钙质砂饱和机理及效果评价

Calcareous sand is a special geotechnical medium of marine biogenic genesis. The soil particles have the characteristics of porous (including intra-pores), irregular shape, low strength and easily broken. Due to the intra-pores，the calcareous sand could not reach the full saturation in the conventional soil mechanics test. The vacuum saturation combined back pressure saturation method is used to reach higher saturation. However, the particles might be broken during the saturation process. Therefore, in this project the influence of particle crushing and intra-pores on the mechanical properties of calcareous sand will be studied from the aspect of particle morphology, pore distribution, water distribution and macroscopic physical mechanics characteristics. The saturation mechanism of calcareous sand samples will be analyzed comprehensively. Its saturation effect would be evaluated eventually. Comparing with the terrigenous sand, the saturated discriminant standards will be proposed for the calcareous sand. Maintaining the microstructure of calcareous sand, the suitable saturation method will be selected to the calcareous sand. This study will provide an important theoretical basis for the study of the saturated mechanical properties of calcareous sand.

钙质砂是一种海洋生物成因的特殊岩土介质，具有多孔隙（含有内孔隙）、形状不规则、强度低易破碎等特点。由于内孔隙的存在，钙质砂在常规土力学试验时，不能达到很大饱和度；采用抽真空饱和联合反压饱和法增加其饱和度时，颗粒极易破碎，砂体性质随之改变。故而本项目从钙质砂饱和前后颗粒形态、孔隙分布、水分分布及宏观物理力学特性等方面研究饱和过程中颗粒破碎及内孔隙等因素对钙质砂力学性质的影响，分析钙质砂的饱和机理，评价饱和效果，对比陆源砂提出钙质砂饱和判别标准，并立足于保持钙质砂原有微细观结构的基础上，选择适合于钙质砂的饱和方法。本研究将为钙质砂饱和力学性质的研究提供重要的理论依据。

钙质砂是一种形状极其不规则且内孔隙丰富的特殊岩土材料。钙质砂的特殊构造致使其饱和技术一直是钙质砂研究中的关键。在传统土力学试验中，通常采用二氧化碳饱和、真空饱和、水头饱和和反压饱和等方法，或联合使用以制备饱和钙质砂样。不同的饱和方法导致的饱和效果必然有所差异，故对钙质砂的结构特征、力学性能以及颗粒破碎特征会造成一定程度的影响。本项目采用不同的饱和方法对钙质砂进行处理，通过三轴剪切试验方法研究了不同饱和方法对钙质砂力学性能以及颗粒破碎特性的影响，并借助3D扫描技术分析了饱和前后钙质砂颗粒形状的变化。同时，采用反压饱和方式制备了不同饱和度的钙质砂，探讨了饱和度对钙质砂力学性能的影响并确定了一个可以替代完全饱和状态的饱和度范围；并且建立了孔隙水压力系数B与饱和度之间的函数表达式。本项目的研究内容将为非饱和以及饱和钙质砂力学性质的研究提供重要的理论依据。