CN105386474A - Method for determining influences of leakage of waterproof curtain above foundation pit excavation face on surrounding environment - Google Patents

Abstract

The invention provides a method for determining influences of leakage of a waterproof curtain above a foundation pit excavation face on the surrounding environment. According to the method, the leakage situation of the waterproof curtain is observed according to soil layer information and foundation pit materials, and the leakage area and the actual leakage amount of the leakage position are measured on site; a three-dimensional finite element model is established, a user-defined leakage unit is set at the corresponding position of the model according to the leakage area, and the osmotic coefficient of the leakage position is determined according to the relative relational graph of the leakage amount and the osmotic coefficient in the three-dimensional model; and the osmotic coefficient of the leakage position is set for the user-defined leakage unit, foundation pit excavation and seepage solidification are simulated in sequence, and the foundation pit surrounding underground water level and the ground settling volume caused by leakage of the waterproof curtain above the foundation pit excavation face are finally determined. The method is simple and convenient to popularize and has very high application value. The method is suitable for the problem of the leakage of the waterproof curtain above the foundation pit excavation face.

Description

Determine the method that above excavation of foundation pit face, water stopping curtain seepage affects surrounding enviroment

Technical field

What the present invention relates to is a kind of method of construction engineering technical field, a kind of specifically method determining that above excavation of foundation pit face, water stopping curtain seepage affects surrounding enviroment.

Background technology

Since 21 century, the development of the underground space obtains and deepens constantly, the building on a large scale of city underground, the increasing pressure all effectively alleviating aboveground space such as underground store and underground garage.Along with the exploitation of the underground space, base pit engineering also emerges in multitude, and at present, the base pit engineering that cutting depth reaches 20 ~ 30m gets more and more, and what have even reaches more than 40m, is deep big foundation pit.For deep big foundation pit, using now is that the method that combines with water-stop curtain of well-points dewatering is to reduce groundwater table in foundation ditch widely.Wherein, water-stop curtain, in deep pit digging, had both played the effect of gear soil, and can play again the effect stoping the horizontal seepage flow of underground water, generally speaking, water-stop curtain is that deep big foundation pit engineering excavation is smooth and ensure that foundation ditch periphery does not produce the technological means of excessive deformation because of seepage action of ground water.But, in Practical Project, because the reason such as construction technology, construction technology often makes water-stop curtain appearance seepage in various degree, if seepage occurs in the saturated sandy soil above excavation of foundation pit face, may there is quicksand phenomenon in serious seepage, thus cause ground that the disasters such as sedimentation, pipeline failure, construction cracking occur.For this reason, determine the method that above excavation of foundation pit face, water stopping curtain seepage affects seepage environment, deep pit monitor excavation is had very important significance.

Through finding the retrieval of prior art document, mainly concentrate in the impact of Leakage for Groundwater position on the research of water stopping curtain seepage, for be the seepage of water-stop curtain on artesian aquifer below excavation of foundation pit face, what existing analytical method adopted is two-dimensional finite element method.As Vilarrasa utilizes the numerical simulation result of two-dimensional finite element method in " the Amethodologyforcharacterizingthehydrauliceffectivenessof anannularlow-permeabilitybarrier " within 2011, to deliver on " EngineeringGeology ", draw out the time dependent judgement figure of drawdown under different water stopping curtain seepage degree, but it is applicable to the situation that water-stop curtain cuts off aquifer completely.Pujades utilizes two-dimensional finite element method to depict drawdown derivative and the graph of a relation of time under different seepage condition in " the Hydrauliccharacterizationofdiaphragmwallsforcutandcovert unnelling " within 2012, to deliver on " EngineeringGeology ", and propose some analytic sensitivity, can be calculated the leak factor of water-stop curtain by both combinations, its shortcoming is the strip foundation be only applicable under certain condition.

In fact, the seepage of water-stop curtain belongs to space problem, and two-dimensional finite element method for be simplify plane problem, not as the three-dimensional finite element method for space problem more gears to actual circumstances, therefore, be necessary to set up Three-dimension Numerical Model and carry out above simulating excavation face water stopping curtain seepage to the impact of surrounding enviroment.But for threedimensional model, according to solid element, so at the position that leakage area is less, need the very little of stress and strain model, make number of grid on the high side, cause calculating loaded down with trivial details, even can affect the convergence of calculating, finally cannot determine that above excavation of foundation pit face, water stopping curtain seepage is on the impact of surrounding enviroment.

