Research Of Forecast, Evaluation And Protective Measures Of Bank Failure In Mountain Reservoir

The environgeologic and hydrogeologic conditions in riverbank will be greatlychanged when building reservoirs. The raise of waterlevel in reservoir reduces thestability of bank highly. It happens to all kinds of bank failures after building reservoir,especially in mountain reservoirs which commonly crosses many differentphysiognomies and there are all kinds of geologic structures. So it is very dangerous.This paper researches bank failure and its genetic mechanism, develop several newmethods of forecasting bank failure zone, evaluate the dangerous degree of bankfailure, and put forward bank protection measures. We investigate four typicalmountain reservoirs; do a series of physics model tests and works. The major creativeoutcome has been obtained as follows:(1) Base on a lot of field investigations, the characteristics of distribution anddeformation about bank failures is found, especially in Quaternary bank. In order toresearch the genetic mechanism of bank failure, we build four types lab physicsmodels of reservoir bank, including the model considering several factors and singlefactor, the model of soil bank and rock bank, and a model of actual reservoir bankzoom out. Simulate the happening course of bank failure, obtain a lot of data, andobserve some valuable phenomena. After analysis, some quantization relationship isgot between zone or amount of bank failure and angle of bank, bank composition orwaterlevel of reservoir.(2) And the types of bank failure of reservoir are systematically classified for thefirst time. And its genetic mechanism and damage course of each type of bank failuresis analyzed, including happen-develop-end. Then bring forward the common geologiccondition causing each type of bank failure. After field investigations and analysis onThree Gorges Reservoir and other three reservoirs (Ertan, Baozhusi and Gongzui),two ways to get forecasting parameters are brought forward, longitudinal analogism and horizontal analogism. This paper discusses these parameters of bank failureforecasting and its eigenvalue angles (θ,α,β), and takes statistic of parametersabout all kinds of soil and soft rock. After analysis, some regularity conclusions aredrew between the parameters and soil composes and its genesis mechanics orreservoir water dynamical conditions. If the structure of soil is closer, percentagecomposition of coarse grain is greater, or dynamic force of reservoir water is lower,then the eigenvalue angle of forecasting parameters is bigger.(3) The forecast and field practice let author to understand there is a reasonableway to forecast the zone of bank failure. The way is one means to one type of bankfailure. Then forecasting means to each type of bank failures is excogitated one byone, including Reservoir Bank Structure Method (RBSM), Three Segment ForecastMethod, a Multianalysis Regress Method that is developed by means of those physicsmodels tests, a zone-forecasting method of slope-type bank failure, a zone-forecastingmethod of rock sliding type bank failure, and a zone-forecasting method of flowingsoil type bank failure. Then integrate them to form a method system to forecast alltypes of bank failure. Assembly line works together. And design its rule, flow chart,and use step, as like a manual. Author use this integrated method system to forecastthe failure zone of many segment riverbanks in Three Gorges, Ertan, Baozhusi andGongzui Reservoir. The forecasting zone is reasonable and it is verified by fieldinvestigation and remote sensing image.(4) The evaluation to dangerous degree of bank failure is done in this paperfirstly. Include building a factor index system, choosing key factors, deciding impactintensity, building a model and means to calculate total impact value, etc. Thenevaluate three segments riverbank in Three Gorges Reservoir and the evaluationresults accord with our field investigation.(5) After summarizing all kinds of bank protection measures, including newprotection means, new technique and new protective material, and advance a type ofprotective measure. Then bring forward a suitable protection means to each type ofbank failures in mountain reservoir.(6) At last, main and important riverbanks in Three Gorges Reservoir areforecasted and evaluated by using this set of theory and method in this paper.