JinpingIIhydropowerstationisanimportantcascadestationof Ya-Long RiverinSichuan province. TheregionofhydropowerstationistypicalV-shapedrivervalleymorphology. Tectonicmovement,includingIndo-Chineseepochmovement,Yanshanmovementand Himalayan movement, madetheregionpreserveprodigioushorizontaltectonicstress. But,the corrosion of Ya-Longriverleadstofiguration ofthe "V" shaped valley andrelease oftectonic stress.

To understand the effect of inter dynamical geological process and outer dynamical geological process to current geo stress of Jinping, a new nonlinear back analysis method of initial geo stress ispresented,whichintegratesthestratadenudationsimulation,numericalelasto-plastic calculation and neural networkinversion. The methodtakesthe geo structure order processinto accountbyelasto-plasticcalculationandsimulatesthestratadenudationprocessbysurface excavation. The method includes several steps. Firstly, a numerical model including immemorial plantationsurfaceisbuildupinalargearea. Secondly,thegivendisplacementboundary conditions are applied on the model in order of tectonic movement time and the balance is gained byelasto-plasticcalculation. Thirdly,surfaceexcavationiscarriedouttosimulatethestratum corrosion, the "V" shaped valley and the current geo stress field of Jinping II hydropower station region is obtained by several excavation calculation. In the method, the "the given displacement boundaryconditions"isrecognizedthroughnonlinear mappingfrom measuredgeo-stress with artificial neural net.


As we all know, the current geo stress in stratum is the result of complicatedinter dynamical geological process andouterdynamicalgeologicalprocess(McKinnon, 2001; Hudson, 2003). On one hand,theinter dynamical geologicalprocess,includingtheIndosinianorogeny, Himalaya movement, and so on,leadsto preservation of great horizontal tectonic stress in rock. On the other hand, the outer dynamical geological process, including stratum abrasionandrivererosion,leadstothereleaseand adjustment of tectonic stress (Obara, 2000; Mello, 2002). Therefore,areasonablestudyofgeostressshould consider the history of tectonic evolvement.

JinpingII hydropowerstationis animportant cascade stationofYa-LongRiverinSichuanprovince. The hydropowerstationregionistypicalV-shapedriver valley morphology with high grand mountainsand deep gorges(Figure 1). Thein-situstressmeasurement indicatesthatthe geo stressfieldisaffectednot only by immemorial tectogenesis but also by exogenic geological processes (Zhong, 2002).

(Figure in full paper)

To understand the effect of inter dynamical geological processandouter dynamicalgeologicalprocesstoform the curr

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