【摘要】 高应力、高水压卸荷条件下岩石的非连续性微缺陷演化过程研究对揭示隧道围岩裂纹的起裂孕育、碎胀裂化和峰值破坏,分析围岩稳定性具有重要意义。利用MTS815型程控伺服刚性试验机开展了砂岩在固定围压、不同水压条件下的水力三轴卸荷试验。试验结果表明:岩石变形在卸荷前以压缩为主,变化微小;卸荷后不久开始快速扩容,直至损伤破裂。水力条件下应力–应变曲线上的各个特征应力值比无水压条件下的饱和试样有不同程度地提高,增加了应变能储备,从初始扩容到峰值强度的历时更短,曲线斜率更陡。随着水压的不断增大,各个特征应力值有所减小,表现在起裂条件降低,压缩极限减小,扩容时间提前,表明了砂岩在高水压条件下的脆性特性进一步增强,抵抗变形破坏的能力逐渐降低。通过扩容特征值与扩容点后的体应变关系,求得初始扩容点后的相对扩容应变与变形模量差,建立了多项式回归关系。研究结论揭示了水力作用下砂岩扩容变形行为的强烈性和突发性,可为水–力双场条件下的围岩变形预测及控制提供参考。更多还原

【Abstract】 The strong and sudden properties of the bulking and deformation behaviors of the sandstones under the hydro-mechanical(H-M) function are studied. The evolution of micro-defects under high geo-stress and hydraulic coupling conditions are critically important to reveal different stages of the micro-cracks evolving from the initiation to the failure and to evaluate the stability of the surrounding rocks. The MTS815 rock mechanical system is used to test sandstone samples collected from Bamiao Tunnel in Sichuan of China, and the H-M coupling experiment is performed under the fixed confining pressure and varied hydraulic pressure. The findings reveal that the rock deformation is compressive before unloading, though the change is small. However, rapid dilatancy proceeds to the failure stages shortly after the unloading. The stress-strain curves under H-M coupling conditions are generally higher than those without hydraulic pressure, implying that the strain energy is enhanced. In addition, the experienced time lasts shorter from the initial dilatancy point to the peak, and the slope of the curves becomes steeper. Furthermore, with the increase of the hydraulic pressure, the key characteristic stress decreases, which is reflected under lower fracture initiation conditions, reduced compression limits and advanced bulking time. Accordingly, the brittle characteristics of the sandstones are further enhanced while the ability to resist deformation and failure gradually decreases. Finally, a polynomial regression relationship is established by calculating the relative expansion strains after the initial expansion points and their corresponding deformation modulus difference values. In conclusion, the findings of this study may provide advices for the forecast and control of the deformation of the surrounding rocks under multi-conditions.更多还原