Influence of cohesion on California bearing ratio of clay-gravel mixtures

An understanding of the behavior of cohesive sediment is required to solve various engineering problems such as scour around bridge elements, mitigation of soil erosion, pavement design, river bed degradation,stable channel design. Pavement foundation designers principally use the California bearing ratio(CBR)to describe the subgrade and subbase materials and their strength. Several laboratory experiments were done to study the variation in the CBR of cohesive mixtures comprised of clay-gravel m...     

Rock Magnetic Investigation of Historical Lavas Used in Palaeointensity Studies

Five samples from historical lava flows on Mt. Etna, which had previously been used in a palaeointensity study, were examined using a combination of rock magnetic and microscopic techniques to elucidate the causes of failure of palaeointensity determination. The samples were characterised using a combination of low-temperature susceptibility (LT-), Bitter pattern imaging and scanning electron microscope (SEM). High-temperature susceptibility curves and hysteresis loops had been previously measured by Calvo et al. (2001). Of the five samples only one gave an accurate palaeointensity. This sample was deuterically oxidised and consisted of large exsolved ore grains. It was only possible to distinguish this sample either optically or magnetically from a similar sample by the LT- warming curves; the unsuccessful sample displayed alteration in the LT- warming curves, which was not readily observed in the high temperature susceptibility curves. It is proposed that the measurement of LT- curves before and after heating could be a more sensitive method of determining suitability for palaeointensity determination than previous rock magnetic pre-selection techniques.     

Provenance discrimination and Source-to-Sink studies from a dryland fluvial regime： An example from Kachchh,western India

Tracing the sediment delivery from its source terrain to its ultimate sink envisage multiple factors that play a vital role in understanding present day erosional engine.To accomplish this,it is significant to distinguish the variable end-members contributing to the basin.The findings from the study of dryland coastal fluvial regime in Kachchh(Western India),which is one of the end members contributing to the Gulf of Kachchh coast(partial sink) and finally to the Arabian Sea(ultimate sink) have been presented here.Multi-proxy sediment provenance proxies such as grain-size,clay minerals,geochemistry and magnetic minerals have been employed to evaluate the provenance discriminating characteristics of the Kachchh dryland fluvial system and factors influencing them.The results of different proxies indicate that the provenance signatures of uplands are quite characteristic with magnetic susceptibility(χ) values of 20×10~(-7)m~3kg~(-1) and smectite(S)/kaolinite(K) ratio between 0.26 and 0.49.The middle reaches show marked increase in magnetic mineral concentration with χ values(140×10~(-7)m~3kg~(-1))and S/K ratio(4.92),while the estuarine tract shows χ values(80×10~(-7)m~3kg~(-1)),S/K ratio(1.90) and,characteristic heavy minerals(i.e.mica minerals),probably reflect the interplay between land and sea oscillations.Major sources of sediments within catchment scale were identified,viz.,upland sedimentary rocks(Juran and Bhuj Formation sandstone-shale) and middle reaches volcanic(Deccan Trap Formation basalt) rocks.The present study draw cautions in provenance of sediment discrimination in areas influenced by Deccan basalt that has the overwhelming sediment delivery and a comparatively subdued effects of other provenance signatures.The studied proxies of mineralogy of clays,magnetic minerals and geochemistry of heavy and major elements serve as the potential for fingerprint of sediment source regions and hence behold a strong position in source to sink studies globally.     

膨胀土与地形变

本文根据南京地震台短水准场地膨胀土研究的实际资料,指出了在膨胀土发育区进行地形变观测、地震地质和震害调查、烈度小区划等项工作时,必须考虑到膨胀土特性这个因素,以避免失误。     

Facies characteristics, morphology and depositional models of clay-slide deposits in terraced fjord valleys, Norway

Many bedrock-confined fjord valleys along the Norwegian coast contain thick accumulations of fine-grained sediments that were deposited during and after the last deglaciation. The deposits gradually emerged above sea level due to glacioisostatic uplift, and fjord marine sedimentation was gradually followed by shallow marine and fluvial processes. During emergence terraces and river-cut slopes were formed in the valleys. Subsequent leaching of salt ions from the pore water in the marine deposits by groundwater has led to the development of quick clay. The deposits are subject to river erosion and destructive landslides involving quick clay. Most slides are of prehistoric age. Others are known from modern observations as well as from historic records.Landforms such as distinct slide scars or the hummocky terrain of slide deposits may be strongly modified by secondary processes. In addition, deposits from the most liquid part of quick clay slides may have planar surfaces. Clay-slide deposits on a fluvial or deltaic terrace, therefore, are not always easily recognized from morphology, and only exposures may reveal their internal structures and allow them to be distinguished from overbank flood sediments. Detailed sedimentological work shows that slide deposits in such setting consist of distinct facies containing reworked marine sediments. We propose three facies successions of clay-slide deposits that form a continuum. The dominant components of these succession types are: slightly deformed blocks of laminated clay and silt (A), highly deformed clay and silt with gravel clasts (B) and massive to stratified clay and silt with scattered clasts (C). We suggest that in many cases a basal muddy diamicton is a characteristic, and possibly diagnostic feature. Processes and depositional models are interpreted from the different succession types. The results may be relevant for identifying clay-slide deposits elsewhere and may be useful during general mapping of fjord marine deposits and characterization of slide-prone areas as well as during identification of prehistoric slides.     

