Method for calculating deformation increment of flash-down type servo support foundation pit enclosure structure

Abstract

The present application relates to the technical field of foundation pit deformation calculation, in particular to a kind of flash drop type servo support foundation pit enclosure structure deformation increment calculation method, comprising the following steps: establishing foundation pit model;Simulate excavating first layer of earthwork, pour first concrete support, carry out first calculation;S3: simulate excavating next layer of earthwork, utilize flash drop type servo support to exert top force;S4: the top force exerted is added to the calculation result of first calculation as an incremental load and the deformation of existing foundation pit enclosure structure;S5: pour concrete support or floor slab;S6: remove flash drop type servo support, the support removed is added to the calculation result of step S4 as an incremental load and the deformation of existing foundation pit enclosure structure;Judge whether it is the last layer of earthwork excavation, if yes, then end operation, if not, then repeat steps S3 to S6.The present application accurately calculates the deformation and internal force size of construction stage enclosure structure, and provides reliable guidance for pre-stage foundation pit enclosure structure design.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of foundation pit deformation calculation, in particular to a flash drop type servo support foundation pit enclosure structure deformation increment calculation method. BACKGROUND

[0002] The flash drop type servo steel support is a new type of deep foundation pit construction technology, which refers to the rapid setting of temporary pre-support in a short period of time after the completion of foundation pit excavation by means of vertical sliding module, and the application of pre-support force to the enclosure wall by hydraulic jack servo module, and finally the rapid pouring of concrete support on the pre-support, so as to effectively control the deformation of the support structure by greatly shortening the exposure time of the foundation pit. In the design process, the traditional design method faces some challenges, because when the enclosure structure is actively supported by the servo support, its stress and deformation are different from the case when the traditional support is passively supported. The design and calculation of the servo support active support usually lack reasonable methods, and the analysis of the active support effect is usually not deep enough. SUMMARY

[0003] The purpose of the present application is to overcome the defects of the prior art, provide a flash drop type servo support foundation pit enclosure structure deformation increment calculation method, and solve the problems of lack of reasonable methods for design and calculation of the servo support active support and the analysis of the active support effect is usually not deep enough.

[0004] The technical solution to achieve the above-mentioned purpose is:

[0005] The present application provides a flash drop type servo support foundation pit enclosure structure deformation increment calculation method, comprising the following steps:

[0006] S1: establishing a foundation pit model according to the engineering conditions, and setting the number of earthwork excavation layers for the established foundation pit model;

[0007] S2: simulating the excavation of the first layer of earthwork, simulating the pouring of the first concrete support in the foundation pit model, and performing the first calculation of the foundation pit enclosure structure deformation;

[0008] S3: simulating the excavation of the next layer of earthwork, simulating the lowering of the temporary support enclosure purlin in the foundation pit model, and applying the top force of the flash drop type servo support according to the design value;

[0009] S4: applying the top force of the flash drop type servo support according to the design value as the first incremental load to the foundation pit enclosure structure, and superimposing the first incremental load and the existing deformation of the foundation pit enclosure structure when the flash drop type servo support is installed to the calculation result of the first calculation;

[0010] S5: simulating the pouring of the concrete support or floor on the top surface of the flash drop type servo support in the foundation pit model;

[0011] S6: remove the temporary support of the surrounding purlin and the flash servo support, the reaction force of the removed flash servo support is regarded as the second incremental load acting on the foundation pit support structure, and the second incremental load and the existing deformation of the foundation pit support structure when the flash servo support is removed are superimposed on the calculation result of step S4;

[0012] S7: determine whether it is the last layer of earthwork excavation, if yes, end the operation and output the calculation results of the above steps, if not, repeat steps S3 to S6.

[0013] The further improvement of the flash servo support foundation pit support structure deformation increment calculation method of the application is that the first calculation of the deformation of the foundation pit support structure in step S2 includes:

[0014] The load increment caused by excavating the first layer of earthwork is added to the foundation pit model, and the load increment caused by excavating the first layer of earthwork includes the reduction of the static upward pressure on the side of the foundation pit caused by excavation and the release of the elastic resistance of the excavated soil body;

[0015] The balance equation of the support structure for the first calculation is:

[0016] Equation one,

[0017] In equation one, is the non-limiting 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.

