Method, device, equipment and medium for determining the spacing between composite piles under soil arching effect

Abstract

The present invention provides a method, device, equipment and medium for determining the spacing of composite piles under soil arch effect, belonging to the field of civil engineering, the method comprising: obtaining the physical parameters of target soil arch and composite pile; determining the soil arch curve trajectory according to the physical parameters of the composite pile; when the soil arch is in the limit equilibrium state, determining the first relationship between cohesion and internal friction angle and major principal stress according to Mohr-Coulomb theory; obtaining the axial force at the arch foot of the large pile through the soil arch curve trajectory and sliding force; determining the second relationship between axial force and major principal stress according to Mohr-Coulomb theory; determining the target relationship between the physical parameters of the target soil arch and composite pile and the pile spacing according to the first relationship and the second relationship, and then determining the pile spacing. In this way, the present invention comprehensively analyzes the physical parameters of the soil arch and the pile, comprehensively considers various influencing factors, ensures the scientificity and rationality of the pile spacing design, effectively prevents accidents caused by unreasonable pile spacing, and ensures the safe operation of the project.

Description

Technical Field

[0001] The invention belongs to the field of civil engineering, and in particular relates to a method, a device, equipment and a medium for determining the spacing between composite piles under soil arch effect. Background Art

[0002] With the continuous development of urban rail transit and high-rise buildings, foundations are becoming increasingly diversified. Common foundation pit support structures include internal support, pile-anchor support, and row pile support systems. In these support structures, as the foundation pit is excavated, the soil pressure inside the foundation pit is gradually released, causing the soil layer outside the foundation pit to move inward. The excavation of the foundation pit leads to a decrease in the soil pressure inside, thereby weakening the constraint of the soil layer outside the foundation pit. This reduced soil pressure will cause a series of complex movements in the soil layer, including deformation, displacement, and redistribution of internal stress. In this process, due to the destruction of the soil layer, the soil layer between the two supporting piles forms a soil arch effect, which forms a relatively stable soil arch structure outside the foundation pit. When designing the support structure, too large a pile spacing will weaken the support effect, while too small a pile spacing will lead to unnecessary over-support, which will cause the project cost to soar. Therefore, determining a reasonable pile spacing has become an important consideration in the design of foundation pit support.

[0003] At present, many scholars at home and abroad have conducted relevant research on the reasonable pile spacing. First, by constructing a mechanical analysis model of soil arch, taking the most unfavorable sections of the arch foot and arch top as the control conditions, the pile-stabilized soil arch problem is reduced to a zero-value problem, and the pile spacing and soil arch equation are determined by solving nonlinear equations. The soil pressure of sheet piles is calculated by the soil arch equation, and the calculation is performed using a reasonable arch axis and integral method. The rationality of this method has been verified in engineering examples. The results show that under different damage control conditions of soil arch effect, the soil pressure calculated by the proposed method is appropriate and suitable for the design of sheet piles. By combining the Meyerhof pile foundation theory and the cavity expansion method, a method for calculating the optimal pile spacing is proposed by comprehensively considering the mechanical and physical properties of sand such as stiffness, strength, compressibility and particle size. Secondly, the generalized landslide model is used to consider the interaction between multi-layer sliders, and the equation of landslide stability coefficient is improved. By using the finite difference method, the distribution of vertical landslide driving force and horizontal load between adjacent piles is deeply studied, and a calculation method for pile spacing is proposed based on the simulation result data. Then, a novel soil arch model with three-dimensional soil arch quality characteristics is adopted. By assuming that the soil arch height remains constant along the vertical direction and the inclination angle of the soil arch is not affected by the friction angle of the soil, the residual driving force of the rear soil is used as the load on the stabilizing pile, while the load on the retaining wall is the larger of the Coulomb active earth pressure caused by the sliding wedge before the soil arch is formed or the residual sliding force generated by the front soil. On this basis, a simplified method is proposed to consider the soil arch effect under different conditions (including the soil arch axis located before and after the top of the active failure surface) to calculate the load acting on the stabilizing pile and the retaining wall respectively. This method can be used to determine the pile spacing in the composite retaining wall. In the study of cantilever anti-sliding piles, an innovative method is proposed by applying the natural equilibrium arch theory and the influence of lateral earth pressure. By deriving a reasonable arch axis equation, considering the arch shape as an elliptic curve, taking the arch foot and arch top as the control conditions for stable soil arch, and introducing an appropriate safety factor, the soil arch problem of anti-sliding piles is transformed into a zero value extreme value problem of unconstrained nonlinear functions. By adopting the integral method, the earth pressure value on the pile plate and the pile spacing are accurately determined.

[0004] However, most existing studies focus on the calculation of pile spacing for soil arching effect formed by piles of the same size. For composite pile structures consisting of cast-in-place concrete piles and micro-grouted steel pipe piles, there has been no detailed study on the pile spacing. Summary of the invention

[0005] In order to solve the above-mentioned problem of determining the spacing between composite piles consisting of cast-in-place concrete piles and micro-grouting steel pipe piles, the present invention provides a method, device, equipment and medium for determining the spacing between composite piles under soil arch effect.

