CN110927360A

CN110927360A - Slope stability dynamic evaluation method based on rainfall seepage path and water content change

Info

Publication number: CN110927360A
Application number: CN201911202690.8A
Authority: CN
Inventors: 赵伟华; 李艾浓; 赵建军; 余建乐; 解明礼
Original assignee: Chengdu Univeristy of Technology
Current assignee: Chengdu Univeristy of Technology
Priority date: 2019-11-29
Filing date: 2019-11-29
Publication date: 2020-03-27

Abstract

The invention discloses a slope stability dynamic evaluation method based on rainfall seepage paths and water content changes, which comprises the steps of collecting slide soil on site, carrying out a physical mechanical strength test on the slide soil, and recording corresponding physical mechanical parameters; utilizing the collected slippery soil as a slope model to be evaluated and carrying out rainfall physical simulation on the slope model; and establishing a slope stability dynamic analysis model based on the rainfall seepage path and the water content change based on the physical mechanical parameters, the water content change condition and the pore water pressure change condition. The invention researches the way of rainwater entering the interior of the infiltration slope body, and speculates that the rainwater flows into the infiltration along the cracks to gradually soften the cracks and promote the cracks to develop. And rainwater can be simulated to flow into the infiltration along the crack by assigning values to the seepage path in sections, so that the crack is gradually softened to promote the process of penetration. The calculation result is more accurate and accords with the reality, and the defects that the traditional integral strength reduction method has large calculation error, is difficult to quantitatively evaluate and predict the slope deformation trend can be overcome.

Description

Slope stability dynamic evaluation method based on rainfall seepage path and water content change

Technical Field

The invention belongs to the technical field of slope or slope stability analysis of rainfall seepage influence, and particularly relates to a dynamic slope stability evaluation method based on rainfall seepage paths and water content changes.

Background

The slope of a rock body or a soil body is influenced by factors such as river erosion, underground water activity, earthquake, human activity and the like, and the phenomenon that the whole or part of the slope body slides downwards along a certain shearing sliding surface under the action of gravity is called landslide. Landslide geological disasters have the characteristics of difficult prediction, large harm, high engineering cost for treatment and the like, and landslide often causes huge casualties and property loss. In 1963, 10 and 9 days, huge landslides occur near a dam at the left bank of the Italian Wagan reservoir, the reservoir is damaged by the landslides, so that the reservoir can not be used any more, and the generated wave destroys many downstream towns, so 1925 people are in distress; the landslide caused by the earthquake of Wenchuan in 2008 causes immeasurable loss, for example, landslide of Daguan Bao mountain in Anxian county, landslide of New North China school, and landslide of Wen's ditch cause thousands of people to die, and unmeasurable economic loss; in 2009, 6 and 5 days, the Chinese cocktail mountain of Wulong, Chongqing city generates landslide with the amount of 700 ten thousand cubic meters, and the landslide forms debris flow to cause 74 people to die; 11 th day 20 of 12 th of 2015, 40 minutes, and an artificial mound landslide is formed in the Shenzhen Guangming New region Taiyu industrial park, which causes 90 people to die. Because of the great destructiveness of landslide, landslide research is always the key point of engineering geology.

The roadbed slopes are important components of the highway and comprise excavated cutting slopes and filled embankment slopes. Comprehensive protection of subgrade slopes has been a common research subject in highway construction for a long time, but the development degree is low. Before the middle of the 80 s, China mainly builds low-grade roads, filling excavation is less, investment in road construction is less, so that the problem of stability of a roadbed slope is relatively less, the attention of people to the problem of the roadbed slope is less, slope protection engineering cannot be used as a main part of road construction, and the slope protection engineering is often ignored in road engineering construction. After the 90 s, China begins to build a plurality of high-quality roads and encounters a plurality of slope stability problems caused by deep foundation filling and excavation. In the early 90 s, the slope protection and reinforcement treatment still mainly refers to the slope engineering technology of low-grade roads and the treatment experience teaching of local government railway departments to carry out local treatment. Projects often involve various problems due to lack of comprehensive considerations for slope management. For example, the sinking highway and the deep-Shan highway built in the early period all collapse on the road base side slope after the vehicle is communicated, which causes huge economic loss and adverse social influence. The spanish mackerel encloses a sunken highway section with a length of 180km, and 80% of the whole engineering control cost is used for slope management engineering. The landslide section of the deep Shan expressway is short of 2km, and the landslide control cost is up to 1 hundred million Yuan. In the construction of high-grade highways, because of insufficient funds, relative lag of technical means and insufficient awareness of protecting the highway environment, a plurality of comprehensive treatment problems of roadbed slopes are left in the areas along the highway without emphasizing the ecological protection of the highway.

Therefore, it is urgently needed to provide a dynamic evaluation method for slope stability based on rainfall seepage paths and water content changes to solve the above problems.

Disclosure of Invention

The invention aims to provide a method and a system for dynamically evaluating slope stability based on rainfall seepage paths and water content changes, which are used for solving the technical problems in the prior art, such as: in the construction of high-grade highways, because of insufficient funds, relative lag of technical means and insufficient awareness of protecting the highway environment, a plurality of comprehensive treatment problems of roadbed slopes are left in the areas along the highway without emphasizing the ecological protection of the highway.

In order to achieve the purpose, the technical scheme adopted by the invention is as follows:

a slope stability dynamic evaluation method based on rainfall seepage paths and water content changes comprises the following steps:

s1: carrying out engineering geological survey on a slope to be evaluated to obtain basic characteristics of the slope, collecting the zonal soil on site, carrying out a physical mechanical strength test on the zonal soil, and recording corresponding physical mechanical parameters;

s2: on the basis of the step S1, utilizing the collected slip soil as a slope model to be evaluated, carrying out rainfall physical simulation on the slope model, monitoring the change condition of the water content and the change condition of the pore water pressure of different positions of the slope model to be evaluated, and recording the corresponding change condition of the water content and the change condition of the pore water pressure;

s3: and establishing a slope stability dynamic analysis model based on the rainfall seepage path and the water content change based on the physical mechanical parameters, the water content change condition and the pore water pressure change condition, and comparing the analysis results of different stages of the slope to be evaluated with the on-site deformation damage signs, so as to estimate the deformation damage stage of the slope at present and predict the deformation damage phenomenon which is possibly generated in the next step.

Further, in step S1, the basic features of the slope include topography, stratigraphic lithology, geological structure, hydrogeological conditions and unfavorable geological phenomena.

