CN104102767B - Shield-tunneling construction is to the neighbouring Numerical Analysis methods for underpining Influence of Pile Foundation - Google Patents

Shield-tunneling construction is to the neighbouring Numerical Analysis methods for underpining Influence of Pile Foundation Download PDF

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CN104102767B
CN104102767B CN201410290394.9A CN201410290394A CN104102767B CN 104102767 B CN104102767 B CN 104102767B CN 201410290394 A CN201410290394 A CN 201410290394A CN 104102767 B CN104102767 B CN 104102767B
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pile
pile foundation
tunnel
shield
soil
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CN104102767A (en
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袁鸿
刘熙
杨雄飞
韩军
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Jinan University
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Jinan University
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Abstract

The invention discloses a kind of shield-tunneling construction to the neighbouring Numerical Analysis methods for underpining Influence of Pile Foundation, comprise the following steps：1) according to specific underpinning method scheme, the FEM model of pile foundation underpinning single pile is set up；2) shield tunneling process is simulated, analysis is compared to the situation of change for underpining deformation of pile foundation and internal force before tunnel excavation, in tunnel excavation and after tunnel excavation terminates；3) by changing the parameter of each engineering factor in specific underpinning method scheme, the FEM model set up under multigroup different operating modes, situation of change to underpining deformation of pile foundation and internal force under each operating mode is compared analysis, obtains each engineering factor after tunnel excavation to underpining the influence rule of pile foundation；4) according to specific underpinning method scheme, the FEM model of many of pile foundation underpinning is set up, using the situation of change for underpining deformation of pile foundation and internal force, verifies the feasibility of underpinning method scheme.The inventive method has innovative significance, possesses extensive future in engineering applications.

Description

Shield-tunneling construction is to the neighbouring Numerical Analysis methods for underpining Influence of Pile Foundation
Technical field
The present invention relates to a kind of Numerical Analysis methods, especially a kind of shield-tunneling construction Influence of Pile Foundation is underpined to neighbouring Numerical Analysis methods, belong to shield-tunneling construction to the neighbouring analysis field for underpining Influence of Pile Foundation.
Background technology
As society flourishes with economic, subway has turned into the important vehicles, and subway tunnel is generally used Shield method is excavated, and in construction, influencing each other between shield machine, earth formation and Adjacent Buildings is one sufficiently complex Process, be directed to it is numerous influence construction effects controllable and uncontrollable factor, it is difficult to think prediction.Therefore, it is current Research is inevitably present some shortcomings and deficiency in discussing, the problem being primarily present has：
1) empirical formula method is the analysis and summary to empirical data, but data are limited by concrete engineering particularity, past It is instable toward that can there are problems that, it is difficult to accomplish perfect fitting with certain formula curve.Analytic method it is computationally intensive, and do not have Have the unified approach to be formed suitable for various engineering situation, in practice, limitation is larger, not frequently with.Model test Model test is organized the need for method, engineering is simulated.But it is required to be tested for concrete engineering specific design, with can not Repeatability, the financial resource and material resource of cost are more, can cause larger waste.When being simulated to engineering using numerical analysis method, Equally exist certain difficulty.
2) in numerous researchs to Tunnel Engineering, be directed to ground settlement and stratum deformation problem carries out deep spy more Beg for, the Theory comparison for obtaining is ripe, method is relatively reliable.But for mutual shadow between constructing tunnel and the neighbouring construction of structures of surrounding The research of rule is rung, but simply comes just progressively to carry out in recent years, perfect analysis system is not formed also, influence engineering effort Factor also not yet clearly, and the technical research achievement of outstanding pile foundation underpinning problem is even more phoenix feathers and unicorn horns, therefore this respect Research also has very big development space.
The content of the invention
Defect the invention aims to solve above-mentioned prior art, there is provided one kind can verify specific underpinning method The shield-tunneling construction of concept feasible is to the neighbouring Numerical Analysis methods for underpining Influence of Pile Foundation.
The purpose of the present invention can be reached by adopting the following technical scheme that：
Shield-tunneling construction is comprised the following steps to the neighbouring Numerical Analysis methods for underpining Influence of Pile Foundation：
1) according to specific underpinning method scheme, suitable soil body block size is chosen, determines tunnel-liner, grouting layer and underpin The material and its parameter of pile foundation, and treatment to the lateral stiffness reduction coefficient and grouting layer of tunnel-liner optimizes, and sets up The FEM model of pile foundation underpinning single pile；
2) according to step 1) FEM model set up, mould is carried out to shield tunneling process using Life-and-death element control methods Intend, to pile lateral displacement, pile body vertical displacement, pile body before tunnel excavation, in tunnel excavation and after tunnel excavation terminates Frictional force, the situation of change of pile shaft force are compared analysis, obtain underpining the Changing Pattern of deformation of pile foundation and internal force, are engineering Quality control provides numeric reference foundation；
3) underpin in specific underpinning method scheme the distance between pile foundation, stake end and tunnel horizontal median axis position by changing Put, the parameter of upper load active position and grouting pressure these engineering factors, using step 1) and step 2) method build Found the FEM model under multigroup different operating modes, to pile lateral displacement under each operating mode, pile body vertical displacement, pile body frictional force, The situation of change of pile shaft force and moment of flexure is compared analysis, obtains each engineering factor after tunnel excavation to underpining the shadow of pile foundation Ring action rule；
4) according to specific underpinning method scheme, the FEM model of many of pile foundation underpinning is set up, using underpining deformation of pile foundation With the situation of change of internal force, the feasibility of underpinning method scheme is verified.
As a kind of embodiment, step 2) the use Life-and-death element control methods to shield tunneling process be simulated, It is specific as follows：
A) the soil layer situation according to specific underpinning method scheme sets up soil model, reserves underpinned pile base location, reserved The constraint on horizontal displacement direction is applied to the soil body at position, it is ensured that the soil body will not be clamp-oned；Apply gravity, obtain the soil body in deadweight Under stress and deformation, as initial field stress file derive preserve；
B) set up the soil body and underpin the coefficient model of pile foundation, and read in initial field stress file, applied to underpining pile foundation Power is aggravated, pile top load is applied in former stake position；
C) tunneling part soil body unit is killed, simulation tunnel Stress relieving of surrounding rocks 25%, around tunneling The soil body reversely applies 75% primary stress, while applying 0.15Mpa grouting at the tail of the shield machine pressure；
D) simulated ground stress releases 75%, and 25% primary stress is reversely applied to tunneling surrounding soil, while Apply grouting at the tail of the shield machine pressure；
E) simulated ground stress completely, only applies grouting at the tail of the shield machine pressure to tunneling surrounding soil；
F) cancel grouting pressure, activate liner structure and slip casting layer unit；
Wherein, step a)~b) it is simulation before tunnel excavation；Step c)~e) it is simulation in tunnel excavation；Step f) It is the simulation after tunnel excavation terminates.
Used as a kind of embodiment, the method that the simulation of crustal stress is used in step d) is：Using step excavation pattern, will The soil body unit of tunnel internal is set as " dummy cell " after excavation, calculates the borderline nodal force in tunnel, and these power are anti- Boundary node is acted on, to simulate primary stress, is discharged come simulated ground stress by the size and direction that change active force.
Used as a kind of embodiment, the pile top load that step b) is applied is 250~300t；Step d) and e) applied Grouting at the tail of the shield machine pressure is 0.1~0.2Mpa.
Used as a kind of embodiment, the step a) soil models are D-P constitutive models.
As a kind of embodiment, step 1) soil body block size be 46m × 48m, i.e., take 8D in the direction of the width, In short transverse, corresponding earth's surface is got in shield top, and lower section soil body edge to shield shell outside is not less than 30m.
As a kind of embodiment, step 1) material that uses of the tunnel-liner is C30 concrete placings, thickness is 0.3m, Poisson's ratio is 0.2, and severe is 26KN/m3；The material that the grouting layer is used is soil cement, and thickness is 0.2m, and Poisson's ratio is 0.2, severe is 21KN/m3；The pile foundation that underpins is double stake beam type underpinning structures, and the material that wherein needle beam is used is C40 Concrete placings, length × height=12.55m × 2m, Poisson's ratio is 0.2, and severe is 27.5KN/m3；Underpinned pile is diameter 1.2m, length The drilling concrete-pile of 27m, pile body uses C30 concrete placings, and Poisson's ratio is 0.2, and severe is 26KN/m3。
As a kind of embodiment, step 1) the lateral stiffness reduction coefficient of the tunnel-liner is 0.85
As a kind of embodiment, step 1) treatment of the grouting layer, specially：In shield method tunnel construction process In, after shield tail shell is pushed ahead, the soil body around shield lose before supporting role, internal stress release, while shield Structure machine rearwardly clearance position spray injecting paste material, in the presence of grouting at the tail of the shield machine pressure and inside soil body stress, in shield tail The complicated annular mixed layer of a soil body, injecting paste material and air multiphase coexistence will be formed, this layer of material is simulated using equipollent layer Material, the parameter of the equipollent layer chooses as follows：
Elastic modelling quantity is 1e9；Poisson's ratio is 0.2；Thickness uses formulaChosen, whereinIt is shield tail space Theoretical value, go to 1/2 of difference between shield external diameter and lining cutting external diameter；η is regulation coefficient, and span is 0.7~2.0, soil properties Harder, value is smaller.
