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精确的试验测试显示,土体在小应变下呈非线性作用,用常规的室内试验和传统的线弹性分析方法不能真实描述土的刚度变化,只能采用原位试验和非线性分析方法来确定。基于Bolton等人提出的平面应变下不排水膨胀试验的非线性分析理论,研究了剑桥自钻式旁压试验过程中土体刚度随应变的变化规律,并与线性分析结果进行了对比。试验和分析结果表明:小应变下土体刚度具有高度的非线性,随应变的增加发生衰减,但在不同应变区间衰减程度不同;土体割线模量值大于切线模量值,其差值随应变的增加逐渐减小;传统的线性分析低估了土体弹性作用范围和强度,而采用非线性分析能确定不同应变下土的刚度参数,真实反映土的非线性作用特点。
Accurate tests show that the soil behaves nonlinearly under small strain. The conventional in-house tests and the traditional linear elastic analysis methods can not describe the soil stiffness changes accurately, and can only be determined by in-situ tests and nonlinear analysis methods . Based on the nonlinear analysis theory of undrained expansion test under plane strain proposed by Bolton et al., The variation of soil stiffness with strain during self-drilling Cambridge under-pressure test was studied and compared with the linear analysis results. The results of tests and analysis show that the stiffness of soil under small strain is highly nonlinear and decays with the increase of strain, but the attenuation is different in different strain regions. The value of secant modulus of soil is larger than the tangent modulus, The traditional linear analysis underestimates the range and intensity of soil elasticity, while the non-linear analysis can determine the soil stiffness parameters under different strains, which truly reflects the nonlinear characteristics of soil.