A method, apparatus and storage medium for measuring the stability of unsaturated soil slopes

Abstract

This invention relates to the field of slope stability analysis technology, and in particular to a method, device, and storage medium for measuring the stability of unsaturated soil slopes. The unsaturated soil slope stability measurement method of this invention is based on the soil-water characteristic curve of unsaturated soil and uses the finite element method to solve the Richards equation to obtain the transient seepage field distribution of the unsaturated soil slope. This method is more consistent with reality than the seepage field assumed by empirical formulas in the past. While the SMP criterion proposed by Songgang-Zhongjing considers the influence of intermediate principal stress, the SMP criterion is only suitable for cohesive soil failure criteria. Therefore, this invention modifies the SMP criterion by considering the influence of cohesion, friction angle, and matrix suction, making it applicable to unsaturated cohesive soil slopes. Based on the calculation of the slope's self-weight stress, and using a modified SMP material model, we conduct stability analysis of unsaturated soil slopes using the strength reduction method, considering the influence of the intermediate principal stress of the soil, resulting in more reasonable results.

Description

Technical Field

[0001] This invention relates to the field of slope stability analysis technology, and in particular to a method, device and storage medium for measuring the stability of unsaturated soil slopes. Background Technology

[0002] Unsaturated soil refers to soil whose pores are filled with water and air, meaning its saturation level is less than 100% but greater than 0%. Unsaturated soils are widespread in nature, while truly saturated soils are rare, especially in arid and semi-arid regions. Due to climatic conditions, several soil types with special properties exist, such as expansive soils, disintegrating soils (loess, etc.), and residual soils, collectively referred to as "special soils." They all possess the basic characteristics of unsaturated soils, namely, the presence of suction within the soil structure. This characteristic is particularly pronounced and important in expansive soils.

[0003] Slope sites are a common type of engineering construction site, such as those in mountainous areas, highway embankments, and dams. The stability of slopes directly affects the safety of building structures, road engineering, and dam engineering. When a soil slope becomes unstable under external loads and its own weight, it will form a continuous slip zone, resulting in a landslide. In slope stability analysis, the limit equilibrium method and the strength reduction method are commonly used.

[0004] Currently, slope stability analysis methods mainly consist of the slice analytical method and the numerical method. The analytical method generally uses simplified inter-slice forces and landslide shape assumptions, which cannot describe the deformation coordination conditions between soil masses. The numerical method generally uses an elastoplastic model to simulate the soil, often employing the Mohr-Coulom material model or the Drucker-Prager model, neither of which can reflect the influence of intermediate principal stresses, resulting in a conservative safety factor and inaccurate stability analysis. Summary of the Invention

[0005] Therefore, the technical problem to be solved by the present invention is to overcome the problem of inaccurate stability analysis caused by the failure to consider the influence of intermediate principal stress in the prior art.

[0006] To address the aforementioned technical problems, this invention provides a method for measuring the stability of unsaturated soil slopes, comprising:

[0007] Draw the geometry of the target slope, import it into the finite element simulation software to generate a mesh, and specify the physical parameters of the soil in the area, including cohesion and friction angle.

[0008] Set the analysis start time and step size, and under specified seepage boundary conditions, perform transient analysis of the soil seepage field based on the soil-water characteristic curve and the Richards equation to obtain the pore water pressure distribution. Then, obtain the matrix suction distribution based on the pore water pressure distribution.

[0009] Hydrostatic pressure is applied to the water-facing surface, vertical displacement constraints are set at the bottom boundary and lateral displacement constraints are set at the side boundary, gravity load is applied, the material model is defined as an elastic model, and the matrix suction is input in the form of external force according to the equilibrium differential equations to perform soil self-weight stress analysis.

[0010] Set vertical displacement constraints at the bottom boundary and lateral displacement constraints at the side boundary, define the material model as the Matsuoka-Naka i model, and modify its yield function and plastic potential function according to the modified SMP criterion that considers the effects of cohesion, friction angle and matrix suction to obtain the modified SMP material model. Add the self-weight stress analysis results as prestress and calculate stress, strain and displacement changes.

