CN109785584A - Method for predicting stability of composite hydrodynamic reservoir bank slope - Google Patents

Abstract

The invention relates to a method for predicting the stability of a bank slope of a composite hydrodynamic reservoir, and belongs to the technical field of slope stability evaluation and landslide disaster monitoring and early warning. The steps of the present invention are as follows: preliminary investigation of reservoir-type landslides and selection of displacement monitoring points, arrangement and installation of monitoring equipment and processing of monitoring data, determination of basic physical and mechanical property parameters of landslides and method of slicing of slope body, water level line upslope under the action of rainfall Determination of the residual sliding thrust increment of the overall body, determination of the slope infiltration line during the decline of the reservoir water level, determination of the residual sliding thrust increment of the slope body within the range of the water level fluctuation under the action of the reservoir water level, composite water loading of the reservoir type landslide and its response parameters Determination of composite hydrodynamic load-increasing displacement response ratio prediction model, composite water slope stability evaluation and monitoring and early warning, revealing the corresponding relationship between the composite hydrodynamic load-increasing displacement response ratio parameters of reservoir-type landslides and the stability of the landslide. In order to analyze and evaluate the evolution law of reservoir-type slope stability.

Description

Prediction Method of Bank Slope Stability for Compound Hydrodynamic Reservoir

technical field

The invention relates to a method for predicting the stability of a bank slope of a composite hydrodynamic reservoir, and belongs to the technical field of slope stability evaluation and landslide disaster monitoring and early warning.

Background technique

The special engineering characteristics and complex water environment conditions of major water conservancy projects determine that reservoir-type landslides have potentially huge hazards. For reservoir-type landslides, in the process of reservoir water level fluctuation, if encountering heavy rainfall, the probability of instability will increase. Therefore, the coupling effect of reservoir water and rainfall will inevitably damage the original groundwater operating environment in the reservoir area, and form a special composite water environment dynamic effect in the Three Gorges Project reservoir area, which will greatly affect and control the frequency and scale of landslide disasters in the reservoir area. The composite hydrodynamic effect of the reservoir area and its possible impact on the slope stability of the reservoir area have become the focus of attention in the field of disaster prevention and mitigation at home and abroad. Therefore, the research and establishment of the disaster early warning and prediction method for reservoir-type slopes under compound hydrodynamic conditions will have important theoretical significance and application value for the prediction, prediction and prevention of reservoir-type landslides in the Three Gorges Project reservoir area and similar compound hydrodynamic conditions.

At present, the most widely used reservoir-type landslide prediction and evaluation methods at home and abroad are the limit equilibrium method, the displacement time series prediction method and the displacement dynamics method. The limit equilibrium method assumes the landslide body as a rigid body, analyzes its mechanical equilibrium state along the sliding surface, and evaluates the stability of the slope by taking the ratio of sliding force and anti-sliding force as the safety factor K of the landslide. However, the mechanical evaluation model established by this type of method is a static model without time factor, and there are many assumptions and constraints in the modeling, which makes the prediction and evaluation results easily affected by the above factors, with strong uncertainty, and even more unpredictable. The time of occurrence of landslide; displacement time series prediction method is to use landslide displacement, displacement rate or displacement acceleration as landslide prediction parameters, and analyze its variation law to predict landslide stability and its instability time. Although this method overcomes the shortcomings of the limit equilibrium method to some extent, the parameters it evaluates are only the displacement or displacement rate and its variation law during the evolution of the landslide. The displacement prediction parameters used in the method are susceptible to the interference of external factors, resulting in multi-phase acceleration stair-like oscillation changes, and this displacement acceleration stair-like oscillation change does not necessarily represent the overall instability of the landslide, and the displacement prediction parameters of this type of method do not have Unified instability criteria, so it is impossible to accurately judge and predict the occurrence time of landslide disasters. Displacement dynamics method Most of the proposed methods are to monitor and integrate landslide rainfall (reservoir water level) and displacement or displacement rate at the same time, so as to determine the coupled integrated dynamic prediction parameters and evaluation method of landslide rainfall (reservoir water level) and displacement or displacement rate. This prediction method overcomes the limitation that the traditional displacement time series prediction method only selects the landslide displacement or displacement rate as the monitoring and evaluation parameters, and also overcomes the defect that the limit equilibrium method cannot dynamically evaluate the slope stability. However, current researches use a single hydrodynamic variable such as rainfall or reservoir water as the inducing factor to calculate the response ratio of loading and unloading. For reservoir-type landslides, the deformation and damage of the landslide are often affected by the combination of changes in reservoir water level and rainfall. For hydrodynamic effects, the dynamic loading and unloading parameters of the landslide should include the superposition of these two factors. Only considering the effect of a single hydrodynamic factor on the landslide may lead to misjudgment of the stability of the landslide. How to effectively evaluate and predict the stability of reservoir-type landslides according to the composite hydrodynamic conditions and displacement change laws remains to be further studied.

SUMMARY OF THE INVENTION

Aiming at the limitations and deficiencies of the above-mentioned traditional composite water landslide stability evaluation and prediction methods, the present invention comprehensively considers the composite hydrodynamic effects of rainfall and reservoir water fluctuations on reservoir-type landslides based on the basic principles of elastic-plastic mechanics. Based on the derivation of the residual sliding thrust increment, a model of the composite hydrodynamic loading displacement response ratio of the reservoir-type landslide was established, and the corresponding relationship between the parameters of the reservoir-type landslide composite hydrodynamic loading displacement response ratio and the landslide stability coefficient and its criterion were established. Based on this criterion, the evolution law of the stability of the reservoir-type slope is analyzed and evaluated.

The method for predicting the stability of the bank slope of a composite hydrodynamic reservoir according to the present invention includes the following steps:

Step 1: Preliminary investigation of reservoir-type landslides and selection of displacement monitoring points, including the following small steps:

(1) According to the reservoir water level adjustment plan, set n displacement monitoring points within the range from the slope contacted by the highest reservoir water level to the tensile cracks at the trailing edge, n≥3;

(2) The number of displacement monitoring reference points shall be no less than 3, which shall be selected in the stable bedrock or non-deformed area outside the monitored landslide mass, and form a displacement monitoring and control network to ensure self-checking and comprehensive monitoring of the slope monitoring points;

Step 2: Layout and installation of monitoring equipment and processing of monitoring data, including the following small steps:

(1) The layout and installation of monitoring equipment;

(2) Real-time monitoring and data processing of slope displacement and rainfall, reservoir water level;

Step 3: Determination of the basic physical and mechanical property parameters of the landslide and the method of dividing the slope;

Step 4: Determination of the overall residual sliding thrust increment of the slope above the water level under the action of rainfall, including the following small steps:

(1) Determination of the average groundwater level of the landslide due to rainfall:

The relationship between the effective rainfall and the average groundwater level change: h _t = AJ _t + B (A and B are related to the properties of rock and soil, A >0); The historical monitoring data of groundwater can be linearly fitted to comprehensively determine the rock and soil property parameters A and B of the landslide mass to be evaluated, and then the average groundwater level increment Δh _t caused by rainfall at time t can be determined according to formula (1);

Δh _t =(h _t -h _t-1 )=A(J _t -J _t-1 )=AΔJ _t (1)

(2) Determination of the residual sliding thrust increment of the i-th block under the action of rainfall:

