Gradation affects basic mechanical characteristics of Chinese calcareous sand as airport subgrade of reefs     

Shen Yang  Xue Shen  Hanlong Liu  Huayang Ge  Xiaoxi Rui 《Marine Georesources & Geotechnology》2020,38(6):706-715

Abstract

Construction of the reefs in the South China Sea is a significant foundation to the secure stability and economic development of China. The construction of an airport runway is necessary for this realization. The calcareous sand is the main primary material in the runway construction. A certain type of calcareous sand near a certain reef of the South China Sea was studied in this paper. To investigate this specific calcareous sand, quartz sand was used as a reference for comparison. Microscopic 3-D imaging, compression and triaxial tests were conducted to test the micro, squeezing and shear properties. The effect mechanism of gradation on the calcareous sand’s compressibility and shear characteristics are discussed from a mesoscopic viewpoint using 3-D morphology. Calcareous sand particles are multiangular and flatter in comparison with quartz sand. The larger the particle sizes are, the more different the two sands’ morphologies are. The compressibility of calcareous sand is greater, and the effect of the coarse fraction (5–1?mm) content in the gradation plays the most significant role in this feature. When the coarse particles’ content is less than 25% and the mass ratio of the middle and fine particles (M) is constant, there is the worst coarse fraction content causing the calcareous sand to be most likely compressed. The worst coarse fraction content decreases with the increase in M, and an empirical formula is proposed. When the gradation, relative density and confining pressure are the same, the peak shear stress and strain of calcareous sand are all at a high level. The effect of confining pressure is manifested in calcareous sand. The shear strength and dilation of calcareous sand are also most affected by the medium coarse fraction (5–0.25?mm) content.  相似文献   

A Preliminary Study of Shear Wave in Seafloor Surface Sediments   总被引：1，自引：0，他引：1  

Bo Lu  Ganxian Li  Shaojian Huang 《Marine Georesources & Geotechnology》2006,24(1):17-28

This article preliminarily reports and analyses the transmission characteristics and behaviors of shear wave in the offshore seafloor surface sediments in China, discusses the relationships between the physical and mechanical features of the shear wave and the compression wave, and compares the testing results with that of Hamilton and Chen et al. The result shows that the shear wave can be tested if the seafloor surface sediment has tangent modulus. The shear wave velocity ranges from 50-600 m/s and the measuring frequency from 50-200 kHz. The sound velocity rate of shear wave and compression wave can be used to appraise the stress-strain feature of seafloor surface sediments. This study provides a basis for further describing and appraising the seafloor sedimentary acoustic-mechanical feature and building a geological-acoustic model on China's offshore sea area.  相似文献   

0220号热带风暴(米克拉)特征分析     

李孟植 《海洋预报》2003,20(3):7-11

南海是热带气旋活动较为频繁的地区之一。该地区因其独特的地理环境和复杂的热带大气环流系统，在热带气旋预报工作上存在一定的困难。本文在分析一些气象图表资料的基础上，对2002年第20号热带风暴(米克拉)的形成、发展及消亡进行了探讨和研究。主要从形成的背景环流，气旋的结构等方面入手，总结出一些该气旋所具备韵特有流场，从而为以后的南海自生热带气旋预报工作积累一定经验。  相似文献   

海底浅层介质切变波的初步研究   总被引：2，自引：0，他引：2  

卢博  李赶先  黄韶健 《热带海洋学报》2004,23(4):11-18

初步分析了中国沿海海底浅层介质切变波的传播特性,讨论了多种海底浅层介质切变波与压缩波、物理力学性质之间的关系,并与Hamilton和Chen等人的结果进行了比较。认为海底浅层介质存在切变模量,切变波可以被测量出来,切变波速为50—600m·s-1,测量频率在50—200kHz之间,用波速比可以评价海底浅层介质的应力 应变性质。研究工作有助于描述和评价中国沿海海底浅层介质声学物理性状,并为最终建立中国沿海海底地声模型提供依据。  相似文献   

