Method and module for calculating and determining wall thickness of bored pile steel casing

Abstract

The application relates to the field of design calculation of bored piles, and particularly discloses a method for calculating and determining the wall thickness of a steel casing of a bored pile, which comprises the following steps: analyzing a stress mechanical model of the steel casing of the bored pile, taking a section of the steel casing structure and developing the section into a plate-shaped structure along the ring direction, equivalently simulating stability analysis of an axial compression rod system structure, calculating the cross-section parameters of the steel casing structure, the horizontal static load soil pressure and the axial force of the compression rod, when the internal stress of the compression rod of the steel casing structure is less than or equal to the critical stress of the compression rod stability, the steel casing structure is stable in the ring direction, the relationship between the diameter, the thickness of the steel casing structure and the static lateral pressure of the soil and the embedding depth of the steel casing is obtained, the diameter-thickness ratio range of the steel casing structure is further determined, and the purpose of scientifically and reasonably determining the wall thickness of the steel casing is achieved, construction safety is ensured, and the construction economy is improved.

Description

Technical Field

[0001] This invention relates to the field of bored pile technology, and in particular to a method and module for calculating and determining the wall thickness of the steel casing of bored piles. Background Technology

[0002] Drilled cast-in-place piles are pile columns made by forming pile holes in the foundation soil through mechanical drilling, steel pipe extrusion, or manual excavation on the engineering site, and then placing a steel cage inside and pouring concrete. Depending on the hole-forming method, drilled cast-in-place piles can be divided into several categories, such as driven cast-in-place piles, drilled cast-in-place piles, and excavated cast-in-place piles.

[0003] Drilled piles are widely used in foundation engineering. During drilling, steel casings are usually used to protect the borehole opening. In the existing technology, the diameter of the steel casing is selected according to the diameter of the drilled pile, the length is mainly determined according to the geological conditions, and the wall thickness of the steel casing is mainly determined based on experience.

[0004] With the development of domestic infrastructure, the design diameter of pile foundations is getting larger and larger, and the geological conditions they face are becoming more and more complex. The wall thickness of the steel casing is crucial to the stress stability of the steel casing and the economic efficiency of material selection. Determining the wall thickness of the steel casing based on experience is not only a great test of the qualifications and experience of technical personnel, but also requires technical personnel to have a thorough understanding of the conditions of the construction site. This method has great uncertainty and arbitrariness, and there are significant safety hazards in the construction process.

[0005] Therefore, how to scientifically and rationally determine the wall thickness of the steel casing, ensure construction safety, and improve construction economy has become a major problem faced by technicians in the construction of bored piles. Summary of the Invention

[0006] One of the objectives of this invention is, at least, to address the problem that the determination of steel casing wall thickness for borehole protection in existing borehole construction processes involves considerable arbitrariness and uncertainty based on experience. This invention provides a method for calculating and determining the wall thickness of steel casing for bored piles. This method analyzes the stress characteristics of the steel casing, identifies multiple factors affecting its wall thickness, and proposes a simplified calculation method for the steel casing wall thickness. This achieves the goal of scientifically and rationally determining the steel casing wall thickness, ensuring construction safety, and improving construction economy.

[0007] To achieve the above objectives, the technical solution adopted by the present invention includes the following aspects.

[0008] A method for calculating and determining the wall thickness of steel casing for bored piles includes the following steps: Step 1: Based on the installation structure of the steel casing of the bored pile, analyze the mechanical model of the stress on the steel casing of the bored pile. Step 2: Based on the stress state of the steel casing, take a segment of the steel casing structure with a segment length of b, and unfold the steel casing structure of this segment into a plate-like structure along the circumferential direction. At the same time, simulate the circumferential plate-like structure as an axially compressed rod system structure and perform a simulation stability analysis. Step 3: Calculate the cross-sectional parameters of the steel casing structure in Step 2, including the moment of inertia, radius of inertia, and slenderness ratio. Step 4: Calculate the axial force of the compression members of the steel casing structure based on the horizontal static earth pressure of the steel casing structure; Step 5: When the internal stress of the compression member of the steel casing structure is less than or equal to the critical stress for stability of the compression member, the steel casing structure is stable in the circumferential direction and will not produce a failure mode. Based on the cross-sectional parameters of the steel casing structure in Step 3 and the axial force of the compression member of the steel casing structure in Step 4, the relationship between the diameter and thickness of the steel casing structure and the static lateral pressure of the soil and the burial depth of the steel casing is calculated. Step 6: Based on the embedment depth of the steel casing structure, the soil unit weight value, and the static lateral pressure coefficient of the soil, obtain the ratio of the diameter to the wall thickness of the steel casing structure, and then determine the wall thickness of the steel casing for the bored pile.