Used as a kind of embodiment, the unit that the FEM model is chosen includes PLAN42 units, CONTA172 units With TARGE169 units, wherein：Using the PLAN42 unit simulations soil body, underpin pile foundation and tunnel structure；It is mono- using CONTA172 The soil body, the connection function underpined between pile foundation and tunnel structure are simulated by unit；Using TARGE169 units as object element to tool Body underpinning method scheme is simulated.
The present invention has following beneficial effect relative to prior art：
The inventive method sets up FEM model to shield using the D-P constitutive models of the soil body using large software ANSYS The neighbouring internal force and deformation for underpining pile foundation has carried out the analysis of system in work progress, and shield tail in tunnel excavation is radially noted Starching the applying of pressure, the hardening of grout layer, progressively release etc. details of crustal stress has carried out detailed simulation, also to pile foundation with CONTACT WITH FRICTION between the soil body has carried out rational setting, while the model that can be set up under multigroup different operating modes, further divides Analysis underpins the engineering factors such as stake spacing, stake end position, stake footpath, the grouting pressure between pile foundation in constructing tunnel, to pile foundation internal force And the influence of deformation, and then the feasibility of specific underpinning method scheme is verified, with innovative significance, possess extensive engineer applied Prospect.
Brief description of the drawings
Fig. 1 is the Numerical Analysis methods flow chart of the embodiment of the present invention 1.
Fig. 2 is the FEM model schematic diagram that the embodiment of the present invention 1 is set up.
Fig. 3 a are the Stress Map in Y-direction before the simulation tunnel of the embodiment of the present invention 1 is excavated；Fig. 3 b are the embodiment of the present invention 1 simulation tunnel excavates the Stress Map in preceding soil body Y-direction；Fig. 3 c are to underpin knot before the simulation tunnel of the embodiment of the present invention 1 is excavated Stress Map in structure Y-direction.
Fig. 4 a are the influence figure that the simulation tunnel of the embodiment of the present invention 1 is constructed to pile lateral displacement；Fig. 4 b are real for the present invention Apply influence figure of the simulation tunnel of example 1 construction to pile body vertical displacement；Fig. 4 c are that the simulation tunnel of the embodiment of the present invention 1 is constructed to facing tunnel The influence figure of road side-friction force；Fig. 4 d are that the simulation tunnel of the embodiment of the present invention 1 is constructed to the influence figure for carrying on the back tunnel side-friction force；Figure 4e is the influence figure that the simulation tunnel of the embodiment of the present invention 1 is constructed to axial force of pile.
Fig. 5 a are influence figure of the simulation piles with different interval S of the embodiment of the present invention 1 to pile lateral displacement；Fig. 5 b are the present invention Embodiment 1 simulates influence figure of the piles with different interval S to pile body vertical displacement；Between Fig. 5 c are the simulation piles with different of the embodiment of the present invention 1 Away from S to facing the influence figure of tunnel side-friction force；Fig. 5 d are that the embodiment of the present invention 1 simulates piles with different interval S to the friction of back of the body tunnel side The influence figure of power；Fig. 5 e are influence figure of the simulation piles with different interval S of the embodiment of the present invention 1 to pile shaft force.
Fig. 6 a are influence figure of the simulation piles with different end position of the embodiment of the present invention 1 to pile lateral displacement；Fig. 6 b are this hair Bright embodiment 1 simulates influence figure of the piles with different end position to pile body vertical displacement；Fig. 6 c are that the embodiment of the present invention 1 simulates piles with different End position is to facing the influence figure of tunnel side-friction force；Fig. 6 d are that the embodiment of the present invention 1 simulates piles with different end position to back of the body tunnel side The influence figure of frictional force；Fig. 6 e are influence figure of the simulation piles with different end position of the embodiment of the present invention 1 to pile shaft force.
Fig. 7 a simulate influence figure of the different load positions to pile lateral displacement for the embodiment of the present invention 1；Fig. 7 b are The embodiment of the present invention 1 simulates influence figure of the different load positions to pile body vertical displacement；Fig. 7 c are the mould of the embodiment of the present invention 1 Intend different load positions to facing the influence figure of tunnel side-friction force；Fig. 7 d simulate different loads and make for the embodiment of the present invention 1 With position to carry on the back tunnel side-friction force influence figure；Fig. 7 e simulate different load positions to pile body for the embodiment of the present invention 1 The influence figure of axle power.
Fig. 8 a simulate influence figure of the different grouting pressures to pile lateral displacement for the embodiment of the present invention 1；Fig. 8 b are this hair Bright embodiment 1 simulates influence figure of the different grouting pressures to pile body vertical displacement；Fig. 8 c simulate different notes for the embodiment of the present invention 1 Slurry pressure is to the influence figure to facing tunnel side-friction force；Fig. 8 d simulate different grouting pressures to pile body axle for the embodiment of the present invention 1 The influence figure of power.
Fig. 9 a are that the embodiment of the present invention 1 simulates the pile body horizontal distortion curve map underpined in the case of many；Fig. 9 b are this hair Bright embodiment 1 simulates the pile body Vertical Settlement deformation curve figure underpined in the case of many；Fig. 9 c are that the embodiment of the present invention 1 simulates support That changes in the case of many faces tunnel side-friction force curve map；Fig. 9 d are that the embodiment of the present invention 1 simulates the back of the body underpined in the case of many Tunnel side-friction force curve map；Fig. 9 e are that the embodiment of the present invention 1 simulates the pile shaft force curve map underpined in the case of many.
Specific embodiment
Embodiment 1：
As shown in figure 1, the present embodiment under certain section of left tunnel line on No. six lines of Guangzhou Underground wearing one three across 9 floor framework knot As a example by the engineering of structure, the engineering proposal uses Bored Pile Foundation, and is single-column single pile cap, now using Pile Underpinning Technology pair The impacted pile foundation of structure bottom is underpined, to control influence of the shield tunneling to structure pile foundation.The shield of the present embodiment is applied Work is comprised the following steps to the neighbouring Numerical Analysis methods for underpining Influence of Pile Foundation：
1) according to the engineering proposal of the present embodiment, suitable soil body block size is chosen, determines tunnel-liner, grouting layer and support Change the material and its parameter of pile foundation, and treatment to the lateral stiffness reduction coefficient and grouting layer of tunnel-liner is optimized, profit The FEM model of pile foundation underpinning single pile is set up with large-scale finite element method (fem) analysis software ANSYS；
1.1) suitable soil body block size is chosen
Generally, the excavation in tunnel is only adjusted the distance in the range of the tunnel excavation width (width) of 3-5 times of tunnel center The soil body produce actual influence, STRESS VARIATION at 3 times of width it is general 10% once, the STRESS VARIATION at 5 times of width Scope it is general 3% once；But in view of to eliminate the marginal benefit in FEM calculation, the soil body block of analysis should not be obtained Too small, the size of final decision soil body block is：46m × 48m, i.e., take 8D (8 times of diameter widths), in height side in the direction of the width Upwards, corresponding earth's surface is got in shield top, and lower section soil body edge to shield shell outside is not less than 30m.
1.2) determine tunnel-liner, grouting layer and underpin the material and its parameter of pile foundation
Edpth of tunnel is taken as 25m, and the pile foundation that underpins is double stake beam type underpinning structures, tunnel-liner, grouting layer, underpin it is big Material and its parameter that beam and underpinned pile are used, it is as shown in table 1 below；
Structure Material Size Poisson's ratio v Severe (KN/m3)
Tunnel-liner C30 concretes Thickness：0.3m 0.2 26
Grouting layer Soil cement Thickness：0.2m 0.2 21
Needle beam C40 concretes Length × height=12.55m × 2m 0.2 27.5
Underpinned pile C30 concretes Diameter D=1.2m；Length L=27m； 0.2 26
The tunnel-liner of table 1, grouting layer and underpinned pile sill parameter list
1.3) treatment to the lateral stiffness reduction coefficient and grouting layer of tunnel-liner is optimized
1.3.1) the lateral stiffness reduction coefficient optimization of tunnel-liner
When being simulated to Shield Tunneling, due to having one between practice of construction situation and ideal situation Fixed difference, so parameter is optimized, to closer to actual operating mode；After tunnel lining structure shaping, each tunnel Need to link by cross bolts and longitudinal bolt between road lining segment, form a coefficient entirety, but exactly Due to the presence of these bolts so that the rigidity of whole tunnel lining structure will have more obvious change, so in simulation When need to carry out its rigidity one appropriate reduction, due to using two dimensional model analysis, herein only consider lateral stiffness change Change；When calculating is analyzed to shield tunnel pipe ring, the particularity of pipe ring structure is taken into full account, the pipe ring of shield tail is by many Block pipe sheet assembling is constituted, and is connected by joint between section of jurisdiction and section of jurisdiction, when numerical simulation is carried out, from the usual calculating method of amendment Pipe ring structure is simplified, its basic thought be using pipe ring an as annulus for rigid homogeneous, due to the presence of joint between section of jurisdiction, The bending rigidity of pipe ring changes, it is necessary to be modified to the rigidity of pipe ring with effective rigidity reduction coefficient η after simplification, according to many Individual analysis of project example, takes lateral stiffness reduction coefficient ηIt is horizontal=0.85, comparing can be close to actual condition.
