复合桩基在沿海软土地基中的研究应用

本文报导了在沿海软土地基中采用复合桩基作为多层建筑基础的工程应用。在研究过程中，对基础底板反力及建筑物沉降进行了长期观测。研究成果表明，软土地基承台下地基土仍能分担较大份额的上部荷载。采用复合桩基进行地基处理具有明显的经济效益。     

软土地基处理方法综述

针对软土地基的危害性,阐述了软基处理的目的,分别介绍了轻型材料转换处理技术,土工织物加固地基技术,复合地基处理技术等常用的软土地基处理方法,以指导实践。     

粉喷桩处理大面积软土地基

铁路工程具有点多线长、工程量大、地质地貌复杂的特点。当铁路工点处于软土地基时，必须进行处理。现阶段常用的软土地基处理方法有清淤换填、碾压夯实、排水固结、挤密、排水芯板及粉喷桩等。其中粉喷桩加固软地基的施工方法是在注浆法基础上发展起来的一项新技术，现已经广泛用于铁路、公路工程的地基处理、开挖支护体系中。本文结合广深港客运专线制梁厂工程实际，讨论粉喷桩在大面积软土地基处理过程中的应用及半刚半柔复合地基的形成机理。     

多桩型复合地基在地基处理中的应用

随着大量高层建筑物越来越多,地基的处理方法显得很重要,在沉降变形不易控制的软土地区,好的方法更加重要。本文通过比较几种不同的地基处理方案,着重阐述了多桩型复合地基在软土地区地基处理中的优点。     

公路工程软土地基处治方法

简单介绍了软土的性质和软土地基的危害,分别阐述了浅层软土地基、深层软土地基、复合地基的各种处理方法及其原理、优缺点等内容,指出应综合考虑工程地质、上部结构、工期、造价等因素,合理确定适合的方案。     

沉降控制复合桩基在软土地基中的运用浅析

在软土地基中 ,房屋基础的选型与设计 ,对其总造价往往有着至关重要的影响。近年来 ,大量工程实践证明 ,在软土地基中 ,沉降控制复合桩基 (以下简称复合桩基 )能在满足建筑设计要求的同时 ,有效地降低其成本 ,取得较好的经济效益。是目前软土地基上多层房屋普遍采用的一种基础型式。下面笔者结合工程实例谈谈自己在复合桩基运用中的粗浅体会。1　沉降控制复合桩基的工作原理在软土地基上 ,多层建筑采用天然浅基础方案在很多情况下难以满足地基变形的要求。当采用常规桩基时 ,即外荷载全部由桩承担 ,往往桩数较多 ,其工程造价大幅增加。复合…     

强夯碎石桩的设计及应用

以长治至晋城高速公路K32 885拱通道地基处理为例，介绍了运用强夯碎石桩加固软土地基的工程实践，指出强夯碎石桩适用于塑性指数高、含水量较大的软土地基处理。     

运用振动挤密碎石桩与CFG桩处理某钢铁厂软土地基

通过工程实例，介绍了某钢铁厂在软土地基处理方案选拔中，采用振动挤密碎石桩与CFG桩联合处理软土地基的工程经验。     

复合地基在软弱地基处理中的应用

介绍了建筑软土地基的特点和处理中常见的复合地基形式,并针对软弱地基的实际情况,提出了一些处理的方法,以指导实践.     

水泥粉喷桩处理长钢6000m^3／h制氧工程软土地基

本文针对长钢制氧车间软土地基的特点，提出用水泥粉体喷射搅拌桩处理，由于方法合理，效果良好，经多种手段检测，复合地基强度满足设计要求。     

强夯置换处理软土地基的现场试验研究

结合深圳市湾滨海生态景观带岸线整理及软基处理工程实例,通过强夯置换的现场试验,对强夯过程中的夯沉量的变化规律、置换深度以及孔隙水压力的增长和消散规律进行分析,得出一些有价值的结论,并就强夯置换法在软基处理中的后续现场试验提出了几点建议。     

大面积堆载作用下软土地基变形特性

通过在大面积堆载场地设置监测仪器,进行历时 3 a 的现场监测,对大面积堆载作用下软土地基的变形特性和加载条件、地层条件、排水条件、时间效应等的相关性进行分析研究,揭示了大面积堆载作用下软土地基变形特性不同于常规荷载作用下软土地基变形特性的规律,总结了在不同边界条件下软土地基变形和固结沉降的规律,为软土地基的固结沉降分析计算提供依据。     

Comparative analysis on performance of vertical drain improved clay deposit under vacuum or surcharge loading

This paper presents two well-instrumented large-scale field tests of PVD-improved soft soil with vacuum and surcharge preloading, respectively. The two large-scale field tests were conducted adjacent to each other with the same preload. A comparative analysis was performed to investigate the performance of subsoil (i.e., the ground settlement, the layered settlement, the lateral displacement of subsoil and pore water pressure) under vacuum preloading and equivalent surcharge preloading. Some design methods were verified based on the field data. Cone Penetration Tests (CPT) and Vane Shear Tests (VST) were conducted to assess the improvement effects on subsoil after preloading. The results showed that as compared with surcharge preloading, vacuum preloading mitigated the differential settlement of the ground. The vacuum pressure transmitted into the soil with a minor loss through the PVD length. From a practical point of view, the improvement effects by vacuum preloading and surcharge preloading were similar in terms of influence depth and soil strength based on the in-situ tests.     

