【摘要】 钙质砂因特殊的成因，具有不规则形状和复杂孔隙等特征，容易发生颗粒破碎。本文对南海某岛礁天然钙质砂进行等向压缩试验和大直径三轴排水试验，同时测量颗粒相对破碎率，结果表明：钙质砂强度随轴向应变逐渐增大，达到峰值后明显软化，且峰值偏应力随围压增大而增大；颗粒破碎随着剪切逐渐发生，且围压越大破碎程度越大。采用描述颗粒破碎的SIMSAND模型预测排水条件下的三轴剪切试验，通过试验与预测结果的对比，揭示了模型对钙质砂预测的局限性。本文改进了SIMSAND模型，提出了围压不超过1 MPa时的颗粒相对破碎率公式，优化后的公式能更合理地预测峰值应力对应的轴向应变和颗粒破碎程度的演化。更多还原

【Abstract】 Due to the biological origin and its irregular shape and inner pore, particle breakage generally occurs in calcareous sand. The isotropic compression test and drained triaxial test for natural calcareous sand from an island in the South China Sea were carried out, and the relative breakage index was measured. Results show that the strength of calcareous sand increases gradually with the increase of shear strain and then strain-softening was appeared obviously after reaching the peak deviator stress, which was increased gradually with the increase of confining pressure. Particle breakage occurs gradually during shearing, and the greater the confining pressure, the greater the degree of breakage. The SIMSAND model which can consider particle breakage was used to simulate drained triaxial test, and the evolution of relative breakage index is modified. By comparing the experimental results with the simulations, the limitations of SIMSAND model in describing calcareous sand are verified. Therefore, based on the experimental results, the SIMSAND model is optimized, and a formula suitable for predicting the relative breakage of particles under the confining pressure of 100～1 000 kPa is proposed, and the optimization shows that the optimized formula can predict the development trend of axial strain of peak stress and relative breakage better.更多还原