Summary of the invention

The present invention is directed to the deficiencies in the prior art, provide a kind of method determining that above excavation of foundation pit face, water stopping curtain seepage affects surrounding enviroment, on the basis understanding soil layer information and foundation ditch data, according to the water stopping curtain seepage situation of observation, the leakage area of on-site measurement leakage and actual seepage quantity; Set up three-dimensional finite element model, in the relevant position of three-dimensional finite element model, self-defined seepage unit is set according to leakage area, and the transmission coefficient of dependency relation figure determination leak location with reference to leakage in three-dimensional finite element model and transmission coefficient; Self-defined seepage unit is arranged to the transmission coefficient of leak location, successively simulating excavation, seepage consolidation, finally determine groundwater table and ground settlement around foundation ditch that above excavation of foundation pit face, water stopping curtain seepage causes.

The present invention is achieved by the following technical solutions:

The invention provides a kind of method determining that above excavation of foundation pit face, water stopping curtain seepage affects surrounding enviroment, described method comprises the steps:

The first step, carries out site inspection to foundation ditch, determines compartmentalize soil information and groundwater occurrence situation, and carries out laboratory soil test by boring extracting soil, obtains the physical and mechanical parameter of soil layer;

Second step, obtains foundation ditch planar dimension, cutting depth, and water-stop curtain thickness, buried depth, modulus of elasticity, transmission coefficient, determines the water-stop curtain equivalent elastic modulus E ' considering strength degradation effect;

3rd step, the leakage scenarios of water-stop curtain above observation excavation of foundation pit face, record leak location, seepage form, determine water stopping curtain seepage place leakage area D, actual seepage quantity Q _k;

4th step, adopts finite element analysis software to set up the three-dimensional fluid structure interaction mode of water stopping curtain seepage above excavation of foundation pit face; According to field investigation, at the corresponding leak location of three-dimensional fluid structure interaction mode, self-defined seepage unit is set according to leakage area, Simulation of Excavation Process;

5th step, to the osmotic coefficient k of self-defined seepage unit hypothesis varying number level _j, activate the seepage boundary inside water-stop curtain above excavation of foundation pit face, determine the leakage Q of water-stop curtain under each operating mode after seepage a period of time (such as 1 day);

6th step, sets up Descartes's rectangular coordinate system, and transverse axis is the osmotic coefficient k of varying number level _j, the longitudinal axis is leakage Q, makes leakage Q and osmotic coefficient k _jdependency relation figure, and according to the actual seepage quantity Q of graph of a relation determination on-site measurement _kthe leak factor k of corresponding leak location;

7th step, arranges the osmotic coefficient k of leak location, carries out seepage consolidation simulation to the self-defined seepage unit in three-dimensional fluid structure interaction mode, determine groundwater table and ground settlement around foundation ditch that above excavation of foundation pit face, water stopping curtain seepage causes.

Preferably, in the first step, described compartmentalize soil refers to: divided the soil layer within the scope of 2.5 times of foundation depths below earth's surface in foundation ditch by the method for boring extracting soil, obtain job site soil sample subsequently and carry out laboratory soil test, obtain job site compartmentalize soil information and geological information, determine each soil layer soil nature and corresponding the thickness of the layer;

Preferably, in the first step, described groundwater occurrence situation refers to: adopt boring spy water instrument to carry out underground water boring to foundation ditch place and verify, judged type and the thickness in aquifer by the soil body type disclosed; The fixed level of drilling well observation different water cut layer, takes water proof measure to survey its fixed level by behind tested aquifer and the isolation of other aquifers for artesian aquifer.

Preferably, in the first step, described boring extracting soil refers to: around foundation ditch, obtain on-the-spot soil sample with thin-wall sampler, soil sample number is advisable with three test specimens.

Preferably, in the first step, described laboratory soil test refers to: density test, specific gravity test, water ratio test, triaxial test, conventional Axial compression tests, load test and results of permeability tests.

Preferably, in the first step, described physical and mechanical parameter refers to: the severe of the soil body, void ratio, effective cohesion intercept, angle of internal friction, modulus of compressibility, poisson's ratio, modulus of deformation, horizontal-hole blasting and vertical permeability coefficient.

