Method for calculating deformation increment of flash descending type servo support foundation pit support structure

Abstract

The invention relates to the technical field of foundation pit deformation calculation, in particular to a flash drop type servo support foundation pit support structure deformation increment calculation method which comprises the following steps: establishing a foundation pit model; simulating excavation of a first layer of earthwork, pouring a first concrete support, and performing first calculation; s3, simulating excavation of a next layer of earthwork, and applying jacking force by using a flash descending type servo support; s4, the applied jacking force is used as an incremental load, and the incremental load and the existing deformation of the foundation pit support structure are superposed into a calculation result of the first calculation; s5, a concrete support or a floor slab is poured; s6, the flash descending type servo support is dismantled, and the dismantled support serves as an incremental load to be superposed with existing deformation of the foundation pit support structure into the calculation result of the step S4; and S6, judging whether the last layer of earth is excavated or not, if so, ending the operation, and if not, repeating the steps S3 to S6. According to the method, the deformation and the internal force of the enclosure structure in each construction stage are accurately calculated, and reliable guidance is provided for early-stage design of the foundation pit enclosure structure.

Description

Technical Field

[0001] The invention relates to the technical field of foundation pit deformation calculation, and in particular to a method for calculating the deformation increment of a flash-down servo-supported foundation pit retaining structure. Background Art

[0002] The flash-down servo steel support is a new deep foundation pit construction process. After the foundation pit is excavated, temporary pre-support is quickly set up in a short period of time with the help of a vertical sliding module, and the pre-support force is applied to the retaining wall through the hydraulic jack servo module. Finally, concrete support is quickly poured on the pre-support, which effectively controls the deformation of the support structure by greatly shortening the exposure time of the foundation pit. During the design process, traditional design methods face some challenges. This is because when the retaining structure is actively supported by the servo support, its force and deformation are different from those when the traditional support is passively supported. The design calculation of the servo support active support usually lacks a reasonable method, and the analysis of the active support effect is usually not in-depth enough. Summary of the invention

[0003] The purpose of the present invention is to overcome the defects of the prior art and provide a method for calculating the deformation increment of a flash-down servo-supported foundation pit retaining structure, so as to solve the problems that the design and calculation of the existing servo-supported active support lack a reasonable method and the analysis of the active support effect is usually not in-depth enough.

[0004] The technical solution to achieve the above purpose is: The present invention provides a method for calculating the deformation increment of a flash-down servo-supported foundation pit retaining structure, comprising the following steps: S1: Establish a foundation pit model according to the project conditions, and set the number of earth excavation layers for the established foundation pit model; S2: simulate the excavation of the first layer of earthwork, simulate the pouring of the first concrete support in the foundation pit model, and perform the first calculation of the deformation of the foundation pit retaining structure; S3: simulate the excavation of the next layer of earthwork, simulate the lowering of temporary supporting purlins in the foundation pit model, and use the flash-down servo support to apply the top force according to the design value; S4: applying a top force according to the design value of the flash-down servo support to the foundation pit retaining structure as the first incremental load, and superimposing the first incremental load and the existing deformation of the foundation pit retaining structure when the flash-down servo support is installed to the calculation result of the first calculation; S5: Simulate pouring concrete support or floor slab on the top surface of the flash-down servo support in the foundation pit model; S6: dismantle the temporary supporting purlin and the flash-down servo support, regard the reaction force of the support force of the dismantled flash-down servo support as the second incremental load acting on the foundation pit retaining structure, and superimpose the second incremental load and the existing deformation of the foundation pit retaining structure when the flash-down servo support is dismantled to the calculation result of step S4; S7: Determine whether it is the last layer of earth excavation. If so, end the operation and output the calculation results of the above steps. If not, repeat steps S3 to S6.

[0005] The further improvement of the method for calculating the deformation increment of the flash-down servo-supported foundation pit retaining structure of the present invention is that the first calculation of the deformation of the foundation pit retaining structure in step S2 includes: Adding the load increment caused by excavating the first layer of earthwork into the foundation pit model, wherein the load increment caused by excavating the first layer of earthwork includes the reduction of static upper pressure on the foundation pit side caused by excavation and the release of elastic resistance of the soil in the excavated soil; The equilibrium equation of the enclosure structure for the first calculation is: Equation 1, In equation 1, is the non-limit earth pressure matrix of the soil outside the pit, is the wall stiffness matrix, is the soil spring stiffness matrix, is the deformation matrix of the underground continuous wall, is the support stiffness matrix.

