Abstract: To investigate stability characteristics of landfill cover system with different slope length types (i.e. finite length or infinite length), and different interface types (i.e.weak interface or strong interface), the failure mode of landfill cover with different slope length types and different interface types at limit state is obtained by model test. Based on the test results, an allowable landfill cover failure mode and the velocity field are established. Meanwhile, the consistent stability analysis model is obtained by using the upper-bound solution theory, which agrees well with those from the model tests. The stability of new environmental protection technology of ecological sludge evapotranspiration technology (EST) is studied by this model. The results show that: the upper part of the failure plane is straight, which is under the carrying soil and parallel with original slope surface; but the lower part is approximate straight line connected with the upper-part with a angle. With decreasing the length of slope, the safety factor of cover system will be increased; but the relation between thickness and safety factor of cover system is to be related to interface types. The stability of cover system is mainly controlled by shear strength of interface; and it is not obvious to increasing the safety factor of cover system by increasing substrate shear strength; it is better to increase the safety factor of cover system by increasing the cohesion of interface than increased the internal frictional angle of interface.

Key words: landfill, cover system, model test, stability, upper-bound solution theory, ecological sludge evapotranspiration technology