[0009] Because steel casings have high compressive strength, failure and instability caused by their own material are usually unlikely to occur. However, this invention is based on the analysis that the failure mode of steel casings is often controlled by circumferential instability. By unfolding the steel casing into a plate-like structure and simulating the circumferential plate-like structure as an axially compressed rod system, a stability analysis is performed to establish the relationship between the axial force of the steel casing rod and the circumferential earth pressure on the steel casing. When the internal stress of the steel casing rod is within the critical stress range for rod stability, the steel casing can work stably without failure.

[0010] Preferably, in step two, the internal force state of the steel casing is set to be equivalent to the axial compression member of the steel casing structure with circumferential cross-sectional area, length and axial force N, thereby simulating the circumferential plate structure as an axially compressed rod system structure. The circumferential cross-sectional area of ​​the steel casing structure is b×t, where b is the segment length of the steel casing structure, t is the wall thickness of the steel casing, and the length of the steel casing structure is π×d.

[0011] Preferably, in step three, the moment of inertia of the steel casing section is I=bt. 3 / 12, radius of inertia Longer system In the formula, b is the length of the steel casing structure segment, A is the circumferential cross-sectional area of ​​the steel casing structure, d is the diameter of the steel casing structure, and t is the wall thickness of the steel casing.

[0012] Preferably, in step four, the horizontal static earth pressure q of the steel casing structure is q = Koγh, and the axial force N of the compression member of the steel casing structure is N = qbd / 2, where Ko is the static lateral pressure coefficient of the soil, which is determined according to different soil types, γ is the soil unit weight, h is the burial depth of the steel casing structure, b is the segment length of the steel casing structure, and d is the diameter of the steel casing structure. Different soil types and burial depths result in different static earth pressures on the steel casing structure. Therefore, the axial force N of the equivalent axially compressed rod system is directly proportional to the horizontal static earth pressure q, the segment length b of the steel casing structure, and the diameter d of the steel casing structure.

[0013] Preferably, in step four, the static lateral pressure coefficient Ko of the soil is determined according to different soil types. Under the condition of loose granular soil, Ko is 0.5 to 0.6; under the condition of compact granular soil, Ko is 0.3 to 0.5; under the condition of soft clay, Ko is 0.5 to 0.6; and under the condition of hard clay, Ko is 0.8 to 0.9.

[0014] Preferably, in step four, the soil unit weight γ is taken as 18 kN / m³. 3 -22 kN / m 3 Further optimization of γ to 20 kN / m 3 .

[0015] Preferably, in step five, the critical stress for stability of the compression bar σ´ is determined using Euler's formula, σ´=π 2 E / ελ 2 ε is the stability coefficient, taken as ε=1.2, E is the elastic modulus of steel, taken as E=200Gpa, and the internal stress of the compression member is σ=N / A. When the internal stress of the compression member σ≤ the critical stress for stability of the compression member, we get σ= N / A= Koγhbd / 2bt= Koγhd / 2t≤π 2 E / ελ 2 =π 2 E / 1.2×5.4 2 (d / t) 2 =0.282E / (d / t) 2 The results are as follows: (d / t) 3 ≤2×0.282E / Koγh=0.564E / Koγh, therefore, In each formula, A is the circumferential cross-sectional area of ​​the steel casing structure, N is the axial force of the compression member of the steel casing structure, d is the diameter of the steel casing structure, Ko is the static lateral pressure coefficient of the soil, γ is the unit weight of the soil, h is the burial depth of the steel casing structure, b is the segment length of the steel casing structure, d is the diameter of the steel casing structure, and t is the wall thickness of the steel casing.

