摘 要

钙质砂是指富含碳酸钙或其他难溶盐类的一种特殊岩土介质，属于海洋沉积物的一种。其具有形状不规则、多孔隙、易破碎等特点，与常规的陆源砂不同。本文对国内外钙质砂基本力学特性和土体颗粒破碎的研究进展进行阐述，发现对钙质砂的研究大多为围压恒定下应变控制式的常规三轴剪切试验，对不同应力路径下的钙质砂的力学特性研究较为薄弱。为了解钙质砂在不同应力路径下的力学性质和颗粒破碎情况，对其进行等、等、等应力路径的三轴试验。采用相对破碎势对颗粒破碎进行度量，并利用IPP软件对颗粒形态参数进行了统计。试验结果表明：围压是影响钙质砂试件力学特性的主要因素。随着围压的增大，钙质砂试件峰值应力也随着增大，剪胀作用则逐渐受到抑制。在相同固结围压下，应力路径越短，则剪胀越容易发生；破坏围压相近的钙质砂试件，钙质砂试件的剪胀性与应力路径相关性较强；在本文所采用的围压下，三轴剪切过程中，颗粒的破碎随围压的变化是先慢后快；颗粒在发生破碎时，其长宽高有更加接近的发展趋势，使钙质砂峰值强度降低；钙质砂的剪切强度与围压非线性相关，其内摩擦角是近似关于围压变化的一个对数函数。围压减小的应力路径下，其剪切强度较常规三轴压缩试验将会减小。本文对不同应力路径下钙质砂的力学特性和颗粒破碎的机理做出了一定研究，其成果可为考虑构建应力路径影响的钙质砂本构模型提供试验基础。

关键词：钙质砂；应力路径；三轴试验；力学特性；颗粒破碎

Abstract

Calcareous sand is a kind of special geomaterial which is rich in calcium carbonate or other insoluble salts and is a kind of marine sediments. It has the characteristics of irregular shape, porous, and fragile, differs from conventional terrestrial sand. In this paper, the research progress at home and abroad between the basic mechanical properties of calcareous sand and the particle breakage of soil are expounded. It is found that the study of calcareous sand is mostly a conventional triaxial shear test of strain control under constant confining pressure, and the study of the mechanical properties of calcareous sand under different stress paths is weak. In order to understand the mechanical properties and particle breakage of calcareous sand under different stress paths, const , const ,const stress path of the triaxial shear tests were carried out. The relative broken potential was used to measure the particle breakage, and the particle morphological parameters were statistically analyzed by IPP software. The experimental results show that confining pressure is the main factor affecting the mechanical properties of calcareous sand specimen. With the increase of confining pressure, the peak stress of calcareous sand specimen increases, while the effect of dilatation is gradually restrained. Under the same consolidated confining pressure, the shorter the stress path, the more easily the dilatancy occurs; The calcareous sand specimen with similar destruction of confining pressure, the relationship between the dilatancy of the calcareous specimen and the stress path is strong. In the process of shearing, the breakage of the particles with the confining pressure is first slow and fast under the confining pressure used in this paper. The length and height of the particles are closer in the event of crushing, and the peak strength of the calcareous sand is reduced. The shear strength is related to the confining pressure nonlinearity, and its internal friction angle is a logarithmic function about the change of confining pressure. Under the stress path of decreasing confining pressure, the shear strength is less than the conventional triaxial compression test. In this paper, the mechanical properties of calcareous sand and the mechanism of particle breakage under different stress paths are studied. The results can provide the experimental basis for the calcareous sand constitutive model considering the effect of stress path.
Key words: calcareous sand; stress path; triaxial test; mechanical properties; particle breakage

目录

第1章 绪论 1

1.1 钙质砂介绍 1

1.2 国内外研究现状分析 1

1.2.1 钙质砂基本力学特性的研究进展 1

1.2.2 土颗粒破碎的研究进展 3

1.3 研究背景及意义 4

1.4 本文的研究内容及目标 5

1.5 毕业论文进度安排 5

第2章 试样制备与试验方法 6

2.1 试验用料 6

2.2 不同应力路径下的三轴试验 7

2.2.1 试验设备 7

2.2.2 基本步骤 7

2.2.3 需要注意的问题 7

2.2.4 不同应力路径的三轴试验设计 8

2.3 钙质砂颗粒破碎研究 8

2.3.1 筛分时间的确定 8

2.3.2 颗粒破碎指标的选取 8

2.4 颗粒图像的获取和处理 10

2.5 颗粒的基本尺寸参数 11

2.5.1 IPP软件的介绍 11

2.5.2 统计颗粒的基本尺寸参数 11

2.6 颗粒形状参数的定义 12

第3章 试验结果及分析 13

3.1 等（常规）三轴试验 13

3.2 不同应力比的三轴试验 14

3.3 等p试验 16

3.4 两个破坏围压接近的试验结果比较 17

3.5 颗粒破碎分析 18

3.5.1 颗粒破碎的分类 18

3.5.2 颗粒破碎的影响因素分析 18

3.5.3 颗粒破碎的度量 19

3.6 颗粒形态参数量化分析 21

3.7 钙质砂的强度特性 24

第4章 结论 26

4.1 结论 26

参考文献 27

致 谢 30

第1章 绪论

1.1 钙质砂介绍

钙质砂是海洋沉积物的一种，其矿物组成主要是碳酸钙和其他一些难溶盐类，大多分布在南北纬30°之间。在我国，其主要分布在南海诸岛。钙质砂的沉积主要是来自海洋中的贝壳等富含钙质的生物骨架，另有少量的水中碳酸盐类物质和碎屑物。在沉积的过程中，钙质砂通常没有经过长距离的搬运，使它得以保留了其原生生物骨架中细小的孔隙。钙质砂颗粒的形状通常非常不规则，且颗粒中含有大量内孔隙，在常应力水平下就容易发生破碎，与一般的石英砂相比，物理力学性质有比较大的差异，因此成为了人们研究的重点。