Preferably, in second step, described water-stop curtain equivalent elastic modulus E ' meets following formula:

E’＝ηE _s，

Wherein: η is modulus reduction coefficient, gets 1/5; E _sfor the modulus of elasticity of steel concrete.

Preferably, in second step, described water-stop curtain transmission coefficient is divided into horizontal direction and vertical direction, and the transmission coefficient of horizontal direction and vertical direction all gets concrete filtration coefficient.

Preferably, in the 3rd step, described leak location refers to: seepage region is at the position coordinates of whole foundation ditch plane, and the depth size in foundation ditch vertical direction.

Preferably, in the 3rd step, described seepage form refers to: the seepage shape that underground water presents when water-stop curtain infiltrates foundation ditch.

Preferably, in the 3rd step, described water stopping curtain seepage place leakage area D determines in the following manner:

Range estimation seepage region is positioned at the Position Approximate of ground surface, ground surface near institute's excavation pit is chosen object of reference (object of reference has position coordinates on foundation ditch plan view), measure the distance in object of reference and seepage region, determine the position coordinates of seepage region in whole foundation ditch plane; Seepage region coordinate place, plan-position transfer lining rope, respectively measure seepage region top degree of depth h ₁, lowermost end degree of depth h ₂and the distance l between the side of two, seepage region, obtain leakage area D:

D＝l×(h ₂-h ₁)。

Preferably, in the 3rd step, described actual seepage quantity Q _kdetermine in the following manner:

Above excavation of foundation pit face, lay a drum immediately below water stopping curtain seepage place, measure the basal diameter d of drum, the height h of bucket ₃, the height h of water in bucket ₄; The on-site measurement leak location leakage Q of 2 hours _2ksize; Described Q _2kmeet following formula:

Q _2k＝NV+(πd ²/4)×h ₄，

In formula: N is 2 hours connects the barrelage of percolating water, and V is drum volume; Described drum volume V meets following formula:

V＝(πd ²/4)×h ₃；

By the leakage Q of 2 hours of on-site measurement _2k, the actual seepage quantity Q of estimation seepage after 1 day _k, i.e. Q _k=12Q _2k.

Preferably, in the 4th step, described self-defined seepage unit refers to the two nodal line unit with certain permeability and rigidity, the solid element conode in this self-defined seepage unit and threedimensional model, and has three basic parameters: leakage area D _z, osmotic coefficient k and elastic modulus E.Particularly, leakage area D _zdetermining by surveying leakage area D in the 3rd step, meeting formula: D _z=D/n, the grid node of the n process that is water stopping curtain seepage position in formula; Osmotic coefficient k is by the osmotic coefficient k of setting varying number level _jdetermine; Elastic modulus E gets 0.01.

Preferably, in the 4th step, described three-dimensional fluid structure interaction mode refers to: model scope is centered by foundation ditch, and horizontal direction is greater than dewatering well radius of influence R; Model vertical direction is greater than the artesian aquifer base plate place degree of depth; Carry out stress and strain model to model, input Soil Parameters and water level, and the primary condition of setting model and fringe conditions, wherein: the primary condition of model is: water level string holes pressure is zero, displacement is zero; Fringe conditions is: model surrounding is constant water level boundary, and bottom is fixed boundary condition; The soil body and water-stop curtain all adopt 8 node holes pressure unit, and arrange contact surface between water-stop curtain and the soil body, contact surface friction factor is 0.25.More preferably, described dewatering well radius of influence R adopts the empirical formula of artesian aquifer:

$R=10S\sqrt{K},$

In formula: S is drawdown (m), K is the horizontal-hole blasting (m/d) of artesian aquifer.

Preferably, in the 4th step, described Simulation of Excavation Process refers to: weaken the soil body inside foundation ditch, and remove the inner soil body unit of foundation ditch and complete Base Pit Excavation Simulation, ground loss rate is regulated by the weakening degree of the soil body inside foundation ditch, controls within 1%.

Preferably, in the 5th step, the osmotic coefficient k of described varying number level _jget 10 ^-6m/s, 10 ^-5m/s, 10 ^-4m/s, 10 ^-3m/s, 10 ^-2m/s.

Preferably, in the 5th step, the boundary condition of seepage flow above described activation excavation of foundation pit face inside water-stop curtain refers to: the pore water pressure inside water-stop curtain above excavation of foundation pit face is set to zero.

