Design method of deep foundation pit bracing blade wall based on stiffness matching and deformation control

Abstract

This invention discloses a design method for blade wall replacement in deep foundation pits based on stiffness matching and deformation control. The method involves obtaining the equivalent stiffness of the original support and deformation control indices of the retaining structure; establishing a shear-bending coupled stiffness model within the blade wall surface; setting a stiffness matching coefficient, constructing a stiffness matching equation, and solving for the recommended combination of section parameters; establishing a deformation control equation for the retaining structure based on the principle of elastic foundation beams, back-calculating the maximum allowable spacing, and outputting the standardized spacing; establishing a dual-control reinforcement model, introducing a temporary structure importance reduction coefficient, calculating the area of ​​edge longitudinal reinforcement and the reinforcement ratio of horizontally distributed reinforcement, and outputting complete design parameters. This invention achieves rapid design of blade walls based on stiffness matching and deformation control for the first time, improving efficiency by more than 80% compared to traditional finite element trial calculation methods, ensuring continuous deformation of the support system before and after replacement, and controllable failure modes.

Claims

1. A design method for deep foundation pit replacement blade wall based on stiffness matching and deformation control, characterized in that, Includes the following steps: Step 1: Parameter Acquisition Obtain the equivalent stiffness of the original support system at the layer to be replaced. And the deformation control index of the retaining structure under the support replacement condition. ; Step 2: Stiffness Matching Design Establish a calculation model for the lateral stiffness of the blade wall. ,in For the length of the blade wall, For blade wall thickness, For the height of the blade wall, These are the elastic modulus and shear modulus of the wall material for the blade wall; a stiffness matching coefficient is set. Construct stiffness matching equations By combining the preset structural constraints, at least one set of recommended blade wall section parameters can be obtained. combination; Step 3: Deformation Control Design Based on the cross-sectional parameters determined in step 2, a deformation control equation for the enclosure structure under the support of discrete blade walls is established, using the aforementioned deformation control index. As boundary conditions, calculate the maximum allowable spacing of the blade walls. Based on the principle of modularization, the standardized blade wall layout spacing is output. ; Step 4: Reinforcement Design Based on the blade wall section parameters output in step 2 and the standardized blade wall arrangement spacing output in step 3 A stress analysis model of the blade wall was established, and the design bending moment of the blade wall under the condition of bracing replacement was calculated. and shear design value ; Calculate the edge longitudinal reinforcement area of ​​the blade wall according to the formulas for the bearing capacity of reinforced concrete normal and oblique sections. and horizontal distribution reinforcement ratio and output the blade wall section parameters. Standardized blade wall layout spacing Edge longitudinal reinforcement area and horizontal distribution reinforcement ratio .

2. The design method for deep foundation pit replacement blade wall based on stiffness matching and deformation control according to claim 1, characterized in that, In step 2, the calculation model for the lateral stiffness within the blade wall surface is a coupled stiffness model considering bending and shear deformation, and its expression is: in, Let the moment of inertia of the cross section be... For cross-sectional area, The coefficient for shear stress non-uniformity is 1.2 for rectangular sections.

3. The design method for deep foundation pit replacement blade wall based on stiffness matching and deformation control according to claim 1, characterized in that, stiffness matching coefficient in step 2 Based on the distance from the bottom of the pit to the support layer The hierarchical settings are as follows: When d≤3m, it is defined as the lower support layer, and is taken as... ; When 3 < d ≤ 6m, it is defined as the middle strut replacement layer, taking ; When d > 6m, it is defined as the upper support layer, and is taken as... .

4. The design method for deep foundation pit replacement blade wall based on stiffness matching and deformation control according to claim 1, characterized in that, The construction constraints in step 2 include: blade wall thickness. The aspect ratio of the blade wall .

5. The design method for deep foundation pit replacement blade wall based on stiffness matching and deformation control according to claim 1, characterized in that, Step 3, which establishes the deformation control equations of the enclosure structure under the support of discrete blade walls, specifically includes: The discrete support of the blade wall is equivalent to an elastic point support, and the deflection differential equation of the retaining pile or retaining wall is established based on the elastic foundation beam or the finite difference method; the deformation control index is used as the basis for this equation. As a limit condition for the lateral displacement of the enclosure structure, the maximum allowable spacing of the blade walls is solved iteratively or analytically. ; will the Round down to the preset modular spacing series to output standardized blade wall layout spacing. .

6. The design method for deep foundation pit replacement blade wall based on stiffness matching and deformation control according to claim 5, characterized in that, The standardized blade wall arrangement spacing It can be selected from at least one of 2m, 2.5m, 3m, 4m, 5m, and 6m, or customized according to the modulus of the foundation pit side length.

7. The design method for deep foundation pit replacement blade wall based on stiffness matching and deformation control according to claim 1, characterized in that, In step 4, the area of ​​the longitudinal reinforcement at the edge of the blade wall is calculated according to the formulas for the bearing capacity of the normal and oblique sections of reinforced concrete. and horizontal distribution reinforcement ratio Specifically, it includes: Edge longitudinal reinforcement area of ​​blade wall calculate: in, This is the importance coefficient for temporary structures. The effective height of the cross section, This is the distance from the resultant force point of the tensile reinforcement to the edge of the cross section; Calculation of horizontal distribution reinforcement ratio: in, The horizontal distribution reinforcement ratio, This is the design value for the tensile strength of the stirrups. The spacing between horizontally distributed reinforcing bars.

8. The design method for deep foundation pit replacement blade wall based on stiffness matching and deformation control according to claim 7, characterized in that, Step 4 also includes a target destruction mode control step: Based on the target failure mode instructions input by the designers, the importance coefficient of the temporary structure is determined differentially. Reinforcement control conditions: If the target failure mode instruction is "ductile bending failure", then... And configure horizontally distributed reinforcement according to the principle of strong shear and weak bending to meet the requirements. ; If the target failure mode instruction is "economic reinforcement mode", then... Reinforcement is configured according to the principle of simultaneous bending and shear, to meet the requirements. ; in, The flexural bearing capacity is calculated based on the actual reinforcement. This represents the shear capacity calculated based on the actual reinforcement.

9. The design method for deep foundation pit replacement blade wall based on stiffness matching and deformation control according to claim 8, characterized in that, Step 4 also includes a destruction mode determination step: Calculate the ultimate load based on flexural reinforcement and the ultimate load according to shear reinforcement ,in, ;like If so, then output the "Bending Failure Control" message; if If the condition is not met, a "shear failure control" message will be output, and it will be suggested that the reinforcement scheme be adjusted.

10. The design method for deep foundation pit replacement blade wall based on stiffness matching and deformation control according to any one of claims 1 to 9, characterized in that, Step 4 output blade wall section parameters Standardized blade wall layout spacing Edge longitudinal reinforcement area and horizontal distribution reinforcement ratio Used for the industrial production of prefabricated blade wall units, or for the processing of formwork and reinforcing bars for cast-in-place reinforced concrete blade walls.

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