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Evaluation of strength for coral sand and gravel mixed deposits

珊瑚砂砾石混合矿床强度评价

基本信息

批准号：
06650548
负责人：
SHINJO Toshiya
金额：
$ 1.22万
依托单位：
University of the Ryukyus
依托单位国家：
日本
项目类别：
Grant-in-Aid for General Scientific Research (C)
财政年份：
1994
资助国家：
日本
起止时间：
1994 至 1995
项目状态：
已结题

项目摘要

Calcareous sediments, which consist of such bioclastics as coral, shell and foraminifera, distribute in shallow tropical and sub-tropical sea-water. In this study the mechanical properties of the calcareous sediments are clarified in order to evaluate the strength of coral sand and gravel mixed deposits for practical use based on the gradation characteristics. Samples used are dredged from sea floor in coral reefs around Ryukyus Island. A series of consolidated drained triaxial compression tests, permeability tests and oedometer tests for K_0 value are carried out on reconstitute samples with head-cut gradation, similar gradation and different content of coral gravel.According to triaxial test results, the peak friction angle of sand and gravel mixed deposits is affected significantly by the coefficient of uniformity and the content of coral gravel. In permeability tests the coefficient of permeability of coral sands is depend on a void ratio, the content of coral gravel and the presence of fine sand less the particle size of 0.25mm. In the determination of K_0 value in the oedometer it is important to take account of the rigidity of an oedometer ring. K_0 value of coral sand measured with relatively rigid oedometer ring is 0.5 irrespective of the void ratio, while this value increases up to 0.8-0.9 under the stress level where a particlebreakageoccurs.

钙质沉积物分布于热带和亚热带浅水海水中，由珊瑚、贝壳和有孔虫等生物碎屑组成。本研究明确了钙质沉积物的力学性质，以便根据级配特征评价珊瑚砂和砾石混合沉积物的实际应用强度。使用的样本是从琉球岛周围珊瑚礁的海底挖来的。对头切级配、级配相似、含砾量不同的珊瑚砾石重构样进行了一系列固结排水三轴压缩试验、渗透性试验和K_0值测井仪试验。三轴试验结果表明，砂砾石混合沉积物的峰值摩擦角受均匀系数和珊瑚砾石含量的显著影响。在渗透试验中，珊瑚砂的渗透系数取决于孔隙比、珊瑚砾石的含量和小于0.25mm的细砂的存在。在确定测温计的K_0值时，必须考虑测温计环的刚度。相对刚性测环测得的珊瑚砂K_0值与孔隙比无关，均为0.5，而在发生颗粒破碎的应力水平下，K_0值可达0.8 ~ 0.9。