Consolidation Settlement Of "Raising Earth Dam From Upstream Deposited Mud" In South Mountain Area Of Ningxia

Reservoir with which has the multiple functions of storing runoff, flood detention, agriculture irrigation, urban and rural water supply, and etc. is one of the most important water engineering in south mountain area of Ningxia. However, those existing reservoirs have many potential questions comprising reservoir leakage, slope stability and reservoir sedimentation due to the low standard of reservoir construction and severe soil erosion of the loess plateau area. Further, that has become the problem to the safe operation and management of reservoirs locally.Although the method of "raising earth dam from upstream deposited mud" has been widely used to the project of risk elimination and reinforcement for dangerous reservoir in severe soil erosion area of the loess plateau in southern Ningxia, the systematic theoretical research and perfect technical scheme that guide the project construction are still lack. The dam foundation settlement both Datankou reservoir and Yshigou reservoir were calculated by using the piled load, Terzaghi theory of one-dimensional consolidation and numerical simulation of Plaxis software in this thesis. And their consolidation settlement characteristics were analyzed so as to serve the local actual construction.The main contents are as follows:(1) An overview including the background, significance, dam reinforcement measures of silt dam foundation were presented.(2) The concept of the piled load, Terzaghi theory of one-dimensional consolidation and numerical simulation method and their application conditions were described in detail.(3) The settlement of dam foundation that upstream deposited mud of Datankou reservoir and Yshigou reservoir were calculated by using three methods presented in this thesis and results were compared with the survey data.(4)The effective consolidation depth was discussed when the time factor was constant.The main conclusions have been given as follows:(1) An obvious effective is showed when add the sand cushion to referencing the dam foundation, so that the consolidation speed is fast and the construction period is shorten.(2) The results of dam foundation consolidation settlement of Datankou reservoir and Yashigouare reservoir that used above three methods show that the numerical simulation values are large, and Terzaghi theory of one-dimensional consolidation is simple. It is proposed that the piled load method can be conducted to determine the earth dam heightening load rating.(3) The secondary consolidation settlements are calculated by using numerical simulation method for Yashigouare reservoir, and the results are compared with survey data. The both datum are agreement basically.(4) The increasing and dissipation of excess pore water pressure is a regular variety with the piled load growth. During filling loaded, the pore water pressure increases; stop loading, the pore water pressure keep slowly dissipated. The drainage of soil on dam foundation is fast accelerate due to adding the sand cushion. Finally, the consolidation process will be finished when the pore water pressure is zero.(5) The affects depth of dam foundation consolidation degree can be determined by piled load method. The consolidation degree will slow growth when the fifth piled load is added without sand mat layer and the consolidation degree is unaffected basically; but adding sand cushion, the consolidation degree reaches extreme at the depth of 8 m, and then decrease gradually.