CN109408944A - Expansive soil slope failure by leaking method for analyzing stability based on complete softening intensity - Google Patents

Abstract

The invention discloses a method for analyzing the shallow sliding stability of expansive soil slope based on complete softening strength. The physical and mechanical parameters are obtained from the soil strength test; the fissure depth and the height of the wetting line are determined according to the hydrogeological data; the expansive soil slope is modeled according to the physical and mechanical parameters, the depth of the fissure and the height of the wetting line, and the seepage analysis model is obtained; the seepage analysis model Conduct the stability analysis of the first landslide to obtain the stability results; simulate the traction failure process of the seepage analysis model to obtain the landslide characteristic analysis results; Slope design and construction. Beneficial effects: The method can correctly describe the failure process of the actual expansive soil slope, and can reflect the instability mechanism of the expansive soil slope.

Description

Analysis method of shallow sliding stability of expansive soil slope based on fully softened strength

technical field

The invention relates to a stability analysis method, in particular to a method for analyzing the shallow sliding stability of expansive soil slopes based on complete softening strength, and belongs to the field of geotechnical engineering soil slope stability, especially the application research field of expansive soil slope stability analysis.

Background technique

Due to the sensitivity of expansive soil to changes in environmental factors, the expansive soil expansiveness and shear strength are complex and changeable, and the failure mechanism and landslide characteristics of expansive soil slopes are different from those of ordinary soil slopes. When the stability of expansive soil slope is analyzed by the conventional method of slope stability analysis such as the slice method, the calculation results are often quite different from the actual situation in terms of safety degree and landslide form. Therefore, it is determined that it is suitable for expansive soil slope. The stability analysis method is very important.

There are two kinds of commonly used slope stability analysis methods, one is the limit equilibrium method; the other is the finite element method. In order to determine the stability analysis method suitable for expansive soil slope, many scholars have improved the limit equilibrium method and the finite element method based on the conventional method, and made a lot of efforts.

This paper summarizes the calculation methods of expansive soil slopes improved by many scholars, mainly from the following two aspects: one is to use residual strength or dry-wet cycle strength; Physical or surface forces are applied when using the finite element method. Although the improved method can satisfy the stability analysis of expansive soil slope to a certain extent, it still has some shortcomings.

All over-consolidated soils have residual strength. There is no theoretical basis for using residual strength in the stability analysis of expansive soil slopes, and the first failure of the slope is mainly considered when analyzing the stability of expansive soil slopes, while the residual strength is the result of repeated shearing. Strength after cutting; dry-wet cycles lead to the development of cracks, and cracks lead to strength reduction. Therefore, some scholars study the strength of expansive soil through dry-wet cycle tests, and relate the strength to the number of dry-wet cycles. The stability analysis uses a certain number of dry-wet cycles. Strength of. Although the strength under dry-wet cycle conditions can reflect the strength characteristics of expansive soil, the number of dry-wet cycles in the actual environment cannot be defined and can only be controlled indoors; The expansion force is introduced into the form, and the expansion force is applied to the slope as an external force. The expansion force belongs to the internal force. This way of considering the expansion force is inconsistent with the actual situation; Moreover, the landslide is caused by the gradual upward traction after the partial failure of the slope foot, and the current stability analysis method of expansive soil slope cannot correctly describe the failure process of the actual expansive soil slope; for the safety evaluation of expansive soil slope, there are currently The study only takes the safety factor at the first sliding as the safety evaluation standard for expansive soil slopes. In fact, expansive soil slopes and landslides have multiple sliding surfaces from bottom to top, and the process of expansive soil traction landslides needs to be studied.

SUMMARY OF THE INVENTION

The main purpose of the present invention is to overcome the deficiencies in the prior art, and to provide a method for analyzing the shallow sliding stability of expansive soil slopes based on complete softening strength, which can correctly describe the failure process of the actual expansive soil slopes, and can reflect the expansive soil slope. The instability mechanism of soil slopes can reflect the characteristics of gentleness, shallowness, traction, long-term, seasonality and directionality of expansive soil slopes and landslides.

