不同固结度下原状软土先动后静强度特性
Post-cyclic strength behaviors of undisturbed soft soils with different degrees of reconsolidation
-
摘要: 经历动荷载作用后的软土在一段时间后处于完全固结和未固结的中间状态,该状态可用振后固结度的概念进行描述。当前,考虑振后固结度对土体振后强度特性影响的研究较少。因此,通过开展一系列动、静三轴试验,对珠江入海口原状软土的振后强度特性进行研究,重点分析了初始固结围压、循环应力比及振后固结度的影响。试验结果表明:不同条件下土体应力应变曲线的变化趋势相似;土体的振后抗剪强度随着初始围压、循环应力比及振后固结度的增大而增加。其中,当固结围压为20 kPa,振后固结度从0%增加到100%时,抗剪强度从20.2 kPa增加到33.0 kPa;对于振后完全固结的试样而言,当固结围压从20 kPa增加到60 kPa时,对应的抗剪强度从33.0 kPa增加到39.5 kPa。另一方面,存在一临界循环应力比,在该循环应力比作用下,振后土体抗剪强度与相同围压条件下未经历循环荷载作用的土体抗剪强度基本一致。Abstract: The soft soil after cyclic loading is often in an intermediate state between unconsolidated and fully reconsolidated after a period of time, which can be described by the concept of degree of reconsolidation. At present, there are few studies considering the effects of different degrees of reconsolidation on the post-cyclic strength behaviors of soils. Therefore, as eries of dynamic and static triaxial tests are carried out to study the post-cyclic strength behaviors of undisturbed soft soils at the Pearl River Estuary. The effects of the initial consolidated confining pressure, cyclic stress ratio and different degrees of reconsolidation on the post-cyclic strength behaviors of soils are analyzed. The test results show that the variation trends of stress-strain curves under different conditions are similar. The post-cyclic shear strength of soils increases with the increase of the initial confining pressure, cyclic stress ratio and degree of reconsolidation. When the confining pressure is 20 kPa and the degree of reconsolidation increases from 0 % to 100 %, the shear strength increases from 20.2 to 33.0 kPa. For the fully reconsolidated specimens after cyclic loading, when the confining pressure increases from 20 to 60 kPa, the corresponding shear strength increases from 33.0 to 39.5 kPa, respectively. On the other hand, there is a critical cyclic stress ratio, at which the post-cyclic shear strength basically equal to that of soils without cyclic loading under the same confining pressure.