To explore the feasibility of geogrid reinforcement as a promising countermeasure to improve the liquefaction and post-liquefaction resistance of calcareous sand, extensive undrained monotonic and multi-stage triaxial tests were performed on unreinforced and geogrid reinforced calcareous sand with different relative densities. The test results illustrate that pore pressure generation curves of unreinforced and reinforced calcareous sand gradually evolve from S-shaped to hyperbolic-shaped with the increase in relative density, cyclic stress ratio, and effective confining pressure. Following this, a pore pressure model applicable to both unreinforced and reinforced calcareous sand is proposed. The liquefaction resistance of calcareous sand increases with the increase in relative density, whereas an elevated cyclic stress ratio increases its liquefaction susceptibility. A virtually unique relationship can be observed between the liquefaction resistance normalized to the product of phase transformation strength ratio and relative density against the number of cycles for triggering liquefaction, providing an effective means of early assessing sand liquefaction resistance. Moreover, the geogrid exhibits excellent reinforcement efficiency in enhancing the liquefaction resistance of calcareous sand at relative densities of 50% and 70%. During the post-liquefaction stage, increasing relative density and geogrid reinforcement can accelerate the recovery of stiffness and strength for liquefied calcareous sand and improve the post-liquefaction strength. In general, geogrid reinforcement is considered a good alternative to densification for improving the engineering properties of calcareous sand and offers great application prospects in marine engineering construction.

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无加筋和土工格栅加筋钙质砂的液化及液化后行为

为了探讨土工格栅加筋作为提高钙质砂抗液化和液化后抗力的一种有前景的对策的可行性，对不同相对密度的未加筋和土工格栅加筋钙质砂进行了广泛的不排水单调和多阶段三轴试验。试验结果表明，随着相对密度、循环应力比和有效围压的增加，未加筋和加筋钙质砂的孔隙压力生成曲线逐渐由S形演变为双曲线形。在此基础上，提出了适用于未加筋和加筋钙质砂的孔隙压力模型。钙质砂的抗液化能力随着相对密度的增加而增加，而循环应力比的增加则增加了其液化敏感性。在归一化为相变强度比和相对密度的乘积的抗液化性与触发液化的循环次数之间可以观察到几乎独特的关系，为早期评估砂的抗液化性提供了有效的手段。此外，该土工格栅在提高相对密度50%和70%钙质砂的抗液化能力方面表现出优异的加筋效率。在液化后阶段，增加相对密度和土工格栅加筋可以加速液化钙质砂刚度和强度的恢复，提高液化后强度。总的来说，土工格栅加筋被认为是改善钙质砂工程性能的致密化的良好替代方案，在海洋工程建设中具有广阔的应用前景。