The Study Of Foundation Deformation Control And Foundation Design Of Shapotou Water Control Project

Complex foundations such as sandy soil, clay, soft rock, sand and gravel overburden, complicated structure, and soft interlayer etc. would inevitably be encountered in water resources and hydropower engineering. Adaptability and treatment of these foundations is a subject of great importance to be dealt with in engineering.Treatment of very soft rock in Shapotou Water Control Project is a grave subject to be dealt with in project construction. Partial soft rocks exist in dam foundations of some already built hydraulic projects in China, while the entire foundation of Shapotou Water Control Project is soft, which is mainly composed of mud rocks and shale rocks. These rocks are between soft rocks and hard soil in geologic characteristics. It has to bear great risk to construct large scale structures on this sort of foundation. Considering its particularity in characteristics, deformation control of soft rock foundation is a fundamental issue to guarantee structure safety. Besides site monitoring, some technical measures such as computer analysis are adapted to study and predict foundation deformation at present, however, the calculation theory and analysis method are still not mature enough. Excavation and unloading of soft rocks would lead to cracking in dam foundations because of its particular characteristics. Foundation would suffer uneven deformation after the structure is completed due to the effect of self-weight, water load etc., which would eventually compromise structure safety.Meanwhile mechanical characteristics of loaded rocks and unloaded rocks are essentially different, so correspondent parameters shall be taken according to the very loading and unloading conditions. By now rock mechanics of loaded rocks is studied profoundly, while that of unloaded rocks is not recognized deeply. In order to predict foundation deformation accurately and hence to improve the engineering measures for foundation deformation control, foundation deformation and stress condition are studied in this paper through establishing 3-D model for simulation and using computer numerical analysis on the basis of geologic parameters determined in tests, thus reliable references are obtained for project planning and design. Foundation optimization design and deformation control measures adopted on the basis of these references solved the problems faced in dam construction on very soft rocks, such as low bearing capacity, low deformation modulus, susceptibility of anti-sliding index of basal face rocks to construction.At present Shapotou Water Control Project is basically completed. Judging from data monitored, main structures and units in the project are working normally; horizontal displacement and settlement of the dam body are both less than 10mm, meeting requirements in standards and design. The design of this project accumulated engineering experience for constructing dams in soft rock area.