Basic Research On Control Of Surrounding Rock In Big Section Safety Mining In Steep Seams

There are abundant of resources of steep seams in Urumqi coal mine in Xinjiang. Horizontal section top-coal caving has become a only mining method used in this mining area as a scientific method, and the past mining practice and theoretical research results indicate that increasing section height is a major mean to improve coal production.In the 11th five-year plan period, section height gradually will try to be increased to 30m in accordance with require of National Coal Mine Safety Supervision Bureau that the ratio of mining to letting is not more than 1:8 in top-coal caving face in Urumqi mining area.There are three main issues in so much of section height, whether or not the support can maintain good operating characteristics, the surrounding rock avoid the existence of large-scale rock with the danger of collapse, and how to ensure recovery rate, the core of which is reasonable range of section height to steep seams with different inclination, as well as further enhances controllability's way, namely the theoretical research of surrounding rock control on the basis of depth understanding to migration characteristics of surrounding rock. It is on the basis of contrasting, analyzing and summarizing previous researchs of steep seams, above issues are specifically studied by means of site monitoring, theoretical analysis, numerical and similar material simulation in this thesis.Based on the actual situation of complex occurrence conditions in steep seams, firstly, solid monitoring mode was established in top-coal caving face in field. All-round monitoring of strata behavior and migration laws of surrounding rocks are achieved in working face. Site measurement showed that the support bears pressure of different heights of caving completely destroyed along rock strike on different region and collapse range of basic roof is in gob area rear of coal wall. Although the working face has obvious period strata behavior along strike, working resistance of support did not increase along with increasing of mining depth and section height, which indicates that support will be protected by overhead (coal body and gob field) provisional structure along stata strike. Secondly, arch destruction of top-coal and replaced form of instability low arch by upper arch indicate that support will be protected by structure along tendency in top-coal body in top-coal caving trial Therefore, good operation properties of support are related to rock structures under conditions of big section mining.Further comparative similar simulation test of steep seams with typical angle showed that roof strata exists "unloading arch" structure, which makes it only bear strata action within the arch.Stability of roof was largely improved after roof was supported by collapse body which moves along region of the goaf and lies in "ladder" location to steep seams with larger inclinationBy means of small deflection theory of strata's plate destruction, reasonable high-value range was derived to steep seams with different angle. Therefore, there is basic requisite of avoiding large-scale rock collapse, and recovery ratio also can be guaranteed in working face. Mining 30m section steep seams whose inclation is more than 55°angle is feasible. In research of raising strata controllability, the test of large pile three-dimensional simulation which has total weighing of 18.6t shows characteristics of many times repeated subsidence, and collapse body possesses stepped distribution from bottom to roof. So the pit should be backfilled according this sequence. The action mechanism of filling body shows that it easily forms temporary stable structures above the working face, controls the movement of roof and bottom, and avoids the disaster from large-scale roof collapse.Genarally, this paper pointed out that selection of reasonable range of section height and forms of controlling surrounding rock on the basis of deeply understanding strata's damage characteristics.The issues have certain guiding significance for horizontal section top-coal caving in Urumqi coal mine, and reference significance to similar coal mine.