CN113293767B - Underground structure upper soil body construction system and method - Google Patents
Underground structure upper soil body construction system and method Download PDFInfo
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- CN113293767B CN113293767B CN202110572987.4A CN202110572987A CN113293767B CN 113293767 B CN113293767 B CN 113293767B CN 202110572987 A CN202110572987 A CN 202110572987A CN 113293767 B CN113293767 B CN 113293767B
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- E—FIXED CONSTRUCTIONS
- E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
- E02D—FOUNDATIONS; EXCAVATIONS; EMBANKMENTS; UNDERGROUND OR UNDERWATER STRUCTURES
- E02D17/00—Excavations; Bordering of excavations; Making embankments
- E02D17/02—Foundation pits
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- E—FIXED CONSTRUCTIONS
- E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
- E02D—FOUNDATIONS; EXCAVATIONS; EMBANKMENTS; UNDERGROUND OR UNDERWATER STRUCTURES
- E02D1/00—Investigation of foundation soil in situ
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- E—FIXED CONSTRUCTIONS
- E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
- E02D—FOUNDATIONS; EXCAVATIONS; EMBANKMENTS; UNDERGROUND OR UNDERWATER STRUCTURES
- E02D19/00—Keeping dry foundation sites or other areas in the ground
- E02D19/06—Restraining of underground water
- E02D19/10—Restraining of underground water by lowering level of ground water
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- E—FIXED CONSTRUCTIONS
- E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
- E02D—FOUNDATIONS; EXCAVATIONS; EMBANKMENTS; UNDERGROUND OR UNDERWATER STRUCTURES
- E02D27/00—Foundations as substructures
- E02D27/01—Flat foundations
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- E—FIXED CONSTRUCTIONS
- E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
- E02D—FOUNDATIONS; EXCAVATIONS; EMBANKMENTS; UNDERGROUND OR UNDERWATER STRUCTURES
- E02D27/00—Foundations as substructures
- E02D27/01—Flat foundations
- E02D27/016—Flat foundations made mainly from prefabricated concrete elements
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- E—FIXED CONSTRUCTIONS
- E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
- E02D—FOUNDATIONS; EXCAVATIONS; EMBANKMENTS; UNDERGROUND OR UNDERWATER STRUCTURES
- E02D3/00—Improving or preserving soil or rock, e.g. preserving permafrost soil
- E02D3/02—Improving by compacting
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- G—PHYSICS
- G06—COMPUTING; CALCULATING OR COUNTING
- G06F—ELECTRIC DIGITAL DATA PROCESSING
- G06F30/00—Computer-aided design [CAD]
- G06F30/10—Geometric CAD
- G06F30/13—Architectural design, e.g. computer-aided architectural design [CAAD] related to design of buildings, bridges, landscapes, production plants or roads
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- G—PHYSICS
- G06—COMPUTING; CALCULATING OR COUNTING
- G06F—ELECTRIC DIGITAL DATA PROCESSING
- G06F30/00—Computer-aided design [CAD]
- G06F30/20—Design optimisation, verification or simulation
- G06F30/23—Design optimisation, verification or simulation using finite element methods [FEM] or finite difference methods [FDM]
Abstract
The application relates to the field of buildings and provides a system and a method for constructing soil on the upper part of an underground structure. The system for constructing the soil body on the upper part of the underground structure comprises a precipitation well, a plurality of engineering piles, a simulation analysis system, a field data monitoring system and a regulation and control system, wherein the regulation and control system regulates and controls the water level of the precipitation well, so that the actual vertical lifting deformation value of the underground structure in the unloading process of the soil body on the upper part of the underground structure is smaller than or equal to the simulated vertical lifting deformation value simulated by the simulation analysis system. The regulation and control system is combined with effective data acquired by the field data monitoring system and a simulated precipitation depth value and a simulated vertical upward lifting deformation value simulated by the simulation and analysis system, and the water level of the precipitation well is regulated and controlled in real time in the upper soil unloading process of the underground structure, so that the actual vertical upward lifting deformation value of the underground structure is smaller than or equal to the simulated vertical upward lifting deformation value, the vertical upward lifting deformation of the underground structure is always not more than a specified allowable range, and the stability and the safety of the underground structure are ensured.
Description
Technical Field
The invention relates to the technical field of building construction, in particular to a system and a method for constructing an upper soil body of an underground structure.
Background
The problem of land resource shortage caused by urban development enables limited land resources to be fully utilized, and the development and utilization of underground space are important development trends. The development of the underground space often causes the situation that foundation pit engineering straddles over the existing underground structure (such as a subway tunnel); the unloading of the foundation pit excavation above the existing underground structure inevitably affects the existing underground structure. The method comprises the following specific steps: the process that the upper portion soil body of existing underground structure carries out foundation ditch excavation is the process of the upper portion soil body off-load of existing underground structure in fact, must arouse the upper portion soil body between foundation ditch bottom and the existing underground structure to take place to kick-back, and the effect that the resilience of upper portion soil body can produce the come-up to existing underground structure leads to the vertical deflection that lifts of underground structure to exceed standard allowed range, influences existing underground structure's stability and safety.