Preferably, in the 6th step, described actual seepage quantity Q _kthe leak factor k of corresponding leak location determines in the following manner:

The longitudinal axis of dependency relation figure marks actual seepage quantity Q _kposition, and make horizon, with Q ~ k _jdependency relation figure intersects at a point, and makes vertical line, namely obtain actual seepage quantity Q at this point _kthe leak factor k of corresponding leak location.

Compared with prior art, the present invention has following beneficial effect:

In the water stopping curtain seepage model of the present invention above excavation of foundation pit face, self-defined seepage unit is arranged to leakage, to solve in threedimensional model stress and strain model difficulty, calculate the difficult problems such as loaded down with trivial details, finally to determine above excavation of foundation pit face water stopping curtain seepage to the impact of surrounding enviroment.The inventive method is simple, is convenient to promote, and has very large using value.The present invention is applicable to the problem of water stopping curtain seepage above excavation of foundation pit face.

Accompanying drawing explanation

Fig. 1 a is the grid partial enlarged drawing of water stopping curtain seepage drag above one embodiment of the invention excavation of foundation pit face;

Fig. 1 b is water stopping curtain seepage drag three dimensional network trrellis diagram above one embodiment of the invention excavation of foundation pit face;

Fig. 2 is the self-defined seepage cell schematics of one embodiment of the invention;

Fig. 3 is leakage Q and k under one embodiment of the invention water stopping curtain seepage _jdependency relation figure (seepage is after 1 day);

Fig. 4 is the first artesian aquifer section I-I ' drawdown figure (stablizing) under one embodiment of the invention water stopping curtain seepage;

Fig. 5 is section I-I ' ground fallout plot (100 days) under one embodiment of the invention water stopping curtain seepage.

Detailed description of the invention

Below in conjunction with accompanying drawing, embodiments of the invention are elaborated: the present embodiment is implemented premised on technical solution of the present invention, give detailed embodiment and concrete operating process, but protection scope of the present invention is not limited to following embodiment.

Certain base pit engineering is Circular Pit, and adopt high-pressure rotary jet grouting pile as water-stop curtain, the aquifer system of foundation ditch present position is the aquifer of multilayer-aquitard alternating layers.When excavation of foundation pit, there is Seepage in the water-stop curtain above excavation of foundation pit face.

The present embodiment provides a kind of method determining that above excavation of foundation pit face, water stopping curtain seepage affects surrounding enviroment, and described method comprises the steps:

The first step, carries out site inspection to foundation ditch, determines compartmentalize soil information and groundwater occurrence situation, and carries out laboratory soil test by boring extracting soil, obtains the physical and mechanical parameter of soil layer.

By the soil layer residing for boring extracting soil method determination foundation ditch be from top to bottom:

Silt, the silty clay of first floor to be thickness be 14m, belong to water table aquifer;

The silty clay of the second layer to be thickness be 7m, belongs to I aquitard;

The flour sand of third layer to be thickness be 10m, belongs to I artesian aquifer;

The silty clay of the 4th layer of to be thickness be 5m, belongs to II aquitard;

The silt of layer 5 to be thickness be 18m, II artesian aquifer;

The silty clay of layer 6 to be thickness be 6m, belongs to III aquitard.

The physico-mechanical properties making conventional indoor acquisition foundation pit earth layer soil body that fetches earth is:

The severe of first floor silt, silty clay is 19.6kN/m ³, poisson's ratio is 0.25, void ratio is 0.80, modulus of compressibility is 6530KPa, angle of internal friction is 25 °, horizontal-hole blasting is 6.94 × 10 ^-8m/s, vertical permeability coefficient are 3.47 × 10 ^-8m/s;

The severe of second layer silty clay is 19.8kN/m ³, poisson's ratio is 0.30, modulus of compressibility is 5410KPa, angle of internal friction is 21 °, void ratio is 0.71, horizontal-hole blasting is 2.31 × 10 ^-8m/s, vertical permeability coefficient are 8.10 × 10 ^-9m/s;

The severe of third layer flour sand is 20.4kN/m ³, poisson's ratio is 0.25, void ratio is 0.58, modulus of deformation is 16000KPa, angle of internal friction is 30 °, effective cohesion intercept is 4.0kPa, horizontal-hole blasting is 4.86 × 10 ^-5m/s, vertical permeability coefficient are 1.74 × 10 ^-5m/s;

