Mechanical Parameters of Concealed Fault Rock Mass on Nujiang River
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摘要:
断层带岩体是工程建设中重点关注的一类特殊岩体，为了获取考虑围压效应的隐伏断层带岩体真实力学参数，依托怒江某水电工程，对坝基深厚覆盖层下隐伏断层带岩体开展三轴试验. 总结了一套断层带岩体取样—试验前处理—施加初始围压—三轴试验—参数取值的评价方法，可避免三轴试验过程中断层带岩体散体以及液压油对试样的影响，使试验结果更接近断层带岩体天然状态下的真实力学参数. 试验结果表明：5个断层带岩体试样的变形模量为449～921 MPa，平均值为665 MPa；黏聚力为0.04～0.22 MPa，平均值为0.13 MPa，取80%保证率的标准值为0.12 MPa；内摩擦系数为0.32～0.61，平均值为0.46，取80%保证率的标准值为0.35；黏聚力试验值比内摩擦系数试验值离散性大，表明断层带岩体黏聚力受物质结构、断层泥含量、胶结程度等的影响更大.
Abstract:The rock mass in a fault zone is a special type of rock mass that has attracted wide attention in the field of civil engineering. Triaxial tests are conducted on the rock mass of a concealed fault zone of a hydropower project on the Nujiang river to obtain the mechanical parameters of the rock mass in the concealed fault zone under confining pressure. Moreover, a systematic method (rock mass sampling in a fault zone, pretreatment of the rock mass prior to test, application of initial confining pressure, triaxial test, and evaluation of mechanical parameters) is summarized. This method avoids the effects of the disintegration of the fault zone and the hydraulic fluid on the samples when the triaxial test is conducted. In this way, the obtained mechanical parameters will be closer to the actual mechanical parameters of the rock mass in the fault zone in a natural state. The results show that the deformation modulus of five samples range from 449 MPa to 921 MPa, with the average value being 665 MPa. The cohesion ranges from 0.04 MPa to 0.22 MPa, with the average value being 0.13 MPa and the standard value being 0.12 MPa at a guarantee rate of 80%. The internal friction coefficient ranges from 0.32 to 0.61, with the average value being 0.46 and the standard value being 0.35 at a guarantee rate of 80%. In addition, the test values of cohesion are more discrete than those of the internal friction coefficient, indicating that the cohesion of the fault zone rock mass is more deeply affected by the material structure, fault gouge content, and cementation degree.
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图 1 怒江某水电工程坝址区地形地貌
Figure 1. Topographic and geomorphological features of a hydropower station on the Nujiang river
图 2 怒江某水电站坝址区发育隐伏断层带岩体
Figure 2. The concealed fault rock mass of a hydropower station on the Nujiang river
表 1 试样物理指标
Table 1. Physical values of samples
试样
编号取样
位置深度/m 直径/cm 高/cm 重量/g 密度/
(g•cm−3)1 号 ZK122 33 5.3 9.9 515 2.36 2 号 ZK122 39 6.1 11.2 769 2.35 3 号 ZK128 65 5.6 9.8 558 2.31 4 号 ZK114 70 5.7 10.1 597 2.32 5 号 ZK114 62 5.1 9.5 460 2.37 
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表 2 断层带岩体变形模型试验结果
Table 2. Test results of deformation modulus of the fault rock mass
MPa 试样编号 变形模量 第 1 个 第 2 个 第 3 个 1 号 728 609 492 2 号 501 511 449 3 号 832 838 825 4 号 921 813 607 5 号 625 622 596
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表 3 三轴试验结果
Table 3. Results of triaxial test
试样编号 σ1/MPa σ3/MPa C/MPa f 1 号 0.96 0.17 0.13 0.52 1.28 0.33 1.60 0.45 1.84 0.54 2.23 0.70 2.89 0.82 2.91 0.96 2 号 0.95 0.15 0.04 0.61 1.26 0.31 1.66 0.49 1.91 0.63 2.34 0.82 3.09 0.97 3.62 1.16 5.09 1.37 3 号 0.82 0.12 0.22 0.35 1.13 0.30 1.63 0.43 1.95 0.61 2.02 0.77 4 号 1.28 0.21 0.17 0.49 1.72 0.39 1.93 0.56 2.07 0.78 2.48 0.96 4.29 1.23 5 号 0.66 0.23 0.08 0.32 1.05 0.48 1.36 0.73 1.50 0.87 1.94 1.09 2.47 1.36 3.17 1.62 3.96 1.95
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