[0006] In order to achieve the above object, the present invention provides the following technical solutions:

[0007] In a first aspect, the present invention provides a method for determining the spacing between composite piles under soil arching effect, comprising the following steps:

[0008] The physical parameters of the target soil arch and composite pile are obtained; the physical parameters of the target soil arch include cohesion, internal friction angle and sliding force; the physical parameters of the composite pile include the large pile diameter and the small pile diameter of the composite pile, the large pile is a concrete cast-in-place pile of the composite pile, and the small pile is a micro-grouting steel pipe pile of the composite pile; the soil arch curve trajectory is constructed according to the large pile diameter and the small pile diameter of the composite pile; when the soil arch is in a limit equilibrium state, the first relationship between the cohesion and the internal friction angle and the major principal stress is determined according to the Mohr-Coulomb theory; the axial force at the arch foot of the large pile is obtained through the soil arch curve trajectory and the sliding force; the second relationship between the axial force and the major principal stress is determined according to the Mohr-Coulomb theory; according to the first relationship and the second relationship, the target relationship between the physical parameters of the target soil arch and the composite pile and the pile spacing is determined, and then the pile spacing is determined according to the target relationship and the physical parameters of the target soil arch and the composite pile.

[0009] Optionally, before constructing the soil arch curve trajectory according to the large pile diameter and the small pile diameter of the composite pile, the soil arch is simplified into an ideal model, and the simplification of the ideal model includes the following steps: the shape of the soil arch is equivalent to a semi-oval line; the sliding force of the soil arch behind the pile is a uniformly distributed load; the deadweight and sliding resistance of the soil arch are ignored; the soil arch is evenly distributed along the pile body of the composite pile, and the shape does not change.

[0010] Optionally, the first relational expression is as follows:

[0011]

[0012] in, is the internal friction angle, c is the cohesion, σ C is the major principal stress.

[0013] Optionally, the axial force is determined by the following formula:

[0014]

[0015] Among them, F Ax ' is the horizontal force at the large pile arch foot, F Ay ' is the vertical force at the large pile arch foot, F A ' is the axial force at the arch foot of the large pile, q is the sliding force, L1 is the distance between the arch foot of the large pile and the center of the semi-oval line, L2 is the distance between the arch foot of the small pile and the center of the semi-oval line, and f is the distance between the highest point of the soil arch and the horizontal plane.

[0016] Optionally, the second relationship between the axial force and the major principal stress determined according to the Mohr-Coulomb theory includes:

[0017] When the target soil arch is in a limit equilibrium state, the slope of the tangent of the soil arch curve trajectory at the large pile arch foot is obtained; the angle between the tangent and the horizontal line is determined according to the slope of the tangent; the angle is the angle between the maximum principal stress action surface and the fracture surface; the ultimate shear strength thickness of the soil arch is characterized by the angle and the large pile diameter; the axial force is characterized by the sliding force; and then the second relationship between the sliding force, the angle, the large pile diameter and the maximum principal stress is determined.

[0018] Optionally, determining the angle between the tangent and the horizontal line according to the tangent slope includes: when the target soil arch is in a limit equilibrium state, the angle between the maximum principal stress action surface of the soil arch and the fracture surface is That is, the angle is The angle between the tangent line and the horizontal line is determined by the following formula:

[0019]

[0020] Among them, β is the angle.

[0021] Optionally, when the target soil arch is in a limit equilibrium state, the second relationship is as follows:

[0022]

[0023] Where, t is the ultimate shear strength thickness of the soil arch;

[0024] The ultimate shear strength thickness of the soil arch characterized by the angle and the large pile diameter is:

[0025]

[0026] Then the second relationship between the sliding force, angle, large pile diameter and large principal stress is determined:

[0027]

[0028] Among them, b1 is the diameter of the large pile.

[0029] In a second aspect, the present invention provides a device for determining the spacing between composite piles under soil arching effect, comprising:

[0030] An acquisition module is used to acquire physical parameters of a target soil arch and a composite pile; the physical parameters of the target soil arch include cohesion, internal friction angle and sliding force; the physical parameters of the composite pile include a large pile diameter and a small pile diameter of the composite pile, the large pile is a concrete cast-in-place pile of the composite pile, and the small pile is a micro-grouting steel pipe pile of the composite pile;

[0031] A determination module is used to construct a soil arch curve trajectory according to the large pile diameter and the small pile diameter of the composite pile; when the soil arch is in a limit equilibrium state, determine the first relationship between cohesion and internal friction angle and the major principal stress according to the Mohr-Coulomb theory; obtain the axial force at the arch foot of the large pile through the soil arch curve trajectory and the sliding force; determine the second relationship between the axial force and the major principal stress according to the Mohr-Coulomb theory; determine the target relationship between the physical parameters of the target soil arch and the composite pile and the pile spacing according to the first and second relationship, and then determine the pile spacing according to the target relationship and the physical parameters of the target soil arch and the composite pile.

[0032] Optionally, before constructing the soil arch curve trajectory according to the large pile diameter and the small pile diameter of the composite pile, the soil arch is simplified into an ideal model, and the simplification of the ideal model includes the following steps: the shape of the soil arch is equivalent to a semi-oval line; the sliding force of the soil arch behind the pile is a uniformly distributed load; the deadweight and sliding resistance of the soil arch are ignored; the soil arch is evenly distributed along the pile body of the composite pile, and the shape does not change.