1.3.2) the treatment optimization of grouting layer
During shield method tunnel construction, the space produced when shield tail is come to nothing has great influence to stratum deformation, The FEM Analysis are had great significance by coming to nothing and slip casting situation for accurate simulation shield tail part, shield tail space Actual conditions it is sufficiently complex, after shield tail shell is pushed ahead, the soil body around shield lose before supporting role, it is internal Stress Release, while shield machine rearwardly clearance position spray injecting paste material, in grouting at the tail of the shield machine pressure and inside soil body stress In the presence of, the complicated annular mixed layer of the multiphase coexistences such as the soil body, injecting paste material, an air will be formed in shield tail, but It is during finite element modelling, it would be desirable to which the parameter to this layer of material of COMPLEX MIXED layer does rational simplification, uses Equipollent layer simulates this layer material, and the material composition in equipollent layer is complicated, and ratio row shared by each composition not only with Foundation soil body has pass in itself, also there is close contact with the construction technology of shield tail.Parameter to equipollent layer is chosen specifically such as Under：
Elastic modelling quantity：Equipollent layer is the materials such as the mixture by the soil body, injecting paste material, air and the soil body and injecting paste material Composition.Therefore the elastic modelling quantity of equipollent layer between cement mortar and soil, and should substantially have with the ratio shared by various composition Close, the engineering proposal actual conditions according to the present embodiment, the elastic modelling quantity of equipollent layer is taken as：1e9；
Poisson's ratio：The selection of Poisson's ratio also shows pass with the ratio shared by specific material and material, but because Poisson's ratio takes Less, the influence to result of calculation is limited for value scope, so directly can generally be replaced with the Poisson's ratio of soil cement, It is taken as 0.2；
Thickness：Generally, the thickness of equipollent layer and shield tail space and unequal, its thickness depends primarily on the soil body Property and grouting at the tail of the shield machine pressure；When the soil body is harder, grouting at the tail of the shield machine pressure is big, when soil body autostability is preferable, when shield is de- After sky, surrounding soil only can have less deformation to shield tail space, and the thickness of equipollent layer is smaller than shield tail interstice theory value.But work as When the soil body around shield is relatively soft, when shield tail is come to nothing, injecting paste material will be penetrated into the soil body, form the soil body and slip casting material The mixture of material, the thickness of equipollent layer will be more than theoretical value, and specific thickness is chosen and may be referred to following formula：
Wherein,It is the theoretical value in shield tail space, goes to 1/2 of difference between shield external diameter and lining cutting external diameter；η is adjustment system Number, span is that 0.7~2.0, soil properties are harder, and value is smaller, in the engineering proposal of the present embodiment, the soil that shield passes through Body layer is the micro- weathered zone of rock, and soil property is harder, therefore takes η=0.9, calculates δ=0.2 × 0.9=0.18m, used as shield in analysis The thickness of tail equipollent layer；
1.4) FEM model of pile foundation underpinning single pile is set up using large-scale finite element method (fem) analysis software ANSYS
Using the PLAN42 unit simulations soil body, pile foundation and tunnel structure are underpined, PLANE42 units are that one kind can be used for point Analyse the solid element of two-dimensional structure；PLANE42 units both can be as analysis plane stress or the plane list of plane stress Unit, can be seen as axisymmetric element, and can obtain preferable sunykatuib analysis effect again；
Using the CONTA172 unit simulations soil body, connection function between pile foundation and tunnel structure is underpined, utilizing ANSYS During analytical structure, the treatment of contact surface is a difficulties, and the region of contact surface often has incomprehensiveness, can be with The change of numerous influence factors such as boundary condition, load, material properties and change.And, the contact situation in face with face is Complex, it is related to numerous mechanics problems, with the non-linear of height；CONTA172 units are exactly that one kind can be used to analyze Three node contact units of two-dimentional plane-plane contact, the surface of the 2d solid unit in there is interior joint, the reality covered with it Body unit has same geometrical property.CONTA172 units can be used on two dimension target face (TARGE169 units) and between flexible face Contact and slippage analysis in, if cell surface permeate in specify target face on, then it is assumed that the phenomenon for coming in contact； The x-axis of CONTA172 units is defined along I-J directions, and contact detection is closely related with the order of cell node.The unit Can use and analyze various two-dimensional state of stress, including the situation under plane strain state, plane stress state and axial symmetry, Stress state can automatically carry out detection pairing according to the situation of the following corresponding stress state of covered solid element.
Specific underpinning method scheme is simulated as object element using TARGE169 units, TARGE169 units are used All kinds of two dimension target units acted on osculating element are described, generally, osculating element needs to be covered in deformable body side On solid element in boundary, and effect will be come in contact with target face.Target face carried out in ANSYS discrete, be as one Row TARGE169 object elements, object element can share real constant success and osculating element structure by with corresponding contact unit It is right into contacting.Object element can bear the effect such as power, torque, translation；Target face can carry out mould with one group of object element Intend, multigroup different object element is combined and can obtain different target face.Rigid body or beformable body can serve as Target face, unlike, just-soft contact mode in, always by target face selection be rigid body, and simulate soft-soft contact when Wait, it is necessary to using the analog form on contact cover wherein a beformable body surface；
The unit chosen according to more than, the FEM model of foundation is as shown in Figure 2.
2) according to step 1) FEM model set up, mould is carried out to shield tunneling process using Life-and-death element control methods Intend, to pile lateral displacement, pile body vertical displacement, pile body before tunnel excavation, in tunnel excavation and after tunnel excavation terminates Frictional force, the situation of change of pile shaft force are compared analysis, obtain underpining the Changing Pattern of deformation of pile foundation and internal force, are engineering Quality control provides numeric reference foundation；
2.1) shield tunneling process is simulated
2.1.1) determine the load of FEM model, according to the process that tunneling shield is constructed, be mainly concerned with following several Load：
Deadweight：The soil body, pile body and tunnel structure are at affected by gravity in gravitational field.Especially for the soil body Material, due to its material characteristic such as compressibility is big, consolidation time is long in itself, the soil body will occur larger change under weight stress Shape.And pile body and tunnel structure are due to excavating the deformation that influence is produced, occurred after the soil body is by deadweight settlement stability, therefore Need to subtract this soil body partial dislocation.In simulations, using import initial field stress file method come eliminate the soil body due to The Influence of Displacement that deadweight is produced.
Pile top load：In scheme is underpined, underpining pile foundation needs to replace former pile foundation to undertake the lotus that top pillar is transmitted Carry, but underpined due to using double stake beam types in this model, the load that top pillar is transmitted is not loaded directly into support The top of pile foundation is changed, but is carried in former stake position, the i.e. top of transform beams, load is：P=270t.
Grouting pressure：During shield method tunnel construction, when shield tail disengages the soil body, can be noted using synchronous in shield tail Slurry mode, among the space that injecting paste material is filled between lining cutting and the soil body.In order to reach uniform full filling effect, need To apply grouting pressure in shield tail.In this model, its value is taken as 0.15Mpa.
Surrouding rock stress：Ground is to accumulate the moon by day by a series of operation of nature such as sedimentation, accumulation, weathering in native state Tired formation, presence of the inside with primary stress；Usually, before excavation construction, the soil body of every bit on tunnel border All in the presence of primary stress, in a kind of poised state of stabilization；When excavating, the rock mass of tunnel segment is hollowed out, its The stress and constraints on border all changes, internal primary stress release, and stress field and displacement field all occur great Change, stress redistribution, is finally reached new balance.
2.1.2) the soil layer situation of the engineering proposal according to the present embodiment sets up soil model, the engineering proposal of the present embodiment Soil layer situation the soil body can be divided into following five layers：A, artificial earth fill；B, Muddy Bottoms silty clay soil；C, sand；D, rock high wind Change band；The micro- weathered zone of e, rock, the soil model is D-P (Drucker-prager) constitutive model, reserves underpin in a model Pile foundation position, to the constraint on soil body applying horizontal displacement direction at reserved location, it is ensured that the soil body will not be clamp-oned；Apply weight Power, obtains stress and deformation of the soil body under deadweight, is derived as initial field stress file and preserved；
2.1.3 the soil body, needle beam and the coefficient model of underpinned pile) are set up, and reads in initial field stress file, it is right Underpin pile foundation and apply gravity, the pile top load of 270t is applied in former stake position；
By step 2.1.2)~2.1.3) Stress Map of Y-direction that has obtained is as shown in Figure 3 a；For the ease of analysis, point The Y-direction stress situation of stake and soil is not extracted, the Stress Map for obtaining is as shown in Fig. 3 b and Fig. 3 c；
From Fig. 3 b and Fig. 3 c, before excavation, in the presence of weight stress, resistance to shear of soil is substantially with soil depth Increase and become big, but near the position of pile body, moved down because underpinned pile is oriented relative to the soil body under load action under post Dynamic trend, native land body provides upward frictional force to stake；On the contrary, stake just has downward rubbing action to the soil body.So For the soil body of same depth, the stress suffered by the soil body near stake week will be greater than the stress away from the underpinned pile soil body, Situation about being swelled upwards in the big stressor layers in stake side is then presented as on Stress Map.Simultaneously in pile foundation underpinning structure, underpin big Beam is different from the girder construction in superstructure, and needle beam is supported on soil layer, when it is acted on by upper post bottom load, Fractional load can be transmitted to beam substratum, cause beam subsoil ply stress to be more than the soil layer stress underpined beyond pile foundation；For support Structure is changed, on the top of transform beams, due to being acted on by load under post, corresponding position occurs in that obvious stress increases Greatly.In scheme is underpined, underpinned pile stretches into needle beam certain length, and its deformation receives the constraint of beam, therefore in model simplification When the connection of the two is considered as it is affixed.Therefore, when load produces curvature effect to underpinning structure under post, transform beams occur downward Flexure, there are the malformations of " evagination " shape in two underpinned piles.For underpinned pile pile body, because the side of surrounding soil is rubbed The Overlay of power is wiped, the stress in the Y-direction of pile body inside is gradually reduced along pile body buried depth；Analyzed more than, it is known that more than Analog result rationally, can meet basic principles of soil mechanics, can carry out the excavation of next step；
2.1.4 tunneling part soil body unit) is killed, simulation tunnel Stress relieving of surrounding rocks 25%, to tunneling Surrounding soil reversely applies 75% primary stress, while applying 0.15Mpa grouting at the tail of the shield machine pressure；
2.1.5) simulated ground stress releases 75%, and 25% primary stress is reversely applied to tunneling surrounding soil, Apply 0.15Mpa grouting at the tail of the shield machine pressure simultaneously；What crustal stress discharged simulates the method for using is：Using step excavation pattern, will The soil body unit of tunnel internal is set as " dummy cell " after excavation, calculates the borderline nodal force in tunnel, and these power are anti- Boundary node is acted on, to simulate primary stress, is discharged come simulated ground stress by the size and direction that change active force；
2.1.6) simulated ground stress completely, only applies 0.15Mpa grouting at the tail of the shield machine pressure to tunneling surrounding soil；
2.1.7) cancel grouting pressure, activate liner structure and slip casting layer unit；
2.2) to tunnel excavation before (i.e. above-mentioned steps 2.1.4 in (i.e. above-mentioned steps 2.1.3 complete after), tunnel excavation ~2.1.6) and the pile lateral displacement Ux of (i.e. above-mentioned steps 2.1.7 complete after), pile body are vertical after tunnel excavation terminates Displacement Uy, pile body frictional force, the situation of change of pile shaft force are compared analysis
2.2.1) the analysis of underpinned pile pile body deformation
Double stake beam type underpinning structures are used in this model, but in analysis, in order to more simply react stake The stress and deformation of base, now underpin pile foundation and discuss, because model uses symmetrical structure, mould mainly for left side Load in type is also symmetrical applying, and the stress and deformation that underpin pile foundation for obtaining are also with symmetry, therefore the left side for obtaining Side underpin pile foundation conclusion can be similarly adapted to right side underpin pile foundation.
