Method for calculating thickness of assembled retaining wall of rectangular cable well

Abstract

The invention belongs to the technical field of civil construction, and particularly provides a rectangular cable well assembly type retaining wall thickness calculation method, which comprises the following steps: carrying out structural design on a cable well assembly type retaining wall; analyzing the relationship between the excavation depth values of different soil properties and the dado pressure of the soil body; the influence of the cohesive force and the internal friction angle on the wall protection soil pressure is analyzed; calculating a critical stable depth value; and calculating the thickness design value of the assembled retaining wall of the cable well. According to the method, the wall protection thickness is designed and calculated, and construction safety and quality can be guaranteed. According to the method, a critical value calculation relational expression of the stable depth value, the internal friction angle and the cohesive force is provided by analyzing influence factors such as the depth value, the cohesive force and the internal friction angle, and the soil pressure stable depth value is obtained through calculation. And finally, a design thought and a design value of the thickness of the arm guard are put forward, and favorable reference is provided for actual engineering.

Description

Technical Field

[0001] The invention relates to the technical field of civil engineering, and in particular to a method for calculating the thickness of an assembled protective wall of a rectangular cable well. Background Art

[0002] Artificial bored piles are increasingly used in engineering construction due to their advantages such as simple construction equipment, no noise and vibration during the construction process, and easy inspection of the bearing layer, such as pile foundations in high-rise buildings, anti-slip piles in geological disaster prevention and control, and bored piles that bear vertical loads in bridge projects. As a supporting structure for the air surface after excavation, the artificial bored pile retaining wall is mainly subjected to the lateral earth pressure exerted on it by the soil behind the wall. The relationship between the magnitude of this earth pressure and the excavation depth of the bored pile has not been studied much so far, and the safety and reliability of the retaining wall design will be directly related to the quality of the bored pile and the safety of the construction operators. The present invention is based on the interaction mechanism between the artificial bored pile retaining wall and the soil behind the retaining wall, focusing on the law of the change of the retaining wall soil pressure with the excavation depth value, and combining engineering examples to compare the current retaining wall design method for optimization design, so as to provide a reference for the design and construction of artificial bored pile retaining walls in actual projects. Summary of the invention

[0003] The technical problem to be solved by the present invention is to provide a method for calculating the thickness of an assembled protective wall of a rectangular cable well, and to design and calculate the thickness of the protective wall, which is beneficial to ensuring construction safety and quality.

[0004] In order to solve the above technical problems, the technical solution adopted by the present invention is: a method for calculating the thickness of a rectangular cable well assembled protective wall, comprising the following steps: Step 1: structural design of the assembled protective wall of the cable well; Step 2: Analyze the relationship between the excavation depth of different soil types and the soil pressure on the retaining wall; Step 3: Analyze the influence of cohesion and internal friction angle on the retaining wall soil pressure; Step 4: Calculate the critical stability depth value; Step 5: Calculate the design value of the thickness of the cable well prefabricated wall.

[0005] In a preferred solution, in step 1, the assembled cable well wall protection adopts a segmented structure in the vertical direction, including a plurality of wall protection sections, and the wall protection sections are prefabricated by slicing in a horizontal ring direction.

[0006] In a preferred solution, in step 2, a relationship curve between excavation depth and soil pressure on retaining wall under different soil conditions is obtained through simulation analysis.

[0007] In the preferred solution, in step 2, the pressure of the soil on the retaining wall increases with the depth of excavation. When the excavation depth reaches a critical value, the pressure of the soil on the retaining wall does not change. The excavation depth at this time is the critical stable depth value.

[0008] In the preferred solution, in step 3, different cohesion forces are obtained through simulation analysis. and internal friction angle Under the condition of excavation depth, the relationship curve between the soil pressure on the retaining wall is shown.

[0009] In the preferred solution, in step 3, as the cohesion increases, the critical stable depth value of the pressure on the same soil retaining wall decreases; as the internal friction angle increases With the increase of, the critical stable depth of pressure on the same soil retaining wall decreases.

[0010] In a preferred embodiment, in step 4, the relationship between the critical stability depth value and the internal friction angle and cohesion is expressed as follows: ; in, is the internal friction angle of the soil, For soil cohesion.

[0011] In a preferred solution, in step 5, calculating the design value of the thickness of the assembled protective wall of the cable well includes the following steps: S501. Calculate the maximum earth pressure acting on the retaining wall; S502. Calculate the maximum bending moment on the retaining wall M ; S503. Calculate the thickness of the protective wall d , the calculation formula is: ; in, M is the maximum bending moment at mid-span, H For the wall protection section, It is the tensile strength of concrete at the center.