带褥垫层刚-柔性桩复合地基工程性状的试验研究

为充分调动地基土参与基础的共同工作,近年来我国土木工程界根据工程实践经验,提出用柔性短桩处理浅层软弱土、刚性长桩控制沉降、褥垫层调整和改善桩土应力分担比的带褥垫层刚-柔性桩复合地基形式。为研究这种新型复合地基的工程性状,本文作者在杭州某采用该种地基的七层住宅楼基底埋设压力盒进行现场观测。实测数据表明,在垫层的作用下,桩土荷载分担在加载初期的弹性阶段近似按各自的相对刚度分配,随着上部荷载的增加,浅层地基土和柔性桩逐渐进入非线性状态,新增荷载主要由刚性桩来承担。本文结果为进一步的理论研究和工程设计提供了有益的依据。     

Geotechnical Reconnaissance Study on Damage Caused by 2001 Gujarat Earthquake,India

The Gujarat earthquake in India occurred in January, 2001, and caused significant damage in the province of Gujarat. The Japanese Geotechnical Society sent a small reconnaissance team to the damaged region after the quake. The present text presents the report from this activity. The major attention of the team was focused on geotechnical aspects of the damage which were related to earthfill dams and harbor land fills. It was found that a significant portion of damage was concentrated in fills resting on soft natural soils. Swedish weight soundings which were conducted at two places demonstrated the existence of such a soft subsoil. From this, it was concluded that amplification of earthquake shaking as well as the permanent deformation in the soft foundation soil induced such kinds of damage as subsidence, cracking, and lateral spreading in overlying artificial fills. For the better seismic resistance of those affected fills during future earthquakes, the improvement of soft subsoil seems essential.     

考虑覆盖层对地基应力分散效应的地基沉降计算方法探讨

对于软土地基上的建筑物的沉降计算,我国规范推荐采用分层总和法。分层总和法中地基附加应力的计算以点荷载作用下的半无限空间的Boussinesq解为基础。对于具有不同刚度和强度相差较大的地层而言,以此方法为基础计算得到的最终沉降往往偏大。本文提出一种基于多层弹性理论的考虑覆盖层对地基应力分散作用的地基沉降计算方法。这种方法的计算结果使地基中的应力水平较基于Boussinesq解的结果大幅降低,对于某工程实例而言,计算得到的地基中的总有效应力小于前期固结压力,土层的变形相对较小。工程实测的结果表明,所提出方法计算结果与实测结果较为接近。     

Analysis of field performance of embankments on soft clay deposit with and without PVD-improvement

This paper presents a case history of the performance of two full-scale test embankments constructed on soft clay deposit in the eastern coastal region of China. One embankment was constructed on natural subsoil and the other was constructed on prefabricated vertical drain (PVD) improved subsoil. The thickness of the soft clay deposit without PVD-improvement was 19 m and with PVD-improved case was 23 m. The PVDs were installed to a depth of 19 m with spacing of 1.5 m in a triangular pattern. Field performance of the two embankments was analyzed using the finite element method. The following influential factors: (i) hydraulic conductivity of subsoil in field and (ii) discharge capacity of PVDs were investigated numerically. The back-analyzed results for the embankment on natural subsoil showed that the hydraulic conductivity ratio (C_f) of field to laboratory values is about 6. To analyse the PVD-improved subsoil, a simple approach using the equivalent vertical hydraulic conductivity of PVD-improved subsoil was employed. The analytical results show that PVDs increased the bulk vertical hydraulic conductivity of soft subsoil by about 30 times compared to the original non-treated subsoil. The discharge capacity of PVDs in this field case is 79–100 m³/a, which is consistent with the findings from laboratory tests and other reported values in literature.     

软土区高速公路地基沉降变形监控方案及实施技术研究

软土地区修筑高速公路,由于软土含水量高、强度低、压缩性大等特点,造成工程条件很差,施工过程的安全风险比较大。因此,软土地基路堤施工期间,根据场地软土的特点,进行施工安全监控,控制地基沉降变形是确保施工进度和施工质量的重要手段。本文在已有的软基设计、施工研究成果基础上,从监控指标的确定和监控实施两方面对软土地基路堤施工期变形监控进行研究,以达到确保施工安全的目的,对类似地区工程实践活动提供指导。     

强夯加固饱和软粘土的几个问题探讨

根据最近用强夯加固饱和软粘土的经验,探讨了下列几个问题:用现场试验法确定夯击参数与饱和软粘土的加固效果。饱和软粘土在强夯后的渗透性。它基本符合西德鲁尔大学提出的公式V=Ki~m。根据荷载大小、种类、范围,地基土壤特性及建筑物类型,提出了超夯范围。强夯振动对附近建筑物的影响及减振措施。建议按频率分析法考虑对附近建筑物的影响。     

不均匀软弱下卧层对砌体结构的影响

通过对某典型的砖砌体结构房屋质量问题的分析，指出不均匀软弱下卧层是造成房屋不均匀沉降的主要原因。由于设计中的地基基础处理不当及施工中砌筑质量差导致了房屋严重开裂。因此对于这类问题，设计和施工两方面都要引起足够的重视，提高设计和施工质量，确保房屋安全，减少损失。