2.2.1.1) Analysis of Lateral Displacement
Due to being reference axis origin with tunnel center in modeling, it is positive direction to take its right and top, so by Fig. 4 a Understand：
A, tunneling shield method excavation before, it is not the substantially vertical insertion soil body to underpin pile foundation, but existed compared with Small inclination and flexure.At the affixed position of needle beam and pile foundation, the horizontal displacement for tending to centric load direction is occurred in that. And on the contrary, occurring in that larger negative displacement on the top (buried depth is about in the range of 2-9m) of pile body, maximum negative displacement is 2.62mm.Because symmetrical configuration load is symmetrical, therefore from double deformation forms, pile body top is mainly showed " outside drum type It is convex " variation tendency, the deformation of pile body lower end is then relatively small.This is because, work as being applied with upper load on needle beam After, there is downward deflection deformation in needle beam, because being connected using consolidation style between beam stake, so that with needle beam two ends Warpage, pile foundation tip position can also produce inside corner and bending, result in connecting portion to centric load direction indent, The displacement in positive direction is shown as in horizontal direction, pile body deviates from centric load direction evagination, shows as deviating from horizontal direction Move in centric load direction.This " drum type evagination " trend is gradually reduced along pile body, until pile body bottom just occur again compared with Small negative displacement, stake bottom horizontal displacement Ux is -0.71m, and 73% is about reduced compared with maximum.Because pile-end soil layer is springform , there is very strong restriction ability the larger micro- weathered rock formation of amount to the deformation of pile body.
B, when tunnel is excavated, the horizontal displacement Ux changes for underpining pile body top are little, keep substantially " outside drum type It is convex " deformation, but after tunnel excavation, the soil body of tunnel site is hollowed out, for being supported on underpining for soil body top For crossbeam, lower support power reduces, and causes the downward deflection deformation of beam body to increase, and then cause the pile body top affixed with it The deformation that curves inwardly becomes apparent, and horizontal displacement value Ux has increased.There is significance difference with the horizontal distortion situation for excavating preceding pile body Different, after tunnel excavation, the horizontal displacement of below pile body 19m parts has obvious increase before relatively excavating.Especially to stake End position, horizontal displacement is changed into -2.42mm from original -0.71mm, about increases 243%.Because in the simulation of second stage In, it is believed that tunnel soil body elastic modelling quantity progressively reduction, inside soil body stress progressively discharges, and tunnel surrounding soil occurs away from tunnel The horizontal distortion of hole, and this deformation tendency outwards progressively expanded with justifying petal-shaped in tunnel both sides.Meanwhile, in second-order Section, along the radial grouting pressure for applying 0.15Mpa around tunnel.In the presence of grouting pressure, tunnel surrounding soil it is additional Pressure increases.Pile body is underpined exactly under this soil deformation pressure and joint effect both grouting pressure, occurs to deviate from tunnel The displacement in direction.
C, at the end of tunnel excavation, the drift displacement curve along pile body occur " bow " font change.Top misalignment base This holding is constant, simply pile body stage casing maximum forward horizontal displacement increase.In below pile body 19m to stake end position, horizontal displacement Change is obvious, and the maximum horizontal displacement of whole pile body appears in tunnel horizontal axis correspondence position, about 3.8mm, than excavating Before increase 44.9%.After constructing tunnel terminates, grouting pressure cancel, tunnel lining structure shaping, tunnel surrounding should Power progressively discharges and finishes, and soil body internal stress tends towards stability after redistribution.Due to the pile peripheral earth in the range of the 9m-18m of stake middle part Tunnel upper is sitting at, it is big to face tunnel side resistance to shear of soil release rate, causes pile body or so unblanced earth pressure, pile body to occur positive Movement.And near tunnel horizontal axis correspondence position, liner structure is in the deadweight of the top soil body and the work of bottom soil body resilience Under, occurring " " formula deforms horizontal ovum, and extruding is produced to tunnel soil at both sides, and then it is larger to cause pile foundation also to occur in the position Displacement in negative direction.But still due to the limitation of the hard soil layer in stake bottom, below tunnel axis, the horizontal displacement edge of pile body Depth direction is gradually reduced, and the horizontal displacement of stake end is only 2.7mm.
2.2.1.2) vertical displacement analysis
A, as shown in Figure 4 b, before tunnel excavation, vertical displacement curve occurs one in part (at stake top 0m-3m positions) Individual difference step, is just uniformly reduced thereafter with lower from 3m along depth direction.Under upper load effect, transform beams are by fractional load It is delivered in lower overburden layer, soil body compression is larger, and transform beams accordingly sink.It is connected with needle beam at stake top, it is erected Straight displacement is larger by the vertical deformation effect of needle beam, therefore vertical displacement maximum appears in stake top position, is about 5.8mm.After the soil layer that crouched under needle beam has shared fractional load, remaining load is delivered to and underpins stake top, and pile body is in deadweight Under the collective effect of load, pile body is pressurized, and pile body is deformed due to material compression.And with the increase of depth, soil is to support Change the rubbing action of pile body substantially, pile body vertical displacement is gradually reduced, and stake bottom vertical displacement is only 4.62mm, and about stake top is vertical The 79.7% of displacement.
B, when tunnel excavation, the vertical displacement situation on pile body top is roughly the same with when not excavating, be simply due to Excavation effect, the resilience of the soil body of tunnel bottom, the trend for having upward pushing tow to pile foundation, before making an end vertical displacement by excavating It is 4.55mm that 4.62mm becomes current.
C, after tunnel excavation terminates, its vertical deformation Uy is gradually reduced along pile body buried depth.While relative tunnel excavation Before for, its correspondence each point value be also obviously reduced, but reduce ratio arrange and differ, the reduction of pile body bottom reaches than row 8%, and the reduction ratio of stake top is less than 4%.This is that resistance to shear of soil redistribution terminates, stake end after stablizing due to tunnel excavation The springback capacity of the soil body has reached maximum.The deformation of liner structure simultaneously is increased, and pile body flexural deformation becomes apparent from, and causes Uy directions On vertical displacement reduce.
2.2.2) the analysis of pile body frictional force
Pile foundation undertakes after upper load, it is necessary to its own holds by pile side friction and end resistance competence exertion Load is acted on, therefore analyzes the change in friction force rule of pile foundation, to further appreciating that it is very great that the stressing conditions inside pile foundation have Meaning, frictional force suffered by pile body and the property of pile peripheral earth and the relative shift between the two are relevant, however, pile body faces tunnel The situation of road Ce Hebei tunnels side but and is differed, therefore is separately discussed herein.
2.2.2.1 tunnel side-friction force) is faced
As illustrated in fig. 4 c, in the pile foundation for facing tunnel side, frictional force is occurred in that just negative situation.And for excavating Different phase, the Changing Pattern of frictional force is also different：
A, before tunnel excavation, pile foundation occurs in that the larger force of negative friction at 4m-18m.Maximum Negative Frictional Force is about sent out It is 33.08KN at raw 10m；In below 18m, the soil body for just, and substantially increases, frictional force the frictional force of pile foundation with buried depth Value constantly increase, reaches due to " soil arch " effect after maximum 71.486KN, and pile-soil relative displacement reduces, stake end frictional resistance hair Wave, frictional force in side-pile is not further added by, stake bottom side-friction force is only 22.691KN.Frictional force and pile peripheral earth suffered by pile body Property, pile body buried depth and stake soil the factor such as relative displacement it is relevant.There is the position of the force of negative friction facing tunnel side in pile body It is in pile body top.Its side soil body bears the load action that top needle beam transmission comes, and compression occurs, with respect to pile body Downward displacement is produced, native land body applies the downward force of negative friction to stake.And in pile body bottom, pile body is made by pile top load With, there is downward relative displacement relative to Pile side soil body, therefore frictional force is just.