[0033] Optionally, the first relational expression is as follows:

[0034]

[0035] in, is the internal friction angle, c is the cohesion, σ C is the major principal stress.

[0036] Optionally, the axial force is determined by the following formula:

[0037]

[0038]

[0039] Among them, F Ax ' is the horizontal force at the large pile arch foot, F Ay ' is the vertical force at the large pile arch foot, F A ' is the axial force at the arch foot of the large pile, q is the sliding force, L1 is the distance between the arch foot of the large pile and the center of the semi-oval line, L2 is the distance between the arch foot of the small pile and the center of the semi-oval line, and f is the distance between the highest point of the soil arch and the horizontal plane.

[0040] Optionally, the determination module is also used to obtain the slope of the tangent of the soil arch curve trajectory at the large pile arch foot when the target soil arch is in a limit equilibrium state; determine the angle between the tangent and the horizontal line according to the tangent slope; the angle is the angle between the maximum principal stress action surface and the fracture surface; characterize the ultimate shear strength thickness of the soil arch by the angle and the large pile diameter; characterize the axial force by the sliding force; and then determine the second relationship between the sliding force, the angle, the large pile diameter and the maximum principal stress.

[0041] Optionally, the determination module is further configured to determine, when the target soil arch is in a limit equilibrium state, the angle between the maximum principal stress action surface of the soil arch and the fracture surface is That is, the angle is The angle between the tangent line and the horizontal line is determined by the following formula:

[0042]

[0043] Among them, β is the angle.

[0044] Optionally, when the target soil arch is in a limit equilibrium state, the second relationship is as follows:

[0045]

[0046] Where, t is the ultimate shear strength thickness of the soil arch;

[0047] The ultimate shear strength thickness of the soil arch characterized by the angle and the large pile diameter is:

[0048]

[0049]

[0050] Then the second relationship between the sliding force, angle, large pile diameter and large principal stress is determined:

[0051]

[0052] Among them, b1 is the diameter of the large pile.

[0053] The method for determining the spacing between composite piles under soil arching effect provided by the present invention has the following beneficial effects:

[0054] Through in-depth analysis of the cohesion and internal friction angle of the soil arch, the utilization of the soil arch effect is optimized, the bearing capacity of the soil arch between piles is significantly improved, and the risk of soil arch failure is reduced; and through systematic analysis and optimization calculation of the major principal stress of the soil arch, the optimal pile spacing is reasonably determined, which reduces material and construction costs and improves economic benefits while ensuring project safety. In addition, accurate calculation of pile spacing also reduces uncertainty and repeated adjustments during construction, simplifies the construction process, shortens the construction period, and improves construction efficiency. In addition, the physical parameters of the soil arch and piles are comprehensively analyzed, and various influencing factors are comprehensively considered to ensure the scientificity and rationality of the pile spacing design, effectively prevent engineering accidents caused by unreasonable pile spacing, and ensure the long-term safe operation of the project. BRIEF DESCRIPTION OF THE DRAWINGS

[0055] In order to more clearly illustrate the embodiment of the present invention and its design scheme, the following briefly introduces the drawings required for this embodiment. The drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0056] Figure 1 This is a flow chart of a method for determining the spacing between composite piles under soil arching effect provided by the present invention according to an exemplary embodiment.

[0057] Figure 2 It is a schematic plan view of a soil arch provided according to an exemplary embodiment of the present invention.

[0058] Figure 3 A schematic diagram of the Mohr-Coulomb theory provided by the present invention according to an exemplary embodiment.

[0059] Figure 4 A force analysis diagram of a soil arch provided according to an exemplary embodiment of the present invention.

[0060] Figure 5 It is a schematic diagram of soil arch behind large piles according to an exemplary embodiment of the present invention.

[0061] Figure 6 It is a block diagram of a device for determining the spacing between composite piles under soil arching effect according to an exemplary embodiment of the present invention.

[0062] Figure 7 A schematic diagram of a computer device for implementing a method for determining the spacing between composite piles under soil arching effect provided by the present invention according to an exemplary embodiment. DETAILED DESCRIPTION

[0063] In order to enable those skilled in the art to better understand the technical solution of the present invention and implement it, the present invention is described in detail below in conjunction with the accompanying drawings and specific embodiments. The following embodiments are only used to more clearly illustrate the technical solution of the present invention, and cannot be used to limit the scope of protection of the present invention.

[0064] First, the application scenario of the present invention is explained. The present invention is used to determine the pile spacing of composite pile support in civil engineering. Considering the composite pile support structure such as concrete cast-in-place piles and micro-grouting steel pipe piles, the method for determining the reasonable pile spacing is discussed. Drawing on the research results of predecessors, by assuming that the soil arch formed by the composite pile is semi-ovate linear, and considering the distribution of the sliding force of the soil arch behind the pile, a calculation model of the soil arch of the composite pile support foundation pit is established, thereby determining the reasonable arch axis of the composite pile support. Combined with the limit equilibrium theory and the Moore-Coulomb criterion, the pile spacing of the composite pile support foundation pit is determined.

