二级新型悬臂式挡土墙主动土压力计算方法

基于土的塑性极限分析理论,考虑滑裂面上填土黏聚力及填土与二级新型悬臂式挡土墙墙背接触面上的黏着力,研究了挡土墙土压力受力分析模式,取墙后滑动土体的水平薄层单元进行受力分析,建立极限状态下悬臂式挡土墙主动土压力的一阶微分方程,给出了土压力强度、土压力合力、土压力作用点的理论计算公式。研究结果表明,二级新型悬臂式挡墙上墙应力分布呈抛物线形状;下墙的应力分布类似于梯形分布,最大值出现在挡墙的底部,最小值出现在挡墙的中部。通过有限元数值分析法研究其受力变形特点,数值分析表明：二级挡土墙卸荷作用比较明显,且土自重在二级挡墙中得到了充分的利用;挡土墙主动土压力分布与模拟结果基本一致。     

考虑墙后填土强度各向异性的主动土压力计算方法

基于水平层分析法,假定不同方向滑裂面上的内摩擦角随该滑裂面与沉积面之间的夹角变化,提出了一种考虑材料各向异性的主动土压力计算方法.通过4个典型算例,讨论了墙后填土强度各向异性程度对主动土压力的影响.计算结果表明,随墙后填土沉积面与水平方向夹角增加,主动土压力逐渐变大,其合力作用点逐渐下降;随填土面倾角增加,各向异性影响逐渐增强.     

柔性材料新型挡土墙的有限元分析

为了研究柔性材料新型挡墙墙背土压力的空间规律、土压力影响因素以及玄武岩纤维拉结绳拉力的变化规律,设计了数值模型,利用ABAQUS进行了有限元模拟和对比分析。研究结果表明:挡土墙水平土压力大致呈抛物线分布,挡墙中下部位置处土压力增大,因此应该加强该类挡土墙中底部的玄武岩纤维拉结绳配置设计。结论可为柔性材料新型挡土墙在公路建设、水利建设、边坡支护工程中大面积的的推广和应用提供理论借鉴。     

台阶式高边坡加肋土挡墙变形特征的有限元分析

为了研究面板仰角对台阶式高边坡加肋土挡墙受力及变形特性的影响,以实际工程为研究背景,主要考虑了3种不同面板仰角的台阶式加肋土挡墙,通过引入肋-土、土-面板接触单元,利用有限元软件Ansys建立二维模型,对其进行数值模拟计算分析。分析结果表明:当改变面板仰角时,其对台阶式加肋土挡墙的墙面变形情况、墙顶沉降以及基底受压情况产生了较大影响。     

挡土墙主动土压力分布研究

基于极限平衡理论,利用单元分层法分别讨论了墙后无开挖回填和有开挖回填不同工况条件下的挡土墙土压力分布形式,推导出不同工况条件下的主动土压力强度及主动土压力系数理论公式.结果表明,墙后无开挖回填工况条件下墙背主动土压力沿墙高成线性分布;墙后有开挖回填工况条件下墙背土压力沿墙高成非线性分布.     

土压力计算中条间力函数的选取

极限平衡条分法计算挡土结构土压力时需要选取合适的条间力函数，目前采用的条间力函数具有理论缺陷，对此，选用4种条间力函数进行了实例计算，表明4种形式的条间力函数，可用于主被动土压力计算。研究还表明，只要满足端部条件，土压力值对条间力函数选取不甚敏感；另外，土压力合力作用点位置对主动上压力值影响较小，而对被动土压力值影响较大。     

条形荷载作用下主动土压力解析解

基于经典库伦理论,建立在条形荷载作用下滑动土楔体处于主动极限状态时的静力平衡模型。按微分学求极值的方法,导出了滑裂角解析解;以力系及力矩系平衡条件,推出了主动土压力及其作用点位置解析解;通过单因素及多因素影响分析法,明确了荷载参数、土体参数与土压力值及其作用点位置之间彼此影响,以及相互制约的规律。为研究露天矿边坡工程中重力式挡土结构的设计及主动土压力计算提供了理论依据。     

考虑土拱效应的倾斜挡墙土压力研究

针对现有主要研究竖直挡墙间土压力,而缺少研究倾斜挡墙间土压力的现状,研究了具有一定倾斜角度的挡墙土压力。通过假定挡墙与水平面呈夹角α,对挡墙间土体沿竖向取水平薄层作为微分单元体,通过作用在单元体上的水平力和竖向力的平衡条件,得到考虑土拱效应及倾斜角度的挡墙土压力理论公式,及对应不同倾斜角度和摩擦角的系数Kw计算公式,并与Handy理论土压力公式进行了比较分析。结果表明：当墙体竖直时,本文公式与Handy理论公式得到的结果一致。倾斜角度越小,竖向应力值越小,而挡墙上土压力值则越大,土拱效应发挥效果越好;Kw随着摩擦角的增大而增大,随内摩擦角的增大而减小。Kw与K′之间的差值随着内摩擦角、摩擦角的增大而增大,随倾斜角度的增大则减小,当墙体非竖直时,采用侧压力系数K′计算挡墙上土压力值存在风险。     

