Determination of Shear Strength Index of Completely Decomposed Granite in Macao
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摘要: 以澳门地区31组全风化花岗岩（CDG）的基本物理指标和三轴固结不排水剪试验数据为依据，分析全风化花岗岩的剪切特性和抗剪强度指标的取值。试验结果表明，澳门地区全风化花岗岩应力–应变曲线总体呈应变软化型，孔隙水压力在最大偏应力出现前达到峰值后开始下降，随着黏粒含量的减少下降速度加快，最终可能出现负值。剪胀问题导致澳门全风化花岗岩的剪切强度破坏标准不能仅以主应力差的峰值一种方式取值，总结了3种取值方式，并将黏粒含量作为剪切强度取值的指导性指标，为全风化花岗岩选取强度参数提供新的思路，对提高取值的可靠性有一定帮助。
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关键词:
- 全风化花岗岩CDG /
- 剪切特性 /
- 固结不排水剪强度指标 /
- 强度破坏标准 /
- 黏粒含量
Abstract: Based on the basic physical parameters and triaxial consolidation undrained shear test results of 31 groups of completely decomposed granite (CDG) in Macao, the shear characteristics and the value of the shear strength index of completely decomposed granite were analyzed. The test results show that the stress-strain curve of the completely decomposed granite in Macao is generally strain-softening, the pore water pressure reaches a peak before the maximum deviatoric stress occurs and then begins to decrease, with the decrease of the clay content, the rate of decrease accelerates, and eventually a negative value may appear. It is inappropriate to take the peak value of the principal stress difference as the shear strength failure standard of Macao completely decomposed granite because of the shear expansion problem. 3 value methods were summarized, and the clay content was selected as a guiding index for the value of the shear strength. A new idea is provided for the selection of strength parameters of completely decomposed granite and is helpful to improve the reliability of the value. -
表 1 澳门全风化花岗岩基本物理性质指标和颗粒组成
土样编号 天然含水率
w/%天然密度
ρ/（g·cm–3）孔隙比
e0颗粒组成百分数/% 土的分类[9] 砾粒 砂粒 粉粒 黏粒 >2.0 mm 2.0～0.5 mm 0.5～0.25 mm 0.25～0.075 mm 0.075～0.0 05mm ˂0.005 mm BH5-M6 20.8 2.01 0.629 14.8 19.4 10.4 13.8 23.5 18.1 粉砂混黏性土 BBH6-U4 26.2 1.87 0.809 17.8 25.2 12.6 14.0 16.8 13.6 中砂混黏性土 BMH3-U5 21.5 1.88 0.732 27.8 18.6 3.8 5.4 26.4 18.0 砾砂混黏性土 BMH6-U5 23.6 1.90 0.743 18.4 29.2 10.2 11.6 18.9 11.7 中砂混黏性土 BMH7-U5 15.6 1.90 0.631 27.6 26.6 9.2 11.4 16.0 9.2 砾砂 BMH8-U3 25.2 1.95 0.746 29.6 9.0 5.2 7.6 25.1 23.5 砾砂混黏性土 BMH8-U5 25.2 1.92 0.774 13.6 18.0 9.0 9.2 22.3 27.9 粉砂混黏性土 BMH10-U5 23.4 2.00 0.654 26.8 23.8 9.8 11.4 14.5 13.7 砾砂混黏性土 ABH17-M4 15.5 2.12 0.460 9.6 25.6 23.8 11.8 16.3 12.9 中砂混黏性土 ABH21-M5 15.4 2.10 0.473 7.6 29.4 39.2 12.8 11.0 粉砂混黏性土 AMH11-M4 29.2 1.85 