[0065] A simplified model of semi-ovate linear soil arch is constructed by considering the composite pile support structure and the distribution of soil arch sliding force behind the pile. Based on the static equilibrium condition and limit equilibrium theory, the calculation model of soil arch of composite pile support foundation pit is successfully established, and the corresponding pile spacing calculation formula is derived. The accuracy and reliability of this method are verified by actual engineering cases. For key factors such as cohesion, internal friction angle and landslide thrust, a systematic analysis is carried out to reveal the influence of these factors on pile spacing. The research results show that with the increase of cohesion, the pile spacing tends to increase; the increase of internal friction angle tends to increase nonlinearly; and the increase of landslide thrust leads to a decrease in pile spacing. The pile spacing calculation formula proposed in this invention is not only applicable to composite pile support foundation pits, but also to the calculation of pile spacing of piles of the same size, showing strong versatility and applicability. This provides a reliable theoretical basis for engineering practice and plays a positive role in the safe and economic design of composite pile support structures.

[0066] The specific embodiments of the present disclosure are described in detail below with reference to the accompanying drawings.

[0067] First, the present invention provides a method for determining the spacing between composite piles under soil arching effect, such as Figure 1 As shown, the following steps are included:

[0068] S101. Obtain physical parameters of target soil arch and composite pile.

[0069] Among them, the physical parameters of the target soil arch include cohesion, internal friction angle and sliding force; the physical parameters of the composite pile include the large pile diameter and the small pile diameter of the composite pile, the large pile is a concrete cast-in-place pile of the composite pile, and the small pile is a micro-grouting steel pipe pile of the composite pile.

[0070] S102: construct a soil arch curve trajectory according to the large pile diameter and the small pile diameter of the composite pile.

[0071] In order to facilitate calculation, the soil arch is simplified into an ideal model before determining the trajectory of the soil arch curve according to the physical parameters of the composite pile.

[0072] Specifically, the pipe piles in the composite piles are equivalent to square piles of different widths. The pile diameters of the pipe piles in the composite piles are D and d, respectively. The height of the soil arch is h, and the pile spacing is L. In order to simplify the soil arch pattern, the following assumptions are made to construct an ideal model: (1) The shape of the soil arch formed by the composite piles composed of large piles and small piles is a semi-oval line. (2) The sliding force of the soil arch behind the pile is a uniformly distributed load. (3) The deadweight and sliding resistance of the soil arch are ignored. (4) The soil arch is evenly distributed along the pile body of the composite pile, and its shape does not change.

[0073] The plan view of soil arch is as follows: Figure 2As shown. The pipe pile of the composite pile is equivalent to a square pile, and a plane coordinate system is constructed with the center of the semi-oval line as the origin. The diameter of the large pile is D, the diameter of the small pile is d, the side length of the equivalent large pile is b1, the side length of the equivalent small pile is b2, the center distance between the large pile and the small pile is L, and the arch height of the soil arch is f. From the above content, it can be seen that the soil arch curve passes through three points: A (-L1, 0), B (-L2, 0), and C (0, f).

[0074] In order to ensure that the pipe piles in the composite piles have similar bearing capacity as the equivalent square piles, the mass and material usage of the square piles and pipe piles must be equal. That is, the volume of the pipe pile is equal to the volume of the square pile, and the equality of the pile lengths means that their bottom areas should also be equal. To achieve this equal volume condition, based on this equivalence construction, the side length of the equivalent square pile can be calculated using the following formula:

[0075]

[0076] Similarly, we can get:

[0077]

[0078] Thus, the distances from the equivalent large and small piles to the origin O can be obtained:

[0079]

[0080] Among them, L1 is the distance between the arch foot of the large pile and the origin, and L2 is the distance between the arch foot of the small pile and the origin.

[0081] The soil arch curve passes through three key points, namely A (-L1, 0), B (L2, 0), and C (0, h). The positional relationship of these three points on the plane reveals the shape and behavior of the soil arch in the composite pile system. Point A and point B correspond to the two sides of the bottom of the soil arch, respectively, while point C represents the top of the soil arch. By connecting these three key points, the present invention obtains a soil arch curve, and its trajectory can be further expressed as:

[0082]

[0083] Where f is the distance between the highest point of the soil arch and the horizontal plane.

[0084] S103. When the soil arch is in a limit equilibrium state, determine the first relationship between cohesion, internal friction angle and major principal stress according to Mohr-Coulomb theory.

[0085] In soil arch structures, the arch foot section is considered to be the most vulnerable area. According to the uniaxial compression condition of Mohr-Coulomb theory, when the stress of the soil arch unit on the pile side reaches the limit equilibrium state, the strength envelope is tangent to the stress circle at point C. Figure 3From the derivation of the geometric relationship in, we can see that the first relationship is as follows:

[0086]

[0087] in, is the internal friction angle, c is the cohesion, σ C is the major principal stress.

[0088] S104. Obtain the axial force at the large pile arch foot through the soil arch curve trajectory and the sliding force, and determine the second relationship between the axial force and the major principal stress based on the Mohr-Coulomb theory.

[0089] Specifically, when the target soil arch is in a limit equilibrium state, the slope of the tangent of the soil arch curve trajectory at the large pile arch foot is obtained; the angle between the tangent and the horizontal line is determined according to the tangent slope; the angle is the angle between the maximum principal stress action surface and the fracture surface.