采空区框架桥侧向土压力研究

为研究采空区框架桥侧墙所承受的侧向土压力随墙体高度及外摩擦角的变化规律,采用库伦土压力理论进行了理论分析,并得到结论:当框架桥位于压缩区时,侧墙土压力值在被动土压力和静止土压力间的某一值;当框架桥位于拉伸区时,其土压力值位于静止土压力和主动土压力之间。当侧墙外层比较平整时,其被动土压力较小,其主动土压力较大;当侧墙外层比较粗糙时,其被动土压力较大,其主动土压力也较小;静止压力大小不受影响。当侧墙较高,土压力较大,当侧墙较低,其土压力较小。     

水平地震力对非线性主动土压力上限解的影响

大多数关于主动土压力的计算都是基于线性摩尔库仑准则.然而,实际上几乎所有的土体材料均遵循非线性关系,线性只是其中一个特例.根据非线性破坏准则,运用拟静态法考虑地震作用,利用极限分析上限定理求得主动土压力上限解.通过切线法原理引进中间变量,对墙后土体建立相容速度场,根据外力功率与内部能量耗散率相等的原理求出土压力的目标函数与约束条件,最后采用序列二次规划算法对该问题进行优化,得出主动土压力的最大值.将结果与已有文献进行分析比较,证明了该方法的可靠性.数值分析结果显示:随着水平地震系数的增加,主动土压力有非线性增大的趋势;非线性系数对主动土压力也有明显影响.     

Market and recycling of NiMH battery

<正>Market status and future trend of NiMH battery1.Global market of small NiMH battery Global market size of small NiMH batteries declined year on year since 2011.The trend will continue to 2018,at the rate of 5%to 10%annually.Demand for small NiMH batteries will be stable gradually.Many electrical apparatuses are powered by the built-in lithium battery today,which is the main reason for the shrunk market of small NiMH batteries.But,for some products,small NiMH     

China rare earth market review

正September 1-10,2014 Affected by the National Day holiday,rare earth transaction was stagnant and the market showed a weak steady state.As there was no good news for downstream market,some products with flat demand would likely rally slightly for some time to     

Current situation and future trend of China rare earth luminescent material industry

<正>Rare earth luminescent material is one of the most important application sectors of rare earths.China enjoys the exceptional advantage to develop rare earth luminescent material for its abundant rare earth resources.After several decades'endeavor,China's rare earth luminescent material industry,headed by rare earth phosphor for lamp and LED and high efficient rare earth energy-saving light source,has been gradually developed into a scale industry.China has become a major production base of rare earth phosphor for lamps and rare earth     

China rare earth market review

正June 1~10,2014Rare earth market remained weak.Quoted price of rare earth products was similar to that in May.There was no sign of recovery in downstream market.The market of NdFeB magnetic materials and phosphor was depressed.Catalyst,polishing powder and ceramic industries remained inactive.Demand from downstream industry was soft.Consumers purchased on their needs.Suppliers had strong intention to sell.Prices of rare earth products     

2014 second batch of rare earth quota released

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Annual Report analysis of Chinese rare earth-related listed companies in 2013

<正>Chinese rare earth-related listed companies have published their 2013 annual reports.It can be understood from their reports that production and operation activities of Chinese rare earth-related companies were still heavily affected by macro economy and industrial policies.They basically followed the steps of national economy.In 2013,world economy recovered slowly but the economy     

Market opportunities and challenges for rare earth polishing powder

正1.Status of rare earth polishing powder Rare earth polishing powder with high content of cerium oxide began to replace iron oxide for glass polishing and became one of the key materials in glass polishing process since 1940.Compared with traditional iron oxide,rare earth polishing powder has many advantages,such as fast polishing rate,high polishing quality and long service life.It can achieve good surface quality and improve operation conditions.For example,in lens polishing,the polishing work that cerium     

Baotou Research Institute of Rare Earths developed a new RE alloy preparation technology

正Pyrometallurgy Laboratory of Baotou Research Institute of Rare Earths had independently developed a new preparation technology of rare earth alloy for NdFeB.The alloy can remarkably enhance the coercivity of NdFeB magnet but also evidently reduce the production cost of the magnet.The new master alloy was prepared in the kA pilot-scale electrolytic cell by the independent technology.The rare earth master alloy can be used as the raw material for NdFeB.Compared     

China rare earth market review

正November 21~30,2014Due to weak demand from downstream industries,transactions of rare earth in Chinese domestic market were inactive.It was difficult to sell any rare earth products except for dysprosium oxide and terbium oxide.Suppliers lost confidence in recent market.Demand for rare earth products was soft.Consumers continued to take a wait-and-see attitude.Rare earth export market remained slow.     

Galaxy Magnets achieved the net profit of 34.02 million yuan in the first six months of 2014

正Galaxy Magnet announced its financial results for the first half of 2014 on August 14.For the first six months ended on 30 June 2014,Galaxy Magnet achieved operation income of RMB 182.3 million,up8.40% over the same period of 2013,and the net profit attributable to the shareholders of the listed company of 34.02 million yuan,increasing 35.49% over the same period of last year.Stable performance increase was led by development of new customers and application market of magnets.