The karst area in Zhejiang province is mainly mantled karst area,which makes karst collapse hidden and sudden.In recent years,there are a series of engineering problems in the northwest region of Zhejiang Province,which brings a great difficulty to the investigation,construction and operation management of the expressway.Therefore it's necessary to evaluate the possibility of karst collapse in the mantled karst area of the northwest of Zhejiang Province and the expressway projects,which can provide the basi...