STUDY ON COMPRESSION AND CRUSHING MECHANICAL PROPERTIES OF CALCAREOUS SAND CONSIDERING INFLUENCE OF MORPHOLOGY AND GRADING
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摘要: 针对岛礁大型构筑物修建过程中由于高应力而导致作为地基材料的钙质砂发生破碎,进而引发地基沉降变形问题。本文采用高压固结仪对钙质砂开展了一系列终止压力为16 MPa的侧限压缩试验,研究了高应力水平下钙质砂的压缩破碎特性。同时基于显微图像采集和处理技术对钙质砂颗粒的形状参数(圆度和完整度)进行了定量化表征,研究了钙质砂的形状分布规律。最终分别探讨了级配特征(如平均粒径、不均匀系数)、形貌特征等因素对钙质砂压缩和破碎特性的影响。结果表明:随着平均粒径的增大,钙质砂颗粒的形状不规则程度逐渐增加,其棱角也越发育。随着竖向应力的增大,在e-logp平面内,不同粒径钙质砂的压缩曲线逐渐会聚并相交于一条直线,初始粒径对其压缩特性的影响逐渐减小以致消失。而不同级配钙质砂的压缩曲线也发生会聚,但未相交于一条直线。当试样的不均匀系数(Cu)相近时,其压缩破碎量随着平均粒径(d50)的增大而逐渐增加,当试样的d50相近时,其压缩破碎量随着Cu增大而逐渐减小。上述研究成果将对南海岛礁大型工程建设提供重要科学依据。Abstract: The scale of reef engineering in the South China Sea is gradually increasing. The construction of some structures with large loads can inevitably lead to the crushing of calcareous sand that can be the main material of foundation. Therefore,it is important to study the compression and the crushing mechanism of calcareous sand under high stress. In this paper,the basic geometric parameters of calcareous particles were obtained based on the microscopic image acquisition and processing technology. The shape of particles was quantitatively characterized by two shape parameters of sphericity(S) and convexity(C). A series of confined compression tests,based on a high-pressure oedometer instrument with a termination pressure of 16 MPa,was carried out to investigate the compression and breakage characteristics of calcareous sand in high stress. The effect of particle size,particle distribution,and particle shape on the compressive and crushing properties of calcareous sand were also discussed respectively. The result showed that with the increase of average particle size,the shape of calcareous sands was more irregular,and the corners were also developed. With the increase of stress,the compression curves of calcareous sand with different particle sizes tend to converge on a straight line. The influence of initial particle size on the compression characteristics of the samples decreased and disappeared eventually. Meanwhile,for calcareous sand of different grades,the compression curve also converged but did not intersect in a straight line. The compression characteristics of samples were still influenced by the initial grades. It's worth noting that when the non-uniformity coefficient(Cu) wass close,the compression and a crushing amount of calcareous sand gradually increased with the increase of average particle size(d50). However,when d50 was close,its compression and crushing amount gradually decreased with the increase of Cu.
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Key words:
- Calcareous sand /
- High stress /
- Particle breakage /
- Shape /
- Grading
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表 1 试样基本物理参数
Table 1. Basic physical parameters of samples
试样 Gs 粒径/mm d50/mm d60/mm d30/mm d10/mm 不均匀系数Cu 曲率系数Cc 钙质砂 2.76 0~2 0.412 0.495 0.285 0.160 3.10 1.03 福建砂 2.65 0.063~1.180 0.409 0.432 0.344 0.272 2.27 0.99 表 2 不同d50、Cu钙质砂试验方案
Table 2. Test programs of compression with different d50 and Cu
粒组名称 Gs 粒径/mm d50/mm d60/mm d30/mm d10/mm Cu Cc 单粒组 2.76 0.063~0.150 0.106 0.115 0.089 0.072 1.61 0.96 0.150~0.212 0.181 0.187 0.169 0.156 1.20 0.97 0.212~0.300 0.256 0.265 0.238 0.221 1.20 0.97 0.300~0.425 0.362 0.375 0.338 0.313 1.20 0.97 0.425~0.600 0.513 0.530 0.478 0.443 1.20 0.97 0.600~1.180 0.890 0.948 0.774 0.658 1.44 0.96 1.180~2.000 1.590 1.672 1.426 1.262 1.36 0.96 混合粒组 2.76 0.300~0.60 0.425 0.460 0.375 0.325 1.42 0.87 0.212~1.18 0.425 0.528 0.329 0.243 2.17 0.84 0.150~1.18 0.425 0.522 0.295 0.191 2.73 0.94 表 3 不同单粒组钙质砂颗粒形状参数
Table 3. Shape parameters for calcareous sand with different particle sizes
粒径/mm S Sd C Cd 0.063~0.150 0.881 0.043 0.974 0.013 0.150~0.212 0.872 0.046 0.971 0.013 0.212~0.300 0.863 0.052 0.969 0.015 0.300~0.425 0.854 0.048 0.961 0.018 0.425~0.600 0.823 0.064 0.948 0.029 0.600~1.180 0.842 0.064 0.957 0.018 1.180~2.000 0.847 0.059 0.953 0.019 表 4 试样压缩破碎结果
Table 4. The result of samples compression and crushing
试样 e0 av Br 钙质砂 1.051 0.032 0.135 福建砂 0.748 0.007 0.028 -
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