The Study On Predicting Of Stability And The Forecasting Of Instability About Guobu-Bank Slope Of Laxiwa Hydropower On Yellow River

Guobu-bank slope is located in front of the right bank of Laxiwa Hydropower.After the sluice was closed in March1,2009, the Guobu-bank slope generated manynew failure phenomena, such as fracturing and dilapidations of the slope and rollingstones,and so on. The Guobu-bank slope continue deforming all the time and the daydeformation and accumulative deformation are large. Faulted structures、joints、thelong and big cracking and the sinking belt are developed fully in the Guobu-bankslope. The fracturing and cracking will highly probable become unstable rock masscombination, and they will affect the stability of the entire bank.It is a big safetyproblem for normal working of the Laxiwa Hydropower.This article takes lots of the-spot investigation and survey as base, from thegeological environment of Guobu-bank, based on detailed analysis of the bank of thestructure characteristics、the deformation characteristics and zoning characteristics,and the monitored material. Through the establishment of the geological model, doingmore detailed study by the methods of numerical simulation for the deformation andstability of Guobu-bank slope. On this basis,predicting the stability of Guobu-bankslope when the water level of the reservoir rise the normal water level on2452m.Atpresent,the progressivity deformation of the slope is very large,through the detailstudy of parts and ways of unstability for the forecasting.Learning from theengineering case studies of slope instability in the past, the article does a study offorecasting in the conditions of the progressivity deformation is strong.Concludingthis article, the main results and conclusions are the following:(1)Guobu-bank is a complex deformative product which is a geological processthrough a long period of geological time. slope body structure is more complex, A lot of loose broken rock and colluvial product each distribute in each mountain ridge,Thecrack in tension and groove are very development.The rock of the bank has a highdegree fragmenting Under the action of the structure, weathering and unloading. fromthe outside to the inside,the rock of bank can be divided into four belts such asfractured structure, chipped structure, massiveness-effracture structure and mosaicstructure.(2)After water storage beginning in March2009, the fracturing deformationbecome more serious and give evidence of the whole revival. From the number1channel in the downstream of Guobu-bank slope to the Huanghua-channel where is inthe upstream,the collapse,the phenomenon of collapse,crack and falling is veryobvious.At the same time, the local scarp is formation of crack and the fall zone.Thedeformation of platform is very strong, developing lots of falling recess, great pit andso on,, especially in the back of platform, developing a steep bank which extends bylinear edge,its distance of moving is over20meters.(3)The finding from the study of the deformation characteristics and monitorinformation:The deformation of Ⅲ area of Guobu-bank slope on the upstream sidewhere located in Shuanghuang ridge above2630m，and Ⅰarea on the downstreamside where located in Number1ridge above2770m are affected by Ⅱarea where isthe largest deformation area in Guobu-bank slope. The deformation degree, rateof Ⅰa rea and Ⅲ area are all less than Ⅱarea.Combining deformation damagecharacteristics and the RS results, in vertical, horizontal, Guobu-bank slope bothshowed obvious block characteristic.In effect failured under continuous deformation,the local block has a probability of disintegration and instability.(4)The numerical simulation method acquires the detailed analysis andevaluation about the stability in different storage stage of Guobu-bank slope. Thecalculation results show that the deformation in various impoundment stage areincreased to different extent, the variations of water level obviously increasedshore-slope deformation. Meanwhile, compared the results are acquired by thecalculations of various storage stage with practical monitoring results,they have agood fitting, also verified from extent computation model and the rationality of thescheme selection.At the same time, it also provides feasibility basis for predictingabout deformation and stability of Guobu-bank slope while rising the water level tonormal water stage under the condition of2452m.(5)Predicted results obtained, the water level in the back during uplift, thedeformation of Guobu-bank slope will be some serious, but with the slope of stress- strain to constantly change, in the water level is relatively stable,the deformation ofslope, showing a gradual leveling off or stable trend. The calculated results indicatethat K1point of slope platform whose total deformation will reach50m or so,whenthe water level rise up to2452m, the local deformation of the high elevation site willreach30m or more.(6)Through the analysis about predicting the stability of Guobu-bankslope,making a detail research of parts and ways of unstability. In the condition ofthe progressivity deformation of the slope is very strong,it makes a research forinstability forecast work of Guobu-bank slope.Then it puts forward the suitableforecasting model in the ways of middle short-term forecast and short imminentforecast for the instability forecast of Guobu-bank slope,it laids a foundation for theforecast later.