Slope Stability Analysis Of The Right Bank Of The Reservoir Of Dagangshan Hydropower Project Under The Condition Of Water Level Rising

Stability of a slope is dependent on various factors and it can be obtained respective to different kind of situations the slope is subjected to. In this paper the stability of slope under the varying water level is taken into consideration. For the case study the right bank of the reservoir of Daganshan hydropower is taken as the study site. The site had suitable conditions as per the research requirements, it is subjected to the varying water level along a period of time. The variation in water level has a significant effect on the slope stability as we know that the water is a very important factor in such geotechnical problems. With the variation in external water level the water table also changes its level and thus affect the properties and behavior of slope. So here the behavior of the slope is intended to study by modelling and numerical analysis. The analysis is done by the use of SEEP/W and SLOPE/W, implementing Morgenstern-Price method for stability analysis. The slope stability is affected when the level of water changes. The change in Factor of Safety with the rise in water level is obtained. Two conditions of rise in water level is studied as fast and slow and the effect of different condition is studied. The variation of factor of safety with the height of water level for both situations is observed and thus the suitable condition is recognized.It is found out that, with the rise in water level, the water table also rises correspondingly and causing to change the properties of rock mass in the slope and its behavior to different situations and stresses. With the change in water table line the property like permeability changes, which is a significant property for the slope stability study and affects directly the strength of the rock mass. And also due to change in water table within the slope the situation of saturated and unsaturated portions in slope also changes and dealing with saturated and unsaturated parts at a time is a complex phenomenon. So it has to be considered as an important factor.From the result of the analysis we found that the pattern of changing the factor of safety with the elevation is similar for the cases of 30 days and 60 days(time taken to rise the water from lower to higher level), but there is the difference in values of factor of safety for same value of elevation so the speed of rise in water level also influences the impact on the stability. Hence, another case was studied, as 180 days taken to rise the water from lower to higher level. And again compared the result with the case of 30 days, and we obtained that there is a significant difference in factor of safety. From this comparison it was possible to point out the difference made by the speed of rise in water level more clearly than the previous comparison.From the graph for comparison of the two cases in the first case(30 days and 60 days) we obtained that both the cases are similar with little discrepancy but still we can see the difference indicating the difference in effect. And from the second comparison of two cases(30 days and 180 days) there was seen a significant difference in the pattern of variation in factor of safety with height of water level. So if the time difference between the two cases is more it may give different reading and it can be observed by further testing considering more cases of different times.