泡沫轻质土在宁海软土地基处理中的应用

泡沫轻质土具有轻质、环保、易施工等特性,在沿海地区的软土路基处理中得到广泛应用。对浙江宁海地区地基土特点进行分析,总结软土地基处理的关键点。通过方案比选,采用泡沫轻质土处理方案能有效减少对土基的附加应力,减小路基总沉降量,同时缩短施工工期。根据施工实测数据,工后沉降值和差异沉降均满足规范要求。对类似地区的软土路基处理具有一定的参考价值。     

软土基坑换填法支护施工技术研究

结合地质勘察报告对某工程地质情况进行分析,明确了工程的特点和难点,经过对多种基坑支护方案进行比较,选用了对软土边坡采用风化砂和石碴换填结合锚杆、土钉支护体系进行基坑边坡处理的施工方案,并对软土换填法基坑支护施工工艺进行了探讨.通过工后监测,该施工技术对处理软土基坑的边坡效果良好.     

现浇泡沫轻质土在改扩建工程设计中的应用

依托江苏省江都至广陵高速公路改扩建工程,基于我国研究现状,从设计角度对现浇泡沫轻质土路基和传统复合地基方案进行技术经济方面比选,并对现浇泡沫轻质土路基进行计算分析,得出的工后沉降和差异沉降成果均满足相关规范要求,采用现浇泡沫轻质土处理效果良好。     

杭州东站路基现浇泡沫轻质土监测研究

结合杭州东站软土路基地基处理及轻质土回填置换工程,选取某试验段,根据现场监测方案,来进行现场土压力和沉降变形监测,绘制了土压力和沉降变化曲线,分析得出现浇泡沫轻质土应用在铁路路基的土压力和沉降分布变化规律,同时,测定了其作为铁路路基基层材料在不同龄期的填料压实指标,为工程顺利完成提供依据。     

换填支护法在浅埋软土基坑工程中的应用

结合地勘报告对光电研发基地工程地质情况进行分析,明确了工程的特点和难点,经过对多种基坑支护方案进行比较,合理选用了对浅埋软土边坡采用风化砂和石渣换填结合锚杆、土钉支护体系进行基坑边坡处理的施工方案,并对该方案进行了理论分析及设计,给出了具体的施工工艺。通过工后监测,该施工技术对处理软土基坑的边坡效果良好。     

谈泡沫轻质土在昌九快速路改造工程中的应用

介绍了泡沫轻质土的特性及其在国内外的发展现状,从施工技术指标、配合比设计、施工要点等方面,阐述了泡沫轻质土在实际工程中的应用,指出泡沫轻质土可减少路基工后沉降,提高路基稳定性,值得推广应用。     

泡沫轻质土在软土地基高速公路中的应用探析

桥头跳车是软土地基高速路常见病害。为预防和应对此病害,可在软基路段台背路基填筑泡沫轻质土,改善传统搅拌桩处理软土地基模式,减少施工后的沉降量。本文论述了泡沫轻质土在软土地基高速公路中的应用。     

气泡混合轻质土在调整高速公路不均匀沉降中的应用

在软土地基上修建的高速公路,由于预压时间不足等原因,可能会造成通车后高速公路日沉降速率过大,路基发生不均匀沉降;为减小路基的剩余沉降,采用对路基横向引孔,并换填气泡混合轻质土进行处置;处置后路基沉降速率趋于稳定,剩余沉降明显减小,避免了因封锁高速公路进行施工带来的经济损失。通过对气泡混合轻质土的室内试验研究,并结合工程实例介绍其在已通车高速公路处置沉降中的应用,通过换填,路基荷载从74.2 kPa减至69.8 kPa,试验段月沉降速率减小50%左右,剩余工后沉降减小70%以上。     

轻质泡沫土在规划地铁上方填筑施工中的应用

结合上海中环线浦东段东段高架工程的施工实际,介绍在规划地铁位置上方进行桥后回填及道路抬高的方案选择,经计算比较,选择了轻质泡沫土作为回填材料,满足了轨道交通的荷载要求。通过对现浇轻质泡沫土的质量控制,大大减少了荷载,控制了沉降量,有效地推进了相关管线及后续工程的顺利实施。     

泡沫轻质土在台背回填中的应用及优势

为了解决沪南路(康花路—上南路)改建工程1标秀龙桥桥后填筑沉降,保证施工工期和环保性,避免桥台台背压实困难问题,在秀龙桥桥后回填工程采用泡沫轻质土填筑。以秀龙路桥后泡沫轻质土施工为例,介绍了泡沫轻质土工艺原理,工艺流程和施工要点等。采用泡沫轻质土施工加快了施工工期,有效解决工后沉降问题,有效缓解和消除桥头跳车现象,对解决桥后常见通病具有一定的示范作用。     

