钙质砂的休止角研究与工程应用

砂土的天然休止角对土堆设计、基坑设计和边坡稳定性研判有重要的指导意义。砂土的天然休止角受土颗粒的摩擦特性、颗粒形状、粒径和含水状态等诸多因素的影响。开展了钙质砂的天然休止角试验，研究了多种因素对钙质砂天然休止角的影响规律。结果表明：钙质砂3种常见颗粒形状中，片状休止角最大，枝棒状次之，块状最小；钙质砂天然休止角随着粒径的增大而增大；当平均粒径相同时，天然休止角随着不均匀系数的增大而增大，随着曲率系数的增大而减少；通过与标准石英砂的对比试验发现，石英砂的天然休止角小于钙质砂天然休止角。对现场钙质砂边坡测量后表明，钙质砂地基经过振冲挤密后基坑开挖最大坡角略大于室内测得的天然休止角。研究结果对钙质砂土堆和基坑设计等工程实践有一定指导意义。

Study of natural repose angle of calcareous sand and engineering application

The natural repose angle of sand has important guidance for mound construction, foundation design and slope stability analysis. The natural repose angle is mainly affected by friction, particle shape, grain size and water content of sand. In this paper, the natural repose angle of calcareous sand under various conditions is tested. In the three common particle shapes of calcareous sand, the flake particles present the largest repose angle; the rod stick particle shapes present less, and the block shape ones show the smallest value of angle. The natural repose angle of calcareous sand increases with the increase of grain size. When the mean particle size is the same, the natural repose angle increases as the inhomogeneous coefficient increases, and decreases as the curvature coefficient increases. The natural angle of repose of quartz sand is smaller than that of calcareous sand. It is mainly determined by the mineral composition and particle shape. The underwater repose angle of calcareous sand is smaller than that of natural repose angle in general. The maximum angle of foundation ditch slope is larger than the tested natural angle of repose. The results are instructive for coral reef mound constructions and design.