不同加载速率下全尾砂固结体抗拉力学特性研究

Study on Tensile Mechanical Properties of Full Tailings Consolidation under Different Loading Rates

利用全尾砂对矿山地表塌陷坑进行固结回填是解决尾矿堆存与地表塌陷两大矿山灾害行之有效的方法之一,如何保证回采过程中塌陷坑全尾砂固结体的稳定性至关重要。塌陷坑全尾砂固结体在回采过程中主要受到拉破坏,且与回采速率直接相关。基于此,本文选取程潮铁矿尾矿库尾砂,制作了不同配比(1∶4、1∶6、1∶8)和不同浓度(68%、72%、76%)的全尾砂固结体试样,开展了5种不同加载速率(0.01、0.02、0.05、0.1、0.2 k N/s)下的全尾砂固结体抗拉力学试验研究,探讨了不同加载速率下全尾砂固结体抗拉力学特性,揭示加载速率对全尾砂固结体抗拉破坏的影响机理。研究结果表明:固结体抗拉强度存在明显的加载速率效应,低浓度低配比的固结体抗拉强度受加载速率影响较大;固结体抗拉强度存在双临界加载速率现象,第一临界加载速率为0.05 k N/s,第二临界加载速率为0.1k N/s;低于第一临界加载速率时,加载速率对固结体原始孔隙存在压密效应,随着加载速率变大压密效应逐渐减弱,到第一临界加载速率时,压密效应消失,固结体抗拉强度最低,宏观裂纹最多,破坏最明显,最终耗弹比最大;高于第一临界加载速率时,加载速率对固结体孔隙发育存在抑制效应,随着加载速率变大抑制效应先增大后趋于稳定,达到第二临界加载速率时,固结体抗拉强度最大,宏观裂纹最少,峰值耗弹比最小。

It is one of the effective methods to solve the two major mine disasters of tailings stacking and surface collapse by consolidation backfilling with full tailings. It is very important to ensure the stability of full tailings consolidation in subsidence pit during mining. The full tailings consolidation of collapse pit is mainly damaged by tension in the mining process,which is directly related to the mining rate. Therefore,this paper selected tailings from Chengchao Iron Mine and made the full tailings consolidation samples with different proportions(1 ∶4,1 ∶6,1 ∶8) and different concentrations(68%,72%,76%). The tensile test research of full tailings consolidation under five different loading rates(0. 01,0. 02,0. 05,0. 1 and 0. 2 k N/s) were carried out to discuss the tensile properties of the total tailings consolidation under different loading rates and reveal the influence mechanism of loading rate on the tensile failure of the full tailings consolidation. The results show that the tensile strength of the full tailings consolidation has obvious loading rate effect,and the tensile strength of the consolidation with low concentration and low ratio is greatly affected by the loading rate. There are two critical loading rates for the tensile strength of the consolidation.The first critical loading rate is 0. 05 k N/s,and the second critical loading rate is 0. 1 k N/s. When the loading rate is lower than the first critical loading rate,the compaction effect on the original pores of the consolidation exists,and gradually weakens with the increase of the loading rate. When the first critical loading rate is reached,the compaction effect disappears,and the tensile strength of the consolidation is the lowest,the macroscopic cracks are the most,the damage is the most obvious,and the final ratio of dissipated energy to elastic strain energy is the largest. When the loading rate is higher than the first critical loading rate,the inhibition effect on the pore development of the consolidation exists,and the inhibition effect increases first and then stables with the increase of the loading rate. When the second critical loading rate is reached,the tensile strength of the consolidation is the maximum,the macroscopic crack is the least,and the peak ratio of dissipated energy to elastic strain energy is the minimum.