断续裂隙岩体在单向压缩应力状态下的强度与能量特征

Strength and Energy Characteristics of Discontinuous Collinear Fractured Rock Mass under Compressive Stress

【目的】三峡库区边坡岩体内常含断续裂隙,研究探讨这些断续裂隙岩体在压缩应力状态下的岩体强度特征和能量特征,可为三峡库区的防灾减灾提供理论支持。【方法】利用RFPA软件对含不同中、缓裂隙倾角和连通裂隙贯通度变化的岩体在单向压缩应力状态下进行数值模拟试验,分析断续裂隙岩体的强度、声发射能量特征及能量损伤系数特征。【结果】1)断续裂隙岩体的应力-应变曲线在峰值强度后呈现“台阶式下降”现象,它的峰值强度和峰值应变基本呈2个“V”字型,随着裂隙贯通度的增加,峰值强度低值由裂隙倾角20°向30°转变;2)选取裂隙贯通度25%的中、缓倾角断续裂隙岩样和完整岩样在破坏过程中的声发射能量,发现裂隙倾角小于20°的前期积累能量的低频次很突出,在达到峰值强度后会经历第二次声发射能量爆发;3)对于岩体变形破坏阶段的能量损伤系数,在应力峰值前,裂隙贯通度25%岩体的值小于0.1,仅完整岩样的值达0.1,峰后阶段该值急剧上升达到0.8,特别是经历峰后能量释放平台后该值陡升。【结论】研究结果揭示了间断裂隙岩体破坏过程中的强度特征与能量特征,可为三峡库区高边坡断续共线裂隙岩体的合理防治提供重要理论依据。

[Purposes]The slope rock mass in the Three Gorges reservoir area often contains discontinuous fractures. It is of great significance to explore the strength and energy characteristics of discontinuous fractured rock mass under compressive stress for disaster prevention and mitigation in the three Gorges Reservoir area. [Methods]RFPA software was used to conduct numerical simulation tests under unidirectional compressive stress for rock mass with different medium and slow crack inclinances and varying degree of connectivity of connected crack. The characteristics of strength, acoustic emission energy and energy damage coefficient of discontinuous fractured rock mass were analyzed. [Findings] The results show that: 1) The stress-strain curve of the discontinuous fractured rock mass shows a “step-down” phenomenon after the peak strength, and the peak strength and the peak strain basically show two v-shaped shapes. With the increase of the fracture connection degree, the low value of the peak strength changes from 20° to 30°. 2) Acoustic emission energy of fractured rock samples with medium and slow dip angles and intact rock samples with 25% fracture continuity was selected in the failure process. It was found that the low frequency of accumulated energy in the early stage was prominent when the fracture inclination Angle was less than 20 degrees, and the second acoustic energy burst would occur after reaching the peak intensity. 3) For the energy damage coefficient of rock mass deformation and failure stage, before the stress peak, the value of rock mass with 25% fracture connection is less than 0.1, and only the value of intact rock sample is up to 0.1. In the post-peak stage, the value of rock mass with 25% fracture connection increases rapidly to 0.8, and the stress platform rises faster after no peak. [Conclusions]The research results reveal the strength and energy characteristics of discontinuous fractured rock mass in the process of failure, which can provide an important theoretical basis for the reasonable prevention and control of discontinuous collinear fractured rock mass in the high slope of the Three Gorges reservoir area.