Slope stability analysis method based on rock and soil characteristics

Abstract

The invention discloses a slope stability analysis method based on rock and soil characteristics, belongs to the technical field of traffic engineering modeling, and aims to solve the technical problems as follows: exploring a slope instability mechanism; analyzing the reliability of the slope sliding surface system; the influence of the hydraulic effect on the slope stability is avoided. The method specifically comprises the steps that the geological structure, the rock-soil body type and the distribution characteristics of the side slope are surveyed in detail; performing indoor and outdoor tests to obtain mechanical parameters of the rock-soil body; the influence of underground water level change, rainfall infiltration and underground water flow on the slope stability is investigated, then main factor parameters influencing the slope stability are determined, a slope two-dimensional finite element model is established on the basis, investigation parameters are input, and subsequent feedback and improvement are carried out. Therefore, the performance of the slope stability under the influence of complex geological conditions and external factors is explored.

Description

Technical Field

[0001] The invention relates to the field of transportation engineering, and in particular to a slope stability analysis method based on rock and soil characteristics. Background Art

[0002] The technical background of slope stability analysis methods based on geotechnical characteristics is a multidisciplinary and comprehensive research field, which mainly relies on the in-depth understanding of the physical and mechanical characteristics of rock and soil, combined with advanced numerical simulation technology and probabilistic statistical analysis methods. The core of this technical background is to fully consider the three-dimensional characteristics and dynamic response of rock slopes through means such as the modified pseudo-dynamic method, as well as the application of numerical tools in simulating complex geological conditions, so as to achieve accurate analysis of the stability of slopes under static and dynamic forces. At the same time, the application of system reliability analysis enables the evaluation process to cover multiple potential sliding surfaces and nonlinear characteristics of rock mass strength parameters, enhancing the rationality of the evaluation results. Considering the influence of the timeliness (rheology) of rock mass strength parameters on the long-term stability of slopes, and the role of the randomness of geotechnical parameters on stability reliability, these methods are constantly being improved and optimized, in order to provide more reliable data support in engineering design, ensure engineering safety, and reduce the risk of disasters caused by slope instability. Summary of the invention

[0003] The present invention provides a slope stability analysis method based on rock and soil characteristics to solve the above problems;

[0004] The present invention provides a slope stability analysis method based on rock and soil characteristics, comprising the following steps:

[0005] S1. Conduct detailed investigation on the geological structure, rock and soil type and distribution characteristics of the slope, and analyze the physical properties of the rock and soil, such as density, water content, porosity, etc.;

[0006] S2. Conduct indoor and outdoor tests to obtain mechanical parameters of rock and soil, such as shear strength (c, φ value), elastic modulus, Poisson's ratio, etc.;

[0007] S3. Investigate the influence of groundwater level change, rainfall infiltration and groundwater flow on slope stability, and analyze the change of rock and soil strength under different hydrogeological conditions;

[0008] S4. Model establishment: Based on the geological survey and parameter test results, a suitable slope stability analysis model is established, including limit equilibrium method, finite element method, discrete element method, etc., considering the simulation of boundary conditions, initial stress state, and constitutive relationship by different models;

[0009] S5. Use the established model to calculate stability, derive the safety factor or directly conduct stability evaluation, and analyze the slope stability under different working conditions, such as natural state, heavy rain, snowfall, etc.;

[0010] S6. Conduct model analysis on slope displacement, seepage, groundwater, etc., collect data, and perform model modification and feedback analysis based on simulation results.

[0011] According to the present invention, a slope stability analysis method based on rock and soil characteristics is provided, wherein step S1 specifically comprises the following steps:

[0012] S11. Collect regional basic geographic information data, including basic regional area data and slope transverse and longitudinal lengths;

[0013] S12. Collect slope topography data, including regional environmental geomorphic characteristics, terrain shape characteristics, ground crack distribution, and hydrological distribution characteristics;

[0014] S13. Collect ground elevation data, including the total height from the slope foot to the slope top and the inclination angle of each part;

[0015] S14. Collect the data set of stratum geotechnical characteristics, including the depth distribution characteristics of underground rock layers, rock layer strength parameters, and rock layer hydraulic parameters of the slope, and take samples at different parts of the slope, including original soil samples and rock samples;

[0016] S14. Collect historical weather data sets, including regional average monthly precipitation, average temperature distribution, and average snowfall over the past decade.

[0017] According to the present invention, a slope stability analysis method based on rock and soil characteristics is provided, wherein the step S2 is to conduct indoor and outdoor tests to obtain mechanical parameters of the rock and soil mass, such as shear strength (c, φ value), elastic modulus, Poisson's ratio, etc.;

[0018] S21, integration step 1: classify and remove redundancy of the data collected from the slope geotechnical investigation, and retain data with strong reference value;

[0019] S22, such as Figure 2 As shown, the slope strata and soil are divided into regions, and the rock layers are classified according to the detection depth;

[0020] S23. Conduct indoor experiments based on original soil and rock samples, including direct shear test and triaxial shear test, to determine the cohesion (c value) and internal friction angle (φ value) of rock and soil;

[0021] S24. Perform an acoustic wave test according to the divided formation area, obtain the returned acoustic wave, and calculate the corresponding elastic modulus and Poisson's ratio according to the elastic wave theory.

