ANALYSIS ON THE CAUSE OF VALLEY WIDTH SHRINKAGE OF AN ULTRA-HIGH ARCH DAM AND ITS INFLUENCE ON DAM SAFETY RISK

摘要

To better understand the phenomenon of valley width shrinkage after the impoundment of an ultra-high arch dam, the cause and mechanism of the narrowing of valley width on both sides of the high arch dam during the impoundment stage are studied and analyzed. The effect of reservoir water pressure and bedrock temperature drop on valley width narrowing is found to be limited; after impounding, the change in the seepage field of the bedrock mass disequilibrates the pre-impounding natural stress balance of the intra- and inter-laminar dislocation band. The triggering of creep deformation of the rock mass is thereby a major cause of valley width shrink. The results of actual monitoring and feedback simulation analysis also confirm this deduction. Ultimately, the effect of valley width shrink on the overall displacement and stress of the dam is further analyzed. Suggestions are proposed for the strengthening of tracking observation analysis in the later stage, dam area expansion, and the observation range of reservoir deformation.