Further, engineering geological analysis is carried out on a slope deformation failure mechanism according to the basic characteristics of the slope, deformation failure signs are found out, the failure mechanism and crack formation reasons are analyzed, rainwater flows into and seeps down along the formed cracks, the inner-layer geological mechanism is softened, further seeps down until the cracks are communicated, and the process of communicating the cracks is divided in stages.

Further, the physical mechanical strength test in the step S1 includes a natural water content test, a natural state direct shear test, a plastic/liquid limit test, and a direct shear test with different water contents.

Further, the physical mechanical parameters measured in the physical mechanical strength test in step S1 include natural moisture content, shear strength parameter: the relationship between the internal friction angle, the cohesive force, the plastic/liquid limit and the shear strength and the vertical pressure.

Further, the rainfall physical simulation in step S2 specifically includes:

and (3) reducing the collected slip soil in proportion to serve as a slope model to be evaluated, simulating rainfall within a certain time by using a water spraying device, and designing the specific rainfall time and rainfall according to the model scaling and the actual situation on site.

The beneficial technical effects of the invention are as follows: the way of rainwater entering the interior of the infiltration slope body is researched, and the rainwater is presumed to flow into the infiltration along the cracks to gradually soften the cracks and promote the cracks to develop. And rainwater can be simulated to flow into the infiltration along the crack by assigning values to the seepage path in sections, so that the crack is gradually softened to promote the process of penetration. The calculation result is more accurate and accords with the reality, and the defects that the traditional integral strength reduction method has large calculation error, is difficult to quantitatively evaluate and predict the slope deformation trend can be overcome.

Drawings

FIG. 1 is a flow chart illustrating steps of an embodiment of the present invention.

Fig. 2 is a schematic flow chart of the overall implementation of the technical solution of the embodiment of the present invention.

FIG. 3 is a schematic diagram of a avalanche integrated particle curve according to an embodiment of the present invention.

FIG. 4 is a schematic view showing the particle profile of the fill in the embodiment of the present invention.

FIG. 5 is a graph showing the tau-p relationship of a soil sample in a natural state according to an embodiment of the present invention.

FIG. 6 is a graph showing the τ -p relationship of a soil sample with a water content of 23% according to an example of the present invention.

FIG. 7 is a graph showing the τ -p relationship of a soil sample with a water content of 27% according to an example of the present invention.

FIG. 8 is a graph showing the τ -p relationship of a soil sample with a water content of 31% according to an example of the present invention.

FIG. 9 is a graph showing the τ -p relationship of a soil sample with a water content of 35% according to an example of the present invention.

FIG. 10 is a graph showing the variation of the c-value with the increase of the water content according to the embodiment of the present invention.

FIG. 11 shows an embodiment of the present invention

The values are shown as a graph of water cut.

Fig. 12 is a schematic diagram illustrating landslide model building according to an embodiment of the present invention.

Fig. 13 is a schematic diagram illustrating the overall effect of the landslide model building according to the embodiment of the invention.

FIG. 14 is a schematic diagram of a landslide model building grid according to an embodiment of the invention.

FIG. 15 is a schematic diagram illustrating the slip surface forming stage division according to an embodiment of the present invention.

Fig. 16 shows a natural state vertical displacement cloud of an embodiment of the present invention.

FIG. 17 shows a natural state maximum shear strain increment cloud for an embodiment of the invention.

FIG. 18 shows a natural state horizontal displacement cloud in accordance with an embodiment of the present invention.

Fig. 19 is a schematic view of the natural state slope safety factor according to an embodiment of the present invention.

FIG. 20 shows a cloud of maximum shear strain increase at the rain infiltration-trailing edge crack formation stage for an embodiment of the present invention.

FIG. 21 shows a vertical displacement cloud for the rainfall infiltration-trailing edge crack formation phase of an embodiment of the present invention.

FIG. 22 shows a horizontal displacement cloud for the rainfall infiltration-trailing edge crack formation stage of an embodiment of the present invention.

FIG. 23 is a schematic illustration of slope safety factor at the stage of rainfall infiltration-trailing edge crack formation in accordance with an embodiment of the present invention.

FIG. 24 shows a cloud of rain water flowing down a fracture into the infiltration-fracture growth stage maximum shear strain increase for an embodiment of the invention.

FIG. 25 shows a vertical displacement cloud of rain water flowing into a infiltration-fracture growth stage along a fracture in accordance with an embodiment of the present invention.

FIG. 26 shows a horizontal displacement cloud of rain water flowing into the infiltration-fracture growth stage along the fracture for an embodiment of the present invention.

FIG. 27 is a schematic illustration of the slope safety factor of rainwater flowing into the infiltration-crack development stage along the crack according to an embodiment of the present invention.

FIG. 28 is a cloud of maximum shear strain increments during the slip plane through-bulk slip phase for an embodiment of the present invention.

FIG. 29 shows a sliding surface through-bulk sliding phase vertical displacement cloud for an embodiment of the invention.

FIG. 30 is a horizontal displacement cloud illustrating a sliding surface through-bulk sliding phase according to an embodiment of the present invention.

Fig. 31 is a schematic diagram of slope safety factor in the sliding surface through-integral sliding stage according to the embodiment of the present invention.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to fig. 1 to 31 of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

Example (b):

as shown in fig. 1, the method for dynamically evaluating the stability of a slope based on the change of the rainfall seepage path and the water content comprises the following steps:

Further, the rainfall physical simulation in step S2 specifically includes:

According to the scheme, the way of rainwater entering the interior of the seepage slope body is researched, and the rainwater is presumed to flow into the seepage along the cracks and gradually soften the cracks to promote the cracks to develop. And rainwater can be simulated to flow into the infiltration along the crack by assigning values to the seepage path in sections, so that the crack is gradually softened to promote the process of penetration. The calculation result is more accurate and accords with the reality, and the defects that the traditional integral strength reduction method has large calculation error, is difficult to quantitatively evaluate and predict the slope deformation trend can be overcome.