B, when tunnel excavation, the situation of the force of negative friction with for excavate when it is basically identical.But it is special in positive friction region It is not to correspond to tunnel horizontal median axis above 6m to the pile body region at tunnel center, frictional force is significantly increased, and maximum amount of increase goes out At present 21.2m, 146.7% has been reached.And below tunnel horizontal median axis, frictional force reduces before relatively excavating, by original 71.486KN is changed into 47.747KN.This phenomenon is mainly by tunnel excavation, along applying radial grouting pressure around tunnel Cause, for tunnel horizontal median axis area above, when applying grouting pressure, upward additional stress point is produced to the soil body Amount, increases the relative displacement between pile body, and frictional force is increased.Similarly, be the soil body below horizontal median axis, be subject to be to Under Additional stress component, counteract part stake soil between relative displacement, frictional force reduce.However, used in this programme Pile body buried depth is deeper, and pile body is more long, and the influence area of grouting pressure is limited, therefore the change in friction force above pile body is little.
C, after tunnel excavation, the tunnel segment soil body hollows out, and frictional force is changed significantly.Tunnel upper soil body off-load, leads The sleeping soil body is moved further downward relative to pile foundation under causing needle beam, so producing the region increase of negative friction, positive negative friction The position of the neutral point between power drops to 19.5m by initial 18.3m, and the value of maximum negative friction increases 10.06%, is changed into 36.408KN.Meanwhile, in pile body bottom, its side inside soil body stress discharges on the liner structure for being formed completely, lining cutting knot There is the deformation of " horizontal ovum " formula, the transverse shear stress soil body, and then influence in the presence of the deadweight of the top soil body and bottom soil body resilience in structure Close on the flexural deformation for underpining pile foundation generation away from tunnel.The soil body is boundary with tunnel horizontal axis simultaneously, and the top soil body is upward Mobile, the bottom soil body is moved down, and is caused and is increased in horizontal median axis above pile-soil relative displacement, and relative below axis Displacement reduces.About there is first horizontal median axis correspondence displacement in maximum, reaches 99.467KN.
2.2.2.2 tunnel side-friction force) is carried on the back
As shown in figure 4d, Shield Tunneling is smaller for the influence of the frictional force suffered by back of the body tunnel side pile foundation.Opening Before digging, pile body is subject to upward frictional force.And the trend constantly increased along pile body buried depth, frictional force is showed on the whole. Underpin pile foundation has downward mobile trend under pile top load effect relative to the back of the body tunnel side soil body, and maximal friction is 90.926KN.But after tunnel excavation terminates, because tunnel top (17m-23.6m) resistance to shear of soil discharges completely, tunnel bottom Under the joint effect of the factor such as soil body resilience and tunnel lining structure transversely deforming, tunnel side soil pressure is faced in the both sides for underpining pile foundation Power reduces, and tunnel surrounding soil release rate is maximum, and is radially gradually reduced.The back of the body tunnel side soil body is then with the horizontal axis in tunnel Line is boundary, and the top soil body has downward change in displacement, and the motion of the bottom soil body is then conversely, event rubs in the range of 17m-23.6m Wipe power to reduce, maximum reduces 32%, only 38.2KN；Due to being influenceed by excavation, in tunnel, horizontal median axis correspondence position is attached The near force of negative friction is significantly increased, and at 2.2m below tunnel horizontal median axis, its value is frictional force maximum 101.43KN。
2.2.3) the analysis of Internal forces
2.2.3.1) pile shaft force
Structure based on pile body, mainly undertakes the load that superstructure is transmitted, and deliver load to the lower hard soil that crouches Layer.Pile foundation mainly has two kinds with the mode of action of soil layer, and a kind of is, by the rubbing action of stake surrounding soil, fractional load to be passed It is delivered in ground；Another way is directly supported on soil layer by by stake end, delivers load to the soil body.So, dividing When analysis underpins the axle power of pile foundation, it is necessary to consider with reference to the variation tendency of frictional force, accurately result can be just obtained rationally.
As shown in fig 4e, before tunnel excavation, the axle power of underpinned pile is generally along pile body in gradually less trend. Stake top, the axle power born is 965KN.The theoretical value of load is much smaller under post of the value than 1/2, load only under post 71.48%.When being underpined using double stake beam types, underground pile one underpins girder construction has very big difference with the ground girder construction of upper prop one Not.Transform beams are embedded at the position of underground 3.2m.When by upper prop bottom load action, transform beams by upper load share to While pile foundation, part upper load will necessarily also be passed to the lower sleeping soil layer of transform beams, cause the load for assigning to stake top remote Not as good as the 1/2 of post bottom load.In more than pile body 6m, the change curve of axle power is gentle, but still present with depth increase gradually The trend of reduction, when depth declines 6m, axle power only reduces 8%.At 6m-11m positions, due to larger by facing tunnel side The force of negative friction is acted on, and is generally represented as pile shaft force and is become big.Due to the increasing of pile body buried depth, facing the tunnel side force of negative friction It is gradually reduced, eventually becomes positive friction, therefore shown as on pile shaft force after pile body depth reaches 11m, axle power significantly subtracts Small, pile body buried depth increases 16m, and pile shaft force reduces 88.53%.In tunnel excavation and after the completion of tunnel excavation, axle power Substantially variation tendency is generally consistent with before excavation.But after excavation, pile body faces the neutral point of the positive force of negative friction in tunnel side Move down, the effect of the force of negative friction becomes apparent from.Although axle power still has reduction by a small margin in 0m-6m, in the axle of below 6m Power growth region is elongated, and 6m-13m is changed into from the scope of original 6m-11m.And in the region, axle power is increased 79.835KN.Facing below tunnel side 19.5m, because the positive friction that excavation causes is dramatically increased, therefore in the following tunnel in the position Road axle power reduces rapidly, and pile body buried depth only increases 9m, and pile shaft force is reduced by about 54%.
3) by above-mentioned numerical simulation analysis, the digging process in adjacent stake tunnel can be rationally and effectively simulated, and is known Tunnel excavation will produce the influence that can not ignore to the internal force and deformation that underpin pile foundation, but want this shadow of labor Ring effect size, it is necessary to pass through change specific underpinning method scheme in underpin the distance between pile foundation S, stake end and tunnel level The parameter of axis line position (i.e. stake end relative position), stake footpath size and grouting pressure these engineering factors, using step 1) With step 2) the FEM model set up under multigroup different operating modes of method, it is perpendicular to pile lateral displacement Ux, pile body under each operating mode The situation of change of straight displacement Uy, pile body frictional force, pile shaft force N and moment M is compared analysis, obtains each engineering factor in tunnel Road excavate after to underpining the influence rule of pile foundation；
3.1) influence of underpinned pile stake interval S
The stake spacing of underpinned pile refers to the distance between axis of underpinned pile, is one of important duty parameter, for three Operating mode under group piles with different interval S, analysis is made with regard to pile foundation internal modification and stressing conditions：
As shown in Figure 5 a, no matter how stake spacing changes, and the change of " bow " font is occurred in that in the horizontal displacement Ux of pile body Change situation, i.e. negative displacement increase twice, a negative displacement reduce the form of (or even displacement is reversely changed into positive displacement), maximum displacement Value is both present in tunnel horizontal median axis position；When stake spacing increases, pile body upper deformation amplitude increase, curve otherness is bright It is aobvious.Pile body lower deformation amplitude reduces, and Ux curves almost overlap；When stake spacing is changed into 12m and 14m from 9.6m, stake top position is just Increase and increase with pilespacing to moving, 0.52mm and 0.74mm is increased respectively.It can be seen that S increases, transform beams are lengthened, and are had on more Under being delivered in sleeping soil layer, the deflection deformation of needle beam aggravates portion's load, and because stake top position is connected with needle beam, Therefore the corresponding stake top for underpining pile foundation deformation is also increased.Meanwhile, during the increase of S, the maximum negative displacement value increase of pile body epimere, The maximum negative displacement value of pile body hypomere reduces, and the maximum hogging moment of pile body epimere has increased 37.2% and 46.7%, has been changed into respectively 3.60mm and 3.85mm, and the maximum negative displacement of pile body hypomere reduces 5.3% and 7.9% respectively, be changed into 3.62mm and 3.52mm.In the range of the about 5m-14m of pile body stage casing, negative horizontal displacement Ux is substantially reduced, and pilespacing S is bigger, the reduction of negative displacement Amount is smaller.In S=9.6m and S=12m, the maximum reduction amount of negative displacement is respectively 3.91mm and 3.68mm, negative more than maximum Shift value, then occurs in that positive displacement underpining pile foundation middle section position.And as S=14m, the maximum reduction amount of negative displacement is only There is not positive displacement, the increase principle of pile body epimere negative displacement and the increase principle phase of displacement at pile top in 3.43mm, pile foundation stage casing Together, caused by pile body occurs in that the bigger flexure for concaving towards needle beam direction.And due to pile foundation from tunnel more away from, what is be subject to opens Dig influence also just smaller, therefore when s increases, the horizontal displacement Ux of stake bottom is gradually reduced.