[0090] Figure 4 The force analysis diagram of soil arch is shown in the figure. It can be seen from the figure that any point M(F x ,F y ), F x is the horizontal force of soil arch at point M, F y is the vertical force of the soil arch at point M. At the arch foot, F x ' is the horizontal force at the arch foot, F y ' is the vertical force at the arch foot. According to the equilibrium condition, it can be calculated:

[0091]

[0092] Among them, F Ax ' is the horizontal force at the large pile arch foot, F Ay ' is the vertical force at the large pile arch foot, F A ' is the axial force at the large pile arch foot, and q is the sliding force.

[0093] In the soil arch structure, the angle between the tangent line at point A of the soil arch foot and the horizontal line is β. Through mathematical calculation, the slope of the tangent line can be obtained. The specific expression is as follows:

[0094]

[0095] According to the limit equilibrium theory, when the target soil arch is in the limit equilibrium state, the angle between the maximum principal stress action surface and the fracture surface is That is, the angle β is Since A(-L1,0), the slope of the tangent line is:

[0096]

[0097] Then, the angle between the tangent line and the horizontal line is determined based on the slope through inverse trigonometric functions.

[0098] The soil arch compression area behind the large pile is as follows Figure 5 According to the prior art, a compression zone ADF will be formed behind the pile, where the angle between AD and AF is t represents the ultimate shear strength thickness of the soil arch. When the target soil arch is in the limit equilibrium state, the second relationship can be obtained according to the Mohr-Coulomb criterion:

[0099]

[0100] The ultimate shear strength thickness of the soil arch characterized by this angle and the large pile diameter is:

[0101]

[0102] The sliding force is used to characterize the axial force, and then the second relationship between the sliding force, the angle, the large pile diameter and the large principal stress is determined:

[0103]

[0104] S105, determining a target relationship between the physical parameters of the target soil arch and the composite pile and the pile spacing according to the first relationship and the second relationship, and then determining the pile spacing according to the target relationship and the physical parameters of the target soil arch and the composite pile.

[0105] Specifically, an equivalent relationship between the first relational expression and the second relational expression is constructed, namely:

[0106]

[0107] Further substitute the above formula to derive:

[0108]

[0109] Therefore, the center distance between the composite piles of large piles and small piles can be expressed as:

[0110]

[0111] Where L is the pile spacing.

[0112] The equivalent large pile diameter is restored, and the target relationship is finally obtained:

[0113]

[0114] When the cohesion, internal friction angle and sliding force of the target soil arch as well as the large pile diameter and small pile diameter of the composite pile are known, the pile spacing can be obtained by substituting the above target relationship into the above target relationship.

[0115] By adopting the above method, through in-depth analysis of the cohesion and internal friction angle of the soil arch, the utilization of the soil arch effect can be optimized, the bearing capacity of the soil arch between piles can be significantly improved, and the risk of soil arch failure can be reduced; and by using systematic analysis and optimization calculation of the major principal stress of the soil arch, the optimal pile spacing can be reasonably determined, while ensuring the safety of the project, reducing material and construction costs and improving economic benefits. In addition, accurate calculation of the pile spacing can also reduce uncertainty and repeated adjustments during the construction process, simplify the construction process, shorten the construction period, and improve construction efficiency. In addition, the physical parameters of the soil arch and piles are comprehensively analyzed, and various influencing factors are comprehensively considered to ensure the scientificity and rationality of the pile spacing design, effectively prevent engineering accidents caused by unreasonable pile spacing, and ensure the long-term safe operation of the project.

[0116] In addition, in order to further verify the technical solution of the present invention and ensure the effectiveness of the proposed method for calculating the pile spacing of the composite pile support foundation pit, the pile spacing is compared by taking an actual project as an example.

[0117] Example 1: A composite pile support of large and small piles is used to support the foundation pit in a certain place. The soil behind the piles is mainly strongly weathered quartzite. According to the survey report, the average bulk density of the strongly weathered quartzite behind the piles is 23kN / m3, the cohesion c is 100kPa, and the friction angle is 35°. The diameter of the large pile is 0.8m, the diameter of the small pile is 0.168m, the pile length is 27.3m, the cantilever section is 20m, and the landslide thrust acting on the unit thickness soil arch is 124.65kPa.

[0118] According to the above pile spacing determination formula, the pile spacing can be obtained:

[0119]

[0120] According to the formula, the pile center distance is 2.61m, and the distance between large piles and small piles in actual projects is 1.25m.

[0121] Example 2: In order to verify the applicability of the pile spacing calculation method for composite pile-supported foundation pits to pile-supported foundation pits of the same diameter, it is known that the average bulk density of the soil behind the piles in a certain area is 20kN / m3, the cohesion c is 50kPa, the internal friction angle is 28°, the piles used are concrete square piles with a size of 2×3×22m, the cantilever length is 11m, and the landslide thrust behind the piles is 1050kN / m. According to Formula 2, the present invention can convert it into a pipe pile of the same diameter, and the diameter of the pile is The pile spacing can be obtained by the above pile spacing determination formula:

[0122]

[0123] Through calculation, it is found that when the same pile diameter is supported, the center spacing of the piles is 6.72m. It is worth noting that in the actual project, the center spacing of the piles is 6m, and after the completion of the project, the support structure performed well and no collapse occurred. This result further verifies that the pile spacing calculation method for composite pile support foundation pit is applicable to projects with the same diameter support to a certain extent. Compared with the pile spacing values ​​obtained by other researchers using different calculation methods, the result calculated by the scheme of the present invention is 6.72m, which is consistent with the actual value of the actual project.