The severe of the 4th layer of silty clay is 20.2kN/m ³, poisson's ratio is 0.30, void ratio is 0.72, modulus of compressibility is 6260KPa, angle of internal friction is 24 °, horizontal-hole blasting is 1.16 × 10 ^-8m/s, vertical permeability coefficient are 4.64 × 10 ^-9m/s;

The severe of layer 5 silt is 20.3kN/m ³, poisson's ratio is 0.25, void ratio is 0.68, modulus of deformation is 12570KPa, angle of internal friction is 30 °, effective cohesion intercept is 4.8kPa, horizontal-hole blasting is 2.31 × 10 ^-5m/s, vertical permeability coefficient are 9.26 × 10 ^-6m/s;

The severe of layer 6 silty clay is 20.0kN/m ³, poisson's ratio is 0.30, void ratio is 0.68, modulus of compressibility is 5350KPa, angle of internal friction is 22 °, horizontal-hole blasting is 9.29 × 10 ^-9m/s, vertical permeability coefficient are 4.63 × 10 ^-9m/s;

Second step, obtains foundation ditch planar dimension, cutting depth and water-stop curtain thickness, buried depth, modulus of elasticity, transmission coefficient information, determines the water-stop curtain equivalent elastic modulus considering strength degradation effect.

The foundation ditch of the present embodiment is Circular Pit, and radius is 18m, and cutting depth is 32m; The thickness of water-stop curtain is 1.2m, the degree of depth is 48m, severe is 25kN/m ³, horizontal-hole blasting is 1.0 × 10 ^-9m/s, vertical permeability coefficient are 1.0 × 10 ^-9m/s.Consider that the water-stop curtain equivalent elastic modulus E ' of strength degradation effect meets following formula:

E’＝ηE _s，

Wherein: η is modulus reduction coefficient, gets 1/5; E _sfor the modulus of elasticity of steel concrete, obtaining its value is:

$E^{,}={\mathrm{\ηE}}_s=\frac{1}{5}\×34500=6900MPa.$

3rd step, the leakage scenarios of water-stop curtain above observation excavation of foundation pit face, in whole foundation ditch plane, leak location A (as shown in Figure 1a) is positioned on the water-stop curtain inside wall in 45 ° of directions, east by north, foundation ditch center, and seepage form is vertical wire seepage; By transferring lining rope, measure the tip depth h of leakage ₁=21m, bottom degree of depth h ₂=24m, the distance l=5cm between the side of two, seepage region, therefore leakage area D=0.15m ²; Described actual seepage quantity Q _kdetermine in the following manner:

Above excavation of foundation pit face, lay a basal diameter d immediately below water stopping curtain seepage place is 1m, the height h of bucket ₃for the drum of 1.5m, the on-site measurement leak location leakage Q of 2 hours _2ksize, the height h of water in bucket after 2 hours ₄for 1.046m, wherein, Q _2kmeet following formula:

$Q_{2k}=NV+\left({\mathrm{\πd}}^2/4\right)\×h_4=1\×\frac{\mathrm{\π}\×1^2}{4}\×1.5+\frac{\mathrm{\π}\×1^2}{4}\×1.046=1.9996m^3$

In formula: N is 2 hours connects the barrelage of percolating water, and being 1, V is drum volume, and V meets following formula:

V＝(πd ²/4)×h ₃＝(π×1 ²/4)×1.5＝1.1781m ³。

By the leakage Q of 2 hours of on-site measurement _2k, the actual seepage quantity Q of estimation seepage after 1 day _k, that is:

Q _k＝12Q _2k＝12×1.9996＝23.9952m ³。

4th step, adopts finite element analysis software to set up the three-dimensional fluid structure interaction mode of water stopping curtain seepage above excavation of foundation pit face; According to field investigation, at the corresponding leak location of three-dimensional fluid structure interaction mode, self-defined seepage unit is set according to leakage area, Simulation of Excavation Process.

