云南大理洱海东缘早全新世软粘土的工程特性研究

云南大理洱海周缘分布着厚层的早全新世软粘土, 大量原状样品的工程性质测试结果表明, 洱海东缘早全新世软粘土具有高含水量、孔隙比高、压缩性强、强度低、高塑性等工程特性, 其中表层软土超固结现象明显。通过对软土的物理力学指标统计分析表明, 洱海东缘软粘土的力学指标的变异系数较大, 而物理性质指标变异系数很小; 多个物理指标之间及物理指标与力学指标之间存在明显的相关性。对洱海东缘软粘土各类工程特性指标之间相互关系的认识, 不仅有助于揭示软粘土的工程性质及其形成机理, 而且可以指导软粘土工程问题处理措施的合理选择。      

Micro-environmental controls on biomineralization: superficial processes of apatite and calcite precipitation in Quaternary soils, Roussillon, France

Calcium hydroxyapatite and calcite precipitates around bacteria were observed in 2-week-old alluvial topsoil (Roussillon area, SE France). This observation prompted a laboratory study of Ca²⁺ and PO₄³⁻ incorporation into hydroxyapatite and Ca²⁺ into calcite mediated by bacteria using similar topsoil material, but free from apatite and calcite. Subsamples were prepared using three different grain sizes, and experiments were undertaken using sucrose and different contents of Ca²⁺ and PO₄³⁻. Mineralization experiments proceeded over 5 days. Calcium and PO₄³⁻ sorption onto clay influenced the Ca/P ratio in the solutions. Hydroxyapatite and calcite precipitation only occurred in unsterilized samples. The presence of clay minerals promoted biomineralization.     

Use of clay as a pozzolona in high strength Portland cement and its thermal activation

In this investigation local clay from Cherat mines, Nowshera District, NWFP, Pakistan, has been tested as a pozzolanic material in high strength Portland cement. Thermal treatments were performed as a means of activation of the clay. It was found that thermal treatment of the clay can increase its pozzolanic activity. Different blended mortars, containing different amounts of clay, activated at different temperatures were studied for compressive strength, consistency, and setting times. It was concluded that the mechanical properties of the blended cements were mainly governed by the percentage of incorporation of the calcined clay. Blended cement composition has been formulated, with optimal results of 20% calcined clay at a temperature of 600℃.     

非均质软土基坑抗隆起稳定性的极限分析方法

考虑到实际工程中土体非均质以及软土地区基坑开挖过程中土体稳定性的特点,将极限分析上限方法应用于非均质软土基坑抗隆起稳定分析计算中,讨论了极限分析方法的适用性问题。选用Prandtl机构建立了非均质软土地区基坑抗隆起稳定分析的运动许可速度场,根据速度场推导了极限分析上限方法的计算公式。讨论了该方法中土体强度、基坑宽度、支护墙体入土深度、基岩埋置深度等因素对坑底抗隆起稳定的影响。通过几个工程的计算与对比,验证了该方法的适用性和优越性。     

Climatic signals in lacustrine deposits of the Upper Yacoraite Formation,Western Argentina: Evidence from clay minerals,analcime, dolomite and fibrous calcite

Authigenic clays are an important control on reservoir quality in lacustrine carbonates but remain challenging to predict. Lacustrine depositional systems respond to climatic variations in rainfall, surface runoff and groundwater input, and evaporation, and result in rapid and frequent changes in lake volume; this is expressed through changing water depth and shoreline position. In the upper portion of the Early Palaeocene Yacoraite Formation of the Salta Basin in Argentina, extensive lacustrine deposits were deposited during the sag phase of rifting. Prior high-resolution stratigraphic studies have suggested that climatic factors control microbial carbonate sequences within a ‘balanced fill’ lake, with variation in the lake level having a major influence on facies association changes. This study characterizes the evolution of facies and mineralogy within the Yacoraite Formation, focusing on the distribution of clay minerals, making a link between the high, medium and low-frequency sequence stratigraphic cycles. The low-frequency transgressive hemicycle of the upper portion of the Yacoraite Formation is comprised of abundant siliciclastic facies, suggesting a wetter period. Microbialites occurring in this interval are coarse-grained and agglutinated. Detrital clay minerals such as illite and chlorite and associated siliciclastic sediments were input to the lake during high-frequency transgressive periods. During high-frequency regressive hemicycles, sedimentation was dominated by carbonate facies with Ca-rich dolomite and the authigenic clays are comprised of chlorite/smectite mixed-layers. By contrast, the low frequency regressive hemicycle records fine-grained agglutinated microbialite with horizons of fibrous calcite, more stoichiometric dolomite, barite and authigenic magnesian smectite. This indicates elevated ion concentrations in the lake under intense evaporation during an arid period. Understanding the conditions that are favourable for formation and preservation of authigenic clays within the lacustrine environment can improve understanding of reservoir quality in comparable economically important deposits.     