Disclosure of Invention
The invention aims to overcome the problem that the vertical uplift deformation of an underground structure exceeds the standard allowable requirement due to the unloading of the upper soil body of the underground structure, so that the structural stability and the safety of the underground structure are influenced, and provides a construction method of the upper soil body of the underground structure, which comprises the following steps:
establishing an integral model of a soil construction structure at the upper part of the underground structure by using finite element analysis software, and simulating all construction processes of the construction structure, wherein the construction processes comprise engineering pile construction, foundation pit partition layer-by-layer excavation construction and precipitation construction of a plurality of precipitation wells;
simulating simulated precipitation depth values of precipitation wells and simulated vertical uplift deformation values of the underground structure, which correspond to a plurality of unloading depths of unloading of an upper soil body of the underground structure respectively, by using the finite element analysis software according to all construction processes simulated by the finite element analysis software;
carrying out engineering pile construction on peripheral soil bodies of the underground structure;
constructing precipitation wells in the peripheral soil bodies of the underground structure, and setting the precipitation depth value of each precipitation well as a simulated precipitation depth value corresponding to the unloading depth;
unloading the upper soil body, detecting an actual vertical uplifting deformation value of the underground structure in real time, and regulating and controlling the water level of the dewatering well when the actual vertical uplifting deformation value is larger than the simulated vertical uplifting deformation value, so that the actual vertical uplifting deformation value detected in real time is smaller than or equal to the simulated vertical uplifting deformation value;
and repeatedly executing the previous step, excavating the soil body with the next unloading depth, and regulating the water level of the dewatering well to ensure that the actual vertical lifting deformation values detected in real time in the excavating process are all smaller than or equal to the simulated vertical lifting deformation values until the unloading construction of the upper soil body of the underground structure is completed.
Further, the water level of the dewatering well is regulated and controlled according to a formula F Floating body =F Descend +2 F Resistance device +F Resist against Adjusting to enable the adjusted water level reduction height delta h in the precipitation well to meet the formula:
in the formula, F Floating body A floating force F applied to the upper soil body Descend The settling force to which the upper soil body is subjected for precipitation of the precipitation well, F Resistance device Is the frictional resistance to the upward flotation of the underground structure, F Is resistant to Deformation resistance to deformation of the underground structure due to its own stiffness under the influence of uplift forces;
wherein the floating force F Floating body The calculation formula of (c) is: f Floating body =γ Soil for planting h Unloading l Digging machine D，
Said settling force F Descend The calculation formula of (2) is as follows: f Lower the main body =αγ Water (W) Δhl Digging tool D，
The frictional resistance F Resistance block The calculation formula of (2) is as follows: f Resistance block =βKγ Soil for planting h Is buried in l Digging tool D，
Said deformation resistance F Resist against The calculation formula of (c) is: f Is resistant to =（384ηEIs）/5l Digging machine 3 ，
In the above formula: gamma ray Soil for planting Is the weight (kN/m) of the upper soil body 3 ），h Unloading The unloading depth (m) of the upper soil body,l digging machine The unloading length (m) of the upper soil body, D the diameter (m) of the underground structure, alpha the regulating coefficient, gamma Water (W) Is the water weight (kN/m) in the surrounding soil of the underground structure 3 ) Delta h is the water level reduction height (m) in the precipitation well, beta is the coefficient of regulation, K is the coefficient of friction angle, h Is buried in Is the buried depth (m) of the underground structure, and EI is the longitudinal stiffness (kN m) of the underground structure 2 ) Eta is the effective rate of rigidity, and s is the vertical uplift deformation value (mm) of the underground structure in the unloading length of the upper soil body.
The beneficial effects of the further scheme are as follows: the water level of the dewatering well is regulated in real time, so that the settlement acting force of the upper soil body caused by dewatering is regulated, and dynamic balance with the floating acting force borne by the upper soil body in unloading is realized by combining the deformation resistance of the underground structure.
And further, the construction method comprises a construction step of a counter-pressure structure after the unloading construction of the upper soil body of the underground structure is completed, wherein the counter-pressure structure is permanently arranged at the bottom of a foundation pit formed after the unloading of the upper soil body and is connected with the tops of the engineering piles.
The beneficial effects of the further scheme are as follows: through set up the back pressure structure in the bottom of foundation ditch, utilize the dead weight of back pressure structure to exert pressure in order to restrict the vertical upward deformation value of underground structure to the foundation ditch bottom, guaranteed underground structure's stability and safety. In addition, the self-weight of the back pressure structure can be regulated and controlled by combining the regulation and control of the water level of the dewatering well, so that the vertical uplifting deformation value of the underground structure can be regulated and controlled by regulating the pressure applied to the bottom of the foundation pit. The back pressure structure is permanently arranged at the bottom of the foundation pit, and the back pressure structure does not need to be dismantled, so that resource waste is reduced.
Further, the backpressure structure comprises:
prefabricating a concrete block; the precast concrete blocks are arranged at the bottom of the foundation pit; and
pouring a raft foundation in situ; the cast-in-place raft foundation is connected with the precast concrete blocks into a whole.
The beneficial effects of the above further scheme are: the prefabricated concrete blocks are arranged at the bottom of the foundation pit and are connected with the prefabricated concrete blocks through the cast-in-place raft foundation to form an integrally formed back pressure structure, the prefabricated concrete blocks not only provide a construction operation surface for the construction of the cast-in-place raft foundation, but also limit the vertical upward lifting deformation of the underground structure in time by applying pressure to the bottom of the foundation pit through self weight of the prefabricated concrete blocks. The cast-in-place raft foundation and the precast concrete block are connected into a whole to form a back pressure structure which can be directly used as a bottom plate of a foundation pit, so that the construction efficiency of the foundation pit is greatly improved, and the construction flow of the foundation pit is simplified.
Further, cast-in-place raft foundation includes:
a transverse raft beam;
the longitudinal raft beam is connected with the transverse raft beam to form a horizontal frame structure; and
a raft plate;
the prefabricated concrete blocks are filled in the space formed between the transverse raft beam and the longitudinal raft beam, and the raft plates are formed by casting concrete on the top surfaces of the prefabricated concrete blocks in situ.
