Time-domain characteristics of overlying strata failure under condition of longwall ascending mining

Ascending mining is one of the most effective ways to solve problems of water inrush, gas outburst and rock burst in coal seams mining. In order to reveal the law of motion and spatiotemporal relationship of overlaying strata, field measurement has been done in a mine. Long distance drillings were constructed from 4# coal seam to 6# coal seam at several certain typical positions, and movement and failure law of overlying strata after mining was analyzed by drilling video and observing the fluid leakage. Besides, we also analyzed the spatiotemporal development law of overlying strata failure with different mining heights and time intervals in the lower coal seam. The results show that: ascending mining is significantly affected by time-domain characteristics of overlaying strata failure after the lower coal seam's mining, height equations of caving zone and fractured zone are given in this paper, and the feasibility of ascending mining was compartmentalized concretely according to the spatiotemporal relationship. Research methods and conclusions of this paper have certain referential significance for the study of ascending mining, mining under water, mining under building, mining under railway and stress-relief mining.

Study on ascending mining roadway layout of close distance coal seams in deep mine

To solve the problems appeared in mining process of No.2 seam, the ascending stress-releasing mining method was adopted. Studying on the reasonable layout of actual mining roadway in upper coal seams is the precondition of successful ascending mining. By using ＂device of leak measuring by blocking up double ends＂, it detected the height of overburden water flowing fractured zone originated from sub-coal seams mining. Thus it proved that the actual mining roadway of No.2 upper ascending seam was located in the smooth sagging zone. On the basis of analyzing the stress-releasing effect of sub-coal seams mining to upper coal seams by using RFPA software, it analyzed the stability of up-face coal seams and the reasonable location of starting cut in up-face coal seams. It also analyzed the reasonable gateway location in upper coal seams, which ensured the crossheading in upper coal seams out of the effect of sub-coal work face mining by using theory of underground pressure. Meanwhile, the reasonable pillars dimensions in upper coal seams by building the structure mechanics model of stope were researched. It can make the roadway driven along next goaf to be located in low stress zone, and be beneficial to keeping roads stable owing to less stress of surrounding rock. Finally, it tested the rationality of the layout method of roads in upper coal seams by engineering field measurement in 3221 working face.

Analysis on air-leakage law of goal in condition of ascending mining for top-coal caving

Using the Jisan Coalmine's top-coal caving for the 3down coal seam with ascending mining as the project background, the air-leakage characteristics of the goaf wasanalyzed. Through data fitting of the in situ observation, the models of gas seepage, diffusion and air-leakage in the goaf were established in ascending mining. The ComputationFluid Dynamics software Fluent was used to simulate the air-leakage law of the goaf. Theresults of the numerical simulation provide a basis for the use of the technology of ventilation and fire prevention in the working face of an ascending mining, which ensures thesafety in production in the working face of the top-coal caving for 3_down coal seam in theJisan Coalmine.