浅议CFG桩复合地基及其应用

笔者运用CFG桩的作用机理，通过CFG桩复合地基处理方法解决了通州区某天然地基标准承载力较低、不满足设计要求、又无其它有效方法解决的地基处理工程问题，阐明CFG桩复合地基为目前城市地基处理工程中地基土饱和、挤密差、天然地基承载力低等特殊情况下较先进、实用、有效的地基处理方法。     

干振碎石桩复合地基处理及其效果

干振碎石桩是处理松软地基土的一种行之有效的方法，它是挤密桩的一种。新乡市地方铁路处仓库场地经干振碎石桩地基处理后，桩间土密实度有明显的提高，液化指数大幅度降低，复合地基承载力相应提高，满足了设计要求。     

强夯处理湿陷性黄土地基效果浅析

强夯是处理湿陷性黄土地基的一种有效方法。灵宝市委市政府办公大楼湿陷性黄土地基，经强夯处理后，地基土孔隙比和压缩系数降低，干密度提高，湿陷性被消除，地基承载力大幅度提高并满足了建筑设计基础底面压力２２０ｋＰａ／ｍ２的要求。     

振冲碎石桩处理黄土地基的效果分析

振冲碎石桩在不同的地基中有不同的作用,本文就某热电厂工程中用振冲碎石桩处理湿陷性黄土地基,消除地基的湿陷性;处理饱和(软)黄土地基,提高其承载能力,以及用振冲桩消除地基中饱和粉细砂的振动液化等效果,用试验和理论计算加以分析和讨论。     

水泥粉体深层喷射搅拌桩复合地基处理及其效果

水泥粉体深层喷射搅拌桩与干振碎石桩〔１〕、干振灰土桩等一样,也是处理松软地基土的一种有效方法。但与干振碎石桩等其他挤密型复合地基处理方法不同,水泥粉体深层喷射搅拌桩属于摩擦桩型。由于天然地基土对桩体的侧摩擦力和端阻力的共同作用,使复合地基的承载力大幅度提高。然而人们普遍认为,水泥粉体深层喷射搅拌桩法复合地基处理不能解决场地土的液化问题。本文通过工程实例和瑞雷波检测结果,证实了该方法处理的复合地基,除了承载力有较大幅度的提高外,地基土的抗液化能力也可以得到相应的加强。     

大同--运城高速公路某软基复合地基检测结果分析

以山西大运高速公路某段软基处理为例,从挤密碎石桩的加固机理和破坏方式入手,通过对软基复合地基的原位测试结果分析,得出碎石桩不但提高了地基的承载力,增加了桩间土的强度,减少了地基沉降,而且消除或减轻了地基的液化,使复合地基承载力达到了设计要求,特别是为以后在高速公路修筑中的软基处理提供了参考资料.     

黄土地基群桩效应的有限元分析

利用有限元法考虑桩土的变形协调 ,分析了在黄土地基中承台 -桩 -桩间土共同作用的机理 ,得到了若干规律 ,对实际工程设计具有实用意义和参考价值     

海洋软黏土大直径沉桩贯入挤土效应

【目的】研究海上沉桩贯入软土地基诱发的挤土效应。【方法】利用有限元大变形RITSS程序,通过大量的参数分析,对海洋地基桩基础贯入引起的挤土效应、土体破坏机理、周围土体的水平和隆起位移,以及挤土效应的影响范围展开系统研究。【结果】将数值模型与锥形桩(圆锥贯入仪)经典理论解进行比对,获得了较好的一致性。对大量数值仿真结果进行统计,获得在海洋地基中沉桩时土体的径向位移和垂直隆起高度的定量化描述,桩周土在1~3倍圆桩半径范围内最大水平位移为0.26R。【结论】提出关于水平位移和隆起高度的计算公式,能够预测沉桩对临近土体扰动的影响范围,能较为准确地评估多桩系统中沉桩对临近桩基础的影响。     

振动沉管碎石桩复合地基综合检测若干值得研究的岩土工程问题

近年来,振动沉管碎石挤密桩在处理饱和黄土地基方面得到了相当广泛的应用。本文通过对西安市某工程振动沉管碎石桩复合地基的综合检测,提出几个值得研究的岩土工程问题。     

关中地区饱和黄土工程地质特性

关中地区广泛分布着黄土地层,当地下水埋深较浅时,湿陷性黄土往往由于地下水的作用,常呈饱和状态的非湿陷性黄土,简称饱和黄土. 当该土层若作建筑物地基(持力层或下卧层)被利用时,就必须掌握其基本性质和工程特性. 根据关中地区部分饱和黄土资料,分析和论证了关中地区饱和黄土的基本物理力学性质和工程特性,目的为了正确合理地利用饱和黄土地基取得效益.     

Parameter analysis of composite pile foundation in bridge foundation

In the current theory of bridge foundation design,all of the loads above the cap are loaded by the pile,and the bearing capacity of the soil among piles is not taken into account.In order to analyze the bearing capacity of the soil among piles in bridge pile foundation,a model of pile foundation is established based on a bridge foundation which is under construction,and by the finite element analysis software ANSYS.According to the results of finite element analysis(FEA)and current bridge foundation design theory,a feasible composite pile foundation which can be applied in the design of bridge foundation,is recommended.Additionally,a number of modifications are made to the original design.It was confirmed that these modifications derived from numerical simulations can improve the performance of the foundation.     