For the bars above the reservoir water level, without considering the transfer of force between bars, the variation of the remaining sliding thrust of the i-th bar is:

Considering the force transfer between strips, the residual sliding thrust increment of the first strip under groundwater changes is:

The overall residual sliding thrust increment from the front end of the i-th block to the trailing edge of the slope is:

where:

Step 5: Determination of the slope infiltration line during the decline of the reservoir water level, including the following small steps:

According to the statistics of the actual monitoring data of a large number of reservoir landslides, it can be determined that the highest point of the seepage infiltration surface under the actual fluctuation of the reservoir water level is:

In the formula: k is the permeability coefficient of the slope body; μ is the water supply; v is the drop rate of the water level; ΔH is the maximum drop distance of the reservoir water;

The seepage flow of the slope body section from the highest point F to the seepage point E is:

The slope flow from seepage point E to slope angle C is:

In the formula: h _i is the water surface depth at the time of calculation, m; m ₁ is the slope rate; L is the horizontal distance from the highest point of the calculated infiltration line to the toe of the slope, m;

Make equation (6) equal to equation (7), obtain he _e , and then obtain The height h _x of the highest point F of the wetting surface at the corresponding horizontal distance x can be obtained by using the formula (8):

Step 6: Determination of the residual sliding thrust increment of the slope body within the range of the water level fluctuation under the action of the reservoir water level, including the following small steps:

For the blocks within the reservoir water level regulation range, without considering the transfer of force between the bars, the residual sliding thrust increment of the jth block caused by the drop of the reservoir water level can be determined according to Equation (9):

where:

Considering the force transfer between bars, the residual sliding thrust increment of the first bar within the reservoir water level regulation range under the condition of reservoir water level change ΔH is:

The residual sliding thrust increment of the slope within the reservoir water fluctuation range is:

where:

Step 7: Determination of composite water loading and response parameters of reservoir-type landslides, including the following small steps:

(1) Determination of the unit statistical analysis period;

(2) Determination of rainfall and reservoir water level loading and its response parameters;

Step 8: Determination of the prediction model of the composite hydrodynamic loading displacement response ratio: Based on the composite hydrodynamic loading and its displacement response statistics, the slope composite hydrodynamic loading displacement response ratio model can be determined, namely:

Step 9: Stability evaluation and monitoring and early warning of compound water slope, including the following small steps:

(1) According to the composite hydrodynamic loading displacement response ratio of different periods of the slope calculated in step 8, the slope stability can be evaluated and monitored and early warning:

When η=1 or η fluctuates around 1, it is determined that the slope is in the stable stage;

When η>1 and η keeps getting larger, it is determined that the slope is in the stage of unstable development;

(2) For the slope in the unstable development stage, according to the relationship curve of the dynamic load-increasing displacement response ratio with the composite hydrodynamic change, the change rate λ of the composite hydrodynamic load-increasing response ratio is determined as:

When the dynamic loading response ratio change rate λ _t is a constant, it is determined that the slope is in the stage of accelerated deformation;

When the dynamic loading response ratio change rate λ _t gradually increases, it is determined that the slope is in the overall slip stage, and the slope instability should be warned in time.

Preferably, in the first step, preliminary survey and mapping of the reservoir-type landslide to be evaluated are carried out to determine the distribution range and size characteristics of the landslide, so as to select a reasonable arrangement of the slope displacement monitoring points.

Preferably, in the second step (1), the monitoring equipment includes rainfall monitoring equipment, reservoir water level monitoring equipment and displacement monitoring equipment, wherein the rainfall monitoring equipment selects a fully automatic hydrological monitoring system, covering the slope monitoring area. monitoring, so that the measured rainfall is representative; the reservoir water level monitoring equipment selects the GPRS remote reservoir water level monitoring system, and is arranged and installed at the slope monitoring point according to the installation requirements; the displacement monitoring equipment selects the wireless GPS displacement monitoring system. Displacement and deformation monitoring points and displacement monitoring reference points shall be arranged at the monitoring point locations, and wireless monitoring equipment shall be installed, and the buried monitoring equipment shall be closely integrated with the surface of the landslide body, and the equipment shall be independent and non-interfering with each other, and the displacement change value of each monitoring point shall be can be effectively monitored.

Preferably, in the second step (2) of the step 2, the real-time monitoring and data processing of the slope displacement, rainfall and reservoir water level are performed synchronously on a monthly basis for the rainfall J, reservoir water level H and displacement S in the landslide area to be measured. monitoring, and transmit the above monitoring data to the remote monitoring room through the slope site data signal collector for classification and preprocessing, and then the preprocessed monthly rainfall ΔJ, monthly reservoir water level change ΔH and n displacement monitoring points monthly Average value of displacement change Enter the details into the Excel table.

Preferably, in the step 3, the following small steps are included:

(1) Determination of basic physical and mechanical property parameters of the landslide: According to the geological and topographical data of the landslide in the reservoir, the inclination angle θ i of the overall sliding surface of the underlying bedrock and the slope angle θ _i , the slope angle of the slope, etc. are comprehensively determined by means of geological survey, exploration and geophysical prospecting. The change law of the vertical burial depth _Hi of the slope body; the physical and mechanical property parameters of the slope and the underlying bedrock surface (γ, c, );

(2) Determination of the landslide body segmentation method: According to the change of the overall slip plane dip angle θ _i of the underlying bedrock, a downward vertical line is drawn at the position where the slip plane dip angle θ _i of the underlying bedrock changes greatly. , divide the slope into n vertical blocks; since the inclination angle θ _i of the slip surface within the range of each block has no obvious change, it can be assumed that the sliding surface of each calculation block of the landslide is a straight line, that is, the entire The sliding surface is a polyline on the section.

Preferably, in the fifth step, for a reservoir-type slope sliding along the bedrock surface, the highest point of the slope infiltration surface drops along the bedrock surface as the reservoir water level drops. According to statistics from a large number of actual monitoring data, the infiltration line The speed of falling is related to k/μv and the maximum drop distance ΔH.

Preferably, in the sixth step, the height of the infiltration line at any position can be determined according to the infiltration line equation (8) of the slope during the decline of the reservoir water level. The average value is used as the wetting line for the block to calculate the height ΔH _j .

Preferably, in the seventh step (1), according to the reservoir-type landslide rainfall and the variation law of the reservoir water level, the present invention selects the rainfall, reservoir water, and displacement monitoring data in the month when the reservoir water level drops for calculation and analysis, and takes each month as a Statistical analysis and forecasting period per unit, and the number of statistical analysis and forecasting periods can be determined from this.

Preferably, in the seventh step (2), according to the monitoring data obtained in the second step, read the cumulative monthly rainfall ΔJ _t , the monthly reservoir water level drop value ΔH _t and the monthly displacement change in the early t periods of the slope, respectively. mean The overall residual sliding thrust increment _ΔE'Jt of the slope body above the slope body above the water level line of the slope body caused by the accumulated rainfall in the first t cycles calculated in step 4 is taken as the rainfall loading parameter of the landslide; The overall residual sliding thrust increment ΔE′ _Ht of the slope body within the range of the reservoir water level fluctuation caused is used as the reservoir water loading parameter of the landslide; the sum of ΔE′ _Ht and ΔE′ _Jt is used as the composite hydrodynamic loading parameter of the t-th cycle of the reservoir-type landslide; The average value of the cumulative displacement change of the landslide monitored in the first t cycles It is used as the displacement response parameter of the landslide under the coupled dynamic action of rainfall and reservoir water.