[0016] By calculating the ratio of the diameter to the wall thickness of the steel casing structure under the condition that the internal stress of the compression member is less than or equal to the critical stress for stability of the compression member, it is found that the ratio of the diameter to the wall thickness of the steel casing is related to the static lateral pressure of the soil and the elastic modulus of the steel, and is inversely proportional to the cubic root of the embedment depth of the steel casing.

[0017] In step six, when the burial depth h of the steel casing structure is ≤ 2m, the ratio of the diameter to the wall thickness d / t of the steel casing structure is in the range of 100 to 140; when the burial depth h is 2m < h ≤ 4m, the ratio of the diameter to the wall thickness d / t of the steel casing structure is in the range of 80 to 120; and when the burial depth h is > 4m, the ratio of the diameter to the wall thickness d / t of the steel casing structure is in the range of 60 to 100.

[0018] Preferably, in step six, the burial depth h of the steel casing structure ranges from 2 to 4 m.

[0019] Preferably, for common steel casing structures with an burial depth h≤2m, the wall thickness of the steel casing is selected according to d / t=120~140.

[0020] Correspondingly, this application also provides a module for calculating and determining the wall thickness of the steel casing for bored piles, characterized in that it includes at least one processor and a memory communicatively connected to the at least one processor; the memory stores instructions executable by the at least one processor, which, when executed by the at least one processor, enables the at least one processor to perform the calculation process of the aforementioned method for calculating and determining the wall thickness of the steel casing for bored piles. Using this module, the steel casing wall thickness calculation and determination module can be applied independently in the process of calculating and verifying the wall thickness of the steel casing for bored piles, or it can be integrated into the overall construction software for bored piles.

[0021] In summary, by adopting the above technical solution, the present invention has at least the following beneficial effects: 1. This application analyzes the stress mechanics model of the steel casing of bored piles during use, and simulates its stress state as an equivalent compression rod structure. Combining the cross-sectional parameters of the steel casing structure, it analyzes the stability failure principle of the internal stress of the compression rod, and simplifies the calculation to obtain the relationship between the diameter and thickness of the steel casing structure and the static lateral pressure of the soil and the embedment depth of the steel casing. Then, based on the relevant parameters, it obtains the ratio of the diameter to the wall thickness of the steel casing structure, and then determines the wall thickness of the steel casing of the bored pile. This determination calculation process is simplified and convenient, and it is easy to quickly determine the wall thickness of the steel casing under the conditions of stress stability and material economy. 2. Simulating the circumferential plate structure as an axially compressed rod system can reasonably analyze the internal force state of the steel casing, ensuring the accuracy of the calculation of the steel casing's instability process, and simplifying and facilitating subsequent calculations; 3. The method for calculating and determining the wall thickness of the steel casing for bored piles proposed in this application analyzes and calculates the stress characteristics of the steel casing and proposes a simplified calculation method for the wall thickness of the steel casing. This method identifies multiple factors affecting the wall thickness of the steel casing, including the soil unit weight of the soil in which the steel casing is buried, the diameter of the steel casing, the burial depth of the steel casing, and other relevant parameters. This achieves the goal of scientifically and rationally determining the wall thickness of the steel casing, ensuring construction safety and improving construction economy. Attached Figure Description

[0022] Figure 1 This is a flowchart illustrating the method for calculating and determining the wall thickness of the steel casing for bored piles according to the present invention.

[0023] Figure 2 This is a schematic diagram of the installation and stress structure of the steel casing for the bored pile in this invention.

[0024] Figure 3 This is a schematic diagram of the stress plane of the steel casing of the bored pile in this invention.

[0025] Figure 4 This is a planar schematic diagram of the forces acting on the steel casing of the bored pile and the axial force N of the compression rod in this invention.

