The sidewall fracture of the shaft and the creep of concrete

In coal mines of Huang Huai region,the sidewall fracture is basically induced by axial additional loading downwards to the shaft,which is brought about by negative skin friction outside of the sidewall due to the drain consolidation of the aquifer at the bottom of the deep loose overburden layer and the settlement of the strata.The fracture begins from the flake of the sidewall concrete.With the axial loading increasing,the perpendicular closely spaced sand slurry fissures in the concrete of the shaft growth,the aggregates of the concrete are peeled off as a result of inter faced fissures,and then the concrete dilate to the inner of the shaft and the deformation shows the phenomena of "pseudo plastic".Besides these properties above,the fracture of the sidewall results from axial high compressive stress for a long time in view of the negative skin friction and the process of loading increasing.