不同固结路径下钙质砂固结排水强度性状研究

An experimental study on consolidated drainage strength of calcareous sand under anisotropic consolidation paths

钙质砂是我国南海岛礁建设的主要吹填材料,岛礁建筑施工中钙质砂地基将受到不同固结路径外荷载作用,开展不同固结路径下钙质砂的固结排水强度特性研究是岛礁地基建设的迫切需求。对取自我国南海某吹填岛礁的钙质砂开展不同固结路径三轴固结排水剪切试验,探究钙质砂的强度参数和颗粒破碎程度随固结路径的演变规律。研究结果表明:钙质砂的应变软化和剪胀特性随平均有效应力的增大、有效主应力比的增大而逐渐减弱;与等向固结工况相比,随着有效主应力比减小至0.45时,钙质砂固结排水峰值强度折减系数介于0.60~0.95之间;在常规应力范围内,当有效主应力比增大,峰值内摩擦角呈减小趋势,介于38°~53°之间。在固结阶段,颗粒破碎程度随偏应力的增大而变大,但在剪切完成后颗粒破碎程度反而最小,剪切阶段的颗粒破碎占主导地位;验证了不同固结路径下峰值内摩擦角与相对破碎率的定量关系式,计算得到的峰值内摩擦角预测值为实测值的0.8~1.2倍。固结应力路径和固结压力不同引起的颗粒破碎程度差异,是导致剪切后钙质砂固结排水强度性质差异的主要原因。

Calcareous sand is the primary fill material used in the construction of islands in the South China Sea.Throughout the process of island construction,the calcareous sand foundation will be subjected to external loads with varying consolidation stress paths,investigating the drainage strength characteristics of calcareous sand under various consolidation stress paths is an urgent requirement in practice.By conducting triaxial consolidation drainage shear tests on calcareous sand samples obtained from a reclamation island in the South China Sea,the evolution of strength parameters and the degree of particles breakage of calcareous sand with varying consolidation stress paths are investigated.The results show that the strain softening and dilation characteristics of calcareous sand diminish progressively as the mean effective stress and the effective principal stress ratio increase.In contrast to isotropic consolidation conditions,when the effective principal stress ratio diminishes to 0.45,the reduction coefficient of peak strength for the consolidated drainage of calcareous sand spans from 0.60 to 0.95.Within the conventional stress range,as the effective principal stress ratio increases,the peak internal friction angle shows a decreasing trend,ranging from 38°to 53°.During the consolidation,the degree of particles breakage increases with the increase of the deviator stress.However,following completion of shearing,the degree of particles breakage paradoxically diminishes,with particle breakage during the shearing phase assuming predominance.The quantitative relationship is verified between the peak internal friction angle and the relative breakage potential under different stress paths.Calculations predict peak internal friction angle values that are approximately 0.8 to 1.2 times the experimentally measured values.Differences in particle crushing caused by varying consolidation stress paths and consolidation pressures are the primary reasons for the differences in the consolidation drainage strength properties of calcareous sand after shearing.