Comparing Study On The Total Stress Method And Effective Stress Method Of The Core Wall Dams

The earth dam's force condition for the construction period is so single that there is only self-gravity. After water impounding, stress and deformation of the soil-rock fill dam become more complicated than that in the construction period. The calculating methods mainly contain total stress method and effective stress method. Total stress method is more simplified and it is reasonable with the macroscopic viewpoint in taking account of total stress and surface force as a big element for core wall, but it is unreasonable for every element of core wall with the microscopic viewpoint. Effective stress method takes account of effective stress and seepage force, in addition, uplift force and equivalent force to the damping deformation of the dam shell and core wall for every element of dam under the saturation line is considered, so that effective stress method is more reasonable not only with the macroscopic viewpoint but with the microscopic viewpoint. The effective stress method should be suggested to be popularized in the calculation of stress and deformation of the soil-rock fill dam. This paper demonstrates the rationality of effective stress method in every ways by calculation and analysis on stress and deformation of two kinds of dam and two methods. It can be said that the effective stress method is more rational than total stress method. Because of the emphasis of this text is the two method's difference oncalculating algorithm research, it can not be considered of all influence factors on dam's stress and deformation , just as " wetting deformation" and " stress coupling". Undermentioned work has been done in the paper:1. 3D-FEM calculating program has been modified on the base of TDAD, which is compiled by Institute of Geotechnical Engineering of Hohai University;2.2-D seepage-calculation has been done on the two core-wall dams. Pore pressure is solved by seepage FEM method of every connected point on all kinds of storage level when it is stable seepage. We can get the equipotential lines and seepage lines. The average hydraulic gradient and seepage force of every element is solved also.3. Making use of 2-D seepage result and the modified TDAD program, two dam's stress and deformation are solved on the base of total stress method and effective stress method. The analysis and compares are done on two results. At last, it can be said that the result of effective stress method is more reasonable than total stress method.