南京栖霞山铅-锌-银矿银的工艺矿物学研究

研究了南京栖霞山铅-锌-银矿银的工艺矿物学特征,分析了矿石的化学组成,对矿石中银矿物的种类、成份、粒度、嵌布特征进行测定和统计,并进行了矿石中银的物相分析和银的平衡配分。根据银的工艺矿物学研究结果,提出了提高银的选矿回收率的建议。     

The First James K. Mitchell Lecture In situ soil testing: from mechanics to interpretation†

The current use of fundamental mechanics in developing rational interpretation methods for deriving soil properties from in situ test results is reviewed and evaluated. The focus is on some of the most widely used in situ test devices including cone penetrometers with and without pore pressure measurements (CPTU and CPT), self-boring and cone pressuremeters (SBPMT and CPMT), and flat dilatometers (DMT). In situ tests in both cohesive and frictional soils for measuring strength and stiffness properties, in situ state parameters, consolidation coefficients, stress history, and in situ stresses are considered in detail.     

Identifying parameters controlling soil delayed behaviour from laboratory and in situ pressuremeter testing

The aim of this paper is to present a methodology for identifying the soil parameters controlling the delayed behaviour from laboratory and in situ pressuremeter tests by using an elasto‐viscoplastic model (EVP‐MCC) based on Perzyna's overstress theory and on the elasto‐plastic Modified Cam Clay model. The influence of both the model parameters and the soil permeability was studied under the loading condition of pressuremeter tests by coupling the proposed model equations with Biot's consolidation theory. On the basis of the parametric study, a methodology for identifying model parameters and soil permeability by inverse analysis from three levels of constant strain rate pressuremeter tests was then proposed and applied on tests performed on natural Saint‐Herblain clay. The methodology was validated by comparing the optimized values of soil parameters and the values of the same parameters obtained from laboratory test results, and also by using the identified parameters to simulate other tests on the same samples. The analysis of the drainage condition and the strain rate effect during a pressuremeter test demonstrated the coupled influence of consolidation and viscous effects on the test results. The numerical results also showed that the inverse analysis procedure could successfully determine the parameters controlling the time‐dependent soil behaviour. Copyright © 2008 John Wiley & Sons, Ltd.     

Changes in grain-size and sedimentation rate of the Neogene Red Clay deposits along the Chinese Loess Plateau and implications for the palaeowind system

In recent years, the Red Clay deposits underlying Quaternary loess on the Chinese Loess Plateau (north China) have attracted more attention because they show a direct and continuous record of past atmos- pheric circulation and palaeoclimatic change. Investiga- tions on Red Clay deposits through multidisciplinary methods have demonstrated an aeolian origin for the Red Clay, like the overlying Quaternary loess. The Red Clay formed during the Miocene and Pliocene[1―13]. However, the type o…     

柿竹园矿床大理岩型锡矿石工艺矿物学研究

大理岩型锡矿石产于燕山早、中期千里山花岗岩与中、上泥盆统灰岩的外接触带。矿石呈细脉、网脉浸染状,锡矿物有:锡石、黄锡矿,富钛尼日利亚石、尼日利亚石和木锡矿,脉石矿物绿帘石、石榴石、电气石、萤石、方解石及磁黄铁矿等亦含锡,锡主要呈锡的浊立矿物存在,占总锡量的89.78％,其中锡石锡占总锡量的80.01％,其次有呈类质同象形式存在的锡,在绿帘石、石榴石、电气石等矿物中以Sn~(4+)取代Fe~(3+),这类锡占总量的8.33％。工艺矿物学研究表明,该类锡矿石以“贫”、“细”、“杂”为特征。锡不仅十分分散,而且品位偏低,矿石矿物组合及镶嵌关系复杂、相互包裹,紧密连生;锡矿物粒度微细,粒径一般为0.2～0.01mm,部分为<0.0l～0.002mm,是一种难选的锡矿石类型。通过锡的回收试验,采用选冶联合工艺流程,预测锡的最佳回收率可达50％以上。