[0022] According to the present invention, a slope stability analysis method based on rock and soil characteristics is provided, which determines the corresponding elastic modulus and Poisson's ratio calculated based on elastic wave theory, and the step S32 specifically includes the following steps:

[0023] S241. Use drilled core specimens to test the shear wave velocity. Use the single-hole shear wave velocity method (layer detection method) to test the shear wave velocity. Read the measured waveforms in the positive and negative directions, find the intersection of the waveforms, read the propagation time of the first arrival wave, and calculate the shear wave velocity value of each measuring point (layer) according to the formula, thereby calculating the equivalent shear wave velocity value of the soil layer.

[0024]

[0025] v se =d 0 / t;

[0026]

[0027] Among them, v i is the shear wave velocity of the soil layer from the i-1th point to the ith point; H i The depth of the i-th point; H i-1 The depth of the i-1th point; d i Calculate the thickness of the i-th soil layer within the depth range; s is the distance from the center of the excitation plate to the center of the hole; t i Arrival time of shear wave at point i; t i-1 Arrival time of shear wave at point i-1; v se Equivalent shear wave velocity of soil layer; d 0 Calculation depth; t is the propagation time of shear wave from the ground to the calculation depth; v is the propagation time of shear wave from the ground to the calculation depth si Calculate the shear wave velocity of the i-th soil layer within the depth range; n calculates the number of layers of soil within the depth range;

[0028] S242. On site, the longitudinal wave velocity of the rock mass is measured by the acoustic wave method. A transmitting and receiving downhole transducer is used. The spacing between transmitting and receiving is 30 cm, and the spacing between receiving and receiving is 20 cm. Acoustic wave information is transmitted and received along the well wall in the borehole (a bare hole containing well fluid). The initial arrival time of the longitudinal wave is determined according to the waveform starting point in the waveform collected by the instrument, and the longitudinal wave velocity is calculated.

[0029]

[0030]

[0031]

[0032]

[0033]

[0034] Where E d ,μ,G d , Q d and ρ are the dynamic elastic modulus, Poisson's ratio, dynamic shear modulus, dynamic bulk modulus and density of the rock mass, respectively; V p , V s are the propagation velocities of longitudinal and transverse waves in the rock mass, respectively. From the formula, we can see that after measuring ρ, we only need to measure V p , V s , the dynamic modulus and Poisson's ratio of the rock mass can be calculated.

[0035] According to the present invention, a slope stability analysis method based on rock and soil characteristics is provided. Step S3 examines the influence of groundwater level change, rainfall infiltration, and groundwater flow on slope stability, and the change of rock and soil strength under different hydrogeological conditions, and specifically includes the following steps:

[0036] S31. Determine the underground water characteristics of the slope and the depth of the groundwater level in the dry state;

[0037] S32. Classify the collected historical weather data sets to determine the month with the maximum rainfall and snowfall in a year. Collect historical weather data for at least the past ten years, including rainfall, snowfall, temperature, humidity, etc. Preprocess the collected data, including data cleaning, missing value processing, outlier detection, etc. to ensure data quality. Classify the preprocessed data by month, and count the rainfall and snowfall in each month separately. Use statistical methods, such as box plots and histograms, to analyze the distribution characteristics of rainfall and snowfall in each month, determine the month with the maximum rainfall and snowfall in a year, and analyze its relationship with climate change, geographical location and other factors.

[0038] S33. Determine the permeability coefficient of different rock types by consulting the regional moisture manual and conducting indoor experiments. Extract groundwater from the aquifer in a selected borehole or shaft outdoors to form an artificial drawdown field. Determine the water richness and hydrogeological parameters of the aquifer through the relationship between water gushing out and water level drop.

[0039] According to the present invention, a slope stability analysis method based on rock and soil characteristics is provided. When determining the snowfall distribution characteristics, the step S32 specifically includes the following steps:

[0040] S321, the degree-day factor method is used to estimate the energy balance of the snowmelt process, combining temperature and time, to quantify the total energy required for snowmelt for every 1 degree increase in temperature within a certain temperature range;

[0041] Degree-day model calculation formula:

[0042]

[0043] Among them, M s is the snowmelt thickness; DDF s is the degree-day factor, which is taken as 3 mm / (℃·d) by consulting the Xinjiang Geology and Hydrology Manual and related literature; T M is the daily average temperature, which is replaced by the monthly average temperature; T B It is the reference temperature, which is normally 0℃.

[0044] According to the present invention, a slope stability analysis method based on rock and soil characteristics is provided. The step S4 is to establish a suitable slope stability analysis model, such as limit equilibrium method, finite element method, discrete element method, etc., considering the simulation of boundary conditions, initial stress state, and constitutive relationship by different models, and specifically includes the following steps:

[0045] S41. Establish a two-dimensional finite element model to analyze the stability and seepage characteristics of the slope under different rainfall conditions. Use Geo-Studio software to conduct detailed stability analysis and seepage field simulation on typical cross sections of the slope.