The phenomenon of instability of the roadbed is prominent when the expressway is built in a mountain area. For example, a highway toll station is planned at a certain section K29+800-K30+200 of a highway, the original slope is filled, and a retaining wall is used for supporting. 7 months in 2014, landslide is generated after roadbed backfilling under the influence of continuous strong rainfall, the total volume is about 50 ten thousand, and supplementary and support measures and toll stations are causedAnd (6) re-addressing. The landslide is a process of stability → deformation → gradual progress of destruction, and is not a complete conclusion. The traditional method for reducing the overall strength is used for researching the slope stability or the catastrophe process, the error is large, the process is difficult to simulate, the calculation is limited before deformation and after instability, and the calculation result is difficult to be used for quantitative evaluation or subsequent deformation prediction. The field is developed and investigated, the slippery soil with different water contents is collected and subjected to direct shear test, and the physical and mechanical parameters of the slippery soil with different water contents are measured. Then carrying out engineering geological analysis on the deformation failure mechanism of the landslide, wherein the important factor is fill loading, the induction factor is continuous rainfall, the landslide is judged to be formed by cracks formed at the rear edge and developed and communicated to the front edge to form the landslide, and the process is divided into three stages: rainfall infiltration, the crack is formed on the rear edge → rainwater flows into the infiltration along the crack, the crack is expanded, the middle part is communicated → the sliding surface is communicated, and the whole body slides. And (3) carrying out rainfall physical simulation on the landslide, monitoring the occurrence time of pore water pressure peak values of all measuring points on the sliding surface, and verifying the result of engineering geological analysis. Using FLAC^3DEstablishing a landslide model, independently modeling a sliding surface, carrying out staged division on the development of the sliding surface, and carrying out sectional assignment on the sliding surface at different stages.

As shown in fig. 2, under the main scheme of the slope stability dynamic evaluation method based on the rainfall seepage path and the change of the water content, the specific implementation includes the following contents for the above case:

(1) and (4) carrying out on-site investigation on the landslide body, collecting fresh tyre soil, carrying out a direct shear test and measuring the natural water content. Measuring the glide soil c in the natural state,

The value is obtained.

(2) Measuring plastic liquid limit of the zonate soil, setting different water content zones with gradient in the range from the plastic liquid limit to the liquid limit for direct shear test, measuring the water content zones of the zonate soil c,

The value is obtained.

(3) And (4) carrying out a permeability test on the slippery soil, and measuring the permeability coefficient K of the slippery soil.

(4) And determining the development stage of the sliding surface of the landslide by combining the change conditions of the pore water pressure at different positions with time monitored by physical simulation.

(5) Using FLAC^3DAnd establishing a landslide body model, and setting parameters according to indoor test and reconnaissance data.

(6) Using FLAC^3DAnd calculating the landslide point stability coefficient under different working conditions.

(7) Combining test data, using FLAC^3DAnd carrying out dynamic simulation and dynamic analysis on different stages of sliding surface development under the rainstorm working condition.

(8) Using FLAC^3DAnd (4) arranging anti-slide piles at different stages of the development of the sliding surface, and dynamically controlling the sliding mass.

(9) And calculating the most reasonable fortification condition and giving engineering suggestions.

Slope morphology characteristics of this case:

the side slope is a weathered and sloping gravity landform of a typical middle mountain area and comprises near-horizontal bedrock, an overlying landslide body and a filler. Under the action of peripheral faults, the bedrock is extruded to be crushed, and due to the property that the shale is easy to weathere, mountain bodies with steep trailing edges collapse and are stacked in the middle of a slope platform to form a collapse volume, the transverse width of the collapse volume is approximately 600 meters, and the longitudinal length of the collapse volume is approximately 330-520 meters; the slope has a volume average thickness of about 28 meters and a volume of about 6.5 ten thousand cubic meters. The slope of the top of the side slope is steeper, about 60 degrees; the middle-upper part is relatively gentle, averaging about 15 °; the front edge slope foot terrain is slightly steeper than the middle part, and the slope is 20-35 degrees. According to the survey data, the gradient of the base boundary line varies greatly, within 0-38 deg. Fill height 920-.

The elevation of the leading edge is around 890 meters and the elevation of the trailing edge is about 940 meters. The longitudinal extension of the side slope is basically consistent with the slope of the ground, and the inclination is 198 degrees; the height of the landslide ground is 850.85-1006.52 m, the relative height difference is 155.67m, and the main sliding direction is 170 degrees. The left side and the right side of the slope are developed with gullies for perennial running water, so that the two sides of the slope form a face with exposed bedrock. The front edge of the slope forms an obvious inverted triangle under the cutting action of the gully.

The slope rock-soil body composition and the structural characteristics of the case are as follows:

the first step is that the bed rock is rock shale belonging to the phylum of the Shandong-system Lormaxi group (S1l), which is black and grey black, and the shape is 252 degrees ∠ 4 degrees, according to the drilling and exploration data, especially the existing excavation of the anti-slide pile construction, the surface of the bed rock is strongly weathered and is mud-shaped, the strongly weathered shale mainly comprises viscous minerals, is of a mud structure and a thin-layer structure, and can be crushed by hand pinching in the extreme intensity area, and the bed rock is in an arc curve in the longitudinal direction and basically consistent with the surface relief.

Second, collapse and build up layer: the hillside soil is mainly composed of gravels and covered with viscous ploughing and planting soil. And obtaining relevant parameters of the collapse slope layer through field sampling and field tests, and performing an indoor water content test, a particle test, a shear test and a penetration test. The collapse slope layer density measured by field test is: 1.93g/cm3, and the water content test showed that the water content in the disintegrated volume was 20.81%. The results of the particle tests are shown in table 1 below and fig. 3.

TABLE 1 statistical table of particle size data of collapse slope

As can be seen from the data in the particle curves of the collapse masses shown in Table 1 and FIG. 3, the collapse masses mainly comprise 2-20mm of broken stones, the proportion of the broken stones is 63%, the broken stones larger than 20mm only occupy nearly 13%, the rest small particles occupy 24%, and the broken stones are mainly soil particles. In addition, a shear test is carried out on the collapse layer soil sample, the shear test result is shown in the following table 2, and the permeability coefficient is 0.05 cm/s.

TABLE 2 collapse volume soil shear strength parameters

Thirdly, artificial filling: the artificial filling on the side slope is positioned at the high-speed embankment section of the south road, has the elevation of 913 + 915 meters, mainly comprises blocky gravel soil, and is khaki, grayish yellow sandstone, siltstone and grayish black shale. The rock-soil ratio of the filling body is 7:3, the construction rolling control data is that the compactness reaches 93 percent, the slope ratio is 1:1.5, and the thickness of the whole filling body is 1-12 meters. The density was 2.02g/cm3, obtained by field sampling and field testing. The results of the laboratory test particles are shown in table 3 below and fig. 4. The filling is mainly composed of block gravels with the particle diameter larger than 10mm, and the proportion of the block gravels is more than 70%.

