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摘要: 通过三轴试验与侧限压缩试验, 研究了膨胀土的强度、超固结性和压缩指标; 建立了胀缩指标与抗剪强度的关系, 分析了膨胀土的结构特征、矿物成分及外界条件等因素对其变形和强度的影响。研究结果表明: 膨胀土具有超固结性, 且超固结性越明显, 从峰值强度达到稳定强度状态时所需的变形越大, 抗剪强度也越大; 裂隙越发育, 其压缩性越高, 超固结性越弱, 抗剪强度指标越小。给出了膨胀土抗剪强度指标的变化范围: 固结排水条件下的粘聚力变化范围为19.8~25.5 kPa, 内摩擦角变化范围为10°~19°; 固结不排水条件下的粘聚力变化范围为23.0~35.3 kPa, 内摩擦角变化范围为3°~14°; 不固结不排水条件下的粘聚力变化范围为37.0~55.0 kPa, 内摩擦角为0°。Abstract: Strength, over consolidation and compression index of expansive soil were studied by triaxial test and confined compression test, the relationship between swell-shrinking index and shear strength was set up, the influences of structural feature, mineral composition and outside factors on deformation and strength property were analyzed.Study result shows that expansive soil has the property of over consolidation, shear strength increases with the over consolidation, the better the fissures develop, the higher the compressibility is, the weaker the over consolidation is, and the smaller the shear strength index is.The variation extents of shear strength index are put forward, cohesion changes from 19.8 kPa to 25.5 kPa, and internal friction angle changes from 10° to 19° under consolidated-drained compression test; cohesion changes from 23.0 kPa to 35.3 kPa, and internal friction angle changes from 3° to 14° under consolidated-undrained compression test; cohesion changes from 37.0 kPa to 55.0 kPa, and internal friction angle is 0° under unconsolidated-undrained compression test.
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Key words:
- subgrade engineering /
- expansive soil /
- mechanical property /
- over consolidation /
- shear strength index
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图 8 抗剪强度与胀缩指标的关系
Figure 8. Relationship between shear strengthes and swelling-shrinking parameters
表 1 不同固结程度和排水条件下的C、φ值
Table 1. C、φunder different consolidation degrees and drainage conditions
指标 试验条件 固结排水(CD) 固结不排水(CU) 不固结不排水(UU) C/kPa 19.8~25.5 23.0~35.3 37.0~55.0 φ/(°) 10~19 3~14 0 
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表 2 不同围压下土样的抗剪强度及指标
Table 2. Shear strengthes and indexes under different confining pressures
标段 抗剪强度/kPa 抗剪强度指标 围压为25 kPa 围压为50 kPa 围压为100 kPa C/kPa φ/(°) K4+160 30.5~44.3 40.8~65.0 62.7~80.1 19.8~25.5 10~19 K5+120 43.0~68.9 59.3~84.0 75.6~107.2 23.0~50.2 18~27 K91+700 70.1~101.5 97.3~135.0 130.0~155.0 41.8~75.0 22.5~32.6
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表 3 峰值强度与残余强度的差值
Table 3. Difference between peak strength and residual strength
标段 围压为25 kPa 围压为50 kPa 围压为100 kPa K4+160 40.0~55.7 54.0~72.4 70.0~91.0 K5+120 38.1~45.2 41.8~67.0 64.0~77.2 K91+700 24.3~36.0 33.5~45.9 42.2~65.0
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表 4 超固结性指标
Table 4. Over consolidated indexes
标段 K4+160 K5+120 K91+700 P1/kPa 43 47 48 P/kPa 120 260 480 ROCR 2.79 5.53 10.00
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表 5 压缩指标
Table 5. Compression indexes
压缩指标 标段 K4+160 K5+120 K91+700 a1-2/MPa-1 0.490~0.700 0.294~0.484 0.039~0.082 E1-2/MPa 2.500~7.000 10.656~15.673 20.937~33.915 压缩性 高压缩性 中压缩性 低压缩性
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表 6 矿物成分
Table 6. Mineral composition
标段 膨胀土类型 伊蒙混层矿物 蒙脱石 高岭石 石英 K4+160 Ⅲ 45.75~71.37 16.60~38.96 1.63~12.10 12~21 K5+120 Ⅱ 47.85~59.06 10.61~16.60 5.36~12.60 18~30 K91+700 Ⅰ 39.43~44.62 9.51~14.04 7.6~13.7 12~28
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