饱和方式对珊瑚砂力学特性影响试验研究

Effect of Saturation Methods on the Mechanical Properties of Coral Sands

由于珊瑚砂特殊的形成环境,造成了其多孔隙且存在内孔隙、颗粒强度低、易破碎等特征,致使其饱和过程中难以达到较高的饱和度。针对易忽视的珊瑚砂饱和问题,利用三轴剪切试验对不同饱和方式下珊瑚砂的力学特征进行研究。结果表明:使用抽真空饱和法达到饱和状态的珊瑚砂峰值强度和滑动摩擦角最大,浸泡饱和法居中,反压饱和法最小;随有效围压的增长,饱和方式对珊瑚砂力学性能的影响逐步减弱;借助不同饱和方式达到饱和状态的珊瑚砂颗粒破碎量存在显著差异,使用浸泡饱和法时最大,而使用抽真空饱和法时最小。颗粒破碎是珊瑚砂峰值偏应力的重要影响因素,但由于饱和过程中也会发生破碎,因此颗粒破碎量随饱和方式的变化与峰值偏应力并不完全相同;需对不同饱和方式下珊瑚砂微细观特征进行研究,对比饱和方式导致试样的差异性,进而全面评价饱和方式对珊瑚砂力学特性的影响。

Due to its special deposition environments,the coral sand has the characteristics of high voids with inner porous,low individual grain strength and prone to grain breakage.The high porosity of coral sand sample is difficult to reach high degrees of saturation in the sample preparations for the laboratory tests.This paper presents the triaxial test results on samples under different degree of saturations.The test results indicate that,the tested peak strength and the internal friction angle reach the maximum on sample saturation prepared by vacuum method followed by the submerging saturation method,and the back pressure saturated samples have the minimum peak strength and internal friction angle.With the increasing of confining pressure,the internal friction angle differences on samples prepared by different saturation methods are smaller.The grain breakage during the sample preparation by different methods has obvious difference with submerging method having the maximum amount of grain breakage and vacuum method having minimum amount of grain breakage.It is also concluded that the grain breakage is an important factor that affecting the peak oblique stress value.Since part of the grain breakage occur during the sample preparation,the amount of total grain breakage cannot completely be associated with the peak oblique stress value.It is necessary to conduct microscopic study on the samples and comparing the differences induced by different saturation methods so that the impact of the sample saturation methods on the shear strength properties of the coral sand samples can be evaluated.