基于厚板理论下向进路充填假顶强度模型及应用
Strength model and its application of downward drift filling roof based on thick plate theory
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摘要: 充填假顶作为下向进路式采场的直接顶板,其稳定是该法成功应用的关键,以充填假顶所需强度为研究对象,通过分析下向进路式采矿法典型工艺特征,确定了假顶危险力学状态,并将其简化为四边简支的厚板模型,借助厚板理论符拉索夫基本解答,分析了充填假顶拉应力分布状态,据此建立了下向进路充填假顶强度模型。通过实测大屯锡矿下向进路式采场充填体上覆压力,以最大监测结果0.35 MPa作为基础计算参数,分析确定了假顶底部极限拉应力为0.23 MPa,为保障假顶稳定,考虑1.5的安全系数,设计假顶抗拉强度0.345 MPa。采用FLAC 3D构建了3-1矿体下向进路式采场物理模型,并模拟分析了充填假顶在设计强度参数条件下服务矿体回采过程中应力分布及稳定性状态,矿体回采至最后一分层,假顶拉应力分布于0.10~0.23 MPa,最大值为0.23 MPa,与理论分析结果一致,假顶服务至分层回采结束,未出现塑性破坏。根据模型计算结果与数值模拟分析结果,推荐满足强度指标的最优配比为废石:尾砂=8:2,水泥添加量210 kg/m3,质量分数85%,并指导完成大屯锡矿3-1矿体下向进路式采场11万m3充填实践,假顶服务矿体回采过程中未出现失稳引发安全事故,为矿体安全回采提供了强度保障,与矿山原设计相比,模型设计强度更加合理且经济,推荐的废石+铜渣尾砂膏体配比较矿山原充填配比节约32.30元/m3,累计节约充填成本355.30万元。Abstract: As the direct roof of the stope using the downward drift cut and fill mining method,the stability of the artificial roof formed by backfill is the key to the successful application of the method. The strength required for filled artificial roof is taken as the research object,and the typical technological characteristics of the downward approach mining method are analyzed. Meanwhile,the dangerous mechanical state of artificial roof is determined and simplified to a thick plate model with four sides simply supported. Based on the Vlasov's basic solution to the thick plate theory,the tensile stress distribution of filled artificial roof is analyzed,and the strength model of filled artificial roof in downward drift is established. According to the measured value of overburden pressure of backfill body in the downward approach stope of the Datun tin mine,the ultimate tensile stress at the bottom of artificial roof is determined to be 0.23 MPa based on the maximum monitoring result of 0.35 MPa as the basic calculation parameter. In order to ensure the stability of the artificial roof,the tensile strength of the artificial roof is designed as 0.345 MPa,considering the safety factor of 1.5. The stope physical model of 3-1 ore body is constructed with FLAC3D,and the stress distribution and stability state of filled artificial roof in the process ofore body mining are simulated and analyzed under the condition of designed strength parameters. When the ore body is recovered to the last layer,the tensile stress of artificial roof is distributed between 0.10 MPa and 0.23 MPa,and the maximum value is 0.23 MPa,which is consistent with the theoretical analysis results that no plastic damage is found until the end of delamination stoping. With the results of model calculation and numerical simulation analysis,the optimal ratio satisfying the strength index is recommended as waste rock:tailings=8:2, cement content 210 kg/m3, mass concentration 85%, whch guides the completion of 110 000 m3 filling practice in the downward approach stope of 3-1 ore body in the Datun Tin Mine. There is no safety accident caused by instability in this process,which provides strength guarantee for the safe mining of ore body. Compared with the original mine design,the strength of the model design is more reasonable and economical. The recommended ratio of waste rock and copper slag tailings paste save 32.30 yuan/m3 compared with the original one,and the cumulative saving of filling cost is 3 553 000 yuan.