Determine dewatering well radius of influence R, in the present embodiment, I artesian aquifer transmission coefficient is 4.86 × 10 ^-5m/s, i.e. 4.2m/d, I artesian aquifer water level 1m under excavation of foundation pit face in foundation ditch in Excavation Process, namely pressure water head is-25m, and the initial pressure water head of this engineering is-1m, therefore drawdown is 24m, and dewatering well radius of influence R is:

$R=10S\sqrt{K}=10\×24\×\sqrt{4.2}=492m$

Analytical model is centered by foundation ditch, and horizontal direction is greater than dewatering well radius of influence 492m, to external expansion 500m, to eliminate the impact of fringe conditions on result of calculation; In the plane, research range is 1000 × 1000m ²; On vertical, compute depth is 60m.In the horizontal direction, by foundation ditch outwards from dense to sparse, every layer plane contains 2920 nodes to finite element grid, 2829 unit; In vertical direction, 17 layers are divided into.Whole model has 54720 nodes, 48093 unit.

Water stopping curtain seepage drag grid partial enlarged drawing, three dimensional network trrellis diagram above excavation of foundation pit face as shown in Figure 1 a, 1 b.Input Soil Parameters and water level, and the primary condition of setting model and fringe conditions.Wherein:

The primary condition of model is: in analytical model, each aquifer initial water level is underground 1m, and water level string holes pressure is zero, and displacement is zero;

Fringe conditions is: model surrounding is constant water level boundary, and bottom is fixed boundary condition.

The soil body and water-stop curtain all adopt 8 node holes pressure unit, and arrange contact surface between water-stop curtain and the soil body, contact surface friction factor is 0.25.

According to field investigation, arrange self-defined seepage unit at analytical model corresponding leak location A (as shown in Figure 1a), leak location altogether through 3 nodes, therefore arranges 3 self-defined seepage unit, leakage area D _z=D/n=0.15/3=0.05m ², Fig. 2 is self-defined seepage cell schematics.

In the present embodiment, described Simulation of Excavation Process refers to: weaken the soil body inside foundation ditch, and remove the inner soil body unit of foundation ditch and complete Base Pit Excavation Simulation, ground loss rate is regulated by the weakening degree of the soil body inside foundation ditch, controls within 1%.

5th step, to the leak factor k of self-defined seepage unit hypothesis varying number level _j, activate the seepage boundary inside water-stop curtain above excavation of foundation pit face, determine the water stopping curtain seepage place seepage leakage Q 1 day after of each operating mode above excavation of foundation pit face.

The osmotic coefficient k of the varying number level described in the present embodiment _jbe taken as 10 ^-6m/s, 10 ^-5m/s, 10 ^-4m/s, 10 ^-3m/s, 10 ^-2m/s.

The boundary condition of seepage flow above activation excavation of foundation pit face described in the present embodiment inside water-stop curtain refers to: the pore water pressure inside water-stop curtain above excavation of foundation pit face is set to zero.

6th step, sets up Descartes's rectangular coordinate system, and transverse axis is the osmotic coefficient k of varying number level _j, the longitudinal axis is leakage Q, makes leakage Q and osmotic coefficient k _jdependency relation figure (as shown in Figure 3), according to the actual seepage quantity Q of on-site measurement _k=23.9952m ³, the longitudinal axis of dependency relation figure finds this point, and makes horizon, the abscissa that this horizon is corresponding with dependency relation figure intersection point is the osmotic coefficient k of leak location:

k＝1.0×10 ^-5m/s。

7th step, arranges osmotic coefficient k=1.0 × 10 of leak location to the self-defined seepage unit in three-dimensional fluid structure interaction mode ^-5m/s, carry out seepage consolidation simulation, finally to draw above excavation of foundation pit face I artesian aquifer section I-I ' drawdown figure (stablizing) (as shown in Figure 4), section I-I ' ground fallout plot (100 days) (as shown in Figure 5) under A place, water stopping curtain seepage position wire seepage.

The present embodiment can determine that above excavation of foundation pit face, water stopping curtain seepage is on the impact of surrounding enviroment accurately, finally to draw above excavation of foundation pit face groundwater table and ground settlement around water stopping curtain seepage place, the research only concentrating on Leakage for Groundwater position of comparing seem more comprehensively, more scientific, more reliable.

Above specific embodiments of the invention are described.It is to be appreciated that the present invention is not limited to above-mentioned particular implementation, those skilled in the art can make various distortion or amendment within the scope of the claims, and this does not affect flesh and blood of the present invention.