Table 3 filler particle test data

Particle diameter Range (mm)	Percentage of the component (%)
		d>60	23
60>d>40	21
		40>d>20	21
20>d>10	10
		10>d>5	7
5>d>2	8
		2>d>1	4
1>d>0.5	2
		0.5>d	4

The slope hydrogeological conditions of this case:

both the fill and the landslide deposit are mainly composed of rubble and constitute a good aquifer, while the strongly weathered shale under the landslide deposit is a relatively water-barrier. Therefore, the water in the slope body is mainly pore water and is enriched in the collapse slope volume body

In addition, it is supplemented by atmospheric precipitation, and has the characteristics of supplementing and discharging immediately. The land surface of the collapse volume section is relatively flat, the average slope is about 12 degrees, so most rainfall can permeate into the collapse volume body, finally converges at the base boundary line and is discharged to the lower side of the slope, and the cut outlet at the front edge of the landslide is obviously visible.

The water seepage amount of the front edge of the landslide from the slope body to the outside is about 1.86ml/min according to the measurement of using a simple plastic bottle on site. Crab activity can be seen in the shearing outlet, the water quantity in the shearing outlet is sufficient, water can be continuously supplied, and the water quality is good and pollution-free.

In addition, there are 3 spring points at the front edge of the collapse volume, S01 (water amount of 0.3L/S), S02 (water amount of 0.9L/S), and S03 (water amount of 0.3L/S).

Therefore, the collapse volume has abundant underground water which is mainly distributed near the lower part of the collapse volume and the base boundary line, which is very unfavorable for the overall stability of the side slope.

Deformation failure characteristics of the slope of this case:

first, overall deformation failure characteristics:

the side slope slides when the right side embankment of the T J5 work area K29+ 880-K30 +200 section of the 28-sun road in 10 and 28 months 2014 is backfilled to the first filling body platform, so that a sliding slope body is formed. The longitudinal length of the landslide body is about 150 meters, the transverse width of the rear edge is about 250 meters, the transverse width of the front edge is about 65 meters, the average thickness is about 13 meters, and the total volume is about 50 ten thousand square. The penetrating crack of the rear edge is 151 m long, the lower dislocation is 0.7 m, the crack width is about 0.01-0.3 m, and the crack is arc-shaped. The front edge is cut out, and a plurality of cracks are arranged on the sliding body.

Second, trailing edge deformation failure characteristics:

obvious cracks can be seen at the position close to the rear edge on the landslide body, the main landslide direction of the landslide is 170 degrees, and the statistical data of the main cracks are shown in the following table 4. In addition, the farmland close to the true side of the road can obviously subside along the sliding direction, the subsidence distance is close to 30cm, the farmland generates tensile crack towards the outer side, and the width of the crack is about 17 cm.

TABLE 4 statistical table of trailing edge cracks of landslide (main cracks)

Crack numbering	Trend (°)	Opening width (cm)	Crack depth (cm)	Extended length (m)
					SL04	245	10-20	10-40	12.5
SL06	275	10-35	55	5.8
					SL07	230	5-15	35	3
SL08	270	5-10	20	11.8
					SL09	160	5-50	5	4.3
SL10	250	10-30	40	3.8
					SL11	265	5-20	5-15	4.4
L04	264	5-15	10	6
					L05	260	10	20	3
L06	260	5-15	20	4.9
					L08	278	10-20	35	2.9
L10	279	40	40	11
					L11	270	5-15	20	3.1
L12	290	15	35	2.5
					L13	275	10	35	15.5
L14	282	3-10	50	1
					L15	272	10	10-30	3.8
L17	268	8	10	8
					L18	274	10-25	30	10
L19	290	10	20	17
					L20	295	10	35	8

Third, leading edge deformation characteristics:

although the front edge of the landslide is more than one and a half years away from the landslide, the damage phenomenon is still very obvious, most notably, the front edge is cut out, and the surface of the landslide is damaged. In addition, the seepage of groundwater from the position of the front edge shear outlet is also a more obvious phenomenon. These phenomena are also important signs for determining the landslide front edge in the field. The damage length of the front edge of the landslide is 65 meters along the transverse direction of the landslide, and a steep ridge which is nearly 5 meters is formed integrally.

Fourthly, deformation characteristics of the retaining wall:

at the beginning of filling, the retaining wall is built at the front edge of the filling body, which is intended to ensure the safety of the filling body, but the retaining wall is deformed and damaged as the filling continues until the slope is unstable. Mainly embodied in that the middle part of the retaining wall protrudes out of the slope, and the protruding distance reaches 2-9 cm. The wall body on the right side (along the true direction) has tensile cracks, the width of the cracks is about 1-2cm, and water seepage exists locally.

Based on the basic characteristics, the physical mechanical test is carried out:

first, testing the water content of the soil in the natural state:

the ratio of the mass of water lost when the soil is dried in an oven at the temperature of 105-110 ℃ until the mass is unchanged to the mass of dried soil after drying is called the water content of the soil and is expressed by percentage. The water content of the soil is an important physical property index of the soil, the water content can reflect the dry and wet states of the soil, and the physical and mechanical properties of the soil can be changed in a series due to the change of the water content. The water content of the soil is the most active and uncertain factor in solid, liquid and gas three-phase substances of the soil, and is also one of important factors influencing the state of the soil and the engineering geological properties. The change of the water content can affect a series of physical and mechanical properties of the soil, such as the consistency, the saturation, the structural strength and the like of the soil. Therefore, research on the water content of soil is an indispensable index in research on the physical and mechanical properties of soil, and the water content of soil is measured to detect the water-containing state of soil and to study the influence of the water-containing state of soil on engineering construction.

In the experiment, the field-collected slippery soil is used as a test soil sample, the natural water content of the slippery soil is measured, and a theoretical basis is provided for the numerical simulation assignment.

1. Test instrument equipment

(1) Electric oven: the temperature was controlled at 105 ℃ and 110 ℃.

(2) Balance: weighing 200g, wherein the minimum division value is 0.01 g; 1000g are weighed out, the minimum index value being 0.1 g.

2. Procedure for the preparation of the

(1) Taking 15-30g of representative slippery soil, removing broken stones with the diameter larger than 5mm in the soil sample, respectively placing the processed soil sample into weighing boxes with different numbers, weighing the mass of the boxes with different numbers, recording the number of the boxes, weighing the box, and humidifying the soil mass to be accurate to 0.01 g.

(2) And (3) placing the weighing box filled with the soil sample in an oven, and drying for 24 hours at the constant temperature of 105-110 ℃.

