粉喷桩加固软土地基的技术探讨

分析了粉喷桩加固软土地基的原理,探讨了粉喷桩的设计理论,介绍了粉体喷搅桩的施工,根据工程实例,对粉体喷搅桩加固软土地基进行了说明,以促进粉喷桩在软土地基加固中的应用。     

粉喷桩处理软土地基的地基承载力研究

分析了粉喷桩加固软土的机理，从粉喷桩的设计参数、单桩复合地基载荷试验及试验结果介绍了粉喷桩在工程实例中的具体应用，表明了粉喷桩加固软土技术的应用将越来越广泛。     

粉喷桩加固既有线旁软土地基技术

针对在既有铁路路基旁软土地基上新建路基会对既有路基产生牵引沉降的问题,通过京广铁路武昌至武昌南增建三、四线工程粉喷桩处理软土地基的成功实践,介绍了粉喷桩加固软基的施工要点、加固效果和各种检测手段,并通过与其他几种加固方法的比较,得出粉喷桩加固软土地基有广泛的应用前景。     

浅析2D工法地基处理技术

复合地基技术在软土地基处理上已有着大量的应用研究,不同的处理技术适用于不同的条件。软基处理中最为常用的是粉喷桩复合地基,该法对于工期紧,软土性质较差的地基有着较理想的处理效果,但是粉喷桩在处理软土地基中常出现一些问题。粉喷桩与排水固结法有机地结合起来,成为一种全新的软土地基处理技术-排水粉喷桩复合地基工法（简称2D工法）。比较粉喷桩处理软土地基,这种技术有效地解决了传统地基处理方法遇到的问题。现在复合地基处理技术已经日趋完善,排水粉喷桩复合地基处理技术处于起步阶段,各方面的理论都不够成熟,而且还没有很好应用于工程实践中,在以后地基处理技术的完善中一定能得到进一步的发展和广泛的应用。     

道路路基软基处理技术及应用

粉喷桩技术是通过一系列物理及化学作用,在短期内使原来的软土地基变成具有整体性、水稳定性和一定强度的加固土桩复合地基,从而提高地基承栽力,减小地基的沉降,达到加固地基的目的。结合某生态园道路软土地基处治的实例,简述粉喷桩技术在道路施工中的应用,着重介绍粉喷桩施工前的设计及施工工艺流程,提出了粉喷桩的质量控制要求。     

公路粉喷桩处理软土地基施工与检测方法探讨

结合江石一级公路工程探讨粉喷桩处理软土地基的施工工艺与检测方法,提出了粉喷桩施工注意事项,归纳了粉喷桩处理软土地基的优点,以推广粉喷桩在软土地基加固工程中的应用。     

粉喷桩复合地基在工程中的应用

本文结合工程实例，介绍了单层厂房的结构选型，粉喷桩复合地基在软土地基中的应用，粉喷桩复合地基的经济效益，桩长的计算及加固效果。     

深层搅拌水泥粉喷桩施工工法

深层搅拌水泥粉喷桩施工工法南京市住宅建设总公司１原理和特点深层搅拌水泥粉喷桩（简称深搅粉喷桩）是近年来新兴的一种软土地基改良加固方法。施工时，以钻头在桩位搅拌后将水泥干粉用压缩空气输入到软土中，强行拌合，使其充分吸收地下水并与地基土发生理化反应，形成...     

双向搅拌粉喷桩在深厚海相软土地基加固中的应用

软土在我国分布广泛,而粉喷桩技术是一种有效的软土地基加固方法。其中深厚海相软土地基具有工程性质差,地基加固时成桩难度大等特点,本文依托衢州至宁德铁路工程,通过海相软土路基进行粉喷桩加固地基试桩试验,探讨了双向搅拌粉喷桩的施工工艺,并分析了粉喷桩不同桩长在深厚海相软土地基加固过程中,成桩质量较好时的施工参数,以及施工技术要点和质量控制措施等,为粉喷桩技术更好的应用于工程实践提供参考和依据。     

粉喷桩加固桥头软土地基在公路工程中的应用

介绍了湖北省汉沙公路新滩东荆河大桥采用粉喷桩加固桥头软土地基的施工程序及检测项目、控制标准等,对地基处理前后的效果进行对比分析,指出其适用性,从而推广粉喷桩在软土路基施工中的应用.     

