Study on swelling properties of an expansive soil deposit in Saskatchewan, Canada

The main objective of this paper was to study the swelling properties of Regina clay. The deposit comprises a topsoil (surface to 0.3 m depth), an expansive clay (0.3–8 m), and a bottom till (8–9 m). High liquid limit (70 ± 15 %) and plastic limit (33 ± 4 %) indicated high water retention and adsorption capacity for the clay. Irrespective of the cover type (vegetation and cracked road), the field water content in summer closely matched the plastic limit. The clay was characterized by medium-to-high swelling that was best predicted by SP = 0.16 (I _p)^1.188. The soil had 51 % clay minerals including smectite (32 %), illite (7 %), kaolinite (5 %), and chlorite (3 %). With a CEC of 40 cmol(+)/kg, Ca²⁺ and Mg²⁺ were found to be the main exchangeable cations: the specific surface area was 50 m²/g. The SP and P _s for a 1.2 m deep sample measured 12 % and 260 kPa, respectively, and the estimated surface heave of 180 mm gradually diminished to 3.6 m depth. These values matched well with consistency-based correlations.     

Prediction of lateral swelling pressure behind retaining structure with expansive soil as backfill

Lateral swelling pressure (LSP) develops in expansive soil when the volume expansion associated with water infiltration is restrained in the horizontal direction due to a rigid infrastructure. Various types of testing techniques, used to determine the LSP from both laboratory and field studies, are critically reviewed by focusing on two key factors, namely, the boundary conditions and the saturation path. Most testing techniques are capable of reasonably simulating the stress state of a soil element behind a retaining structure by applying a fixed boundary condition in the horizontal direction and a stress boundary condition in the vertical direction. However, they are only used to determine the LSP following a simple path, which is from an initially unsaturated state to a fully saturated state. In other words, these tests fail to provide information on the variation in LSP with respect to changes in the degree of saturation, the water content or the matric suction during the infiltration process. Furthermore, the literature review suggests that a reliable model for the prediction of the LSP during the infiltration process is not available. For this reason, a model is proposed in this paper to estimate the lateral earth pressure (LEP) considering the variation in LSP behind fixed rigid retaining structures with respect to the matric suction during the infiltration process. The proposed model is simple and only requires information, which includes the soil water characteristic curve (SWCC) and a limited number of soil properties. Data from one large-scale model test and two field case studies from published literature are used to illustrate and verify the proposed model. Reasonable comparisons are made between the predictions and the measured data. The proposed model will be a valuable tool for use in conventional engineering practice for the quick prediction of the increasing LEP behind retaining structures with expansive soils as backfill due to the development of LSP associated with water infiltration.     

南宁地区膨胀土膨胀力的现场测试

以广西南宁膨胀土为研究对象,考虑气象因素的影响,进行了现场膨胀力测试。测试场地设置桩和框锚结构,在土体中沿水平方向和垂直方向设置土压力盒,测试浅层土体水平向和竖向膨胀力,膨胀力的测试经历了一个完整的雨季。测试结果表明,土体膨胀力的变化与降雨入渗息息相关,"旱涝急转"的过程会造成土体膨胀力骤然变化,但雨季的持续又会对土体水平向和竖向膨胀力带来不同影响。现场对膨胀土竖向和水平向膨胀力的测试结果可为工程设计的优化提供参考。     

谈膨胀土工程特性及处治方法

介绍了膨胀土的相关工程特性及其分类办法,并对石灰处治、水泥处治、粉煤灰处治膨胀土等具体处治方法进行了介绍和分析,推荐了一种合理的膨胀土路基结构形式,并针对膨胀土问题自身的特点及其研究现状提出了今后膨胀土问题研究的发展方向。     

脱湿状态对膨胀土膨胀变形和强度特性的影响

非饱和膨胀土的脱湿状态对土中水分散失速率影响较大,不同的脱湿速率又会使膨胀土呈现不同的工程性状。通过控制恒温恒湿箱的温湿度工作参数,设置不同的脱湿环境制备土样,进行土工试验,深入认识脱湿状态对膨胀土膨胀变形和抗剪强度的影响。将饱和土样脱湿到设定的不同含水率,进行有荷载膨胀率试验,结果表明：在相对湿度越大的环境下,脱湿速率越小,土体膨胀率越大;起始含水率和上部荷载越小,土体膨胀变形越大。将不同起始含水率的土样膨胀完全后放入直剪仪,进行固结直剪试验,结果表明：脱湿到不同含水率的试样,脱湿速率越小,土体越密实膨胀后的抗剪强度越大;上部荷载存在可提高土体的抗剪强度,起始含水率越小上部荷载越大土样的抗剪强度越高。研究结果可为大气作用下膨胀土边坡的防护设计提供参考,有助于对自然气候环境下膨胀土边坡的灾变进行预警,并可优化膨胀土边坡的施工方案。     

基于膨胀力作用在膨胀土基坑支护设计中的应用研究

在成都地区膨胀土基坑支护设计时,考虑到膨胀土的胀缩影响,对膨胀土的抗剪强度参数进行大幅度的折减,且没有考虑膨胀土的力学性质对支护体系的作用。基于结构体系分析,提出将膨胀力等效为水平集中力作用于支护结构的计算方法,并与成都地区某膨胀土基坑支护设计实例对照,为膨胀土基坑支护设计提供一种新的计算方法。     