[0046] S42. Divide the lithology of the slope into different levels to truly reflect the geological structure of the slope, select a suitable inclination angle of the sliding body, and the selection of this angle is consistent with the inclination angle of the actual slope. The left and lower boundaries of the model are set as impermeable boundaries, the upper boundary is a permeable boundary so that rainwater can penetrate freely, and the right boundary is a zero pressure head boundary so that rainwater can be discharged from the soil;

[0047] S43. In order to better simulate the distribution and flow of water during rainfall, the model is divided into three areas: precipitation infiltration area, landslide prone area and precipitation seepage area. When analyzing the seepage state, multiple observation points are selected on the surface of the three different areas of the slope to monitor the changes in soil pore water pressure;

[0048] S44. Seep / w module and Slope / w module in Geo-studio numerical simulation software were used to conduct seepage and stability analysis to reveal the variation of slope seepage trend and safety factor;

[0049] According to the present invention, a slope stability analysis method based on geotechnical characteristics is provided, which determines to perform seepage and stability analysis based on the Seep / w module and Slope / w module in Geo-studio numerical simulation software, and the step S44 specifically includes the following steps:

[0050] S441. Perform saturated-unsaturated seepage analysis on the slope in the Seep / w module. The saturated-unsaturated seepage equation is:

[0051]

[0052] i, j = 1, 2, 3.

[0053] in, is the saturated permeability tensor; K r (h c ) is the negative pressure head h c The function between the unsaturated hydraulic conductivity K, its value is 1 in the saturated zone and between 0 and 1 in the unsaturated zone; ω is the sink index; C is the water capacity;

[0054] S442. When considering the volumetric water content of soil, the Fredlund-Xing model is used. It is a mathematical model for describing the soil-water characteristic curve (SWCC) of unsaturated soil. In the Fredlund-Xing model, the shape of the soil-water characteristic curve depends on the pore size distribution of the soil. A nonlinear least squares computer program is used to determine the best fitting parameters for the experimental data. The equation of the model is based on the assumption that the shape of the soil-water characteristic curve is affected by the pore size distribution of the soil. The Fredlund-Xing model expression is:

[0055]

[0056] Where, θ is the volumetric water content; θ s is the residual moisture content; S is the saturated matrix suction; S r is the matrix suction corresponding to the residual moisture content; e is the soil porosity ratio; a is the influencing parameter of soil pore size distribution; m and n are shape parameters.

[0057] Based on Fredlund soil strength theory, the theoretical formula for shear strength of unsaturated soil is as follows:

[0058]

[0059] Where: τ f is the shear stress; c′ is the effective cohesion; σ n is the normal total stress; u w is the pore water pressure; Effective internal friction angle; is the internal friction angle that changes with matrix suction; u a is the pore gas pressure;

[0060] S443. In the Slope / w module, the limit equilibrium method is used to analyze the stability of the slope. The transfer coefficient method should be used to calculate the landslide thrust. The strip force system is shown in the figure. When T i When <0, that is, when there is a sliding force opposite to the sliding direction, T should be taken i = 0. When the residual sliding force of the last block of the landslide body is less than or equal to 0, the landslide is stable; when it is greater than 0, the landslide is unstable;

[0061] like Figure 3 As shown in the figure, the landslide soil unit contribution formula is:

[0062]

[0063]

[0064]

[0065]

[0066]

[0067] Among them, F s is the safety factor, T i is the sliding force of the i-th slider, W i is the self-weight of the ith slider, W bi is the external load on the slider surface, α i is the inclination angle of the i-th slider, ψ i is the transfer coefficient, is the internal friction angle of the ith slider, C i is the cohesion of soil, L i is the slider length, R i is the resistance of the slider on the sliding surface.

[0068] According to the present invention, a slope stability analysis method based on rock and soil characteristics is provided. The step S5 uses the established model to perform stability calculation, obtains the safety factor or directly performs stability evaluation, and analyzes the slope stability under different working conditions, such as natural state, heavy rain, snowfall, etc., and specifically includes the following steps:

[0069] S51. Based on the permeability coefficient and porosity of each layer of soil, input the parameter values ​​in the Seep / w module, define the soil layer boundary, input the permeability coefficient and porosity parameter values ​​of each soil layer in turn, and clarify the boundary conditions of each soil layer in the model, including the contact surface characteristics between layers, and the interaction between the soil layer and the surrounding medium (such as bedrock, water body, etc.);

[0070] S52. The rainfall and snowfall are converted into rainfall intensity at the upper boundary of the model. The left, right and lower boundaries are defined as impermeable boundaries. At the upper boundary of the model, the rainfall and snowfall are converted into equivalent rainfall intensity according to meteorological data. The water volume after melting snow is considered. The rainfall intensity is set to change periodically to simulate the actual rainfall process. The left and right boundaries of the model are defined as impermeable boundaries to simulate the geological conditions on both sides of the actual slope. The lower boundary of the model is also defined as an impermeable boundary to simulate the bottom restriction condition of the groundwater level.

