阶段空场嗣后充填胶结充填体力学强度模型研究

Study on mechanical strength model of cemented backfill pillar for subsequent stage filling of open stope

利用普氏平衡拱理论、侧帮楔体滑动理论,构建阶段空场嗣后胶结充填体向临空面滑动的失稳模型,在考虑采场长度、高度、宽度、倾角、围岩和充填体自身材料力学特征、充填体与围岩接触面特性和爆破震动等影响因素的基础上,推导出胶结充填体在极限平衡状态下所需单轴抗压强度理论公式。以某地下稀土矿山为工程实例,开展需求强度设计、影响因素分析和充填配比试验研究,研究结果表明:采场宽12.5 m、高50 m、长40 m和倾角68°时,考虑1.5的安全系数后,充填体设计需求强度1.55 MPa;需求强度随采场长度、高度增加而增大,随采场宽度、倾角增加而减小;采场高度、宽度、倾角和长度对需求强度影响依次降低;推荐灰砂比1∶6、质量浓度78%的充填料浆,28 d抗压强度1.52 MPa,塌落度26 cm,流动度210 mm,流动性能较好,泌水率9.4%,不离析满足生产要求。

PU’s equilibrium arch theory and sidewall wedge sliding theory are used to construct instability model of subsequent cemented filling body sliding to the free surface of open stope,and the theoretical formula of uniaxial compressive strength required for cemented backfill body under limit equilibrium state is derived based on influencing factors of stop length,height,width,inclination,self-mechanical properties of surrounding rock and backfill material,contact surface characteristics of backfill and surrounding rock and blasting.Taking for example an underground rare earth mine,the required strength is designed,the influencing factors are analyzed and the experimental study on the filling ratio is carried out,and the results show that the design strength of the filling body is 1.55 MPa when the mining stop is 12.5 m wide,50 m high,40 m long with 68° inclination,after considering the safety factor of 1.5,the required strength increases with the increase of stope length and height and decreases with the increase of stope width and inclination.The effect of stop height,width,inclination and length on required strength is reduced in turns.The cemented tailings backfill with 1 ∶ 6 cement-to-tailings ratio and 78% solid mass fraction is recommended,as its characteristics such as 28 d compressive strength( 1.52 MPa),slump( 26 cm),liquidity( 210 mm),better flow performance,bleeding rate( 9.4%) and non-segregating etc.can meet the requirements of mining operation.