[0026] Figure 5 This is a schematic diagram of the equivalent compression member of the steel casing of the bored pile in this invention, which unfolds into a circumferential plate-like structure.

[0027] Figure 6 This is a schematic diagram of the cross-section of the steel casing segment of the bored pile in this invention.

[0028] Figure 7 This is a schematic diagram of the structure of the module for calculating and determining the wall thickness of the steel casing for bored piles according to the present invention.

[0029] The diagram shows the following labels: 1-Ground, 2-Steel casing, 3-Electronic equipment, 31-Processor, 32-Memory, 33-Input / output interface. Detailed Implementation

[0030] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments, so that the objectives, technical solutions, and advantages of the present invention will be clearer. It should be understood that the specific embodiments described herein are only for explaining the present invention and are not intended to limit the present invention. Example 1

[0031] Figure 1 A flowchart illustrating a method for calculating and determining the wall thickness of a steel casing for bored piles, as shown in an exemplary embodiment of the present invention, is presented, and mainly includes the following steps: Step 1: Based on the installation structure of the steel casing of the bored pile, analyze the force mechanics model of the steel casing of the bored pile, such as... Figure 2As shown, the steel casing 2 buried in the ground 1 is subjected to the pressure q of the surrounding soil. Step 2: Based on the stress state of the steel casing, select a segment of the steel casing structure with a segment length of b, such as... Figures 3-6 As shown, the diameter of the steel casing is d, the wall thickness of the steel casing is t, and the steel casing generates circumferential compressive stress σ due to the circumferential earth pressure q. The axial force is set to N. The steel casing segment is unfolded into a plate structure along the circumferential direction. At the same time, the circumferential plate structure is simulated as an axially compressed rod structure, and a simulation stability analysis is performed. Step 3: Calculate the cross-sectional parameters of the steel casing structure in Step 2, including the moment of inertia, radius of inertia, and slenderness ratio. Step 4: Calculate the axial force of the compression members of the steel casing structure based on the horizontal static earth pressure of the steel casing structure; Step 5: When the internal stress of the compression member of the steel casing structure is less than or equal to the critical stress for stability of the compression member, the steel casing structure is stable in the circumferential direction and will not produce a failure mode. Based on the cross-sectional parameters of the steel casing structure in Step 3 and the axial force of the compression member of the steel casing structure in Step 4, the relationship between the diameter and thickness of the steel casing structure and the static lateral pressure of the soil and the burial depth of the steel casing is calculated. Step 6: Based on the embedment depth of the steel casing structure, the soil unit weight value, and the static lateral pressure coefficient of the soil, obtain the ratio of the diameter to the wall thickness of the steel casing structure, and then determine the wall thickness of the steel casing for the bored pile.

[0032] Because steel casings have high compressive strength, failure and instability caused by their own material are usually not possible. However, this invention is based on the analysis that the failure mode of steel casings is often controlled by circumferential instability. By unfolding the steel casing into a plate-like structure and simulating the circumferential plate-like structure as an axially compressed rod system, a stability analysis is performed to establish the relationship between the axial force of the steel casing rod and the circumferential earth pressure on the steel casing. When the internal stress of the steel casing rod is within the critical stress range for rod stability, the steel casing can work stably without failure. The method for calculating and determining the wall thickness of the steel casing for bored piles, as described in this invention, analyzes and calculates the stress characteristics of the steel casing and proposes a simplified calculation method for the wall thickness. This method identifies multiple factors affecting the wall thickness of the steel casing, including the soil unit weight, diameter, and burial depth of the steel casing. This achieves the goal of scientifically and rationally determining the wall thickness of the steel casing, ensuring construction safety, and improving construction economy.