(3) And taking the weighing box out of the oven, putting the weighing box into a drying container, cooling to room temperature, weighing the weighing box, adding dry soil, and accurately weighing to 0.01 g.

3. Results of the experiment

(1) The water content of the sample is calculated according to the formula (4-1) and is accurate to 0.1 percent

W 0-moisture content (%) of the sample;

m 0-Wet soil mass (g);

md-dry soil mass (g).

(2) The moisture content test record is shown in Table 5. The obtained topsoil has natural water content of 22.6%

TABLE 5 test record of water content of natural state tyre soil

Second, the direct shear test of the natural state sliding zone soil:

the shear resistance of soil refers to the performance of soil body for resisting shear force and maintaining the property of the soil body without damage, the maximum value of the shear stress which can be resisted by the soil is called the shear strength of the soil, and the numerical value is equal to the maximum shear stress which can be borne by the soil body.

There are many methods for determining the shear strength of soil, this timeOne of the direct shear tests used in the test is the direct shear test. The test adopts four samples, different normal phase pressures p are respectively applied to different samples, shearing force is applied to the samples for shearing, the maximum shearing stress tau during damage is measured in the test, and the shearing strength parameter of the unearthed soil can be calculated according to the tau-p curve: internal friction angle

And cohesion (c).

1. Test instrument equipment

(1) Strain control type direct shear apparatus: the device consists of vertical pressurizing equipment, a shearing box, a shearing transmission device, a dynamometer and a displacement measuring system.

(2) Cutting a ring: an inner diameter of 61.8mm and a height of 20 mm.

2. Procedure for the preparation of the

(1) And (3) preparing a soil sample, screening large gravels which cannot be tested from the natural slip-band soil collected in the field in the test, and preparing 4 groups of soil samples containing fragments by using a cutting ring for testing.

(2) Putting a hard plastic film at the bottom of the shearing box, aligning the cutting edge of the circular cutter upwards to the opening of the shearing box, putting a hard plastic film and a water permeable plate on the sample, pressing the water permeable plate to carefully push the sample into the shearing box, and covering a cover of the shearing box.

(3) Four levels of vertical loads are applied to each set of test respectively, the vertical maximum load is designed to be 200kpa according to the average thickness of 13m, the natural filling body weight is 2150kg/m3 and the natural covering layer weight is 2050kg/m3 of the filling body landslide of the highway on the south road, and the four levels of loads are respectively 50kpa, 100kpa, 150kpa and 200 kpa.

(4) Releasing the vertical pressure, pulling out the fixed pin, and starting shearing at the shearing speed of 0.8mm/min under the control of a machine operation panel start key to shear the sample within 3-5 min. The data is recorded by a computer in the whole process, and the machine is stopped when the shearing displacement is 6 mm.

(5) And after shearing, sucking accumulated water in the box, removing the shearing force and the vertical pressure, moving the pressurizing frame, taking out the sample, and finishing the instrument.

3. Results of the experiment

(1) And (4) making a scatter diagram from the obtained data, and drawing a scatter trend curve, namely a relation curve of the shear strength and the vertical pressure.

(2) According to the relation curve of the shearing strength and the vertical pressure, the inclination angle of a straight line is an internal friction angle, and the intercept of the straight line on a vertical coordinate is cohesive force. The functional relationship is shown in formula (4-2).

(3) The direct shear test is reported in Table 6, and the shear strength versus vertical pressure curve is shown in FIG. 5. The natural state c is measured to be 15.2kpa,

TABLE 6 direct shear record of natural state of the slip band soil

Thirdly, the test of the plastic limit and the liquid limit of the slip zone soil is as follows:

the plastic limit and liquid limit measurement test is carried out based on the characteristic of linear relation between the cone penetration depth of the cone apparatus and the corresponding water content on a double logarithmic coordinate. Measuring the soil penetration depth of the cone at different water contents by using a plastic and liquid limit combined tester with the cone mass of 76g, drawing a relation straight line graph, checking the water content corresponding to the cone sinking depth of 10mm (or 17mm) on the graph as the liquid limit, and checking the water content corresponding to the cone sinking depth of 2mm as the plastic limit.

1. Test instrument equipment

(1) Plastic and liquid limit combined measuring instrument: comprises a cone gauge with a scale, an electromagnet, a display screen, a control switch and a sample cup. Cone mass 76g, cone angle 30 °; the reading display adopts a photoelectric type, a vernier type and a percentage type; the inner diameter of the sample cup is 40mm, and the height of the sample cup is 30 mm.

(2) Balance: weigh 200g, minimum division value 0.01 g.

2. Procedure for the preparation of the

(1) Taking a natural slip-band soil sample, drying and mashing the natural slip-band soil sample, and sieving soil particles and impurities larger than 0.5mm by using a 0.5mm sieve to obtain a representative soil sample 200g below the sieve. Placing the sample on a rubber plate, mixing the soil sample into a uniform paste with pure water, placing the paste into a soil mixing vessel, and soaking the soil sample day and night.

(2) And fully and uniformly stirring the prepared sample, filling the sample into a sample cup, fully kneading the relatively dry sample without leaving a gap during sample filling, compactly filling the sample into the sample cup, and scraping the surface after filling.

(3) The sample cup is placed on a lifting seat of the combined measuring instrument, a thin layer of vaseline is smeared on the cone, and the cone is attracted by the electromagnet when the power supply is switched on.

(4) Adjusting zero point, adjusting a scale on a screen to zero point, adjusting a lifting seat to enable a cone tip to contact the surface of a sample, sinking the cone into the sample under the dead weight when an indicator lamp is on, measuring and reading the sinking depth of the cone (displayed on the screen) after 5s, taking out a sample cup, digging out vaseline at the position where the cone tip is buried, taking out not less than 10g of sample near the cone, putting the sample into a weighing box, and measuring the water content.

(5) And adding water into all the samples or blow-drying and uniformly mixing, and repeating the steps of 2-4 to respectively measure the cone sinking depth and the corresponding water content of the samples at the second point and the third point.

3. Results of the experiment

(1) The water content of the sample was calculated as in the formula (4-1) to the nearest 0.1%.

(2) The test records of the plastic and liquid limit combined determination method are shown in Table 7. The plastic limit of the slip band soil was found to be 22.5% and the liquid limit was found to be 35.7%.