[0011] By gradually increasing the strength reduction factor by a certain step size, the cohesion and friction angle are reduced, and the stress, strain and displacement changes are recalculated until the calculation fails to converge and the slope becomes unstable and fails. The strength reduction factor in the step before the calculation diverges is the safety factor of the slope.

[0012] Preferably, transient analysis of the soil seepage field using the Richards equation based on the soil-water characteristic curve includes:

[0013] Soil and water characteristic curves or Substituting into the Richards equation, where Θ is the standardized water content, ψ is the matrix suction, a, n, m are fitting parameters, and h is the suction head. b For the intake pressure head, ψ b θ is the intake pressure value. s For saturated water content, θ r λ represents the residual water content, and λ is the fitting parameter.

[0014] The Richards equation is:

[0015]

[0016] Where C is the specific water capacity dθ / dh, and S s θ is the water storage ratio, θ is the volumetric water content, and S is the water storage ratio. e It is the effective saturation, h p It is the pressure head, K is the unsaturated permeability coefficient of the soil, and is the product of the matrix suction head function and the random number of the soil location point.

[0017] Preferably, the seepage boundary condition is a hybrid of the Neumann and Dirichlet conditions:

[0018]

[0019] Where n is the direction of the outward normal to the boundary, u is the flow velocity, ρ is the liquid density, p is the boundary pore water pressure, and K s The permeability coefficient of saturated soil, L is the model parameter, and α and β are the switching functions.

[0020] Preferably, the modified SMP criterion that considers the effects of cohesion, friction angle, and matrix suction is as follows:

[0021]

[0022]

[0023]

[0024]

[0025]

[0026] in, As the first stress invariant, As the second stress invariant, As the third stress invariant, σ x σ y σ y These are the normal stresses, τ and τ, respectively. xy τ yz τ zx They are shear stresses, Given the internal friction angle, cohesion c≠0, and χ can be taken as the effective saturation S. e , where p is the pore water pressure.

[0027] Preferably, the equilibrium differential equations are:

[0028]

[0029] Where, σ x σ y For the normal stress of the soil, τ xy γ is the soil shear stress, γ is the soil weight, p is the pore water pressure, and S is the soil shear stress. e This represents the soil saturation.

[0030] Preferably, the self-weight stress analysis results are used as prestressing, and the calculation of stress, strain, and displacement changes includes:

[0031] The self-weight stress analysis results were used as prestressing additions, and the stress was obtained using the withsol operator.

[0032] Calculate strain based on stress: Where, σ x σ y For the normal stress of the soil, τxy For soil shear stress, ε x ε y For the normal strain of the soil, γ xy D represents the soil shear strain. ep This is the elastoplastic stiffness matrix;

[0033] Calculate displacement based on strain: Where u and v are displacements in the x and y directions, respectively.

[0034] Preferably, the formula for reducing cohesion and friction angle is expressed as follows:

[0035] c F =c / SRF

[0036]

[0037] Among them, c and c F These represent the cohesion before and after the reduction. and These are the friction angles before and after the reduction, respectively, and SRF is the reduction factor.

[0038] The present invention also provides a device for measuring the stability of unsaturated soil slopes, comprising:

[0039] The geometry model building module is used to draw the geometry of the target slope, import it into the finite element simulation software to generate a mesh, and specify the physical parameters of the soil in the region, including cohesion and friction angle.

[0040] The soil seepage analysis module is used to set the analysis start time and step size. Under specified seepage boundary conditions, based on the soil-water characteristic curve, the Richards equation is used to perform transient analysis of the soil seepage field to obtain the pore water pressure distribution. The matrix suction distribution is obtained from the pore water pressure distribution.

[0041] The soil self-weight stress analysis module is used to apply hydrostatic pressure to the water-facing surface, set vertical displacement constraints at the bottom boundary and lateral displacement constraints at the side boundary, apply gravity loads, define the material model as an elastic model, and input the matrix suction in the form of external forces according to the equilibrium differential equations to perform soil self-weight stress analysis.

