Discrete element modeling of sand behavior in a biaxial shear test

The mechanical behavior of sand is very complex, and depends on factors including confining pressure, density, and drainage condition. A soil mass can be contractive or dilative when subjected to shear loading, and eventually reaches an ultimate state, referred to as the critical state in soil mechanics. Conventional approach to explore the mechanical behavior of sand mainly relies on the experimental tests in laboratory. This paper gives an alternative view to this subject using discrete element method （DEM）, which has attracted much attention in recent years. The implementation of the DEM is carried out by a series of numerical tests on granular assemblies with varying initial densities and confining pressures, under different test configurations. The results demonstrate that such numerical simulations can produce correct responses of the sand behavior in general, including the critical state response, as compared to experimental observations. In addition, the DEM can further provide details of the microstructure evolutions during shearing processes, and the resulting induced anisotropy can be fully captured and quantified in the particle scale.     

橡胶混凝土轴压强度细观数值仿真

在细观层次上将橡胶混凝土看作由砂浆、粗骨料、橡胶颗粒、砂浆-粗骨料界面、砂浆-橡胶界面及分布在界面中的初始缺陷组成的多相非均质复合材料,建立考虑初始缺陷的橡胶混凝土细观计算模型,模拟橡胶混凝土在轴压荷载作用下的强度和开裂破坏过程,结果显示:损伤区域首先出现在橡胶颗粒周围;初始缺陷的随机分布位置对橡胶混凝土强度影响不大,但其含量对强度有较明显的影响。与物理试验对比发现:该模型能较好地模拟橡胶混凝土的轴压强度和开裂过程。     

Numerical evaluation of sample size effect on the stress-strain behavior of geotextile-reinforced sand

This paper studies the effect of sample size on the stress-strain behavior and strength characteristics of geotextile reinforced sand using the finite element numerical analysis. The effect of sample size was investigated by studying the effects of varying the number of geotextile layers, the confining pressure and the type of geotextile. Modeling was performed on samples with five different diameters： 38, 100, 200, 500 and 600 mm. The elastic-plastic Mohr-Coulomb model was used to simulate sand behavior. Results showed that small-sized samples show higher values of peak strength and higher axial strain at failure in comparison with large-sized samples. The size effect on the behavior of samples became further apparent when the number of geotextile layers was increased or the confining pressure was decreased. In addition, the results indicated that the magnitude of the size effect on the mechanical behavior of reinforced sand decreases with an increase in the sample size.     

渤海曹妃甸LNG码头布置的潮流数值模拟(英文)

为了在大范围数学模型中合理有效地模拟码头桩基等小尺度建筑物附近的潮流场,采用非结构网格建立了渤海二维有限元潮流数学模型.在面积达85 700 km2的模型范围中将码头桩基概化为面积约20-30 m2的不透水单元,用于直接模拟桩基附近的复杂潮流场.在此基础上,对渤海曹妃甸海域10万吨级LNG(液化天然气)码头布置的走向进行了优化.结果表明:数学模型模拟的潮位和流速等水动力特征与实测结果一致,LNG码头布置的优化结果合理可信.表明建立的能够直接模拟小尺度建筑物的渤海二维有限元数学模型可应用于码头工程布置及优化的潮流场模拟研究.     

Creating a web of support: an important leadership strategy for advancing campus diversity

Research demonstrates that leadership, particularly among presidents, is important for moving a diversity agenda forward and make appreciable progress on it. The research questions pursued here are: What is the role of the college president in advancing a diversity agenda? What strategies do presidents identify as important to facilitating a diversity agenda? There were three main findings: (1) strategies are deployed in a non-linear way best represented through a web metaphor, (2) six sets of actors that serve as key nodes on the web and specific strategies were crucial to enhancing and deepening the web-developing an internal network, hiring, mentoring, partnering with faculty on the curriculum, supporting student affairs staff, working directly with and learning from students, and establishing external networks; and, (3) strategies within the human resource frame are noted by presidents as particularly important to moving a diversity agenda forward.     

