Study On The Movement Law Of Above Strata In Shallow Coal Seam With Soft Roof Caving Stope

Ili Mine No.4is a principal mine in Yining mine lot Its coal bed is characterized with shallow depth and soft rock stratum. In this paper, first mining face21105of Mine Mine No.4is taken as the object of research. On the basis of material collection, surrounding rocks in the quarry are classified and evaluated through theoretical analysis. According to the result of classification and evaluation and in combination with the research result of motion of overlying strata in the quarry, the overlying strata motion model is established for soft roof of coal bed with shalow depth. Based on theoretical analysis of the model, the basic motion law of the overlying strata is obtained. Moreover, such law is verified by physical experimentAccording to the research result, surrounding rock at face21105is classified as v. The li-thology is soft, with broken rocks easy to fall and collapse. The quarry is longitudinally divided as the loose structure zone, the arched girder structure zone and the fissure zone by the structure model of overlying strata established according to features of surrounding rocks and ordinary motion laws of overlying strata. The quarry is horizontally divided as the fracture development zone, the arch support zone and the secondary compaction zone. Basic motion parameters of the quarry were determined through theoretical calculation, such as pressure weighting step, immedia te roof and height of the quarry. Through repeated tests for lots of test blocks, similar ratio of soft rock strength was determined. Motion parameters and structure of overlying strata obtained through physical experiment are basically consistent with the theoretical analysis result According to the experiment, under shallow depth and loose conditions, the compressive streng-th of goaf filling is gentler than that of the quarry. Critical layer still exists in the overlying rock. Instabili-ty of critical layer is the reason for sudden compression. The compressive strength is violent Fr-acture directly stretches to the surface. This research is of guiding significance and reference va-lue for forecasting sudden compression and roof control of the quarry.