[0018] The further improvement of the flash servo support foundation pit support structure deformation increment calculation method of the application is that in step S4, the existing deformation of the foundation pit support structure when the first incremental load and the flash servo support are installed is superimposed on the calculation result of the first calculation, and the balance equation of the support structure is:

[0019] Equation two,

[0020] In equation two, is the non-limiting 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, is the existing deformation matrix of the foundation pit support structure when the flash servo support is installed, is the concentrated force matrix.

[0021] The further improvement of the flash descending type servo support foundation pit enclosure structure deformation increment calculation method is that the support stiffness matrix comprises the flash descending type servo support stiffness.

[0022] The further improvement of the flash descending type servo support foundation pit enclosure structure deformation increment calculation method is that the concentrated force matrix comprises the top force applied by the flash descending type servo support.

[0023] The further improvement of the flash descending type servo support foundation pit enclosure structure deformation increment calculation method is that in step S6, the second increment load and the existing deformation of the foundation pit enclosure structure when the flash descending type servo support is removed are superimposed on the calculation result of step S4, and the balance equation of the enclosure structure is obtained as:

[0024] Equation three,

[0025] In equation three, is a non-limiting soil pressure matrix of the soil outside the pit, is a wall stiffness matrix, is a soil spring stiffness matrix, is a deformation matrix of the underground continuous wall, is a support stiffness matrix, is an existing deformation matrix of the foundation pit enclosure structure when the flash descending type servo support is removed, is a counterforce matrix.

[0026] The further improvement of the flash descending type servo support foundation pit enclosure structure deformation increment calculation method is that the support stiffness matrix in step S6 comprises the support stiffness of the concrete support or the floor in step S5.

[0027] The further improvement of the flash descending type servo support foundation pit enclosure structure deformation increment calculation method is that the counterforce matrix comprises the counterforce of the support force of the removed flash descending type servo support.

[0028] The flash descending type servo support foundation pit enclosure structure deformation increment calculation method has the following beneficial effects:

[0029] The flash descending type servo support foundation pit enclosure structure deformation increment calculation method can consider the active support effect of the flash descending type servo support at each excavation stage, and uses the increment method to regard the process of applying active support as adding an increment load acting on the enclosure structure for calculation, so that the whole process of foundation pit excavation is basically truly simulated, and the deformation and internal force size of the enclosure structure at each construction stage are accurately calculated, thereby providing reliable guidance for the design of the early foundation pit enclosure structure.

[0030] The application truly simulates the whole process of foundation pit excavation, accurately calculates the deformation and internal force size of the enclosure structure in each construction stage, thus more truly reflects the control effect of the flash descending type servo steel support on the deformation of the deep foundation pit enclosure structure, and improves the design reliability of the enclosure structure. BRIEF DESCRIPTION OF DRAWINGS

[0031] Figure 1 A flow chart of the flash descending type servo support foundation pit enclosure structure deformation increment calculation method of the application.

[0032] Figure 2 A schematic diagram of the active support process in the flash descending type servo support foundation pit enclosure structure deformation increment calculation method of the application.

[0033] Figure 3 An incremental calculation sketch corresponding to the active support process in the flash descending type servo support foundation pit enclosure structure deformation increment calculation method of the application.

[0034] Figure 4 A schematic diagram of the active support process in the flash descending type servo support foundation pit enclosure structure deformation increment calculation method of the application.

[0035] Figure 5 An incremental calculation sketch corresponding to the active support process in the flash descending type servo support foundation pit enclosure structure deformation increment calculation method of the application.

[0036] Reference signs: 1 - foundation pit enclosure structure; 2 - flash descending type servo support; 3 - equivalent spring of the flash descending type servo support; 4 - equivalent soil spring of the pit soil; 5 - already poured concrete support or floor; 6 - equivalent spring of the already poured concrete support or floor. DETAILED DESCRIPTION

[0037] The application will be further described below in combination with the drawings and specific embodiments.

[0038] Referring to Figure 1 The application provides a flash descending type servo support foundation pit enclosure structure deformation increment calculation method. To solve the problem that the traditional calculation method cannot accurately calculate the deformation of the foundation pit enclosure structure under the action of the flash descending type servo support, the application uses the incremental method in the calculation process, regards the process of applying the active support as adding an incremental load acting on the foundation pit enclosure structure to participate in the calculation, truly simulates the whole process of foundation pit excavation, accurately calculates the deformation and internal force size of the enclosure structure in each construction stage, and provides reliable guidance for the design of the early foundation pit enclosure structure. The flash descending type servo support foundation pit enclosure structure deformation increment calculation method of the application will be described below in combination with the drawings.

