Discrete element method simulations of offshore plate anchor keying behavior in granular soils

Abstract

The keying mechanism of plate anchors (PLA) embedded into granular sandy soils is investigated in this work using the discrete element method (DEM) modeling to simulate microscale response and to observe the emergent macroscale behavior. Parameters (e.g., padeye eccentricity, loading direction) that influence anchor keying are analyzed in the simulations. The load-displacement response and embedment losses during keying are evaluated and compared to published experimental results from the literature. The keying mechanism of the PLA for different padeye eccentricities and loading directions are investigated. The DEM results are found to have the same trends as published experimental results. The embedment loss has a bilinear response with the padeye eccentricity which is in accordance with the experimental results reported in the literature. Embedment losses increase linearly with increasing loading directions. Microscale observations of mobilized particle friction, particle rotation, contact force network, and steering coefficient during keying are used to provide insights into the keying mechanisms. The potential for particle mobilization is reached more quickly for the larger padeye eccentricities. The particle rotation is the major keying mechanism for all the cases in the simulations. Finally, the granular assembly adjacent to the PLA is steering from horizontal to vertical for all padeye eccentricities.     

河南铝土矿资源开发战略研究

文章评价了河南铝土矿资源的开发条件,用系统工程方法,反馈机理和耗散结构观点分析了铝土矿资源开发系统的运行机制,提出了铝工业发展战略及具体措施。     

HUBEX区域资料同化系统

介绍HUBEX区域资料同化系统。这个系统采用6 h周期的间歇资料同化方法, 利用全球粗网格分析场资料, 形成冷启动的初估场和同化模式的边界条件。系统还包括资料质量控制、σ面最优插值客观分析、张弛逼近 (Nudging) 初值化、中尺度同化模式预报和后处理等部分, 对来自全球通讯系统、HUBEX加密观测的资料和国家卫星气象中心的导风资料进行同化。最后, 用1998年6月24~28日长江流域的暴雨过程对这个资料同化系统进行测试。     

冻土旁压试验与单轴试验对比

为了认识冻土旁压试验结果与常规试验结果之间的关系,在室内分别开展了冻结重塑黏土的旁压试验和单轴压缩试验,并对试验结果进行了对比分析。结果表明,在各级荷载作用下旁压曲线一般都呈现应变速率衰减的趋势,而单轴曲线在冻土破坏时会出现渐进流动阶段。旁压试验的应力-应变曲线呈现应变硬化型,而且出现初始拟弹性阶段;而单轴试验的应力-应变曲线则属于应变软化型,并在轴向应变大约为10%时达到剪应力峰值。温度相同时,旁压试验的剪切强度以及初始弹性模量都要大于单轴试验,且温度越低差值越大。     

海潮负荷地心运动对GPS坐标时间序列周期信号的影响分析

分别采用地球系统质心（center of mass of the whole earth system, CM）和固体地球质心（center of mass of the solid earth, CE）框架的海潮负荷(ocean tide loading, OTL)改正计算132个全球站的静态精密单点定位PPP坐标,分析海潮负荷引起的地心运动对GPS坐标时间序列的影响。结果表明：1）海潮负荷地心运动在水平和垂直方向上引起的坐标差异分别为0.7 mm和1.3 mm,海潮负荷地心运动对坐标时间序列的影响具有显著的区域分布特征;2）在CM-OTL和CE-OTL中,海潮负荷效应引起的周期信号明显减小,海潮负荷改正所属框架与GPS轨道所属框架的不一致将引入GPS交点年信号、14 d、9 d信号;3）利用IGS精密轨道进行PPP计算时,应采用CE框架进行海潮负荷改正。     

Landsat-8 OLI遥感数据的矿化蚀变信息提取——以重庆市彭水县为例

利用重庆市彭水县Landsat-8 OLI遥感数据和ERDAS-9.3软件进行一系列的图像增强及几何校正处理,对波段进行相关性分析,按照波段特征,选取OLI7、OLI5、OLI4波段作为基础信息源。应用图像的掩膜技术,除去植被信息的干扰,并结合典型的蚀变矿物光谱特征,运用主成分分析方法提取该区域的矿化蚀变信息,主要为铁染及羟基蚀变信息。分析表明,区域已开采矿产资源的分布情况与结果吻合,为后续的区域找矿工作提供了可靠方向。     

Effect of Underground Mine Blast Vibrations on Overlaying Open Pit Slopes: A Case Study for Daye Iron Mine in China

Investigating the propagation and attenuation of blast vibration in rock slopes is the key point to assess the influence of underground mine blasting on overlaying open pit slopes stability and determining the potential risk. In this paper, Daye Iron Mine in China has been chosen as the case to study the effect of blast vibrations on overlaying open pit slopes due to underground mine blast. Firstly, the characteristics of blast loadings are analyzed by the dynamic finite element method. Then, a three dimensional (3D) numerical model of the open pit and the underground mine is made, which is verified by the field monitoring data to prove its reliability. The effect of blast vibration on overlaying open pit slope due to underground mine blasting are discussed based on the peak particle velocity (PPV) and the peak effective tensile stress (PETS) distribution characteristics which are calculated and analyzed by inputting the obtained blast vibration data into the numerical model. The results show that the effect of present mining blasting on the stability of pit slopes are limited because the simulated maximum PPV and PETS of monitoring point on slopes are all < 0.747 cm/s and 0.738 MPa. At last, according to numerical simulations of the underground mine blasting, the PPV predicting formulas for the slopes in Daye Open Pit Iron Mine is proposed based on the classic Sadaovsk formula.     

基于CEI的城市生态环境状况评价——以福建省为例

快速掌握城市生态环境质量及其变化规律有助于相关部门整合生态资源、改善生态环境、规划城市建设、对实现城市可持续发展具有重要的现实意义.基于遥感解译、环境监测、环境统计等数据,利用城市生态环境状况指数定量分析福建省2015—2019年城市生态环境质量,并采用灰色关联分析法度量城市生态环境状况指数与环境质量指数、污染负荷指数...     

滇池大泊口水域水生植物种子库时空特征与恢复潜力

以滇池典型生态修复区——大泊口水域为研究对象,研究了富营养化高原湖泊种子库时空特征、种子库与地表覆盖水生植被及水环境的相关关系和恢复潜力.利用高密度样方原位观测与温室控制种子萌发实验相结合,基于20142016共3年的长期定位研究,分析湖泊平均种子库密度、分布格局及与覆盖水生植物S?rensen相似性关系,结果显示:年...     

单部多普勒天气雷达风场反演及其在数值预报中的应用试验

针对1998年7月5日下午到夜间北京地区出现的一次强降雨过程, 采用“局部VAD法”, 对中国气象科学研究院多普勒雷达测得的1998年7月5日12:00UTC的径向风反演成水平风, 并将反演风应用到数值天气预报 (NWP) 同化系统中, 进行了同化预报试验。结果表明, 反演的雷达风基本符合事实, 将其应用到NWP中, 有助于分析和预报时空尺度较小的中尺度系统。