[0071] S53. Define precipitation as a periodic change, define a periodic rain-stop period, run two cycles and observe the changes in the seepage length and safety factor of the slope. Define precipitation as a periodic change, simulate the seasonal characteristics of actual rainfall, set a periodic rain-stop period to simulate the seepage recovery process during the rainfall interval, run the model for two complete rainfall-rain-stop cycles to observe the dynamic changes of the slope seepage field. During the simulation process, monitor the seepage length and safety factor of the slope in real time, analyze their changing trends in different rainfall stages, and evaluate the stability of the slope under different rainfall conditions through comparative analysis, providing a scientific basis for slope protection design.

[0072] According to the present invention, a slope stability analysis method based on rock and soil characteristics is provided. In step S6, displacement, seepage, groundwater and other model analyses are performed on the slope, data are collected, and the model is corrected and feedback analyzed according to the simulation results:

[0073] S61. Establish a seepage model corresponding to the displacement analysis in the Seep / w analysis module, input parameters such as the permeability coefficient and porosity ratio of each layer of soil, define boundary conditions such as rainfall infiltration, simulate the slope seepage field under different rainfall intensities, and collect data such as seepage path, flow velocity, pore water pressure, etc.;

[0074] S62. Combined with the results of seepage analysis, simulate the groundwater flow field, consider the impact of groundwater level changes on slope stability, analyze the impact of groundwater flow on soil effective stress distribution and possible soil softening, and collect key data such as groundwater level, hydraulic gradient, and permeability coefficient;

[0075] S63. Modify the model and conduct feedback analysis based on the simulation results. After collecting preliminary simulation results, optimize the model and improve the accuracy of the analysis.

[0076] According to the present invention, a slope stability analysis method based on rock and soil characteristics is provided to optimize the model and improve the accuracy of the analysis. The step S63 specifically includes the following steps:

[0077] S631. Compare the simulation results with the field monitoring data, identify the deviations in the model, and adjust the model parameters, such as permeability coefficient, soil mechanical parameters, etc., based on the deviation analysis to better reflect the actual situation. If necessary, redefine the model boundary conditions to ensure the accuracy of the simulation;

[0078] S632. Re-enter the corrected parameters into the model and conduct a new round of simulation analysis. Repeat the displacement, seepage, and groundwater analysis steps until the simulation results are highly consistent with the field data. Through feedback analysis, verify the effectiveness of the model correction to ensure that the model can accurately predict the stability of the slope. BRIEF DESCRIPTION OF THE DRAWINGS

[0079] Figure 1 It is a schematic flow chart of a slope stability analysis method based on rock and soil characteristics provided by the present invention;

[0080] Figure 2 It is a soil layering schematic diagram of the slope stability analysis method based on rock and soil characteristics provided by the present invention;

[0081] Figure 3 It is a schematic diagram of the sliding force of a landslide in the slope stability analysis method based on rock and soil characteristics provided by the present invention. DETAILED DESCRIPTION

[0082] Figure 1 is a schematic diagram of the slope stability analysis method based on rock and soil characteristics provided by the present invention, referring to Figure 1 , in combination with the embodiments, a slope stability analysis method based on rock and soil characteristics provided by the present invention is described in detail, including:

[0083] 1. Conduct detailed investigation on the geological structure, rock and soil type and distribution characteristics of the slope, and analyze the physical properties of the rock and soil, such as density, water content, porosity, etc.;

[0084] 2. Conduct indoor and outdoor tests to obtain mechanical parameters of rock and soil, such as shear strength (c, φ value), elastic modulus, Poisson's ratio, etc.;

[0085] 3. Investigate the impact of groundwater level changes, rainfall infiltration, and groundwater flow on slope stability, and analyze the changes in rock and soil strength under different hydrogeological conditions;

[0086] 4. Establishment of stability analysis model: According to the geological survey and parameter test results, establish a suitable slope stability analysis model, limit equilibrium method, finite element method, discrete element method, etc., considering the simulation of boundary conditions, initial stress state and constitutive relationship by different models;

[0087] 5. Use the established model to calculate stability, obtain the safety factor or directly conduct stability evaluation, and analyze the slope stability under different working conditions, such as natural state, heavy rain, snowfall, etc.;

[0088] 6. Conduct model analysis on slope displacement, seepage, groundwater, etc., collect data, and modify and conduct feedback analysis on the model based on the simulation results.

[0089] Apply the above solution in practice, the specific process is as follows:

[0090] Step 1: Collect data.

[0091] 1.1. Collect regional basic geographic information data, including basic regional area data and slope transverse and longitudinal lengths;

[0092] 1.2. Collect slope topography and geomorphology data, including regional environmental geomorphology characteristics, terrain shape characteristics, ground crack distribution, and hydrological distribution characteristics;

[0093] 1.3. Collect ground elevation data, including the total height from the slope foot to the slope top and the inclination angles of each part;

[0094] 1.4. Collect the data set of geological and geotechnical characteristics, including the depth distribution characteristics of the underground rock layer of the slope, the rock layer strength parameters, and the rock layer hydraulic parameters. Sampling is carried out at different parts of the slope, including original soil samples and rock samples;

[0095] 1.5. Collect historical weather data sets, including the regional average monthly precipitation, average temperature distribution, and average snowfall in the past ten years, as shown in Tables 1 and 2.