[0033] In step two, the internal force state of the steel casing is set to be equivalent to that of an axially compressed member with a circumferential cross-sectional area, length, and axial force N of the steel casing structure. The circumferential plate-like structure is then simulated as an axially compressed member structure. The circumferential cross-sectional area of ​​the steel casing structure is b×t, where b is the segment length of the steel casing structure, t is the wall thickness of the steel casing, and the length of the steel casing structure is π×d. When the steel casing is used for borehole protection in cast-in-place piles, it mainly bears the soil pressure q around the borehole opening. After taking a segment of length b along the vertical direction of the steel casing, the steel casing is subjected to circumferential soil pressure along the segment length. The axial force of the steel casing is determined by the horizontal static soil pressure, the segment length of the steel casing, and the wall thickness of the steel casing. Simulating the circumferential plate-like structure as an axially compressed member structure allows for a reasonable analysis of the internal force state of the steel casing, ensuring the accuracy of the calculation of the steel casing's instability process, and simplifying and facilitating subsequent calculations.

[0034] In step three, the moment of inertia of the steel casing section is I = bt. 3 / 12, radius of inertia Longer system In the formula, b is the length of the steel casing structure segment, A is the circumferential cross-sectional area of ​​the steel casing structure, d is the diameter of the steel casing structure, and t is the wall thickness of the steel casing.

[0035] In step four, the horizontal static earth pressure of the steel casing structure is q = Koγh, and the axial force of the compression member of the steel casing structure is N = qbd / 2. In these formulas, Ko is the static lateral pressure coefficient of the soil, determined according to different soil types; γ is the soil unit weight; h is the embedment depth of the steel casing structure; b is the segment length of the steel casing structure; and d is the diameter of the steel casing structure. Different soil types and embedment depths result in different static earth pressures on the steel casing structure. The static earth pressure on the steel casing in granular soil is less than that in clay, while the static earth pressure in dense granular soil is greater than that in loose granular soil. The static earth pressure in soft clay is greater than that in hard clay, and it is directly proportional to the embedment depth of the steel casing. The axial force N, equivalent to an axially compressed bar system, is directly proportional to the horizontal static earth pressure q, the segment length b of the steel casing structure, and the diameter d of the steel casing structure. The static lateral pressure coefficient Ko of the soil is determined according to different soil types: for loose granular soil, Ko is 0.5–0.6; for compact granular soil, Ko is 0.3–0.5; for soft clay, Ko is 0.9–1.0; and for hard clay, Ko is 0.8–0.9. The soil unit weight γ is taken as 18 kN / m³. 3 -22 kN / m 3 .

[0036] In step five, the critical stress for column stability σ´ is determined using Euler's formula: σ´=π 2 E / ελ 2ε is the stability coefficient, taken as ε=1.2, E is the elastic modulus of steel, taken as E=200Gpa, and the internal stress of the compression member is σ=N / A. When the internal stress of the compression member σ≤ the critical stress for stability of the compression member, we get σ= N / A= Koγhbd / 2bt= Koγhd / 2t≤π 2 E / ελ 2 =π 2 E / 1.2×5.4 2 (d / t) 2 =0.282E / (d / t) 2 The results are as follows: (d / t) 3 ≤2×0.282E / Koγh=0.564E / Koγh, therefore, In the formula, A is the circumferential cross-sectional area of ​​the steel casing structure, N is the axial force of the compression member of the steel casing structure, d is the diameter of the steel casing structure, Ko is the static lateral pressure coefficient of the soil, γ is the unit weight of the soil, h is the embedment depth of the steel casing structure, b is the segment length of the steel casing structure, d is the diameter of the steel casing structure, and t is the wall thickness of the steel casing. The formula for the ratio of the diameter to the wall thickness of the steel casing structure is calculated under the condition that the internal stress of the compression member of the steel casing structure is less than or equal to the critical stress for stability of the compression member. It is found that the ratio of the diameter to the wall thickness of the steel casing is related to the static lateral pressure of the soil and the elastic modulus of the steel, and is inversely proportional to the cube root of the embedment depth of the steel casing.

[0037] The explanation is based on a soil type consisting of a combination of soft and hard clay. The coefficient of lateral pressure at rest, Ko, is taken as 1.0, and the unit weight of the soil, γ, is taken as 20 kN / m³. 3 For different burial depths of steel casings, the following two calculation processes are given: ① The steel casing is buried at a depth of 2m: ; ②The steel casing is buried at a depth of 4m: .

