Study On Caracteristics Of Foudation Rock And Abutment Stability Of Sanhekou Arch Dam

The Sanhekou Hydropower project,which is one of the water diversion from HanRiver to Wei River Project，s two water sources,is regulation center of the diversionproject.The height of arch dam is145m,the total reservoir capacity is710millionm3,and the regulating storage is60million m3.The engineering geological conditions indam site is complex,there grew fault and joints,it has certain influence on the stabilityof the dam abutment.Available rock mass is metamorphosed sandstone, crystallinelimestone, and locally inclusion are marble, pegmatite vein and quartz vein,this kind ofrock mass is mainly for hard rock,but there is a big volatility in the longitudinal wavevelocity and mechanical parameters,also,according to current codes there are certaindeviation with the reality on the division of rock mass structure,rock mass weatheringand rock mass quality. The result of the division cannot truly reflect the engineeringgeological characteristics of the rock mass, directly influence the choice of thefoundation interface. So the important research topic in the project is accuratelyevaluating the characteristics of the foundation rock,safely and economically choosingthe location of the foundation interface,and according to the selected foundationinterface taking dam abutment stability analysis.In this paper, we take Sanhekou arch dam foundation rock as the researchobject,focus on studying the complex rock structure,weathered divided and rock massquality evaluation.Based on these researches,we have taken the choice of the foundationinterface and analyzed the stability of arch dam abutment.The main research results areas follows:(1) In this paper, we have carried out a large number of rock mass deformationtests,direct shear tests,wave velocity tests and drilling deformation tests etc in-situ tests,focused on research that the mechanical properties of the metamorphic sandstone andthe crystalline limestone,obtained a series of rock mass mechanics parameters,asloestablish the relationship between rock mass deformation modulus and wave velocity.(2) Through regional fracture characteristics,focal mechanism solutions,geostressmeasurement,finite element method numerical analysis,we have determined the area ofmaximum principal stress orientation for the NE;According to the numerical simulationresults of the dam site cross section stress field,the valley stress field is divided intofive,the basic characteristics of each stress points are obtained.(3) On the basis of the analysis of structure plane development features,we haveadopted the discontinuity spacing, intact coefficient, RQD etc tangible criteriacombinedwith Code forengineering geological invcstigation of water resources and hydropower, weput forward that Sanhekou Arch Dam Area rock mass structure taxonomy.According tothe classification results of the dam site rock mass structure,the middlestream dam lineof rock mass axis structure is better than the upstream and the downstream dam axis.(4) In accordance with the regulation of current codes and longitudinal wavevelocity,wave velocity ratio,intact coefficient tangible criteria, and combined with sitetunnel survey, rock mass weathering of abutment and foundation are divided. The right bank abutment rock mass weathering degree as a whole is higher than the left bank.(5) This paper has established Sanhekou dam foundation rock mass quality gradingstandards, which take deformation modulus,the longitudinal wave velocity,intactnessindex,rock mass shear strength index,rock mass structure type as representativeindicators.Using BQ grading standard,《Code for water resources and hydropowerengineering geological investigation》(2008)standards and grading standards of thisarticle,we have taken a quality classification for Sanhekou dam area rock mass, theclassification results show that,the grading standards of this article is more reasonable,economic.(6) To analyse the Sanhekou arch dam arch spandrels stress by multi archcantilevermethod and finite element method.we have Selected controlling index, established thequantitative criteria of Sanhekou arch dam foundation surface selection,ultimatelydetermined Sanhekou arch dam foundation surface boundaries.(7) By using three-dimensional numerical simulation analysis,we have analysedrock mass stress and deformation characteristics after the base surface rock excavation,andanalysed stress and deformation characteristics of dam abutment and the stability. Theresults show that the dam abutment rock as a whole is stable,under normal loadcondition of the dam body resistance.