[0039] Referring to Figure 1, shows the flow chart of the flash drop type servo support foundation pit enclosure deformation increment calculation method of the present application. The following will be described in combination with Figure 1 the flash drop type servo support foundation pit enclosure deformation increment calculation method of the present application.

[0040] As shown in Figure 1 , the flash drop type servo support foundation pit enclosure deformation increment calculation method of the present application comprises the following steps:

[0041] Step S1 is executed: according to the engineering conditions, a foundation pit model is established, and the established foundation pit model is set with the earthwork excavation layers; wherein the engineering conditions include the basic engineering information such as the determined excavation depth of the foundation pit, the design parameters of the enclosure structure, and the soil layer parameters, and the foundation pit model is established based on the above information; then step S2 is executed;

[0042] Step S2 is executed: the first layer of earthwork is simulated to be excavated, the first concrete support is simulated to be poured in the foundation pit model, and the first calculation of the foundation pit enclosure deformation is performed; then step S3 is executed;

[0043] Step S3 is executed: the next layer of earthwork is simulated to be excavated, the temporary support surrounding purlin is simulated to be lowered in the foundation pit model, and the top force of the flash drop type servo support is applied according to the design value; then step S4 is executed;

[0044] Step S4 is executed: the top force of the flash drop type servo support according to the design value is applied as the first incremental load on the foundation pit enclosure structure, and the first incremental load and the existing deformation of the foundation pit enclosure structure when the flash drop type servo support is installed are superimposed on the calculation result of the first calculation; then step S5 is executed;

[0045] Step S5 is executed: the concrete support or floor on the top surface of the flash drop type servo support is simulated to be poured in the foundation pit model; then step S6 is executed;

[0046] Step S6 is executed: the temporary support surrounding purlin and the flash drop type servo support are removed, the reaction force of the removed flash drop type servo support is regarded as the second incremental load acting on the foundation pit enclosure structure, and the second incremental load and the existing deformation of the foundation pit enclosure structure when the flash drop type servo support is removed are superimposed on the calculation result of step S4; then step S7 is executed;

[0047] Step S7 is executed: it is judged whether it is the last layer of earthwork excavation, if yes, the operation is ended and the calculation results of the above steps are output, if not, steps S3 to S6 are repeatedly executed.

[0048] In one specific embodiment of the present application, the first calculation of the foundation pit enclosure deformation in step S2 comprises:

[0049] The load increment caused by excavating the first layer of earth is added to the foundation pit model, and the load increment caused by excavating the first layer of earth includes the reduction of the static earth pressure on the side of the foundation pit caused by excavation and the release of the elastic resistance of the earth in the excavated earth body;

[0050] The balance equation of the enclosure structure in the first calculation is:

[0051] Equation One,

[0052] In Equation One, is the non-limiting earth pressure matrix of the earth outside the pit, is the wall stiffness matrix, is the earth spring stiffness matrix, is the deformation matrix of the underground continuous wall, is the support stiffness matrix.

[0053] After the first excavation, the load increment is the earth pressure increment, which is composed of two parts: the first part is the reduction of the static earth pressure on the side of the foundation pit caused by excavation, which is equivalent to applying the reduction value of this pressure to the system in the opposite direction in the excavated earth body; the second part is the release of the elastic resistance of the earth in the excavated earth body (including horizontal and tangential earth elastic resistance), which is equivalent to applying these earth elastic resistances to the system in the opposite direction at the excavation site. The above load increment is added to the model and the first calculation is completed.

[0054] Further, as shown in step S3, Figure 2 the earth excavation of the foundation pit is carried out to the specified depth, the temporary support purlin is assembled in the excavated earth of the foundation pit, and then the flash descent type servo support 2 is pushed outwards to apply the top force to the foundation pit enclosure structure 1 (such as the underground continuous wall) according to the design value, so that the temporary support purlin applies prestressed support to the foundation pit enclosure structure 1.

