Energetics parameter estimation of jointed rock mass based on Hoek-Brown failure criterion
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摘要: 岩体变形和破坏可以看作能量耗散和释放的过程。由于节理岩体结构复杂且难以开展室内试验,因此无法通过试验直接求取其能量学参数。基于Hoek-Brown准则和岩石能量理论,提出了节理岩体在临界状态能量学参数的估算方法。针对含贯通节理(或层面)岩体,通过修正岩块单轴抗压强度以体现贯通节理的方向效应。采用PFC3D分别模拟小尺寸岩样(Φ50 mm×100 mm)和大尺寸岩体(Φ2 m×2 m)的三轴压缩试验,通过岩石三轴试验结果拟合岩石数值模拟的细观参数并应用于节理岩体的模拟。根据节理岩体模拟得到应力应变曲线和能量流,验证了Hoek-Brown准则对节理岩体能量参数估算的合理性。Abstract: The deformation and failure of rocks are a process of energy dissipation and release. For the jointed rock masses, the estimation of energetics parameters during loading procedures is a challenge because of their complex structures and difficulties of laboratory tests. The paper proposed a methodology for the energetics parameter estimation of jointed rock masses in critical state based on the Hoek-Brown failure criterion and rock energy theory. For the rock mass with continuous joints (or layers), the orientation effect of continuous joints was reflected by the revised uniaxial compressive strength of rock piece. The PFC3Dnumerical simulation software was used to simulate the triaxial compressive process with small size models of rock pieces (Φ50 mm×100 mm) and big size models of rock masses (Φ2 m×2 m). The mesoscopic parameters of rock numerical model were calibrated by the result of triaxial compression test and applied for the numerical simulation of jointed rock mass. The estimated energetics parameters derived from Hoek-Brown failure criterion were proved to be accurate by the validation with simulated stress strain curves and energy curves.
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表 1 PFC3D模型细观参数
Table 1. Mesoscopic parameters of PFC30 rock model
细观参数 取值 墙体 法向刚度/(N·m-1) 1.2×109 切向刚度/(N·m-1) 1.2×109 颗粒 法向刚度/(N·m-1) 1.2×108 切向刚度/(N·m-1) 1.2×108 密度/(g·cm-3) 2 650 最小粒径/m 1.0×10-3 粒径比 3.0 摩擦系数 0.8 平行粘结
模型抗拉强度/Pa 2.0×108 内聚力/Pa 5.0×107 有效弹性模量 1.0×109 内摩擦角/(°) 30.0 平滑节理模型
(smooth-joint)法向刚度/(N·m-1) 1.0×1070.1 切向刚度(N/m) 1.0×107 抗拉强度/Pa 2.0×106 内聚力/Pa 5.0×105 摩擦系数 0.3 影响范围 0.1 表 2 含不同倾角贯通节理岩体的三轴抗压强度
Table 2. Triaxial compressive strengths of layered rock mass with different layer dip angles
节理倾角/
(°)PFC模拟
TCS(MPa)σc修正
系数H-B估算
TCS/MPa无 56 1 49.2 15 34 0.61 33.4 30 22 0.39 24.5 45 12 0.21 16.6 60 15 0.27 19.0 75 32 0.57 31.9 90 43 0.77 39.9 表 3 三组优势节理产状和直径分布参数
Table 3. The distribution parameters of orientations and diameters of dominant joint sets
优势组 产状 直径或迹长 分布 倾向/(°) 倾角/(°) k 分布 a 最大/m 最小/m 1 Fisher 120 90 200 power-law 4 2.0 1.2 2 30 20 500 4 2.0 1.2 3 70 45 500 3.2 2.0 1.2 表 4 断续节理岩体峰值强度和弹性模量估算
Table 4. The estimated TCS and elastic modulus of jointed rock masses
节理密度/
(m2/m3)Jv
(条·m-3)GSI mb S a σ1/
MPaE0/GPa PFC3D H-B H-D1 H-D2 0.0 0.0 90 11.89 0.329 0.501 59.8 2.10 97.74 4.47 2.01 0.5 1.59 75 6.96 0.062 0.505 33.2 1.34 39.11 3.47 1.46 2.0 9.87 52 3.06 0.005 0.530 16.7 0.49 10.41 1.73 0.73 4.0 12.57 50 2.85 0.004 0.534 15.8 0.355 9.27 1.54 0.65 6.0 17.98 47 2.56 0.003 0.542 14.4 0.152 7.80 1.27 0.53 表 5 三轴加载试验含断续节理岩体峰值状态的弹性能估算值
Table 5. The estimated elastic energy in the peak stress of jointed rock mass under the triaxial loading
节理密度/
(m2·m-3)弹性能/106J PFC3D 式(9)* 式(2) 0 6.958 5.470 4.760 0.5 2.901 2.288 2.777 2 0.918 1.121 0.754 4 0.864 1.117 0.742 6 0.450 1.139 0.320 *:使用式(9)估算时峰值强度采用H-B准则估算,弹性模量采用H-D准则估算;*:使用式(2)估算时峰值强度和弹性模量均使用PFC3D的模拟结果 -
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