As shown in Figure 5 b, for vertical displacement Uy, in same buried depth position, when S becomes from 9.6m turns to 12m, underpinned pile Stake spacing it is bigger, vertical displacement value is bigger.Maximum horizontal displacement Ux occurs at the 6.69 of stake top position, about S=9.6m The 119.9% of acquired maximum.And when s progressively increases to 14m, same buried depth position vertical displacement Uy slightly has reduction, But less, situation when maximum is only compared with S=12m reduces 4% to variable quantity；Stake interval S is bigger, and underpinned pile flexural deformation is got over Greatly, it will cause the vertical displacement to have the trend of increase.However, S is bigger, described by the normal distribution curve in Peek formula Situation, the deformation of the distal end soil body is smaller, and pile body is influenceed also smaller by tunnel excavation, has reduction to become vertical displacement Gesture.So, two kinds of summary influence, vertical displacement is totally being showed with the increase first increases and then decreases between stake apart from S Situation of change.
As shown in Figure 5 c, under the operating mode of different interval Ss, pile body occurs in that frictional force has and just has negative situation, rubs The maximum for wiping power is both present in tunnel horizontal median axis correspondence position.In the same buried depth position of pile body, frictional force during S=9.6m Value is noticeably greater than the situation of S=12m and S=14m, and now maximal friction is positive friction, about 99.467KN, the force of negative friction Pile body top 19m above position is appeared in, maximum is 36.4KN.And as S=12m and S=14m, the friction force value of the two And variation tendency is closer to.Positive friction maximum is 25.9KN and 22.2KN, and maximum when respectively compared with S=9.6m reduces 73.9% and 77.6%.Meanwhile, being moved at 16m on the neutral point position of the positive force of negative friction, Maximum Negative Frictional Force is respectively 18.552KN and 20.615KN.The reduction of the force of negative friction is relevant with the relative displacement reduction for facing the tunnel side soil body.When S increases, The soil body volume that upper load is undertaken under needle beam also accordingly increases, under the effect of identical upper load, the deformation of the soil body Reduce, pile-soil relative displacement reduces.
As fig 5d, it may be clearly seen that, the situation of change of frictional force is substantially different from other two kinds during S=9.6m Situation；During S=9.6m, back of the body tunnel side-friction force is significantly increased near tunnel horizontal median axis correspondence position, maximum hair The raw 2m positions below horizontal axis, have reached 101.43KN.When S is bigger, the frictional force for carrying on the back tunnel side is obviously reduced.And work as S increases when to a certain extent, and the frictional force for carrying on the back tunnel side is essentially identical.In the case of S=12m and S=14m, maximum is about Occur at pile body 11m-12m sections, maximal friction respectively compared with S=9.6m in the case of reduce 61.4% and 64.6%.
As depicted in fig. 5e, for the situation of change of pile shaft force, with the increase of stake interval S, the soil body is shared under transform beams Load combination ratio increase, stake top axle power reduce, therefore show as stake top axle power difference it is larger, but every underpin pile foundation axle power change Trend is roughly the same, and substantially axle power reduces along pile body.However, the excursion of each stake is different, and during S=9.6m, stake Body minimum axle power is the 38% of maximum axle power, and during S=12m and S=14m, it is maximum axle power that pile body minimum axle power is only 35.5% and 26.1%.It can be seen that the variation tendency of axle power, is changed on the basis of frictional force in side-pile, closer to excavation tunnel Road, the amplitude of variation of axle power is bigger, and it is obvious that axle power reduces situation；For underpining pile foundation, in top 6m-13m positions due to negative The effect of frictional force, axle power has different degrees of increase tendency in this position, and when S is smaller, the effect of the force of negative friction becomes apparent from, The amplification of axle power is bigger, or even in the case of S=9.6m, underpins the position of pile body middle part 11m-13m, and pile shaft force exceedes Stake top axle power, and for same pile body buried depth position, pile shaft force increases with S and progressively reduces.S is changed into 12m and 14m from 9.6m When, the maximum of pile shaft force becomes for 806.1KN and 603.8KN from 993.8KN, and 18.9% and 39.2% is reduced respectively.
3.2) influence of stake end relative position
As shown in Figure 6 a, for different pile foundation length, the change of horizontal displacement is more apparent；As L=20m, most flood It is negative displacement that prosposition is moved, and is 2.70mm at pile body 4m.When underpinned pile foundation pile end is located at tunnel horizontal median axis correspondence position When putting, influenceed most obvious by tunnel excavation, situation of change and the other two situation of its horizontal displacement have marked difference.Stake The horizontal displacement on base top is obviously reduced, the horizontal negative displacement increase of bottom, has reached 2.62mm, and 2.49mm occur in stake end Positive displacement.When stake end is located at below horizontal median axis, its maximum horizontal displacement appears in axis correspondence displacement, reaches 3.81mm, situation when maximum displacement is compared with L=20m and L=25m increases 45.4% and 41.8% respectively.
As shown in Figure 6 b, vertical displacement generally reduces with the lengthening of pile body；When pile body length is located at tunnel upper When, vertical displacement is very big, about pile body L=25m situations when maximum vertical displacement Uy 116.6%, about axis lower section situation When maximum vertical displacement Uy 138.7%, pile body is shorter, and stake end is supported in the larger soil layer of tunnel upper stress release rate, So the Influence of Displacement being subject to is big, and tunnel side and lower section soil layer stress release rate are smaller, and the influence to deformation of pile foundation is smaller.
As fig. 6 c, face tunnel side-friction force and positive and negative alternate situation occur, during L=20m, the position position of neutral point At 12.2m, at 61% length of pile body.It is 25m and 28m as L increases, the position of neutral point have dropped respectively 4.4m and 7.1m, is each mutually located at the 66% and 69% of pile body length.It can be seen that, with the increase of pile foundation length, in pile foundation in Property point position will move down along pile body.When stake end is located at tunnel excavation cavern top, maximum appears in an end position, maximum The force of negative friction is 28.3KN, and maximum positive friction is 46.8KN.And work as stake end positioned at tunnel horizontal median axis position and its following When, 17.4% and 28.7% is increased when Maximum Negative Frictional Force is than L=20m respectively.The maximum of positive friction is then both present in Tunnel horizontal median axis correspondence position, and with pile foundation length increase, positive friction maximum increase, respectively 99.225KN and 99.467KN。
As shown in fig 6d, for away from tunnel side, showing frictional force per pile base and becoming along the change that pile body increases Gesture.And underpin receiving for pile foundation frictional force in more than 20m correspondence positions under suffered two kinds of operating modes of frictional force and other during L=20m Power situation is essentially identical, and only at respective newly-increased stake position long, frictional force further increases.This explanation stake change long is carried on the back to pile foundation The Changing Pattern influence of the frictional force suffered by tunnel side is little.Simply as L=20m, maximal friction occurs in stake end position, Its value is 55.5Kn, and with the increase of L, maximum positive friction appears in tunnel horizontal median axis correspondence position, compared with L=20m When maximum increase 8% and 82.6% respectively.
As shown in fig 6e, by can be seen that the top of pile foundation, the value of axle power and change in the case of three groups of pile foundation length Trend is essentially identical, but the bottom of pile foundation, in same buried depth position, pile shaft force of the stake pile foundation long at the position It is bigger, and as buried depth is increased, the difference of axle power is bigger, is 92.11KN in the axle power difference of stake top, and arrived stake end 20m Depth, difference is changed into 503.89KN.And stake is long, the side-friction force suffered by pile body is bigger, to the reduction effect of pile shaft force Fruit is more obvious, and during L=20m, axle power reduces 587.5KN along stake, and as L=25m and 28m, axle power is reduced along stake 700.9KN and 616.7KN.
3.3) influence of upper load active position
When upper load is underpined using underpinning structure, a underpinning structure often occurs while underpining several originals The situation of pile foundation.After the former stake of diverse location is underpined, upper load is still acted on needle beam in the original location.It is different Load position, additional bending moment, stake top axle power etc. to underpining pile foundation generation can all be produced and had a significant impact, and then be embodied In the deformation of pile foundation and the change of internal force.Therefore, upper load active position is studied to underpining the influence of pile foundation, with very Great practical significance.
The suffered influence under the effect of diverse location upper load of pile foundation is underpined in order to specifically reflect, top has been taken respectively Load action at needle beam left end 1/3L, centre position and at needle beam right-hand member 1/3 these three situations are said Bright analysis.Compare by three cases above：
As shown in Figure 7a, when upper load gradually moves to right-hand member by left end, the drift displacement curve of pile body is by approximate straight Vertical bow font is changed into the bow font being tilted to the right, and the integral inclined degree of pile body is increased.The change of displacement at pile top is maximum, increases to the right Big 3.94mm.Maximum displacement in the range of pile body epimere 0m-10m reduces, and is acted on away from the position of needle beam left end 1/3 by F When 3.30mm, be reduced to 0.99mm, about reduce 69.8%.Maximum forward displacement in the middle part of pile body also with F away from And reduce, 0.85mm is reduced to by 1.45mm.And underpining below pile foundation buried depth 20m, maximum horizontal negative displacement is but remote with F From and increase, the maximum displacement value of pile body increases 37.5%, has reached 4.51mm.Because when upper load F is gradually right During shifting, eccentric throw increase, additional bending moment increase, meanwhile, transform beams there occurs bigger buckling deformation in remote load end pile foundation, most Cause eventually and finally occur in that overall situation about being tilted to the right, top deforms to the right aggravation, and pile body bottom is away from primitive axis line position.