Claims (11)

1. determine the method that above excavation of foundation pit face, water stopping curtain seepage affects surrounding enviroment, it is characterized in that, described method comprises the steps:

The first step, carries out site inspection to foundation ditch, determines compartmentalize soil information and groundwater occurrence situation, and carries out laboratory soil test by boring extracting soil, obtains the physical and mechanical parameter of soil layer;

Second step, obtains foundation ditch planar dimension, cutting depth, and water-stop curtain thickness, buried depth, modulus of elasticity, transmission coefficient, determines the water-stop curtain equivalent elastic modulus E ' considering strength degradation effect;

3rd step, the leakage scenarios of water-stop curtain above observation excavation of foundation pit face, record leak location, seepage form, determine water stopping curtain seepage place leakage area D, actual seepage quantity Q _k;

4th step, adopts finite element analysis software to set up the three-dimensional fluid structure interaction mode of water stopping curtain seepage above excavation of foundation pit face; According to field investigation, at the corresponding leak location of three-dimensional fluid structure interaction mode, self-defined seepage unit is set according to leakage area, Simulation of Excavation Process;

5th step, to the osmotic coefficient k of self-defined seepage unit hypothesis varying number level _j, activate the seepage boundary inside water-stop curtain above excavation of foundation pit face, determine the leakage Q of water-stop curtain under each operating mode after seepage a period of time;

6th step, sets up Descartes's rectangular coordinate system, and transverse axis is the osmotic coefficient k of varying number level _j, the longitudinal axis is leakage Q, makes leakage Q and osmotic coefficient k _jdependency relation figure, and according to the actual seepage quantity Q of graph of a relation determination on-site measurement _kthe leak factor k of corresponding leak location;

7th step, arranges the osmotic coefficient k of leak location, carries out seepage consolidation simulation to the self-defined seepage unit in three-dimensional fluid structure interaction mode, determine groundwater table and ground settlement around foundation ditch that above excavation of foundation pit face, water stopping curtain seepage causes.

2. a kind of method determining that above excavation of foundation pit face, water stopping curtain seepage affects surrounding enviroment according to claim 1, is characterized in that, in the first step:

Described compartmentalize soil refers to: divided the soil layer within the scope of 2.5 times of foundation depths below earth's surface in foundation ditch by the method for boring extracting soil, obtain job site soil sample subsequently and carry out laboratory soil test, obtain job site compartmentalize soil information and geological information, determine each soil layer soil nature and corresponding the thickness of the layer;

Described groundwater occurrence situation refers to: adopt boring spy water instrument to carry out underground water boring to foundation ditch place and verify, judged type and the thickness in aquifer by the soil body type disclosed; The fixed level of drilling well observation different water cut layer, takes water proof measure to survey its fixed level by behind tested aquifer and the isolation of other aquifers for artesian aquifer.

3. a kind of method determining that above excavation of foundation pit face, water stopping curtain seepage affects surrounding enviroment according to claim 1, is characterized in that, in second step, described water-stop curtain equivalent elastic modulus E ' meets following formula:

E’＝ηE _s，

Wherein: η is modulus reduction coefficient, gets 1/5; E _sfor the modulus of elasticity of steel concrete.

4. a kind of method determining that above excavation of foundation pit face, water stopping curtain seepage affects surrounding enviroment according to claim 1, it is characterized in that, in second step, described water-stop curtain transmission coefficient is divided into horizontal direction and vertical direction, and the transmission coefficient of horizontal direction and vertical direction all gets concrete filtration coefficient.

5. a kind of method determining that above excavation of foundation pit face, water stopping curtain seepage affects surrounding enviroment according to claim 1, is characterized in that, in the 3rd step:

Described leak location refers to: seepage region is at the position coordinates of whole foundation ditch plane, and the depth size in foundation ditch vertical direction;

Described seepage form refers to: the seepage shape that underground water presents when water-stop curtain infiltrates foundation ditch.

