以南沙群岛永暑礁的钙质砂为研究对象,通过三轴排水剪切试验发现:中密钙质砂在不同围压下的应力应变关系具有转型现象,提出了能反映硬、软化和剪胀、缩转型的非线性弹性应力-应变模型。这个模型综合考虑了砂土的临界围压及临界密度对应力-应变关系的影响,经与试验数据比较,验证了理论模型的合理性。 Taking calcareous sand of Yongshu reef in Nansha Islands as the research object, through the triaxial drainage shear test, it is found that the stress-strain relationship of medium density calcareous sand under different confining pressure has the transformation phenomenon, Nonlinear elastic stress - strain model of expansion and contraction. The model considers the influence of the critical confining pressure and critical density of sand on the stress-strain relationship. The rationality of the theoretical model is verified by comparison with the experimental data.