TABLE 7 test records of plastic and liquid limit combined determination method

Fourth, direct shear test of the slippery soil with different water contents:

1. purpose and procedure of the test

The test is carried out by controlling the water content of the slippery soil on the basis of the prior natural slippery soil direct shear test, and aims to obtain c, c and c of slippery soil with different water contents,

A relation curve is obtained, and c,

The value is obtained. The specific scheme is as follows:

(1) a strain control type direct shear apparatus is adopted to perform a direct shear test, the apparatus tests the tool changing diameter is 61.8mm, the height is 20mm, and the allowable grain size of a sample grain is 1/6 with the height of a cutting ring. Therefore, the screened sand particle group and the fine particle group (the particle size is less than 2mm) are taken for testing.

(2) The soil sample is blended into samples with different water contents, and the water contents of the samples refer to plastic and liquid limits, and the water contents are increased to be near the liquid limits every 4 percent. The plastic limit of the obtained slide belt soil is 22.5 percent and the liquid limit is 35.7 percent. Therefore, the water content is respectively designed as follows: 23%, 27%, 31%, 35% for 4 groups of tests.

(4) In order to control the test accuracy, the quality of the same group of samples is the same, the quality of different groups of samples is controlled within 4%, the samples in the same group are tightly covered by a preservative film after being prepared, the samples are placed for 24 hours and then are configured according to the target moisture content of the test design, and the measured moisture content is 23.1%, 27.3%, 31.8% and 35.7% respectively and is basically stable with the designed moisture content.

2. Results of the experiment

(1) And (4) making a scatter diagram from the obtained 4 groups of water content data, and drawing a scatter trend curve, namely a relation curve of the shear strength and the vertical pressure.

(3) The water content of the soil sample is measured and shown in table 8, the direct shear test records with different water contents are shown in tables 9 to 12, and the relation curve of the shear strength and the vertical pressure is shown in fig. 6 to 9. Because large particles larger than 2mm are removed and more gravels are in the slippery soil, the obtained c,

The value needs to be multiplied by an empirical factor. The experimental c value is 1.3,

the empirical coefficient of value is 1.2. c.

The results of the value calculations are shown in table 13.

TABLE 8 determination of moisture content of soil sample

Direct shear test record of table 923% water content

TABLE 1027% moisture content direct shear test record

Table 1131% moisture content direct shear test record

Direct shear test record of table 1235% moisture content

TABLE 13 different water contents c,

Value calculation result

According to the test results of the slippery soil with different water contents, under the condition of the same water content, the measured shear strength tau value is correspondingly increased along with the increase of the vertical pressure p value, and the corresponding function curve is approximately in a straight line. Under the condition that the vertical pressure p is not changed, the shear strength tau value of the slipband soil is reduced along with the increase of the water content. The water content of the slippery soil is increased, the physical and mechanical properties are reduced, and the measured c,

The value is correspondingly reduced, the soil is carried by the sliding belt c,

The change of the value with the increase of the water content is shown in FIGS. 10 to 11. C, c and c of the slippery soil with different water contents measured by tests,

The value can show the physical and mechanical strength of the zonal soil under different water-containing conditions, and simultaneously shows the strength change of the zonal soil along with the increase of the water content. The physical and mechanical strength conditions of the slipband soil under different water-containing conditions along with the rainfall are simulated, and a basis is provided for parameter selection during the dynamic simulation of the stability of the filling roadbed slope.

Establishing a slope stability dynamic analysis model based on rainfall seepage paths and water content changes:

this FLAC^3DThe numerical simulation adopts the original design test simulation to calculate, and the numerical simulation is divided from top to bottomAnd 3 layers of artificial filling, collapse layer and bedrock (shale). And determining the position of the known sliding surface according to the landslide survey data.

This FLAC^3DThe simulation adopts a false three-dimensional model, wherein the establishment of the profile is crucial, and the model profile is related to whether the simulation of the prototype is real or not and the value of the test. Based on field investigation and indoor data analysis, the area I in the two subareas of the landslide is a main landslide area, so that the area I of the landslide is selected as a research area for numerical simulation, a section with a representative shape from a filled highway to a toe is selected as the section, and the section is almost the same as the actual situation, namely the research section is about 275 meters long and the height difference is 92 meters. According to the actual situation, the model establishment is considered as follows:

(1) the model building divides the landslide into 7 modules, including 7 modules in 3 stages and sections of artificial filling, a covering layer, bedrock (shale), a retaining wall and a slip surface.

(2) The sliding surface is modeled in three sections, the sectional position is based on the monitoring condition of the pore water pressure at different positions in physical simulation, and the value is assigned based on the detection value of the pore water at different time.

(3) In the model, only the finally communicated crack which has the largest influence on the stability of the side slope is modeled, and the other cracks with smaller influence are not modeled.

(4) Combining the properties of the roadbed slope to be filled, the constitutive model adopts FLAC^3DBuilt-in Moore-Coulomb model.

(5) In order to simulate the actual situation more accurately, the limited displacement boundary condition is adopted for 4 surfaces of the model, and the free boundary condition is adopted for two adjacent empty surfaces.

(6) For convenience of calculation, the gravity was set to 10 KN/m. In order to more accurately simulate the actual deformation damage process, the respective deformation damage stage calculation steps are set to 5000 steps in addition to the natural state.

The specific modeling cases are as shown in fig. 12 to 14. The slip surface staging determined from pore water pressure monitoring is shown in figure 15.

In the parameter selection of model calculation, six parameters of volume modulus, shear modulus, cohesive force, internal friction angle, tensile strength and gravity are mainly considered, the saturated water content, saturated permeability coefficient and residual water content of rock and soil mass are also considered, and the hydraulic parameter selection condition is shown in table 14. The parameter selection basis is mainly obtained by indoor experiments, and is determined by combining part of experience values, and 3 stages of natural state and landslide formation and development are respectively assigned and calculated.

Table 14 table for taking values of hydraulic parameters of each seepage medium

Dynamic analysis of stability of different stages of deformation damage of the filling roadbed slope:

1. natural state of the body

In a natural state, due to the gravity action of a filling body, all parts of a filled roadbed slope can generate settlement in a long time, and all parameters can change correspondingly, but in the practical situation, continuous rainstorm occurs soon after artificial filling and slope sliding occurs, consolidation settlement is not completed, so the parameters of artificial filling, covering layers and bedrocks before the slope sliding occurs are equivalent to the parameters obtained in an exploration sampling test after the slope sliding occurs. The natural state numerical simulation analysis values of the parameters of the modules are shown in table 15.