0.872 15.4 18.6 8.6 12.8 25.5 19.1 粉砂混黏性土 AMH2-M6 32.7 1.90 0.872 12.4 21.4 8.2 13.0 27.4 17.6 粉砂混黏性土 AMH2-M7 29.7 1.87 0.859 18.8 17.6 8.6 14.2 26.6 14.2 粉砂混黏性土 ABH15-M6 28.1 1.92 0.788 19.4 14.8 6.8 11.4 23.7 23.9 粉砂混黏性土 ABH13-M6 19.4 2.05 0.561 27.6 21.0 8.6 10.6 20.4 11.8 砾砂混黏性土 ABH9-M6 24.3 1.88 0.772 20.8 16.8 5.8 10.4 25.1 22.1 粉砂混黏性土 ABH7-M4 10.9 2.25 0.321 22.2 28.8 15.4 10.4 11.4 11.8 粗砂混黏性土 ABH7-M6 25.0 1.90 0.763 13.2 21.6 8.8 12.2 26.6 17.6 粉砂混黏性土 ABH14-M6 31.4 1.89 0.863 24.6 15.8 4.8 7.0 24.0 23.8 粉砂混黏性土 ABH40-M5 20.0 1.98 0.624 13.4 30.4 16.6 4.2 8.5 26.9 中砂混黏性土 AMH7-M9 22.0 1.96 0.668 15.2 23.8 13.6 12.4 18.2 16.8 中砂混黏性土 AMH6-M8 19.5 2.03 0.578 13.8 34.8 13.8 6.2 5.1 26.3 中砂混黏性土 AMH6-M12 30.7 1.85 0.893 20.2 19.6 8.2 7.2 21.1 23.7 粉砂混黏性土 AMH6-M17 24.4 1.99 0.675 10.8 29.4 14.8 14.0 16.5 14.5 中砂混黏性土 AMH5-M10 26.8 1.90 0.789 19.0 22.0 11.4 12.8 18.8 16.0 中砂混黏性土 AMH5-M12 28.0 1.91 0.796 12.4 25.6 9.2 6.8 21.3 24.7 粉砂混黏性土 AMH10-U4 18.0 2.01 0.573 5.2 33.6 16.4 14.6 17.8 12.4 中砂混黏性土 AMH4-M4 34.2 1.82 0.976 18.2 17.8 6.6 12.4 30.8 14.2 粉砂混黏性土 ABH19-M6 25.8 1.86 0.813 16.4 25.2 9.6 11.4 18.6 18.8 中砂混黏性土 ABH11-M6 20.0 2.05 0.569 15.8 25.5 11.2 15.3 19.6 12.6 中砂混黏性土 ADH8-M4 19.6 2.09 0.534 15.0 28.6 10.8 9.4 11.4 24.8 中砂混黏性土 平均值 23.6 1.96 0.704 17.9 22.4 11.0 11.7 19.6 17.8 
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表 2 澳门全风化花岗岩三轴固结不排水剪指标统计
土样编号 总应力 有效应力 粉粒含量/% 黏粒含量/% 强度破坏标准 黏聚力ccu/kPa 内摩擦角φcu/（°） 黏聚力c´/kPa 内摩擦角φ´/（°） ˂0.075 mm ˂0.005 mm BH5-M6 10 27 5 31 41.6 18.1 （σ1-σ3）max点 BBH6-U4 14 28 1 37 30.4 13.6 umax后某一点 BMH3-U5 72 20 58 27 44.4 18.0 （σ1-σ3）max点 BMH6-U5 8 26 5 33 30.6 11.7 umax后某一点 BMH7-U5 3 31 1 37 25.2 9.2 umax前某一点 BMH8-U3 19 21 6 28 48.6 23.5 （σ1-σ3）max点 BMH8-U5 27 23 4 32 50.2 27.9 （σ1-σ3）max点 BMH13-M8 16 19 14 26 （σ1-σ3）max点 BMH10-U5 21 26 15 31 28.2 13.7 umax后某一点 ABH17-M4 5 32 1 35 29.2 12.9 umax前某一点 ABH21-M5 3 31 1 33 23.8 11.0 umax前某一点 ABH13-M6 5 30 1 35 32.2 11.8 umax前某一点 ABH9-M6 14 21 12 27 46.2 22.1 （σ1-σ3）max点 ABH7-M4 3 37 1 39 23.1 11.7 umax前某一点 ABH14-M6 26 21 7 33 47.8 23.8 （σ1-σ3）max点 AMH6-M8 20 22 16 28 31.4 26.3 （σ1-σ3）max点 AMH6-M12 18 22 7 32 44.8 23.7 （σ1-σ3）max点 AMH6-M17 9 29 7 36 31 14.5 umax后某一点 AMH5-M10 7 31 1 36 34.8 16.0 umax后某一点 AMH10-U4 36 33 28 35 30.2 12.4 umax前某一点 AMH4-M4 9 26 5 34 45 14.2 umax后某一点 ABH11-M6 12 28 5 33 30.8 12.6 umax后某一点
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