[0042] The stress, strain, and displacement change calculation module is used to set the vertical displacement constraint of the bottom boundary and the lateral displacement constraint of the side boundary. The material model is defined as the Matsuoka-Naka i model. The yield function and plastic potential function are modified according to the modified SMP criterion that considers the effects of cohesion, friction angle and matrix suction to obtain the modified SMP material model. The self-weight stress analysis results are added as prestress to calculate stress, strain and displacement changes.

[0043] The safety factor calculation module is used to gradually increase the strength reduction factor at certain step sizes to reduce cohesion and friction angle, and recalculate stress, strain and displacement changes until the calculation fails to converge and the slope becomes unstable and fails. The strength reduction factor at the step before the calculation diverges is the safety factor of the slope.

[0044] Preferably, the unsaturated soil slope stability measuring device is used in slope engineering design.

[0045] The present invention also provides a computer-readable storage medium storing a computer program, which, when executed by a processor, implements the steps of the above-described method for measuring the stability of an unsaturated soil slope.

[0046] The technical solution of the present invention has the following advantages compared with the prior art:

[0047] The unsaturated soil slope stability measurement method described in this invention is based on the soil-water characteristic curve of unsaturated soil and uses the finite element method to solve the Richards equation to obtain the transient (steady-state) seepage field distribution of unsaturated soil slopes. This method is more consistent with reality than the seepage field assumed by empirical formulas in the past. The SMP criterion proposed by Songgang-Zhongjing considers the influence of intermediate principal stress. The SMP criterion matches well with the failure test curves of actual soil and rock materials. However, the SMP criterion is only suitable for the failure criterion of cohesive soil with c=0. Therefore, this invention adopts the effective stress criterion of unsaturated soil to modify the SMP criterion, that is, it considers the influence of cohesion, friction angle and matrix suction, making it applicable to unsaturated cohesive soil slopes. Based on the calculation of the self-weight stress of the soil slope, we use the strength reduction method to analyze the stability of unsaturated soil slopes based on the modified SMP material model, considering the influence of the intermediate principal stress of the soil. The results obtained are more reasonable than those based on the Mohr-Coulb criterion. Attached Figure Description

[0048] To make the content of this invention easier to understand, the invention will be further described in detail below with reference to specific embodiments and accompanying drawings, wherein:

[0049] Figure 1 This is a flowchart illustrating the implementation of a method for measuring the stability of unsaturated soil slopes according to the present invention.

[0050] Figure 2 This is a cross-sectional view of the dam slope;

[0051] Figure 3 This is a schematic diagram of the boundary conditions of the seepage field on the dam slope;

[0052] Figure 4 This is a schematic diagram of the calculation area for the dam slope;

[0053] Figure 5 This is a schematic diagram of the finite element mesh generation for the dam slope;

[0054] Figure 6 This is a schematic diagram of the steady-state seepage field on the dam slope;

[0055] Figure 7 This is a schematic diagram of the Mises equivalent stress of the soil on the dam slope;

[0056] Figure 8 This is a schematic diagram of the displacement distribution of a dam slope before instability, based on the modified SMP criterion.

[0057] Figure 9 This is a schematic diagram of the equivalent plastic strain of a dam slope before instability, based on the modified SMP criterion.

[0058] Figure 10 This is a schematic diagram of the displacement distribution of a dam slope before instability based on the MC criterion.

[0059] Figure 11 This is a schematic diagram of the equivalent plastic strain of a dam slope before instability based on the MC criterion.

[0060] Figure 12 This is a structural block diagram of an unsaturated soil slope stability measurement device provided in an embodiment of the present invention. Detailed Implementation

[0061] The core of this invention is to provide a method, apparatus, equipment, and computer storage medium for measuring the stability of unsaturated soil slopes, thereby improving the accuracy of stability analysis.