[0012] In a preferred solution, in step S501, the maximum earth pressure acting on the retaining wall is calculated as follows: ; ; in, is the maximum earth pressure, is the Coulomb active earth pressure coefficient, is the weight of the soil, h is the depth of the soil, is the internal friction angle of the soil.

[0013] In a preferred solution, in step S502, the maximum bending moment is calculated as follows: ; in, is the bending moment on the left side, is the bending moment on the right side, K = a / b , a The side pressure arch loses height. b Half of the side length of the pile section ，q is the unit lateral pressure.

[0014] The present invention provides a method for calculating the thickness of a rectangular cable well assembly wall, which has the following beneficial effects: 1. The present invention is based on the interaction mechanism between the bored pile retaining wall and the soil behind the retaining wall, focuses on studying the law of variation of retaining wall soil pressure with excavation depth, and compares the existing retaining wall design method with engineering examples to optimize the design, so as to provide a reference for the design and construction of bored pile retaining walls in actual projects.

[0015] 2. In step 1 of the present invention, it is evaluated whether the structure of the well can withstand the various forces and loads applied by the transmission lines and cables, taking into account the dead weight of the transmission cables and the tension applied during power transmission, the underground pressure, etc., to facilitate the structural design of the transmission line and cable well.

[0016] 3. The depths of different soil stability points are different, but they are basically between 5.0 and 7.0 m. In order to ensure construction safety and save manpower and material resources, the soil conditions should be specifically considered before formulating a construction plan to improve construction safety.

[0017] 4. By analyzing the data of soil pressure stability depth, cohesion and internal friction angle, a quantitative relationship between the three is fitted. In future arm guard design, only the cohesion of the foundation soil and the internal friction angle are needed to quickly calculate the soil pressure stability depth value, and finally select this value for the wall thickness design. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The present invention will be further described below in conjunction with the accompanying drawings and embodiments: Figure 1 is the cable well wall protection section; Figure 2 It is the reinforcement arrangement diagram; Figure 3 This is the relationship curve between retaining wall pressure and depth in loam condition; Figure 4 This is the relationship curve between retaining wall pressure and depth in sandy loam; Figure 5 This is the relationship curve between retaining wall pressure and depth in clay condition; Figure 6 This is the relationship curve between retaining wall pressure and depth in the case of silt sand; Figure 7 The curve of the relationship between retaining wall pressure and depth in sandy soil; Figure 8 It is the fitting curve of excavation depth and maximum stress when the cohesion is 10000Pa; Fig. 9 It is the fitting curve of excavation depth and maximum stress when the cohesion is 18000Pa; Fig.10 It is the fitting curve of excavation depth and maximum stress when the cohesion is 32000Pa; Fig.11 The internal friction angle is The fitting curve of excavation depth and maximum stress; Fig.12 The internal friction angle is The fitting curve of excavation depth and maximum stress at that time; Fig.13 The internal friction angle is The fitting curve of excavation depth and maximum stress; Fig.14 This is a simplified diagram for calculating the maximum bending moment. DETAILED DESCRIPTION

[0019] The specific implementation modes of the present invention are described in detail below with reference to the accompanying drawings.

[0020] A method for calculating the thickness of a rectangular cable well assembly wall comprises the following steps: Step 1: Design the prefabricated and assembled protective wall of the cable well. This embodiment takes a cable well with a length of 2m, a width of 1.6m, and a depth of 3.2m as an example. The prefabricated reinforced concrete protective wall design of the anchor cable well adopts a segmented structure in the vertical direction, including several protective wall sections, and adopts a slice prefabrication design concept in the horizontal direction. Through the pouring of concrete, each piece of prefabricated wall is connected into a whole, thereby improving its shear resistance and solving the problem of water seepage in wall protection. In order to meet the size of the cable well, 8 protective wall sections are installed in the vertical direction. The protective wall section is a prefabricated wall with a thickness of 8cm and a height of 40cm.

[0021] In actual projects, the prefabricated reinforced concrete cable well wall material is C30 concrete and HRB400 grade ordinary steel bars. Figure 1 As shown, the steel bars are arranged as Figure 2As shown. The prefabricated concrete cable construction method reduces the disturbance of mechanical excavation to the railway roadbed and reduces the steel bar processing and concrete mixing sites. The construction process can be described as: dismantling the existing protective fence, scraping and pressing ballast, installing the first section of the cable well prefabricated wall → scraping and pressing ballast, installing the second section of the cable well prefabricated wall → digging the cable well to a depth of 0.4m, sinking the cable prefabricated wall 0.4m, installing the third section of the cable well prefabricated wall → continue digging the cable well and installing the cable well prefabricated wall at the same time until the designed depth is reached → handling the concrete joints → covering the plate.