The beneficial effects of the further technical scheme are as follows: the horizontal displacement of the precast concrete blocks is limited by limiting the precast concrete blocks in a horizontal frame structure formed by connecting the transverse raft beams and the longitudinal raft beams, the vertical displacement of the precast concrete blocks is limited by casting the raft formed by the concrete on the top surface of the precast concrete blocks in situ, and the cast-in-situ raft foundation and the precast concrete blocks are connected into an integral structure.
Furthermore, there are a plurality of precast concrete pieces, and a plurality of precast concrete pieces are spliced into a concrete slab body.
The beneficial effects of the further technical scheme are as follows: the precast concrete blocks are arranged into a plurality of precast concrete blocks, the pressure applied to the upper soil body can be regulated and controlled according to the splicing number of the precast concrete blocks, and the influence on the structural stability of the soil body at the periphery of the underground structure due to the over-low water level of the dewatering well caused by the vertical upward lifting deformation value of the underground structure can be avoided.
Further, each precast concrete piece is provided with the anchor reinforcing bar, a plurality of precast concrete pieces pass through the anchor reinforcing bar is connected with the raft roof beam.
The beneficial effects of the above further scheme are: the precast concrete blocks and the raft beam are connected into a whole through the anchoring reinforcing steel bars, and the overall stability of the structure of the back pressure structure is improved.
Further, the method also comprises the step of reinforcing the peripheral soil body of the underground structure before the precipitation well is constructed.
The beneficial effects of the further scheme are as follows: by reinforcing the peripheral soil body of the underground structure, the stability of the peripheral soil body of the underground structure is ensured in the process of constructing the upper soil body of the underground structure.
The construction method has the beneficial effects that: the simulation precipitation depth value of a precipitation well and the simulation vertical upward deformation value of an underground structure which correspond to a plurality of unloading depths of the upper soil body unloading of the underground structure are simulated by utilizing finite element analysis software, the actual vertical upward deformation value of the underground structure detected in real time in the unloading process of the upper soil body of the underground structure is smaller than or equal to the simulation vertical upward deformation value by regulating and controlling the water level of the precipitation well, the integral stability and safety of the underground structure are ensured, the stress balance of the local area of the underground structure is ensured, the underground structure cannot deform beyond the standard, the local deformation is caused to break, and the problems that the structure cannot be operated and the like are influenced. The integral model of the upper soil body construction structure of the underground structure is established through finite element analysis software, and all construction processes of the construction structure are simulated, so that the comprehensive monitoring of the upper soil body construction process of the underground structure is realized, and the safety of the whole construction process is ensured. Simulating the simulated precipitation depth values of the precipitation well and the simulated vertical uplift deformation values of the underground structure corresponding to a plurality of unloading depths of the upper soil body of the underground structure by using finite element analysis software, so as to regulate and control the water level of the precipitation well according to different unloading depths, and enable the vertical uplift deformation values of the underground structure corresponding to different unloading depths to be always in an allowable range.
The invention also provides a system for constructing the soil body on the upper part of the underground structure, which comprises the following components:
the plurality of dewatering wells are arranged in the peripheral soil body of the underground structure;
a plurality of engineering piles arranged in the peripheral soil body of the underground structure;
the simulation analysis system is used for establishing an integral model of an upper soil body construction structure of the underground structure and simulating a simulated precipitation depth value of a precipitation well and a simulated vertical uplifting deformation value of the underground structure, wherein the simulated precipitation depth value and the simulated vertical uplifting deformation value correspond to a plurality of unloading depths of the upper soil body unloading of the underground structure respectively;
the field data monitoring system comprises a water level monitoring device and a displacement monitoring device, wherein the water level monitoring device is used for monitoring the water level height in the precipitation well to obtain the precipitation depth value of the precipitation well, and the displacement monitoring device is used for monitoring the vertical uplifting deformation of an underground structure to obtain the actual vertical uplifting deformation value of the underground structure; and
and the regulating and controlling system regulates and controls the water level of the dewatering well, so that the actual vertical uplifting deformation value acquired by the displacement monitoring device in real time in the unloading process of the upper soil body of the underground structure is smaller than or equal to the simulated vertical uplifting deformation value.
Further, the underground structure upper portion soil body construction system still includes:
the back pressure structure is permanently arranged at the bottom of a foundation pit formed after the upper soil body is unloaded, and the back pressure structure is connected with the tops of the engineering piles;
wherein, the back pressure structure includes precast concrete piece and cast-in-place raft foundation, the precast concrete piece set up in the bottom of foundation ditch, cast-in-place raft foundation with the precast concrete piece is connected as a whole.
The beneficial effects of the above further scheme are: through set up the back pressure structure in the bottom of foundation ditch, utilize the dead weight of back pressure structure to exert pressure in order to restrict the vertical upward deformation value of underground structure to the foundation ditch bottom, further guaranteed underground structure's stability and safety. In addition, the self weight of the back pressure structure can be regulated and controlled by combining the regulation and control of the water level of the dewatering well, so that the vertical uplifting deformation value of the underground structure can be regulated and controlled by regulating the pressure applied to the bottom of the foundation pit. The back pressure structure is permanently arranged at the bottom of the foundation pit, and the back pressure structure does not need to be dismantled, so that resource waste is reduced. The precast concrete piece not only provides the construction operation face for cast-in-place raft foundation's construction, but also restricts the vertical of underground structure to lift up and warp in time through its dead weight application pressure to the foundation ditch bottom. The cast-in-place raft foundation and the precast concrete block are connected into a whole, and the back pressure structure can be directly used as a bottom plate of a foundation pit, so that the construction efficiency of the foundation pit is greatly improved, and the construction flow of the foundation pit is simplified.