6. a kind of method determining that above excavation of foundation pit face, water stopping curtain seepage affects surrounding enviroment according to claim 1, is characterized in that, in the 3rd step, described water stopping curtain seepage place leakage area D determines in the following manner:

Range estimation seepage region is positioned at the Position Approximate of ground surface, ground surface near institute's excavation pit chooses object of reference, object of reference has position coordinates on foundation ditch plan view, measures the distance in object of reference and seepage region, determines the position coordinates of seepage region in whole foundation ditch plane; Transfer lining rope at the coordinate place, plan-position in seepage region, measure seepage region top degree of depth h respectively ₁, lowermost end degree of depth h ₂and the distance l between the side of two, seepage region, obtain leakage area D:

D＝l×(h ₂-h ₁)。

7. a kind of method determining that above excavation of foundation pit face, water stopping curtain seepage affects surrounding enviroment according to claim 1, is characterized in that, in the 3rd step, and described actual seepage quantity Q _kdetermine in the following manner:

Above excavation of foundation pit face, lay a drum immediately below water stopping curtain seepage place, measure the basal diameter d of drum, the height h of bucket ₃, the height h of water in bucket ₄; The on-site measurement leak location leakage Q of 2 hours _2ksize; Described Q _2kmeet following formula:

Q _2k＝NV+(πd ²/4)×h ₄，

In formula: N is 2 hours connects the barrelage of percolating water, and V is drum volume; Described drum volume V meets following formula:

V＝(πd ²/4)×h ₃；

By the leakage Q of 2 hours of on-site measurement _2k, the actual seepage quantity Q of estimation seepage after 1 day _k, i.e. Q _k=12Q _2k.

8. a kind of method determining that above excavation of foundation pit face, water stopping curtain seepage affects surrounding enviroment according to claim 1, is characterized in that, in the 4th step:

Described self-defined seepage unit refers to the two nodal line unit with certain permeability and rigidity, the solid element conode in this self-defined seepage unit and threedimensional model, and has three basic parameters: leakage area D _z, osmotic coefficient k and elastic modulus E; Wherein: leakage area D _zdetermined by the leakage area D surveyed in the 3rd step, meet formula: D _z=D/n, the grid node of the n process that is water stopping curtain seepage position in formula; Osmotic coefficient k is by the osmotic coefficient k of setting varying number level _jdetermine; Elastic modulus E gets 0.01;

Described three-dimensional fluid structure interaction mode refers to: model scope is centered by foundation ditch, and horizontal direction is greater than dewatering well radius of influence R; Model vertical direction is greater than the artesian aquifer base plate place degree of depth; Carry out stress and strain model to model, input Soil Parameters and water level, and the primary condition of setting model and fringe conditions, wherein: the primary condition of model is: water level string holes pressure is zero, displacement is zero; Fringe conditions is: model surrounding is constant water level boundary, and bottom is fixed boundary condition; The soil body and water-stop curtain all adopt 8 node holes pressure unit, arrange contact surface between water-stop curtain and the soil body;

Described Simulation of Excavation Process refers to: weaken the soil body inside foundation ditch, and remove the inner soil body unit of foundation ditch and complete Base Pit Excavation Simulation, ground loss rate is regulated by the weakening degree of the soil body inside foundation ditch, controls within 1%.

9. a kind of method determining that above excavation of foundation pit face, water stopping curtain seepage affects surrounding enviroment according to claim 8, is characterized in that, described dewatering well radius of influence R adopts the empirical formula of artesian aquifer:

$R=10S\sqrt{K},$

In formula: S is drawdown (m), K is the horizontal-hole blasting (m/d) of artesian aquifer;

Described contact surface friction factor is 0.25.

10. a kind of method determining that above excavation of foundation pit face, water stopping curtain seepage affects surrounding enviroment according to any one of claim 1-9, is characterized in that, in the 5th step:

The osmotic coefficient k of described varying number level _jget 10 ^-6m/s, 10 ^-5m/s, 10 ^-4m/s, 10 ^-3m/s, 10 ^-2m/s;

The boundary condition of seepage flow above described activation excavation of foundation pit face inside water-stop curtain refers to: the pore water pressure inside water-stop curtain above excavation of foundation pit face is set to zero.

11. a kind of methods determining that above excavation of foundation pit face, water stopping curtain seepage affects surrounding enviroment according to any one of claim 1-9, is characterized in that, in the 6th step, and described actual seepage quantity Q _kthe osmotic coefficient k of corresponding leak location is determined in the following manner:

The longitudinal axis of dependency relation figure marks actual seepage quantity Q _kposition, and make horizon, with Q ~ k _jdependency relation figure intersects at a point, and makes vertical line, namely obtain actual seepage quantity Q at this point _kthe leak factor k of corresponding leak location.