[0006] The further improvement of the deformation increment calculation method of the flash-drop servo support foundation pit retaining structure of the present invention is that in step S4, the first incremental load and the existing deformation of the foundation pit retaining structure when the flash-drop servo support is installed are superimposed on the calculation result of the first calculation, and the equilibrium equation of the retaining structure is obtained as follows: Equation 2, In equation 2, is the non-limit earth pressure matrix of the soil outside the pit, is the wall stiffness matrix, is the soil spring stiffness matrix, is the deformation matrix of the underground continuous wall, is the support stiffness matrix, When the flash-down servo support is installed, the foundation pit retaining structure has a deformation matrix. is the concentration matrix.

[0007] A further improvement of the method for calculating the deformation increment of the flash-down servo-supported foundation pit retaining structure of the present invention is that the support stiffness matrix includes the flash-down servo support stiffness.

[0008] A further improvement of the method for calculating the deformation increment of the flash-down servo support foundation pit retaining structure of the present invention is that the concentrated force matrix includes the top force applied by the flash-down servo support.

[0009] The further improvement of the deformation increment calculation method of the flash-drop servo support foundation pit retaining structure of the present invention is that in step S6, the second incremental load and the existing deformation of the foundation pit retaining structure when the flash-drop servo support is removed are superimposed on the calculation result of step S4, and the equilibrium equation of the retaining structure is obtained as follows: Equation 3, In equation 3, is the non-limit earth pressure matrix of the soil outside the pit, is the wall stiffness matrix, is the soil spring stiffness matrix, is the deformation matrix of the underground continuous wall, is the support stiffness matrix, When the flash-down servo support is removed, the foundation pit retaining structure has a deformation matrix. is the reaction force matrix.

[0010] A further improvement of the method for calculating the deformation increment of the flash-down servo-supported foundation pit retaining structure of the present invention is that the support stiffness matrix in step S6 includes the support stiffness of the concrete support or floor slab in step S5.

[0011] A further improvement of the method for calculating the deformation increment of the flash-drop servo-supported foundation pit retaining structure of the present invention is that the reaction force matrix includes the reaction force of the support force of the removed flash-drop servo support.

[0012] The beneficial effects of the deformation increment calculation method of the flash-down servo-supported foundation pit retaining structure of the present invention are: The present invention can take into account the active support effect of the flash-down servo support in each excavation stage, and use the incremental method to regard the process of applying active support as adding an incremental load acting on the retaining structure for calculation, thereby basically simulating the entire process of foundation pit excavation and accurately calculating the deformation and internal force of the retaining structure in each construction stage, providing reliable guidance for the early design of the foundation pit retaining structure.

[0013] The present invention truly simulates the entire process of foundation pit excavation and accurately calculates the deformation and internal force of the retaining structure at each stage of construction, thereby more truly reflecting the control effect of the flash-down servo steel support on the deformation of the deep foundation pit retaining structure and improving the reliability of the retaining structure design. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 The present invention is a flow chart of the method for calculating the deformation increment of the flash-down servo-supported foundation pit retaining structure.

[0015] Figure 2 The present invention provides a schematic diagram of an active support process added to the deformation increment calculation method of the flash-down servo-supported foundation pit retaining structure.

[0016] Figure 3 The present invention provides a simplified diagram of incremental calculation corresponding to the active support process in the incremental calculation method for deformation of the flash-down servo-supported foundation pit retaining structure.

[0017] Figure 4 It is a schematic diagram of the process of removing active support in the deformation increment calculation method of the flash-down servo-supported foundation pit retaining structure of the present invention.

[0018] Figure 5 It is a simplified diagram of the incremental calculation corresponding to the process of removing the active support in the incremental calculation method of deformation of the flash-down servo-supported foundation pit retaining structure of the present invention.

[0019] Explanation of the accompanying drawings: 1- foundation pit retaining structure; 2- flash-drop servo support; 3- flash-drop servo support equivalent spring; 4- equivalent soil spring of soil in the pit; 5- cast concrete support or floor slab; 6- cast concrete support or floor slab equivalent spring. DETAILED DESCRIPTION

[0020] The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments.