上海市浅部数层硬土的沉积环境、时代及划分对比

上海市陆域东部滨海平原区埋深三、五十米以上及西部湖沼平原区埋深二十多米以上分布有数层“硬土”,现在可以确定,均属于晚更新世晚期的陆相沉积。     

柏井采空区地基注浆加固技术

通过目前国内外现有资料的对比研究，对严重影响石太高速公路修建和运营的柏井采空区采用压力注浆的方法，充填采空区上覆的裂隙冒落带，以达到加固地基的目的。灌注材料选用水泥和粘土，水固比为１：１．５，依据地面构造物不同，在桥涵地段采用１：０．８：０．７（水：水泥：粘土，下同）的配比，在边坡地段采用１：０．５：１的与比，在一般路段采用１：０．３：１的配比，灌注浆液的结石体在采空区及上覆的裂隙冒落带中充填率达     

复杂应力条件下掺砾黏土真三轴试验

采用新型真三轴仪器,对掺砾黏土进行了复杂应力条件下加载试验,近似模拟了土石坝填筑期心墙土体单元的加荷过程。试验结果表明,由于土体单元处于复杂应力状态,即使是单向加载这样的简单加荷应力路径,在不同应力方向上的应力和变形也都呈现显著的应力各向异性。土石坝应力变形分析中坝体单元处于三向应力条件下,由于加载引起的应力各向异性对心墙乃至整个坝体的应力变形规律都有较大影响,合理的本构模型应该能够反映并描述这种复杂应力状态下的应力各向异性。     

深层搅拌桩在某住宅楼地基加固中的应用

以桂林某工地为例阐述了深层搅拌桩在深厚软弱地基中的设计、施工方法以及应用效果。     

高黏粒含量新吹填淤泥加固新技术室内研发

新吹填淤泥处于“稀泥汤”状态,工程特性极差,几乎无承载力,现有真空预压技术加固效果不理想,地基有效加固深度小,土体强度增长有限。为此,提出了“真空预压联合化学加固”的新思路。室内采用3种环保型化学加固剂设计了3种真空预压联合化学加固方案（VPCT1、VPCT2、VPCT3）和1种纯化学加固方案（CT）,与现行真空预压加固方案（VPT）进行了对比试验研究。研究结果表明：(1) 添加有效的化学加固剂后,新吹填淤泥在抽真空前较短的静置时间内就基本完成了自重沉积过程;(2) 化学加固剂选取得当能有效提高土体的加固效果;(3) 宏观上,VPCT3方案加固效果较均匀,加固后土体中黏粒含量明显降低、湿密度最大,孔隙比降低幅度明显,无侧限抗压强度也最大,为66.7 kPa（为VPT方案的3.5倍）;(4) 微观上,VPCT3方案加固后,土颗粒之间的孔隙总面积、孔隙平均周长、总孔隙数、孔隙比、孔隙率等最小,单元体之间有良好的定向度、排序性最好,连结方式以面-面为主导,相互之间接触紧密,团聚现象最明显。因此,相对于现行的真空预压技术而言,VPCT3方案土体加固效果非常明显,也较均匀,可以进一步开展现场试验研究,探讨其付诸于工程实践的可行性。