Study On The Variation Of Uplift Pressure And Leakage Law Of Masonry Gravity Dam Of Huanglongdai Resevior

The masonry gravity dam of huanglongdai reservoir in guangzhou was built with a height of 61.3 m in 1970s,which is a typical mediun-high gravity dam construsted with masonry in early stage.Its safety has been highly valued by the water conservancy department through a long-time monitoring and secondary sagety assessment.In this paper,based on safety analysis and assessment,the variation of uplift pressure at dam foundation and leakage law are studied.The specific works includes field investigation,data collection,statistical analysis of uplift pressure,analysis of leakage law,finite element analysis and reinforcement measures,as follows.（1）The varaiation of uplift pressure.The statistical model of uplift pressure at dam foundation is estabilished and the monitoring index is obtained.The uplift pressure at measuring point sy7 was in an abnormal state,conformed with the characteristics of higher value than standard value,and the water level of uplift pressure fall behind that of upstream reservior for 1-4 days.Considering engineering geology and precipitation from drainage holes,it is concluded that abnomal uplift pressure is mainly caused by strong permeable cracks at dam foundation and underachieving grouting and draining.（2）The law and reason of dam leakage.The leakage mainly determined by the reservoir water level and strongly correlated with the highest reservoir water leel.The reason for the leakage of dam is the low local compactness and large gap of masonry dam.The main cause of leakage at dam foundation is strong permeable crack in the shallow bedrock of 166-170 m on the abutment of two banks.However,the overall dam leakage is small and the seepage prevention is in a normal range.（3）Anti-seepage effect of anti-seepage curtain.For huanglongdai reservoir dam,when the anti-seepage curtain depth reaches 20 m and the permeability coefficient of curtain is less than5.0×10^-7cm/s,the curtain play a good anti-seepage role and consistes with the engineering practice.（4）Evalation of multiple reinforcement treatment effects.During the operation,uplift pressure drainage hole,local renforcement consolidation grouting and curtain grouting are gradually adopted to reduce the uplift pressure and leakage.However,the leakage after reinforcement along with year is still random fluctuant instead of decreasing with year obviously.The measures of grouting an drainage have inapparent effects on reducing leakage.In the future,the leakage of 166-170 m elevation area should been pay close attention and if necessary,reinforced again.