地基基础设计要考虑地基土体的先期固结压力

首先介绍了土体的先前固结压力及土体对应的分类,并以此分类着重分析了在进行地基基础设计时为何要考虑地基土体的先前固结压力,最后阐述了几种先期固结压力的推求方法及考虑先前固结压力沉降的计算方法。     

关于土的前期固结压力试验中几个问题的探讨

介绍了一种比较简捷而准确地在e—logp曲线上求取最小曲率半径Rmin点O,以求取土的前期固结压力pc值的方法,并提出影响试验成果的几个重要因素,以指导实践中准确判断土层的压密状态。     

The compressibility characteristics of a compacted laterite soil

Laterite soils occupy large parts of the tropical regions of the world. They are used, in the compacted state, as bases for roads and air-field pavements, as fills for foundations, embankments and earth dams. Although the response to load with decreasing void ratio (compressibility) is important under the conditions of use, it has not been the subject of considerable study. Engineering studies in laterite soils have been limited to classification, compaction characteristics and sometimes, shear strength. The compressibility characteristics of a compacted laterite soil from Paraiba State, North-East Brazil has been examined in the oedometer. The results indicate the presence of collapsible soil grains which comminute under load. The behaviour of soil with collapsible soil grains is described.     

超前加固在软弱破碎围岩隧道中的应用

采用大型有限差分软件FLAC3D对掌子面前方围岩加固与无加固两种情况进行了数值模拟,并对围岩和隧道结构的变形及应力进行了对比分析,得出在该围岩条件下超前加固的必要性。     

Geotechnical properties of undisturbed and compacted amphibolite derived laterite soil

This study considers the influence of compactive energy on certain geotechnical properties of an amphibolite derived laterite soil with respect to the undisturbed soil. Properties such as void ratio, compression index, coefficient of permeability and cohesion showed improvement with increased compaction energy. Critical pressure and angle of internal friction were more or less constant while the maximum density showed improvement only at the energy of the modified Proctor. The usability of the soil at the various densities is also assesed.     

Some properties of A sedimentary laterite soil as engineering construction material

A sedimentary laterite soil is examined for its suitability as a construction material by the consideration of its mineralogy and basic geotechnical properties as well as its consolidation and permeability in the compacted state. Three compaction energy levels are utilised. Mineralogically, the soil contains virtually nothing undesirable while its basic geotechnical properties are those generally ascribed to non-problematic soils. The compressibility of the soil varies from moderate to low depending on the energy of compaction. It is however impervious for all the compaction energy levels. The sedimentary laterite soil constitute a good engineering construction material as it has already been successfully used as base and sub-base material in road construction. Results obtained in this study show that this laterite soil is also suitable for use as fill materials in embankment and dam construction.     

Variability in the shear strength characteristics of an amphibolite derived laterite soil

Variability in the shear strength characteristics of a fine grained amphibolite derived laterite soil within an area of one square metre in the same horizon is investigated by means of consolidated undrained triaxial compression tests. The shear strength parameters in terms of both effective and total stresses show remarkable variabilities. Cohesion values have coenfficients of variation of 65.1% and 54.7% respectively while the angle of internal friction values have coefficients of variation of 16.1% and 23.6% respectively. The chemistry of the soil has been found to be essentially constant while the spatial distribution of the goethite present was found to be non-uniform The variability in the shear strength characteristics of the soil is attributed to the inconsistent cementation of the soil particles by the goethite.     

泥页岩前期名义固结压力的层理效应研究

在研究盖层封闭性过程中发现,仅针对盖层当前的封闭性是不够的,还应研究地质历史时期盖层的演化特征。在盖层封闭性动态演化研究中,对抬升剥蚀改造阶段可采用OCR(over consolidation ratio,超固结比)法进行定量恢复。在确定OCR值过程中,关键的是获取其前期名义固结压力;同时泥页岩为沉积岩,具有明显的层理结构,因此其封闭性表现出较强的层理效应。以龙马溪组泥页岩为研究对象,采用厚壁钢质套筒约束试样横向变形来模拟单轴应变试验,获取了不同层理角度下泥页岩的前期名义固结压力及侧压系数,并分析其层理效应,探讨层理对泥页岩的脆–延转化的临界围压的影响。研究表明:(1)单轴应变试验曲线大致呈三段变化,剪应力表现出先增大后减小趋势;(2)前期名义固结压力随层理角度的增大呈先减少后增大的趋势;(3)前、中侧压系数均表现出明显的层理效应,而层理面对后侧压系数影响不大;(4)不管对于何种角度的泥页岩,前、中侧压系数均小于1,而后侧压系数均大于1;(5)泥页岩发生脆–延转化的临界围压除了与前期名义固结压力有关外,还受层理面的影响。该研究为评价不同层理角度盖层的封闭性能提供了重要依据,为建立盖层封闭性的静–动评价模型提供参考。     

高填方涵洞土体压力分析

从高填方涵洞的设计出发,对当前高填方涵洞的土压力计算理论——马斯顿法与普氏压力理论作了分析研究,并探讨了高填方涵洞土压力的减载及调整方法,以期采用合适的计算理论与土压力控制方法,建造安全、经济的涵洞结构。     

