A concrete diaphragm wall is always used to prevent the seepage through the deep alluvium deposit for conerete face rockfill dam built on it. The tensile stress distributed the zones near by the both riversides and the top zone of the concrete diaphragm wall are usually big and sometimes are even larger than the tensile strength of concrete

that usually leads to cracking of diaphragm wall which decreases the safety of diaphragm wall and dam. In order to solve this complex problem

a new idea— arc type diaphragm wall is suggested. Comparison between the stress-deformation behavior of arc type diaphragm wall and that of plane type diaphragm wall has been made by using three-dimensional finite element method numerical analysis. The calculation result shows that the tensile stress of arc type diaphragm wall is much less than that of plane type diaphragm wall although the compression stress of arc type diaphragm wall is a little larger. Since the tensile strength of concrete is only less than 10 percent of compression strength

tensile stress is the main control factor of diaphragm wall. So the arc type diaphragm wall is probably reasonable especially for concrete face rockfill dam built on a deep alluvium deposit.