Variable-diameter deep mixing column for multi-layered soft ground improvement: Laboratory modeling and field application

Deep mixing columns are commonly employed for soft ground improvement. However, the diameter of a single conventional column is a constant and the area replacement ratio does not vary with depth. Hence, the conventional column is not the ideal solution for multi-layered soft grounds, where different layers have remarkably different soil properties. Accordingly, this study proposes a better solution, which is the variable-diameter deep mixing column with a large diameter in the soil layer having high compressibility and a small diameter in the soil layer having relatively low compressibility. In this study, small-scale laboratory model tests were firstly employed to compare the performance of two-layered soft grounds improved by a variable-diameter column and a conventional column. The additional vertical stress in the soil and the column, the excess pore water pressure, and the ground settlement were analyzed. Then, a field application of variable-diameter columns for multi-layered soft ground improvement was presented; the design considerations, column installation, and monitored settlement were introduced and analyzed. The results indicated that the additional stress in the soil and the column in the highly compressible soil layer were much lower in the variable-diameter column-improved ground than in the conventional column-improved ground. Consequently, the variable-diameter column-improved ground yielded less total settlement and less post-construction settlement compared to the conventional column-improved ground.     

排水板复合框架自钻胎串式锚杆支护结构的工作机制分析

针对软土地区的深基坑工程降水与支护问题,提出排水板复合框架自钻胎串式锚杆新型支护结构,对其结构构成和工作机制进行详细探讨。基于柱孔扩张理论,推导出自钻胎串式锚杆在孔压影响下的承载力计算公式,采用数值软件ADINA对排水板的降水效果及其对自钻胎串式锚杆抗拔承载力的影响规律进行分析,最后将承载力模拟值与理论值进行对比。结果表明:(1)排水板具有良好的降水效果,能够快速有效地消散掉含水层土体的孔隙水压力。(2)通过与无排水板的工况进行对比,得出排水板降水措施能够有效减小锚杆轴力和框架柱的水平位移。(3)排水板能够及时消散胎体膨胀引起的超孔隙水压力,随着孔压消散,土体沿锚杆轴向产生的位移和应变降低,锚杆的抗拔承载力得到提高。(4)抗拔承载力理论公式计算值与模拟值基本吻合,验证了承载力计算公式的正确性。     

软土地基孔隙水压力降低引起的压缩分析

根据土力学基本原理,分析孔隙水压力降低引起的土体压缩方式,并对真空预压地基的分层沉降现场实测值和理论计算值进行分析;同时,定量分析真空预压地基在不同深处单位压缩量。研究结果表明:(1)若按有效应力原理水土压力分开计算、地基土体中孔隙水压力降低时,土体竖向总应力维持不变而侧向总应力减小;(2)土体中孔隙水压力在相对压强小于0的范围内降低时,将引起土体等向压缩,在相对压强大于0的范围内降低时,将引起土体单向压缩;(3)南沙港区的真空预压地基若其沉降按欠固结计算时,计算值与实测值接近,自重应力欠固结引起的沉降是抽真空期间地基总沉降主要部分;(4)真空预压的加固深度随排水体深度增加而增大,土层压密效果随地层深度增加而减弱,故降低孔隙水压力法在加固软土地基中,设计排水体深度时应考虑最佳加固深度。     

Effect of clogging of stone column on drainage capacity during soil liquefaction

Stone columns act as vertical drains, and due to their high permeability, allow for the quick dissipation of earthquake induced excess pore water pressure. When water flows through a loose sandy soil, it washes away fine soil particles. The fine sand particles get detached when the hydrodynamic force applied on the soil particles breaks the inter particle bonds between soil grains. These detached soil particles are then migrated by the seepage water. Based on the concentration of the soil particles in the seepage water, these may be captured at the pore constriction of gravels during the flow of water through the stone column. Thus, the clogging of stone column initiates which reduces of the permeability of column. The rate of dissipation of pore water pressure during earthquake is affected due to the clogging of column. In this paper, a mathematical model is proposed to determine the rate of dissipation of pore water pressure of stone column-reinforced ground by considering the clogging effect of column. The result obtained from the proposed model is verified with the available in-situ experimental data. A parametric study is also performed to investigate the effect of different parameters of the proposed model on the clogging of stone column. It is observed that when the permeability ratio, compressibility ratio and area ratio decrease, the possibility of clogging increases. The peak value of the excess pore water pressure ratio can increase up to around 50% due to clogging.     