[0062] To enable those skilled in the art to better understand the present invention, the invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. Obviously, the described embodiments are merely some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0063] Please refer to Figure 1 , Figure 1 The flowchart illustrates the implementation of the unsaturated soil slope stability measurement method provided by this invention; the specific operation steps are as follows:

[0064] S101: Draw the geometry of the target slope, import it into the finite element simulation software to generate a mesh, and specify the physical parameters of the soil in the area, including cohesion and friction angle.

[0065] S102: Set the analysis start time and step size. Under specified seepage boundary conditions, based on the soil-water characteristic curve, use the Richards equation to perform transient analysis of the soil seepage field to obtain the pore water pressure distribution. Based on the pore water pressure distribution, obtain the matrix suction distribution.

[0066] S103: Apply hydrostatic pressure to the water-facing surface, set vertical displacement constraints at the bottom boundary and lateral displacement constraints at the side boundary, apply gravity load, define the material model as an elastic model, input the matrix suction in the form of external force according to the equilibrium differential equations, and perform soil self-weight stress analysis.

[0067] Based on Biot's consolidation theory and the effective stress principle, the equilibrium equations under plane strain conditions can be obtained (according to the convention in elasticity: tension is positive, and compression is negative). The equilibrium differential equations are as follows:

[0068]

[0069] Where, σ x σ y For the normal stress of the soil, τ xy γ is the soil shear stress, γ is the soil weight, p is the pore water pressure, and S is the soil shear stress. e This represents the soil saturation.

[0070] S104: Set vertical displacement constraints at the bottom boundary and lateral displacement constraints at the side boundary. Define the material model as the Matsuoka-Nakai model. Modify its yield function and plastic potential function according to the modified SMP criterion that considers the effects of cohesion, friction angle and matrix suction to obtain the modified SMP material model. Add the self-weight stress analysis results as prestress and calculate stress, strain and displacement changes.

[0071] The SMP criteria are:

[0072]

[0073] I1=σ x +σ y +σ y

[0074]

[0075]

[0076] Wherein, I1 is the first stress invariant, I2 is the second stress invariant, and I3 is the third stress invariant.

[0077] The SMP criterion is suitable for granular materials, i.e., cohesion c = 0, such as sand. For cohesive soils with c ≠ 0, the modified SMP criterion, considering the effects of cohesion, friction angle, and matrix suction, is as follows:

[0078]

[0079]

[0080]

[0081]

[0082]

[0083] in, For the modified first stress invariant, For the modified second stress invariant, For the modified third stress invariant, σ x σ y σ y These are the normal stresses, τ and τ, respectively. xy τ yz τ zx They are shear stresses, Given the internal friction angle, cohesion c≠0, and χ can be taken as the effective saturation S. e , where p is the pore water pressure.

[0084] In Comsol Multiphysics, select the Solid Mechanics module, define the material model as the Matsuoka-Nakai model, and modify its yield function and plastic potential function in Equation according to formulas (1) to (4) to obtain the modified SMP material model, which can reflect the influence of the intermediate principal stress of the soil.

[0085] The self-weight stress analysis results were used as prestressing additions, and the stress was obtained using the withsol operator.

[0086] Calculate strain based on stress: Where, σ x σ y For the normal stress of the soil, τ xy For soil shear stress, ε x ε y For the normal strain of the soil, γ xy D represents the soil shear strain. ep This is the elastoplastic stiffness matrix;

[0087] Calculate displacement based on strain: Where u and v are displacements in the x and y directions, respectively.

[0088] S105: Gradually increase the strength reduction factor by a certain step size to reduce the cohesion and friction angle, and recalculate the stress, strain and displacement changes until the calculation fails to converge and the slope becomes unstable and fails. The strength reduction factor in the step before the calculation diverges is the safety factor of the slope.

[0089] The formula for reducing cohesion and friction angle is expressed as follows:

[0090] c F =c / SRF

[0091]

[0092] Among them, c and c F These represent the cohesion before and after the reduction. and These are the friction angles before and after the reduction, respectively, and SRF is the reduction factor.