As shown in Figure 7b, then it will be clear that load is away from the displacement more of pile foundation, pile foundation is smaller by being influenceed, Vertical displacement value is also smaller.When top imposed load is gradually moved to right, 6.39mm difference when maximum vertical load is by high order end 12.7% and 24.6% is reduced, is changed into 5.58mm and 4.82mm.
As shown in figs. 7 c and 7d, when top imposed load is gradually moved to right, it can be seen that face tunnel side in the case of three kinds Frictional force variation tendency it is essentially identical, maximal friction is appeared near tunnel horizontal median axis.But with load Move to right, pile body top is increased by the region of negative friction, and Maximum Negative Frictional Force increases 99.4%, reaches 45.4KN.And stake The positive friction of body bottom is but gradually reduced with moving to right for load, full the maximal friction of stake is reduced to by 112.5KN 81.9KN.Because for different load positions, both sides underpin the pile top load obtained by pile foundation distribution and differ. When upper load is gradually moved to right, the pile top load of left stake is gradually reduced, and move downward trend of the pile body under load action subtracts It is small, the relative displacement increase between stake soil, therefore the force of negative friction on top increases.And now after excavation terminates, the tunnel such as lining cutting In the presence of the factors such as the top soil body, post bottom load, the deformation of generation is no longer symmetrical to structure, and under nearly post load position The deformation increase put, remote loading position deformation reduces, and causes the soil deformation on the right side of left tunnel not reciprocity.Therefore when load is moved to right When, the deformation of the Pile side soil body of left side pile foundation reduces, and pile body maximal friction is reduced to 81.9KN, about reduces by 112.5KN 27.2%, and the pile body frictional force of tunnel side is carried on the back, being influenceed smaller by load position, its value is kept essentially constant.
As shown in figure 7e, for pile shaft force, can be clear that, with moving to right for load position, for Same buried depth position, pile shaft force is gradually reduced.And when F acts on left end, axle power reduces 81.7% along pile body, and axle power becomes Change curve to incline.And when load position is gradually distance from, axle power changes small along pile body, axle power change curve gradually tends to perpendicular Directly, the difference of pile shaft force is less than 48.4%.
3.4) influence of grouting pressure
In Shield Tunneling, when shield machine is pushed ahead, excavate between border and liner structure, it is necessary to by Apply grouting pressure, cement mortar is injected among space.But meanwhile, grouting pressure can be also acted on the soil body around tunnel, Apply additonal pressure to the soil body, and then influence to underpin the deformation of pile foundation.
As figures 8 a and 8 b show, analysis understands, the situation of grouting pressure is not applied and applies 0.15Mpa grouting pressures Situation is compared, and horizontal distortion Ux is essentially identical in the variation tendency of more than pile foundation 15m.But in below 15m, pile body has negative direction to move Dynamic trend, and with the increasing of pile body buried depth, the horizontal displacement difference of the two also becomes larger.In 15m, the water of the two Prosposition puts difference for 0.29mm, and the difference of the horizontal displacement Ux at both stake ends has reached 1.02mm.In analysis before, Main influence area is tunnel both sides " circle petal " part during tunnel excavation.Even if therefore not applying grouting pressure, pile body Can still be influenceed by soil deformation in tunnel excavation position, the position of negative direction is occurred, the horizontal displacement of stake end is -0.74mm. And when grouting pressure is applied, the soil body is subject to bigger additional stress, the negative horizontal level of pile foundation is caused to increase, in stake end level Displacement is changed into 1.77mm, in the case of less applying grouting pressure, increased 136.5%.And vertical displacement curve is weighed substantially Close, illustrate that grouting pressure is little to the influence of vertical displacement.
As shown in Figure 8 c, for the frictional force suffered by pile body, grouting pressure rubs to the influence very little on pile body top Force value does not have notable difference.But below pile foundation, and particularly near tunneling (in contrast curve, main performance In the range of 16m-27m), influence of the grouting pressure to friction force value is larger.Shown as tunnel side is faced, 20m-25m's In the range of, the positive friction suffered by pile foundation increases.This is just because of grouting pressure to the top soil body of tunnel horizontal median axis There are upward Additional stress component, the relative displacement increase of pile body.Similarly, below axis, between counteracting part stake soil Relative displacement, positive friction reduces, and maximum positive friction does not apply 65.7% during grouting pressure only.The back of the body tunnel side soil body During without directly being influenceed by grouting pressure, therefore carry on the back the frictional force situation suffered by the pile foundation of tunnel side and do not apply grouting pressure It is essentially identical, therefore do not illustrated herein.
As shown in figure 8d, for axial force of pile, in below pile foundation 15m, for same pile body buried depth position, slip casting pressure is applied The internal force in pile foundation is underpined after power and is greater than the situation for not applying grouting pressure, maximum decrement occurs approximately in greatly 23.6m positions, Axle power reduction amount is 109.11KN.
4) according to specific underpinning method scheme, the FEM model of many of pile foundation underpinning is set up, one support of Detailed simulation The situation that structure underpins many is changed, using the situation of change for underpining deformation of pile foundation and internal force, the feasible of underpinning method scheme is verified Property；
4.1) pile foundation underpinning engineering design
Pile foundation underpinning step：Surveying setting-out → foundation trench jet grouting pile construction → drilling underpins pile driving construction → construction foundation trench cubic metre of earth and opens Dig and soil nailing bolt-spary supports → underpin pile framing, transform beams construction → pre- top, envelope pile driving construction → pit earthwork backfill, building and Road recovers.
4.2) Deformation control of pile foundation is underpined
For the Deformation control of pile foundation, it is mainly reflected in pile lateral displacement control and Vertical Settlement Deformation control.
4.2.1) control of horizontal displacement
For horizontal displacement, according to《Technical code for building pile foundation》It is required that, when the horizontal bearing capacity of pile foundation is with Bit andits control When, the horizontal displacement permissible value of stake can be taken as 10mm, and the horizontal displacement permissible value of the works sensitive to horizontal displacement is taken as 6mm.When pile foundation level bearing capacity is with strength control, horizontal displacement permissible value can be as the following formula determined：
Wherein, RhaRepresent horizontal bearing capacity of single pile characteristic value, VxHorizontal displacement coefficient is represented, α represents horizontal distortion coefficient； The circular of each parameter may be referred to《Technical code for building pile foundation》, in the engineering proposal of the present embodiment, it is believed that when When the horizontal loading of pile foundation is no more than 6m, then it is assumed that the horizontal distortion of pile foundation meets safety requirements.
By rational numerical simulation, obtain underpining pile foundation after load action is underpined by top, the change of horizontal displacement Change as illustrated in fig. 9, left side underpins pile foundation and occurs in that inclination to the right, right side underpins pile foundation and occurs in that inclination to the left.Left side is most The horizontal displacement of big forward direction occurs, in stake top position, to reach 3.92mm, and due to being influenceed by tunnel excavation, maximum negative sense level Displacement, then occur in tunnel horizontal median axis 25m positions, and its value is 4.40mm.The horizontal distortion curve map of right side pile foundation then goes out Existing " bow " font change, there is positive-displacement in pile body upper and lower part, and pile body middle part occurs in that local negative sense displacement, maximum Positive-displacement amount equally occurs in tunnel horizontal median axis correspondence position, and maximum position value is 3.42mm.The maximum horizontal of each stake Deformation is respectively less than 6mm, then it is assumed that this underpins scheme for use, and under tunnel construction infection, the horizontal distortion of pile foundation meets engineering will Ask.
4.2.2) Vertical Settlement Deformation control
Usually, in engineering, Vertical Settlement deformation is main to be needed to meet four Con trolling index, and they are respectively：Sedimentation Amount：Framed bent pile foundation 120mm, high-rise structures 150-350mm；Differential settlement：Framework, side organ timbering, other redundant structures 0.0007- 0.005L0；Incline：Crane rail level, multilayer are high-rise, high-rise structures；Local dip：Brick body load bearing wall.In due to this programme, adopt It is to underpin top three across 9 story frame structures using double stake beam type underpinning structures, so only needing to consider deformation of pile foundation First three items, i.e. settling amount, differential settlement, and integral inclined situation.Wherein, for the deformation of pile foundation feasible value of building, can be with Reference《Technical code for building pile foundation》5.3.4 bar is chosen, it is desirable to as shown in table 2 below：
The deformation of pile foundation feasible value of table 2
According to Practical Project scheme, obtain underpining sedimentation and deformation of the pile foundation under the influence of Shield Tunneling such as Fig. 9 b institutes Show, it can be seen that the settling amount for underpining pile foundation is gradually reduced along pile body, and in same pile body buried depth position, right side underpins pile foundation Sedimentation and deformation will be significantly greater than the deformation of left side pile foundation.The largest settlement of left side pile foundation is 5.67mm, right side largest settlement It is 6.80mm, is satisfied by table 2 requirement to neighboring piles largest settlement.The maximum settlement difference of left and right pile foundation is 1.125mm ≤ 0.002L0, meets the requirement to pile foundation settlement difference in construction project.And the ratio between differential settlement and stake spacing for 0.0001≤ 0.003, thus top-out will not occur it is obvious integral inclined.
In sum, by numerical simulation analysis, after carrying out pile foundation underpinning by this engineering proposal, pile foundation is underpined in tunnel Under the influence of road shield construction, suffered internal force within the scope of bearing capacity of pile foundation, in engineering allowed band hold in the palm by malformation Change structure safe and reliable.Therefore, if using this programme in Practical Project, both can guarantee that the normal of top-out was used, and Being smoothed out for Shield Tunneling is can ensure that, scheme has engineering practical feasibility.
