The Study Of Characteristics And Stablity Of Unloaded Rock Mass In The Right Dam Abutment Of Duobu Hydropower Station In Tibet Niyang River

In this paper, the study object is the unloading rock mass distributing in the right dam abutment of Duobu Hydropower Station in Tibet Niyang River. From the geological environment conditions of rock mass to the characteristics of unloding rock mass and from forming mechanism to stability evaluation of unloading rock mass,this is a basic condition to application of technical route, which has meaning to the study of the right of the abutment unloading rock mass distribution law, rock quality and stability, and which can provide a theoretical basis for the construction surface and slope excavation.In this paper the main conclusions and cognition are obtained as followed.1. With the qualitative and quantitative index for the unloading rock mass zone in the right dam abutment of Duobu Hydropower Station classified,the depth of strong unloading rock mass is range from0to30m, the depth of weak unloading rock mass is range from30to45m and the depth of deep unloading rock mass range from45to175m. Deep unloading problem exist in the right dam abutment.2. Combined with rock weathering, the quantitative indicators of rock mass quality (RQD), and the rock quality research show that strong unloading rock mass was strongly weathered shpe, the rock integrity is mostly range from broken or completeness broken, the rock mass structure is mainly fractured or chipped and the quality of rock slope is classified as â…£-â…¤. Weak unloading rock mass is weak weathered shape, the rock mass structure is mainly split block structure and sub-block structure and the quality of rock slope are classified as â…¢-â…£; Deep unloading rock is mainly composed of the fresh rock, this rock has a distinct zone belt feature and the structure is in a integrity state of rock mass. The unloading fracture rock mass always develop with rock fissures, localized weathering phenomenon can be found which structure is mainly split block and the quality classification of this kind of rock slope can be classified as â…¡-â…¢.3. In the dam site area with river-valley landforms, regional geological environmental conditions on the mechanism analysis of the abutment unloading rock mass shows that the abutment unloading rock mass is the formation of the birth of superficial born transformation product,in the formation of slope valley with slope release of stress on its original structure based on the original rock mass structure surface.Rock in the right bank of the river is at the beginning of the old channel cut formating, difference of nearly600m high steep slope, three facing empty conditions, and the slope rock mass in the rain and snow melting water infiltration, frozen, ice swells, ice erosion, earthquake and so on,which are the stress that long-term act on the slope under the steep structure surface happening out of the unloading, pulling a deformation, forming the strong and weak of unloading zones and deep concentration unloading belt.The superficial department of plasmodium is slip-cracking deformation deformated by the dumping and steep structure surface in the river in the rock.The cover of the late development of river right bank unloading rock bottom has certain press foot function, which is favorable in the internal limitation of rock mass deformation,slow and the direction of the overall stability and development.4. The right bank according to the abutment unloading rock mass and the dam site area through analysis of characteristics of the earthquake damage analysis and the slope surface ground investigation, it can be preliminary determined that the overall stability of right bank is stable. Furthermore, the factor of safety of unloading rock mass in right bank is testify can meet the design control standards by using limit equilibrium method and numerical analysis.