Wall building stiffness and strength effect on content sliding in Wellington seismic conditions

A numerical study of unobstructed content sliding within several low‐to‐midrise reinforced concrete cantilever wall buildings designed to Wellington conditions in New Zealand is performed to validate the belief that increasing a building's strength and/or stiffness would result in more severe sliding response. It was shown that contents within stronger buildings experienced larger sliding response. If the building was designed to be strong, the sliding response of contents with a friction coefficient of 0.1 was smaller in stiffer buildings compared with those in flexible buildings. However, the trends start reversing with an increase in friction coefficient or a decrease in building strength. Overall, content sliding is not necessarily more severe in stiffer buildings, and in many cases, the opposite is true. This study's findings were compared against an existing parametric equation for estimating the maximum sliding displacement. This equation, which was originally derived for contents located within elastic frame buildings, was found to be more efficient than considering total floor accelerations alone but was underconservative by a mean of 17% for yielding multistorey buildings. A design procedure considering content sliding using the parametric equation and an example are provided. Copyright © 2016 John Wiley & Sons, Ltd.     

A model of triple friction pendulum bearing for general geometric and frictional parameters

Current models describing the behavior for the triple friction pendulum (TFP) bearing are based on the assumption that the resultant force of the contact pressure acts at the center of each sliding surface. Accordingly, these models only rely on equilibrium in the horizontal direction to arrive at the equations describing its behavior. This is sufficient for most practical applications where certain constraints on the friction coefficient values apply as a direct consequence of equilibrium. This paper presents a revised model of behavior of the TFP bearing in which no assumptions are made on the location of the resultant forces at each sliding surface and no constraints on the values of the coefficient of friction are required, provided that all sliding surfaces are in full contact. To accomplish this, the number of degrees of freedom describing the behavior of the bearing is increased to include the location of the resultant force at each sliding surface and equations of moment equilibrium are introduced to relate these degrees of freedom to forces. Moreover, the inertia effects of each of the moving parts of the bearing are accounted for in the derivation of the equations describing its behavior. The model explicitly calculates the motion of each of the components of friction pendulum bearings so that any dependence of the coefficient of friction on the sliding velocity and temperature can be explicitly accounted for and calculations of heat flux and temperature increase at each sliding surface can be made. This paper presents (a) the development of the revised TFP bearing model, (b) the analytic solution for the force–displacement relations of two configurations of the TFP bearing, (c) a model that incorporates inertia effects of the TFP bearing components and other effects that are useful in advanced response history analysis, and (d) examples of implementation of the features of the presented model. Copyright © 2016 John Wiley & Sons, Ltd.     

滑动面倾斜时抗滑桩弹塑性区临界高度的计算

探讨了三峡库区滑坡治理滑面倾斜时抗滑桩桩前岩土体弹塑性区临界高度的计算模式。介绍了常用的确定抗滑桩嵌岩深度的工程地质法和强度控制法,剖析了抗滑桩设计的弹性理论和弹塑性理论,利用空间楔形体极限平衡理论,得出了滑面倾斜时桩前岩土体弹塑性区的临界高度计算公式,并且讨论了弹塑性区临界高度与滑面倾斜角度及岩体的强度参数之间的关系。以三峡库区万州区某滑坡为例,计算了桩前弹塑性区的临界高度,并总结出临界高度与滑面倾角及岩体的黏聚力呈指数分布关系,与岩体的抗力及岩体的内摩擦角呈线性分布关系的规律。根据这些规律可以对抗滑桩嵌岩深度进行修正,并适当地控制抗滑桩嵌岩段岩土体弹塑性区临界高度。     

单江拱坝右坝肩岩体变形稳定计算分析

用有限元计算了单江拱坝右坝肩岩体的变形,着重分析了断层F1对于坝肩岩体变形的影响。用极限分析方法,计算了断层、层面等结构面切割形成的块体的抗滑稳定安全系数。结果表明,在一定范围内断层F1对于坝肩岩体的变形具有很大的影响,块体不能满足规范规定的抗滑稳定要求,需要加固。并对加固方式提出了建议。     