The soil body construction system on the upper part of the underground structure has the advantages that: the regulation and control system is combined with effective data acquired by the field data monitoring system and a simulated precipitation depth value and a simulated vertical upward lifting deformation value simulated by the simulation and analysis system, and the water level of the precipitation well is regulated and controlled in real time in the upper soil unloading process of the underground structure, so that the actual vertical upward lifting deformation value of the underground structure is smaller than or equal to the simulated vertical upward lifting deformation value, the vertical upward lifting deformation of the underground structure is always not more than a specified allowable range, and the stability and the safety of the underground structure are ensured.
Drawings
FIG. 1 is a schematic flow structure diagram of the method for constructing the upper soil body of the underground structure.
Fig. 2 is a schematic structural view of the principle of the soil construction system of the upper part of the underground structure of the present invention.
Fig. 3 is a schematic structural view of the soil construction system on the upper part of the underground structure before excavation of the foundation pit.
Fig. 4 is a schematic structural view of the soil construction system at the upper part of the underground structure after the foundation pit is excavated to the designed elevation.
Fig. 5 is a side view of the structure of fig. 4.
Fig. 6 is a schematic structural diagram of the distribution positions of the dewatering well and the engineering piles in fig. 3.
Fig. 7 is a schematic structural view of a plurality of precast concrete blocks of the soil construction system of the upper portion of the underground structure, which are spliced in a first concavo-convex fitting manner, according to the present invention.
Fig. 8 is an exploded perspective view illustrating a plurality of precast concrete blocks of fig. 7.
Fig. 9 is a schematic structural view of a plurality of precast concrete blocks of the soil construction system for an upper portion of an underground structure according to the present invention, which are spliced in a second concavo-convex coupling manner.
Fig. 10 is an exploded perspective view of a plurality of precast concrete blocks of fig. 9.
Fig. 11 is a schematic structural view of a plurality of precast concrete blocks of the soil construction system for an upper portion of an underground structure according to the present invention, which are spliced in a third concavo-convex coupling manner.
Fig. 12 is an exploded perspective view illustrating a plurality of precast concrete blocks of fig. 11.
In the figure; 1-a tunnel; 2, foundation pit; 3-engineering piles; 4-dewatering well; 4.1-Dredging well; 4.2-deep dewatering well; 5-soil body reinforcement structure; 6-cast-in-place raft foundation; 6.1-transverse raft beam; 6.2-longitudinal raft beam; 6.3-raft board; 7-precast concrete block, 7.1-L type concrete block, 7.2-Z type concrete block; 7.3-convex concrete blocks; 7.4-concave-convex concrete block; 7.5-concave concrete blocks; 7.6-T type concrete block; 7.7-anchoring the reinforcing steel bar; 8-a regulatory system; 9-water level monitoring device; 10-a displacement monitoring device; 11-a first soil mass; 12-a second soil mass; 13-simulation of the analysis system.
Detailed Description
The present invention is described in further detail below with reference to fig. 1 to 12 and specific examples.
The underground structure to which the system and the method for constructing the soil mass on the upper part of the underground structure are applicable is not limited to the form of a tunnel, and can also be applicable to underground structures of other forms, such as underground structures of subway stations, basements and the like.
The upper soil unloading mode applicable to the system and the method for constructing the upper soil of the underground structure is not limited to the excavation mode of the foundation pit 2, and can be other soil unloading modes, for example, the upper soil of the underground structure is unloaded by drilling.
As shown in fig. 3, the underground structure in this embodiment is exemplified by a bidirectional tunnel, and the upper soil unloading construction is exemplified by performing soil excavation construction on the upper soil and forming a foundation pit 2 in the upper soil. The upper soil body comprises a first soil body 11 and a second soil body 12, the first soil body 11 is arranged above the second soil body 12, the first soil body 11 is the soil body from the top of the foundation pit 2 to the bottom of the foundation pit 2 before the foundation pit 2 is excavated, namely the depth of the first soil body 11 is equal to the depth of the foundation pit 2, and the second soil body 12 is the soil body from the bottom of the foundation pit 2 to an underground structure, so that the unloading of the upper soil body is the unloading of the second soil body 12 caused by the excavation of the first soil body 11.
When the excavation operation of the foundation pit 2 needs to be performed on the first soil body 11 above the tunnel 1, in order to ensure the structural stability and the safety of the tunnel 1, the construction system and the construction method of the embodiment are used to reduce the influence on the tunnel 1 and the second soil body 12.
The soil body construction system on the upper part of the underground structure as shown in fig. 2 to 5 comprises a plurality of precipitation wells 4, a plurality of engineering piles 3, a simulation analysis system 13, a field data monitoring system, a regulation and control system and a counter-pressure structure.
The simulation analysis system 13 comprises a computer and finite element analysis software arranged in the computer, establishes an integral model of a soil construction structure on the upper part of the underground structure by using the finite element analysis software, and simulates all construction processes of the construction structure, wherein the construction processes comprise construction of the engineering piles 3, excavation construction of the foundation pit 2 in a subarea layer-by-layer manner and precipitation construction of a plurality of precipitation wells 4. The simulation analysis system 13 simulates simulated precipitation depth values of the precipitation well 4 and simulated vertical uplift deformation values of the tunnel 1, which correspond to a plurality of unloading depths of the second soil body 12 by using finite element analysis software.
The counter pressure structure comprises a plurality of precast concrete blocks 7 and a cast-in-place raft foundation 6. The back pressure structure is permanently arranged at the bottom of the foundation pit 2 formed after the second soil body 12 is unloaded, is connected with the tops of the engineering piles 3 and is used for applying pressure to the second soil body 12 to regulate and control the vertical uplift deformation value of the tunnel 1 in the unloading process of the second soil body 12.