In order to achieve the above object, the technical scheme adopted in the present invention is:

The analysis method of shallow sliding stability of expansive soil slope based on full softening strength includes the following steps:

1) Carry out on-site investigation and investigation on expansive soil slopes to obtain soil samples and hydrogeological data;

2) Carry out the expansive soil strength test on the soil sample to obtain physical and mechanical parameters; wherein, the expansive soil strength test includes the original shear strength test and the complete softening strength test;

3) Determine the depth of the fissure and the height of the wetting line according to the hydrogeological data;

4) Model the expansive soil slope according to the physical and mechanical parameters, the depth of the fissure and the height of the wetting line, and obtain the seepage analysis model;

5) Carry out the stability analysis of the first landslide on the seepage analysis model, and obtain the stability results;

6) Simulate the traction progressive failure process of the seepage analysis model, and obtain the analysis results of the landslide characteristics;

7) Based on the stability results that can reflect the instability mechanism of expansive soil slopes and the analysis results of landslide characteristics, guide the design and construction of expansive soil slopes.

The present invention is further configured as follows: the on-site field survey and investigation in the step 1) includes arranging the hydrogeological data on the site and sampling the soil body on the site.

The present invention is further set as: the undisturbed shear strength test in the step 2), specifically, taking the unweathered expansive soil sample in its original state to carry out the shear strength test under saturated consolidation and undrained conditions, and according to the test results Obtain the shear strength parameters of the soil sample under saturated consolidation and undrained conditions, which are the original cohesion c ₀ and the original internal friction angle, respectively

The present invention is further set as: the complete softening strength test in the step 2), specifically, taking the original unweathered expansive soil sample to carry out the complete softening strength test, and obtaining the soil sample under the complete softening condition according to the test result. The shear strength parameters are the fully softened cohesion c _f and the fully softened internal friction angle, respectively

The present invention is further provided as follows: determining the depth of the fissure in the step 3), that is, determining the development depth of the fissure area as the fissure depth h _c according to the hydrogeological data. The maximum depth that can be expected to be reached is taken as the crack depth h _c , and for permanent slopes, the maximum depth that the crack can reach is taken as the crack depth h _c ; , because the surface fissures are mature and meet the representative requirements of the survey data, the fissure depth is taken according to the measured data; for newly excavated or newly filled slopes, the fissures in the surveyed soil layer are still in the development stage. If the data is not representative, the fissure depth is taken as 4m according to the survey statistics of the nearby soil layers.

The present invention is further set as: determining the height of the wetting line in the step 3), specifically,

For the existing slopes whose formation time of the surveyed soil layer has reached the development period, the actual height position of the infiltration line is monitored and determined as the infiltration line height by the monitoring instrument embedded in the field;

For newly excavated or newly filled slopes, the approximate estimated height position is taken as the height of the infiltration line through the survey statistics of the nearby soil layers;

Among them, the height of the wetting line is the position of the toe of the slope or the actually reached position of the slope or the top of the slope distributed along the slope.

The present invention is further set as: modeling the expansive soil slope in the step 4), specifically,

4-1) Establish the geometric model of the slope;

4-2) According to the depth of the fissure, the slope in the slope geometric model is divided into sections;

The slope is divided into three layers along the depth direction, the first layer is the fully developed layer with cracks, and the depth is taken as 2h _c /3; the second layer is the layer with insufficient cracks, and the depth is taken as h _c /3; the third layer is the non-cracked layer zone; the first layer and the second layer constitute the fissure zone;

4-3) Assign soil strength to different zones;

For the fracture area, take the fully softened cohesion c _f and the fully softened internal friction angle The shear strength parameters of the soil in the fully developed cracked layer are assigned, and the average value of the original cohesion c ₀ and the fully softened cohesion c _f and the original internal friction angle are taken. with fully softened internal friction angle The average value of the value of the shear strength parameter of the soil in the underdeveloped cracked layer is assigned, then the cohesion of the underdeveloped cracked layer is determined. Internal friction angle of underdeveloped fissures

For the non-cracked area, take the original cohesion c ₀ and the original internal friction angle Assign value to shear strength parameters of soil in non-crack area;

Among them, the original cohesion c ₀ and the original internal friction angle are the shear strength parameters of the soil sample under saturated consolidation and undrained conditions, the fully softened cohesion c _f and the fully softened internal friction angle is the shear strength parameter of the soil sample under the condition of complete softening;

4-4) Set the position of the wetting line according to the height of the wetting line. The sliding moment of the soil below the wetting line is calculated by the saturated bulk density, and the anti-slip moment of the soil below the wetting line is calculated by the floating bulk density;

4-5) Based on the soil strength assignment and the setting of the wetting line position on the slope geometric model, the seepage analysis model is obtained by reconstruction.

