冲击碾压加固吹填粉细砂地基机理及应用

从砂土液化的角度研究冲击碾压技术加固粉细砂地基的实质,揭示了冲击碾压技术加固此类粉细砂地基的作用机理.通过对首钢曹妃甸吹填粉细砂地基处理中采用冲击碾压技术的工业实验资料和效果进行分析研究,证明使用冲击碾压技术加固粉细砂地基是可行的.     

软土地基贝雷片现浇梁预拱度的控制

温(州)福(州)铁路罗汉溪特大桥在软土地基上采用了原位贝雷片现浇箱梁预拱度的控制措施.由于软土地基沉降量较大,采用贝雷片桁架支架原位浇筑大体积梁片难度很大.为了能更好地控制梁片的预拱度,地基预压和桁架预压成为关键.因为地基、桁架的预压不仅关系到梁片预拱度的设置,更关系到梁片浇筑过程中的稳定和施工安全.     

浅析不良地基的加固处理策略

目前许多地基并不符合建筑的要求,而地基又是所有建筑物的最终荷载点,因此,应当根据具体条件,结合各种方法,对不良地基进行加固处理,使其满足建筑物对地基的要求,从而保障建筑工程后期的质量安全.     

深层搅拌桩在软土地基的应用

以建在软土地基上的商住楼采用深层搅拌桩为实例,对该施工工艺加固地基时在设计、施工方面的一些问题作了分析、研究,揭示了由复合地基载荷试验获得的复合地基承载力标准值和通过理论公式计算的复合地基承载力标准值的关系.     

“软弱地基”与“重载地面”的结构设计

分析了软弱地基形成的原因,针对软弱地基根据相关专业规范,考虑减轻软弱地基对重载地坪的影响,提出了一些软弱地基的处理方法,满足了工程的质量要求,对跨专业设计是一种尝试和设计经验的积累.     

预应力高强混凝土管桩在沿海软土地基处理中的应用

采用锤击法施工工艺,高强度混凝土预应力管桩PHc桩加固软土地基,提高地基承载力.     

后压浆技术在CFG桩地基处理工程中的应用

朔黄发展大厦工程采用CFG桩复合地基,并进行桩基的后压浆处理,不仅提高了复合地基的承载力,而且缩短了桩长,加快了施工进度.经试验及时间检验,该工程地基处理效果良好,技术经济效益显著.结合该工程实例,介绍了CFG桩后压浆施工技术.     

振动沉管碎石挤密桩加固软土地基

对特殊地质条件下的盐渍土地基采取何种技术措施来解决三方面的技术难题,一是解决提高地基承载力,二是解决地基土的高压缩性及液化带来的基础沉降问题,三是解决土层中的高盐含量对混凝土和钢材的高强度腐蚀问题.本文采用振动沉管碎石挤密桩的方法对地基土进行了加固,取得了良好的效果.     

考虑侧填荷载的分离式基础涵洞地基承载力新算法和试验

为了研究涵侧填土对采用分离式基础涵洞地基承载力的提高效应,先结合基底土体的受力特点.进行受力分析,建立计算模型,构建求解分离式基础地基极限承载力的算法,给出承栽力表达式.然后在相似理论的指导下,设计了5组模型,试验模拟粉质黏土地基受荷变形直到破坏的全过程,绘出荷载一沉降曲线.测得涵侧填土高度为0、4、8、12、16 m时的地基极限承栽力.试验发现:随着侧填土高度的增加,承载力显著提高,当填土为12 m时已达到885 kPa;但提高幅度表现出非线性特性,先从18.42%增加到36.11%,然后减小到3.39%;当填土达到16 m时承载力达到915 kPa且不再增加;同时发现使用本文算法与试验实测值的误差小于10%,可以考虑用此算法计算分离式基础涵洞的地基极限承载力.继而得出结论:当涵洞地基沉降满足设计要求时,涵侧填土显著提高了地基承载力,节约工程造价,且提高的幅度先增加后减少,当达到16 m时地基承栽力便逐渐趋于915 kPa.     

冶金建筑考虑结构刚度时地基承载力的探讨

介绍了冶金工业建筑地基、基础与上部结构共同工作的概念,根据国内外的相关理论,考虑建筑物刚度与地基土共同作用,提出了新建建筑物地基承载力设计值的计算公式,并给出了公式的适用条件.     

Case Study of Degrading Permafrost beneath a Road Embankment

This paper reports on a case study of degrading permafrost beneath a road embankment in Northern Manitoba, Canada. Field measurements of ground temperatures for a three-year monitoring period have been used in calibrating the geothermal model developed to reproduce the conditions and trends in the subsurface thermal regime beneath the embankment. The numerical model was used to investigate the future ground thermal regime of the foundation and evaluate the potential impacts of embankment construction and climate change. Particular interest was paid to the foundation soil near the toe of embankment where relatively rapid permafrost degradation was occurring.     