路堤土质边坡土性参数的变异性分析

对土的物理参数、力学参数的变异性进行了分析,并探讨了土性参数的变异性对路堤边坡稳定性的影响,得出对于边坡的稳定性分析应在定值法分析的基础上进行可靠度分析,而不应当仅仅进行简单的力学定值分析而判定边坡质量状态的结论。     

离子土固化剂改良膨胀土的机理研究

以河南安阳典型弱膨胀土为研究对象,分别对素土及离子土固化剂（Ionic Soil Stabilizer,简称ISS）改良土进行一系列的理化试验研究,通过标准吸湿含水率试验分析土体吸湿持水能力的变化;通过X射线衍射、傅立叶红外光谱测试、阳离子交换量及可交换阳离子成分测定、Zeta电位、比表面积,扫描电镜试验分析土体矿物组分、晶体结构、电化学性质及表面属性等反映土体胀缩本质因素的变化规律。试验结果表明：膨胀土经离子土固化剂处理后,吸湿持水能力下降,膨胀能力变弱,土样矿物成分未发生明显变化,但蒙脱石类矿物d₀₀₁晶层间距变小,层间水合度降低;通过离子交换,ISS置换出膨胀土体颗粒表面亲水性阳离子,促使土体阳离子交换量减小,可交换阳离子主要成分为Ca²⁺;改良土体ξ电位降低,土颗粒间连接力增强,比表面积减少。ISS改良机理可解释为通过离子交换,吸附,包裹等一系列复杂的表面物化反应,降低黏土矿物晶层间“水敏性”,改变土颗粒表面的双电层结构,促使结合水膜厚度减薄,从而降低了土体的膨胀性,水稳定性。     

水泥稳定土处治盐渍土软土地基试验研究

通过 S201线水泥稳定土处治试验盐渍土软土地基研究,找出了水泥稳定土处治盐渍土软土地基的合理厚度,以完善盐渍土地基处治设计及施工工艺,为盐渍土湿软地基处治提供参考.     

非饱和土的性状及膨胀土边坡稳定问题

主要叙述非饱和膨胀土及其边坡稳定研究方面的新进展。首先讨论了非饱和土研究中与土坡稳定性有关的若干重要特性,指出非饱和土的气 水形态问题是非饱和土研究的一个基本问题。并提出随含水率由小变大,非饱和土存在四种气 水形态,不同气 水形态的土具有不尽相同的性状。然后,对非饱和土的吸力和土水特征曲线以及不同气 水形态下的强度作了讨论,并对非饱和土的本构关系作了简要的介绍。接着以南水北调中线膨胀土渠道工程为背景,以吸力问题为中心,对非饱和膨胀土边坡滑动的各种内在的和外界的因素进行了分析,尤其对新近研究的降雨入渗和裂隙影响的研究进行了定量的分析,改变了以往对这方面只进行定性研究的情况。在此基础上对边坡失稳的机理和考虑裂隙及雨水入渗的稳定分析方法进行了研究。     

土钉支护技术在软土基坑中的应用

土钉支护技术近年来已在我国高层建筑的深基坑开挖施工中得到愈来愈多的应用，本文作者通过对具体项目的实践，透析了该技术在运用中的一些问题，具有一定的借鉴作用。     

脂肪族离子固化剂改性水泥土的机理研究

水泥基材料加固土(水泥土)存在早期强度低、易开裂变形等性能缺陷。为对其改性,在水泥土中掺入含水率体积1/300～1/50不等的新型土壤固化材料,离子固化剂(ISS)。通过无侧限抗压强度试验、体积化学减缩试验,探究了ISS改性水泥土的可行性,并通过对表面吸附特性、物相构成演变、微结构特性的表征及分析,对ISS改性水泥土的机理进行了系统的研究。结果表明:ISS分子对于水泥土各组分具有显著的选择吸附性;ISS掺入水泥土后,能够提升体系内各组分的分散性并降低黏土矿物结合水的能力,进而加速土体内水化反应产物的生成,优化土体孔隙结构,提升土体强度并增大体积化学减缩;最优ISS掺量为1/150,过量的掺入会减弱ISS的改性效果,但可降低水泥土体积的化学减缩。相关成果可为离子固化剂应用于水泥土的改性提供一定的参照。     