The present invention is further provided as follows: the stability analysis, specifically, considering deep sliding and shallow sliding, local sliding and overall sliding, selecting the type of sliding arc for the slope foot in the seepage analysis model, and checking the instability of the expansive soil slope. Dangerous slip arc; further, based on different wetting line heights and different slip arc types, check and calculate the position of the wetting line where the expansive soil slope is unstable; among them, deep sliding means that the sliding surface penetrates below the depth of the fissure, and shallow sliding means that the sliding surface is limited within the fissure depth.

The present invention is further configured as follows: in the step 6), a traction-type progressive failure process simulation is performed, specifically, after the first landslide occurs, the landslide body is removed; the first landslide in the step 6) will form a stable seepage due to the accumulation of rainwater at the foot of the slope. At the foot of the slope; after the foot of the slope landslide, conduct the second stability analysis, and so on, until the landslide develops to the top of the slope.

Compared with the prior art, the present invention has the following beneficial effects:

The method provided by the invention starts from the slope soil layer division, the value of soil strength parameters, the determination of the wetting line, etc., and carries out limit equilibrium method calculation by adopting a seepage model that can reflect the effect of cracks with complete softening strength and reasonable seepage. The analysis of the expansive soil slope stability can simulate the progressive failure process of the expansive soil slope. The calculation results can reflect the instability mechanism of the expansive soil slope, and can reflect the gentleness, shallowness and traction of the expansive soil slope and landslide. , long-term, seasonal, directional and other characteristics.

The above content is only an overview of the technical solutions of the present invention. In order to understand the technical means of the present invention more clearly, the present invention will be further described below with reference to the accompanying drawings.

Description of drawings

Fig. 1 is the flow chart of the method of the present invention;

Fig. 2 is the schematic diagram of determining fissure depth in the method of the present invention;

Fig. 3 is the schematic diagram of determining the change of wetting line in the method of the present invention;

4 is a schematic diagram of determining the height of the wetting line in the method of the present invention;

Fig. 5 is the schematic diagram of slope partition in the method of the present invention;

FIG. 6 is a schematic diagram of the progressive failure of the slope in the method of the present invention.

Detailed ways

The present invention will be further described below with reference to the accompanying drawings.

The present invention provides a method for analyzing the shallow sliding stability of expansive soil slope based on complete softening strength, as shown in Figure 1, comprising the following steps:

1) Carry out on-site investigation and investigation on expansive soil slopes to obtain soil samples and hydrogeological data.

On-site field investigation and investigation include sorting out the hydrogeological data on the site and sampling the soil mass on the site.

2) Carry out the expansive soil strength test on the soil sample to obtain physical and mechanical parameters; wherein, the expansive soil strength test includes the original shear strength test and the complete softening strength test;

Undisturbed shear strength test, specifically, take the original unweathered expansive soil sample for shear strength test under saturated consolidation and undrained conditions, and obtain the resistance of the soil sample under saturated consolidation and undrained conditions according to the test results. shear strength parameters, respectively the original cohesion c ₀ and the original internal friction angle

Complete softening strength test, specifically, take the original unweathered expansive soil sample for complete softening strength test, and obtain the shear strength parameters of the soil sample under the completely softened condition according to the test results, which are respectively the completely softened cohesion c _f and the fully softened internal friction angle The soil samples were obtained through the complete softening strength test to obtain the complete softening strength parameters required for the calculation.

3) Determine the depth of the fissure and the height of the wetting line according to the hydrogeological data.

Determining the fissure depth, that is, determining the development depth of the fissure area as the fissure depth h _c according to the hydrogeological data. Specifically, for the temporary slope, the maximum depth that the fissure can reach within the design life period is used as the fissure depth h _c . For permanent slopes, the maximum depth that the fissure can reach is taken as the fissure depth h _c ; among them, the temporary slope is the slope that will not be used after excavation for a short time, and the permanent slope is the one that will be used for a long time. slope;

or,

For the existing slope whose formation time of the surveyed soil layer has reached the development period, because the surface cracks are mature and meet the representative requirements of the survey data, the crack depth is taken according to the measured data, as shown in Figure 2; for new excavation Or the newly filled slope, because the fissures in the surveyed soil layer are still in the development stage, and the survey data is not representative, the fissure depth is taken as 4m according to the survey statistics of the nearby soil layers.