Referring to fig. 3 and 6, a plurality of dewatering wells 4 are arranged at intervals in the soil around the tunnel 1. Each dewatering well 4 comprises a dewatering well 4.1 and a deep dewatering well 4.2. A plurality of engineering piles 3 are erected in the peripheral earth of the tunnel 1. And after the foundation pit 2 is excavated to the designed elevation of the foundation pit 2, chiseling off the pile head of each engineering pile 3 to enable the pile head to be connected with the cast-in-situ raft foundation 6 into a whole. As shown in fig. 6, a plurality of dewatering wells 4 are provided along the longitudinal direction of the tunnel 1, and a plurality of construction piles 3 are provided along the longitudinal direction of the tunnel 1. In this embodiment, there are two tunnels 1, and a precipitation well 4 and an engineering pile 3 are correspondingly arranged in the soil body between the two tunnels 1. It can be understood that when there are two tunnels 1, the construction piles 3 may not be arranged in the soil body between the two tunnels 1, and the dewatering wells 4 may be arranged only in the soil body between the two tunnels 1.
As shown in fig. 3, the soil body construction system at the upper part of the underground structure further comprises a soil body reinforcing structure 5 arranged in the peripheral soil of the tunnel 1; the soil body reinforcing structure 5 comprises a high-pressure jet grouting pile or an MJS grouting pile. Since the tunnel 1 of this embodiment is a subway tunnel as an example, the soil body reinforcing structure 5 should be arranged outside the disturbance range of the subway tunnel, and this embodiment is preferably 3 meters, that is, the soil body reinforcing structure 5 is arranged in the peripheral soil body 3 meters away from the outside of the subway tunnel structure.
As shown in fig. 4 and 5, the cast-in-place raft foundation 6 comprises transverse raft beams 6.1, longitudinal raft beams 6.2 and rafts 6.3. The transverse raft beam 6.1 and the longitudinal raft beam 6.2 are both arranged at the bottom of the foundation pit 2, the transverse raft beam 6.1 and the longitudinal raft beam 6.2 are perpendicular to each other or are connected at other angles to form a horizontal frame structure, and concrete is poured into the horizontal frame structure to form a raft 6.3. A plurality of precast concrete blocks 7 are filled in the horizontal frame structure, and each precast concrete block 7 is internally provided with an anchoring reinforcing steel bar 7.7, and at least part of the anchoring reinforcing steel bars 7.7 extend out of the precast concrete blocks 7 to be used for being connected with a cast-in-place raft foundation 6. The side end of the precast concrete piece 7 in this embodiment is provided with a protruding anchoring rebar 7.7, and this anchoring rebar 7.7 is used for being connected with the raft beam of the cast-in-place raft foundation 6, i.e. the transverse raft beam 6.1 and the longitudinal raft beam 6.2. In order to improve the connection strength between the cast-in-place raft foundation 6 and the precast concrete block 7, the anchoring steel bars 7.7 can also be arranged at the top end of the precast concrete block 7 and used for being connected with the raft 6.3. Cast-in-place raft foundation 6, engineering pile 3 are connected with precast concrete piece 7 and are overall structure, and this overall structure not only can restrict second soil body 12 come-up in tunnel 1 and regulate and control the vertical upward deformation value of tunnel 1 of 12 off-load in-process of second soil body, can restrict second soil body 12 moreover and to peripheral diffusion, and then guarantee tunnel 1's stability and security.
A plurality of precast concrete blocks 7 are spliced into a concrete plate body; the concrete plate body is connected with the cast-in-place raft foundation 6 into a whole. At least two of the precast concrete blocks 7 are concavo-convex fitted to form a concrete panel body. Or at least one end surface of the precast concrete blocks 7 is provided with a tongue-and-groove, and the precast concrete blocks 7 are spliced by the tongue-and-groove to form a concrete plate body. The precast concrete block 7 may be added with steel chips or iron sand to raise the counterweight.
There are various types of the form of fitting of the precast concrete segment 7, and in this embodiment, three types of the form of fitting of the precast concrete segment 7 are listed but not limited to the listed three types.
Specifically, as shown in fig. 7 and 8, the first concavo-convex matching type precast concrete segment 7 includes an L-shaped concrete segment 7.1 and a Z-shaped concrete segment 7.2 which are spliced together. The corresponding quantity of the L-shaped concrete blocks 7.1 and the Z-shaped concrete blocks 7.2 can be selected according to the width of the foundation pit 2 and the pressure required by the vertical uplifting deformation of the limited tunnel 1, and the plurality of L-shaped concrete blocks 7.1 and the plurality of Z-shaped concrete blocks 7.2 are spliced in the horizontal direction to form a whole concrete plate body.
As shown in fig. 9 and 10, the precast concrete block 7 of the second male-female mating form includes a male concrete block 7.3 and a female concrete block 7.5 which are spliced with each other. The concrete plate can also comprise a plurality of concave-convex concrete blocks 7.4, the structure of the concave-convex concrete blocks 7.4 is the same as or similar to the structure of the convex concrete blocks 7.3 and the concave concrete blocks 7.5 after being spliced, when the concave-convex concrete blocks 7.4 are arranged, the concave-convex concrete blocks are spliced to form a middle plate body, and the convex concrete blocks 7.3 and the concave concrete blocks 7.5 are respectively spliced on two sides of the middle plate body to form a whole concrete plate body.
As shown in fig. 11 and 12, the third form of pre-cast concrete block 7 comprises a plurality of rebated T-shaped blocks 7.6. The tongue-and-groove of a plurality of T-shaped concrete blocks 7.6 are spliced to form an integral concrete plate body.