[0093] The strength reduction factor SRF scan range was set to (1, 0.005, 2.25). The SRF was performed with an initial value of 1, a step size of 0.005, and a termination value of 2.25 to measure the material physical parameters c and The reduction will result in the strength index c after each reduction. F and Substitute the material parameters into the finite element model and perform nonlinear finite element analysis; if the calculation results converge, reduce the material physical parameters c and y by a reduction factor increasing by 0.005 in increments. Continue with the nonlinear finite element analysis. If the calculation results do not converge, it indicates that the soil material can no longer withstand the equivalent load of its own weight stress field, and the slope is in a state of sliding failure. The strength reduction factor at this point is the safety factor of the slope. Examine the horizontal displacement-reduction factor curve at the top of the slope; the reduction factor corresponding to the point of maximum curvature on the displacement curve is the safety factor. Examine the equivalent plastic strain of the slope to obtain the slope slip arc. This can provide services for slope engineering design.

[0094] The unsaturated soil slope stability measurement method described in this invention is based on the soil-water characteristic curve of unsaturated soil and uses the finite element method to solve the Richards equation to obtain the transient (steady-state) seepage field distribution of unsaturated soil slopes. This method is more consistent with reality than the seepage field assumed by empirical formulas in the past. The SMP criterion proposed by Songgang-Zhongjing considers the influence of intermediate principal stress. The SMP criterion matches well with the failure test curves of actual soil and rock materials. However, the SMP criterion is only suitable for the failure criterion of cohesive soil with c=0. Therefore, this invention adopts the effective stress criterion of unsaturated soil to modify the SMP criterion, that is, it considers the influence of cohesion, friction angle and matrix suction, making it applicable to unsaturated cohesive soil slopes. Based on the calculation of the self-weight stress of the soil slope, we use the strength reduction method to analyze the stability of unsaturated soil slopes based on the modified SMP material model, considering the influence of the intermediate principal stress of the soil. The results obtained are more reasonable than those based on the Mohr-Coulomb criterion.

[0095] Based on the above embodiments, step S102 will be further described in detail:

[0096] Based on the soil-water characteristic curve (the relationship between soil moisture content and matrix suction can be described by the soil seepage gradually transitioning from an unsaturated to a saturated state), transient analysis of the soil seepage field using the Richards equation includes:

[0097] Soil-water characteristic curves: Van Genuchten model Or Brooks-Corey model Substituting into the Richards equation, where Θ is the standardized water content, ψ is the matrix suction, a, n, m are fitting parameters, and h is the suction head. b For the intake pressure head, ψ b θ is the intake pressure value. s For saturated water content, θ r λ represents the residual water content, and λ is the fitting parameter.

[0098] The Richards equation is:

[0099]

[0100] Where C is the specific water capacity dθ / dh, and S s θ is the water storage ratio, θ is the volumetric water content, and S is the water storage ratio. e It is the effective saturation, h p It is the pressure head, and K is the unsaturated permeability coefficient of the soil, which is the product of the matrix suction head function and the random number of soil location points. Compared with the existing technology, which regards it as a single function of saturation, it takes into account the influence of random pore distribution, which is more in line with reality.

[0101] For seepage boundaries, when the soil is unsaturated, it will not expel water; when the soil is saturated, it will expel water. To simulate seepage boundaries in slope soil, a hybrid of Neumann conditions (given flow rate or velocity at boundary conditions) and Dirichlet conditions (given head or pressure values ​​at boundary conditions) was used:

[0102]

[0103] Where n is the direction of the outward normal to the boundary, u is the flow velocity, ρ is the liquid density, p is the boundary pore water pressure, and K s The saturated soil permeability coefficient, L is a model parameter. When the seepage boundary soil is in an unsaturated state, the external flow velocity I = 0. α and β are switching functions used to switch between the Dirichlet flow boundary condition and the Neumann head boundary condition.

[0104] Based on the above embodiments, this embodiment uses the method of the present invention to conduct a fluid-structure interaction stability analysis on a dam slope. The soil material adopts the SMP strength criterion considering the influence of intermediate principal stress.

