非饱和黄土等效吸力的研究

作为土力学基本框架的重要组成部分,饱和土的强度理论己经基本趋于成熟,而非饱和土在实际工程中分布更为广泛,工程特性更为复杂,但其强度理论尚不完善。在非饱和土力学中,应力理论和强度理论是非饱和土变形稳定性分析的重要基础。非饱和土力学的研究水平目前还未进入实用阶段,主要原因在于吸力量测的困难。鉴于此,提出用等效吸力代替真实吸力的试验方法并进行验证。以常规静三轴试验得到的原状饱和及非饱和黄土的应力–应变曲线为基础,根据在相同σ1-σ3下产生同一轴向应变ε1的变形等效的原则,确定与对应饱和度Sr相当的围压即为等效吸力。建立饱和度与等效吸力之间的非线性关系,并验证该数学公式的正确性。根据试验结果分析含水率对非饱和土抗剪强度的影响,建立非饱和土的实用抗剪强度公式。该研究为非饱和土理论应用于工程实践提供了一种新的实用方法。

STUDY OF EQUIVALENT SUCTION OF UNSATURATED LOESS

As an essential portion of basic framework of soil mechanics，strength theory of saturated soils has been well developed and widely used in geotechnical engineering. However，unsaturated soils have a wide distribution and display more complex behaviours compared with saturated soils in engineering practice. Until now the research activities in the field of unsaturated soils have been still in the academic stage because of the difficulty of suction measurement. To solve this problem，the equivalent suction has been proposed and validated recently. Based on the principle of equivalence of deformation and the stress-strain curves obtained from triaxial compression tests of intact saturated and unsaturated loess，a determination method of equivalent suction is proposed. The nonlinear relationship formula between equivalent suction and degree of saturation is proposed；and the correctness of this exponential function relationship is verified. Based on testing results，the influence of water content on shear strength is analyzed；and shear strength formula of unsaturated soils is established. It provides a new feasible method for application of unsaturated soil theory to engineering practice.