Preferably, in the step 8, under the condition of stable initial period reservoir water level, the overall residual sliding thrust increment ΔE' _J0 of the block above the water level caused by rainfall is used as the initial dynamic loading of the composite water, and the corresponding displacement As the initial dynamic loading displacement response; the overall residual sliding thrust increment ΔE′ _Jt of the block above the water level caused by the previous t cycles of rainfall and the overall residual sliding thrust increment ΔE′ _Ht of the block within the reservoir water fluctuation range caused by the reservoir water The sum is used as the composite hydrodynamic loading of the t period, and its corresponding cumulative displacement As the t period dynamic loading displacement response.

The beneficial effects of the present invention are as follows: the method for predicting the bank slope stability of a composite hydrodynamic reservoir according to the present invention is based on the comprehensive analysis of the relationship between the residual sliding thrust and displacement deformation characteristics of the reservoir-type landslide and the dynamic factors such as rainfall and reservoir water level changes. In the above, the dynamic load-increasing displacement response ratio model of the single factor of rainfall and reservoir water was improved, and the reservoir-type landslide composite hydrodynamic load-increasing displacement response ratio model was established, and the parameters of the reservoir-type landslide composite hydrodynamic load-increasing displacement response ratio were revealed. Based on the corresponding relationship of landslide stability, the evolution law of reservoir-type slope stability is analyzed and evaluated.

Description of drawings

Fig. 1 is the process flow schematic diagram of the present invention.

FIG. 2 is a schematic diagram of the layout of the landslide monitoring points of the present invention.

Fig. 3 is a sectional view of the soil strip of the present invention.

FIG. 4 is a schematic diagram of the force of the unit bar of the rainfall-affected slope according to the present invention.

Fig. 5 is a position diagram of the slope wetting line of the present invention.

FIG. 6 is a schematic diagram of the force of the slope block of the slope affected by the reservoir water according to the present invention.

In the figure: 01, slope body,; 02, displacement monitoring point; 03, tensile crack at the trailing edge.

Detailed ways

In order to make the purpose and technical scheme of the present invention clearer, the present invention will be described in further detail below in conjunction with the embodiments.

Example 1:

As shown in Figure 1 to Figure 6, the method for predicting the bank slope stability of a composite hydrodynamic reservoir according to the present invention, the steps are as follows:

Step 1: Preliminary investigation of reservoir-type landslides and selection of displacement monitoring points

Preliminary survey and mapping of the reservoir-type landslide to be evaluated shall be carried out to determine the distribution range and size of the landslide and other characteristics, so as to select a reasonable layout of the slope displacement monitoring point 02: ①According to the reservoir water level adjustment plan, the slope body 01 to 02 in contact with the highest reservoir water level Set n displacement monitoring points (n ≥ 3) within the range of the trailing edge tensile crack 03; ② displacement monitoring reference points (no less than 3) are selected in the stable bedrock or non-deformed area outside the monitoring landslide mass to form displacement Monitoring and control network to ensure self-checking and comprehensive monitoring of slope monitoring points.

Step 2: Layout and installation of monitoring equipment and processing of monitoring data

(1) Layout and installation of monitoring equipment

The monitoring equipment of the present invention includes rainfall monitoring equipment, reservoir water level monitoring equipment and displacement monitoring equipment, wherein the rainfall monitoring equipment selects an automatic hydrological monitoring system, and covers monitoring in the slope monitoring area, so that the measured rainfall is representative; The water level monitoring equipment adopts the GPRS remote reservoir water level monitoring system, and is installed at the slope monitoring point according to the installation requirements; the displacement monitoring equipment adopts the wireless GPS displacement monitoring system, and the displacement and deformation monitoring points and displacement monitoring are arranged at the monitoring points of the slope body. Install wireless monitoring equipment at the reference point, and ensure that the buried monitoring equipment is closely integrated with the surface of the landslide body, and the equipment is independent and non-interfering with each other, and the displacement change value of each monitoring point can be effectively monitored, as shown in Figure 2.

(2) Real-time monitoring and data processing of slope displacement and rainfall, reservoir water level

The rainfall J, reservoir water level H and displacement S in the landslide area to be measured are monitored synchronously on a monthly basis, and the above-mentioned monitoring data are transmitted to the remote monitoring room through the data signal collector of the slope site for classification and preprocessing. The processed monthly rainfall ΔJ, the monthly reservoir water level change ΔH and the average value of the monthly displacement change of n displacement monitoring points Enter details into an Excel spreadsheet.

Step 3: Determination of the basic physical and mechanical property parameters of the landslide and the method of dividing the slope body

(1) Determination of basic physical and mechanical property parameters of landslide

According to the geological and topographic data of the reservoir landslide, geological survey, exploration and geophysical prospecting are used to comprehensively determine the variation law of the inclination angle θ _i of the overall slip plane of the bedrock underlying the accumulation layer slope and the vertical burial depth _Hi of the slope body; The physical and mechanical property parameters of the slope and the underlying bedrock surface (γ, c, ).

(2) Determination of landslide body segmentation method

According to the change of the inclination angle θ _i of the overall slip plane of the underlying bedrock, a downward vertical line is drawn at the position where the slip plane inclination angle θ _i of the underlying bedrock changes greatly, and the slope is divided into n vertical blocks. ; Since the inclination angle θ _i of the slip surface within the range of each block has no obvious change, it can be assumed that the sliding surface of each calculation block of the landslide is a straight line, that is, the entire sliding surface is a broken line in the section (Fig. 3).

Step 4: Determination of the overall residual sliding thrust increment of the slope above the water level under the action of rainfall

(1) Determination of the average groundwater level of the landslide due to rainfall

From Principle 1 and Figure 4, it can be known that the relationship between effective rainfall and average groundwater level change: h _t =AJ _t +B (A and B are related to the properties of rock and soil, A>0). The present invention proposes to use the engineering geological analogy method to linearly fit other landslide rainfall and groundwater historical monitoring data in the area, and comprehensively determine the rock and soil property parameters A and B of the landslide mass to be evaluated. Furthermore, according to formula (1), the average groundwater level increment Δh _t caused by rainfall at time t can be determined.

Δh _t =(h _t -h _t-1 )=A(J _t -J _t-1 )=AΔJ _t (1)

(2) Determination of the residual sliding thrust increment of the i-th block under the action of rainfall

According to Principle 1, for the blocks above the reservoir water level, without considering the transfer of force between the bars, the change in the residual sliding thrust of the i-th block is:

Considering the force transfer between strips, the residual sliding thrust increment of the first strip under groundwater changes is:

The overall residual sliding thrust increment from the front end of the i-th block to the trailing edge of the slope is:

where:

Step 5: Determination of slope infiltration line in the process of reservoir water level decline

For the reservoir-type slope sliding along the bedrock surface, the highest point of the slope wetting surface will drop along the bedrock surface with the decrease of the reservoir water level. According to a large number of actual monitoring data statistics, the falling speed of the infiltration line is related to k/μv (k is the permeability coefficient of the slope; μ is the water supply; v is the falling speed of the water level) and the maximum drop distance ΔH. Therefore, according to the actual monitoring data of a large number of reservoir landslides, the present invention can determine that the highest point of the seepage infiltration surface under the actual fluctuation of the reservoir water level is:

In the formula: k is the permeability coefficient of the slope body; μ is the water supply; v is the drop rate of the water level; ΔH is the maximum drop distance of the reservoir water.