[0021] See also Figure 1 The present invention provides a method for calculating the incremental deformation of a flash-down servo-supported foundation pit retaining structure. To solve the problem that the traditional calculation method cannot accurately calculate the deformation of the foundation pit retaining structure under the action of the flash-down servo support, the present invention uses the incremental method in the calculation process, and regards the process of applying active support as adding an incremental load to the foundation pit retaining structure to participate in the calculation, truly simulating the entire process of foundation pit excavation, and accurately calculating the deformation and internal force of the retaining structure at each stage of construction, providing reliable guidance for the early design of the foundation pit retaining structure. The incremental calculation method for the deformation of the flash-down servo-supported foundation pit retaining structure of the present invention is described below in conjunction with the accompanying drawings.

[0022] See also Figure 1 , showing a flow chart of the method for calculating the deformation increment of the flash-down servo-supported foundation pit retaining structure of the present invention. Figure 1 , the deformation increment calculation method of the flash-down servo-supported foundation pit retaining structure of the present invention is explained.

[0023] like Figure 1 As shown, the deformation increment calculation method of the flash-down servo-supported foundation pit retaining structure of the present invention comprises the following steps: Execute step S1: establish a foundation pit model according to the engineering situation, and set the number of earthwork excavation layers for the established foundation pit model; the engineering situation includes basic engineering information such as the excavation depth of the foundation pit, the design parameters of the retaining structure, and the soil layer parameters, and establish the foundation pit model based on the above information; then execute step S2; Execute step S2: simulate the excavation of the first layer of earthwork, simulate the pouring of the first concrete support in the foundation pit model, and perform the first calculation of the deformation of the foundation pit retaining structure; then execute step S3; Execute step S3: simulate excavation of the next layer of earthwork, simulate lowering of temporary supporting purlins in the foundation pit model, and use the flash-down servo support to apply the top force according to the design value; then execute step S4; Execute step S4: apply a top force according to the design value of the flash-down servo support to the foundation pit retaining structure as the first incremental load, and superimpose the first incremental load and the existing deformation of the foundation pit retaining structure when the flash-down servo support is installed to the calculation result of the first calculation; then execute step S5; Execute step S5: simulate pouring concrete support or floor slab on the top surface of the flash-down servo support in the foundation pit model; then execute step S6; Execute step S6: remove the temporary supporting purlin and the flash-down servo support, regard the reaction force of the support force of the removed flash-down servo support as the second incremental load acting on the foundation pit retaining structure, and superimpose the second incremental load and the existing deformation of the foundation pit retaining structure when the flash-down servo support is removed to the calculation result of step S4; then execute step S7; Execute step S7: determine whether it is the last layer of earth excavation. If so, end the operation and output the calculation results of the above steps. If not, repeat steps S3 to S6.

[0024] In a specific implementation of the present invention, the first calculation of the deformation of the foundation pit retaining structure in step S2 includes: The load increment caused by excavating the first layer of earthwork is added to the foundation pit model. The load increment caused by excavating the first layer of earthwork includes the reduction of static upper pressure on the foundation pit side caused by excavation and the release of elastic resistance of the soil in the excavated soil. The equilibrium equation of the enclosure structure for the first calculation is: Equation 1, In equation 1, is the non-limit earth pressure matrix of the soil outside the pit, is the wall stiffness matrix, is the soil spring stiffness matrix, is the deformation matrix of the underground continuous wall, is the support stiffness matrix.

[0025] After the first excavation, the load increment is the soil pressure increment, which consists of two parts: the first part is the reduction of the static soil pressure on the side of the foundation pit caused by excavation, which is equivalent to the reduction of this pressure applied to the system in the reverse direction at the part where the soil is excavated; the second part is the release of the elastic resistance of the soil in the excavated soil (including horizontal and tangential soil elastic resistance), which is equivalent to applying these soil elastic resistances to the system in the reverse direction at the excavation site. Add the above load increment to the model and complete the first calculation.

[0026] Further, in step S3, if Figure 2 As shown, the foundation pit is excavated to a specified depth, and temporary supporting purlins are assembled in the excavated foundation pit. Then, the flash-down servo support 2 is pushed outward to apply a top force to the foundation pit retaining structure 1 (such as an underground continuous wall) according to the design value, so that the temporary supporting purlins apply prestressed support to the foundation pit retaining structure 1.

[0027] In a specific embodiment of the present invention, the first incremental load in step S4 and the deformation of the foundation pit retaining structure when the flash-down servo support is installed are added to the calculation result of the first calculation, and the equilibrium equation of the retaining structure is obtained as follows: Equation 2, In equation 2, is the non-limit earth pressure matrix of the soil outside the pit, is the wall stiffness matrix, is the soil spring stiffness matrix, is the deformation matrix of the underground continuous wall, is the support stiffness matrix, When the flash-down servo support is installed, the foundation pit retaining structure has a deformation matrix. is the concentration matrix.