MJS桩加固对上覆地铁运营隧道影响研究

以长沙地铁4号线下穿2号线运营隧道MJS水平桩加固工程为背景,对MJS水平桩施工期间周围地层孔压、2号线隧道附加应力、竖向位移进行监测分析,获得MJS水平桩施工对周围地层及运营隧道的影响规律。研究表明:MJS水平桩在钻孔期间,对周边地层孔压及隧道受力变形基本无影响;喷浆期间周围地层孔压增量随距离增加线性减小,隧道附加应力和竖向位移有明显变化,最大分别达到1.8 MPa和5.42 mm,但管片受力变形均处于允许范围内。表明MJS桩施工期间,隧道处于安全状态,研究可为类似工程提供参考。     

双向搅拌桩加固高速公路软土地基现场对比试验研究

 针对国内水泥土搅拌桩施工工艺存在的问题,提出了双向水泥土搅拌桩技术。为了分析双向搅拌桩加固高速公路软土地基的处理效果,在同一场地进行了双向搅拌桩和常规搅拌桩试验段工程,对比分析了双向搅拌桩和常规搅拌桩的桩身质量、施工扰动、复合地基承载力和路堤荷载下的工作性状特点。现场试验结果表明,双向搅拌技术能有效地提高搅拌均匀性、消除冒浆现象,并减小搅拌桩施工对桩周土体的扰动;双向搅拌桩桩身质量均匀,桩身强度沿深度变化较小,复合地基承载力高于常规搅拌桩复合地基;填土高度相近时,双向搅拌桩荷载分担比高于常规搅拌桩,地表沉降和坡角处最大水平位移小于常规搅拌桩复合地基,而地基固结速率快于常规搅拌桩复合地基。研究结果表明,双向搅拌桩在高速公路软土地基处理工程中具有很好的应用前景。     

软土地区粉喷桩施工工艺分析

介绍了粉喷桩的施工工艺,并重点讨论了软土地区中粉喷桩施工的注意事项,同时给出了相关的质量检测方法,为此类工程的施工建设提供了有意义的指导作用。     

Instability of a geogrid reinforced soil wall on thick soft Shanghai clay with prefabricated vertical drains: A case study

A 7.6 m high geogrid reinforced soil retaining wall (RSW) was constructed at the end of an embankment on very thick, soft Shanghai clay with 12 m deep prefabricated vertical drains (PVDs). The settlement of the ground, the wall movement and pore water pressure were monitored during the construction. From day 118, halfway through the construction, unexpected pore water pressure increment was recorded from the pore water pressure meters installed in the PVD drained zone indicating a possible malfunction of the PVDs due to large deformation in the ground. After the last loading stage, on day 190, a sudden horizontal movement at the toe was observed, followed by an arc shaped crack on the embankment surface at the end of the reinforced backfill zones. The wall was analyzed with a coupled mechanical and hydraulic finite element (FE) model. The analysis considered two scenarios: one with PVDs fully functional, and the second one with PVD failure after day 118 by manually deactivating the PVDs in the FE model. The comparison between the measured and simulated ground settlement, toe movement, and pore water pressure supported the assumption on the malfunction of the PVDs. It is believed that the general sliding failure in the wall was caused by the increase of pore water pressure in the foundation soil and soils in front of the toe. It is suggested that possible failure of PVDs should be considered in the design of such structures, and the discharge rate of the PVDs and the pore water pressure should be closely monitored during the construction of high soil walls on soft soils to update the stability of the structures, especially for grounds where large deformations are expected which may cause the failure of the PVDs.     

长板–短桩工法处理高速公路软土地基的数值分析

长板–短桩工法综合了排水固结法和水泥土搅拌桩法在加固软土地基工程中的优点,适用于处理高速公路深厚软土地基。以江苏省淮安–盐城高速公路盐城试验段为原型和依据,利用Plaxis软件,针对长板–短桩工法、排水固结法和水泥土搅拌桩法三种工况下的路堤和地基性状进行了二维有限元计算分析。从数值分析的角度研究了长板–短桩复合地基的加固机理和特性,进一步认识了总沉降、分层沉降、侧向位移、潜在滑动面及超孔隙水压力等指标的特征,得到了一些有益的结论。     

堆载预压下砂井地基固结有限元分析

采用砂井地基平面应变等效方法,结合ABAQUS软件对堆载预压下地基的侧向位移、沉降及孔压分布进行有限元模拟,并分析计算值与实测值之间的差异;计算结果能很好地预测砂井地基位移与孔压的变化,可为地基处理的设计提供参考。