桩锚支挡结构体系挡板土压力试验研究

以重庆地区常见的桩锚枝挡结构体系挡板上土压力为研究对象,采用室内模型试验方法,定性的分析了挡板上土压力分布规律,并将其与经典土压力理论计算结果作对比,从而指出了经典土压力理论在桩锚支挡结构体系挡板土压力计算中的不适用性。     

轻型支挡结构的土压力试验分析

以某高速公路轻型支挡结构监测项目为依托，分析研究了锚拉式柱板墙墙背土压力的分布规律，其成果和结论可为高速公路支挡结构设计和土压力理论研究提供参考。     

单锚预应力支挡结构锚杆设置的相互作用分析

本文运用数值模拟试验对单锚式预应力支挡结构锚杆设置参数进行了分析,探讨了锚杆设置的位置、倾角及预应力大小与墙体位移、土压力和支挡结构内力等因素的相互作用关系,所得结论可供设计单锚式预应力支挡结构参考。     

挡土结构侧土压力与水平位移关系的试验研究

目前挡土结构侧土压力计算方法中,一般未考虑挡土结构位移对土压力的影响。而控制挡土结构位移,使土体不能达互极限平衡状态,正是实际基坑工程中的常见情况。本文通过一定数量的室内模型试验研究,对不同挡土结构位移下,侧土压力由静止土压力逐步向主动土压力发展过程进行了测定,得出挡土结构位移和侧土压力强度值间的关系,提出了一种考虑挡土结构侧向位移的侧土压力简化计算方法。     

常用支挡结构形式与应用

本文简要对现今常用的一些支挡结构形式作了介绍,重点对未来支挡结构的发展趋势和在各类工程实践中的应用进行了分析。     

两种支挡结构的实测和计算土压力

对一座锚拉式桩板墙和一座楔形钢筋混凝土块拉筋加筋土挡墙,将原型观测、有限元计算、理论计算得到的土压力进行分析和比较,所得结论可供设计类似支挡结构时计算土压力参考。     

计算柔性支挡结构主动土压力的简化方法

对于柔性支护挡土墙,在计算土压力时,宜考虑土压力作用点位置对其计算数值的影响。提出一个建立在Bishop法基础上的简化法。当土压力作用点位置为下三分点时,计算成果可无一例外地收敛到经典的库仑理论值。作用点位置为墙高中点时,经算例分析,主动土压力相应下三分点时的数值增加了15%左右。     

地下增层h型双排桩支挡体系模型试验研究

针对地下增层基坑支护问题,提出既有-新增排桩组成的h型双排桩支挡体系.建立室内大比尺模型试验,以排间距为参数,研究h型双排桩中既有和新增排桩桩身受力随挖深变化规律.结果 表明增挖施工时新增排桩上部出现正向弯矩,下部出现负向弯矩.一定范围内,排间距增加可优化新增排桩桩身受力状态;既有和新增排桩可互相分担荷载,提高支挡结构...     

密排灌注桩支挡结构的优化设计

某电厂取水泵房位于甬江边，西北面紧挨电厂制氢站，西面靠近甬江航标灯（图１）。由于稳定的需要，泵房四周设永久性流水通道。为避免制氢站和航标灯搬迁，减少开挖影响，综合考虑地质条件等因素，护岸采用密排灌注桩挡墙方案。由于挡墙外侧距航标灯仅２m，与制氢罐的最近距离为１４．５m，因此减小桩顶位移以保护周围建筑物是挡墙设计的关键。１工程地质条件各土层主要物理力学参数见表１。２结构方案优化基坑围护工程中，减小桩顶位移的常用方法有设内支撑或土层锚杆等，本工程由于场地狭窄、土质软弱均无法实施，故从平面布置、结构形式…     

微型钢管排桩支挡结构原型试验研究

由于微型钢管排桩缺乏系统试验研究,严重制约了该新型结构的推广应用。通过3组不同组合的钢管排桩原型结构堆载试验,获取了加载至极限破坏过程的桩土变形、桩身应变、土压力等实测数据,总结了该支挡结构受力、变形规律,分析了钢管桩排数、排距、间距对承载能力的影响特征,得到了推力作用下各排桩承受土压力比值。试验成果为微型钢管排桩的理论分析和工程应用提供了较系统的基础资料。     

黄土地区某土钉支护结构测试分析

通过对黄土地区某一土钉支护结构工程实例的现场实测,分析了不同排土钉之间及同排土钉不同长度处的受力特征以及土钉支护结构变形的时间及空间效应,并同以往的实验结果进行了比较,指出了黄土地区土钉支护结构的受力及变形特点：（1）中下排的土钉轴力较上排的大;（2）土钉强度发挥沿钉长并不均匀,其轴力的最大值出现在土钉的中后部,土钉端部的轴力很小,土钉轴力开始阶段增长趋势平缓,约在钉长1／3处出现拐点,到达极值点后急剧下降,与以往测得的弓形轴力分布稍有不同;（3）土钉最大轴力出现在朗肯破坏面附近;（4）变形主要发生在开挖结束、支护尚未完成阶段;（5）沿基坑边沿,呈现中间变形大、两端变形小的特征。实验及分析结果为黄土地区土钉支护结构的设计及注意事项提供了参考依据。     

