Abstract: To control the stability of waste dump slopes with soft soil base during dumping and heightening process, the relationship between heightening rate and shear strength parameters of the soft soil is established, and a method for analyzing slope stability under different heightening rates is proposed. Based on a practical case, a series of quick shear tests for soft soil with different consolidation degrees is conducted. Results show that the internal friction angle gradually increases as a hyperbolic function with increasing degree of consolidation, while the cohesion remains almost constant. The evolution of consolidation degrees of soft soil layers under surcharge loading is studied using the finite element method and the hardening soil model. The relationships between consolidation duration, surcharge loading layer thickness, and strength parameters are established. Results indicate that a thicker soft soil layer has a lower internal friction angle under the same surcharge loading and consolidation duration. A lower surcharge loading results in a higher internal friction angle of the soft soil layer under the same consolidation duration. The slope failure mode changes from sliding along the base to sliding within the waste mass as the consolidation duration extends from 50 d to 100 d. Further extension of the consolidation duration has no effect on slope stability.

Key words: soft soil base, waste dump, heightening rate, consolidation degree, strength parameters, stability analysis