考虑应力路径的软黏土小应变特性试验研究

以苏南地区原状软黏土经K₀固结形成的试样为对象,利用配备了弯曲元系统和局部位移测量系统的GDS应力路径三轴测试系统,研究了小应变范围内应力路径转角θ对剪切模量衰减曲线以及阈值剪应变(γ_0.7)的影响。试验结果表明,土体的初始剪切模量G₀值与初始固结应力大小呈正相关关系,并可表示为与孔隙比e、平均有效应力p′相关的函数关系式。土体的剪切模量在10^-6~10^-3的应变范围内随着剪应变的增加而逐渐衰减,并表现出和试验应力路径与近期应力历史间夹角θ的相关性:应力路径对衰减曲线的影响随着应力路径转角θ的增大逐渐增大,当两者完全相反时,其影响最大。在K₀固结条件下,应力路径转角θ对γ_0.7的影响大于初始固结平均有效应力p′,同时γ_0.7值随着应力路径转角θ的增大而逐渐增大。

Experimental Study on the Small-strain Characteristics of Soft Clay Considering Stress Paths

The test object was undisturbed soil derived from southern Jiangsu after K₀ consolidation. Using GDS stress path triaxial system equipped with bender element and local displacement measurement system, the effect of stress path rotation angle θ on shear stiffness decay curve and threshold shear strain (γ_0.7) under small strain were studied. The results of this study show that the initial value of shear modulus G₀ increased along with the consolidation stress, and G₀ can be expressed as a functional relationship related to void ratio e and the mean effective stress p′. The shear modulus of soil decreases with the increase of shear strain under small strain related to the angle θ between trail stress path and recent stress history. The effect of stress path on decay curve increases along with the stress path rotation angle θ. If the two directions are entirely reverse, the effect is largest. The effect of the angle θ on γ_0.7 is larger than the mean effective stress p′, and the value of γ_0.7 increases along with the θ.