Abstract: A new risk assessment method for karst ground collapse is presented in order to quickly and accurately assess the risk of surface subsidence in covered karst area. Firstly, the main factors were identified by mechanism analysis of karst ground collapse, and secondly the weight back analysis method was used to obtain the weights of main factors of karst ground collapse based on 100 typical engineering examples in Tangshan city. As a result, a score sheet of comprehensive hazard evaluation of karst ground collapse was established. Studies have shown that the weights of selected five main factors are as follows: karst development degree- 0.338, water-resisting capacity of impermeable layer-0.255, overburden thickness-0.186, depth of bedrock water level-0.174, and distance from the fault-0.047. The karst ground collapse hazard evaluation results of the 100 project examples based on the proposed score sheet have shown that the correct rate is 99% ,which can prove that the proposed method has a good performance in feasibility and effectiveness. In addition, the proposed method has the advantage of easy access of evaluation factors and high efficiency, and therefore it is worth popularizing and applying.

Key words: karst, ground collapse, risk assessment, weight, back analysis