钢管混凝土结构地震模拟试验研究

对钢管混凝土 5层框架结构进行了地震模拟试验 .通过振动台试验及理论分析 ,对钢管混凝土结构的动力特性、多种地震波输入下的结构加速反应和位移反应进行了对比 ,综合评定了钢管混凝土结构的抗震性能 ,为结构设计提供了参考数据     

饱和砂土挡墙被动破坏超孔隙水压力试验研究

通过自制饱和砂土挡墙模型箱,对于不同挡墙位移模式和位移大小,测试了不同相对密度饱和砂土挡墙被动破坏过程中超孔隙水压力,揭示了饱和砂土挡墙后砂土破坏机理。对深入研究土与挡墙共同作用具有理论价值,对更加合理设计挡墙、控制稳定具有指导意义。     

基坑分级支护的模型试验研究

对大面积基坑,条件适当时采用多级支护可以取消水平支撑,目前已经有一些应用。而针对多级支护工作机理的研究却相对较少。进行了大型模型试验,研究了两级支护间土体水平距离B及第二级支护桩桩长L_2这两个主要参数对多级支护变形、受力及破坏模式的影响。根据B的不同,多级支护存在整体式、关联式和分离式三种破坏模式,3种破坏模式的主要区别在于破坏面的范围及两级支护间土体的应力状态不同。第一级桩的桩顶位移及桩身弯矩分别随B的增加而减小,基坑稳定性增加。而L_2的增加会导致第二级桩转变为主要受力结构,即第二级桩承受更大的弯矩,两级桩桩身弯矩分配更加均匀,L_2的增加同样有利于减小第一级桩桩顶位移。     

Experimental investigation of structure vulnerabilities to firebrand showers

Attempting to experimentally quantify the vulnerabilities of structures to ignition from firebrand showers has remained elusive. The coupling of two facilities has begun to unravel this difficult problem. The NIST Firebrand Generator (NIST Dragon) is an experimental device that can generate a firebrand shower in a safe and repeatable fashion. Since wind plays a critical role in the spread of WUI fires in the USA and urban fires in Japan, NIST has established collaboration with the Building Research Institute (BRI) in Japan. BRI maintains one of the only full scale wind tunnel facilities in the world designed specifically for fire experimentation; the Fire Research Wind Tunnel Facility (FRWTF). The present investigation is aimed at extensively quantifying firebrand penetration through building vents using full scale tests. A structure was placed inside the FRWTF and firebrand showers were directed at the structure using the NIST Dragon. The structure was fitted with a generic building vent, consisting of only a frame fitted with a metal mesh. Six different mesh sizes openings were used for testing. Behind the mesh, four different materials were placed to ascertain whether the firebrands that were able to penetrate the building mesh assembly could ignite these materials. Reduced scale test methods afford the capability to test new vent technologies and may serve as the basis for new standard testing methodologies. As a result, a new experimental facility developed at NIST is presented and is known as the NIST Dragon's LAIR (Lofting and Ignition Research). The NIST Dragon's LAIR has been developed to simulate a wind driven firebrand attack at reduced scale. The facility consists of a reduced scale Firebrand Generator (Baby Dragon) coupled to a bench scale wind tunnel. Finally, a series of full scale experiments were conducted to visualize the flow of firebrands around obstacles placed downstream of the NIST Dragon. Firebrands were observed to accumulate in front of these obstacles at a stagnation plane, as was observed when the structure was used for firebrand penetration through building vent experiments, due to flow recirculation. The accumulation of firebrands at a stagnation plane presents a severe threat to ignitable materials placed near structures.     

Experimental investigation of a reinforced soil retaining wall with a flexible geogrid-wrapped ecological bag facing

This paper presented a field study of the reinforced soil wall (RSW) with a geogrid wrap-around facing. In addition to the conventional monitoring content, the strain of the face-wrapping geogrid, which was neglected in most previous studies, was monitored during the construction process. The positional relationship between the maximum vertical earth pressure and horizontally laid geogrid strain was revealed by using the proposed oblique dragging effect. It was found that the strain on the face-wrapping geogrid occurred mainly in the early stage of construction. The oblique dragging effect existing in the flexible RSWs increased the vertical earth pressure and changed its distribution law, resulting in the position of the maximum vertical soil pressure appearing behind the position of the maximum horizontally laid geogrid strain. The horizontal earth pressure at different positions behind the wall was obviously lower than the theoretical result by using Rankine's theory. Also, a modified 0.3H method (where H refers to the wall height) was presented to account for the slope of the wall face, which could be used to determine the potential sliding surfaces for single-stage RSWs and two-tier RSWs with small offset.     

集热挡水板应用效果的试验研究

搭建集热挡水板应用效果测试平台,设计12种实验场景,对比同一水平处集热罩内、外和顶棚处烟气的温度,研究火源位置、安装高度对集热罩集热效果的影响规律,并测试不同形状、面积和边缘厚度集热罩的集热效果。研究结果表明:火源位于集热罩正下方时,集热罩集热效果明显;随顶棚高度的增加集热罩集热效果减弱;圆形集热罩的效果较好。