According to Principle 2 and Figure 5, the seepage flow of the slope body from the highest point F to the seepage point E is:

The slope flow from seepage point E to slope angle C is:

Among them, h _i is the water surface depth at the time of calculation, m; m ₁ is the slope ratio; L is the horizontal distance from the highest point of the calculated infiltration line to the toe of the slope, m; let formula (6) be equal to formula (7), and obtain he _e , to obtain The height h _x of the highest point F of the wetting surface at the corresponding horizontal distance x can be obtained by using the formula (8):

Step 6: Determination of the residual sliding thrust increment of the slope within the range of the water level fluctuation under the action of the reservoir water level

The height of the wetting line at any position can be determined according to the wetting line equation (8) of the slope during the decline of the reservoir water level. The wetting line calculates the height ΔH _j .

For the blocks within the reservoir water level regulation range, according to the principle (3) and Figure 6, without considering the transfer of force between the bars, the residual sliding thrust of the jth block caused by the decrease of the reservoir water level can be determined according to the formula (9). Increment:

where:

Considering the force transfer between bars, the residual sliding thrust increment of the first bar within the reservoir water level regulation range under the condition of reservoir water level change ΔH is:

The residual sliding thrust increment of the slope within the reservoir water fluctuation range is:

where:

Step 7: Determination of composite water loading and response parameters of reservoir-type landslides

(1) Determination of unit statistical analysis period

According to the variation law of rainfall and reservoir water level in reservoir-type landslides, the present invention selects the monitoring data of rainfall, reservoir water and displacement in the month when the reservoir water level drops for calculation and analysis, and takes each month as a unit for statistical analysis and prediction period, and based on this, the statistical analysis can be determined. with the number of forecast periods.

(2) Determination of rainfall and reservoir water level loading and its response parameters

According to the monitoring data obtained in step 2, read the cumulative monthly rainfall ΔJ _t , the monthly reservoir water level drop value ΔH _t and the average monthly displacement change in the early t periods of the slope, respectively. The overall residual sliding thrust increment _ΔE'Jt of the slope above the slope body above the water level line of the slope body caused by the accumulated rainfall in the first t cycles calculated in step 4 is taken as the rainfall loading parameter of the landslide; the cumulative reservoir water level in the first t cycles calculated in step 6 is decreased The overall residual sliding thrust increment ΔE′ _Ht of the slope body within the range of the reservoir water level fluctuation caused is used as the reservoir water loading parameter of the landslide; the sum of ΔE′ _Ht and ΔE′ _Jt is used as the composite hydrodynamic loading parameter of the t-th cycle of the reservoir-type landslide; The average value of the cumulative displacement change of the landslide monitored in the first t cycles It is used as the displacement response parameter of the landslide under the coupled dynamic action of rainfall and reservoir water.

Step 8: Determination of the prediction model of the composite hydrodynamic load-increasing displacement response ratio

Under the condition of stable reservoir water level in the initial period, the overall residual sliding thrust increment ΔE′ _J0 of the block above the water level caused by rainfall is taken as the initial dynamic loading of composite water, and the corresponding displacement as the initial dynamic loading displacement response. The sum of the overall residual sliding thrust increment ΔE′ _Jt of the block above the water level caused by the previous t periods of rainfall and the overall residual sliding thrust increment ΔE′ _Ht of the block within the reservoir water fluctuation range caused by the reservoir water is taken as the composite hydrodynamic force of the t period Loading amount, its corresponding cumulative displacement As the t period dynamic loading displacement response. Based on the composite hydrodynamic loading and its displacement response statistics, the displacement response ratio model of the slope composite hydrodynamic loading can be determined, namely:

In the formula: ΔE′ _Ht +ΔE′ _Jt — t period compound hydrodynamic loading; ΔE′ _J0 — rainfall hydrodynamic loading under the condition of stable reservoir water level in the initial period; —Displacement response amount caused by t period composite water loading; - The displacement response amount caused by rainfall hydrodynamic loading under the condition of stable reservoir water level in the initial period.

Step 9: Stability evaluation and monitoring and early warning of compound water slope

(1) According to the composite hydrodynamic loading displacement response ratio of different periods of the slope calculated in step 8, the slope stability can be evaluated and monitored and early warning:

When η=1 or η fluctuates around 1, it is determined that the slope is in the stable stage;

When η>1 and η continues to increase, it is determined that the slope is in the stage of unstable development.

(2) For the slope in the unstable development stage, the present invention proposes to determine the change rate λ _t of the composite hydrodynamic load-increasing response ratio according to the relationship curve of the dynamic load-increasing displacement response ratio with the composite hydrodynamic change:

When the dynamic loading response ratio change rate λ _t is a constant, it is determined that the slope is in the stage of accelerated deformation;

When the dynamic loading response ratio change rate λ _t gradually increases, it is determined that the slope is in the overall slip stage, and the slope instability should be warned in time.

Principle 1:

Rainfall is the main inducing factor of landslides, and its influence on the stability of landslides is usually realized by transforming into groundwater. Therefore, groundwater is a direct factor affecting the stability of landslides, and changes in groundwater levels will inevitably lead to changes in landslide dynamics and displacement. Now, taking the uniformly water-filled slope blocks of equal thickness as an example (Fig. 4), the groundwater level, its sliding force and its stability change rules are analyzed for this type of slope.

First, the soil skeleton block in the sliding soil mass of the slope is selected as the research object.

The change of the groundwater infiltration line with time is the main factor for the dynamic change of the slope. The gravity of the blocks below and above the infiltration line is calculated by the floating weight and the natural weight respectively. The sliding force and anti-slip force of the bar are expressed as follows:

T= _Wsinθ +Pw (14)

in,

W=V _u γ+V _d γ′ (16)

P _w = γ _w V _d sinθ (17)

where T is the sliding force of the strip, R is the anti-slip force of the strip, W is the gravity of the strip, _pw is the penetration force, c is the cohesive force of the sliding surface, l is the length of the bottom surface of the strip, and V _u is the volume above the wetting line , V _d is the volume below the wetting line, θ is the slope angle, is the internal friction angle of the sliding surface, γ is the natural weight, γ′ is the floating weight, and _γw is the water weight.

The wetting line changes in parallel from the GF position to the IJ position (the force of the bar at the IJ position is represented by the addition subscript 1, the area of the GFIJ is represented by S, S=lh(t)), and the change of the bar gravity is expressed as:

(W ₁ -W)=( _{γS IJCE} +γ′S _ABJI )-( _{γS ECFG} +γ′S _ABFG )=(γ′-γ)S<0 (18)

The change in permeability is expressed as:

P _w1 -P _w = γ _w Ssinθ>0 (19)

The change of the remaining sliding thrust of the bar with time:

in,

Therefore, the remaining sliding thrust of the bar is always greater than 0, that is, ΔE(t)>0.

