Measurement and engineering application of temperature field multiple-ring hole frozen wall in extra-thick clay strata

In China the thickness of freeze sinking through alluvial layer has exceeded 500 m and is close to 600 m. Multiple-ring hole freezing scheme and construction materials of the previous 10 mine shafts are collected. Data of the temperature field of the multiple-ring hole frozen wall of two super-thick layer freezing wells in Zhaogu No.1 Coal Mine are measured. The main reasons for rib spalling in shallow area, fully frozen in deep area, slow driving, and high expense of freezing in freezing shafts are that the frozen wall is too thick, the ring diameter of holes cannot adapt to each other, the middle-ring holes are excessive, and the inner-ring holes are too deep. The frozen soil extends more quickly to inside after the intersection of inner and middle ring holes, and adjustment capacity of the main frozen hole is poor during frozen period in middle ring. The method of frozen wall thickness and the matched hole-distributing method of three-ring hole freezing which makes the outside circle as the main frozen hole, the middle circle as the auxiliary hole and the inner hole as the prevention hole for wall caving are studied. The contradiction between the freezing, driving and lining is effectively solved, and technical and economic benefits have increased greatly after the proposed method is applied successfully in three frozen walls of 530 m extra-thick clay-strata in Zhaogu No. 2 Coal Mine.