[0055] In one specific embodiment of the present application, the first incremental load and the deformation of the foundation pit enclosure structure when the flash descent type servo support is installed are added to the calculation results of the first calculation, and the balance equation of the enclosure structure is:

[0056] Equation Two,

[0057] In Equation Two, is the non-limiting earth pressure matrix of the earth outside the pit, is the wall stiffness matrix, is the earth spring stiffness matrix, is the deformation matrix of the underground continuous wall, is the support stiffness matrix, is the deformation matrix of the foundation pit enclosure structure when the flash descent type servo support is installed, is the concentrated force matrix.

[0058] Furthermore, the support stiffness matrix includes the sag-type servo support stiffness.

[0059] Furthermore, the concentrated force matrix includes the top force applied by the slumping servo support.

[0060] In this step, such as Figure 3 As shown, the load increment includes the increase in earth pressure on the excavated soil, as well as the increment caused by the jacking force actively applied by the servo support. When calculating the jacking force, the process of actively applying the jacking force is considered as adding an incremental load F. h The calculation is performed on the retaining structure of the foundation pit. At this time, it is equivalent to the spring 3 of the descent servo support on the retaining side supporting the prestress. In the foundation pit model, the soil inside the pit is used as an equivalent soil spring 4 to simulate the unexcavated soil inside the foundation pit. By superimposing the first incremental load and the existing deformation of the foundation pit retaining structure when the descent servo support is installed onto the previous calculation results, the true results of the internal forces and deformations of the support structure after considering the prestressing effect can be obtained.

[0061] Based on the principle of mixed boundary conditions of "concentrated force + support", the servo support stiffness and the preset servo axial force are set, and the servo support stiffness is considered in the support stiffness matrix. The magnitude of the pre-applied servo axial force is taken into account in the concentrated force matrix. Inside, the soil resistance within the pit is simultaneously updated. After adding servo steel supports, the equilibrium equation of the entire enclosure structure becomes Equation 2 as described above.

[0062] In step S5, the top support device is depressurized and retracted, releasing its support to the diaphragm wall. At the same time, the connection between the hoisting rope of the winch and the temporary support waler is released, and the reinforced concrete support or floor slab is poured.

[0063] In one specific embodiment of the present invention, in step S6, the existing deformation of the foundation pit retaining structure when the second incremental load and the flash-drop servo support are removed is superimposed on the calculation result of step S4 to obtain the equilibrium equation of the retaining structure as follows:

[0064] Equation 3,

[0065] In equation three, The matrix of non-ultimate earth pressure on the soil outside the pit. Here is the wall stiffness matrix. Here is the soil spring stiffness matrix. The deformation matrix of the diaphragm wall. To support the stiffness matrix, When dismantling the servo-supported quick-release system, the retaining structure of the foundation pit already had a deformation matrix. This is the reaction force matrix.

[0066] Further, the support stiffness matrix in step S6 includes the support stiffness of the concrete support or floor in step S5.

[0067] Still further, the counterforce matrix includes the counterforce of the support force of the removed drop servo support.

[0068] As shown in Figure 4 and Figure 5 , the temporary support is removed, the counterforce of the support force of the removed drop servo support is regarded as the second incremental load acting on the foundation pit support structure, and the increased concrete support or floor is regarded as the newly added support.

[0069] The removed drop servo support is calculated as the added incremental load, the load increment of which is the counterforce of the support force of the removed drop servo support, and the increased already-poured concrete support or floor 5 is regarded as the newly added support, and the already-poured concrete support or floor 5 is simulated by the equivalent spring 6 in the foundation pit model. The second incremental load and the deformation of the foundation pit support structure when the drop servo support is removed are superimposed on the calculation result of step S4, so that the stress change result of the support structure after the drop servo support is removed is obtained.

[0070] The newly added concrete support or floor is considered in the support stiffness matrix , and the counterforce of the support force of the removed drop servo support is considered in the counterforce matrix . Meanwhile, the resistance of the soil in the pit is updated .

[0071] After the servo steel support is removed, the balance equation of the whole support structure becomes equation three.

[0072] Still further, after the operation is finished, the design parameters such as the depth, thickness and reinforcement of the support structure are adjusted according to the stress and deformation of the wall under each working condition obtained by calculation.

[0073] The application provides an incremental calculation method for the deformation of a foundation pit support structure under the action of a drop servo support. Compared with the traditional method, the method can truly simulate the whole process of the foundation pit excavation and accurately calculate the deformation and internal force of the support structure at each construction stage, so as to more truly reflect the control effect of the drop servo steel support on the deformation of the deep foundation pit support structure and improve the design reliability of the support structure.

