Study On Caving Regularity Of Basic Roof In Wall Mining Along Strike Of Steep Coal Seam

For a long time,steep coal seam is that the dip of coal seam is greater than45°in China.Because of the serious distribution inhomogeneity of coal seam resources reserves,steep coal seam play an important roal in coal reserves and output in remote and south lack coal areas,for example Qinghai,Xinjiang,Gansu,Sichuang,Hainan,Guizhou,Fujian,etc.Steep coal seam has an important role for the economic development of these provinces.It has formed considerable scale to mining steep coal seam in southwest areas, steep coal seam is main coal seam in many mining areas.Its reserves is about70%of southwest region coal total,and its yield is about50%of all production.In allusion to actual and concrete existence of steep coal seam, some basic researches are implemented to caving regularity of basic roof in mining steep coal seam,using the bonded method of theory analysis and similarity simulation experiment methods in this thesis,and we acquire some beneficial conclusions.(1)Analyzed the actual existence state and stress of basic roof in space,and established an thin plate model of the basic roof in accordance with Elastic mechanics thin plate theory.The basic roof before it is firstly disrupted is regarded as an thin plate model that it’s four sides are fixed,and the one when it is periodically disrupted is regarded as an thin plate model that it’s three sides are fixed but the other is simple supported.Roof strata of steep coal seam is considered as an homogeneous, continuous and isotropic material.Through calculation and analysis,the breakage of basic roof is tension crack failure of the leading of buckling instability.The first and cycle characteristics of basic roof are all tension crack failure that its crack open is toward the goaf along the horizontal blanking level of tendency,meanwhile,the tension crack failure of basic roof that its crack open is back on to the goaf is also occured about the upper and lower fixed sides vicinity.The formulas of basic roof first and cycle caving interval are given.The basic standards of basic roof first and cycle caving flexion and breakage is established.(2) Similarity simulation experiment is carried out on the basis of the steep coal seam of Lu-ning-da-han-gou coal mine,Lu’an group as the prototype.Tre characteristics of basic roof is tension crack failure like plate when roof is thir plate.Rock plate firstly bends along the line what parallel to the upper and lowe fixed sides at middle-upper part of rock plate,soon forms minimal cracks. The minimal cracks gradually expan,rock plate finally breaks fluctuation two part toward the goaf,the breakage site open direction is toward the goaf,and the cracks that their open is back on to the goaf is also occured about the upper and lower fixed sides vicinity.It is verified that the correctness of obtained basic roo breakage characteristics by the method of theory analysis.And obtained that the breakage of basic roof do not reach caol face,but keep some distance.The touch between fell down strata and floor is more scarce like ">".The conclusions of obtained basic roof breakage characteristics respectively by theory analysis and similar material model test methods was contrasted.They are similar,But the breakage site has some difference because of the diversity on treating the prototype.(3)According to similarity simulation experiment,with each coal seam mined,many uncompacted finished stopes is formed in unmined coal seam upper,and they are got many repeated mining influence.The ability of the rock mass stability is reduced greatly,upper rock mass occurs entirety instability in a time,it will cause great difficulties to unmined coal seams.