[0038] In step six, based on the calculation results in step five, and after repeated verification, it is determined that: when the burial depth h of the steel casing structure is ≤ 2m, the ratio of the diameter to the wall thickness d / t of the steel casing structure ranges from 100 to 140; when the burial depth h is 2m < h ≤ 4m, the ratio of the diameter to the wall thickness d / t ranges from 80 to 120; and when the burial depth h > 4m, the ratio of the diameter to the wall thickness d / t ranges from 60 to 100. Based on the diameter of the steel casing structure, the wall thickness can be determined. Furthermore, the range of the diameter to wall thickness ratio d / t varies depending on the burial depth. The value closer to the upper or lower limit of the range is selected based on safety and economy. When prioritizing the economic efficiency of the steel casing structure construction, the preferred ratio of the diameter to the wall thickness d / t is [insert value here]. The value range is close to the lower limit of the interval. When the construction safety of the steel casing structure is more important, the preferred value range for the diameter-to-wall-thickness ratio d / t of the steel casing structure is close to the upper limit of the interval. Moreover, the deeper the burial depth, the smaller the value of the diameter-to-wall-thickness ratio d / t of the steel casing structure. Based on the different burial depths of the steel casing structure, the value range of the diameter-to-wall-thickness ratio d / t of the steel casing structure determined in this scheme can ensure both the construction safety of the steel casing structure and the economy of the steel casing structure selection.

[0039] Verify the above value range: First, the calculation is performed assuming the soil type is soft clay. The coefficient of lateral pressure at rest, Ko, is taken as 1.0, and the unit weight of the soil, γ, is taken as 22 kN / m³. 3For different burial depths of steel casings, the diameter-to-wall-thickness ratio (d / t) of multiple steel casing structures at burial depths of 1m, 2m, 3m, 4m, and 5m was calculated. The calculation results were: d / t=172, d / t=137, d / t=128, d / t=116, and d / t=108, respectively. It can be seen that when the burial depth h ≤ 2m, the maximum value of d / t is 137. In actual production, the value of Ko should be less than 1.0, and the soil unit weight γ should also be less than 22kN / m³. When both Ko and soil unit weight γ are at their maximum values, d / t reaches its maximum value of 137. Based on practical experience, when the burial depth h ≤ 2m, a diameter-to-wall-thickness ratio (d / t) of 100–140 fully meets the requirements. Similarly, when the burial depth h < 2m, the ratio is less than 2m. When the depth is ≤4m, the maximum value of d / t is 116. In actual production, the value of Ko should be less than 1.0, and the value of soil unit weight γ should also be less than 22kN / m3. When both Ko and soil unit weight γ are at their maximum upper limits, d / t is at its maximum value of 116. Based on practical experience, when the burial depth of the steel casing structure is 2m < h ≤ 4m, the range of the ratio of the diameter to the wall thickness of the steel casing structure, d / t, is 80 to 120, which fully meets the requirements. When the burial depth of the steel casing structure is h = 5m, the range of values ​​is met. In this embodiment, combined with the specification requirements for the burial depth of the steel casing structure, when the burial depth of the steel casing structure is h > 4m, the range of the ratio of the diameter to the wall thickness of the steel casing structure, d / t, is 60 to 100, which can meet the usage requirements. Secondly, the calculation was performed with granular soil as the soil type. The static lateral pressure coefficient Ko of the soil was taken as 0.4, and the soil unit weight γ was taken as 18 kN / m3. For different burial depths of the steel casing, the diameter-to-wall thickness ratio d / t of multiple steel casing structures at burial depths of 1m, 2m, 3m, 4m, and 5m were calculated respectively. The calculation results are: d / t=397, d / t=146, d / t=120, d / t=109, and d / t=101. From the calculation results, it can be seen that since the soil type is granular soil and the soil unit weight is low, all calculated parameter values ​​meet (or are better than) the value range requirements.

[0040] It is worth noting that in the actual calculation process, we can calculate based on the actual soil type and the monitored soil unit weight, and then obtain the range of wall thickness values ​​for the steel casing based on the diameter of the steel casing structure, so as to obtain the most economical optimized value while meeting the performance requirements.