[0028] Furthermore, the support stiffness matrix includes a flash-down servo support stiffness.

[0029] Furthermore, the concentrated force matrix includes the top force applied by the flash-down servo support.

[0030] In this step, if Figure 3 As shown in the figure, the load increment includes the soil pressure increment of the excavated soil and the increment caused by the top force actively applied by the flash-down servo support. When calculating the top force, the process of actively applying the top force is regarded as adding an incremental load F. hThe calculation is based on the action on the foundation pit retaining structure. At this time, the equivalent spring 3 of the flash-down servo support on the retaining side is supporting the prestress. In the foundation pit model, the equivalent soil spring 4 of the soil in the pit is used to simulate the unexcavated soil in the foundation pit. The first incremental load and the deformation of the foundation pit retaining structure when the flash-down servo support is installed are superimposed on the previous calculation results, and the true results of the internal force and deformation of the support structure after considering the prestress can be obtained.

[0031] According to the mixed boundary condition principle of "concentrated force + support", the servo support stiffness and the preset servo axis force are set, and the servo support stiffness is also considered in the support stiffness matrix. The pre-applied servo axis force is considered in the concentrated force matrix At the same time, the soil resistance in the pit is updated After adding the servo steel support, the equilibrium equation of the entire enclosure structure becomes the above equation 2.

[0032] In step S5, the top support device is depressurized and retracted to release the support to the underground continuous wall. At the same time, the connection between the hoist rope of the winch and the temporary supporting purlin is released to pour the concrete of the reinforced concrete support or floor slab.

[0033] In a specific embodiment of the present invention, in step S6, the second incremental load and the existing deformation of the foundation pit retaining structure when the flash-down servo support is removed are superimposed on the calculation result of step S4, and the equilibrium equation of the retaining structure is obtained as follows: Equation 3, In equation 3, is the non-limit earth pressure matrix of the soil outside the pit, is the wall stiffness matrix, is the soil spring stiffness matrix, is the deformation matrix of the underground continuous wall, is the support stiffness matrix, When the flash-down servo support is removed, the foundation pit retaining structure has a deformation matrix. is the reaction force matrix.

[0034] Further, the support stiffness matrix in step S6 includes the support stiffness of the concrete support or floor slab in step S5.

[0035] Still further, the reaction force matrix includes a reaction force to a support force of the removed flash-down servo support.

[0036] like Figure 4 and Figure 5 As shown, the temporary support is removed, and the reaction force of the support force of the removed flash-down servo support is regarded as the second incremental load acting on the foundation pit retaining structure, and the added concrete support or floor slab is regarded as the newly added support.

[0037] The removal of the flash-drop servo support is calculated as adding an incremental load, and the load increment is the reaction force of the support force of the removed flash-drop servo support. The added already cast concrete support or floor slab 5 is used as a newly added support. In the foundation pit model, the already cast concrete support or floor slab equivalent spring 6 is used to simulate the already cast concrete support or floor slab 5. The second incremental load and the existing deformation of the foundation pit retaining structure when the flash-drop servo support is removed are superimposed on the calculation result of step S4 to obtain the force change result of the supporting structure after the flash-drop servo support is removed.

[0038] Add concrete supports or slabs to be considered in the support stiffness matrix The reaction force of the support force of the removed flash-down servo support is considered in the reaction force matrix At the same time, the soil resistance in the pit is updated .

[0039] After removing the servo steel support, the equilibrium equation of the entire enclosure structure becomes equation 3 mentioned above.

[0040] Furthermore, after the calculation is completed, the design parameters such as the depth, thickness and reinforcement of the enclosure structure are adjusted according to the calculated wall stress and deformation under various working conditions.

[0041] The present invention provides an incremental calculation method for the deformation of a foundation pit retaining structure under the action of a flash-down servo support. Compared with the traditional method, this method can truly simulate the entire process of foundation pit excavation and accurately calculate the deformation and internal force of the retaining structure at each stage of construction, thereby more truly reflecting the control effect of the flash-down servo steel support on the deformation of the deep foundation pit retaining structure and improving the reliability of the retaining structure design.

[0042] The present invention is described in detail above in conjunction with the embodiments of the accompanying drawings. A person skilled in the art can make various variations of the present invention according to the above description. Therefore, certain details in the embodiments should not constitute a limitation of the present invention, and the scope of protection of the present invention shall be defined by the scope of the attached claims.

