Study On Spatiotemporal Evolution Law Of The Stress At Island Coal Face With Fully Mechanized Top Coal Caving Mining In Jinqiao Coal Mine

In the coal mining process, skip-mining will ineviTablely result in the formation ofisland coal face. Setting the2321island coal face of Jinqiao mine as an example and thespatiotemporal evolution law of its stress field as a research object.The paper with the comprehensive research method consist of laboratory study,theoretical analysis, numerical simulation and field monitoring. Weak bursting liabilityis found in the coal mass and its roof at2321coal face.After the mining of the coal masson both sides of2321coal face, the resultant abutment stress field is a typicalsaddle-shaped stress field with twin peaks, and k, the stress concentration coefficient ofthe middle coal mass, is1.2. During studies on the spatiotemporal evolution law of thestress field when setting the coal face mining time and coal face mining position as theaxis respectively, we obtained the following results: abutment stress field in the initialmining stage is significantly lower than that in the middle stage and pre-mining stage;the most pronounced stress concentration occurs in areas surrounding roadwaychambers whose concentration coefficient is3.6, moreover, the failure scope of theplastic zones within these surround rocks has expanded. Through the spatiotemporalanalysis of areas with a bursting danger at2321island coal face, we found that Whenthe roadway chamber lies in middle and terminal mining position, it will bear theinfluences of the dynamic loading during periodic weighting. At this moment, thebursting posibility in these areas is much higher than that in other areas. Duringnumerical simulation, a least pronounced stress concentration is found in the coal pillarwith a5m width.2321island face on mine pressure test shows: the initial weightinginterval and the periodical weighting interval is65m,12m respectively. During theinitial weighting period, rib to rib converging velocity of the roadway on two sides ofthe coal face reaches30to36mm/d, and the roof subsidence velocity falls between11and17mm/d.Through the studies of the spatio-temporal evolution of the stress field in the islandmining face, this paper summarized the law of the stress field around the island miningface, which is of great theoretical and realistic significance to rock-burst prevention andcontrol in island mining face.