The precast concrete blocks 7 may also be in other shapes, and during specific construction, the precast concrete blocks 7 in appropriate shapes and numbers may be reasonably selected for splicing. The precast concrete blocks 7 can be hoisted into the foundation pit 2 after being precast in advance.
The field data monitoring system comprises a water level monitoring device 9 and a displacement monitoring device 10, wherein the water level monitoring device 9 is arranged in the precipitation well 4 or above the precipitation well 4 and is used for monitoring the water level height in the precipitation well 4 so as to obtain the precipitation depth value of the precipitation well 4, and the water level monitoring system can be an existing water level monitoring sensor. The displacement monitoring device 10 is used for monitoring the vertical uplift deformation amount of the tunnel 1 so as to obtain an actual vertical uplift deformation value of the tunnel 1. The displacement monitoring device 10 may be a displacement sensor, which may be disposed at the upper end of the tunnel 1 and configured to monitor the vertical uplift deformation of the tunnel 1 to obtain the actual vertical uplift deformation value of the tunnel 1, and the displacement monitoring device 10 may also be an underground pipeline detector disposed above the first soil body 11 and configured to detect the vertical uplift deformation of the tunnel 1. The present embodiment does not specifically limit the installation position and the structural form of the displacement monitoring device 10.
The regulating and controlling system 8 is in electric signal connection with the displacement monitoring device 10 and in electric signal connection with the water level monitoring device 9, and the regulating and controlling system 8 regulates and controls the height of the water level in the dewatering well 4, so that the actual vertical uplift deformation value of the tunnel 1, which is acquired in real time by the displacement monitoring device 10 in the unloading process of the second soil body 12, is smaller than or equal to the simulated vertical uplift deformation value of the simulated analysis system 13.
The regulation and control system 8 at least comprises a terminal console (such as a computer), a controller, a water pump and a water pipe communicated with the water pump, and the water pump is arranged in the dewatering well 4.
As shown in fig. 2, the simulation analysis system 13 uses finite element analysis software to build an integral model of the upper soil construction structure of the tunnel 1 and simulate all the construction processes of the construction structure, including construction of the engineering piles 3, excavation of the foundation pit 2 by zones and layer by layer, and precipitation of a plurality of precipitation wells 4. The simulation analysis system 13 simulates the simulated precipitation depth value of the precipitation well 4 and the simulated vertical uplift deformation value of the underground structure corresponding to a plurality of unloading depths of the second soil body 12 by using the finite element analysis software according to all construction processes simulated by the finite element analysis software. In the unloading process of the second soil body 12, the displacement monitoring device 10 monitors the vertical uplift deformation of the tunnel 1 in real time to obtain the actual vertical uplift deformation value of the tunnel 1. The regulating and controlling system 8 compares the actual vertical uplift deformation value with the simulated vertical uplift deformation value, and when the actual vertical uplift deformation value is larger than the simulated vertical uplift deformation value, the regulating and controlling system 8 regulates and controls the water level of the dewatering well 4, so that the actual vertical uplift deformation value acquired by the displacement monitoring device 10 in real time in the unloading process of the second soil body 12 is smaller than or equal to the simulated vertical uplift deformation value. The regulation and control system 8 can also compare the simulated precipitation depth value with the real precipitation depth value of the precipitation well 4 obtained by the water level monitoring device 9 in real time to verify whether the water level of the precipitation well 4 regulated and controlled by the regulation and control system 8 is reasonable.
During the excavation of the foundation pit 2, the field data monitoring system and the regulating and controlling system 8 are always in a working state, that is, the adjustment of the water level height in the precipitation well 4 is not started after the excavation of the foundation pit 2 is finished, but can run through the whole excavation process of the foundation pit 2 or be called as the whole unloading process running through the second soil body 12.
The method for constructing the soil body above the underground structure as shown in fig. 1 comprises the following steps:
And 5, performing soil excavation construction of a certain unloading depth in a certain area of the foundation pit 2, detecting the actual vertical uplifting deformation value of the tunnel 1 in real time, and when the actual vertical uplifting deformation value of the tunnel 1 is larger than the simulated vertical uplifting deformation value of the tunnel 1, regulating and controlling the water level of the dewatering well 4 by a regulating and controlling system, so that the actual vertical uplifting deformation value of the tunnel 1 detected by the displacement monitoring device 10 in real time is smaller than or equal to the simulated vertical uplifting deformation value of the tunnel 1.
And 6, repeatedly executing the step 5, excavating the soil body at the next unloading depth of the foundation pit 2 in the area, continuously regulating and controlling the water level of the dewatering well 4 by the regulating and controlling system, so that the actual vertical lifting deformation value of the tunnel 1 detected in real time in the excavation process of the foundation pit 2 is smaller than or equal to the simulated vertical lifting deformation value of the tunnel 1 until the foundation pit 2 in the area is excavated to the designed elevation, and repeatedly executing the step 5 to excavate the soil body of the foundation pit 2 in the next area until the soil body excavation construction of all areas of the foundation pit 2 is completed.
In the above steps, the regulation and control system regulatesThe water level of the dewatering control well 4 is controlled according to the formula F Floating body =F Descend +2 F Resistance device +F Resist against The adjustment is carried out, so that the water level reduction height delta h in the adjusted dewatering well 4 meets the formula:
in the formula, F Floating body The floating force F for unloading the second soil body 12 Descend The sedimentation force, F, to which the second soil body 12 is subjected for the precipitation of the precipitation well 4 Resistance device Frictional resistance to the tunnel 1 floating upward, F Is resistant to The tunnel 1 is provided with deformation resistance against deformation due to its own rigidity under the influence of the floating force.