[0124] In order to study the influence of the diameter of small piles in composite pile support pit on the pile spacing when considering factors such as soil cohesion, internal friction angle and landslide thrust, the specific parameter settings include the pile diameter D of the large pile is 0.8m, the internal friction angle of strongly weathered quartzite is 35°, and the landslide thrust is 124.65kPa. The pile diameters d of the small piles are 0.168m, 0.24m, 0.32m, 0.48m, 0.64m, and 0.8m respectively.

[0125] In this study, the effects of cohesion, internal friction angle, and landslide thrust on the pile spacing are analyzed.

[0126] By observing the collected data, the following conclusions can be drawn: when the diameter of the small pile is 0.168m, the pile spacing increases linearly with the increase of cohesion. This is because greater cohesion means that the soil arch has a higher shear strength, thereby enhancing its ability to resist the collapse of the soil arch behind the pile, so the pile spacing can be increased accordingly. In addition, it can be seen that as the diameter of the small pile increases, the pile spacing also gradually increases.

[0127] There is an increasing curve relationship between the pile spacing and the internal friction angle. As the internal friction angle increases, the pile spacing gradually expands. The increase in the friction angle makes the pile spacing more sensitive to its changes. This is because when the internal friction angle increases, the internal shear strength of the soil arch also increases, that is, the soil arch's resistance to the horizontal direction is enhanced. This makes the soil arch more able to resist lateral displacement under the same landslide thrust. On the other hand, a larger internal friction angle also indicates that the soil arch has a stronger lateral support effect on the pile, thereby reducing the mutual influence between piles.

[0128] As the thrust of the landslide increases, the distance between piles decreases gradually. In particular, when the thrust of the landslide increases from 50kPa to 150kPa, the distance between piles decreases suddenly; when the thrust of the landslide exceeds 150kPa, the speed of the distance between piles decreases relatively slowly. This is because in the composite pile support foundation pit, when the thrust of the landslide is small, the lateral thrust of the soil arch on the supporting structure is relatively small, and the distance between piles can be relatively large to meet the stability requirements of the supporting structure. However, as the thrust of the landslide increases, the lateral thrust of the soil arch on the supporting structure also increases, causing the supporting structure to be subjected to greater horizontal forces, which in turn causes the distance between piles to decrease. When the thrust of the landslide increases to 150kPa, due to the sharp increase in the lateral thrust of the soil arch, the horizontal force borne by the supporting structure will reach a critical point, resulting in a sudden decrease in the distance between piles. This is because the bearing capacity of the piles is limited and cannot withstand excessive horizontal forces. Therefore, at this critical point, the distance between piles will decrease rapidly to enhance the stability of the supporting structure. When the landslide thrust exceeds 150 kPa, although the lateral thrust of the soil arch on the supporting structure continues to increase, the initial arrangement of the piles is relatively tight, and the effect of the increased thrust on the pile spacing is relatively small, so the reduction rate of the pile spacing is relatively slow.

[0129] This verification result further consolidates the reliability and applicability of the calculation method of the present invention from the perspective of different cohesion, internal friction angle, and landslide thrust. The scheme proposed by the present invention can not only show characteristics closer to the actual situation than the existing methods under the same pile size conditions, but also calculate the pile spacing of the composite pile (large pile and small pile) supporting the foundation pit. It provides a more comprehensive and reliable theoretical basis for pile support design.

[0130] Secondly, the present invention provides a device for determining the spacing between composite piles under soil arching effect, such as Figure 6 As shown, including:

[0131] The acquisition module 601 is used to acquire the physical parameters of the target soil arch and the composite pile; the physical parameters of the target soil arch include cohesion, internal friction angle and sliding force; the physical parameters of the composite pile include the large pile diameter and the small pile diameter of the composite pile, the large pile is a concrete cast-in-place pile of the composite pile, and the small pile is a micro-grouting steel pipe pile of the composite pile.

[0132] Determination module 602 is used to construct a soil arch curve trajectory according to the large pile diameter and the small pile diameter of the composite pile; when the soil arch is in a limit equilibrium state, determine the first relationship between cohesion and internal friction angle and the major principal stress according to the Mohr-Coulomb theory; obtain the axial force at the arch foot of the large pile through the soil arch curve trajectory and the sliding force; determine the second relationship between the axial force and the major principal stress according to the Mohr-Coulomb theory; determine the target relationship between the physical parameters of the target soil arch and the composite pile and the pile spacing according to the first relationship and the second relationship, and then determine the pile spacing according to the target relationship and the physical parameters of the target soil arch and the composite pile.

[0133] Optionally, before constructing the soil arch curve trajectory according to the large pile diameter and the small pile diameter of the composite pile, the soil arch is simplified to an ideal model, and the simplification of the ideal model includes the following steps: the shape of the soil arch is equivalent to a semi-oval line; the sliding force of the soil arch behind the pile is a uniformly distributed load; the deadweight and sliding resistance of the soil arch are ignored; the soil arch is evenly distributed along the pile body of the composite pile, and the shape does not change.

