Abstract:

Based on field investigation and lab tests, the ground collapse characteristics of mined-out area along Qingdao-Lanzhou express highway has been studied. The formation mechanism of the ground collapse has been discussed further. The research shows that the ground collapse represents collapse hole, earth fissure and sinking basin,and the distributing rule is not good. The ground collapse is obviously hysteretic comparing with coal seam excavate. The main reason of ground collapse is that coal seams are buried low,and the two zones are through the earth’s surface. Because the loose loess overlaying coal seam has unique structure and certain structural strength, it would not break down immediately. The tensile crack would form firstly along loess vertical joints in loose bed, and then the crack would develop corrosion and erosion under the condition of ground water current action, and the tensile crack would extend to form collapse hole finally.

Key words: mined-out area, ground collapse, formation mechanism, loess