[0041] As a further preferred embodiment, for common steel casing structures with an burial depth h≤2m, the wall thickness of the steel casing is selected according to d / t=120~140. This embodiment can further improve the economy of construction materials and construction process, while ensuring construction safety. Example 2

[0042] Figure 7 A module for calculating and determining the wall thickness of the steel casing for bored piles according to an exemplary embodiment of the present invention is shown, namely, an electronic device 3 (e.g., a computer component with program execution function), which includes at least one processor 31, a power supply 34, and a memory 32 and an input / output interface 33 communicatively connected to the at least one processor 31. The memory 32 stores instructions executable by the at least one processor 31, which are executed by the at least one processor 31 to enable the at least one processor 31 to perform the calculation process in the calculation and determination of the wall thickness of the steel casing for bored piles disclosed in the foregoing embodiments. The input / output interface 33 may include a display, a keyboard, a mouse, and a USB interface for inputting and outputting data, including multiple cross-sectional parameters of the steel casing structure, multiple horizontal static earth pressure parameters, multiple internal stress parameters of the compression members of the steel casing structure, and multiple critical stresses for stability of the compression members. The power supply 34 is used to provide electrical energy to the electronic device 3.

[0043] Those skilled in the art will understand that all or part of the steps of the above method embodiments can be implemented by hardware related to program instructions. The aforementioned program can be stored in a computer-readable storage medium. When the program is executed, it performs the steps of the above-described method embodiments for calculating and determining the wall thickness of the steel casing of bored piles. The aforementioned storage medium includes various media capable of storing program code, such as mobile storage devices, read-only memory (ROM), magnetic disks, or optical disks.

[0044] When the integrated computing unit of the present invention is implemented as a software functional unit and sold or used as an independent product, it can also be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the embodiments of the present invention, or the part that contributes to the prior art, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute all or part of the methods described in the various embodiments of the present invention. The aforementioned storage medium includes various media capable of storing program code, such as mobile storage devices, ROM, magnetic disks, or optical disks.

[0045] The above description is merely a detailed illustration of specific embodiments of the present invention and is not intended to limit the invention. Various substitutions, modifications, and improvements made by those skilled in the art without departing from the principles and scope of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for calculating and determining the wall thickness of steel casing for bored piles, comprising the following steps: Step 1: Based on the installation structure of the steel casing of the bored pile, analyze the mechanical model of the stress on the steel casing of the bored pile. Step 2: Based on the stress state of the steel casing, take a segment of the steel casing structure with a segment length of b, and unfold the steel casing structure of this segment into a plate-like structure along the circumferential direction. At the same time, simulate the circumferential plate-like structure as an axially compressed rod system structure and perform a simulation stability analysis. Step 3: Calculate the cross-sectional parameters of the steel casing structure in Step 2, including the moment of inertia, radius of inertia, and slenderness ratio. Step 4: Calculate the axial force of the compression members of the steel casing structure based on the horizontal static earth pressure of the steel casing structure; Step 5: When the internal stress of the compression member of the steel casing structure is less than or equal to the critical stress for stability of the compression member, the steel casing structure is stable in the circumferential direction and will not produce a failure mode. Based on the cross-sectional parameters of the steel casing structure in Step 3 and the axial force of the compression member of the steel casing structure in Step 4, the relationship between the diameter and thickness of the steel casing structure and the static lateral pressure of the soil and the burial depth of the steel casing is calculated. Step 6: Based on the embedment depth of the steel casing structure, the soil unit weight value, and the static lateral pressure coefficient of the soil, obtain the ratio of the diameter to the wall thickness of the steel casing structure, and then determine the wall thickness of the steel casing for the bored pile.

2. The method for calculating and determining the wall thickness of the steel casing for bored piles according to claim 1, characterized in that, In step two, the internal force state of the steel casing is set to be equivalent to the axial compression member of the steel casing structure with circumferential cross-sectional area, length and axial force N. Then, the circumferential plate structure is simulated as an axially compressed rod system structure. The circumferential cross-sectional area of ​​the steel casing structure is b×t, where b is the segment length of the steel casing structure, t is the wall thickness of the steel casing, and the length of the steel casing structure is π×d.

