School of Mines, China University of Mining and Technology State Key Laboratory of Coal Resources and Safe
Mining Changping Coal Industry Co., Ltd., Jincheng Coal Group

为分析极松软煤层注水防止片帮的效果,研究了极松软煤层注水后抗剪强度的变化。基于非饱和土理论及直剪试验,采用极松软煤体重塑煤样,进行了一系列不同含水率及法向应力下不固结不排水直剪试验的研究,提出了以含水率为中心,以黏聚力和内摩擦角为主要指标的抗剪强度分析方法,采用试验和理论方法综合分析研究了含水率对极松软煤的抗剪强度的影响。研究结果表明:在低法向应力状态下,试样剪应力易发生软化现象,而在高法向应力状态下,试样易发生硬化现象;重塑煤样的黏聚力随含水率的增加先增大,达到最适含水率后(约17.64%),黏聚力随含水率的增加反而减小;含水率对重塑煤样的内摩擦角影响不明显,证实松软煤层注水防止片帮的工程控制技术是有效的。

In order to analyze the effects of preventing rib spalling by using water injection in extremely soft coal seam, the change of shear strength after water inj ection was carried out on extremely soft coal seam.Based on the theory of unsaturated soil theory and the direct shear tests, by using extremely soft coal samples whic h had been re-modelled, a series of direct shear tests with non consolidation and non drainage were performed under the conditions of different moisture contents and different normal stresses. The analysis method of shear strength was proposed in this paper, and the moisture content was used as the key index, the cohesion and int ernal friction angle were selected as the main indexes. The influences of moisture content on extremely soft coal seam were studied comprehensively combined with te sts and theoretical analysis.Results showed that in the condition of low normal stress, the shear strength of the sample tended to soften, and the sample was prone to h ardening in high stress state. Besides, the cohesion increased with the increasing of the moisture content, after that when the moisture content of the sample exceeded the optimum moisture content ( approximately 17.64%)，the cohesion began to decline and the moisture content possesses lttle effect on the internal friction angle. It i s proved that the engineering control technology of preventing rib spalling by using water injection in extremely soft coal seam is effective.

国家高技术研究发展计划(863计划)资助项目(2012AA062101)；教育部新世纪优秀人才支持计划资助项目(NCET-10-0770)；国家自然科学基金资助项目(51074164)；