冻结施工井壁结构的合理设计

Rational Design of Shaft Lining Structure in Freezing Shaft Sinking

分析冻结井壁破坏的啜因,采用3种理论计算井壁负摩擦力,在井壁中性点位置设置压缩节点。

Cracking and faults on shaft lining occured in 17 main shafts after put into operation in Xuzhou and Huainan Coal Mining Areas. After the investigations the results show that the cracking ang faults mainly occured at mine shafts sunk by the freezing shaft sinking. The reasons of the cracking and faults are as followings, unproperly considerations in the design, problems in loading design of the shaft, unsuitable selection of the shaft lining structure,the vertical stress of the shaft not considered and examined, too small to the laterial effective cross section of the shaft lining and other factors not considered. The shaft lining were also failed by the consolidation of refilled soils, thawing of freezing soils, shrinkage of soil volume, compression subsidence, reduction of underground water level, reducing of floating force, compressed density of soil and downward negative friction of the shaft lining. The key point is to consider the shaft as a hollow pile. A friction effected on shaft due to ground subsidence is same to a negative friction effected on a surface of a pile. As for the structure of the shaft, the author proposed to have a compression joint at the upper section of a vertical centre of the shaft.When the asphalt/sand grout at the compression joint heavely loaded, the grout could yield through holes of the side steel plates and this will have a function of a reduction on compression. When a twin shaft lining with an saphalt/sand grout heavely lcaded and staggered to each other, the loading capacity of the shaft wall will not be reduced.