Predicting ground pressure evolution and support crushing of fully mechanized top coal caving face based on zoning support mechanical model

In order to predict hydraulic support crushing accidents in fully mechanized top coal caving face,based on the zoning support mechanical model of main roof,the calculation method of roof ground pressure evolution and support crushing criterion in fully mechanized top coal caving face are put forward. And the corresponding calculation code is developed,and the evolution laws of roof ground pressure in fully mechanized top coal caving face with large mining height is researched. The results include that:①=1\\*GB3 There are four evolution stages of the roof ground pressure in fully mechanized top coal caving face,including slow resistanceincreasing stage,roof fracturing stage,fast resistanceincreasing stage and instability stage. ② In slow resistanceincreasing stage,the roof settlement is small,and the support resistance slowly increases with unremarkable roof pressure. In fast resistanceincreasing stage,the roof settlement is large,and the support resistance quickly increases with remarkable roof pressure. ③ The roof fracturing stage is a transition from slow resistanceincreasing stage to fast resistanceincreasing stage. When the main roof fractures in the front of the roof coal wall,the boundary condition of main roof changes. The roof pressure is intensive,and the increasing resistance of the support is large. Those easily lead to opening of the safety valve. If the roof settlement exceeds the allowable value of movable column of hydraulic support,large area support crushing accident will appear. ④ When the working face arrives at the fracture line position,due to the large mining height,the roof loses stability. If the load of overburden on the support exceeds the rated working resistance,the safety valve is opened. Which is easy to cause large area support crushing accidents. ⑤ The design principles of the rated working resistance and initial force of the support are:In slow resistanceincreasing and fast resistanceincreasing stages,the loads on the support could not exceed the rated working resistance of the support;In the roof fracturing stage,the support should have sufficient allowable compressible space for pressure relief;In the instability stage,the support should have sufficient rated working resistance to bear the load of collapse overburden. ⑥ ZF15000/26/42 of fourcolumn shielding support with an initial support force of 10 800 kN is adopted in 6105-2 working face of the fully mechanized top coal caving of Suancigou coal mine. The rated working resistance force of the support is insufficient,and largearea support crushing accidents easily appear. This research provides a new idea for the prediction of roof ground pressure evolution and support crushing accidents,the support selection,design of initial support force and roof accidents prevention in mine.