Wherein the floating force F Floating body The calculation formula of (c) is: f Floating body =γ Soil for soil h Unloading l Digging machine D，
Settling force F Descend The calculation formula of (c) is: f Descend =αγ Water (I) Δhl Digging machine D，
Frictional resistance F Resistance device The calculation formula of (c) is: f Resistance device =βKγ Soil for planting h Buried in l Digging machine D，
Resistance to deformation F Resist against The calculation formula of (c) is: f Is resistant to =（384ηEIs）/5l Digging tool 3 ，
In the above formula: gamma ray Soil for soil The second soil mass 12 has a heavy weight (kN/m) 3 ），h Unloading The unloading depth (m) of the second soil body 12,l digging machine Is the unloading length (m) of the second soil body 12) or the length (m) of the sectional excavation of the foundation pit 2, D is the diameter (m) of the tunnel 1, alpha is an adjusting coefficient, and gamma is Water (W) Is the water weight (kN/m) in the soil surrounding the tunnel 1 3 ) Delta h is the water level lowering height (m) in the dewatering well 4, beta is the regulating coefficient, K is the friction angle coefficient, h Is buried in Is the buried depth (m) of the tunnel 1, and EI is the longitudinal stiffness (kN m) of the tunnel 1 2 ) Eta is the effective rate of rigidity, and s is the vertical uplift deformation value (mm) of the tunnel 1 in the unloading length (or called the excavation length of the foundation pit 2) of the second soil body 12.
Taking the diameter of the tunnel 1 as 6m and the buried depth of the tunnel 1 as 12m as an example, the relationship between the precipitation depth of the precipitation well 4 of the foundation pit 2 at different excavation depths and the maximum vertical uplift deformation value s of the tunnel 1 and each force in the formula is as follows:
in the example of the above formula, γ Soil for planting The value is 22 kN/m 3 ，γ Water (W) The value is 9.8 kN/m 3 The value of the adjustment coefficient alpha is 0.6, the value of the adjustment coefficient beta is 0.05, the value of the friction angle coefficient K is 0.25, and the value of the rigidity EI of the tunnel 1 is 1.235 multiplied by 10 7 The effective coefficient of stiffness is 1/8. The rainfall depth needs to be controlled in the excavation process of the second soil body 12, and the maximum vertical uplift deformation value of the tunnel 1 is guaranteed not to exceed the maximum allowable vertical uplift deformation value 10mm required by the specification.
As can be seen from the above table, the frictional resistance F is removed as the excavation depth of the foundation pit 2 increases Resistance device Constant external and upward floating force F Floating body Settling force F Descend And deformation resistance F Is resistant to The vertical uplift deformation value of the tunnel 1 is increased continuously, and in order to regulate the vertical uplift deformation value of the tunnel 1 to be within an allowable range, the regulation system needs to regulate the precipitation depth of the precipitation well 4 to be increased along with the excavation depth of the foundation pit 2. Establishing a relation between a theoretical precipitation water level and the vertical uplift deformation of the tunnel 1 according to a finite element simulation analysis and adjustment control formula, wherein a part of the relation is shown in the table above, and the adjustment and control system 8 is used for pre-controlling the precipitation depth of the precipitation well 4 according to different excavation depths of the foundation pit 2; in the actual excavation process, if the excavation depth is in a stage of 2-3 m, the precipitation depth is 4m in advance, the actual vertical uplifting deformation amount of the tunnel 1 is monitored, and if the actual vertical uplifting deformation value of the tunnel 1 is smaller than 2.4mm, the precipitation depth is stabilized and excavation is continued; if the actual vertical uplift deformation value of the tunnel 1 in the excavation process reaches 2.4mm, feeding back to a regulation and control system 8 according to monitoring data, automatically and gradually increasing the precipitation depth, regulating and controlling balance, and controlling the vertical uplift deformation of the tunnel 1; the layered excavation is automatically regulated and controlled, and the vertical uplift deformation of the tunnel 1 in the actual excavation process is ensured to be less than or equal to the theoretical deformation (namely the simulation vertical uplift deformation)Form and value) and meets specification and design requirements.
And 7, constructing a back pressure structure at the bottom of the foundation pit 2: the method comprises the steps of breaking the pile head of the engineering pile 3, adjusting the steel bars exposed out of the top of the engineering pile 3, laying a plurality of precast concrete blocks 7 at the bottom of the foundation pit 2, splicing the adjacent precast concrete blocks 7 through grooves and tongues to form a concrete plate body, and adjusting the vertical lifting deformation value of the tunnel 1 and providing a construction operation surface for subsequent construction.
The upper end of the precast concrete block 7 is used as a construction operation surface of the cast-in-place raft foundation 6, and a template and reinforcing steel bars for pouring construction of the cast-in-place raft foundation 6 are erected at the bottom of the foundation pit 2.
Pouring concrete to the inner side of the template, and enabling the poured concrete to surround the pile head of the engineering pile 3 and the precast concrete block 7 to form a cast-in-place raft foundation 6; wherein, the precast concrete blocks 7 are connected with the cast-in-place raft foundation 6 through the cast concrete to form a whole counter pressure structure. The back pressure structure is permanently arranged at the bottom of the foundation pit 2, the cast concrete of the cast-in-place raft foundation 6 is connected with the top of the engineering pile 3, and the back pressure structure formed by the cast-in-place raft foundation 6 after solidification and the precast concrete 7 is connected with the engineering pile 3.