TABLE 15 Natural State parameter selection

The following results are obtained according to the calculated graph by carrying out numerical simulation analysis by using the set parameters:

(1) according to the maximum shear strain increment cloud chart, the filling roadbed side slope in a natural state can generate weak shear strain under the influence of slope type influence and the physical and mechanical properties of a filling body, namely the rear edge position of a landslide, in the natural state, the weak property of the filling body can be verified, and a foundation is laid for forming cracks and developing and communicating under the rainfall condition. As shown in fig. 16.

(2) Known by the vertical direction displacement cloud picture, under natural state, because the heap of artifical banket effect, the hole in the banket can be compressed, can produce certain settlement displacement in vertical direction, and the overburden is because the consolidation is incomplete, also can produce a small amount of subsides, and the basement rock is because long-term consolidation subsides, does not basically take place to subside, but under retaining wall body gravity effect, can produce trace settlement consolidation through the lengthy time in the retaining wall below, subside mainly concentrate on artifical banket. However, as the construction of the filling body is completed shortly, the side slope encounters continuous strong rainfall and forms a landslide, and consolidation settlement is not completed yet. As shown in fig. 17.

(3) According to the horizontal displacement cloud picture, the influence of settlement is eliminated, a small amount of displacement is generated in the horizontal direction under the natural state, the displacement is mainly concentrated in the middle of the filling body and near the retaining wall, and the weak characteristic at the rear edge of the landslide is verified. As shown in fig. 18.

(4) The slope safety coefficient graph shows that the slope safety coefficient in a natural state is 1.38, and FLAC^3DThe conservative value of the safety coefficient in the method is between an arc method and a strip division method, and is a relatively conservative calculation result, and the calculated slope is relatively stable in a natural state. As shown in fig. 19.

According to the calculation result, the main displacement and strain of the slope in a natural state are concentrated in the middle of the filling body, namely the rear edge position of the landslide, the weak characteristic of the soil body at the position is verified, and a foundation is laid for the crack formation at the position in the rainfall process and the crack development and penetration caused by the inflow of rainwater along the crack.

2. Rainfall infiltration-trailing edge crack formation stage (first stage)

Since the filling body in a natural state encounters continuous strong rainfall and forms a landslide shortly after the construction is completed, displacement and strain formed by numerical simulation of the natural state need to be removed. After the displacement and strain are cleared, the modules are reassigned using the preset parameters, the assignment of which is shown in table 16.

TABLE 16 rainfall infiltration-trailing edge crack formation stage parameter selection

And (3) reassigning the slope by using preset parameters to calculate 5000 steps, simulating the process of the first stage of landslide development damage, and obtaining the following results according to a calculation chart:

(1) the maximum shear strain of the first stage is mainly concentrated in the middle of the filler, namely the position of the rear edge of the landslide, in addition, the landslide surface initially shows a contour, and each position of the landslide surface has a small amount of shear strain, so that the position of the landslide surface obtained by investigation is further verified. As shown in fig. 20.

(2) In the first stage of landslide damage deformation, the filling body has about 1-2cm of settlement at each position due to large pores among particles, and the settlement is most prominent at the rear edge position of the landslide, so that the shearing displacement of about 1cm is formed. As shown in fig. 21.

(3) In the first stage of deformation and damage of the landslide, 1.3cm of horizontal displacement is formed at the position of the rear edge of the landslide, namely, a crack of about 1cm is formed at the rear edge, and rainwater can flow in along the crack, so that a foundation is laid for the subsequent development of the landslide. As shown in fig. 22.

(4) The safety coefficient of slope deformation damage in the first stage is 1.23, the slope is safe, but creep can be formed under the action of rainfall. As shown in fig. 23.

Under the action of rainfall, the strength of artificial filling is reduced, a crack is generated in the middle of the filling body, namely the rear edge of a landslide under the action of downward sliding force, rainwater flows into the crack along with the continuous progress of heavy rain, and the strength of soil at the crack is reduced violently. At this stage, a fine crack was observed at the trailing edge.

3. Rainwater flows into the infiltration-crack development stage (second stage)

On the basis of displacement and strain formed by assignment calculation in the first stage, preset parameters are used for reassigning and calculating all modules of the slope, and the assignment of the parameters is shown in a table 17.

TABLE 17 rainwater infiltration along crack-crack development stage parameter selection

And (3) carrying out reassignment calculation on each module of the slope by using preset parameters on the basis of the existing deformation for 5000 steps, simulating the second stage of landslide deformation damage, and obtaining the following results according to calculation:

(1) the maximum shear strain in the second stage is mainly concentrated near the basal-covering interface under the crack, and the landslide surface develops approximately along the basal-covering interface. As shown in fig. 24.

(2) The trailing edge produced a shear displacement of about 30cm in the vertical direction during the second stage of landslide deformation failure. Corresponding to the phenomenon of farmland fault seen in site survey, a section with obvious filling bodies can be seen at the rear edge. As shown in fig. 25.

(3) The landslide deformation damages the basal covering interface under the second stage crack to generate displacement of about 30cm, the position of the rear edge generates crack of about 10cm, the position of the front edge of the landslide generates upward extrusion effect, and slight uplift can be seen. The twisting cracking of the retaining wall about 3cm occurs, which is consistent with the cracking phenomenon of the retaining wall observed in site investigation. As shown in fig. 26.

(4) According to the slope safety coefficient diagram, the slope safety coefficient in the second stage of landslide deformation damage is calculated to be 1.12, the slope stability is poor, a relatively stable point can be kept before a landslide sliding surface is communicated, deformation is still in a creeping stage, the slope safety coefficient in the stage cannot meet the design requirement, and if the life and property safety of residents is guaranteed, a project can be guaranteed to run smoothly, control measures must be taken in the stage. As shown in fig. 27.

Under the continuous action of rainfall, due to the generation of the crack at the rear edge of the landslide, rainwater flows in from the crack at the rear edge and seeps to the base-cover interface from the crack, so that the intensity of soil at the base-cover interface is sharply reduced, and the rainwater is accumulated at the base-cover interface below the crack and downwards seeps along the underlying shale layer. And because the strength of the rear edge is reduced, the soil body begins to slide downwards, stress is accumulated on the front edge, extrusion deformation is generated, and the maximum shear strain is generated at the position of a basal covering interface under the crack. In the stage, the farmland at the rear edge is staggered, the slope body at the front edge is raised, and the retaining wall is slightly twisted and cracked. The sign of the change is very obvious at this stage, and if the project is ensured to run smoothly, the control measures are required to be taken immediately to ensure the life and property safety of residents.

