不同含水状态凝灰岩损伤演化试验研究

Experimental study on damage evolution of tuff under different moisture states

为探究矿井巷道、隧道开挖过程中岩石含水状态对围岩变形稳定的影响,开展干燥、自然及饱水状态下凝灰岩三轴压缩试验。基于三维数字图像相关技术研究了含水状态与岩石全应力-应变曲线、表面变形场、变形局部化及损伤演化特征的对应关系。结果表明:从干燥到饱水状态试件各特征应力阈值显著降低,弹性模量与泊松比显著降低;破坏阶段全应力-应变曲线跌落趋势趋于平缓,软化特征明显。从干燥到饱水状态试件表面变形非均匀程度增加,变形局部化现象提前启动,变形局部化带宽度明显增加。从干燥到饱水状态试件局部化轴向、径向启动应力水平显著降低,且与含水率保持良好的线性关系。基于变形场数据统计分析提出表征岩石表面损伤大小的损伤因子,干燥及自然状态损伤因子呈突发式增长现象,而饱水状态下呈缓慢增长趋势;不同含水状态损伤因子演化曲线均存在"突变点",统计结果表明随着含水率增加,损伤突变点对应应力水平值显著降低。

In order to explore the influence of rock moisture content on deformation and stability of surrounding rockS during excavation in mine roadways and tunnels, triaxial compression tests of Tuff under dry, air-dried, and wet conditions, respectively, were carried out. Based on three-dimensional digital image correlation technology, corresponding relationship between moisture content and full stress-strain curve, surface deformation field, deformation localization, and damage evolution characteristics were studied. The results have shown that, characteristic stress thresholds of specimens significantly reduce from dry to wet;elastic modulus and Poisson’s ratio significantly reduce;falling trend of full stress-strain curve at failure stage tends to be gentle, and softening characteristics are obvious. Non-uniform degree of surface deformation of specimens increases from dry to wet,phenomenon of deformation localization starts earlier, and width of deformation localization zone increases significantly. Localized axial and radial starting stress levels of specimens significantly reduce from dry to wet;and it maintains a good linear relationship with moisture content;Based on statistical analysis of deformation field data, damage factor that characterizes the size of rock surface damage was proposed. The damage factor in dry and air-dried states shows a sudden increase, while in wet state, it shows a slow growth trend;there are "mutation points" in evolution curves of damage factors in different moisture states. Statistical results have shown that as moisture content increases, stress level corresponding to damage mutation points significantly reduce.