The cast-in-situ raft foundation 6 comprises a transverse raft beam 6.1, a longitudinal raft beam 6.2 and a raft 6.3, wherein the transverse raft beam 6 is connected with the longitudinal raft beam 6.2 to form a horizontal frame structure. The precast concrete blocks 7 are filled in the spaces formed between the transverse raft beams and the longitudinal raft beams, and the raft plates 6.3 are formed by casting concrete on top of the precast concrete blocks 7 in situ. In order to improve the connection strength of the precast concrete blocks 7 and the cast-in-place raft foundation 6, each precast concrete block 7 is provided with an anchoring steel bar 7.7, and the precast concrete blocks 7 are connected with raft beams through the anchoring steel bars 7.7, wherein the raft beams comprise transverse raft beams 6.1 and longitudinal raft beams 6.2.
The above is only a preferred embodiment of the present invention, and the protection scope of the present invention is not limited to the above-mentioned embodiments, and all technical solutions belonging to the idea of the present invention belong to the protection scope of the present invention. It should be noted that modifications and embellishments within the scope of the invention may be made by those skilled in the art without departing from the principle of the invention.
Claims (7)
1. A construction method of an upper soil body of an underground structure is characterized by comprising the following steps:
establishing an integral model of a soil construction structure on the upper part of an underground structure by using finite element analysis software, and simulating all construction processes of the construction structure, wherein the construction processes comprise engineering pile construction, foundation pit partition layer-by-layer excavation construction and precipitation construction of a plurality of precipitation wells;
simulating simulated precipitation depth values of precipitation wells and simulated vertical uplift deformation values of the underground structure, which correspond to a plurality of unloading depths of unloading of an upper soil body of the underground structure respectively, by using the finite element analysis software according to all construction processes simulated by the finite element analysis software;
carrying out engineering pile construction on peripheral soil bodies of the underground structure;
carrying out precipitation well construction in the peripheral soil body of the underground structure, and setting the precipitation depth value of the precipitation well as a simulated precipitation depth value corresponding to the unloading depth;
unloading the upper soil body, detecting an actual vertical uplifting deformation value of the underground structure in real time, and regulating and controlling the water level of the dewatering well when the actual vertical uplifting deformation value is larger than the simulated vertical uplifting deformation value, so that the actual vertical uplifting deformation value detected in real time is smaller than or equal to the simulated vertical uplifting deformation value;
repeatedly executing the previous step, excavating the soil body at the next unloading depth, and regulating the water level of the dewatering well to ensure that the actual vertical lifting deformation values detected in real time in the excavation process are all smaller than or equal to the simulated vertical lifting deformation values until the unloading construction of the upper soil body of the underground structure is completed;
the water level of the dewatering well is regulated and controlled according to a formula F Floating body =F Descend +2 F Resistance device +F Resist against Adjusting to enable the adjusted water level reduction height delta h in the precipitation well to meet the formula:
in the formula, F Floating body A floating force F acting on the upper soil body for unloading Lower the main body Subjecting the upper soil body to precipitation for the precipitation wellSettling force of (F) Resistance device Is the frictional resistance to the upward flotation of the underground structure, F Resist against Deformation resistance to deformation of the underground structure due to its own stiffness under the influence of uplift forces;
wherein the floating force F Floating body The calculation formula of (2) is as follows: f Floating body =γ Soil for planting h Unloading l Digging machine D，
Said settling force F Descend The calculation formula of (2) is as follows: f Lower the main body =αγ Water (W) Δhl Digging machine D，
The frictional resistance F Resistance block The calculation formula of (2) is as follows: f Resistance device =βKγ Soil for soil h Buried in l Digging machine D，
Said deformation resistance F Resist against The calculation formula of (2) is as follows: f Resist against =（384ηEIs）/5l Digging machine 3 ，
In the above formula: gamma ray Soil for planting Is the weight (kN/m) of the upper soil body 3 ），h Unloading The unloading depth (m) of the upper soil body,l digging tool The unloading length (m) of the upper soil body, D the diameter (m) of the underground structure, alpha the regulating coefficient, gamma Water (I) Is the water weight (kN/m) in the surrounding soil of the underground structure 3 ) Delta h is the water level reduction height (m) in the precipitation well, beta is the coefficient of regulation, K is the coefficient of friction angle, h Is buried in Is the buried depth (m) of the underground structure, and EI is the longitudinal stiffness (kN m) of the underground structure 2 ) And eta is the effective stiffness rate, and s is the vertical uplift deformation value (mm) of the underground structure in the unloading length of the upper soil body.
2. The construction method according to claim 1, further comprising a construction step of a back pressure structure after the unloading construction of the upper soil body of the underground structure is completed, wherein the back pressure structure is permanently disposed at the bottom of a foundation pit formed after the unloading of the upper soil body, and the back pressure structure is connected to the tops of the plurality of engineering piles.
3. The construction method according to claim 2, wherein the back pressure structure comprises:
prefabricating a concrete block; the precast concrete blocks are arranged at the bottom of the foundation pit; and
pouring a raft foundation in situ; the cast-in-place raft foundation is connected with the precast concrete blocks into a whole.
4. A construction method as claimed in claim 3, wherein the cast-in-situ raft foundation comprises:
a transverse raft beam;
the longitudinal raft beam is connected with the transverse raft beam to form a horizontal frame structure; and
a raft plate;
the prefabricated concrete blocks are filled in the space formed between the transverse raft beam and the longitudinal raft beam, and the raft plates are formed by casting concrete on the top surfaces of the prefabricated concrete blocks in situ.
5. The construction method according to claim 4, wherein the precast concrete block is provided in plurality, and the precast concrete blocks are joined together to form a concrete slab.
6. The construction method according to claim 5, wherein each of the precast concrete blocks is provided with an anchoring reinforcement, and a plurality of the precast concrete blocks are connected to the raft beams through the anchoring reinforcement.
7. The construction method according to claim 1, further comprising the step of reinforcing the soil around the underground structure before the dewatering well is constructed.
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