Reserch On Support Technology Of The Fully-mechanized Caving Headentry In Steeply Dipping Soft Thick Seam

The surrounding rock of fully-mechanized caving headentry in the steeply dipping soft thick seam has complex stress environment, collapsible top, support difficulties, which affect the mine safety production. It is signifcant that the study of support technology of fully-mechanized caving headentry in the steeply dipping soft thick seam is for enriching support technology of mining entry under complicated conditions.This paper is aimed at the 1123 fully-mechanized caving headentry in Chang Shanzi mine. Through field investigation, simulation study, theoretical analysis and field monitoring methods, the surrounding rock of the fully-mechanized coal headentry in the steeply dipping soft thick seam has been systematically studied. The results showed that:(1) Support loading and surrounding rock deformation and failure show asymmetric features. Entry instability is mainly characterized by roof instability. the form of entry instability have two kinds of types. One kind of instability is that induced rock instability comes from the lower side of the arch corner. Surrounding rock damage occurs from the lower side of the arch corner firstly. Failure mode is: producing fissures- bent- fracture-rotary – collapse. The final collapse process is divided into two phases that turning collapse and sinking collapse. Another instability is roof separation-induced instability, the instability mode is characterized by the following collapse.(2) It is instability induced point of surrounding rock structure at arch corner under the arc arch straight wall entry. Compared with the rectangular entry, the arc arch straight wall entry maximum shear decreases 46.5% on average and maximum bending moment decreases 56.5% on average at asymmetric loading conditions.(3) Separation warning value of shallow basis points in roof is determined by the relationship between it and overburden load, entry width, elastic modulus of surrounding rock, controlling range of the bolts. Separation warning value of deep basis points in roof is determined by the relationship between it and characteristic of anchor. According formulas and engineering background of steeply dipping soft thick seam of 1123 fully-mechanized caving face in Chang Shanzi mine, it is determined that entry roof separation warning value of shallow basis points is 60 mm and warning value of deep basis points is 140 mm.(4) Using the steeply dipping soft thick seam entry and "big, small structure theory" as the basis for steel ladder reinforced coordination support technology.Supporting parameters are: bolt row spacing 800 × 800 mm, anchor spacing 1200 mm, anchor row spacing 1600 mm.Site monitoring results show that: anchor force is greater than the bolt, bolt stress characteristics for roof is greater than lower side of wall larger than upper side of wall, the entry support parameters is suited to the 1123 fully-mechanized caving headentry, which has achieved good economic results.