盐岩剪切强度与变形特性的加载率效应研究

Loading Rate Effect on Shear Strength and Deformation Properties of Salt Rock

为研究加载速率对盐岩剪切强度与变形性质的影响,采用YZW100型直剪试验机对巴基斯坦高纯度盐岩开展了不同法向压力和不同加载速率下的直剪试验,探讨了盐岩的峰值抗剪强度、残余抗剪强度以及剪胀变形的加载率效应.试验结果表明:随着法向荷载等级的增加,盐岩的剪切破坏趋于延性,并伴有明显的剪胀变形.随着加载速率的增加,剪胀变形减小,而盐岩的峰值抗剪强度和残余强度与加载速率的对数呈线性正相关关系.盐岩强度的加载率效应主要由黏聚力的率效应引起,加载速率从0.01mm/s提高至0.10mm/s,盐岩黏聚力从6.34MPa增长至8.55MPa,而内摩擦角从44.35°略减小至43.6°,几乎保持不变.研究结果可供不同注、采速率地下盐岩储气库围岩稳定性分析提供参考.

Based on the direct shear tests at different loading rates, the loading rate effects on shear mechanical properties of salt rock were evaluated in terms of peak shear strength, residual shear strength and dilatancy deformation.The failure model of salt rock tended to ductile failure, with the increase of the normal force.The dilatancy deformation is negatively correlated with the loading rate, while the peak and residual strength shows a positive linear correlation with the logarithm of loading rate.The loading rate effect on shear strength of salt rock is mainly caused by the rate effect on cohesion.The cohesion of salt rock increased from 6.34 MPa to 8.55 MPa, with the loading rate increasing from 0.01 mm/s to 0.1 mm/s, while the internal friction angle decreased slightly from 44.35° to 43.6°,which is almost constant.The results can provide a reference for stability analysis of underground salt rock caves at different injection and production rates.