Under the influence of seepage, the seepage formed by rainfall infiltration in the slope is an important factor affecting the occurrence of landslides in expansive soil slopes. On the one hand, the accumulation of rainwater at the foot of the slope reduces the strength of the soil mass, and on the other hand, it generates a relatively obvious seepage force when the stable seepage is formed, so the foot of the slope is easy to slide to form a local landslide. The schematic diagram of the change of the wetting line is shown in Figure 3; The location of the rainwater is related to the rainfall intensity and length. In the case of high intensity and long time, the height of the infiltration line may reach the top of the slope, and the infiltration line runs along the entire slope; under the condition of normal rainfall intensity and length, the rainwater gathers at the foot of the slope to form seepage. , the height of the wetting line is located near the toe of the slope, so the position of the wetting line has certain variability and randomness.

Determine the wetting line height, as shown in Figure 4, the wetting line height h _w , specifically,

For the existing slopes whose formation time of the surveyed soil layer has reached the development period, the actual height position of the infiltration line is monitored and determined as the infiltration line height by the monitoring instrument embedded in the field;

For newly excavated or newly filled slopes, the approximate estimated height position is taken as the height of the infiltration line through the survey statistics of the nearby soil layers;

Among them, the height of the wetting line is the position of the toe of the slope or the actually reached position of the slope or the top of the slope distributed along the slope.

4) According to the physical and mechanical parameters, the depth of the fissure and the height of the wetting line, the expansive soil slope is modeled, and the seepage analysis model is obtained.

Modeling expansive soil slopes, specifically,

4-1) Establish the geometric model of the slope;

4-2) According to the depth of the fissure, the slope in the slope geometric model is divided into sections;

The slope is divided into 3 layers along the depth direction, as shown in Figure 5, the first layer is the layer with fully developed fissures, and the depth is taken as 2h _c /3; the second layer is the layer with insufficient development of fissures, and the depth is taken as h _c /3; The third layer is a non-crack area; the first layer and the second layer constitute a crack area;

4-3) Assign soil strength to different zones;

For the fracture area, take the fully softened cohesion c _f and the fully softened internal friction angle The shear strength parameters of the soil in the fully developed cracked layer are assigned, and the average value of the original cohesion c ₀ and the fully softened cohesion c _f and the original internal friction angle are taken. with fully softened internal friction angle The average value of the value of the shear strength parameter of the soil in the underdeveloped cracked layer is assigned, then the cohesion of the underdeveloped cracked layer is determined. Internal friction angle of underdeveloped fissures

For the non-cracked area, take the original cohesion c ₀ and the original internal friction angle Assign value to shear strength parameters of soil in non-crack area;

Among them, the original cohesion c ₀ and the original internal friction angle are the shear strength parameters of the soil sample under saturated consolidation and undrained conditions, the fully softened cohesion c _f and the fully softened internal friction angle is the shear strength parameter of the soil sample under the condition of complete softening;

4-4) Set the position of the wetting line according to the height of the wetting line. The sliding moment of the soil below the wetting line is calculated by the saturated bulk density, and the anti-slip moment of the soil below the wetting line is calculated by the floating bulk density;

4-5) Based on the soil strength assignment and the setting of the wetting line position on the slope geometric model, the seepage analysis model is obtained by reconstruction.

Step 4) is to calculate the slope stability by using the limit equilibrium method after modeling.

5) The stability analysis of the first landslide is carried out on the seepage analysis model, and the stability results are obtained.

The stability analysis, specifically, considers deep slip and shallow slip, local slip and overall slip, selects the slip arc type for the slope toe in the seepage analysis model, and checks and calculates the dangerous slip arc of expansive soil slope instability; Different wetting line heights and different sliding arc types are used to check and calculate the position of the wetting line where the expansive soil slope is unstable; among them, deep sliding means that the sliding surface penetrates below the depth of the fissure, and shallow sliding means that the sliding surface is limited within the depth of the fissure.

Due to the large volume and large sliding moment of the sliding body in deep sliding, if the strength index difference between the cracked area and the non-cracked area is not very significant, there may also be dangerous deep sliding. Deep slip may also occur if there are other soil layers with low strength underneath, or if there are obvious deep weak zones. Therefore, although the instability of expansive soil slopes is generally shallow, the deep sliding surface still needs to be checked. The deep sliding calculation is common to the method of the present invention and the traditional method, and the method of the present invention can calculate the shallow sliding in addition to the calculation of the deep sliding.

6) Simulate the progressive failure process of traction type on the seepage analysis model, and obtain the analysis results of the characteristics of the landslide.