Limit analysis method for active earth pressure on laggings between stabilizing piles

Stabilizing pile is a kind of earth shoring structure frequently used in slope engineering. When the piles have cantilever segments above the ground, laggings are usually installed to avoid collapse of soil between piles. Evaluating the earth pressure acting on laggings is of great importance in design process. Since laggings are usually less stiff than piles, the lateral pressure on lagging is much closer to active earth pressure. In order to estimate the lateral earth pressure on lagging more accurately, first, a model test of cantilever stabilizing pile and lagging systems was carried out. Then, basing the experimental results, a three-dimensional sliding wedge model was established. Last, the calculation process of the total active force on lagging is presented based on the kinematic approach of limit analysis. A comparison is made between the total active force on lagging calculated by the formula presented in this study and the force on a same-size rigid retaining wall obtained from Rankine's theory. It is found that the proposed method fits well with the experimental results. Parametric studies show that the total active force on lagging increases with the growth of the lagging height and the lagging clear span; while decreases as the soil internal friction angle and soil cohesion increase.     

灌注桩基础工程质量事故的处理

灌注桩基础是珠江三角洲地区工业与民用建筑广泛采用的基础形式之一,但由于各种原因,发生质量问题的灌注桩基础屡见不鲜.本文简明地介绍了灌注桩基础工程质量事故概况、灌注桩质量检测和评价方法以及灌注桩质量事故处理的常用方法.     

Displacement characteristic of landslides reinforced with flexible piles: field and physical model test

A field monitoring system was established in an active river bank landslide in the Three Gorges area, China, and a consecutive monitoring for about 5 years were conducted to understand the displacement characteristics of flexible piles and the surrounding soil. It was found that piles deformed elastically under reservoir operation, and the soil in front of piles was gradually separated from piles. The movement of the pile heads exceeded that of the soil between and behind piles. This phenomenon was further studied by a large-scale physical model test to gain insights into the pile-soil interaction. The displacement relationship between pile heads and the surrounding soil is in good agreement with the field data. The physical model test shows that the deformation process of pile-reinforced landslides can be divided into two stages: firstly, when the piles head movement exceeds soil movement, the soil arching is mainly affected by the deflection of the piles, the arches between and behind piles bent upwards;but when the soil movement exceeds piles head movement, the arches near the upslope and downslope bent downwards and upwards, respectively. Furthermore, the different deformation of two adjacent piles and the pile stiffness influenced the arch’s shape and formation;the flexible piles exhibit great coordinated deformation with the landslide, and caused the soil arch on the downslope.     

陕南膨胀土加灰改良的试验研究

陕南膨胀土分布地区由于膨胀土地基的胀缩变形，常常导致建筑物开裂和毁坏。如何改良膨胀土，消除其胀缩性，加固膨胀土地基，确保工程建筑物的安全和稳定，是膨胀上分布地区工程建设实践中急待解决的重要课题。结合陕南三种类型的膨胀土，我们选取有代表性的试样进行了加灰（石灰、粉煤灰）处理的试验研究，其效果较好，消除或减弱了膨胀土的胀缩性，达到了改良膨胀上不良工程地质性质的目的．     

局部桩筏基础的设计与施工

以加拿大多伦多市某工程为例,介绍了在复杂地质条件下采用局部桩筏基础(PPRF)的设计及施工问题;探讨了设计PPRF的决定性因素;在保持PPRF设计的完整性前提下,提出了单位沉降量的准则,并用于筏板和桩的设计;计算了PPRF的滑移及转动;最后,采用有效方法对该工程采用的局部桩筏基础进行了计算分析.结果表明,PPRF的设计主要取决于侧向土压力、分布不均的建筑荷载以及地基土的非均匀承载力,工程桩应主要布置在沉降较大的区域,即位于筏板基础承受高压力而土体承载力较低的西北部.探讨局部桩筏基础的设计与施工为该类型工程的基础设计提供了一个新的解决途径.     

端承桩在常轴力作用下的地震反应分析

对分层弹性地基中端承桩基础按ｗｉｎｋｌｅｒ（温克尔）地基土模型并通过特性分析建立了合理的力学模型。经过动力分析，给出了端承桩横向自振特性及在常轴力与横向地震载荷作用下强迫反应解析解，为具有常轴力与横向地震载荷作用下的无限层弹性地基中端承桩的动力反应分析提供了一种新的解析方法。     

拟建海堤的选型及其对邻近桥墩的影响

基于深圳市大铲湾(宝安中心区段)海堤(西侧)工程与深圳市沿江高速公路桥桩工程,通过对抛石海堤排水固结处理软基、大袋砂海堤排水固结处理软基、抛石海堤爆破处理软基、抛石海堤挖淤处理软基等4种不同类型海堤的基本结构型式及其技术特点进行对比,确定了拟建海堤(西侧)的结构型式;并基于FLAC软件数值模拟拟建海堤(西侧)施工刚完成时对沿江高速公路桥墩的影响.结果表明:拟建海堤(西侧)采用重力式斜坡堤,并使用大袋砂海堤排水固结处理软基方案比较合理;拟建海堤(西侧)施工刚完成时,离海堤边线40.8 m处的桥桩水平向最大位移约为7.5mm,离海堤边线176.8m处的桥桩水平向位移更小,显然拟建海堤(西侧)施工时对已建桥桩的影响甚微.