3. The method for calculating and determining the wall thickness of the steel casing for bored piles according to claim 2, characterized in that, In step three, the moment of inertia of the steel casing section is I=bt. 3 / 12, radius of inertia Longer system In the formula, b is the length of the steel casing structure segment, A is the circumferential cross-sectional area of ​​the steel casing structure, d is the diameter of the steel casing structure, and t is the wall thickness of the steel casing.

4. The method for calculating and determining the wall thickness of the steel casing for bored piles according to claim 3, characterized in that, In step four, the horizontal static earth pressure of the steel casing structure is q=Koγh, and the axial force of the compression member of the steel casing structure is N=qbd / 2, where Ko is the static lateral pressure coefficient of the soil, which is determined according to different soil types, γ is the soil unit weight, h is the embedment depth of the steel casing structure, b is the segment length of the steel casing structure, and d is the diameter of the steel casing structure.

5. The method for calculating and determining the wall thickness of the steel casing for bored piles according to claim 4, characterized in that, In step four, the static lateral pressure coefficient Ko of the soil is determined according to different soil types. For loose granular soil, Ko is 0.5 to 0.6; for compact granular soil, Ko is 0.3 to 0.5; for soft clay, Ko is 0.5 to 0.6; and for hard clay, Ko is 0.8 to 0.

9.

6. The method for calculating and determining the wall thickness of the steel casing for bored piles according to claim 4, characterized in that, In step four, the soil unit weight γ is taken as 18 kN / m³. 3 -22 kN / m 3 .

7. The method for calculating and determining the wall thickness of the steel casing for bored piles according to claim 4, characterized in that, In step five, the critical stress for stability of the compression bar, σ´, is determined using Euler's formula: σ´=π 2 E / ελ 2 ε is the stability coefficient, taken as ε=1.2, E is the elastic modulus of steel, taken as E=200Gpa, and the internal stress of the compression member is σ=N / A. When the internal stress of the compression member σ≤ the critical stress for stability of the compression member, we get σ= N / A= Koγhbd / 2bt= Koγhd / 2t≤π 2 E / ελ 2 =π 2 E / 1.2×5.4 2 (d / t) 2 =0.282E / (d / t) 2 The results are as follows: (d / t) 3 ≤2×0.282E / Koγh=0.564E / Koγh, therefore, In each formula, A is the circumferential cross-sectional area of ​​the steel casing structure, N is the axial force of the compression member of the steel casing structure, d is the diameter of the steel casing structure, Ko is the static lateral pressure coefficient of the soil, γ is the unit weight of the soil, h is the burial depth of the steel casing structure, b is the segment length of the steel casing structure, d is the diameter of the steel casing structure, and t is the wall thickness of the steel casing.

8. The method for calculating and determining the wall thickness of the steel casing for bored piles according to claim 7, characterized in that, In step six, when the burial depth h of the steel casing structure is ≤ 2m, the ratio of the diameter to the wall thickness d / t of the steel casing structure is in the range of 100 to 140; when the burial depth h is 2m < h ≤ 4m, the ratio of the diameter to the wall thickness d / t of the steel casing structure is in the range of 80 to 120; and when the burial depth h is > 4m, the ratio of the diameter to the wall thickness d / t of the steel casing structure is in the range of 60 to 100.

9. The method for calculating and determining the wall thickness of the steel casing for bored piles according to claim 8, characterized in that, For common steel casing structures with an burial depth h≤2m, the wall thickness of the steel casing should be selected according to d / t=120~140.

10. A module for calculating and determining the wall thickness of steel casing for bored piles, characterized in that, It includes at least one processor and a memory communicatively connected to the at least one processor; the memory stores instructions executable by the at least one processor, which, when executed by the at least one processor, enable the at least one processor to perform the calculation process in the method for calculating and determining the wall thickness of the steel casing for bored piles as described in any one of claims 1 to 9.

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