[0074] The application is described in detail above with reference to the embodiments combined with the drawings, and those skilled in the art can make various changes to the application according to the above description. Thus, some details in the embodiments should not constitute a limitation on the application, and the protection scope of the application is defined by the appended claims.

Claims

1. A method for calculating the deformation increment of a flash-type servo support foundation pit enclosure, characterized in that, The method comprises the following steps: S1: establishing a foundation pit model according to engineering conditions, and setting the number of layers of earthwork excavation for the established foundation pit model; S2: simulating excavation of the first layer of earthwork, simulating pouring of the first concrete support in the foundation pit model, and performing first calculation on the deformation of the foundation pit enclosure structure; S3: simulating excavation of the next layer of earthwork, simulating lowering of the temporary support enclosing purlin in the foundation pit model, and applying the top force of the flash descent type servo support according to the design value; S4: applying the top force of the flash descent type servo support according to the design value as the first incremental load on the foundation pit enclosure structure, and superimposing the first incremental load and the existing deformation of the foundation pit enclosure structure when the flash descent type servo support is installed on the calculation result of the first calculation; S5: simulating pouring of the concrete support or floor on the top surface of the flash descent type servo support in the foundation pit model; S6: removing the temporary support enclosing purlin and the flash descent type servo support, applying the reaction force of the support force of the removed flash descent type servo support as the second incremental load on the foundation pit enclosure structure, and superimposing the second incremental load and the existing deformation of the foundation pit enclosure structure when the flash descent type servo support is removed on the calculation result of step S4; S7: determining whether it is the excavation of the last layer of earthwork, if yes, ending the operation and outputting the calculation results of the above steps, and if not, repeating steps S3 to S6; The first calculation on the deformation of the foundation pit enclosure structure in step S2 comprises: adding the load increment caused by the excavation of the first layer of earthwork into the foundation pit model, wherein the load increment caused by the excavation of the first layer of earthwork comprises the reduction of the static upward pressure of the foundation pit side caused by excavation and the release of the elastic resistance of the excavated soil; the balance equation of the enclosure structure for the first calculation is: [P e ] = [K] · [Δ] + [K m ] · [Δ] + [K s ] · [Δ] Equation 1, In equation one, [P e ] is the non-limiting earth pressure matrix of the soil outside the pit, [K] is the wall stiffness matrix, [K m ] is the soil spring stiffness matrix, [Δ] is the deformation matrix of the underground continuous wall, [K s ] is the support stiffness matrix; the balance equation of the enclosure structure obtained by superimposing the first incremental load and the existing deformation of the foundation pit enclosure structure when the flash descent type servo support is installed on the calculation result of the first calculation in step S4 is: [P e ] = [K] · [Δ] + [K m ] · [Δ] + [K s ] · ([Δ] - [Δ' s ]) + [F h ] Equation Two, In equation two, [P e ] is the non-limiting earth pressure matrix of the soil outside the pit, [K] is the wall stiffness matrix, [K m ] is the soil spring stiffness matrix, [Δ] is the deformation matrix of the underground continuous wall, [K s ] is the support stiffness matrix, [Δ' s ] is the existing deformation matrix of the pit enclosure structure when installing the flash servo support, [F h ] is the concentrated force matrix; the support stiffness matrix comprises the stiffness of the flash descent type servo support; the concentrated force matrix comprises the top force applied by the flash descent type servo support; the balance equation of the enclosure structure obtained by superimposing the second incremental load and the existing deformation of the foundation pit enclosure structure when the flash descent type servo support is removed on the calculation result of step S4 in step S6 is: In equation three, [P e ] is the non-limiting earth pressure matrix of the soil outside the pit, [K] is the wall stiffness matrix, [K m ] is the soil spring stiffness matrix, [Δ] is the deformation matrix of the underground continuous wall, [K s ] is the support stiffness matrix, [Δ' s ] is the existing deformation matrix of the pit enclosure structure when the flash servo support is removed, is the counterforce matrix; the support stiffness matrix in step S6 comprises the support stiffness of the concrete support or floor in step S5; the reaction force matrix comprises the reaction force of the support force of the removed flash descent type servo support.

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