Rate-dependent experimental study on unsaturated coarse-grained soil controlled by matrix suction
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摘要: 为研究山区高填方路基的时效变形特性，针对路基粗颗粒填料，开展了粗颗粒填料持水特性和一系列常吸力作用下的率相关力学特性试验，采用三种不同剪切速率对试样进行剪切，分析围压、基质吸力及剪切速率对土体强度和变形特征的影响。试验结果表明：粗颗粒填料的土水特征曲线未出现残余吸力值；不同围压下粗颗粒填料的峰值强度可表示为基质吸力的函数，基质吸力越大，非饱和粗粒土的剪切强度越高，且体积剪缩变形越小；非饱和粗粒土的强度与体积变形均受剪切速率的影响，且变化趋势表现出高度一致性，剪切速率越大，试样强度越高，对应的体积变形越小。Abstract: To study the time-dependent deformation characteristics of high-fill subgrade in mountainous areas, the water-retention characteristics of coarse filler and a series of rate-dependent mechanical properties tests under constant suction are carried out for the coarse filler of subgrade. Three different shear rates are used to shear the samples, and the effects of confining pressure, matrix suction and shear rate on the strength and deformation characteristics of soil are analyzed. The test results show that there is no residual suction value in the soil-water characteristic curve of coarse filler. The peak strength of coarse-grained fill under different confining pressures can be expressed as a function of matrix suction. The greater the matrix suction, the higher the shear strength of unsaturated coarse-grained soil, and the smaller the volume shear deformation. The strength and volume deformation of unsaturated coarse-grained soil are affected by the shear rate, and the change trend shows high consistency. The higher the shear rate, the higher the sample strength, and the smaller the corresponding volume deformation.
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图 3 土样在不同基质吸力下的应力-应变曲线
Figure 3. Stress-strain-volume curves of soil samples under different matric suctions
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图 4 基质吸力与偏应力关系曲线
Figure 4. Relation curves between matrix suction and deviatoric stress
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图 5 土样在不同剪切速率下的应力-应变曲线
Figure 5. Stress-strain curves of soil samples under different shear rates
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图 6 土样在不同剪切速率下的体应变曲线
Figure 6. Strain-volume curves of soil samples under different shear rates
表 1 试验控制条件
Table 1 Control conditions in tests
围压σ3/kPa 基质吸力S/kPa 剪切速率v/(mm·min-1) 100，200 50，100，200 0.011 100 50，100，200 0.011，0.005，0.0025 
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表 2 峰值强度拟合参数值
Table 2 Values of fitting parameters of peak strength
围压σ/kPa a b R2 100 6.358 48.834 0.996 200 28.619 219.054 0.907
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