[0096] Table 1 Rainfall data table

[0097]

[0098]

[0099] Table 2 Temperature change diagram

[0100] Temperature changes Average temperature (℃) Extreme maximum temperature (℃) Extreme minimum temperature (℃) January -26.4 -2.6 -49.6 February -27.1 1.1 -43.6 March -10.2 14.2 -35.5 April 1.3 22.2 -24.2 May 5.9 24.4 -14.6 June 9.6 24.8 -10.5 July 11.3 29.8 -6.7 August 10.4 26.7 -11.5 September 6.2 24.2 -13.1 October -1.1 19.8 -25.5 November -11 13 -35.7 December -21.7 0.6 -42.3

[0101] Step 2: Combined with the rock and soil layer characteristics and topographic data collected in step 1, indoor and outdoor tests are carried out to obtain the mechanical parameters of the rock and soil, such as shear strength (c, φ value), elastic modulus, Poisson's ratio, etc.:

[0102] 2.1. Integration Step 1: Classify and remove redundant data collected from slope geotechnical investigation, and retain data with strong reference value, such as Figure 2 As shown in Table 4, the slope strata and soil are divided into regions, and the rock layers are classified according to the detection depth.

[0103] 2.2. Based on the original soil and rock samples, indoor experiments were carried out, including direct shear test and triaxial shear test, to determine the density, cohesion (c value), and internal friction angle (φ value) of the rock and soil mass, as shown in Table 3;

[0104] Table 3 Soil internal parameters

[0105]

[0106]

[0107] 2.3. According to the divided stratum area, the acoustic wave test is carried out, and the shear wave velocity is tested by using the drilled core specimen. The shear wave velocity test adopts the single-hole shear wave velocity method (layer detection method), reads the measured waveforms in the positive and negative directions, finds the intersection of the waveforms, reads the propagation time of the first arrival wave, and calculates the shear wave velocity value of each measuring point (layer) according to the formula, thereby calculating the equivalent shear wave velocity value of the soil layer;

[0108] 2.3.1、Shear wave velocity calculation formula:

[0109]

[0110] v se =d 0 / t;

[0111]

[0112] Among them, v i is the shear wave velocity of the soil layer from the i-1th point to the ith point; H i The depth of the i-th point; H i-1 The depth of the i-1th point; d i Calculate the thickness of the i-th soil layer within the depth range; s is the distance from the center of the excitation plate to the center of the hole; t i Arrival time of shear wave at point i; t i-1 Arrival time of shear wave at point i-1; v se Equivalent shear wave velocity of soil layer; d 0 Calculation depth; t is the propagation time of shear wave from the ground to the calculation depth; v is the propagation time of shear wave from the ground to the calculation depth si Calculate the shear wave velocity of the i-th soil layer within the depth range; n calculates the number of layers of soil within the depth range;

[0113] 2.4. The longitudinal wave velocity of the rock mass is measured by the acoustic wave method. A one-transmitter and two-receiver downhole transducer is used. The interval between the transmitter and the receiver is 30 cm, and the interval between the receiver and the receiver is 20 cm. The acoustic wave information is transmitted and received along the well wall in the borehole (open hole with well fluid). The initial arrival time of the longitudinal wave is determined according to the waveform starting point in the waveform collected by the instrument, and the longitudinal wave velocity is calculated.

[0114] 2.4.1. Calculation formula of longitudinal wave velocity:

[0115]

[0116]

[0117]

[0118]

[0119]

[0120] Where E d ,μ,G d ,Q d and ρ are the dynamic elastic modulus, Poisson's ratio, dynamic shear modulus, dynamic bulk modulus and density of the rock mass, respectively; V p ,V s are the propagation velocities of longitudinal and transverse waves in the rock mass, respectively. From the formula, we can see that after measuring ρ, we only need to measure V p , V s , the dynamic modulus and Poisson's ratio of the rock mass can be calculated, as shown in Table 5.

[0121] Table 4 Soil transverse and longitudinal wave velocities

[0122] Strata type Depth(m) Average shear wave velocity (m / s) Average longitudinal wave speed (m / s) Gravel layer 1-10 366.3 669.0 Completely weathered mudstone 11-14 525.8 1110.2 Completely weathered carbonaceous mudstone 15-19 545.8 1210.6 Completely weathered mudstone 20-21 595.5 1537.5 Strongly weathered sandstone 22-30 744.3 1804.9

[0123] Table 5 Soil structure parameters

[0124]

[0125] Step 3, determine the hydraulic parameters of the rock and soil mass under groundwater conditions;

[0126] 3.1. Conduct on-site surveys to understand the geographical location, topography, and vegetation coverage of the slope, collect regional geological and hydrogeological data, including geological structure, stratum lithology, groundwater flow direction, etc., and reasonably arrange monitoring wells in the slope area to ensure that the monitoring wells can represent the groundwater level in the area;

[0127] 3.2. Continuously monitor for a certain period of time (such as a hydrological year) to obtain sufficient data to analyze the changing pattern of groundwater levels; 3.3. Collect historical weather data for at least the past ten years, including parameters such as rainfall, snowfall, temperature, and humidity. The snowfall is estimated using the degree-day factor method;

[0128] 3.3.1. Degree-day model calculation formula:

[0129]

[0130] Among them, M s is the snowmelt thickness; DDF s is the degree-day factor, which is taken as 3 mm / (℃·d) by consulting the Xinjiang Geology and Hydrology Manual and related literature; T M is the daily average temperature, which is replaced by the monthly average temperature; T B It is the reference temperature, which is normally 0℃.