[0134] Optionally, the first relation is as follows:

[0135]

[0136] in, is the internal friction angle, c is the cohesion, σ C is the major principal stress.

[0137] Alternatively, the axial force is determined by the following formula:

[0138]

[0139] Among them, F Ax ' is the horizontal force at the large pile arch foot, F Ay ' is the vertical force at the large pile arch foot, F A ' is the axial force at the arch foot of the large pile, q is the sliding force, L1 is the distance between the arch foot of the large pile and the center of the semi-oval line, L2 is the distance between the arch foot of the small pile and the center of the semi-oval line, and f is the distance between the highest point of the soil arch and the horizontal plane.

[0140] Optionally, the determination module 602 is also used to obtain the slope of the tangent of the soil arch curve trajectory at the large pile arch foot when the target soil arch is in a limit equilibrium state; determine the angle between the tangent and the horizontal line according to the tangent slope; the angle is the angle between the maximum principal stress action surface and the fracture surface; characterize the ultimate shear strength thickness of the soil arch by the angle and the large pile diameter; characterize the axial force by the sliding force; and then determine the second relationship between the sliding force, the angle, the large pile diameter and the maximum principal stress.

[0141] Optionally, the determination module is further configured to determine, when the target soil arch is in a limit equilibrium state, the angle between the maximum principal stress action surface of the soil arch and the fracture surface is That is, the angle is The angle between the tangent line and the horizontal line is determined by the following formula:

[0142]

[0143] Among them, β is the angle.

[0144] Optionally, when the target soil arch is in a limit equilibrium state, the second relationship is as follows:

[0145]

[0146] Where, t is the ultimate shear strength thickness of the soil arch;

[0147] The ultimate shear strength thickness of the soil arch characterized by this angle and the large pile diameter is:

[0148]

[0149] Then the second relationship between the sliding force, angle, large pile diameter and large principal stress is determined:

[0150]

[0151] Where b1 is the equivalent side length of the large pile diameter.

[0152] By adopting the above-mentioned device, through in-depth analysis of the cohesion and internal friction angle of the soil arch, the utilization of the soil arch effect can be optimized, the bearing capacity of the soil arch between piles can be significantly improved, and the risk of soil arch failure can be reduced; and by adopting systematic analysis and optimization calculation of the major principal stress of the soil arch, the optimal pile spacing can be reasonably determined, while ensuring the safety of the project, reducing material and construction costs and improving economic benefits. In addition, accurate calculation of the pile spacing also reduces uncertainty and repeated adjustments during the construction process, simplifies the construction process, shortens the construction period, and improves construction efficiency. In addition, the physical parameters of the soil arch and the piles are comprehensively analyzed, and various influencing factors are comprehensively considered to ensure the scientificity and rationality of the pile spacing design, effectively prevent engineering accidents caused by unreasonable pile spacing, and ensure the long-term safe operation of the project.

[0153] The present invention also provides a computer-readable storage medium, which stores a computer program, which can be used to execute the above Figure 1 A method for determining the spacing between composite piles under soil arching effect is provided.

[0154] The present invention also provides a computer device, such as Figure 7 As shown in the figure, at the hardware level, the computer device includes a processor, an internal bus, a network interface, a memory, and a non-volatile memory, and may also include other hardware required for the business. The processor reads the corresponding computer program from the non-volatile memory into the memory and then runs it to achieve the above Figure 1 A method for determining the spacing between composite piles under soil arching effect is provided.

[0155] Those skilled in the art will appreciate that embodiments of the present invention may be provided as methods, systems, or computer program products. Therefore, the present invention may take the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware. Moreover, the present invention may take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0156] The present invention is described with reference to flowcharts and / or block diagrams of methods, apparatus (systems) and computer program products according to embodiments of the present invention. It should be understood that each process and / or block in the flowchart and / or block diagram, as well as a combination of processes and / or blocks in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor or other programmable data processing device to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the process in the flowchart. Figure 1 A process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0157] These computer program instructions may also be stored in a computer-readable memory capable of directing a computer or other programmable data processing device to operate in a specific manner, so that the instructions stored in the computer-readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 A process or multiple processes and / or boxes Figure 1 A function specified in one or more boxes.

[0158] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operating steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing instructions for implementing the process. Figure 1 A process or multiple processes and / or boxes Figure 1 The steps for the functions specified in one or more boxes.

[0159] It should be noted that the above specific implementation method can enable those skilled in the art to understand the invention more comprehensively, but does not limit the invention in any way. Therefore, although the present invention has been described in detail in this specification, those skilled in the art should understand that the invention can still be modified or replaced by equivalents; and all technical solutions and improvements that do not deviate from the spirit and scope of the invention are included in the protection scope of the patent for the invention. Any figure mark in the claims should not be regarded as limiting the claims involved.