网纹红土剪切试验研究

为研究洞庭湖地区网纹红土的力学特性,对其进行了直接剪切试验和三轴剪切试验,试验表明,网纹红土的抗剪强度随垂直荷载的增大而增大,存在使其发挥最大抗剪能力的最适宜剪切速率,它随垂直荷载的增大而减慢,围压越大,土体被剪坏的主应力差也越大。     

Basic index properties,mineralogy and microstructure of an amphibolite derived laterite soil

Variability in the nature, over a small area, of soils derived from coarse-grained rocks have been widely reported. Such reports concerning soils from fine-grained rocks are however sparse. Some geotechnical properties of a laterite soil derived from a fine-grained amphibolite have been investigated with a view to ascertain its variability. Samples of the soil were taken from the same horizon within an area of about one square metre. The basis index properties, chemistry, mineralogy and microstructure of the sol samples have been investigated. Despite the similarities in the grain-size distribution. Atterberg limits and chemistry of the samples, large variations were obtained in the mineralogy as evidenced by the goethite content, as well as in the micro-structure. The variation in the microstructure is attributed to the inconsistent cementation of the soil particles by non-uniformly distributed goethite which itself is believed to be a result of the variations in the Eh-pH conditions within the soil. The implications of this microstructural variation on the geotechnical properties of the undisturbed soil is assessed.     

高强预应力管桩静压法施工在膨胀土地区的应用

以合肥市某实际项目为例,结合膨胀土性质、地基土构成、机械设备的配置及施工现场的准备工作,从测量放线、桩定位及桩起吊、就位两方面,分析了主要的施工技术措施,并阐述了施工中常见的质量问题及注意事项。     

Applied bearing pressure beneath a reinforced soil foundation used in a geosynthetic reinforced soil integrated bridge system

Geosynthetic reinforced soil integrated bridge system (GRS-IBS) design guidelines recommend the use of a reinforced soil foundation (RSF) to support the dead loads that are applied by the reinforced soil abutment and bridge superstructure, as well as any live loads that are applied by traffic on the bridge or abutment. The RSF is composed of high-quality granular fill material that is compacted and encapsulated within a geotextile fabric. Current GRS-IBS interim implementation design guidelines recommend the use of design methodologies for bearing capacity that are based around rigid foundation behavior, which yield a trapezoidal applied pressure distribution that is converted to a uniform applied pressure that acts over a reduced footing width for purposes of analysis. Recommended methods for determining the applied pressure distribution beneath the RSF for settlement analyses follow conventional methodologies for assessing the settlement of spread footings, which typically assume uniformly applied pressures beneath the base of the foundation that are distributed to the underlying soil layers in a fashion that can reasonably be modeled with an elastic-theory approach. Field data collected from an instrumented GRS-IBS that was constructed over a fine-grained soil foundation indicates that the RSF actually behaves in a fairly flexible way under load, yielding an applied pressure distribution that is not uniform or trapezoidal, and which is significantly different than what conventional GRS-IBS design methodologies assume. This paper consequently presents an empirical approach to determining the applied pressure distribution beneath the RSF in GRS-IBS construction. This empirical approach is a useful first step for researchers, as it draws important attention to this issue, and provides a framework for collecting meaningful field data on future projects which accurately capture real GRS-IBS foundation behavior.     

引入位移土压力理论的支护结构变形计算

介绍了位移土压力理论,给出了引入位移土压力理论的支护结构变形计算,并结合具体工程实例进行了说明,指出对于小于5m的基坑,运用位移土压力理论计算变形效果不明显,对于大于5m的基坑支护结构的变形对土压力的变化会非常敏感。     

锚拉式柱板墙土压力试验研究

以某高速公路轻型支挡结构监测项目为依托,对锚拉式柱板墙挡板背土压力进行了现场测试,分析了锚拉式柱板墙挡板背土压力随深度、时间变化和分布的规律,探讨了理论计算值与实测值差异产生的原因。     

浅谈高压喷射注浆法在软地基中的应用

结合工程实际，分析选择了高压喷射桩地基处理方案，阐述了设计要点，技术参数和孔距的确定，检测效果证明，用此法处理软土地基，能在较短的工期内，以较低的成本取得好的加固效果。     

拱涵位移和垂直土压力的数值模拟

通过数值模拟,对高填方拱涵的土压力和位移进行了数值分析,确定了高填方拱涵的土压力分布规律和位移规律,指出涵顶土压力呈非线性分布特征,不同于现行《公路桥涵设计通用规范》中的土压力线性分布假定。     

化学压力注浆在软弱地基加固中的运用

分析了压力注浆的机理，并对注浆法在加固工程中的设计、施工工艺进行了介绍，经过实践证明，指出该地基处理方法具有造价低廉、施工方便和不破坏原有建筑物等优点。     

Properties of concretionary laterite gravel concrete

The compressive strength and the expansion of conrete made with both highly and slightly/moderately indurated concretionary laterite gravels were studied. The compressive strength (19–42 MPa) of most of the laterite concrete is comparable with the average strength (45 MPa) of concrete made with the usual granite crushed rock aggregates from the region. The strength of the laterite concrete is mainly dependent on the aggregate-cement bond whereas the physical properties of the aggregates are only of secondary importance. The laterite concrete showed a net contraction when immersed inhot 1N NaOH solution (i.e. rapid alkali reactivity test). This behaviour is attributed to the low/very low contents of silica, clay and lime in the aggregates. The results of the study reveal that concretionary laterite gravels are potential alternative cheap sources of aggregates for structural concrete.