Principle 2:

According to the regulation plan of the slope reservoir water level, the water level decline stage of the reservoir is equivalent to a uniform drop, and the empirical calculation formula of the highest point of the slope seepage infiltration surface is determined according to formula (1):

In the formula: k is the permeability coefficient of the slope, μ is the water supply; v is the drop rate of the reservoir water level; ΔH is the maximum drop distance of the reservoir water.

As can be seen from Figure 5, the seepage flow of the slope body section from the highest point F to the seepage point E is:

The slope flow from seepage point E to slope angle C is:

Among them, _hi is the water surface depth at the time of calculation, _m ; m1 is the slope ratio; L is the horizontal distance from the highest point of the calculated infiltration line to the foot of the slope, m; Equation (2) is equal to formula (3), and we can obtain h _e , to obtain The height h _x of the highest point F of the wetting surface at the corresponding horizontal distance x can be obtained by using the formula (2):

Principle 3:

The influence of the rise and fall of the reservoir water on the slope is caused by the rise and fall of the groundwater level indirectly through the infiltration of the reservoir water, so the change of the groundwater level is the direct dynamic factor that induces the landslide. Therefore, the transformation relationship between the reservoir water level and the infiltration line can be used to study the dynamic effects of reservoir water changes on the slope. It is assumed that the reservoir slope is homogeneous and isotropic, with a fixed inclination angle and a uniform change in slope thickness, and deformation and instability occur under the dynamic action of the reservoir water. The soil skeleton block in the sliding soil mass of the slope is selected as the research object, and the slope model and the force of the block under the dynamic change of reservoir water are shown in Figure 6.

In Figure 6, _wi is the total gravity of the sliding soil; Ri is the anti- _sliding force on the sliding surface; _Ni is the effective stress of the soil; a is the corresponding infiltration line when the reservoir water level is the highest; b is the reservoir water level The corresponding infiltration line at the lowest time; θ is the inclination angle of the sliding surface; h is the vertical height of the slider; h ₁ is the vertical height from the infiltration line a to the top of the slope; _hi is the elevation difference between the highest reservoir water level and the lowest reservoir water level; h _2i is the vertical height from infiltration line b to infiltration line a; _h3i is the vertical height from the lowest reservoir water level hb to infiltration line _b ; _h4 is the vertical height from the bottom of the slope to the lowest reservoir water level _hb .

The "substitution method" is used, that is, the sliding force of the water weight in the surrounding slide below the infiltration line and above the water level outside the slope to the slope body is used to replace the sliding force of the seepage force on the slope body, and the weight of the part of the sliding body below the water level outside the slope is the same as that of still water. Considering the buoyancy effect, except that the weight of the sliding mass below the water level of the soil slope is considered as the weight of buoyancy, only when calculating the sliding force in the stability coefficient formula, the part of the soil below the wetting line and above the water level outside the slope is calculated as the saturated bulk density; When sliding, the weight of this part of the soil is calculated by the floating bulk density. The following expressions of sliding force and anti-sliding force of sliding soil are obtained:

When the reservoir water level is at its highest:

Sliding force:

T _a =[γh ₁ +γ′(h _2i +h _3i +h ₄ )]sinθ (26)

Slip resistance:

When the reservoir water level is the lowest:

Sliding force:

T _b =[γ(h ₁ +h _2i )+γ _sa h _t3i +γ′h ₄ ]sinθ (28)

Slip resistance:

In the formula: T _a is the sliding force on the soil sliding surface when the wetting line is a; _Ra is the anti-sliding force on the soil sliding surface when the wetting line is a; T _b is the soil sliding surface when the wetting line is b _Rb is the anti-sliding force on the soil sliding surface when the wetting line is b; c is the cohesive force on the sliding surface; is the internal friction angle of the sliding surface; l is the length of the bottom surface of the strip; γ is the natural weight, γ _sat is the saturation weight, and γ′ is the floating weight.

Therefore, for a specific reservoir slope, the slope sliding force increment caused by the reservoir water level falling from the highest to the lowest is:

In the formula: ΔE _i is the sliding force increment of the slope caused by the drop of the reservoir water level; E _a is the sliding force on the sliding soil when the reservoir water level is the highest, and E _b is the sliding force on the sliding soil when the reservoir water level is the lowest.

As can be seen from Fig. 6, for a particular slope, assuming that the shape of the infiltration line changes uniformly during the decline of the reservoir water level every year, then h _i , h _2i , and h _3i always maintain a fixed proportion during the decline of the reservoir water level, that is, h _i :h _2i :h _3i =1:B ₂ :B ₃ , (wherein, B ₂ and B ₃ are proportional coefficients, which respectively represent the height of the infiltration line from the highest water level and the lowest water level in the process of the decline of the reservoir water level, accounting for the maximum water level of the reservoir water level The ratio of the difference, since h _2i +h _3i = _hi , that is, B ₂ +B ₃ =1, both B ₂ and B ₃ are greater than 0 and less than 1). Combined with Equation (16), ΔE _i can be simplified to the following function with only unknown quantity _hi :

Among them, in the formula: B ₃ =ΔH _j /ΔH _j (t), B ₂ =1−B ₃ .

Assuming that the midpoint ΔH _j of the wetting line of any block _j is h _3i , B ₂ and B ₃ can be obtained; hi is the change of the reservoir water level.

Example 2:

The following is a detailed description of a reservoir-type composite water landslide as an example. The landslide is an accumulation landslide along the Yangtze River, which is a typical reservoir-type landslide. The water level of the reservoir drops from May to September every year. The monitoring time in this example is from May to September 2012.

As shown in Figure 1, the specific implementation steps of the method for predicting the bank slope stability of a composite hydrodynamic reservoir according to the present invention are as follows:

Step 1: Preliminary investigation of reservoir-type landslides and selection of displacement monitoring points

Preliminary survey and mapping of the reservoir-type landslide to be evaluated shall be carried out to determine the distribution range and size of the landslide and other characteristics, so as to select a reasonable layout of the slope displacement monitoring points: ①According to the reservoir water level adjustment plan, the slope body that contacts the highest reservoir water level to the trailing edge Set up 3 displacement monitoring points within the tensile fracture range; ②The three displacement monitoring reference points are selected in the stable bedrock or non-deformed area outside the monitored landslide mass to form a displacement monitoring and control network to ensure self-checking and control of slope monitoring full monitoring.

Step 2: Layout and installation of monitoring equipment and processing of monitoring data

(1) Layout and installation of monitoring equipment

The monitoring equipment of the present invention includes rainfall monitoring equipment, reservoir water level monitoring equipment and displacement monitoring equipment, wherein the rainfall monitoring equipment selects an automatic hydrological monitoring system, and covers monitoring in the slope monitoring area, so that the measured rainfall is representative; The water level monitoring equipment adopts the GPRS remote reservoir water level monitoring system, and is installed at the slope monitoring point according to the installation requirements; the displacement monitoring equipment adopts the wireless GPS displacement monitoring system, and the displacement and deformation monitoring points and displacement monitoring are arranged at the monitoring points of the slope body. Wireless monitoring equipment is installed at the reference point, and the buried monitoring equipment is closely integrated with the surface of the landslide body, and the equipment is independent of each other and does not interfere with each other. The displacement change value of each monitoring point can be effectively monitored, as shown in Figure 2.