Claims

1. A method for calculating the deformation increment of a flash-down servo-supported foundation pit retaining structure, characterized in that: The steps include: S1: Establish a foundation pit model according to the project conditions, and set the number of earth excavation layers for the established foundation pit model; S2: simulate the excavation of the first layer of earthwork, simulate the pouring of the first concrete support in the foundation pit model, and perform the first calculation of the deformation of the foundation pit retaining structure; S3: simulate the excavation of the next layer of earthwork, simulate the lowering of temporary supporting purlins in the foundation pit model, and use the flash-down servo support to apply the top force according to the design value; S4: applying a top force according to the design value of the flash-down servo support to the foundation pit retaining structure as the first incremental load, and superimposing the first incremental load and the existing deformation of the foundation pit retaining structure when the flash-down servo support is installed to the calculation result of the first calculation; S5: Simulate pouring concrete support or floor slab on the top surface of the flash-down servo support in the foundation pit model; S6: dismantle the temporary supporting purlin and the flash-down servo support, regard the reaction force of the support force of the dismantled flash-down servo support as the second incremental load acting on the foundation pit retaining structure, and superimpose the second incremental load and the existing deformation of the foundation pit retaining structure when the flash-down servo support is dismantled to the calculation result of step S4; S7: Determine whether it is the last layer of earth excavation. If so, end the operation and output the calculation results of the above steps. If not, repeat steps S3 to S6.

2. The method for calculating the deformation increment of the flash-down servo-supported foundation pit retaining structure according to claim 1 is characterized in that: The first calculation of the deformation of the foundation pit retaining structure in step S2 includes: Adding the load increment caused by excavating the first layer of earthwork into the foundation pit model, wherein the load increment caused by excavating the first layer of earthwork includes the reduction of static upper pressure on the foundation pit side caused by excavation and the release of elastic resistance of the soil in the excavated soil; The equilibrium equation of the enclosure structure for the first calculation is: Equation 1, In equation 1, is the non-limit earth pressure matrix of the soil outside the pit, is the wall stiffness matrix, is the soil spring stiffness matrix, is the deformation matrix of the underground continuous wall, is the support stiffness matrix.

3. The method for calculating the deformation increment of the flash-down servo-supported foundation pit retaining structure according to claim 1 is characterized in that: In step S4, the first incremental load and the existing deformation of the foundation pit retaining structure when the flash-down servo support is installed are superimposed on the calculation result of the first calculation, and the equilibrium equation of the retaining structure is obtained as follows: Equation 2, In equation 2, is the non-limit earth pressure matrix of the soil outside the pit, is the wall stiffness matrix, is the soil spring stiffness matrix, is the deformation matrix of the underground continuous wall, is the support stiffness matrix, When the flash-down servo support is installed, the foundation pit retaining structure has a deformation matrix. is the concentration matrix.

4. The method for calculating the deformation increment of the flash-down servo-supported foundation pit retaining structure according to claim 3 is characterized in that: The support stiffness matrix includes the flash-down servo support stiffness.

5. The method for calculating the deformation increment of the flash-down servo-supported foundation pit retaining structure according to claim 3 is characterized in that: The concentrated force matrix includes the top force applied by the flash-down servo support.

6. The method for calculating the deformation increment of the flash-down servo-supported foundation pit retaining structure according to claim 1 is characterized in that: In step S6, the second incremental load and the existing deformation of the foundation pit retaining structure when the flash-down servo support is removed are superimposed on the calculation result of step S4, and the equilibrium equation of the retaining structure is obtained as follows: Equation 3, In equation 3, is the non-limit earth pressure matrix of the soil outside the pit, is the wall stiffness matrix, is the soil spring stiffness matrix, is the deformation matrix of the underground continuous wall, is the support stiffness matrix, When the flash-down servo support is removed, the foundation pit retaining structure has a deformation matrix. is the reaction force matrix.

7. The method for calculating the deformation increment of the flash-down servo-supported foundation pit retaining structure according to claim 6 is characterized in that: The support stiffness matrix in step S6 includes the support stiffness of the concrete support or floor slab in step S5.

8. The method for calculating the deformation increment of the flash-down servo-supported foundation pit retaining structure according to claim 6 is characterized in that: The reaction force matrix includes reaction forces to the support forces of the removed flash-down servo support.

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