[0105] like Figure 2 The cross-section of the dam is shown. Lengths L1, L2, and L3 are 24m, 5m, and 24m respectively, and the dam height L4 is 2m. The upstream water level is 10m, and the potential seepage height downstream is 4m. The total width of the dam is 53m. The seepage field boundary conditions are as follows... Figure 3 As shown, the Dirichlet boundary conditions are: segments EF and CD have known hydrostatic pressure and head; the Neumann condition is: segments AB, DE, and AF are stagnant boundaries. The soil cohesion is c = 25 kPa, and the friction angle is... Soil weight ρ = 20 kN / m 3 The finite element calculation domain is as follows: Figure 4 As shown, the finite element computational mesh is as follows: Figure 5 As shown.

[0106] Solving the Richards equations yields the steady-state seepage field on the dam slope, as follows: Figure 6 As shown, from Figure 6 It can be seen that the phreatic line distribution on the dam slope shows that the soil is saturated in the area below the phreatic line and unsaturated in the area above the phreatic line.

[0107] Hydrostatic pressure is applied to the water-facing side, and displacement constraints are applied; vertical displacement constraints are applied to the bottom boundary, and lateral displacement constraints are applied to the lateral boundaries, with gravity loads applied. The solid mechanics module is selected, the material model is defined as an elastic model, and the matrix suction is input as an external force according to the equilibrium differential equations. The self-weight stress analysis results of the dam slope soil are as follows: Figure 7As shown, due to the asymmetric distribution of pore water pressure, the Mises equivalent stress of the soil exhibits an asymmetric distribution.

[0108] The stability analysis of the dam slope was conducted using the Mohr-Coulomb strength criterion and the modified SMP strength criterion, respectively. The results are as follows: Figure 8 , Figure 9 , Figure 10 , Figure 11 As shown, the plastic strain distributions of slopes based on the Mohr-Coulomb strength criterion and the modified SMP strength criterion are similar, while the displacement field distributions differ somewhat, and the overall slip arc patterns are basically the same. The slope safety factor based on the Mohr-Coulomb strength criterion is 1.915; the slope safety factor based on the modified SMP strength criterion is 2.19, which is 14% higher than that of the Mohr-Coulomb strength criterion. This is because the Mohr-Coulomb criterion does not consider the influence of the intermediate principal stress of the soil, and the results obtained are more conservative. The slope stability method based on the modified SMP strength criterion adopted in this invention can fully consider the influence of the intermediate principal stress of the soil, and has stronger guiding value for the stability design of unsaturated soil slopes.

[0109] Please refer to Figure 12 , Figure 12 A structural block diagram of an unsaturated soil slope stability measuring device provided in an embodiment of the present invention; the specific device may include:

[0110] The geometric model building module 100 is used to draw the geometry of the target slope, import it into the finite element simulation software to generate a mesh, and specify the physical parameters of the soil in the region, including cohesion and friction angle.

[0111] The soil seepage analysis module 200 is used to set the analysis start time and step size, and to perform transient analysis of the soil seepage field using the Richards equation under specified seepage boundary conditions to obtain the pore water pressure distribution. The matrix suction distribution is obtained based on the pore water pressure distribution.

[0112] The Soil Self-Weight Stress Analysis Module 300 is used to apply hydrostatic pressure to the water-facing surface, set vertical displacement constraints at the bottom boundary and lateral displacement constraints at the side boundary, apply gravity loads, define the material model as an elastic model, and input the matrix suction in the form of external forces according to the equilibrium differential equations to perform soil self-weight stress analysis.

[0113] The stress, strain, and displacement change calculation module 400 is used to set the vertical displacement constraint of the bottom boundary and the lateral displacement constraint of the side boundary. The material model is defined as the Matsuoka-Naka i model. The yield function and plastic potential function are modified according to the modified SMP criterion that considers the effects of cohesion, friction angle and matrix suction to obtain the modified SMP material model. The self-weight stress analysis results are added as prestress to calculate stress, strain and displacement changes.