(2) Real-time monitoring and data processing of slope displacement and rainfall, reservoir water level

The rainfall J, reservoir water level H and displacement S in the landslide area to be measured are monitored synchronously on a monthly basis, and the above-mentioned monitoring data are transmitted to the remote monitoring room through the data signal collector of the slope site for classification and preprocessing. The processed monthly rainfall ΔJ, the monthly reservoir water level change ΔH and the average value of the monthly displacement change of n displacement monitoring points Please see Table 1 for detailed entry into the Excel table.

Table 1: Record table of monthly rainfall, monthly reservoir water level change, and monthly displacement change of displacement monitoring points

Step 3: Determination of the basic physical and mechanical property parameters of the landslide and the method of dividing the slope body

(1) Determination of basic physical and mechanical property parameters of landslide

According to the geological and topographical data of the reservoir landslide, geological survey, exploration and geophysical prospecting are used to comprehensively determine the variation law of the inclination angle θ _i of the overall slip plane of the bedrock underlying the accumulation layer slope and the vertical burial depth _hi of the slope body; The physical and mechanical property parameters of the slope and the underlying bedrock surface (γ, c, ), see Table 2.

(2) Determination of landslide body segmentation method

According to the change of the inclination angle θ _i of the overall slip plane of the underlying bedrock, a downward vertical line is drawn at the position where the slip plane inclination angle θ _i of the underlying bedrock changes greatly, and the slope is divided into 10 vertical blocks. ; Since the inclination angle θ _i of the slip surface within the range of each block has no obvious change, it can be assumed that the sliding surface of each calculation block of the landslide is a straight line, that is, the entire sliding surface is a broken line in the section (Fig. 3), Its calculation parameters are shown in Table 2.

Table 2: Calculation parameter table of 10 vertical blocks of landslide body

Step 4: Determination of the overall residual sliding thrust increment of the slope above the water level under the action of rainfall

(1) Determination of the average groundwater level of the landslide due to rainfall

From Principle 1 and Figure 4, it can be known that the relationship between effective rainfall and average groundwater level change: h _t =AJ _t +B (A and B are related to the properties of rock and soil, A>0). The present invention proposes to use the engineering geological analogy method to linearly fit other landslide rainfall and groundwater historical monitoring data in the area, and comprehensively determine the rock and soil property parameters A=0.8 and B=7.5 of the landslide mass to be evaluated. Furthermore, according to formula (1), the average groundwater level increment Δh _t caused by rainfall at time t can be determined, as shown in Table 3.

Δh _t =(h _t -h _t-1 )=A(J _t -J _t-1 )=AΔJ _t (1)

Table 3: Record table of effective rainfall and average groundwater level change

(2) Determination of the residual sliding thrust increment of the i-th block under the action of rainfall

According to principle 1, for the blocks above the reservoir water level (blocks 1-5), without considering the transfer of force between the bars, the change in the remaining sliding thrust of the i-th block is:

Considering the force transfer between strips, the residual sliding thrust increment of the first strip under groundwater changes is:

The overall residual sliding thrust increment from the front end of the i-th block to the trailing edge of the slope is:

where:

See Table 4 for the variation of the remaining sliding thrust of blocks 1-5.

Table 4: Vertical Bar 1-5 Residual Glide Thrust Change Scale

Bar 1 2 3 4 5 ΔE_hi(KN) 28.84 37.22 30.59 18.33 13.44 ΔE′_hi(KN) 28.84 64.00 92.54 102.60 114.15

Step 5: Determination of slope infiltration line in the process of reservoir water level decline

For the reservoir-type slope sliding along the bedrock surface, the highest point of the slope wetting surface will drop along the bedrock surface with the decrease of the reservoir water level. According to a large number of actual monitoring data statistics, the falling speed of the infiltration line is related to k/μv (k is the permeability coefficient of the slope; μ is the water supply; v is the falling speed of the water level) and the maximum drop distance ΔH. Therefore, according to the actual monitoring data of a large number of reservoir landslides, the present invention can determine that the highest point of the seepage infiltration surface under the actual fluctuation of the reservoir water level is:

According to the actual measurement, the permeability coefficient of the slope body k=0.01m/d; water supply μ=0.025; water level drop rate v=0.2m/d; are 6m, 12m, 18m, 24m, and 30m. According to formula (5), h ₀ under the condition of water level drop in May, June, July, August, and September are determined to be 4.2m, 8.4m, 12.6m, 16.8m, and 21m, respectively. .

According to Principle 2 and Figure 5, the seepage flow of the slope body from the highest point F to the seepage point E is:

The slope flow from seepage point E to slope angle C is:

Taking the water surface drop ΔH of 6m in May as an example, hi is the water surface depth _hi = _175-6 = 159m; the slope rate m ₁ = 0.5; the horizontal distance from the highest point of the infiltration line to the slope foot is L = 460m; let Equation (6) is equal to Equation (7), obtain he = _173.2m , and then obtain Reuse formula (8) to obtain the height of the highest point F of the wetting surface at the corresponding horizontal distance x in May

Step 6: Determination of the residual sliding thrust increment of the slope within the range of the water level fluctuation under the action of the reservoir water level

The height of the wetting line at any position can be determined according to the wetting line equation (8) of the slope during the decline of the reservoir water level. The wetting line calculates the height ΔH _j .

Table 5: Wetted line calculation height calculation table

For the blocks within the reservoir water level regulation range, according to the principle (3) and Figure 6, without considering the transfer of force between the bars, the residual sliding thrust of the jth block caused by the decrease of the reservoir water level can be determined according to the formula (9). Increment:

where:

Considering the force transfer between bars, the residual sliding thrust increment of the first bar within the reservoir water level regulation range under the condition of reservoir water level change ΔH is:

The residual sliding thrust increment of the slope within the reservoir water fluctuation range is:

where:

According to the data in Table 5, combined with formula (9) in May, when the reservoir water falls within the fluctuation range of 169m, the remaining sliding thrust increments of 6-10 blocks on the slope are shown in Table 6:

Table 6: Vertical Bar 6-10 Remaining Glide Thrust Change Scale

Bar 6 7 8 9 10 ΔE_Hi(KN) 51.76 47.94 44.06 30.25 6.68 ΔE′_Hi(KN) 51.76 99.71 143.77 174.01 180.69

Therefore, in May, the residual sliding thrust of the slope within the reservoir water fluctuation range was 299.63KN. Similarly, the remaining sliding thrust of the slope within the reservoir water fluctuation range in June, July, August and September can be calculated according to steps 5 and 6. The increments are 590.2KN, 901KN, 1203.2KN, and 1508.5KN respectively.

Step 7: Determination of composite water loading and response parameters of reservoir-type landslides

(1) Determination of unit statistical analysis period

According to the variation law of rainfall and reservoir water level in reservoir-type landslides, the present invention selects the monitoring data of rainfall, reservoir water and displacement in the month when the reservoir water level drops for calculation and analysis, and takes each month as a unit for statistical analysis and prediction period, and based on this, the statistical analysis can be determined. with the number of forecast periods.