静载送桩法在基桩事故处理中的应用

以工程的基桩事故处理为例,详细介绍了将处理和验证相结合的静载送桩处理方法。工程实践证明,该方法节省了处理费用,大大压缩了处理时间,效果直观、良好,避免了同类工程中静载设备移动困难,提供了新思路。     

优化体育课教学途径之我见

体育教学中,如何提高教学效果,是完成教学任务的关键,体育教师应努力提高自身素质,不断改进自己的教学方法,想方设法让学生积极参与到体育教学中来,只有优化体育课教学,才能引导学生有效地学习,主动地学习,愉快地学习.     

水平旋喷桩成拱预加固隧洞开挖施工数值分析

以地铁区间水平旋喷成拱预加固隧道施工为背景,采用MIDAS—GTS岩土数值分析软件模拟隧道开挖施工工艺;通过数值模拟结果的分析,研究水平旋喷桩成拱预加固隧道开挖施工时旋喷桩拱壳的位移和应力、围岩位移和应力的规律和特点;提出水平旋喷桩成拱预加固隧道开挖施工建议,为今后该类施工提供参考．     

马来西亚华文教育在逆境中开拓前进

马来西亚是世界上华文教育最发达地域。五十多年来当地华文教育冲破种种阻拦压迫,不断发展。从小学到大学教育,逐步形成完整的教育体系。     

提升福建省建筑业企业科技进步水平若干思考

新修订的《施工总承包企业特级资质标准》,重点强调了建筑业企业的科技水平。针对该《资质标准》各硬性指标,建筑业企业惟有寻找差距,夯实资质,才能保级升级。为此,文章根据福建省建筑业企业实际情况从观念、科技体系、工法、专利、产学研结合、科技经费、政府扶持等方面提出几点参考性建议。     

数学建模与现代教学模式的探索

论述数学建模对培养学生的创造性、竞争意识和社会应变能力的作用,研究了数学建模对现代教学模式构建的重要作用,提出了在教学中应该强调的是发现知识的过程,而不是简单地获得结果,重要的是培养创造性解决问题的方法和养成不断探索的精神,而数学建模正是培养这种精神的有效载体。     

软土场地与静压预制桩的压桩力控制

论述静压预制桩压桩力对地表土层和下卧软土层承载能力的要求。在建立两者之间关系时，考虑压入土中桩的挤土效应对软土结构的破坏和因此引起的承载能力的降低。提供了不同型号压桩机在不同表土层厚度条件下，对含水量不同的软土层的许用压桩力的粗略定量解答。     

利用Mathematic进行的一个镜像法问题的数值模拟

该文针对利用镜像法求解问题时,其所给的数学结果过于复杂,不利于对问题的物理认识的特点出发,利用Mathematic对数学结果进行了数值模拟,并绘制了相应的直观的曲线图形,进而十分容易的从复杂的数学结果中提炼其所包含的物理规律.     

加快推进龙岩市域中心镇建设的若干思考

从龙岩市域小城镇发展态势看,龙岩城镇化已经到了加速发展阶段,中心镇作为连接城市与乡村的重要节点和统筹城乡发展的重要载体,应加快推进。新时期加快农村城镇化,应着眼于城乡统筹一体化发展,进一步完善中心镇的整体规划,从创新管理体制、整合各类建设项目、加大资金投入、加强投融资运作、灵活用地政策、加强人才保障等方面加大政策扶持力度,确保中心镇健康、有序发展。     

简我国教育现代化的区域推进战略

进入２１世纪，实现教育现代化已成为我国部分发达地区教育发展的目标，一个教育现代化区域推进的态势正在形成，实行教育现代化区域推进战略已成必然。所谓教育现代化的区域推进战略，是指在我国全面推进教育现代化的时机尚未成熟时，先在部分发达地区推进教育现代化，进而带动全国范围内教育现代化的进程，最终在全国实现教育现代化的一种教育现代化实现方式的战略选择。一、实施教育现代化区域推进战略的必然性与可能性教育现代化是现代化的重要组成部分，是经济社会发展到一定阶段必然产生的对教育发展的客观要求。推进教育现代化需要以…     

人工挖孔桩桩侧与桩端阻力的试验研究

通过两根人工挖孔桩的静载试验 ,从埋于桩中不同层面的混凝土应变传感器和桩端压力传感器所获得的实测数据 ,分析了人工挖孔桩的荷载传递规律及竖向承载力性状。实测结果表明勘察报告提供的土层极限侧阻力标准值偏小 ,说明人工挖孔桩按端承桩进行设计是不经济、不合理的。