浅议膨胀土地基的工程设计与施工

从土的矿物成分及其联结状态和水分迁移角度对膨胀土产生显著胀缩性的机理进行分析,进而论述膨胀土的判别方法。针对建设工程中遇到的膨胀土,从工程设计与施工角度阐述了减小膨胀土胀缩性的措施,从而降低膨胀土对工程建设的危害。     

西--汉高速公路膨胀土胀缩指标试验研究

针对膨胀土的胀缩指标与含水量密切相关的问题,从无荷膨胀量、膨胀力、有荷膨胀量、收缩等方面的试验进行了研究,并得出了试验结论,为全面认识膨胀土的基础特性,提供了理论基础.     

掺石灰改良膨胀土的室内试验研究

针对膨胀土路基的改良问题,进行了一系列室内土工试验,对石灰以及石灰改良后膨胀土的基本物理性质、胀缩特性、击实特性、力学特性等进行了室内对比试验分析,结果表明,石灰改良膨胀土试样的强度主要取决于试样的含水率、掺灰率.     

谈膨胀土的地基处理

对膨胀土及其特性作了简要叙述,将膨胀土地基处理的一般原则作了总结,并结合工程实例,提出了膨胀土地基处理设计的工程措施,以供相关人员参考借鉴。     

呈贡隧道膨胀土膨胀力试验研究

选取呈贡隧道膨胀土重塑土样,通过膨胀力试验,研究了膨胀土在不同初始状态下的膨胀特性,探明了昆明膨胀土的膨胀力与初始含水量和干密度的内在联系,为昆明地区建筑物的设计与施工提供相关依据。     

纤维类材料改善膨胀土工程性能的适用性探讨

通过室内土工试验和数值模拟分析研究纤维类材料改良膨胀土的可行性和效果。结合室内试验结果,采用有限差分软件FLAC3D模拟均质膨胀土边坡和加FRP锚杆后的改良膨胀土边坡,并对二者进行了对比。室内土工试验表明,聚乙烯纤维能有效提高膨胀土的膨胀率和膨胀力以及显著降低纤维土的收缩性。数值模拟分析表明,纤维增强复合塑料能有效增加膨胀土边坡安全系数,减少滑动位移。     

Improvement of engineering properties of expansive soil using liming leather waste ash

Bulletin of Engineering Geology and the Environment - The expansive soils have always presented various challenges for geotechnical and civil engineers due to their low bearing capacity and high...     

膨胀土路堑边坡破坏研究

从膨胀土路堑边坡的破坏类型和机理出发,论述了膨胀土路堑边坡破坏的原因及处治时应考虑的因素,并对南昆铁路和云南楚大高速公路中出现的路堑边坡破坏问题进行了相关分析,提出了采用柔性支护技术处理膨胀土路堑边坡的思路。     

LCHH基于FLAC下的暴雨对弱膨胀土边坡稳定性影响的研究

结合室内弱膨胀土边坡实体模型试验所得数据,利用岩土工程数值分析软件FLAC,模拟分析南方强降雨条件下膨胀土边坡失稳问题,综合实体模型试验结果和软件数值模拟结果对比指出雨水对膨胀土边坡稳定性影响很大,提出膨胀土边坡加固治理建议和方法。     

Influence of moisture on soil swelling

The dependence of the relative swelling of soils on their initial moisture content and yield point is examined. Physical characteristics of six types of swelling soils are determined, and results of their testing in compression devices are also described. The swelling pattern of soils with different initial moisture contents and the relation to liquid limit are demonstrated; this makes it possible to predict the uplift of the surface of a bed. Translated from Osnovaniya, Fundamenty i Mekhanika Gruntov, No. 5, pp. 2–5, September–October, 1997.     

石灰对云南膨胀土力学特性影响的试验研究

选取云南省典型的湖相沉积型膨胀土土样,以石灰为改良剂对其进行化学改良,并对改良的膨胀土进行三轴剪切试验,结果表明,石灰改性土中石灰的最优掺量为5.5%,为工程实践中膨胀土改良提供了一定的依据。     

膨胀土边坡稳定性分析讨论

分析了膨胀土边坡失稳机理及其形式特点，重点讨论了现阶段常用的边坡稳定性分析方法，并指出了各方法的适用性及应注意的问题，对实际边坡工程的稳定性分析具有一定的指导意义。     

膨胀土填料改良试验研究

结合合宁线肥东试验段工程实践，从改良前后土的颗粒分析、物理性质、水理性质、强度试验和土的膨胀性指标测定等入手，着重阐述了石灰改良膨胀土的效果。     

新建云桂铁路膨胀岩膨胀特性试验研究

膨胀岩具有遇水膨胀、软化、崩解和失水收缩、开裂等特性,一直是工程应用中的难点.通过新建云桂铁路膨胀岩的室内试验研究,分析研究了膨胀岩在不同含水率条件下的变形特征和变形过程,进一步建立了膨胀岩的修正Huder-Amberg本构变形模型;根据测定同一膨胀岩在不同含水率状态下的试验成果,分析了膨胀岩在不同含水率状态下的膨胀应...