[0131] 3.4. Perform data preprocessing to remove erroneous records and inconsistent data, and use interpolation, mean substitution and other methods to fill in missing data;

[0132] 3.5. Classify the preprocessed data by month, count the rainfall and snowfall in each month, and use statistical methods such as box plots and histograms to analyze the distribution characteristics of rainfall and snowfall in each month. Determine the month with the maximum rainfall and snowfall in a year as shown in Table 1, and analyze the relationship between the maximum rainfall and snowfall and factors such as climate change and geographical location;

[0133] 3.6. Determine the permeability coefficient of different lithologies by consulting the regional moisture manual and indoor experiments, consult the regional moisture manual, collect data on the permeability coefficient of different lithologies, understand the physical and chemical properties of different lithologies, and their effects on the permeability coefficient;

[0134] 3.7. Select representative rock samples for indoor permeability experiments, measure the permeability coefficients of different rock types under laboratory conditions, control variables during the experiment to ensure the accuracy of the experimental results;

[0135] 3.8. Analyze the experimental data, determine the permeability coefficient under different lithology conditions, compare and analyze the experimental results with the data in the regional moisture manual, and verify the reliability of the experimental results;

[0136] Step 4: Slope finite element model seepage analysis;

[0137] 4.1. Combine steps 1 and 3 to build a model for the structure of the slope investigation experiment. In Geo-Studio software, select the Seep / W module to start building the model. In the graphical interface of Seep / W, use the drawing tools to draw the geometric shape of the slope according to the typical cross-sectional drawing of the slope, and define the size and boundary conditions of the model, including the height, width and distribution of different soil layers of the slope;

[0138] 4.2. Material property assignment: assign corresponding material properties to different soil layers of the model according to geological survey, such as saturated permeability coefficient, saturated volume water content, porosity, etc., define hydraulic parameters of different soil layers, soil-water characteristic curve and permeability function; 4.3. Mesh division: mesh the model to ensure that the mesh quality meets the calculation accuracy requirements, manually divide the mesh or use the automatic mesh generation function of the software;

[0139] 4.4. Combined with the data collection of meteorological conditions in step 1.5, different precipitation conditions are designed, with clear precipitation periods and water-off periods set, and the precipitation changes periodically, running two cycles, as shown in Table 6;

[0140] Table 6 Precipitation conditions

[0141] Time (h) Snowfall(mm) Heavy rainfall (mm) Mixed rainfall (mm) 12 20 44 20 24 20 44 20 36 20 44 20 48 20 44 20 60 20 44 20 72 20 44 20 84 20 0 0 96 20 0 0 108 20 0 0 120 20 0 0 132 20 0 44 144 20 0 44 156 20 0 44 168 20 0 44 180 20 0 0 192 20 0 0 204 20 44 0 216 20 44 0 228 20 44 0 240 20 44 0 252 0 44 0 264 0 44 0

[0142] 4.5. Boundary condition setting: Set the boundary conditions of the model, specify the water head, flow rate or permeability coefficient, etc. Set the rainfall boundary conditions on the upper boundary of the model. You can use a constant rainfall intensity or a variable intensity rainfall mode. Set the left, right and lower boundaries of the model as impermeable boundaries. When the rain stops, set the upper boundary as a zero flow boundary to ensure that rainwater can be discharged from the soil.

[0143] 4.6. In the model, the precipitation infiltration area, landslide-prone area and precipitation infiltration area are divided and these areas are distinguished by different colors or layers;

[0144] 4.7. Select multiple observation points on the surface of three different areas of the slope and set them using the "Observation Point" tool in Seep / W to ensure that the observation points cover different soil layers and key areas;

[0145] 4.8. Perform seepage state analysis, run the model, monitor and record the 24-hour soil pore water pressure changes at each observation point as shown in Table 7, analyze the distribution and changes of pore water pressure under different rainfall stages, obtain the seepage field distribution, check and analyze the seepage path, flow rate and pore water pressure of the model;

[0146] Table 7 Changes in pore water pressure at observation points

[0147]

[0148] By observing the changes of pore water pressure over time in detail, it is found that the changes of pore water pressure at the infiltration zone of the slope show different degrees of rise and fall with the increase of rainfall intensity and the arrival of the rain-free period. This phenomenon can be attributed to the fact that the infiltration zone has a large permeability coefficient and porosity. In the early stage of rainfall, the gravel layer has a large matrix suction and water absorption capacity, as well as a fast drainage capacity, which makes its pore water pressure show a negative growth during the rain-free period.

[0149] The changes in the lower layer of rock are relatively small, and its porosity and permeability coefficient are small. At the same time, due to the large slope of the infiltration zone, the infiltrated water will flow downward along the soil-rock interface and eventually accumulate in the landslide area, resulting in no obvious changes.

