加载速率对分层充填体强度特性的影响

随着阶段嗣后充填采矿法的广泛应用，相邻矿体的开采扰动必然会对分层充填体的力学性能产生影响。为了研究不同加载速率对分层充填体强度特性和破坏模式的影响，分别对养护3、7、28天的分层充填体进行了0.2 、0.5、1.0、1.5、2.0 mm/min 5种加载速率下的单轴压缩试验，根据不同加载速率的单轴抗压强度试验结果，分析了不同养护龄期的分层充填体强度及破坏模式与加载速率之间的关系并建立了回归方程。试验结果表明:不同加载速率下分层充填体的应力应变曲线与完整充填体类似。养护龄期3天时，分层充填体的单轴抗压强度随加载速率的增加而逐渐减小，养护龄期7、28天时，存在临界加载速率现象。在临界加载速率范围内，提高加载速率可以限制初始缺陷的发育，达到临界加载速率后，加载速率将会促进分层结构面的分离、错动及原始缺陷的扩展延伸，抗压强度降低。分层充填体的破坏模式随加载速率变化，在临界加载速率时破坏模式有明显转变，随着加载速率的增加，养护3天时，分层充填体的破坏模式由拉伸剪切混合破坏变为拉伸破坏。养护7、28天时，当达到临界加载速率时破坏模式转变共轭剪切破坏，中间层破坏严重且与上下两层产生明显分离、错动。本研究通过室内试验得到临界加载速率，为研究分层充填体的强度特性提供了重要的研究依据。

Effect of Loading Rate on Strength Characteristics of Layered Backfill

With the wide application of stage-subsequent filling mining method, the mining disturbance of adjacent orebody will inevitably affect the mechanical properties of layered backfill. In order to study the effects of different loading rates on the strength characteristics and failure modes of layered backfills, uniaxial compression tests were carried out at five loading rates of 0.2, 0.5, 1.0, 1.5 and 2.0 mm/min for layered backfills cured for 3, 7 and 28 days respectively,according to the results of uniaxial compressive strength tests at different loading rates, the relationship between the strength and failure modes of layered backfill at different curing ages and loading rates was analyzed, and the regression equation was established.The test results show that the stress-strain curve of layered backfill is similar to that of complete filling body under different loading rates. The uniaxial compressive strength of layered backfill decreases gradually with the increase of loading rate at the curing age of 3 days, and the critical loading rate exists at the curing age of 7 and 28 days. In the critical loading rate range, increasing the loading rate can limit the development of initial defects. When the critical loading rate is reached, the loading rate will promote the separation and dislocation of layered structural plane and the extension of original defects, and reduce the compressive strength. The failure mode of layered backfills changes with loading rate, and obviously changes at critical loading rate. With the increase of loading rate, the failure mode of layered backfills changes from tensile shear mixed failure to tensile failure after curing for 3 days. When loading rate is higher, the failure is serious and large pieces fall off. After curing for 7 and 28 days, when the critical loading rate is reached, the failure mode changes to conjugate shear failure, and the middle layer is seriously damaged, which is obviously separated and dislocated from the upper and lower layers. In this study, the critical loading rate is obtained through laboratory tests, which will provide an important research basis for studying the strength characteristics of layered backfill.