苏北与长江三角洲沉积环境及其土体物理性质关系探讨

土体的物理力学性质是在一定的沉积环境中形成的,所以二者之间存在着密不可分的联系。本文把苏北沿海与长江三角洲地区的沉积环境和物理性质进行联系性的对比分析,说明沉积环境及沉积物源的不同是造成这两个地区浅部土层物理性质差异很大的主要原因,也论证了特定的沉积环境将形成土体特定的物理力学性质。因此,把沉积学与工程地质学结合起来广泛展开二者之间相互关联的地质普查工作,将有助于认识、验证甚至提前预测不同地区土体的物理力学特性。     

南黄海中西部海底空间沉积特征及工程地质特性

南黄海海区被认为是我国在海上进行公益性、战略性油气资源评价的有利海区,但目前该海区海底深度方向上沉积特征及工程地质特性的研究仍较少。本文利用2009年6月及2010年6月在南黄海中西部海底获取的287个站位的沉积物柱状样品,通过粒度分析、物理力学性质测试,得到了该海域海底的空间沉积特征及沉积物工程地质特性:研究区海底表层沉积物类型多样,西南海底以粉砂质砂、砂质粉砂为主,力学强度较高,不易压缩,但由于较强的水动力条件,易冲刷粗化;东北海底以粉砂质黏土、黏土质粉砂为主,力学强度低,极易压缩;研究区海底深度方向上沉积物类型并非单一,常由几种类型沉积物互层组成,沉积物基本物理性质和力学性质随埋深变化的情况主要与沉积物类型有关,其次是压实作用。一定程度上,可利用本文给出的拟合函数,通过压缩波速估算研究区海底沉积物的孔隙度。     

西太暖池区生物组分对海底表层沉积物物理力学性质的影响

西太平洋暖池区是指位于热带西太平洋及印度洋东部海表温度常年在28 ℃以上的海域,是全球海表温度最高的深海区,构造环境与沉积环境复杂,沉积物中的生物组分含量差异较大,生物组分会对深海沉积物物理力学性质产生显著影响,但目前对沉积物中生物组分含量和沉积物物理力学性质之间的相关性关系尚不明确。本文对西太平洋暖池区核心部位的表层沉积物样品进行现场物理力学性质测试和室内涂片鉴定,研究深海表层沉积物的物理力学性质与生物组分之间的关系。结果表明:研究区表层沉积物含水率范围为61.1%~435.1%,天然密度范围为1.04~1.76 g/cm³,贯入阻力范围为0~100 kPa,十字板剪切强度范围为0~8.6 kPa,整体具有高含水率、低密度、低强度等典型的深海沉积物物理力学性质特点。西加洛林海脊、海山等CCD以浅的区域为钙质生物组分>50%的钙质沉积区;西加洛林海槽西南部及其周边的深水沟槽地区一般为硅质生物组分>50%的硅质沉积;西加洛林海盆内部则主要为黏土沉积区。随钙质生物组分减少和硅质生物组分增多,表层沉积物类型分别为钙质沉积物、黏土沉积物和硅质沉积物,天然含水率变高,天然密度、贯入阻力和十字板剪切强度降低,表明深海表层沉积物的物理力学性质与生物组分含量密切相关:贯入阻力、十字板剪切强度、天然密度与钙质生物组分含量呈正相关,与硅质生物组分含量呈负相关;而天然含水率正好相反,与钙质生物组分含量呈负相关,与硅质生物组分含量呈正相关。本文建立了深海沉积物中生物组分与物理力学性质之间的相关关系,提出了沉积物生物组分含量与物理力学性质之间的拟合公式,可以为深海沉积物工程性质的评价提供参考。     

黄渤海表层沉积物环境磁学特征分类及物源诊断

黄渤海是我国东部陆架的重要组成部分, 基于黄渤海130个表层沉积物样品详细的环境磁学研究探讨了磁学特征分类及物源。按照黄渤海表层沉积物样品的S-300、SIRM/X与SIRM磁性参数特征, 将研究区表层沉积物分为4个类型: 类型1磁性矿物含量较高, 亚铁磁性矿物含量中等, 磁性矿物颗粒中等, 与黄河物质磁学特征极为相似, 这里沉积动力中等, 为中等水动力黄河沉积区; 类型2磁性矿物含量中等, 亚铁磁性矿物含量中等, 磁性矿物颗粒细, 与长江及黄河物质磁学特征较为相似, 水动力环境较弱, 为弱水动力黄河-长江混合沉积区; 类型3磁性矿物含量较低, 亚铁磁性矿物含量较低, 磁性矿物颗粒中等, 主要是该海域存在的残留沉积, 水动力中等, 命名为中等水动力残留沉积区; 而类型4磁性矿物含量高, 亚铁磁性矿物含量高, 磁性矿物粒级粗, 与长江沉积物具有相似的磁学特征, 沉积动力强, 命名为强水动力长江沉积区。以上四类沉积物具有不同的环境磁学和沉积环境特征, 从而可以帮助识别黄渤海沉积物的分布及物源信息。     