[0022] Step 2: The critical stress point of the retaining wall is different under different soil environments. The excavation depth and stress of loam, sandy loam, clay, silt and sand are analyzed. Based on the finite element theory, ANSYS is used to establish a finite element model. The finite element analysis of the excavation process of the artificial bored pile when the soil around the pile is a semi-infinite body is carried out. The influence of the depth of the bored pile on the earth pressure of the guard arm under several soil types is simulated respectively. The excavation depth and maximum stress curves are shown in the figure below. Figure 3~Figure 7 As shown, the fitting curve analysis results of the relationship between the wall pressure and the depth are shown in Table 1.

[0023]

[0024] In Table 1, c is the cohesion, is the internal friction angle, is the expansion angle, x is the excavation depth, y is the maximum stress, and h is the critical stable depth value when the retaining wall is under pressure and reaches stability.

[0025] Through the stress analysis of different soils, it can be concluded that the pressure acting on the retaining wall increases with the depth of excavation within a certain range, and reaches a stable value after reaching a critical point, and the pressure of the soil on the retaining wall basically does not change. The depth of the stable point of different soils is different, but it is basically between 5.0 and 7.0m. In order to ensure construction safety and save manpower and material resources, the soil conditions should be specifically considered before formulating a construction plan.

[0026] Step 3: Analyze the effects of cohesion and internal friction angle on retaining wall soil pressure. Soil shear strength is an important indicator that describes the ability of soil to resist shear stress and is usually used in engineering design and soil stability analysis.

[0027] Cohesion and internal friction angle are two important parameters of soil shear strength index. Cohesion is the adsorption force between soil particles, which is the ability of soil to resist shear without bonding. The internal friction angle is another important indicator to describe the resistance of soil to shear stress, which indicates the ability of soil to resist shear when not subject to external constraints. The value is used to analyze the changing relationship between the retaining wall pressure and depth under different setting conditions, and the specific calculation formula is calculated to guide the engineering design.

[0028] 1) The influence of cohesion on shear strength, Figure 8~Figure 10 The relationship curves between excavation depth and maximum stress were obtained through simulation analysis when the cohesion was 10000Pa, 18000Pa, and 32000Pa respectively. The analysis showed that when other parameters were constant, when C = 32000Pa, the pressure on the retaining wall reached stability at about 5.0m. Therefore, with the increase of cohesion, the critical stable depth value of the pressure on the same soil retaining wall decreased.

[0029] (2) The influence of internal friction on shear strength, Figure 11~Figure 13 The internal friction angles are , , The relationship curve between excavation depth and maximum stress is obtained through simulation analysis. It can be analyzed from the image that when other parameters are constant, When the pressure on the retaining wall reaches a stable state at about 4.5 m, the above analysis shows that as the internal friction angle increases, With the increase of, the critical stable depth of pressure on the same soil retaining wall decreases.

[0030] Step 4: Based on the influencing factors analyzed in steps 3 and 4, propose ideas for the design of the retaining wall thickness and calculate the stable depth value of the earth pressure.

[0031] By analyzing the finite element simulation results of steps two and three, the formula in step four is obtained by fitting after processing the data. When designing the thickness of the arm guard, it is only necessary to know the soil cohesion and internal friction angle of the foundation soil to quickly calculate the stable depth value of the earth pressure, and select this value for the design of the wall thickness.

[0032] By analyzing the above two factors, the relationship between the depth value and the internal friction angle and cohesion is obtained as follows:

[0033] The critical value of the depth stability value is calculated by combining the above formula with relevant data. Calculating the critical value has a certain guiding role in the actual engineering design and construction.

[0034] Step 5: Propose design ideas for wall thickness and calculate its design value.

[0035] The first step is to calculate the maximum earth pressure acting on the retaining wall. The calculation formula of the maximum earth pressure acting on the retaining wall is: ; ; in, is the maximum earth pressure, is the Coulomb active earth pressure coefficient, is the weight of the soil, h is the depth of the soil, is the internal friction angle of the soil.

