Settlement And Stress Analysis Of Stilling Basin On Non-homogeneous Foundation

Structural stability of the stilling basin is an important subject in the design of hydraulic engineering. When a stilling basin is built on the uniform and sound rock-bed, the react of the foundation to constructions may not be very heavy. However, if the base rock is constituted with geo-materials of greatly varied mechanical features, it is very often that the non-uniformity of the foundation will lead to un-acceptable uneven settlements and high level internal stress of the basin's base plates, which will lead to the damage of the sealing devices in the structural joints and drainage facilities below the structure, and then develop abnormal uplift and fluctuating pressures to damage the whole stilling basin.The stilling basin in Baise hydraulic project is a typical case which is built on non-homogeneous foundation. In this project, the base rock's mechanical features such as elastic modulus, bearing capacities, low-level scour resistances and the depth of the rock's weathered layers vary greatly. To what extent will the special geological condition influence the stilling basin has become a very important subject to designers.In this paper, the settlement and stress features of Baise stilling basin is discussed in detail by 3D nonlinear finite element method. By using numerical method to simulate the key groove's nature of transmitting compression and shearing but not tension force, the basin's structural joints' distribution and key groove's setting is optimized, and an optimized joint setting plan is recommended. The research showed that: (1) Uneven settlements occurrs between the stilling basin's blocks because of the non-homogeneous foundation and the setting of key-groove could alleviate this kind of non-uniformity. However, key-groove's influence on the general level and distribution of the basin's settlements is rather limited. (2) The variation of the stilling basin's internal stress is related intimately to the under laying base rock's mechanical features. Non-homogeneous foundation will result in unevenly distributed high level stress in the basin plate. The reinforcement of these blocks should be determined on the stress result of FEM analysis (3) Key groove between the basin's side wall and the base plates ,and key groove between the basin's end sill and the base plates should not be set because of their enormous differences on weight and volume. The key grooves between the base blocks on the non-homogeneous rock bed should be reinforced for their dangerous shear stress arising from non-uniformity of the foundation. The above research results have been applied successfully to the design of Baise project.