4.3) Internal force control of pile foundation
Done accordingly specific to the suffered influence during tunneling shield method is excavated of pile foundation is underpined under transform beams TL1 Numerical simulation analysis, because transform beams TL1 is after underpining, while the load action that three posts such as top Z are transmitted is assume responsibility for, no Again to apply balanced load in simulation process above, thus left and right underpin pile foundation deformation and stress it is different, it should separately discuss, The Numerical results for obtaining as shown in Fig. 9 c and Fig. 9 d, after constructing tunnel terminates, because the active position of load is uneven, Right side load be more than left side load, pile foundation face tunnel side-friction force curve map in be presented as left side pile foundation suffered by maximum rub Wiping power is 89.754KN, though and maximum that right side pile foundation faces big side-friction force has reached 113.38KN, increase compared with left side pile foundation 26.3%.And tunnel side is carried on the back in pile foundation, in the range of 16m-26m, for same pile body buried depth position, the friction of left side pile foundation Power is significantly less than the friction force value of right side pile foundation, and maximum difference has reached 16.9KN.And the negative friction force value of other positions is basic It is identical.
As shown in figure 9e, the pile shaft force for underpining pile foundation is substantially presented the variation tendency being gradually reduced along pile body, and due to Pile body faces the comprehensive function of tunnel Ce Jibei tunnels side-friction force, on pile shaft force curve, has a fragment position to occur in that axle The situation of power increase.For same pile body buried depth position, the axle power of right side pile foundation is significantly greater than left side pile foundation, and maximum difference reaches 862.7KN.And the position of pile foundation is different, there is the position of maximum axle power also and differs in pile body.The axle power of left side pile foundation is most About at pile body buried depth 15m, its value is 945.12KN, and right side pile foundation has occurred as soon as axle power at 10m pile bodies for big position Maximum 1647.4KN.This underpins bearing capacity of pile foundation limiting value for 4200KN, therefore the above-mentioned interior force value of pile foundation allows model in design In enclosing, underpining pile foundation will not destroy.
Therefore, in Analysis on Shield Tunnel Driven Process, the internal force of underpinning structure and deformation are satisfied by requiring, upper building peace Entirely, the engineering proposal of the present embodiment has feasibility very high.
The above, patent preferred embodiment only of the present invention, but the protection domain of patent of the present invention is not limited to This, can also such as be applied in other underpinning method schemes, and any one skilled in the art is in patent of the present invention In disclosed scope, technical scheme and its inventive concept according to patent of the present invention are subject to equivalent or change, belong to The protection domain of patent of the present invention.

Claims (9)

1. shield-tunneling construction is to the neighbouring Numerical Analysis methods for underpining Influence of Pile Foundation, it is characterised in that comprise the following steps：
1) according to specific underpinning method scheme, suitable soil body block size is chosen, determines tunnel-liner, grouting layer and underpin pile foundation Material and its parameter, and treatment to the lateral stiffness reduction coefficient and grouting layer of tunnel-liner optimizes, and sets up pile foundation Underpin the FEM model of single pile；
2) according to step 1) FEM model set up, shield tunneling process is simulated using Life-and-death element control methods, To pile lateral displacement, pile body vertical displacement, pile body friction before tunnel excavation, in tunnel excavation and after tunnel excavation terminates Power, the situation of change of pile shaft force are compared analysis, obtain underpining the Changing Pattern of deformation of pile foundation and internal force, are construction quality Control provides numeric reference foundation；
3) by change underpin in specific underpinning method scheme the distance between pile foundation, stake end and tunnel horizontal median axis position, The parameter of upper load active position and grouting pressure these engineering factors, using step 1) and step 2) method set up many FEM model under the different operating modes of group, to pile lateral displacement, pile body vertical displacement, pile body frictional force, pile body under each operating mode The situation of change of axle power and moment of flexure is compared analysis, obtains influence of each engineering factor to underpining pile foundation after tunnel excavation and makees Use rule；
4) according to specific underpinning method scheme, the FEM model of many of pile foundation underpinning is set up, using underpining deformation of pile foundation and interior The situation of change of power, verifies the feasibility of underpinning method scheme；
Step 2) the use Life-and-death element control methods to shield tunneling process be simulated, it is specific as follows：
A) the soil layer situation according to specific underpinning method scheme sets up soil model, underpinned pile base location is reserved, in reserved location Place applies the constraint on horizontal displacement direction to the soil body, it is ensured that the soil body will not be clamp-oned；Apply gravity, obtain the soil body under deadweight Stress and deformation, derive as initial field stress file and preserve；
B) set up the soil body and underpin the coefficient model of pile foundation, and read in initial field stress file, weight is applied to underpining pile foundation Power, pile top load is applied in former stake position；
C) tunneling part soil body unit is killed, simulation tunnel Stress relieving of surrounding rocks 25%, to tunneling surrounding soil Reversely apply 75% primary stress, while applying 0.15Mpa grouting at the tail of the shield machine pressure；
D) simulated ground stress releases 75%, and 25% primary stress is reversely applied to tunneling surrounding soil, while applying Grouting at the tail of the shield machine pressure；
E) simulated ground stress completely, only applies grouting at the tail of the shield machine pressure to tunneling surrounding soil；
F) cancel grouting pressure, activate liner structure and slip casting layer unit；
Wherein, step a)~b) it is simulation before tunnel excavation；Step c)~e) it is simulation in tunnel excavation；Step f) is Tunnel excavation terminate after simulation.
2. shield-tunneling construction according to claim 1 is to the neighbouring Numerical Analysis methods for underpining Influence of Pile Foundation, its feature It is：The method of the simulation use of crustal stress is in step d)：Using step excavation pattern, by the soil of the tunnel internal after excavation Body unit is set as " dummy cell ", calculates the borderline nodal force in tunnel, by these force reactions in boundary node, to simulate Primary stress, is discharged by the size and direction that change active force come simulated ground stress.
3. shield-tunneling construction according to claim 1 is to the neighbouring Numerical Analysis methods for underpining Influence of Pile Foundation, its feature It is：The pile top load that step b) is applied is 250~300t；Step d) and e) the grouting at the tail of the shield machine pressure that is applied for 0.1~ 0.2Mpa。
4. shield-tunneling construction according to claim 1 is to the neighbouring Numerical Analysis methods for underpining Influence of Pile Foundation, its feature It is：Step a) the soil models are D-P constitutive models.
5. shield-tunneling construction according to claim 1 is to the neighbouring Numerical Analysis methods for underpining Influence of Pile Foundation, its feature It is：Step 1) soil body block size be 46m × 48m, i.e., take 8D in the direction of the width, in the height direction, shield top Corresponding earth's surface is got, lower section soil body edge to shield shell outside is not less than 30m.
6. shield-tunneling construction according to claim 1 is to the neighbouring Numerical Analysis methods for underpining Influence of Pile Foundation, its feature It is：Step 1) material that uses of the tunnel-liner is C30 concrete placings, thickness is 0.3m, and Poisson's ratio is 0.2, and severe is 26KN/m3；The material that the grouting layer is used is soil cement, and thickness is 0.2m, and Poisson's ratio is 0.2, and severe is 21KN/m3；It is described It is double stake beam type underpinning structures to underpin pile foundation, and the material that wherein needle beam is used is C40 concrete placings, length × height=12.55m × 2m, Poisson's ratio is 0.2, and severe is 27.5KN/m3；Underpinned pile is diameter 1.2m, the drilling concrete-pile of length 27m, and pile body is adopted C30 concrete placings are used, Poisson's ratio is 0.2, and severe is 26KN/m3。
7. shield-tunneling construction according to claim 1 is to the neighbouring Numerical Analysis methods for underpining Influence of Pile Foundation, its feature It is：Step 1) tunnel-liner lateral stiffness reduction coefficient be 0.85.
8. shield-tunneling construction according to claim 1 is to the neighbouring Numerical Analysis methods for underpining Influence of Pile Foundation, its feature It is：Step 1) grouting layer treatment, specially：During shield method tunnel construction, when shield tail shell is pushed ahead Afterwards, the supporting role before the soil body around shield loses, internal stress release, while shield machine rearwardly clearance position spray Injecting paste material, in the presence of grouting at the tail of the shield machine pressure and inside soil body stress, the soil body, an injecting paste material will be formed in shield tail With the complicated annular mixed layer of air multiphase coexistence, this layer material is simulated using equipollent layer, the parameter of the equipollent layer is chosen such as Under：
Elastic modelling quantity is 1e9；Poisson's ratio is 0.2；Thickness uses formulaChosen, whereinIt is the reason in shield tail space By value, 1/2 of difference between shield external diameter and lining cutting external diameter is gone to；η is regulation coefficient, and span is 0.7~2.0, and soil property is harder, Value is smaller.
9. the shield-tunneling construction according to claim any one of 1-8 is to the neighbouring numerical simulation analysis side for underpining Influence of Pile Foundation Method, it is characterised in that：The unit that the FEM model is chosen includes PLAN42 units, CONTA172 units and TARGE169 Unit, wherein：Using the PLAN42 unit simulations soil body, underpin pile foundation and tunnel structure；Using the CONTA172 unit simulations soil body, Underpin the connection function between pile foundation and tunnel structure；Using TARGE169 units as object element to specific underpinning method side Case is simulated.
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