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摘要: 将非饱和土基质吸力对土体强度的贡献等效为小主应力增量, 通过分析土体极限应力莫尔圆的几何图形, 求得小主应力增量, 并认为土体在破坏时处于极限状态, 提出了粘聚力和内摩擦角同时变化时的土体强度计算方法, 得到了强度参数随含水量变化的函数关系式, 研究了非饱和黄土破坏时大主应力随含水量变化的关系曲线。分析结果表明:计算曲线与试验曲线的变化规律相同, 随着含水量的增大, 大主应力计算值和实测值的差异越来越小, 其相对误差最大值为11.63%, 最小值为1.59%, 说明该计算方法是可靠的;随着含水量的增大, 当粘聚力和内摩擦角同时变化时, 大主应力计算值较小, 当仅有内摩擦角变化时, 大主应力计算值较大, 两者相差1.26~2.17倍, 说明含水量的变化对非饱和黄土的强度有显著影响。Abstract: Loess suction's contribution to its strength was regarded as the increment of minor principal stress.The increment was gained by analyzing the Mohr's circle geometric figure of loess ultimate stress.When loess was in ultimate state at failure, a computation method of loess strength was put forward under the condition that the cohesion and the internal friction angle synchronously changed, the relationship between the strength indexes and water content was obtained, and the relationship curves of major principal stress and water content of unsaturated loess were analyzed at failure.Computation result shows that the changing rules of computation curves and test curves for major principal stress are same, their difference becomes smaller with the increase of water content, the maximum is 11.63%, and the minimum is 1.59%, so the method is credible.With the increase of water content, when the cohesion and the internal friction angle both change, the computation value of major principal stress is larger than the value only when the cohesion changes, their relative error range is 1.26-2.17 times, which indicates that the influence of water content on the strength of unsaturated loess is significant.
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Figure 3. Relationship curves of major principal stress and water content under different σ3
Figure 4. Relationship curves of major principal stress and water content in double change and single change
Table 1. Relationship of strength indexes and water content
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