Calculation model of rock joint stiffness considering anisotropic morphology characteristics
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摘要: 为了实现岩体结构面切向刚度和法向刚度的便捷化精准取值,准确分析结构面变形行为特征,以关山隧道闪长岩结构面为例,对结构面形貌信息进行数字化提取,应用3D打印技术制作结构面试样,开展单轴压缩与各向异性直剪试验,提出了各向异性新形貌参数,建立了结构面切向刚度与法向刚度计算新模型。研究结果表明:新形貌参数综合考虑了结构面起伏体上坡段的爬坡角与爬坡高度,有利于反映结构面形貌的各向异性特征,并且同一方向上结构面剖面线的形貌参数服从对数正态概率分布;在物理模型力学试验的基础上,结合结构面形貌参数、结构面壁面强度和法向应力构建的结构面切向刚度计算新模型,不仅降低了计算参数的获取难度,还可以更好地体现结构面切向变形能力的各向异性;改进的双曲函数法向刚度计算模型考虑了结构面初始法向刚度和最大法向闭合量与结构面壁面强度之间的量化关系,避免了复杂的力学测试,简化了法向刚度的获取过程;通过与经典计算模型和力学试验结果进行对比,发现采用新模型计算的刚度更为接近试验值,其中切向刚度与试验值的平均相对误差为2.09%~27.88%,法向刚度与试验值的平均相对误差为3.25%~17.25%,表明结构面切向刚度和法向刚度计算新模型可以更准确和便捷地获取结构面变形参数。Abstract: To accurately and conveniently achieve the shear and normal stiffnesses of rock joint and analyze the deformation behavior characteristics of rock joint, the diorite joint from the Guanshan Tunnel was scanned to obtain the digital information of morphology. According to the digitized joint surface, the replicate joint samples were made by the 3D printing technology. The uniaxial compression tests and anisotropic shear tests were performed for the joint replicas. The new shear and normal stiffness models were established based on the new anisotropic morphology parameter. Research results show that the proposed new morphology parameter takes into account the climbing angles and heights of positive asperities, which is helpful for expressing the anisotropic roughness of joint surface. The morphology parameter of joint profile in the same direction follows a lognormal probability distribution. On the basis of mechanical tests on the physical models, the new shear stiffness calculation model of rock joint established by considering the morphology parameter, joint compressive strength, and normal stress can lower the difficulty in obtaining the shear stiffness, and better reflect the anisotropy of tangent deformation as well. In consideration of the quantitative relationships of joint compressive strength with the initial normal stiffness and joint maximum closure, the improved hyperbolic-function normal stiffness model can simplify the calculation of normal stiffness by avoiding complex mechanical experiments. Compared with the classical calculation models and the mechanical test results, the stiffnesses calculated by the new models are closer to the test values. The average relative error between the calculated and experimental values of shear stiffness is 2.09%-27.88%, and the average relative error between the calculated and experimental values of normal stiffness is 3.25%-17.25%, which demonstrates that the new models can obtain the deformation parameters of the joint more precisely and conveniently. 5 tabs, 19 figs, 46 refs.
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表 1 结构面重构样品材料的质量配合比
Table 1. Mass proportions of materials of reconstructed joint samples
材料 水 砂 水泥 减水剂 硅粉 a 10 20 20 b 10 30 20 1 1 c 10 30 20 2 2 表 2 结构面剪切力学参数
Table 2. Shear mechanical parameters of joints
组别 a b c α/(°) c/MPa φ/(°) φr/(°) c/MPa φ/(°) φr/(°) c/MPa φ/(°) φr/(°) 0 0.06 27.46 21.07 0.08 35.27 30.50 0.09 35.49 30.21 45 0.10 29.61 22.54 0.11 36.46 31.78 0.11 37.31 31.52 90 0.14 37.09 28.53 0.17 40.59 31.07 0.17 40.87 35.06 135 0.08 28.31 24.54 0.10 35.39 32.66 0.11 35.94 31.37 180 0.16 31.06 29.09 0.14 38.36 34.50 0.14 39.56 32.54 225 0.08 28.12 20.14 0.08 36.56 29.88 0.09 37.03 32.47 270 0.09 27.29 24.73 0.13 35.56 28.86 0.14 36.73 30.33 315 0.16 38.14 33.11 0.15 39.44 32.29 0.17 40.49 31.58 表 3 三种试样在三种法向应力下的法向刚度实测值
Table 3. Experimental normal stiffnesses of three groups of joint samples under three normal stresses
MPa·mm-1 σn/MPa 0.2 0.5 1.0 a 11.33 20.98 32.86 b 40.50 47.06 59.06 c 205.03 211.61 229.74 表 4 法向刚度计算值
Table 4. Calculated normal stiffnesses
σJCS/MPa kni/(MPa·mm-1) Vm/mm kn, Bandis/(MPa·mm-1) σn=0.2 MPa σn=0.5 MPa σn=1.0 MPa 10.50 8.29 0.100 12.77 21.30 40.35 33.88 35.90 0.077 41.28 50.06 66.57 54.40 201.03 0.049 209.55 222.23 244.19 表 5 用于刚度计算模型检验的相关参数
Table 5. Related parameters used to examine calculated stiffness model
组别 E/GPa σJCS/MPa β/(°) G σn/MPa ks/(MPa·mm-1) kn/(MPa·mm-1) a 4.02 10.48 15 2.77 9.88 3.98 1 323.46 30 2.96 2.75 1.47 148.99 45 3.10 2.00 1.20 93.38 60 3.36 0.97 0.74 38.08 b 6.82 33.76 15 2.77 31.31 21.85 4 847.74 30 2.96 18.09 14.31 1 853.42 45 3.10 9.34 8.79 648.34 60 3.36 4.09 5.04 222.28 c 15.03 54.37 15 2.77 51.56 47.44 7 707.74 30 2.96 34.02 34.57 3 933.79 45 3.10 18.16 21.61 1 603.82 60 3.36 8.07 12.43 656.58 -
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