[0150] Step 5: Slope stability analysis:

[0151] 5.1. Switch to the Slope / W module, import the seepage results of the Seep / W module, set different analysis types in Slope / W, such as the limit equilibrium method, Swedish arc method, Bishop method, etc., input parameters such as the density, cohesion, internal friction angle between different rock and soil layers, as shown in Table 3, run the stability analysis, and calculate the safety factor of the slope under different working conditions, as shown in Table 8;

[0152] Table 8 Safety factors under different working conditions

[0153] Time (day) Working condition one safety factor Safety factor for working condition 2 Working condition three safety factors 0 1.529 1.529 1.529 1 1.488 1.518 1.518 2 1.426 1.46 1.46 3 1.389 1.334 1.384 4 1.319 1.313 1.363 5 1.269 1.295 1.343 6 1.221 1.28 1.271 7 1.182 1.262 1.205 8 1.121 1.246 1.134 9 1.081 1.175 1.141 10 1.038 1.094 1.139 11 1.058 1.01 1.137 12 1.076 1.063 1.134 13 1.082 1.073 1.132 14 1.109 1.1 1.13

[0154] 5.2. Analyze the stability analysis results provided by the Slope / W module, including the potential slip surface, minimum safety factor, and slope stability changes under different rainfall conditions. Combine the seepage analysis results with the stability analysis results to reveal the slope seepage trend and the changing law of the safety factor. The slope safety factor gradually decreases with precipitation and slowly increases after the rain stops completely, which indicates that the impact of rainfall on slope stability has a cumulative effect.

[0155] Step 6: Modify the model and conduct feedback analysis based on the simulation results:

[0156] 6.1. Preliminary result evaluation: check the path of water flow in the soil through streamline diagram to confirm whether it is consistent with the expected flow direction; analyze the velocity contour map or vector map to ensure that the magnitude and distribution of the velocity conform to the physical laws; check the pore water pressure contour map to verify whether the pressure distribution is reasonable, especially in key areas such as the slope foot and potential slip surface; compare the simulated groundwater level with the field observation data to check whether their change trends and values ​​match;

[0157] 6.2. Data comparison: compare the simulated key parameters such as seepage path, flow velocity, pore water pressure and groundwater level with the field observation data, record the inconsistencies between the simulation results and the field data, analyze the possible reasons, quantify the errors found in the comparative analysis, and evaluate their impact on the overall model prediction;

[0158] 6.3. Based on the preliminary evaluation results, make necessary corrections to the model. The following are the specific correction steps: Review the material properties of each layer of soil, such as permeability coefficient and porosity, and make adjustments if necessary. If the field data or experimental results provide new information, update the model parameters to reflect the actual situation. Check and optimize the boundary condition settings, such as rainfall infiltration, groundwater level, etc., to ensure that the boundary conditions are closer to the actual situation. Consider the impact of different rainfall stages on the boundary conditions, and adjust the boundary conditions to simulate the actual rainfall process.

[0159] 6.4. Re-run the model. After the correction is completed, re-run the model to verify the effect of the correction. Record the simulation results after each correction and compare them with the previous simulation results. Evaluate the overall reliability of the model after correction, including the stability and sensitivity analysis of the model prediction. By comparing the results before and after correction, analyze the specific impact of the model correction on the prediction results. Record the process and results of each iteration to ensure continuous improvement of the model.

Claims

1. A slope stability analysis method based on geotechnical characteristics, characterized in that: The following steps are involved: S1. Conduct detailed investigation on the geological structure, rock and soil type and distribution characteristics of the slope, and analyze the physical properties of the rock and soil, such as density, water content, porosity, etc.; S2. Conduct indoor and outdoor tests to obtain mechanical parameters of rock and soil, such as shear strength (c, φ value), elastic modulus, Poisson's ratio, etc.; S3. Investigate the influence of groundwater level change, rainfall infiltration and groundwater flow on slope stability, and analyze the change of rock and soil strength under different hydrogeological conditions; S4. Establishment of stability analysis model: Based on the geological survey and parameter test results, establish a suitable slope stability analysis model, such as limit equilibrium method, finite element method, discrete element method, etc., and consider the simulation of boundary conditions, initial stress state, and constitutive relationship by different models; S5. Use the established model to calculate stability, obtain the safety factor or directly conduct stability evaluation, and analyze the slope stability under different working conditions, such as natural state, heavy rain, snowfall, etc.; S6. Conduct model analysis on slope displacement, seepage, groundwater, etc., collect data, and perform model modification and feedback analysis based on simulation results.

2. A slope stability analysis method based on rock and soil characteristics according to claim 1, characterized in that: The step S1 specifically includes the following steps: S11. Collect regional basic geographic information data, including basic regional area data and slope transverse and longitudinal lengths; S12. Collect slope topography data, including regional environmental geomorphic characteristics, terrain shape characteristics, ground crack distribution, and hydrological distribution characteristics; S13. Collect ground elevation data, including the total height from the slope foot to the slope top and the inclination angle of each part; S14. Collecting data sets of stratum geotechnical characteristics, including the depth distribution characteristics of underground rock layers of the slope, rock layer strength parameters, and rock layer hydraulic parameters; S15. Collect historical weather data sets, including regional average monthly precipitation, average temperature distribution, and average snowfall over the past decade.