易塌陷土地基桩基础负摩擦力的研究

为了尽可能准确地计算易塌陷土地基桩基础的负摩擦力,通过对易塌陷土地基桩基础负摩擦力成因的分析,计算出谦比希铜矿充填搅拌站桩基础负摩擦力和桩的极限承受力。与按国内计算湿陷性黄土地基桩极限承受力的方法所得的结果进行比较,桩的极限承受力提高了20%以上。工程费用明显节省。建成使用以来,基础沉降也完全符合设计要求。     

Kinematic Soil-Structure Interaction from Strong Motion Recordings

Earthquake strong motion recordings from 29 sites with instrumented structures and free-field accelerographs are used to evaluate variations between foundation-level and free-field ground motions. The focus of the paper is on buildings with surface and shallowly embedded foundations. The foundation/free-field ground motion variations are quantified in terms of frequency-dependent transmissibility function amplitude ∣H∣. Procedures are developed to fit to ∣H∣ analytical models for base slab averaging for the assumed conditions of a rigid base slab and a vertically propagating, incoherent incident wave field characterized by ground motion incoherence parameter κ. The limiting assumptions of the model are not strictly satisfied for actual structures, and the results of the identification are apparent κ values (denoted κa) that reflect not only incoherence effects, but also possible foundation flexibility and wave inclination effects. Nonetheless, a good correlation is found between κa values and soil shear wave velocity for sites with stiff foundation systems. Based on these results, recommendations are made for modifying free-field ground motions to estimate base slab motions for use in response analyses of buildings.     

Cyclic Softening of Low-Plasticity Clay and Its Effect on Seismic Foundation Performance

During the 1999 Chi-Chi Earthquake (Mw = 7.6), significant incidents of ground failure occurred in Wufeng, Taiwan, which experienced peak accelerations ～ 0.7?g. This paper describes the results of field investigations and analyses of a small region within Wufeng along an E–W trending line 350?m long. The east end of the line has single-story structures for which there was no evidence of ground failure. The west end of the line had three to six-story reinforced concrete structures that underwent differential settlement and foundation bearing failures. No ground failure was observed in the free field. Surficial soils consist of low-plasticity silty clays that extend to 8–12?m depth in the damaged area (west side), and 3–10?m depth in the undamaged area (east side). A significant fraction of the foundation soils at the site are liquefaction susceptible based on several recently proposed criteria, but the site performance cannot be explained by analysis in existing liquefaction frameworks. Accordingly, an alternative approach is used that accounts for the clayey nature of the foundation soils. Field and laboratory tests are used to evaluate the monotonic and cyclic shear resistance of the soil, which is compared to the cyclic demand placed on the soil by ground response and soil–structure interaction. Results of the analysis indicate a potential for cyclic softening and associated strength loss in foundation soils below the six-story buildings, which contributes to bearing capacity failures at the edges of the foundation. Similar analyses indicate high factors of safety in foundation soils below one-story buildings as well in the free field, which is consistent with the observed field performance.     

工程开挖地表移动变形预计的随机介质模型

地表移动变形预计及监测反馈是实现信息化施工、减少工程灾害发生的基础。随机介质理论属于非连续介质理论范畴,其预计模型在自重应力型矿山地表移动变形预计应用中取得了极大成功。在分析地表建（构）筑物移动变形等级及允许移动变形值基础上,研究随机介质理论拓广应用于构造应力型矿山、边坡与基坑工程、地下空间等开挖工程引起的地表移动变形预计的适应条件,并着重探讨基坑工程开挖引起的地表移动变形预计公式：疏水引起固结压缩而导致的地表移动变形,以及基坑工程开挖使侧壁失去支撑而引起的地表移动变形两种因素影响的叠加。     

鞍钢老工业基地旧房改造地基承载力的有效利用

分析、探讨了旧房地基承载力变化的影响因素、提高的幅度及确定方法,为鞍钢老工业旧房增层改造中有效利用原地基承载力提供理论依据。     

新时代水工环地质调查在地质灾害治理中的应用

目前,地质灾害的外在表现方式有很多种,比如地震、泥石流、地裂等等,这些都是比较常见的地质灾害类型,对此,需要采取有效的措施进行治理。在新的时代背景下,需要充分发挥出水土地质调查工作的重要性,从而提升地质灾害的治理质量,为我国社会的健康稳定发展奠定坚实基础。     

基坑开挖对临近地表沉降影响的分析

采用FLAC-3D软件对某基坑开挖引起的地表沉降进行了数值模拟,计算中采用摩尔库仑及修正剑桥弹塑性模型模拟土体特征,采用结构单元模拟基坑支护结构。通过模拟开挖过程,获得了地表沉降的一些规律,可供工程设计和施工参考。分析表明：土方开挖对基坑周围土体的影响范围约为2.7倍的基坑深度;修正剑桥模型模拟昆明地区典型地基土能取得较好效果。     

基坑施工中的地下水处理以及工程实例

介绍井点降水法在基坑施工中地下水处理的应用情况以及工程实例。     

中州氢氧化铝焙烧车间人工挖孔灌注桩设计

在铝工艺中,当设备布置集中,厂房高差较大,而地基又较复杂时,应正确确定地基基础方案,使其满足土建自身的强度、稳定要求,又符合工艺生产要求。通过中州铝厂焙烧车间的基础设计及试验,总结了适合该地区特点的基础形式,为后期工程应用提供了科学、可靠的依据。