The Duncan-Chang statistical damage correction model of unsaturated soil considering matric suction
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摘要:
为反映非饱和地基土变形全过程，以某基础工程非饱和土为研究对象，开展固结排水三轴压缩试验。研究发现，非饱和土的偏应力-应变曲线形态近似双曲线，基质吸力对土体力学行为影响十分明显，基质吸力越大，土体偏应力越高。根据非饱和土变形特性及工程特点，选取邓肯-张双曲线模型作为基础模型，引入统计损伤理论，假设非饱和土微元强度服从Weibull概率密度分布，建立邓肯-张统计损伤模型。通过搭建初始切线模量与基质吸力的联系，建立一种新的考虑基质吸力的非饱和土邓肯-张统计损伤模型。给出参数解析方法，得到Weibull分布参数经验表达式，从而修正模型。分析不同基质吸力条件下非饱和土损伤累积规律，采用所建模型和传统邓肯-张模型对比验证非饱和土偏应力-应变试验曲线，证明所建模型的可行性和合理性。研究成果为非饱和土的力学特性研究及辨识模拟提供一定参考。
Abstract:In order to reflect the whole deformation process of unsaturated foundation soil, the consolidated drained triaxial compression test is carried out on the unsaturated soil of a foundation project. It is found that the partial stress-strain curve of unsaturated soil is similar to hyperbola, and the matrix suction has an obvious influence on the mechanical behavior of soil. The greater the matrix suction, the higher the partial stress of soil. According to the deformation characteristics and engineering characteristics of unsaturated soil, the Duncan-Chang hyperbolic model is selected as the basic model, and the statistical damage theory is introduced. Assuming that the micro element strength of unsaturated soil obeys the Weibull probability density distribution, the Duncan-Chang statistical damage model is established. By establishing the relationship between the initial tangent modulus and matrix suction, a new Duncan-Chang statistical damage model of the unsaturated soil considering matrix suction is established. The parameter analysis method is given, and the empirical expression of the Weibull distribution parameters is obtained, which is used to modify the model. The damage accumulation law of unsaturated soil under different matrix suction conditions is analyzed, and the partial stress-strain test curve of unsaturated soil is compared with the traditional Duncan-Chang model, which proves the feasibility and rationality of the model. The research results provide a certain reference for the study of mechanical properties and identification simulation of unsaturated soil.
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Key words:
- unsaturated soil /
- matric suction /
- initial tangent modulus /
- Duncan-Chang model /
- statistical damage
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表 1 Eu和b值
Table 1. Eu and b values
s/kPa Eu/MPa b/10−4 100 16.113 22.436 200 23.684 16.628 300 33.601 12.041 400 37.583 9.747 
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表 2 参数m和F0值
Table 2. Values of parameters m and F0
s/kPa m F0/kPa β R2 100 0.364 385.720 −1.569 0.9762 200 0.487 527.936 −2.376 0.9841 300 0.612 656.831 −4.083 0.9825 400 0.793 703.367 −5.954 0.9763
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