大生活用海水生化处理技术研究进展   总被引：2，自引：0，他引：2  

王静  张雨山 《海洋技术学报》2002,21(4):51-53

采用海水作为大生活用水最结解沿海城市淡水资源紧缺局面的有效途径之一。该技术得以推广应用的技术关键是大生活用海水的后处理技术，文章综述了大生活用海水的生化处理技术的研究现状，并提出了今后的研究方向。  相似文献   

Random wave-current interactions in water of varying depth     

M. A. Tayfun  R. A. Dalrymple  C. Y. Yang 《Ocean Engineering》1976,3(6):403-420

Refraction of incoherent random gravity waves with currents and bottom topography results in spatial variations in the spectral characteristics of the free surface. Prediction of such variations based on the radiation transfer equation is in a simple analytic form for the case of one dimensional inhomogeneities in currents and topography. This analytic form is examined in terms of two-dimensional wave number- and polar frequency-direction spectra along the associated dynamic and kinematic constraints relevant to wave breaking and reflection. Results are specialized to the simplest case of horizontal shear currents in deep and shallow water with explicit examples to illustrate the relative and combined effects of currents and topography on free surface spectra.  相似文献   

基于坐标归一化和奇异值分解的直接线性变换解法   总被引：2，自引：0，他引：2  

周拥军  寇新建 《测绘科学》2008,(Z1)

直接线性变换方法是数字摄影测量和计算机视觉领域最常用的解析处理方法之一,特别适用于未检校数码相机的三维测量,但直接线性参数间的相关性、物方控制的约束和设计矩阵元素数量级的较大差异,均可导致法矩阵严重病态,从而影响解的稳定性。本文借鉴改进的八点基本矩阵估计算法,采用基于坐标归一化和奇异值分解的解法,即首先将像点和物点坐标进行相似变换得到归一化坐标后组成法矩阵,其次利用矩阵奇异值分解方法代替常规的最小二乘方法,模拟和真实数据表明,此方法可以有效提高解算精度和稳定性。  相似文献   

遥感技术在地质找矿中的应用及发展前景   总被引：6，自引：0，他引：6       下载免费PDF全文

耿新霞  杨建民  张玉君  姚佛军 《地质找矿论丛》2008,23(2):89-93,139

遥感技术作为矿产勘查的一种手段应用于找矿,并取得了一定成就.遥感技术的直接应用是蚀变遥感信息的提取,遥感技术的间接应用包括地质构造信息、植被的光谱特征及矿床改造信息等方面.遥感找矿具有很大的发展前景的领域主要有:高光谱数据、数据融合技术、3S的紧密结合、计算机技术的发展.  相似文献   

刘家坪铜—锌矿区古火山机构特征及其地质意义          下载免费PDF全文

李辉 《甘肃地质》2008,(3):27-35

刘家坪黄铁矿型块状硫化物铜-锌矿床是一个面临闭坑的矿山。对矿区刘家坪组火山岩机构的研究,将是进一步寻找矿体的关键。通过野外地质调查及对刘家坪铜-锌矿区刘家坪组火山岩系的岩石矿物组合和结构构造、岩石化学成分、稀土元素地球化学特征的研究,初步确定了矿区古火山机构及其岩相构造的基本特征,建立了火山岩层序、喷发旋回和喷发类型。  相似文献   

动态最小二乘支持向量机学习算法     

邓兴升  花向红 《武汉大学学报(信息科学版)》2008,33(11):1122-1125

针对大样本集的训练问题和动态训练样本的模型更新问题,提出了动态最小二乘支持向量机学习算法.该算法充分利用已建好的模型,逐渐加入新样本,并可删除位于任何位置的非支持向量,避免了矩阵求逆运算,保证了算法的高效率.大坝变形及电离层延迟两个时间序列的预报实例表明,该算法具有计算时间短、预报精度高的特点.  相似文献