[0114] The safety factor calculation module 500 is used to gradually increase the strength reduction factor at a certain step size to reduce the cohesion and friction angle, and recalculate the stress, strain and displacement changes until the calculation fails to converge and the slope becomes unstable and fails. The strength reduction factor in the step before the calculation diverges is the safety factor of the slope.

[0115] The unsaturated soil slope stability measurement device of this embodiment is used to implement the aforementioned unsaturated soil slope stability measurement method. Therefore, the specific implementation of the unsaturated soil slope stability measurement device can be found in the previous embodiment section of the unsaturated soil slope stability measurement method. For example, the geometric model construction module 100, the soil seepage analysis module 200, the soil self-weight stress analysis module 300, the stress, strain and displacement change calculation module 400, and the safety factor calculation module 500 are respectively used to implement steps S101, S102, S103, S104 and S105 in the above-mentioned unsaturated soil slope stability measurement method. Therefore, its specific implementation can be referred to the description of the corresponding embodiments, which will not be repeated here.

[0116] A specific embodiment of the present invention also provides a computer-readable storage medium storing a computer program, which, when executed by a processor, implements the steps of the above-described method for measuring the stability of an unsaturated soil slope.

[0117] Those skilled in the art will understand that embodiments of this application can be provided as methods, systems, or computer program products. Therefore, this application can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, this application can take the form of a computer program product embodied 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.

[0118] This application is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of this application. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, generate instructions for implementing the flowchart... Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0119] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1 One or more processes and / or boxes Figure 1 The function specified in one or more boxes.

[0120] These computer program instructions may also be loaded onto a computer or other programmable data processing equipment to cause a series of operational steps to be performed on the computer or other programmable equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable equipment for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.

[0121] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A method of measuring the stability of a non-saturated soil slope, characterized by, The method comprises the following steps: drawing the geometric shape of the target slope, importing it into a finite element simulation software to divide a grid, and specifying the physical parameters of the regional soil body, including cohesion and friction angle; setting an analysis starting time and a step length, performing transient analysis on the soil seepage field based on the soil water characteristic curve and using the Richards equation under the specified seepage boundary condition to obtain a pore water pressure distribution, and obtaining a matric suction distribution according to the pore water pressure distribution; applying a hydrostatic pressure on the water-facing surface, setting vertical displacement constraints on the bottom boundary and lateral displacement constraints on the lateral boundary, applying a gravity load, defining a material model as an elastic model, inputting the matric suction as an external force form according to a balance differential equation set, and performing self-weight stress analysis on the soil body; setting vertical displacement constraints on the bottom boundary and lateral displacement constraints on the lateral boundary, defining a material model as a Matsuoka-Nakai model, modifying the yield function and plastic potential function of the Matsuoka-Nakai model according to a modified SMP criterion considering the influence of cohesion, friction angle and matric suction to obtain a modified SMP material model, adding the self-weight stress analysis result as a prestress, and calculating stress, strain and displacement changes; gradually increasing a strength reduction coefficient by a certain step length, reducing the cohesion and friction angle, recalculating the stress, strain and displacement changes, and until the calculation does not converge, the slope is unstable and damaged, and then the strength reduction coefficient of the step before the calculation divergence is the safety factor of the slope.

2. The method of claim 1, wherein, The transient analysis on the soil seepage field based on the soil water characteristic curve and using the Richards equation comprises the following steps: The soil water characteristic curve or is fitted to Richards' equation, where Θ is the normalized water content, ψ is the matric suction, a, n, m are fitting parameters, h is the suction head, h b is the air entry pressure head, ψ b is the air entry pressure value, θ s is the saturated water content, θ r is the residual water content, and λ is a fitting parameter; The Richards equation is as follows: where C is the specific water capacity dθ / dh, S s is the water storage rate, θ is the volumetric water content, S e is the effective saturation, h p is the pressure head, K is the unsaturated hydraulic conductivity of the soil, and ψ is the product of the matric suction head function and a random number of the soil location point.

