加载速率对弱胶结砂岩劈裂特性的影响研究

Effect of loading rate on splitting characteristics of weakly cemented sandstone

为研究加载速率对弱胶结砂岩劈裂特性的影响,对0.01~1 mm/min六级加载速率下的弱胶结砂岩进行巴西劈裂试验,并在试验过程中采用声发射监测系统对岩样破裂过程中声发射信号进行同步采集,采用数字图像相关法(DIC)同步获取岩样的全场应变演化。结果表明:弱胶结砂岩的抗拉强度与加载速率密切相关,且试样的抗拉强度与加载速率呈正相关的关系,采用多项式拟合能够很好地表征其随加载速率的变化规律;弱胶结砂岩的声发射计数曲线可划分为压密、弹性、破坏三个阶段,并且声发射计数的激增点与岩样的峰值应力点一致,大量的声发射事件发生在岩样破坏的瞬间,声发射事件分布与宏观破坏结果相对应,并且随着加载速率的增加事件数逐渐减少;加载速率的变化对弱胶结砂岩劈裂过程中的应变演化没有较大影响,不同速率下岩样应变场演化规律基本相同。本文的研究成果可以为弱胶结软岩巷道变形破坏分析提供参考。

In order to study the influence of loading rate on the splitting characteristics of weakly consolidated sandstone,the Brazilian splitting test is carried out on weakly consolidated sandstone with six loading rates of 0.01-1 mm/min,and the acoustic emission monitoring system is used to collect the acoustic emission signals during the fracture process of rock samples.Digital image correlation(DIC)method is used to obtain the strain evolution of rock samples simultaneously.The results show that the tensile strength of weakly consolidated sandstone is closely related to the loading rate,and there is a positive correlation between the tensile strength and the loading rate.The polynomial fitting can well characterize the variation of the tensile strength with the loading rate.Weak cementation sandstone of acoustic emission counts curve can be divided into pressure,elastic,destroying three phases,and a surge of acoustic emission counts point is consistent with the sample of peak stress points,a large number of acoustic emission events at the instant of the rock s damage,distribution of acoustic emission events and macro damage results,corresponding reduced gradually,and with the increase of loading rate events;the variation of loading rate has no great influence on the strain evolution of weakly consolidated sandstone during the splitting process,and the evolution law of strain field of rock samples under different rates is basically the same.The research results of this paper can provide reference for the deformation and failure analysis of weakly cemented soft rock roadway.