Carry out the simulation of traction-type progressive failure process, specifically, remove the landslide body after the first landslide occurs; the first landslide will appear at the toe of the slope due to the accumulation of rainwater to form a stable seepage; after the landslide at the foot of the slope, conduct the second time Stability analysis, and so on, until the landslide develops to the top of the slope. As shown in Figure 6, Figure 6-(a) is a schematic diagram of the first landslide, Figure 6-(b) is a schematic diagram of the second landslide, Figure 6-(c) is a schematic diagram of the third landslide, Figure 6 -(d) is the schematic diagram of the fourth landslide, Figure 6-(e) is the schematic diagram of the fifth landslide, Figure 6-(f) is the schematic diagram of the sixth landslide, and Figure 6-(g) is the seventh landslide Schematic diagram of the landslide, Figure 6-(h) is a schematic diagram of the overall view of the landslide. The landslide of the expansive soil slope is a typical traction failure process. Step 5) The stability analysis of the first landslide is the analysis of the first failure of the slope toe, and the first failure provides the basis for the traction failure in the subsequent step 6). Progressive failure Process simulation is a part of the entire stability analysis, that is, there is the first failure, then the traction failure, the first failure and the traction failure are the entire process of the expansive soil slope failure; step 6) obtains the overall safety factor of the expansive soil slope and The final landslide form, the results are used to guide the design and construction in step 7).

7) Based on the stability results that can reflect the instability mechanism of expansive soil slopes and the analysis results of landslide characteristics, guide the design and construction of expansive soil slopes.

The innovation of the present invention is that, starting from the slope soil layer division, the value of soil strength parameters, the determination of the wetting line, etc., the limit equilibrium method is used to calculate the limit equilibrium method by using a seepage model that can reflect the effect of cracks and a seepage model with a complete softening strength and a reasonable seepage. , analyze the stability of the expansive soil slope, and finally obtain the stability analysis results, including the safety factor and the characteristics of the landslide, which can correctly describe the failure process of the actual expansive soil slope and reflect the instability mechanism of the expansive soil slope. Therefore, it is helpful to guide the design and construction of expansive soil slope, and solve the problem that the analysis results of the traditional analysis method in the stability analysis of expansive soil slope cannot correctly reflect the safety and landslide characteristics of the actual expansive soil slope.

The foregoing has shown and described the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited by the above-mentioned embodiments, and the descriptions in the above-mentioned embodiments and the description are only to illustrate the principle of the present invention. Without departing from the spirit and scope of the present invention, the present invention will have Various changes and modifications fall within the scope of the claimed invention. The claimed scope of the present invention is defined by the appended claims and their equivalents.

Claims (9)