(2) Determination of rainfall and reservoir water level loading and its response parameters

According to the monitoring data obtained in step 2, read the cumulative monthly rainfall ΔJ _t , the monthly reservoir water level drop value ΔH _t and the average monthly displacement change in the early t periods of the slope, respectively. The overall residual sliding thrust increment _ΔE'Jt of the slope above the slope body above the water level line of the slope body caused by the accumulated rainfall in the first t cycles calculated in step 4 is taken as the rainfall loading parameter of the landslide; the cumulative reservoir water level in the first t cycles calculated in step 6 is decreased The overall residual sliding thrust increment ΔE′ _Ht of the slope body within the range of the reservoir water level fluctuation caused is used as the reservoir water loading parameter of the landslide; the sum of ΔE′ _Ht and ΔE′ _Jt is used as the composite hydrodynamic loading parameter of the t-th cycle of the reservoir-type landslide; The average value of the cumulative displacement change of the landslide monitored in the first t cycles It is used as the displacement response parameter of the landslide under the coupled dynamic action of rainfall and reservoir water.

Step 8: Determination of the prediction model of the composite hydrodynamic load-increasing displacement response ratio

Under the condition of stable reservoir water level in the initial period, the overall residual sliding thrust increment ΔE′ _J0 of the block above the water level caused by rainfall is taken as the initial dynamic loading of composite water, and the corresponding displacement as the initial dynamic loading displacement response. The sum of the overall residual sliding thrust increment ΔE′ _Jt of the block above the water level caused by the previous t periods of rainfall and the overall residual sliding thrust increment ΔE′ _Ht of the block within the reservoir water fluctuation range caused by the reservoir water is taken as the composite hydrodynamic force of the t period Loading amount, its corresponding cumulative displacement As the t period dynamic loading displacement response. Based on the composite hydrodynamic loading and its displacement response statistics, the displacement response ratio model of the slope composite hydrodynamic loading can be determined, namely:

The composite hydrodynamic loading and loading response parameters from May to September are shown in Table 7.

Table 7: Composite hydrodynamic loading and loading response parameter table from May to September

In the formula: ΔE′ _Ht +ΔE′ _Jt — t period compound hydrodynamic loading; ΔE′ _J0 — rainfall hydrodynamic loading under the condition of stable reservoir water level in the initial period; —Displacement response amount caused by t period composite water loading; - The displacement response amount caused by rainfall hydrodynamic loading under the condition of stable reservoir water level in the initial period.

Step 9: Stability evaluation and monitoring and early warning of compound water slope

(1) According to the composite hydrodynamic loading displacement response ratio of different periods of the slope calculated in step 8, the slope stability can be evaluated and monitored and early warning:

Table 8: Slope stability evaluation and monitoring and early warning record table

month 5 6 7 8 9 η_t 1.00 1.02 1.39 2.31 16.91

Since the slope η>1 and η keeps increasing, it is determined that the slope is in an unstable development stage.

(2) For the slope in the unstable development stage, the present invention proposes a relationship curve according to the dynamic load-increasing displacement response ratio with the composite hydrodynamic change, see Table 9, and determines that the composite hydrodynamic load-increasing response ratio change rate λ is:

Table 9: Composite hydrodynamic load-increasing response ratio change rate record table

month 6 7 8 9 λ_t 0.000044 0.000842 0.001972 0.033896

Since the change rate λ of the dynamic load-increasing response ratio gradually increases, it is determined that the slope is in the overall slip stage, and the slope instability should be warned in time at this time.

The invention is widely used in the occasions of slope stability evaluation and landslide disaster monitoring and early warning, and particularly relates to the prediction parameters and stability evaluation method of reservoir type composite hydrodynamic landslide.

The above descriptions are only preferred embodiments of the present invention, and are not intended to limit the present invention. All equivalent modifications, equivalent replacements and improvements made within the spirit and principles of the present invention should be included in the present invention. covered by the patent.

Claims (10)

1. a method for predicting the bank slope stability of a composite hydrodynamic reservoir, is characterized in that, comprises the steps: Step 1: Preliminary investigation of reservoir-type landslides and selection of displacement monitoring points, including the following small steps: (1) According to the reservoir water level adjustment plan, set n displacement monitoring points within the range from the slope contacted by the highest reservoir water level to the trailing edge tensile crack, n≥3; (2) The number of displacement monitoring reference points shall be no less than 3, which shall be selected in the stable bedrock or non-deformed area outside the monitoring landslide body, and form a displacement monitoring and control network to ensure self-checking and comprehensive monitoring of slope monitoring points; Step 2: Layout and installation of monitoring equipment and processing of monitoring data, including the following small steps: (1) The layout and installation of monitoring equipment; (2) Real-time monitoring and data processing of slope displacement and rainfall, reservoir water level; Step 3: Determination of the basic physical and mechanical property parameters of the landslide and the method of dividing the slope; Step 4: Determination of the overall residual sliding thrust increment of the slope above the water level under the action of rainfall, including the following small steps: (1) Determination of the average groundwater level of the landslide due to rainfall: The relationship between the effective rainfall and the average groundwater level change: h _t = AJ _t + B (A and B are related to the properties of rock and soil, A >0); it is proposed to use the engineering geological analogy method to compare the rainfall of other landslides in this area with the The historical monitoring data of groundwater can be linearly fitted to comprehensively determine the rock and soil property parameters A and B of the landslide mass to be evaluated, and then the average groundwater level increment Δh _t caused by rainfall at time t can be determined according to formula (1); Δh _t =(h _t -h _t-1 )=A(J _t -J _t-1 )=AΔJ _t (1) (2) Determination of the residual sliding thrust increment of the i-th block under the action of rainfall: For the bars above the reservoir water level line, without considering the transfer of force between bars, the variation of the remaining sliding thrust of the i-th bar is: Considering the force transfer between strips, the residual sliding thrust increment of the first strip under groundwater changes is: The overall residual sliding thrust increment from the front end of the i-th block to the trailing edge of the slope is: where: Step 5: Determination of the slope infiltration line during the decline of the reservoir water level, including the following small steps: According to the statistics of the actual monitoring data of a large number of reservoir landslides, it can be determined that the highest point of the seepage infiltration surface under the actual fluctuation of the reservoir water level is: In the formula: k is the permeability coefficient of the slope body; μ is the water supply; v is the drop rate of the water level; ΔH is the maximum drop distance of the reservoir water; The seepage flow of the slope body section from the highest point F to the seepage point E is: The slope flow from seepage point E to slope angle C is: In the formula: h _i is the water surface depth at the time of calculation, m; m ₁ is the slope rate; L is the horizontal distance from the highest point of the calculated infiltration line to the toe of the slope, m; Make equation (6) equal to equation (7), obtain he _e , and then obtain The height h _x of the highest point F of the wetting surface at the corresponding horizontal distance x can be obtained by using the formula (8): Step 6: Determination of the residual sliding thrust increment of the slope body within the range of the water level fluctuation under the action of the reservoir water level, including the following small steps: For the blocks within the regulation range of the reservoir water level, without considering the transfer of force between the bars, the residual sliding thrust increment of the jth block caused by the decrease of the reservoir water level can be determined according to Equation (9): where: Considering the force transfer between bars, the residual sliding thrust increment of the first bar within the reservoir water level regulation range under the condition of reservoir water level change ΔH is: The residual sliding thrust increment of the slope within the reservoir water fluctuation range is: where: B ₃ =ΔH _j /ΔH _j (t), B ₂ =1−B ₃ ; Step 7: Determination of composite water loading and response parameters of reservoir-type landslides, including the following small steps: (1) Determination of the unit statistical analysis period; (2) Determination of rainfall and reservoir water level loading and its response parameters; Step 8: Determination of the prediction model of the composite hydrodynamic loading displacement response ratio: Based on the composite hydrodynamic loading and its displacement response statistics, the slope composite hydrodynamic loading displacement response ratio model can be determined, namely: Step 9: Stability evaluation and monitoring and early warning of compound water slope, including the following small steps: (1) According to the composite hydrodynamic loading displacement response ratio of different periods of the slope calculated in step 8, the slope stability can be evaluated and monitored and early warning: When η=1 or η fluctuates around 1, it is determined that the slope is in the stable stage; When η>1 and η keeps increasing, it is determined that the slope is in an unstable development stage; (2) For the slope in the unstable development stage, according to the relationship curve of the dynamic load-increasing displacement response ratio with the composite hydrodynamic change, the change rate λ _t of the composite hydrodynamic load-increasing response ratio is determined as: When the dynamic loading response ratio change rate λ _t is a constant, it is determined that the slope is in the stage of accelerated deformation; When the dynamic loading response ratio change rate λ _t gradually increases, it is determined that the slope is in the overall slip stage, and the slope instability should be warned in time. 2. The method for predicting the stability of the bank slope of a composite hydrodynamic reservoir according to claim 1, wherein in the step 1, preliminary survey and mapping are carried out for the reservoir-type landslide to be evaluated, and the landslide distribution range and size characteristics are determined. , so as to choose a reasonable layout of the slope displacement monitoring points. 3. The method for predicting the bank slope stability of a composite hydrodynamic reservoir according to claim 1, wherein in the second (1) step, the monitoring equipment comprises rainfall monitoring equipment, reservoir water level monitoring equipment and displacement Monitoring equipment, among which the rainfall monitoring equipment adopts the automatic hydrological monitoring system, covering monitoring in the slope monitoring area, so that the measured rainfall is representative; the reservoir water level monitoring equipment adopts the GPRS remote reservoir water level monitoring system, and the slope monitoring Layout and installation are carried out at the points according to the installation requirements; the displacement monitoring equipment adopts the wireless GPS displacement monitoring system, and the displacement deformation monitoring points and displacement monitoring reference points are arranged at the monitoring points of the slope body, and the wireless monitoring equipment is installed, and the buried monitoring equipment is guaranteed to be compatible with the landslide. The body surface layer is closely combined, the equipment is independent and non-interfering with each other, and the displacement change value of each monitoring point can be effectively monitored. 4. The method for predicting the bank slope stability of a composite hydrodynamic reservoir according to claim 3, wherein in the step 2 (2), the slope displacement and rainfall, reservoir water level real-time monitoring and data processing , and synchronously monitor the rainfall J, reservoir water level H and displacement S in the landslide area to be measured on a monthly basis, and transmit the above monitoring data to the remote monitoring room through the slope site data signal collector for classification and preprocessing. The monthly rainfall ΔJ, the monthly reservoir water level variation ΔH and the average monthly displacement variation of n displacement monitoring points obtained by preprocessing Enter the details into the Excel table. 5. The method for predicting the bank slope stability of a composite hydrodynamic reservoir according to claim 1 or 4, wherein in the step 3, the following steps are included: (1) Determination of basic physical and mechanical property parameters of the landslide: According to the geological and topographical data of the landslide in the reservoir, the inclination angle θ i of the overall sliding surface of the underlying bedrock and the slope angle θ _i , the slope angle of the slope, etc. are comprehensively determined by means of geological survey, exploration and geophysical prospecting. The variation law of the vertical burial depth H _i of the slope body; the physical and mechanical property parameters of the slope body and the underlying bedrock surface are comprehensively determined by in-situ tests or indoor geotechnical tests. (2) Determination of the landslide body segmentation method: According to the change of the overall slip plane dip angle θ _i of the underlying bedrock, a downward vertical line is drawn at the position where the slip plane dip angle θ _i of the underlying bedrock changes greatly. , divide the slope into n vertical blocks; since the inclination angle θ _i of the slip surface within the range of each block has no obvious change, it can be assumed that the sliding surface of each calculation block of the landslide is a straight line, that is, the entire The sliding surface is a polyline on the section. 6. The method for predicting the bank slope stability of a composite hydrodynamic reservoir according to claim 5, wherein in the step 5, for the reservoir-type slope sliding along the bedrock surface, the slope infiltration surface is the highest According to the statistics of a large number of actual monitoring data, the falling speed of the infiltration line is related to k/μv and the maximum drop distance ΔH. 7. The method for predicting the bank slope stability of a composite hydrodynamic reservoir according to claim 6, wherein in the step 6, any position can be determined according to the infiltration line equation (8) of the slope in the process of the reservoir water level falling The height of the wetting line at the place where the water level fluctuates, and the average height of the wetting line at both ends of the slope block j within the range of the water level fluctuation is used as the wetting line of the block to calculate the height ΔH _j . 8. The method for predicting the bank slope stability of a composite hydrodynamic reservoir according to claim 1 or 7, characterized in that, in the seventh step (1), according to the reservoir-type landslide rainfall and reservoir water level variation law, this The invention selects the monitoring data of rainfall, reservoir water and displacement in the month when the reservoir water level drops for calculation and analysis, and takes each month as a unit for statistical analysis and forecasting period, and the number of statistical analysis and forecasting periods can be determined based on this. 9. The method for predicting the bank slope stability of a composite hydrodynamic reservoir according to claim 8, wherein in the seventh step (2) of the step, according to the monitoring data obtained in the second step, the early stage of the slope is read respectively. Cumulative monthly rainfall ΔJ _t for t cycles, monthly reservoir water level drop ΔH _t and monthly average displacement change The overall residual sliding thrust increment _ΔE'Jt of the slope above the slope body above the water level line of the slope body caused by the accumulated rainfall in the first t cycles calculated in step 4 is taken as the rainfall loading parameter of the landslide; The overall residual sliding thrust increment ΔE′ _Ht of the slope body within the range of the reservoir water level fluctuation caused by it is used as the reservoir water loading parameter of the landslide; the sum of ΔE′ _Ht and ΔE′ _Jt is used as the composite hydrodynamic loading parameter of the t-th cycle of the reservoir-type landslide; The average value of the cumulative displacement change of the landslide monitored in the first t cycles It is used as the displacement response parameter of the landslide under the coupled dynamic action of rainfall and reservoir water. 10. The method for predicting the bank slope stability of a composite hydrodynamic reservoir according to claim 9, characterized in that, in the eighth step, under the condition of initial period reservoir water level stability, the overall remaining of the block above the water level line caused by rainfall The sliding thrust increment ΔE′ _J0 is used as the initial dynamic loading of composite water, and its corresponding displacement As the initial dynamic loading displacement response; the overall residual sliding thrust increment ΔE′ _Jt of the block above the water level caused by the previous t cycles of rainfall and the overall residual sliding thrust increment ΔE′ _Ht of the block within the reservoir water fluctuation range caused by the reservoir water The sum is used as the composite hydrodynamic loading of the t period, and its corresponding cumulative displacement As the t period dynamic loading displacement response.