| This paper prepares for 11211 Zhengmei group Baiping Coal Mine Working Face in "Three Soft" coal seam coal of different water cut rate of molding coal sample as the research object, using the method combined with theoretical analysis, experimental research and field experiment to study stress and strain rule of different moisture content of molding coal sample and the rule of water rate impact molding coal sample meso structure characteristics, combined with raw coal and briquette coal sample fine microstructure and properties, the paper also analysis the rule of pieces of the internal particle migration specimens under the condition of three to stress test, finally by the field experiment results to confirm the reasonable coal seam water injection rate, which helps to improve the cohesion of coal body and reduce coal wall caving.The paper contents and conclusions drawn in this paper mainly include the following aspects:(1)The paper studys the precess of preparing molding coal sample mould. Through theoretical analysis, laboratory experiments and combined with previous preparation of molding coal sample experience, analyzed and summarized the preparation with different water rate molding coal sample molding pressure and molding time, the speed of the remolding.(2) By the experiment with MTS815.2 on the preparation of different water content in molding coal sample for single axis three complete stress-strain to study different water content on molding coal sample from loading to failure process variation of stress strain curves show that with the increase of moisture content, the post peak curve by plastic soft gradually to strengthen the plastic transition; fully considering the influence of confining pressure and moisture of coal. The paper also analysizes different water content under the condition of peak strength and confining pressure value fits a linear relationship between peak strength and confining pressure, and then calculated the briquette of different water ratio of internal friction angle and cohesion, fitting water content and internal friction curves angle and cohesion, which combined with the contact mechanics and liquid bridge theory to explain the cause of reasonable water increased the pulverized coal particles cohesion.(3)Comparative studying raw coal samples and shaped coal samples with different magnification of macroscopic structure, concluding that the macroscopic structure model of specimen; Combining with MTS815.2 data acquisition rules, according boosting full stress-strain curve, finding that with the increase of the curve magnification, the curve is changed from smooth to the discount; Combining with stress-strain curve and the macroscopic structure characteristics, and based on the theory of granular material mechanics analysis macroscopic particle migration rotation law of molding coal sample in loading process, and then explaining the full stress-strain curve, building relationship of macroscopic mechanics and mesoscopic mechanics.(4)In Zheng Mei Ji Tuan Bai Ping coal mine 11211 face upward and slot is deep hole of coal seam water injection showed that cohesion increased by 29.69%, internal friction angle decreased by 28.5%, the working face of coal wall spalling reduce from 49.5%- 49.5% range rib spalling to 8% ~ 31% range rib spalling, the depth reduce from 290 mm ~ 610 mm to 85 mm ~280 mm. |
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