Effect of strain history on the monotonic and cyclic response of natural and reconstituted silts
Effect of strain history on the monotonic and cyclic response of natural and reconstituted silts
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DOI：
10.1016/j.soildyn.2022.107329
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发表时间：
2022-09
影响因子：
4
通讯作者：
A. Dadashiserej;A. Jana;A. Stuedlein;T. M. Evans
中科院分区：
文献类型：
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作者：
A. Dadashiserej;A. Jana;A. Stuedlein;T. M. Evans
通过一系列等体积、分阶段、应力和应变控制的循环直接简单剪切试验，研究了应变历史对完整和重构、低塑性和高塑性粉砂沉积物的单调和循环响应的影响。在许多情况下，由于循环后再固结后密度增加、明显的假超固结以及可能增加的侧向应力的有益影响，承受应力控制载荷的样本表现出循环阻力的逐渐增加。这种影响超过了由于先前的应变历史而造成的织物破坏的有害影响。然而，当使用不同的剪切应变循环失效标准进行评估时，一些样本表现出不一致的循环阻力演变。早期剪切阶段剪切应变的对称积累并不总是导致循环后阻力的增加趋势；此外，根据最大剪切应变的幅度，循环阻力可能会在后续剪切阶段发生增加或减少。分阶段应变控制试验用于研究土壤对小剪切应变和大剪切应变的循环响应，后者导致在接下来的加载事件中超固结（OC）淤泥样本的循环阻力降低，使用剪切波速度 Vs 进行了确认，测量结果表明在大应变事件后存在大量的织物扰动。相比之下，经受多个阶段的小循环剪切应变的正常固结 (NC) 和 OC 样本表现出 Vs 逐渐增加，其大小随应力历史而变化。 NC 样本中循环阻力的增加与再固结后伪超固结的增加有关。所有承受阶段循环荷载的淤泥样本的单调不排水抗剪强度在循环后再固结后增加；强度的增加和体积趋势的变化分别由循环后再固结的幅度和从 Vs 推断出的土壤结构的变化决定。
The effect of strain history on monotonic and cyclic response of intact and reconstituted, low and high plasticity silt deposits have been investigated through a series of constant-volume, staged, stress- and strain-controlled cyclic direct simple shear tests. In many cases the specimens subjected to stress-controlled loading exhibited a progressive increase in cyclic resistance due to beneficial effects of increased density following post-cyclic reconsolidation, apparent pseudo-overconsolidation and presumably increased lateral stresses. Such effects outweighed the detrimental effects of fabric destructing as a result of the prior strain history. However, some specimens exhibited an inconsistent evolution of cyclic resistance when assessed using different shear strain cyclic failure criteria. Symmetric accumulation of shear strains in earlier shearing stages did not consistently result in an increasing trend in the post-cyclic resistance; additionally, increases or decreases in cyclic resistance can occur in subsequent shearing stages depending on the amplitude of the maximum shear strain. Staged, strain-controlled tests were used to investigate the cyclic soil response to small and large shear strains, the latter of which caused a reduction in the cyclic resistance of overconsolidated (OC) silt specimens in the following loading event, confirmed using shear wave velocity,Vs, measurements which indicated substantial fabric disturbance following the large strain event. In contrast, normally-consolidated (NC) and OC specimens subjected to multiple stages of small cyclic shear strain exhibited progressive increases inVs, the magnitude of which varied with stress history. The increase in cyclic resistance in the NC specimens was related to increased pseudo-overconsolidation following reconsolidation. The monotonic undrained shear strength of all silt specimens subjected to staged cyclic loading increased following post-cyclic reconsolidation; the increase in strength and changes in volumetric tendencies are governed by the magnitude of post-cyclic reconsolidation and changes in soil fabric inferred fromVs, respectively.