Claims

1. A method for determining the spacing between composite piles under soil arching effect, characterized in that: The following steps are involved: Obtaining physical parameters of the target soil arch and the composite pile; the physical parameters of the target soil arch include cohesion, internal friction angle and sliding force; the physical parameters of the composite pile include the large pile diameter and the small pile diameter of the composite pile, the large pile is a concrete cast-in-place pile of the composite pile, and the small pile is a micro-grouting steel pipe pile of the composite pile; The soil arch curve trajectory is constructed according to the large pile diameter and small pile diameter of the composite pile; When the soil arch is in a limit equilibrium state, a first relationship between cohesion and internal friction angle and major principal stress is determined according to Mohr-Coulomb theory; The axial force at the large pile arch foot is obtained through the soil arch curve trajectory and sliding force; the second relationship between the axial force and the major principal stress is determined according to the Mohr-Coulomb theory; According to the first and second relationship equations, a target relationship equation between the physical parameters of the target soil arch and composite piles and the pile spacing is determined, and then the pile spacing is determined according to the target relationship equation and the physical parameters of the target soil arch and composite piles.

2. The method for determining the spacing between composite piles under soil arching effect according to claim 1, characterized in that: Before constructing the soil arch curve trajectory according to the large pile diameter and the small pile diameter of the composite pile, the soil arch is simplified into an ideal model. The simplification of the ideal model includes the following steps: The shape of the soil arch is equivalent to a semi-oval line; the sliding force of the soil arch behind the pile is a uniformly distributed load; the deadweight and sliding resistance of the soil arch are ignored; the soil arch is evenly distributed along the body of the composite pile and its shape does not change.

3. The method for determining the spacing between composite piles under soil arching effect according to claim 2 is characterized in that: The first relationship is as follows: in, is the internal friction angle, c is the cohesion, σ C is the major principal stress.

4. The method for determining the spacing between composite piles under soil arching effect according to claim 3 is characterized in that: The axial force is determined by the following formula: Among them, F Ax ' is the horizontal force at the large pile arch foot, F Ay ' is the vertical force at the large pile arch foot, F A ' is the axial force at the arch foot of the large pile, q is the sliding force, L1 is the distance between the arch foot of the large pile and the center of the semi-oval line, L2 is the distance between the arch foot of the small pile and the center of the semi-oval line, and f is the distance between the highest point of the soil arch and the horizontal plane.

5. The method for determining the spacing between composite piles under soil arching effect according to claim 4 is characterized in that: The second relationship between the axial force and the major principal stress determined by Mohr-Coulomb theory includes: When the target soil arch is in a limit equilibrium state, the slope of the tangent of the soil arch curve trajectory at the large pile arch foot is obtained; the angle between the tangent and the horizontal line is determined according to the slope of the tangent; the angle is the angle between the maximum principal stress action surface and the fracture surface; The ultimate shear strength thickness of the soil arch is characterized by the angle and the large pile diameter; the axial force is characterized by the sliding force; Then, a second relationship between the sliding force, the angle, the large pile diameter and the large principal stress is determined.

6. The method for determining the spacing between composite piles under soil arching effect according to claim 5, characterized in that: Determining the angle between the tangent line and the horizontal line based on the slope of the tangent line includes: When the target soil arch is in a limit equilibrium state, the angle between the maximum principal stress action surface of the soil arch and the fracture surface is That is, the angle is The angle between the tangent line and the horizontal line is determined by the following formula: Among them, β is the angle.

7. The method for determining the spacing between composite piles under soil arching effect according to claim 6, characterized in that: When the target soil arch is in a limit equilibrium state, the second relationship is as follows: Where, t is the ultimate shear strength thickness of the soil arch; The ultimate shear strength thickness of the soil arch characterized by the angle and the large pile diameter is: Then the second relationship between the sliding force, angle, large pile diameter and large principal stress is determined: Where b1 is the equivalent side length of the large pile diameter.

8. A device for determining the spacing between composite piles under soil arching effect, characterized in that: include: An acquisition module is used to acquire physical parameters of a target soil arch and a composite pile; the physical parameters of the target soil arch include cohesion, internal friction angle and sliding force; the physical parameters of the composite pile include a large pile diameter and a small pile diameter of the composite pile, the large pile is a concrete cast-in-place pile of the composite pile, and the small pile is a micro-grouting steel pipe pile of the composite pile; A determination module is used to determine the trajectory of a soil arch curve according to the large pile diameter and the small pile diameter of the composite pile; when the soil arch is in a limit equilibrium state, determine the first relationship between cohesion and internal friction angle and the major principal stress according to the Mohr-Coulomb theory; obtain the axial force at the arch foot of the large pile through the soil arch curve trajectory and the sliding force; determine the second relationship between the axial force and the major principal stress according to the Mohr-Coulomb theory; determine the target relationship between the physical parameters of the target soil arch and the composite pile and the pile spacing according to the first and second relationship, and then determine the pile spacing according to the target relationship and the physical parameters of the target soil arch and the composite pile.

9. A computer-readable storage medium, characterized in that: The storage medium stores a computer program, and when the computer program is executed by a processor, the steps of the method for determining the spacing between composite piles under the soil arching effect described in any one of claims 1 to 7 are implemented.

10. A computer device, characterized in that: The method comprises a memory, a processor and a computer program stored in the memory and executable on the processor. When the processor executes the program, the method steps for determining the spacing between composite piles under the soil arch effect as described in any one of claims 1 to 7 are implemented.

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