3. The rock formation strength parameter according to claim 2, characterized in that: The step S14 specifically includes the following steps: S141, calculate the longitudinal wave velocity by using the in-hole acoustic wave test, test the shear wave velocity by drilling core specimens, and further calculate the rock and soil strength parameters according to the elastic wave theory; Among them, E d ,μ,G d , Q d and ρ are the dynamic elastic modulus, Poisson's ratio, dynamic shear modulus, dynamic bulk modulus and density of the rock mass, respectively; V p , V s are the propagation velocities of longitudinal and transverse waves in the rock mass, respectively. From the formula, we can see that after measuring ρ, we only need to measure V p , V s , the dynamic modulus and Poisson's ratio of the rock mass can be calculated.

4. The slope stability analysis method based on rock and soil characteristics according to claim 1 is characterized in that: The step S2 constructs a basic model framework of the highway slope based on AutoCAD for the basic geographic information data, topographic data, ground elevation data, and stratum rock and soil characteristic data set collected in step S1, and determines the rock and soil distribution characteristics of the slope; S21. Construct a slope model framework at a scale of 1:500 according to the length of the slope's transverse and longitudinal planes, the terrain shape, the total height of the slope, and the inclination angles of each part; S22. Conduct a detailed analysis of the rock distribution characteristics in the study area, including rock type, thickness, lithology, permeability and other parameters, to determine the degree of influence of rock on slope stability; S23. According to the distribution characteristics of rock strata, in the constructed slope model framework, the model is divided into multiple rock strata units according to the depth of the rock strata to more accurately simulate the influence of the rock strata on the slope stability.

5. The slope stability analysis method based on rock and soil characteristics according to claim 1 is characterized in that: The step S3 determines the permeability curve law of each soil layer and rock layer based on the soil-water characteristic curve of the Fredlund-Xing method for the stratum rock and soil characteristic data set collected in step S1; S31, calculating soil-water characteristic curves of each rock layer; Where, θ is the volumetric water content; θ s is the residual moisture content; S is the saturated matrix suction; S r is the matrix suction corresponding to the residual water content; e is the soil porosity ratio; a is the influencing parameter of soil pore size distribution; m and n are shape parameters; S32. Calculate the shear strength of soil and rock formations; Among them, τ f is the shear stress; c′ is the effective cohesion; σ n is the normal total stress; u w is the pore water pressure; Effective internal friction angle; is the internal friction angle that changes with matrix suction; u a is the pore gas pressure.

6. The highway network gradient optimization method based on big data according to claim 1 is characterized in that: The step S4 specifically comprises the following steps: S51, import the highway slope rock layer segmentation nodes constructed by Auto CAD into Geo studio analysis software as a finite element model framework; S52. According to the field survey results and calculated values, corresponding parameters are set for each rock formation unit, including the rock formation's density, cohesion, internal friction angle, permeability coefficient, etc., to reflect the physical and mechanical properties of the rock formation; S53, adjusting the model parameters according to the actual distribution of the rock layer and the lithology changes, so as to more accurately simulate the stability state of the slope; S54, inputting the design conditions (such as different rainfall intensities and durations) into the slope model as boundary conditions to simulate the impact of actual rainfall on the slope. After the rainfall condition ends, a certain water stop period is set as a control test to observe the change of pore water pressure inside the slope and analyze the recovery process of slope stability after the rainfall ends; S55. Divide the model into infiltration zone, landslide zone, and seepage zone, and set two observation points in each zone to monitor the changes in pore water pressure; S56. Perform saturated-unsaturated seepage analysis on the model.

7. The characteristic parameter according to claim 7, characterized in that: The step S56 specifically includes the following steps: S561, saturated-unsaturated seepage: i, j = 1, 2, 3. in, is the saturated permeability tensor; K r (h c ) is the negative pressure head h c It is a function of the unsaturated hydraulic conductivity K, whose value is 1 in the saturated zone and between 0 and 1 in the unsaturated zone; ω is the sink index; C is the water capacity.

8. The slope stability analysis method based on rock and soil characteristics according to claim 1 is characterized in that: The step S5 designs weather condition characteristics under different extreme conditions for the historical weather data set collected in step S1; S41. The historical weather is divided into the cumulative monthly average precipitation, the cumulative monthly maximum precipitation, the cumulative monthly minimum precipitation, the cumulative monthly maximum daily precipitation, and the monthly maximum snowfall; S42. Design extreme operating conditions based on maximum rainfall and snowfall, and implement them repeatedly in a periodic manner.

9. A slope stability analysis method based on rock and soil characteristics, characterized in that: include: Comprehensive analysis of the microstructure and macroscopic mechanical properties of slope rock and soil; Use advanced in-situ testing technology to obtain real-time mechanical parameters of rock and soil; Combining the nonlinear finite element method and the strength reduction method, a stability analysis model is established that can take into account the time dependence and anisotropy of the rock and soil constitutive model. By adjusting model parameters through real-time monitoring data feedback, dynamic management and prediction of slope stability evaluation can be achieved.

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