1. a method for analyzing the shallow sliding stability of expansive soil slope based on complete softening strength, is characterized in that, comprises the following steps: 1) Carry out on-site investigation and investigation on expansive soil slopes to obtain soil samples and hydrogeological data; 2) Carry out the expansive soil strength test on the soil sample to obtain physical and mechanical parameters; wherein, the expansive soil strength test includes the original shear strength test and the complete softening strength test; 3) Determine the depth of the fissure and the height of the wetting line according to the hydrogeological data; 4) Model the expansive soil slope according to the physical and mechanical parameters, the depth of the fissure and the height of the wetting line, and obtain the seepage analysis model; 5) Carry out the stability analysis of the first landslide on the seepage analysis model, and obtain the stability results; 6) Simulate the traction progressive failure process of the seepage analysis model, and obtain the analysis results of the landslide characteristics; 7) Based on the stability results that can reflect the instability mechanism of expansive soil slopes and the analysis results of landslide characteristics, guide the design and construction of expansive soil slopes. 2. the method for analyzing the shallow sliding stability of expansive soil slope based on complete softening strength according to claim 1, is characterized in that: the on-the-spot investigation and investigation in the described step 1) includes sorting out the hydrogeological data on the spot and soil sampling at the site. 3. the method for analyzing the shallow sliding stability of expansive soil slope based on complete softening strength according to claim 1, is characterized in that: the undisturbed shear strength test in the described step 2), specifically, take the original undisturbed The weathered expansive soil samples were subjected to a shear strength test under saturated consolidation and _undrained conditions. Undisturbed internal friction angle 4. the method for analyzing the shallow sliding stability of expansive soil slope based on complete softening strength according to claim 1, is characterized in that: the complete softening strength test in described step 2), specifically, take the undisturbed The weathered expansive soil sample is subjected to a complete softening strength test, and the shear strength parameters of the soil sample under the fully softened condition are obtained according to the test results, which are respectively the fully softened cohesion c _f and the fully softened internal friction angle 5. The method for analyzing the shallow sliding stability of expansive soil slopes based on complete softening strength according to claim 1, is characterized in that: in the described step 3), determining the depth of the fissure, i.e. determining the depth of the fissure area according to hydrogeological data. The development depth is taken as the fissure depth h _c . Specifically, for the temporary slope, the maximum depth that the fissure can reach within the design service life is adopted as the fissure depth h _c , and for the permanent slope, the maximum depth that the fissure can reach is adopted. as the fissure depth h _c ; or, for the existing slopes whose formation time of the surveyed soil layer has reached the development period, since the surface fissures are mature and meet the representative requirements of the survey data, the fissure depth is taken according to the measured data; For excavated or newly filled slopes, the survey data is not representative due to the fact that the fissures in the surveyed soil layer are still in the developing stage, and the fissure depth is taken as 4m according to the survey statistics of the nearby soil layers. 6. the method for analyzing the shallow sliding stability of expansive soil slope based on complete softening strength according to claim 5, is characterized in that: in the described step 3), determine the height of wetting line, specifically, For the existing slopes whose formation time of the surveyed soil layer has reached the development period, the actual height position of the infiltration line is monitored and determined as the infiltration line height by the monitoring instrument embedded in the field; For newly excavated or newly filled slopes, the approximate estimated height position is taken as the height of the infiltration line through the survey statistics of the nearby soil layers; Among them, the height of the wetting line is the position of the toe of the slope or the actually reached position of the slope or the top of the slope distributed along the slope. 7. The method for analyzing the shallow sliding stability of expansive soil slope based on complete softening strength according to claim 6, characterized in that: in the described step 4), the expansive soil slope is modeled, specifically, 4 -1) Establish a geometric model of the slope; 4-2) According to the depth of the fissure, the slope in the slope geometric model is divided into sections; The slope is divided into three layers along the depth direction, the first layer is the fully developed layer with cracks, and the depth is taken as 2h _c /3; the second layer is the layer with insufficient cracks, and the depth is taken as h _c /3; the third layer is the non-cracked layer zone; the first layer and the second layer constitute the fissure zone; 4-3) Assign soil strength to different zones; For the fracture area, take the fully softened cohesion c _f and the fully softened internal friction angle The shear strength parameters of the soil in the fully developed cracked layer are assigned, and the average value of the original cohesion c ₀ and the fully softened cohesion c _f and the original internal friction angle are taken. with fully softened internal friction angle The average value of the value of the shear strength parameter of the soil in the underdeveloped cracked layer is assigned, then the cohesion of the underdeveloped cracked layer is determined. Internal friction angle of underdeveloped fissures For the non-cracked area, take the original cohesion c ₀ and the original internal friction angle Assign value to shear strength parameters of soil in non-crack area; Among them, the original cohesion c ₀ and the original internal friction angle are the shear strength parameters of the soil sample under saturated consolidation and undrained conditions, the fully softened cohesion c _f and the fully softened internal friction angle is the shear strength parameter of the soil sample under the condition of complete softening; 4-4) Set the position of the wetting line according to the height of the wetting line. The sliding moment of the soil below the wetting line is calculated by the saturated bulk density, and the anti-slip moment of the soil below the wetting line is calculated by the floating bulk density; 4-5) Based on the soil strength assignment and the setting of the wetting line position on the slope geometric model, the seepage analysis model is obtained by reconstruction. 8. The method for analyzing the stability of shallow sliding of expansive soil slope based on full softening strength according to claim 1, characterized in that: the stability analysis, specifically, considers deep sliding and shallow sliding and local sliding and For overall sliding, select the slip arc type for the slope foot in the seepage analysis model, and check the dangerous slip arc of expansive soil slope instability; then, based on different infiltration line heights and different slip arc types, check and calculate the infiltration line of expansive soil slope instability Among them, deep sliding means that the sliding surface goes deep below the depth of the crack, and shallow sliding means that the sliding surface is limited within the depth of the crack. 9. The method for analyzing the shallow sliding stability of expansive soil slope based on complete softening strength according to claim 8, characterized in that: in the step 6), the simulation of a traction type progressive failure process is performed, specifically, in the step 6). After the first landslide occurs, remove the landslide body; the first landslide will appear at the foot of the slope due to the accumulation of rainwater to form a stable seepage; after the landslide at the foot of the slope, carry out the second stability analysis, and so on, until the landslide develops to the slope top.