Undrained Cyclic Response and Resistance of Saturated Calcareous Sand considering Initial Static Shear Effect

Panpan Guo,Zhe Wang,Xiaonan Gong,Gaoyun Zhou,Yu Wang,Gang Lei,Baojian Li

doi:10.1155/2021/4616747

Abstract

Sand elements in the natural or manmade field have often undergone initial static shear stresses before suffering cyclic loading. To explore the effect of static shear stress, a series of undrained cyclic triaxial tests were performed on dense and loose calcareous sand under different initial and cyclic shear stresses. The triaxial test results are used to describe the effect of static shear stress on the cyclic response of the calcareous sand with different relative density. Cyclic mobility, flow deformation, and residual deformation accumulation are the three main failure modes under varying static and cyclic shear stress levels. The cyclic resistance of dense sand is greater than that of loose sand, but the initial static stress has different effects on the cyclic resistance of the two kinds of sand. The dense sand owns a higher cyclic resistance with SSR increasing, while for the loose sand, 0.12 is the critical SSR corresponding to the lowest value of the cyclic resistance. The dense sand has more fast accumulation of dissipated energy, compared with loose sand. Additionally, an exponential relationship is established between static shear stress, relative density, and normalized energy density.

Highlights

With the implementation of the Belt and Road Initiative, calcareous sand, biogenic sediment and skeletal remain of marine organism, has been a topic of interest among geotechnical researchers recently [1, 2]
It can be seen from the single curve that the saturated dense sand and loose sand under anisotropic consolidation conditions (SSR ≠ 0) are consistent with those under the condition of isotropic consolidation (SSR = 0); that is, for a given initial deviatoric stress, Nf decreases monotonically with the increase in cyclic stress ratio (CSR), indicating that the increase in cyclic stress amplitude reduces the cyclic stability of soil
For a given SSR, the dissipated energy required by dense sand is always greater than that of loose sand

Summary

Introduction

With the implementation of the Belt and Road Initiative, calcareous sand, biogenic sediment and skeletal remain of marine organism, has been a topic of interest among geotechnical researchers recently [1, 2]. It was first introduced following the assumption of Nemat-Nasser and Shokooh [27] that the dissipated energy per unit volume resulting from the breakdown of soil skeleton was directly related to the pore pressure buildup This could be an efficient way in evaluating the liquefaction potential of sand under both uniform and irregular cyclic stress conditions. Apart from these, the experimental work confirmed that the amount of energy dissipation that led to liquefaction failure (full pore pressure buildup or development of a specific strain) increased with soil density, confining pressure, and sustained shear stress level [30,31,32] These previous studies have afforded valuable data for the energy-based evaluation of liquefaction potential, the validity of this method remains uncertain when it is applied to evaluate the cyclic resistance of calcareous sand under various initial and cyclic stress conditions. Through the energy-based liquefaction analysis, the dissipated energy could be uniquely correlated with cyclic resistance

Laboratory Test Method

Cyclic Response and Failure Modes under Initial Shear Stress

Cyclic Resistance

Energy Dissipation

Conclusions