某砂岩顺层挖方高边坡治理工程施工期变形特征与工程效果评价

为了研究砂岩顺层挖方高边坡支护工程施工期间及施工后的边坡变形规律和治理工程效果,文章依托北京某边坡支护项目,对边坡在施工过程中的锚索轴力及边坡位移进行监测分析,结果表明：锚索轴力变化主要分为加速损失阶段、波动阶段以及持续稳定趋变阶段;锚索轴力变化可以很好地反映坡体内力的变化情况;坡顶水平位移和竖向沉降的变化,可以反映边坡深层位移的变化规律和边坡的稳定性;框架预应力锚索抗滑桩组合支护体系应用于砂岩顺层挖方高边坡的支护时,具有较好的支护效果。采用有限元分析软件,模拟该砂岩顺层挖方高边坡的开挖支护过程发现：随着边坡的开挖,坡体位移沿着软弱滑动面向坡角发展,边坡稳定性降低。将监测结果与模拟结果对比分析,发现二者的变化趋势基本一致,证明了该边坡的支护体系能有效地控制边坡的变形。研究成果能为以后类似边坡的设计施工提供参考。     

公主坟15号院边坡变形分析及防治工程研究

2012年7.21特大暴雨期间,香山街道公主坟15号院边坡出现垮塌并造成了破坏,边坡亟需治理。本文介绍了该边坡的基本特征,分析了边坡的变形情况及影响因素并确定了边坡的破坏模式,并选用瑞典圆弧法评价了边坡的稳定性。根据边坡的实际情况,选择了适于土质边坡防治的新型支挡加固措施一格构锚固工程,并辅以挡土墙工程及绿化工程,作为边坡治理的工程措施。     

基于空间相关的地震前兆数据库的信息提取与数据更新方法

针对当前提取地震前兆数据易受到噪声干扰,且数据库中数据更新速度较慢的问题,提出基于空间相关的地震前兆数据库信息提取与数据更新方法。利用快速Myriad滤波器,引入滑动窗,选择窗口数据参与到计算中,将计算结果当作目前窗口滤波输出值,实现数据滤波,由此实现信息提取的去噪处理。依据初步滤波结果,将当前数据作为中心,并确定空间窗,在横向上进行相关数据统计。针对空间窗中各数据选取滑动时窗,并对其中的数据进行S变换,利用指数拟合的数据传输能力参数,获取缺失数据的填充修复参数。引入曲面加权函数对填充修复参数进行平滑,根据平滑之后的填充修复参数对S变换数据进行更新,实现空间相关下地震前兆数据库的数据更新。实验结果表明,所提方法的数据信噪比较高,数据更新时间较短。     

热水条件下透辉石的摩擦本构特征

为了研究下地壳主要造岩矿物之一的辉石在摩擦滑动中的力学性质,本文选择辉石中的透辉石作为实验样品,在约200 MPa有效正应力（30 MPa孔隙水压）及100~600℃的热水条件下进行了速度阶跃摩擦滑动实验,在滑动开始后将剪切滑动速率在0.122 μm·s^-1和1.22 μm·s^-1之间进行切换来确定摩擦滑动对速度变化的响应.通过实验发现：透辉石在102~200℃表现为速度强化,随着温度升高,在约215℃附近从速度强化转变为速度弱化.在310℃以上,速度弱化的程度受温度的影响不大,而且摩擦本构参数a值和b值随温度的变化趋势相同.对变形样品的显微观测发现,与其速度强化行为相对应的微观变形主要以数条平行的R1剪切为主,卸样时造成的裂纹集中在R1剪切内部,形态长而曲折;与其速度弱化行为相对应的断层泥内部,剪切带变窄且数量明显增加,在内部互相连接,在边界附近多发育B剪切,卸样时形成的裂纹大量存在于B剪切带与R1剪切附近,形态短且平直.

     

平面滑动型岩质边坡稳定性极限分析上限法

在极限分析理论框架体系的基础上,提出了平面滑动型岩质边坡极限分析上限法.该方法按照外力所做的功率等于内力所消耗的功率,即滑体处于极限状态时两功率相等的条件--虚功率方程,综合考虑作用在岩质边坡上的后缘裂缝静水压力、沿滑面扬压力、重力、水平地震作用力、锚固力等外力,按照强度折减法,推导得出了岩质边坡稳定性评价的极限分析上...     

滑坡前兆突变异常识别方法

将滑坡位移观测值时间序列视为非平稳随机过程, 采用建立系统的同态模型的方法提取短期异常 , 并给出了异常识别准则、有序度计算公式; 用一阶差分进行高通滤波的方法提取临滑异常并进行预测; 根据异常时刻组成的灾变日期集用灰色灾变模型进行预测。