4. Sliding surface through-integral sliding stage (third stage)

And on the basis of displacement and strain formed by assignment calculation in the second stage, assigning and calculating each module of the slope again by using preset parameters, wherein the assignment of the parameters is shown in a table 18.

TABLE 18 slip through-slip phase parameter selection

And (3) reassigning and calculating 5000 steps for each module of the slope by using preset parameters on the basis of the existing deformation, simulating a third stage of landslide deformation damage, and calculating the following results according to the calculation:

(1) the maximum shear strain increment of the third stage of landslide deformation damage is concentrated on the front edge of the landslide, a through sliding surface is formed at the moment, an obvious sliding surface profile can be seen from a cloud picture of the maximum shear strain increment, and the whole sliding surface generates large shear strain. As shown in fig. 28.

(2) The vertical displacement of the third stage of landslide deformation damage still mainly occurs at the rear edge of the landslide, the shearing displacement of about 35cm is generated, and the farmland dislocation is more obvious on the basis of the deformation generated at the rear edge of the second stage. As shown in fig. 29.

(3) The horizontal displacement of the third stage of landslide deformation damage mainly occurs at the front edge of the landslide, the position of the front edge of the landslide is simulated and calculated to generate horizontal displacement of about 1.2m, and the horizontal displacement is consistent with the front edge which is obtained by site survey and is cut to about 1 m. As shown in fig. 30.

(4) The slope safety coefficient is calculated to be 0.76 in the third stage of slope deformation damage, the slope is in a continuous sliding stage, the sliding surface is through in the stage, the front edge is cut out, the deformation is changed from creep to violent sliding, the lives and properties of nearby residents are threatened, the highway can not be used continuously, the project can not be run continuously, and the slope in the stage causes huge economic loss. In order to prevent the slope from being completely damaged to cause greater life and property loss, emergency measures need to be taken immediately to control the landslide from multiple aspects. As shown in fig. 31.

Under the action of continuous rainfall, the slope begins to form a crack at the rear edge, rainwater flows in from the crack and seeps from the crack to the position of the basal covering interface, the rainwater is accumulated at the basal covering interface and continuously seeps downwards along the basal covering interface due to the impermeability of the basal rock shale, the strength of soil is reduced sharply, the crack is developed into a non-through sliding surface, the rear edge of the landslide slides downwards and is accumulated and deformed at the front edge, the stability of the landslide suddenly drops due to the action of the stacking load and the continuous seepage of the rainwater to the front edge of the landslide, a through sliding surface is formed, and the landslide is cut from the front edge. In the stage, obvious staggered cracking of the farmland can be seen, the front edge slope body is cut out and water seeps out, and the retaining wall is obviously cracked and rubbed. At the moment, the landslide causes huge economic loss, and in order to avoid causing larger loss of lives and properties, emergency measures need to be taken immediately.

Therefore, the way of rainwater entering the interior of the infiltration slope body is researched, and the rainwater is presumed to flow into the infiltration along the cracks to gradually soften the cracks and promote the cracks to develop. And rainwater can be simulated to flow into the infiltration along the crack by assigning values to the seepage path in sections, so that the crack is gradually softened to promote the process of penetration. The calculation result is more accurate and accords with the reality, and the defects that the traditional integral strength reduction method has large calculation error, is difficult to quantitatively evaluate and predict the slope deformation trend can be overcome.

Furthermore, based on the scheme, dynamic control can be performed on the stability of the roadbed side slope, namely, since the landslide is used as a geological disaster, loss is avoided as much as possible, cost saving and construction period reduction are considered, prevention can be achieved, and the treatment can be achieved. The aim of controlling the landslide is to take control measures orderly and correctly according to a certain principle during control. The following principles are mainly used for landslide control:

(1) the overall principle needs to combine engineering practice, fully utilizes local materials, ensures economy, safety and durability in material selection, does not change the natural environment as much as possible in treatment, and achieves the coordination of treatment measures and the natural environment.

(2) The principle of landslide control is different from the principle of prevention and treatment, correct identification is the primary task of control, landslide deformation characteristics are recognized, and landslide deformation conditions are judged. Secondly, the treatment needs to be systematically planned when taking measures, the principle of small treatment is adhered to, and the purpose of 'treating diseases after taking medicines' is achieved at the same time. The comprehensive treatment principle is adopted for treating the complex large landslide, and the economic reasonability and feasible technology are strived; dynamic control, scientific and efficient construction, and strengthening inspection and timely maintenance after construction is finished.

(3) For the treatment of the landslide, the most important slip factor is water, drainage treatment is preferably considered, and support treatment is considered when the drainage can not meet the treatment requirement. The surface water and the underground water are blocked in the drainage treatment, and the dredging work is well done. When the support measures are taken, firm support measures are taken, landslide sliding places are refilled through the road, the damaged road surface is repaired through the road, and the life and property safety of people is guaranteed.

Claims

1. A slope stability dynamic evaluation method based on rainfall seepage paths and water content changes is characterized by comprising the following steps:

2. The method for dynamically evaluating the stability of the slope based on the seepage path and the change of the water content of the rainfall as claimed in claim 1, wherein in step S1, the basic characteristics of the slope comprise a landform, a lithology of a stratum, a geological structure, a hydrogeological condition and an unfavorable geological phenomenon.

3. The method for dynamically evaluating the stability of the slope based on the rainfall seepage path and the change of the water content according to claim 2, is characterized in that engineering geological analysis is performed on a slope deformation failure mechanism according to basic characteristics of the slope, a deformation failure sign is found out, the failure mechanism and a crack formation reason are analyzed, rainwater flows into and seeps down along a formed crack, an inner-layer geological mechanism is softened, further seeps down until the crack is communicated, and the process of communicating the crack is divided in stages.

4. The method for dynamically evaluating the stability of the slope based on the rainfall seepage path and the change of the water content as claimed in claim 1, wherein the physical mechanical strength test in the step S1 comprises a natural water content test, a natural state direct shear test, a plastic/liquid limit test and a direct shear test with different water contents.

5. The method for dynamically evaluating the stability of the slope based on the rainfall seepage path and the change of the water content according to claim 4, wherein the physical mechanical parameters measured by the physical mechanical strength test in the step S1 include the natural water content, the shear strength parameter: the relationship between the internal friction angle, the cohesive force, the plastic/liquid limit and the shear strength and the vertical pressure.

6. The method for dynamically evaluating the stability of the slope based on the change of the rainfall seepage path and the water content according to claim 5, wherein the rainfall physical simulation in the step S2 comprises the following specific steps: