CN109785584A

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

Info

Publication number: CN109785584A
Application number: CN201910085676.8A
Authority: CN
Inventors: 贺可强; 郭璐; 吴丽丽
Original assignee: Qingdao University of Technology
Current assignee: Qingdao University of Technology
Priority date: 2019-01-29
Filing date: 2019-01-29
Publication date: 2019-05-21

Abstract

The invention relates to a method for predicting stability of a composite hydrodynamic reservoir bank slope, and belongs to the technical field of slope stability evaluation and landslide hazard monitoring and early warning. The invention comprises the following steps: the method comprises the steps of reservoir type landslide initial survey and displacement monitoring point selection, monitoring equipment arrangement and installation and monitoring data processing, landslide basic physical and mechanical property parameter determination and slope strip division method determination, determination of slope integral remaining glide thrust increment above a rainfall action water level line, determination of a slope infiltration line in a reservoir water level descending process, determination of slope remaining glide thrust increment in a reservoir water level action water level variation range, determination of reservoir type landslide composite water loading and response parameters thereof, determination of a composite hydrodynamic load-increasing displacement response ratio prediction model, composite water slope stability evaluation and monitoring early warning, revealing the corresponding relation between the reservoir type landslide composite hydrodynamic load-increasing displacement response ratio parameters and the landslide stability, and analyzing and evaluating the reservoir type slope stability evolution rule according to the relation.

Description

Method for predicting stability of composite hydrodynamic reservoir bank slope

Technical Field

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

Background

The special engineering characteristics of the major hydraulic engineering and the complex water environment conditions determine the potential huge hazard of the reservoir type landslide. For reservoir type landslides, the probability of instability is increased if the reservoir type landslides encounter strong rainfall in the process of reservoir water level fluctuation. Therefore, the coupling effect of reservoir water and rainfall inevitably damages the in-situ underwater operation environment of the reservoir area, and forms a special composite water environment dynamic effect of the three gorges project reservoir area, so that the frequency and scale of occurrence of landslide disasters of the reservoir area are greatly influenced and controlled, and the formed composite water dynamic effect and the influence possibly generated on the stability of the slope of the reservoir area become the focus of attention in the field of disaster prevention and reduction at home and abroad. Therefore, the method for forecasting the catastrophe early warning of the reservoir type slope under the condition of studying and establishing the composite hydrodynamic force has important theoretical significance and application value for forecasting and preventing the reservoir type landslide in the three gorges engineering reservoir area and similar composite hydrodynamic force conditions.

At present, the most widely applied reservoir type landslide prediction and evaluation methods at home and abroad are a limit balance method, a displacement time sequence prediction method and a displacement dynamics method. The limit balance method is to assume a landslide body as a rigid body, analyze the mechanical balance state of the landslide body along a sliding surface, and evaluate the stability of the side slope by taking the ratio of the gliding force and the anti-sliding force as the safety coefficient K of the landslide. However, the mechanical evaluation model established by the method is a static model without time factors, and the assumed conditions and the limited conditions of modeling are more, so that the prediction evaluation result is easily influenced by the factors and has strong uncertainty, and the time of landslide can not be predicted; the displacement time sequence prediction method is to use the landslide displacement, the displacement rate or the displacement acceleration as landslide prediction parameters and analyze the change rule to predict the landslide stability and the instability time. Although the method overcomes the defects of the extreme balance method to a certain extent, the evaluated parameters are only displacement or displacement rate and the change rule thereof in the landslide evolution process, the cause of the landslide displacement or displacement rate change cannot be explained, the displacement prediction parameters adopted by the method are easy to be interfered by external factors to generate multi-period acceleration step-shaped oscillation change, the displacement acceleration step-shaped oscillation change cannot necessarily represent the integral instability of the landslide, and the displacement prediction parameters of the method have no uniform instability criterion, so that the occurrence time of the landslide disaster cannot be accurately judged and predicted. The displacement dynamics method mostly provides a method for simultaneously monitoring and integrating landslide rainfall (reservoir water level) and displacement or displacement rate so as to determine the coupling integrated power prediction parameters and evaluation methods of the landslide rainfall (reservoir water level) and the displacement or displacement rate. The prediction method overcomes the limitation that the traditional displacement time sequence prediction method only selects landslide displacement or displacement rate as monitoring and evaluation parameters, and overcomes the defect that the limit balance method cannot dynamically evaluate the stability of the side slope. However, in the current research, a single hydrodynamic variable such as rainfall or reservoir water is used as an inducing factor of the landslide for calculating the loading and unloading response ratio, and for reservoir type landslides, the deformation and damage of the landslide are often influenced by the reservoir water level change and the composite hydrodynamic force formed by the rainfall, the dynamic loading and unloading parameters of the landslide include the superposition of the two factors, and only the action of the single hydrodynamic factor on the landslide is considered, which may possibly result in misjudgment on the stability of the landslide. How to effectively evaluate and predict the stability of the reservoir type landslide according to the composite hydrodynamic conditions and the displacement change rule is still to be further researched.

Disclosure of Invention

Aiming at the limitations and disadvantages of the traditional composite water landslide stability evaluation and prediction method, the invention comprehensively considers the composite hydrodynamic effect of rainfall and reservoir water fluctuation on the reservoir type landslide according to the basic principle of elastoplasticity mechanics, establishes a reservoir type landslide composite hydrodynamic load-increasing displacement response ratio model through deducing the residual glide thrust increment under the action of different hydrodynamic forces, establishes the corresponding relation between the reservoir type landslide composite hydrodynamic load-increasing displacement response ratio parameter and the landslide stability coefficient and the criterion thereof, and analyzes and evaluates the evolution rule of the reservoir type landslide stability according to the corresponding relation.

The method for predicting the stability of the composite hydrodynamic reservoir bank slope comprises the following steps:

the method comprises the following steps: reservoir type landslide preliminary investigation and displacement monitoring point are selected, including the following substeps:

(1) setting n displacement monitoring points within the range from the slope body contacted with the highest reservoir water level to the rear edge tension crack according to a reservoir water level scheduling scheme, wherein n is more than or equal to 3;

(2) the number of the displacement monitoring datum points is not less than 3, and a stable bedrock or a deformation-free area outside the landslide body is selected to form a displacement monitoring control network, so that self-checking and comprehensive monitoring of slope monitoring points are guaranteed;

step two: the arrangement and installation of the monitoring equipment and the processing of the monitoring data comprise the following steps:

(1) arrangement and installation of monitoring equipment;

(2) monitoring slope displacement and rainfall, reservoir water level in real time and processing data;

step three: determining basic physical and mechanical property parameters of the landslide and a slope body dividing method;

step four: the method for determining the integral remaining gliding thrust increment of the slope above the water level line under the rainfall action comprises the following steps:

(1) determining the average underground water level of the landslide under the action of rainfall:

relation of effective rainfall to mean groundwater level variation: h is_t＝AJ_t+ B (A, B is related to rock-soil body properties, A > 0); the method is provided and applied to an engineering geology class ratio method, the rainfall capacity of other landslides in the area is linearly fitted with the historical monitoring data of the underground water, the property parameters A and B of the landslide mass rock-soil mass to be evaluated can be comprehensively determined, and the average underground water level increment delta h caused by rainfall at the moment t can be further determined according to the formula (1)_t；

Δh_t＝(h_t-h_t-1)＝A(J_t-J_t-1)＝AΔJ_t(1)

(2) Determining the residual gliding thrust increment of the ith block under the action of rainfall:

for the strips above the reservoir water line, under the transmission effect without considering the force among the strips, the residual glide thrust variation of the ith strip is as follows:

considering the force transmission effect among the strips, the 1 st strip block residual gliding thrust increment under the change of underground water is as follows:

the integral residual gliding thrust increment from the front end of the ith block to the rear edge of the side slope is as follows:

in the formula:

step five: the determination of the slope infiltration line in the reservoir water level descending process comprises the following steps:

according to the statistics of a large amount of actual reservoir landslide monitoring data, the highest point of the seepage infiltration surface position under the condition of actual reservoir water level fluctuation can be determined as follows:

in the formula: k is the permeability coefficient of the slope body; mu is the water degree; v is the deceleration of the water level; delta H is the maximum descending distance of reservoir water;

the seepage flow of the slope section from the highest point F to the seepage point E is as follows:

the slope flow from the exudation point E to the slope angle C is:

in the formula: h is_iCalculating the water depth m; m is₁Is the slope rate; l is the horizontal distance m from the highest point of the saturation line to the toe of the slope;

let equation (6) equal equation (7) to obtain h_eAnd then obtainThen, the height h of the highest point F of the wetting surface corresponding to the horizontal distance x can be obtained by the formula (8)_x：

Step six: the determination of the increment of the residual glide thrust of the slope in the water level variation range under the action of the reservoir water level comprises the following steps:

for the strips in the reservoir water level regulation range, under the condition of not considering the transmission effect of the forces among the strips, the residual glide thrust increment of the jth strip caused by the reservoir water level decline can be determined according to the formula (9):

in the formula:

considering the force transmission effect among the strips, the 1 st strip block remaining gliding thrust increment in the reservoir water level regulation range under the reservoir water level change delta H condition is as follows:

the increment of the residual glide thrust of the slope body in the reservoir water fluctuation range is as follows:

in the formula:

step seven: the determination of the reservoir type landslide composite water loading and the response parameters thereof comprises the following steps:

(1) determining a unit statistical analysis period;

(2) loading rainfall and reservoir water level and determining response parameters thereof;

step eight: determining a composite hydrodynamic load-increasing displacement response ratio prediction model: by taking the composite hydrodynamic load-increasing and displacement response statistics as the basis, the slope composite hydrodynamic load-increasing displacement response ratio model can be determined, namely:

step nine: the composite water slope stability evaluation and monitoring early warning method comprises the following steps:

(1) according to the composite hydrodynamic load-increasing displacement response ratio of the slope in different periods obtained by calculation in the step eight, the stability of the slope can be evaluated, monitored and early warned:

when η fluctuates around 1 or η, the slope is determined to be in a stable stage;

when η is larger than 1 and η is larger, the slope is judged to be in an unstable development stage;

(2) for the side slope in an unstable development stage, a relation curve that the power load-increasing displacement response ratio changes along with the composite hydrodynamic force is provided, and the change rate lambda of the composite hydrodynamic load-increasing response ratio is determined as follows:

response rate of change lambda when power load increases_tIf the constant is a constant, judging that the slope is in an accelerated deformation stage;

response rate of change lambda when power load increases_tAnd gradually increasing, judging that the side slope is in the integral sliding stage, and early warning on the instability of the side slope in time.

Preferably, in the first step, the reservoir type landslide to be evaluated is subjected to preliminary investigation and mapping, and the distribution range and the size characteristics of the landslide are determined, so that a reasonable arrangement mode of the side slope displacement monitoring points is selected.

Preferably, in the second step (1), the monitoring device comprises a rainfall monitoring device, a reservoir level monitoring device and a displacement monitoring device, wherein the rainfall monitoring device adopts a full-automatic hydrological monitoring system and is used for covering monitoring in a side slope monitoring area to enable the measured rainfall to be representative; the reservoir water level monitoring equipment selects a GPRS remote reservoir water level monitoring system and is arranged and installed at the side slope monitoring point according to the installation requirement; the displacement monitoring equipment selects a wireless GPS displacement monitoring system, displacement deformation monitoring points and displacement monitoring datum points are distributed at the monitoring points of the slope body, the wireless monitoring equipment is installed, the embedded monitoring equipment is tightly combined with the surface layer of the sliding slope body, the equipment is independent and mutually noninterfere, and the displacement change value of each monitoring point can be effectively monitored.

Preferably, in the second step (2), the slope displacement, the rainfall capacity and the reservoir level are monitored in real time and data are processed, the rainfall J, the reservoir level H and the displacement S of the landslide area to be detected are synchronously monitored in a month unit, the monitoring data are transmitted to a remote monitoring room through a slope field data signal collector and are subjected to classification pretreatment, and the average value of the month rainfall J, the month reservoir level variation delta H and the month displacement variation of n displacement monitoring points obtained through pretreatment is further subjected to classification pretreatmentAnd entering an Excel table in detail.

Preferably, the third step includes the following small steps:

(1) determining basic physical and mechanical property parameters of landslide: according to geology and landform of reservoir landslideData, comprehensively determining the inclination angle theta of the integral slip plane of the bed rock on the side slope of the accumulation layer by means of geological survey, exploration, geophysical prospecting and the like_iVertical buried depth H of slope body_iThe change rule of (2); the physical and mechanical property parameters (gamma, c,)；

(2) determining a landslide body strip method: according to the slope angle theta of the integral slip plane of the underlying bedrock_iVariation of (1) at the dip angle theta of the slip surface of the underlying foundation_iMaking a downward vertical line at the position with larger change, and dividing the slope body into n vertical blocks; due to the angle of inclination theta of the slip plane within the individual bars themselves_iThere is no significant change, so it can be assumed that the sliding surface of each computing block of the landslide is a straight line, i.e. the entire sliding surface is a broken line in cross section.

Preferably, in the fifth step, for the reservoir type slope sliding along the bed rock surface, the highest point of the slope infiltration surface is decreased along the bed rock surface along with the decrease of the reservoir water level, and according to statistics of a large amount of actual monitoring data, the falling speed of the infiltration line is related to k/μ v and the maximum fall distance Δ H.

Preferably, in the sixth step, the height of the saturation line at any position can be determined according to the saturation line equation (8) of the slope in the process of reservoir water level falling, and the average value of the heights of the saturation lines at two ends of the slope bar j in the water level fluctuation range is used as the calculated height Δ H of the saturation line of the bar j_j。

Preferably, in the seventh step (1), according to the reservoir type landslide rainfall and the reservoir level change rule, the rainfall, reservoir water and displacement monitoring data of the month with the reservoir level falling are selected for calculation and analysis, each month is taken as a unit for statistical analysis and prediction period, and the statistical analysis and prediction period number can be determined according to the unit statistical analysis and prediction period number.

Preferably, in the seventh step (2), the monitor obtained in the second stepMeasuring data, and respectively reading the accumulated monthly rainfall delta J of t periods in the early stage of the slope_tLunar reservoir water level drop value delta H_tMean value of variation of moon displacementThe integral gliding thrust increment delta E 'of the slope body above the water line of the slope body reservoir caused by the accumulated rainfall in the first t periods calculated in the step four'_JtAs rainfall loading parameters for landslide; the integral remaining sliding thrust increment delta E 'of the slope body in the reservoir water level fluctuation range caused by the accumulated reservoir water level reduction of the first t periods calculated in the step six'_HtAs a reservoir water loading parameter for landslide; is delta E'_HtAnd delta E'_JtThe sum is used as a composite hydrodynamic loading parameter of the t period of the reservoir type landslide; the average value of the accumulated displacement variation of the landslide monitored in the first t periodsAs displacement response parameter of the landslide under the coupling power of rainfall and reservoir water.

Preferably, in the step eight, under the condition that the reservoir water level is stable in the initial period, the residual gliding thrust increment delta E 'of the whole block above the water line caused by rainfall'_J0As combined water initial power load, its corresponding displacementAs the initial power loading displacement response; integral residual gliding thrust increment delta E 'of blocks above water line caused by rainfall in previous t periods'_JtStrip overall remaining gliding thrust increment delta E 'in reservoir water fluctuation range caused by reservoir water'_HtThe sum is taken as the t period composite hydrodynamic load and the corresponding accumulated displacementAs t-cycle dynamic loading displacement response.

The invention has the beneficial effects that: according to the method for predicting the stability of the bank slope of the compound hydrodynamic reservoir, on the basis of comprehensively analyzing the relation of power factors such as the residual glide thrust and displacement deformation characteristics of the reservoir type landslide, rainfall, reservoir water level change and the like, a dynamic load-increasing displacement response ratio model of a single factor of rainfall and reservoir water is improved, a reservoir type landslide compound hydrodynamic load-increasing displacement response ratio model is established, the corresponding relation between the parameters of the reservoir type landslide compound hydrodynamic load-increasing displacement response ratio and the stability of the landslide is disclosed, and the analysis and evaluation are performed on the stability evolution rule of the reservoir type landslide according to the model.

Drawings

FIG. 1 is a schematic process flow diagram of the present invention.

Fig. 2 is a schematic diagram of the landslide monitoring point arrangement of the present invention.

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

FIG. 4 is a schematic diagram of the force applied to the unit blocks of the rainfall-affected side slope of the present invention.

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

FIG. 6 is a schematic diagram of the stress of the bank water influence side slope body strip of the present invention.

In the figure: 01. a slope body; 02. displacement monitoring points; 03. the trailing edge stretches the crack.

Detailed Description

In order to make the object and technical solution of the present invention more apparent, the present invention will be further described in detail with reference to the following examples.

Example 1:

as shown in fig. 1 to 6, the method for predicting stability of a composite hydrodynamic reservoir bank slope according to the present invention includes the following steps:

the method comprises the following steps: reservoir type landslide initial survey and displacement monitoring point selection

The method comprises the steps of conducting preliminary survey and surveying on reservoir type landslides to be evaluated, determining characteristics such as landslide distribution range and size, and selecting a reasonable arrangement mode of slope displacement monitoring points 02, wherein ① sets n displacement monitoring points (n is more than or equal to 3) in a range from a slope body 01 contacted with the highest reservoir water level to a trailing edge tension crack 03 according to a reservoir water level scheduling scheme, and ② displacement monitoring reference points (not less than 3) are selected in stable bedrocks or deformation-free areas outside a monitored landslide body to form a displacement monitoring control network, so that self-checking is guaranteed, and slope monitoring points are controlled to be monitored comprehensively.

Step two: arrangement and installation of monitoring equipment and processing of monitoring data

(1) Arrangement and installation of monitoring devices

The monitoring equipment comprises rainfall monitoring equipment, reservoir level monitoring equipment and displacement monitoring equipment, wherein the rainfall monitoring equipment adopts a full-automatic hydrological monitoring system and is used for covering monitoring in a side slope monitoring area, so that the measured rainfall is representative; the reservoir water level monitoring equipment selects a GPRS remote reservoir water level monitoring system and is arranged and installed at the side slope monitoring point according to the installation requirement; the displacement monitoring equipment selects a wireless GPS displacement monitoring system, displacement deformation monitoring points and displacement monitoring reference points are arranged at monitoring point positions of a slope body, the wireless monitoring equipment is installed, the embedded monitoring equipment is tightly combined with the surface layer of the slope body, the equipment is independent and mutually noninterfere, and the displacement change value of each monitoring point can be effectively monitored, which is shown in figure 2.

(2) Slope displacement and rainfall, reservoir water level real-time monitoring and data processing

Synchronously monitoring the rainfall J, the reservoir water level H and the displacement S of the landslide area to be detected by taking a month as a unit, transmitting the monitoring data to a remote monitoring room through a side slope field data signal collector, carrying out classification pretreatment, and further carrying out pretreatment to obtain the rainfall J, the reservoir water level H and the displacement SThe average value of the monthly rainfall delta J, the monthly reservoir water level variation delta H and the monthly displacement variation of the n displacement monitoring pointsThe Excel table is entered in detail.

Step three: determination of basic physical and mechanical property parameters of landslide and slope body dividing method

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

According to geological and topographic data of reservoir landslide, the dip angle theta of the integral slip plane of the underlying bedrock of the side slope of the accumulation layer is comprehensively determined by means of geological survey, exploration, geophysical prospecting and the like_iVertical buried depth H of slope body_iThe change rule of (2); the physical and mechanical property parameters (gamma, c,)。

(2) determination of landslide body striping method

According to the slope angle theta of the integral slip plane of the underlying bedrock_iVariation of (2) inclination angle theta at slip plane of underlying bedrock_iMaking a downward vertical line at the position with larger change, and dividing the slope body into n vertical blocks; due to the angle of inclination theta of the slip plane within the individual bars themselves_iThere is no significant change, so it can be assumed that the sliding surface of each computing bar of the landslide is a straight line, i.e. the entire sliding surface is a broken line in section (fig. 3).

Step four: determination of integral residual glide thrust increment of slope body above water level line under rainfall action

(1) Determination of average groundwater level in landslide under rainfall

From principle 1 and fig. 4, it can be known that the relationship between the effective rainfall and the variation of the average groundwater level is: h is_t＝AJ_t+ B (A, B is related to the properties of the rock-soil mass, A > 0). Hair brushObviously, the method is provided to apply an engineering geology class comparison method, linear fitting is carried out on rainfall of other landslides in the area and historical monitoring data of underground water, and property parameters A and B of the landslide rock-soil mass to be evaluated can be comprehensively determined. Further, the average underground water level increment delta h caused by rainfall at the time t can be determined according to the formula (1)_t。

Δh_t＝(h_t-h_t-1)＝A(J_t-J_t-1)＝AΔJ_t(1)

(2) Determination of residual glide thrust increment of ith block under rainfall action

According to principle 1, for the bars above the reservoir water level, under the condition of not considering the transmission action of force among the bars, the residual sliding thrust variable quantity of the ith bar is as follows:

in the formula:

step five: determination of slope infiltration line in reservoir water level descending process

For a reservoir type slope that slides along the bed rock surface, the highest point of the slope wetting surface drops along the bed rock surface as the reservoir water level drops. According to statistics of a large amount of actual monitoring data, the falling speed of the saturation line is related to k/muv (k is the permeability coefficient of a slope body; mu is the water supply rate; v is the falling speed of the water level) and the maximum falling distance delta H. Therefore, the highest point of the seepage infiltration surface position under the condition of actual fluctuation of the reservoir water level can be determined by the invention according to a large amount of actual reservoir landslide monitoring data statistics:

in the formula: k is the permeability coefficient of the slope body; mu is the water degree; v is the deceleration of the water level; and deltaH is the maximum descending distance of reservoir water.

From the principle 2 and fig. 5, the seepage flow of the section of the slope from the highest point F to the seepage point E is as follows:

the slope flow from the exudation point E to the slope angle C is:

wherein h is_iCalculating the water depth m; m is₁Is the slope rate; l is the horizontal distance m from the highest point of the saturation line to the toe of the slope; let equation (6) equal equation (7) to obtain h_eAnd then obtainThen, the height h of the highest point F of the wetting surface corresponding to the horizontal distance x can be obtained by the formula (8)_x：

Step six: determination of slope residual glide thrust increment in reservoir water level variation range

The height of the saturation line at any position can be determined according to the saturation line equation (8) of the side slope in the process of reservoir water level descending, and the average value of the heights of the saturation lines at two ends of a slope body block j in the water level fluctuation range is used as the calculated height delta H of the saturation line of the block_j。

For the bar in the reservoir water level regulation and control range, according to the principle (3) and the graph 6, under the condition of not considering the transmission effect of force among the bars, the residual glide thrust increment of the jth bar caused by reservoir water level decline can be determined according to the formula (9):

in the formula:

step seven: reservoir type landslide composite water loading and determination of response parameters thereof

(1) Determination of unit statistical analysis period

According to the reservoir type landslide rainfall and reservoir water level change rule, the rainfall, reservoir water and displacement monitoring data of the month with the reservoir water level falling are selected for calculation and analysis, the month is taken as a unit for statistical analysis and prediction period, and the statistical analysis and prediction period number can be determined according to the unit.

(2) Rainfall and reservoir level loading and determination of response parameters thereof

Respectively reading the accumulated monthly rainfall delta J of t periods at the early stage of the slope according to the monitoring data obtained in the step two_tLunar reservoir water level drop value delta H_tMean value of variation of moon displacementThe integral gliding thrust increment delta E 'of the slope body above the water level line of the slope body reservoir caused by the accumulated rainfall in the first t periods calculated in the step four'_JtAs a rainfall loading parameter for landslides; the integral residual glide thrust increment delta E 'of the slope body in the reservoir water level fluctuation range caused by the accumulated reservoir water level reduction of the first t periods calculated in the step six'_HtAs a reservoir water loading parameter for landslide; is delta E'_HtAnd delta E'_JtThe sum is used as a composite hydrodynamic loading parameter of the t period of the reservoir type landslide; the average value of the accumulated displacement variation of the landslide monitored in the first t periodsThe displacement response parameter is used as the displacement response parameter of the landslide under the coupling power action of rainfall and reservoir water.

Step eight: determination of composite hydrodynamic load-increasing displacement response ratio prediction model

Under the condition of stable reservoir water level in the initial period, the integral residual gliding thrust increment delta E 'of the blocks above the water line caused by rainfall'_J0As combined water initial power load, its corresponding displacementAs the initial power loading displacement response. Integral residual gliding thrust increment delta E 'of blocks above water line caused by rainfall in previous t periods'_JtStrip block integral residual glide thrust increment delta E 'in reservoir water fluctuation range caused by reservoir water'_HtThe sum is taken as the t period composite hydrodynamic load and the corresponding accumulated displacementAs a power loading displacement response during the t cycle. By taking the composite hydrodynamic load-increasing and displacement response statistics thereof as a basis, a slope composite hydrodynamic load-increasing displacement response ratio model can be determined, namely:

in the formula: delta E'_Ht+ΔE′_Jt-t cycles of compound hydrodynamic loading; delta E'_J0The rainfall dynamic loading capacity is under the condition of stable reservoir water level in the initial period;-displacement response due to composite water loading for t cycles;and displacement response quantity caused by dynamic loading of rainfall under the condition of stable reservoir water level in the initial period.

Step nine: composite water slope stability evaluation and monitoring early warning

when η is greater than 1 and η becomes larger, the slope is judged to be in an unstable development stage.

(2) For the side slope in an unstable development stage, the invention provides that the change rate lambda of the compound hydrodynamic load-increasing response ratio is determined according to the relation curve of the dynamic load-increasing displacement response ratio changing along with the compound hydrodynamic force_tComprises the following steps:

Principle 1:

rainfall is a major causative factor in landslide occurrence, affecting landslide stability, usually through conversion to groundwater. Therefore, underground water is a direct factor influencing landslide stability, and changes in underground water level inevitably cause landslide power changes and displacement changes. The underground water level of the slope, the gliding power and the stability change rule of the underground water level are analyzed by taking a slope strip block with uniform water filling and equal thickness as an example (figure 4).

Firstly, soil skeleton blocks in the sliding soil body of the side slope are selected as research objects, and the stress condition of the slope body blocks under the change of underground water power is shown in figure 4.

The change of the underground water immersion line along with time is a main factor of the change of the power of the side slope, and the gravity of the blocks below and above the immersion line is calculated by adopting the floating weight and the natural weight respectively. The gliding and anti-gliding forces of the bar are respectively expressed as follows:

T＝Wsinθ+P_w(14)

wherein,

W＝V_uγ+V_dγ′ (16)

P_w＝γ_wV_dsinθ (17)

in the formula: t is the downward sliding force of the bar, R is the anti-sliding force of the bar, W is the gravity of the bar, p_wFor osmotic power, c is the slip surface cohesion, l is the bar base length, V_uVolume above the saturation line, V_dThe volume below the saturation line, theta is the slope angle,the angle of friction in the sliding surface, gamma is the natural gravity, gamma' is the floating gravity, gamma_wIs the heaviness of the water.

The wetting line changes from GF position to IJ position (the stress of the IJ position bar is represented by increasing the lower subscript 1, the area of GFIJ is represented by S, and S ═ lh (t)), and the change of the bar gravity is represented as:

(W₁-W)＝(γS_IJCE+γ′S_ABJI)-(γS_ECFG+γ′S_ABFG)＝(γ′-γ)S＜0 (18)

the change in osmotic force is expressed as:

P_w1-P_w＝γ_wSsinθ＞0 (19)

change of bar residual glide thrust with time:

wherein,

therefore, the residual gliding thrust of the bar is constantly greater than 0, namely: Δ E (t) > 0.

Principle 2:

according to the slope reservoir water level regulation and control scheme, equivalent to uniform-speed descending, the reservoir water level descending stage is determined according to an empirical calculation formula of the highest point of the side slope seepage infiltration surface position as shown in the formula (1):

in the formula: k is the permeability coefficient of the slope body, and mu is the water degree; v is reservoir water level deceleration; and deltaH is the maximum descending distance of reservoir water.

From fig. 5, the seepage flow rate of the section of the slope from the highest point F to the seepage point E is:

the slope flow from the exudation point E to the slope angle C is:

wherein h is_iCalculating the water depth m; m is₁Is the slope rate; l is the horizontal distance m from the highest point of the saturation line to the toe of the slope; let equation (2) equal equation (3) to obtain h_eAnd then obtainThen, the height h of the highest point F of the immersion surface corresponding to the horizontal distance x can be obtained by the formula (2)_x:

Principle 3:

the influence of reservoir water lifting on the side slope is caused by underground water level lifting caused by reservoir water infiltration indirectly, so that the change of the underground water level is a direct power factor for inducing landslide. Therefore, the dynamic influence of reservoir water change on the slope can be researched by using the conversion relation between the reservoir water level and the infiltration line. The reservoir side slope is homogeneous and isotropic, has a fixed inclination angle and is uniform in slope thickness, and deforms and destabilizes under the action of reservoir water power. Soil skeleton blocks in the side slope sliding soil body are selected as research objects, and the stress conditions of the side slope model and the slope body blocks under the change of the reservoir water power are shown in figure 6.

In FIG. 6, w_iThe total gravity of the sliding soil body; r_iThe sliding resistance on the sliding surface; n is a radical of_iEffective stress on soil body; a is a corresponding infiltration line when the reservoir water level is highest; b is a corresponding infiltration line when the reservoir water level is lowest; theta is the inclination angle of the sliding surface; h is the vertical height of the sliding block; h is₁The vertical height from the infiltration line a to the top of the slope; h is_iThe height difference between the highest reservoir water level and the lowest reservoir water level is obtained; h is_2iThe vertical height from the wetting line b to the wetting line a; h is_3iIs the lowest reservoir level h_bTo the vertical height of the wetting line b; h is₄From the bottom of the slope to the lowest reservoir level h_bThe vertical height of (a).

The 'substitution method' is used for substituting the gliding power of the seepage force on the slope body by the gliding power of the water weight in the slope body surrounding below the infiltration line and above the water level line outside the slope, the weight of the part of the slide body below the water level line outside the slope is considered according to the action of hydrostatic buoyancy, except that the weight of the slide body below the water level line of the soil slope is considered according to the buoyancy weight, the part of the soil body below the infiltration line and above the water level outside the slope is calculated according to the saturated volume weight only when the sliding force is calculated in the stability coefficient formula; and the gravity of the part of soil body is calculated by using the floating volume weight when the skid resistance is calculated. Obtaining the following expressions of the downward sliding force and the anti-sliding force of the sliding soil body:

when the reservoir water level is highest:

downward sliding force:

T_a＝[γh₁+γ′(h_2i+h_3i+h₄)]sinθ (26)

and (3) skid resistance:

when the reservoir water level is lowest:

downward sliding force:

T_b＝[γ(h₁+h_2i)+γ_{s a}h_t3i+γ′h₄]sinθ (28)

and (3) skid resistance:

in the formula: t is_aThe downward sliding force on the soil body sliding surface when the infiltration line is a; r_aThe sliding resistance on the soil body sliding surface when the infiltration line is a; t is_bThe downward sliding force on the soil body sliding surface when the infiltration line is b; r_bThe anti-sliding force on the soil body sliding surface when the infiltration line is b; c is the internal force of the sliding surface;is the internal friction angle of the sliding surface; l is the length of the bottom surface of the bar block; gamma is the natural gravity, gamma_satSaturated gravities and gamma' superficial gravities.

Therefore, for a specific reservoir slope, the slope descending power increment caused by the reservoir water level from the highest level to the lowest level is as follows:

in the formula: delta E_iThe power increment of slope downslide caused by reservoir water level reduction; e_aIs reservoir waterThe sliding force on the sliding soil body at the highest position, E_bThe sliding force is the sliding force applied to the sliding soil body when the reservoir water level is lowest.

As can be seen from FIG. 6, for a particular slope, if the shape of the saturation line changes uniformly during the reservoir water level decrease every year, h is_i、h_2i、h_3iThe constant proportion is always kept in the process of reservoir water level reduction, namely h_i:h_2i:h_3i＝1:B₂:B₃(wherein, B₂、B₃Is a proportionality coefficient which respectively represents the proportion of the maximum water level and the minimum water level height of the wetting line in the descending process of the reservoir water level to the maximum water level difference of the reservoir water level, because h_2i+h_3i＝h_iI.e. B₂+B₃1, thus B₂、B₃Both greater than 0 and less than 1). Recombination formula (16), Delta E_iCan be simplified to contain only unknown quantity h_iThe following function:

wherein, in the formula:B₃＝ΔH_j/ΔH_j(t),B₂＝1-B₃。

suppose that any one block j wets the midpoint Δ H of the line_jIs h_3iThen B can be obtained₂、B₃；h_iThe reservoir level drop variation is used.

Example 2:

the following description will be made in detail by taking a certain reservoir type composite water landslide as an example. The landslide is a typical reservoir type landslide of a storage layer on the Yangtze river coast, the reservoir water level is reduced by 5-9 months every year, and the monitoring time of the embodiment is 5-9 months in 2012.

As shown in fig. 1, the method for predicting stability of a composite hydrodynamic reservoir bank slope specifically includes the following steps:

The method comprises the steps of conducting preliminary survey and surveying on a reservoir type landslide to be evaluated, determining characteristics such as distribution range and size of the landslide, and accordingly selecting a reasonable arrangement mode of slope displacement monitoring points, wherein ① sets 3 displacement monitoring points in a range from a slope body contacted with the highest reservoir water level to a rear edge tension crack according to a reservoir water level scheduling scheme, 3 displacement monitoring datum points ② are selected from stable bedrocks or deformation-free areas outside a monitored landslide body, a displacement monitoring control network is formed, and self-checking and comprehensive monitoring of the slope monitoring points are guaranteed.

(1) Arrangement and installation of monitoring devices

The monitoring equipment comprises rainfall monitoring equipment, reservoir level monitoring equipment and displacement monitoring equipment, wherein the rainfall monitoring equipment adopts a full-automatic hydrological monitoring system and is used for covering monitoring in a side slope monitoring area, so that the measured rainfall is representative; the reservoir water level monitoring equipment selects a GPRS remote reservoir water level monitoring system and is arranged and installed at the side slope monitoring point according to the installation requirement; the displacement monitoring equipment selects a wireless GPS displacement monitoring system, displacement deformation monitoring points and displacement monitoring datum points are arranged at the monitoring point positions of the slope body, the wireless monitoring equipment is installed, the embedded monitoring equipment is tightly combined with the surface layer of the sliding slope body, the equipment is mutually independent and does not interfere with each other, and the displacement change value of each monitoring point can be effectively monitored, as shown in figure 2.

Synchronously monitoring rainfall J, reservoir water level H and displacement S of the landslide area to be detected by taking a month as a unit, and collecting data signals through a side slope fieldThe device transmits the monitoring data to a remote monitoring room for classification pretreatment, and then average values of the monthly rainfall delta J, the monthly reservoir water level variation delta H and the monthly displacement variation of n displacement monitoring points obtained by the pretreatment are averagedThe Excel table is entered in detail, see table 1.

Table 1: monthly rainfall, monthly reservoir water level variation and monthly displacement variation record table of displacement monitoring point

According to geological and topographic data of reservoir landslide, the dip angle theta of the integral slip plane of the underlying bedrock of the side slope of the accumulation layer is comprehensively determined by means of geological survey, exploration, geophysical prospecting and the like_iVertical buried depth h of slope body_iThe change rule of (2); the physical and mechanical property parameters (gamma, c,) See table 2.

(2) Determination of landslide body striping method

According to the slope angle theta of the integral slip plane of the underlying bedrock_iVariation of (2) inclination angle theta at slip plane of underlying bedrock_iMaking downward vertical lines at the positions with larger changes, and dividing the slope body into 10 vertical blocks; due to the angle of inclination theta of the slip plane within the individual bars themselves_iThere is no significant change, so it can be assumed that the sliding surface of each computing block of the landslide is a straight line, i.e. the whole sliding surface is a broken line in section (fig. 3), the computing parameters of which are calculatedThe numbers are shown in Table 2.

Table 2: calculation parameter table for 10 vertical strips of landslide body strip

(1) Determination of average groundwater level in landslide under rainfall

From principle 1 and fig. 4, it can be known that the relationship between the effective rainfall and the variation of the average groundwater level is: h is_t＝AJ_t+ B (A, B is related to the properties of the rock-soil mass, A > 0). The invention provides an engineering geology comparison method, which is used for performing linear fitting on rainfall of other landslides in the area and historical monitoring data of underground water, and comprehensively determining the landslide rock-soil mass property parameter A to be evaluated to be 0.8 and the landslide rock-soil mass property parameter B to be 7.5. Further, the average underground water level increment delta h caused by rainfall at the time t can be determined according to the formula (1)_tSee table 3.

Δh_t＝(h_t-h_t-1)＝A(J_t-J_t-1)＝AΔJ_t(1)

Table 3: effective rainfall and average groundwater level variation recording meter

According to principle 1, for the bars (bars 1-5) above the reservoir water level, the variation of the residual glide thrust of the ith bar is as follows without considering the transmission action of the force between the bars:

in the formula:

the variation of the residual sliding thrust of the blocks 1-5 is shown in Table 4.

Table 4: 1-5 vertical bar residual glide thrust change meter

Bar block	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

the actual measurement shows that the permeability coefficient k of the slope body is 0.01 m/d; the water feeding degree mu is 0.025; the falling speed v of the water level is 0.2 m/d; 5. the maximum descending distances delta H of the reservoir water in months of 6, 7, 8 and 9 are respectively 6m, 12m, 18m, 24m and 30m, and H under the condition that the water level of the months of 5, 6, 7, 8 and 9 is descended is respectively determined according to the formula (5)₀Respectively 4.2m, 8.4m, 12.6m, 16.8m and 21 m.

the slope flow from the exudation point E to the slope angle C is:

take 5 months of water surface descent Δ H of 6m as an example, H_iFor calculating the water depth h_i175-6-159 m; slope rate m₁0.5; calculating the horizontal distance L from the highest point of the soaking line to the toe of the slope to be 460 m; let equation (6) equal equation (7) to obtain h_eThen, the average value is 173.2m, andthen, the height of the highest point F of the wetting surface at the position of the horizontal distance x corresponding to the month 5 can be obtained by the formula (8)

Table 5: calculating table for calculating height of saturation line

in the formula:

according to the data in the table 5, the amount of the rest sliding thrust increment left by 6-10 blocks of the slope body when the reservoir water drops to 169m fluctuation range in combination with the formula (9)5 is shown in the table 6:

table 6: 6-10 residual glide thrust change gauge for vertical bar

Bar block	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, the remaining downslide thrust increment of the slope body within the reservoir water fluctuation range in the month 5 is 299.63KN, and similarly, the remaining downslide thrust increments of the slope body within the reservoir water fluctuation ranges in the months 6, 7, 8 and 9 can be respectively 590.2KN, 901KN, 1203.2KN and 1508.5KN according to the step five and the step 6.

(1) Determination of unit statistical analysis period

Under the condition of stable reservoir water level in the initial period, the integral residual gliding thrust increment delta E 'of the blocks above the water line caused by rainfall'_J0As combined water initial power load, its corresponding displacementAs initial power plusAnd (4) load displacement response quantity. Integral residual gliding thrust increment delta E 'of blocks above water line caused by rainfall in previous t periods'_JtStrip block integral residual glide thrust increment delta E 'in reservoir water fluctuation range caused by reservoir water'_HtThe sum is taken as the t period composite hydrodynamic load and the corresponding accumulated displacementAs a power loading displacement response during the t cycle. By taking the composite hydrodynamic load-increasing and displacement response statistics thereof as a basis, a slope composite hydrodynamic load-increasing displacement response ratio model can be determined, namely:

the combined hydrodynamic loading and loading response parameters for the 5-9 months are shown in table 7.

Table 7: 5-9 month composite hydrodynamic loading and loading response parameter table

table 8: slope stability evaluation and monitoring early warning recording table

Month of the year	5	6	7	8	9
						η_t	1.00	1.02	1.39	2.31	16.91

Since the side slope η > 1 and η is becoming larger, it is determined that the side slope is in an unstable development stage.

(2) For the slope in the unstable development stage, the invention provides a relation curve according to the change of the power load-increasing displacement response ratio along with the composite hydrodynamic force, see table 9, and the change rate λ of the composite hydrodynamic load-increasing response ratio is determined as follows:

table 9: recording table for change rate of composite hydrodynamic load-increasing response ratio

Month of the year	6	7	8	9
					λ_t	0.000044	0.000842	0.001972	0.033896

Because the change rate lambda of the power load-increasing response ratio is gradually increased, the slope is judged to be in the integral sliding stage, and the slope instability is timely pre-warned.

The invention is widely applied to the occasions of slope stability evaluation and landslide hazard monitoring and early warning, and particularly relates to a prediction parameter and stability evaluation method for reservoir type composite hydrodynamic landslide.

The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, but rather the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention as defined by the appended claims.

Claims

1. A method for predicting stability of a composite hydrodynamic reservoir bank slope is characterized by comprising the following steps:

(2) the number of the displacement monitoring datum points is not less than 3, and stable bedrock or a deformation-free area outside the landslide body is selected to form a displacement monitoring control network, so that self-checking and comprehensive monitoring of slope monitoring points are guaranteed;

(1) arrangement and installation of monitoring equipment;

Δh_t＝(h_t-h_t-1)＝A(J_t-J_t-1)＝AΔJ_t(1)

for the strips above the reservoir water line, under the transmission effect without considering the force among the strips, the residual gliding thrust variation of the ith strip is as follows:

in the formula:

the slope flow from the exudation point E to the slope angle C is:

for the strips in the reservoir water level regulation range, under the condition of not considering the transmission effect of the forces among the strips, the residual glide thrust increment of the jth strip caused by the reservoir water level reduction can be determined according to the formula (9):

in the formula:

in the formula:B₃＝ΔH_j/ΔH_j(t),B₂＝1-B₃；

(1) determining a unit statistical analysis period;

(2) for the side slope in an unstable development stage, a relation curve that the power load-increasing displacement response ratio changes along with the composite hydrodynamic force is provided, and the change rate lambda of the composite hydrodynamic load-increasing response ratio is determined_tComprises the following steps:

2. The method for predicting the stability of the bank slope of the compound hydrodynamic library according to claim 1, wherein in the first step, the reservoir type landslide to be evaluated is preliminarily surveyed and mapped, and the distribution range and the size characteristics of the landslide are determined, so that a reasonable arrangement mode of the slope displacement monitoring points is selected.

3. The method for forecasting stability of a composite hydrodynamic bank slope according to claim 1, wherein in the second step (1), the monitoring devices include a rainfall monitoring device, a bank level monitoring device and a displacement monitoring device, wherein the rainfall monitoring device is a fully automatic hydrological monitoring system, and is monitored in a covering manner in the slope monitoring area, so that the measured rainfall is representative; the reservoir water level monitoring equipment selects a GPRS remote reservoir water level monitoring system and is arranged and installed at the side slope monitoring point according to the installation requirement; the displacement monitoring equipment selects a wireless GPS displacement monitoring system, displacement deformation monitoring points and displacement monitoring reference points are arranged at the monitoring point positions of the slope body, the wireless monitoring equipment is installed, the embedded monitoring equipment is tightly combined with the surface layer of the slope body, the equipment is independent and mutually noninterfere, and the displacement change value of each monitoring point can be effectively monitored.

4. The method for forecasting the stability of the composite hydrodynamic reservoir bank slope according to claim 3, wherein in the second step (2), the slope displacement, the rainfall amount and the reservoir level are monitored and processed in real time, the rainfall amount J, the reservoir level H and the displacement S of the landslide area to be measured are monitored synchronously in a month unit, the monitoring data are transmitted to a remote monitoring room through a slope field data signal collector and are subjected to classification pretreatment, and the average value of the month rainfall amount delta J, the month reservoir level variation delta H and the month displacement variation of n displacement monitoring points obtained through the pretreatment is further subjected to classification pretreatmentThe Excel table is entered in detail.

5. The method for predicting stability of a composite hydrodynamic bank slope according to claim 1 or 4, wherein the third step includes the following steps:

(1) determining basic physical and mechanical property parameters of landslide: according to the geological and topographic data of reservoir landslide, comprehensive measures such as geological survey, exploration and geophysical prospecting are adoptedDetermining the inclination angle theta of the integral slip plane of the bed rock under the side slope of the accumulation layer_iVertical buried depth H of slope body_iThe change rule of (2); comprehensive determination of physical and mechanical parameters of slope and underlying rock surface by in-situ test or indoor geotechnical test

(2) Determining a landslide body strip method: according to the slope angle theta of the integral slip plane of the underlying bedrock_iVariation of (2) inclination angle theta at slip plane of underlying bedrock_iMaking a downward vertical line at the position with larger change, and dividing the slope body into n vertical blocks; due to the angle of inclination theta of the slip plane within the individual bars themselves_iThere is no significant change, so it can be assumed that the sliding surface of each computing bar of the landslide is a straight line, i.e., the entire sliding surface is a broken line in cross section.

6. The method for forecasting stability of a composite hydrodynamic bank slope according to claim 5, wherein in the fifth step, for a reservoir type slope sliding along a bed rock surface, the highest point of a slope infiltration surface is decreased along the bed rock surface along with the decrease of the reservoir water level, and the falling speed of an infiltration line is related to k/μ v and the maximum fall distance Δ H according to statistics of a large amount of actual monitoring data.

7. The method for predicting stability of a composite hydrodynamic bank slope according to claim 6, wherein in the sixth step, the height of the saturation line at any position can be determined according to the equation (8) of the saturation line of the slope during the falling of the bank water level, and the average value of the heights of the saturation lines at two ends of the slope bar j in the water level fluctuation range is used as the calculated height Δ H of the saturation line of the bar j_j。

8. The method for predicting the stability of the composite hydrodynamic bank slope according to claim 1 or 7, wherein in the seventh step (1), according to the reservoir type landslide rainfall and the reservoir level change rule, the method selects the rainfall, reservoir water and displacement monitoring data of the month with the reservoir level falling for calculation and analysis, and takes each month as a unit for statistical analysis and prediction period, so that the statistical analysis and prediction period number can be determined.

9. The method for predicting the stability of the bank slope of the composite hydrodynamic library according to claim 8, wherein in the seventh step (2), the accumulated monthly rainfall Δ J in the earlier t periods of the bank slope is respectively read according to the monitoring data obtained in the second step_tLunar reservoir water level drop value delta H_tMean value of variation of moon displacementThe integral gliding thrust increment delta E 'of the slope body above the water line of the slope body reservoir caused by the accumulated rainfall in the first t periods calculated in the step four'_JtAs a rainfall loading parameter for landslides; the integral residual glide thrust increment delta E 'of the slope body in the reservoir water level fluctuation range caused by the accumulated reservoir water level reduction of the first t periods calculated in the step six'_HtAs a reservoir water loading parameter for landslide; is delta E'_HtAnd delta E'_JtThe sum is used as a composite hydrodynamic loading parameter of the t period of the reservoir type landslide; the average value of the accumulated displacement variation of the landslide monitored in the first t periodsAs displacement response parameter of the landslide under the coupling power of rainfall and reservoir water.

10. The method for predicting stability of a composite hydrodynamic reservoir bank slope according to claim 9, wherein in the eighth step, under the condition of stable reservoir water level in the initial period, the integral remaining gliding thrust increment Δ E 'of the blocks above the water level line caused by rainfall'_J0As combined water initial power load, its corresponding displacementAs initial powerLoading displacement response quantity; integral residual gliding thrust increment delta E 'of blocks above water line caused by rainfall in previous t periods'_JtAnd reservoir water caused bar integral residual glide thrust increment delta E 'in reservoir water fluctuation range'_HtThe sum is taken as the t period composite hydrodynamic load and the corresponding accumulated displacementAs t-cycle dynamic loading displacement response.