Effect of cation exchange capacity of soil on stabilized soil strength

While a certain correlation between the cation exchange capacity (CEC) of the soil and the strength of the cement stabilized soil has been reported, the mechanism remains unclear. In this research, a set of soil samples with different CECs were stabilized with different proportions of cement and calcium hydroxide (Ca(OH)₂, CH). The influence of soil CEC on the strength of the stabilized soil was investigated by analyzing the CH saturation in the pore solution and measuring the strength of the stabilized soil specimens. It is revealed that cation exchange in the soil can reduce the CH saturation of the stabilized soil. If the CEC of the soil is too high, the CH in the pore solution of the stabilized soil cannot reach the saturation level, and further cation exchange would then consume the Ca²⁺ ions which should be originally used to generate calcium silicate hydrate, thus result in the poor strength of the stabilized soil.     

非饱和土土水特性试验研究

在改进的非饱和土三轴仪上对洛阳地区非饱和土开展了三轴试验,并依此对非饱和土土水特性、试样重塑对基质吸力的影响进行了分析研究。研究表明:试件的基质吸力随围压的增大而非线性减小,基质吸力随饱和度的增大而连续减小,饱和度与基质吸力的关系是连续的。     

European soil sampling guidelines for soil pollution studies

The soil sampling guidelines used in European countries (ESSG), as kindly provided by the national institutions which participated in the project, have been recorded, studied, evaluated and presented in this paper. The aim has been to ascertain what soil sampling guidelines exist in Europe; to detect similarities and differences (comparable results), advantages and deficiencies; to identify incompatible strategies and evaluate how methodologies might affect data quality; to investigate sources of deviations or uncertainties; to improve comparability and representativeness of soil sampling; to investigate the need for harmonised sampling guidelines; and to develop suggestions for standard operating procedures (SOP). Soil sampling guidelines throughout Europe differ as to whether they are applied by law, or used throughout the country. In some countries these are ISO/DIS related or based (ISO 10381-1, 1995; ISO 10381-2, 1995), or are produced by a scientific society or a standardisation body. As far as sampling strategy is concerned, not all sampling guidelines clearly describe the sampling scale, the specifications for contamination risk precautions, the sampling plan and protocol structure and the pre-analysis treatment of the soil samples. The purpose for sampling, in descending order of frequency, is soil pollution, soil fertilisation, general soil monitoring, background risk assessment, or else it is not specified. The majority of countries do not sample the top organic matter separately. Sampling depth is either related to the morphogenetic horizon or to ad hoc sampling depth, which is not specified in all cases. They suggest mass- and volume-related soil sampling, while the sampling pattern is not presented in all national guidelines. The criteria for area, site, unit, sub-unit, and point selection are mainly based on pedology and land use, following the history and pre-screening information or geology, or is site related. Some guidelines suggest the division of sampling units into sub-units. The sampling pattern is mainly grid sampling, grid and random sampling, or not mentioned. Sampling density inside the sampling unit either varies greatly or it is not mentioned, while the size of the sampling unit varies widely. Most guidelines require the collection of composite instead of simple samples, while some prefer sampling soil profiles. In the European SSG many technical details and steps are either not defined or vary, while in the pre-analysis treatment quality assurance (QA) and quality control (QC) approaches are used either both in the lab and in the field, or only in the field, or are not mentioned. The common points and the points in which harmonisation could be started or achieved are discussed.     

Influence of relative density of soil on performance of fiber-reinforced soil foundations

An experimental study has been carried out for studying the influence of combinations of relative densities of two layered soil system. The model tests have been performed for the case of circular and ring footings resting on randomly distributed fiber reinforced sand (RDFS) layer overlying unreinforced sand bed. The influence of relative density on, different type of footings i.e. circular and ring (r_i/r_o = 0.3, 0.4, 0.5, 0.6) footings; percentages of fiber in RDFS layer i.e. 0.5%, 0.75%, 1.00%, and 1.25%; and thickness of RDFS layer i.e. 0.5B, 0.75B, and 1.00B have been studied. Results have indicated that relative density, of both the RDFS layer as well as the bottom unreinforced sand layer, significantly influences the ultimate bearing capacity as well as the settlement. Improvement in terms of bearing capacity ratio (BCR) is more when top RDFS layer is compacted at 70% relative density with bottom unreinforced sand having 30% relative density. Moreover, in terms of settlement reduction, maximum improvement is observed when both the layers were compacted at 70% relative density.