[0036] The second step is to calculate the maximum bending moment on the retaining wall. The mid-span bending moment value of the long side of the retaining wall is the largest, which is the most unfavorable section. In actual projects, the long-diameter ratio of the rectangular bored pile retaining wall is relatively large, and the closed rectangular frame plane internal force analysis method with four sides of equal cross-section bearing uniform pressure is often used, such as Fig.14 shown.

[0037] Calculate the bending moment: ; in, is the bending moment on the left side, is the bending moment on the right side, K=a / b, a The side pressure arch loses height. b Half of the side length of the pile section ，q is the unit lateral pressure.

[0038] ; b is half of the long side of the bored pile section. It is the rock strength or formation solidity coefficient.

[0039] The third step is to calculate the thickness of the protective wall. d : ; Among them, M is the maximum bending moment in the mid-span, H is the length of the retaining wall section, It is the tensile strength of concrete at the center.

[0040] The above embodiments are only preferred technical solutions of the invention and should not be regarded as limitations of the invention. The protection scope of the invention should be the technical solutions recorded in the claims, including equivalent replacement solutions of the technical features in the technical solutions recorded in the claims. That is, equivalent replacement improvements within this scope are also within the protection scope of the invention.

Claims

1. A method for calculating the thickness of a rectangular cable well assembled protective wall, characterized in that: The following steps are involved: Step 1: structural design of the assembled protective wall of the cable well; Step 2: Analyze the relationship between the excavation depth of different soil types and the soil pressure on the retaining wall; Step 3: Analyze the influence of cohesion and internal friction angle on the retaining wall soil pressure; Step 4: Calculate the critical stability depth value; Step 5: Calculate the design value of the thickness of the cable well prefabricated wall.

2. A method for calculating the thickness of a rectangular cable well assembly wall according to claim 1, characterized in that: In the step 1, the assembled cable well wall protection adopts a segmented structure in the vertical direction, including a plurality of wall protection sections, and the wall protection sections are prefabricated by slicing in the horizontal ring direction.

3. A method for calculating the thickness of a rectangular cable well assembly wall according to claim 1, characterized in that: In the step 2, through simulation analysis, a relationship curve between the excavation depth and the soil pressure on the retaining wall under different soil conditions is obtained.

4. A method for calculating the thickness of a rectangular cable well assembly wall according to claim 3, characterized in that: In the step 2, the pressure of the soil on the retaining wall increases with the depth of excavation. When the excavation depth reaches a critical value, the pressure of the soil on the retaining wall does not change. The excavation depth at this time is the critical stable depth value.

5. A method for calculating the thickness of a rectangular cable well assembly wall according to claim 1, characterized in that: In step 3, different cohesion forces are obtained through simulation analysis. and internal friction angle Under the condition of excavation depth, the relationship curve between the soil pressure on the retaining wall is shown.

6. A method for calculating the thickness of a rectangular cable well assembly wall according to claim 5, characterized in that: In step 3, as the cohesion increases, the critical stable depth of the pressure on the same soil retaining wall decreases; as the internal friction angle increases, the critical stable depth of the pressure on the same soil retaining wall decreases. With the increase of, the critical stable depth of pressure on the same soil retaining wall decreases.

7. A method for calculating the thickness of a rectangular cable well assembly wall according to claim 1, characterized in that: In step 4, the relationship between the critical stability depth value and the internal friction angle and cohesion is expressed as: ； in, is the internal friction angle of the soil, For soil cohesion.

8. A method for calculating the thickness of a rectangular cable well assembly wall according to claim 1, characterized in that: In the step 5, the thickness design value of the cable well assembled protective wall is calculated, including the following steps: S501. Calculate the maximum earth pressure acting on the retaining wall; S502. Calculate the maximum bending moment on the retaining wall M ; S503. Calculate the thickness of the protective wall d , the calculation formula is: ； in, M is the maximum bending moment at mid-span, H For the wall protection section, It is the tensile strength of concrete at the center.

9. A method for calculating the thickness of a rectangular cable well assembly wall according to claim 8, characterized in that: In step S501, the maximum earth pressure acting on the retaining wall is calculated as follows: ； ； in, is the maximum earth pressure, is the Coulomb active earth pressure coefficient, is the weight of the soil, h is the depth of the soil, is the internal friction angle of the soil.

10. A method for calculating the thickness of a rectangular cable well assembly wall according to claim 8, characterized in that: In step S502, the maximum bending moment is calculated as follows: ； in, is the bending moment on the left side, is the bending moment on the right side, K = a / b , a The side pressure arch loses height. b Half of the side length of the pile section ，q is the unit lateral pressure.

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