3. The method of claim 1, wherein, The seepage boundary condition is a mixed form of Neumann condition and Dirichlet condition: where n is the outward normal direction, u is the flow velocity, p is the liquid density, p is the pore water pressure at the boundary, K s The saturated soil permeability coefficient, L is a model parameter, and a, b are switch functions.

4. The method of claim 1, wherein, The modified SMP criterion considering the influence of cohesion, friction angle and matric suction is as follows: wherein is a first stress invariant, is a second stress invariant, is a third stress invariant, σ x , σ y , σ y are normal stresses, τ xy , τ yz , τ zx are shear stresses, is an internal friction angle, cohesion c≠0, χ can be taken as an effective saturation S e p is a pore water pressure.

5. The method of claim 1, wherein, The balance differential equation set is as follows: wherein σ x , σ y is the normal stress of the soil, τ xy is the shear stress of the soil, γ is the specific weight of the soil, p is the pore water pressure, S e is the saturation of the soil.

6. The method of claim 1, wherein, The calculation of stress, strain and displacement changes by adding the self-weight stress analysis result as a prestress comprises the following steps: adding the self-weight stress analysis result as a prestress, and obtaining stress by using a withsol operator; Calculate strain based on stress: Where, σ x σ y For the normal stress of the soil, τ xy For soil shear stress, ε x ε y For the normal strain of the soil, γ xy D represents the soil shear strain. ep This is the elastoplastic stiffness matrix; Displacement is calculated from strain: where u, v are displacements in x, y directions.

7. The method of claim 1, wherein, The formula for reducing the cohesion and friction angle is as follows: c F = c / SRF wherein c and c F respectively are the cohesion before and after reduction, and respectively are the friction angle before and after reduction, SRF is the reduction factor.

8. A non-saturated soil slope stability measuring device, characterized by, The method comprises the following steps: a geometric model construction module, used for drawing the geometric shape of the target slope, importing it into a finite element simulation software to divide a grid, and specifying the physical parameters of the regional soil body, including cohesion and friction angle; a soil seepage analysis module, used for setting an analysis starting time and a step length, performing transient analysis on the soil seepage field based on the soil water characteristic curve and using the Richards equation under the specified seepage boundary condition to obtain a pore water pressure distribution, and obtaining a matric suction distribution according to the pore water pressure distribution; a soil self-weight stress analysis module, used for applying a hydrostatic pressure on the water-facing surface, setting vertical displacement constraints on the bottom boundary and lateral displacement constraints on the lateral boundary, applying a gravity load, defining a material model as an elastic model, inputting the matric suction as an external force form according to a balance differential equation set, and performing self-weight stress analysis on the soil body; and a strength reduction analysis module, used for setting vertical displacement constraints on the bottom boundary and lateral displacement constraints on the lateral boundary, defining a material model as a Matsuoka-Nakai model, modifying the yield function and plastic potential function of the Matsuoka-Nakai model according to a modified SMP criterion considering the influence of cohesion, friction angle and matric suction to obtain a modified SMP material model, adding the self-weight stress analysis result as a prestress, and calculating stress, strain and displacement changes. A stress, strain and displacement change calculation module is configured to set a bottom boundary vertical displacement constraint, a lateral boundary lateral displacement constraint, define a material model as a Matsuoka-Nakai model, modify a yield function and a plastic potential function of the material model according to a modified SMP criterion considering influences of cohesion, a friction angle and matrix suction, obtain a modified SMP material model, add a self-weight stress analysis result as a prestress, and calculate stress, strain and displacement changes; A safety factor calculation module is configured to gradually increase a strength reduction factor by a certain step, reduce the cohesion and the friction angle, recalculate the stress, strain and displacement changes, and until the calculation does not converge, the slope is unstable and damaged, and a strength reduction factor of a step before the calculation divergence is the safety factor of the slope.

9. The apparatus for measuring the stability of a non-saturated soil slope according to claim 8, wherein, The application is applied to slope engineering design.

10. A computer-readable storage medium, characterized in that, The computer readable storage medium stores a computer program, and the computer program is executed by the processor to realize the steps of the unsaturated soil slope stability measurement method in any one of claims 1 to 7.

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