广西钦州湾外湾海域表层沉积物粒度特征及沉积环境

沉积物粒度特征是反映沉积作用、沉积环境和沉积动力条件的明显标志,为了解广西钦州湾外湾海域沉积环境,对研究区167组表层沉积物样品进行粒度测定,分析粒度参数特征并划分沉积物类型,运用Pejrup三角投图对研究区进行沉积动力环境分区,采用Gao-Collins粒径趋势分析法总结研究区表层沉积物的运移趋势。结果表明: 研究区表层沉积物以粉砂和砂为主,分选系数差。Folk-Ward分类法的结果显示研究区表层沉积物类型共12种,以砂质粉砂、砂质泥和粉砂分布最广,分别占样品总数的22.16%、17.37%和14.97%。沉积动力分析显示研究区的沉积环境复杂,水动力整体表现出由湾口向外逐渐减弱的特征。粒径趋势分析表明研究区表层沉积物整体向湾口及潮流深槽(航道)方向运移。综合分析表明研究区的沉积环境主要受潮流、波浪及人类活动等的影响。研究成果可为港口建设、深水航道改扩建以及海洋牧场建设等提供科学参考。     

系统聚类分析在现代沉积环境划分中的应用--以崎岖列岛海区为例

根据崎岖列岛海区现代沉积物的分选系数、砂粒含量和粘粒含量 3个粒度特征参数,采用系统聚类分析方法划分现代沉积环境,与已知的沉积环境特征信息较为吻合。除水动力条件外,研究区的现代沉积环境深受物源条件和地形因素的影响。在有效划分研究区现代沉积环境的 3个粒度参数中,砂粒含量是受物源条件影响最为显著的参数,分选是对地形与流场相互作用最为敏感的参数。偏度对研究区沉积环境差异的敏感性是有限的。峰度几乎不能作为研究区沉积环境划分的粒度参数。水动力条件的特殊性值得在沉积环境的划分中予以足够重视。     

南黄海中部沉积物岩芯常量元素组成与古环境

南黄海中部三个晚第四纪沉积物岩芯的粒度和常量元素组成研究表明,岩芯YS1和YS2沉积物组成接近,而与YS3沉积物明显不同.根据元素地球化学参数推测沉积物的来源不同,YS1和YS2沉积物主要来自中国大陆,以长江沉积物为主;而YS3沉积物则主要来自朝鲜半岛,长江和黄河的细粒沉积物可能通过黄海暖流输运而影响该岩芯沉积.南黄海中部沉积物受黄海暖流的影响显著,暖流形成前后的沉积物物源及沉积环境并不相同.黄海暖流靠近中国大陆一侧沉积区域的沉积环境由于气旋型涡旋的影响,水动力环境较弱,粒径较细,沉积速率缓慢;而靠近朝鲜半岛一侧的粗粒沉积物则由于靠近南黄海东北部的潮成砂体区,水动力环境相对较强,沉积物颗粒较粗,沉积物的形成过程与中部明显不同.     

海南岛崖州湾宁远河河口区现代沉积特征

崖州湾宁远河河口区位于海南岛南侧,是以陆源为主、沉积环境相对简单的小型河流入海沉积区。分别在宁远河中游、下游、河流两侧海岸带以及近岸300余米的滩坝处,采集了5根重力柱状样、55个底质沉积物样品,通过粒度分析和同位素测试,对研究区近代沉积物沉积环境、空间展布规律和水动力演化规律进行了详细探讨。结果发现,研究区主要以河流三角洲沉积为主,在空间上,根据沉积物粒度和分选将研究区划分为五类沉积环境分区;在时间上,近百年来不同地区的水动力变化有所区别,入海口附近区域水体动荡随时间变化频繁;而河道上游附近区域水体条件变化小,形成明显的沉积旋回。     

淮北煤田芦岭井田二叠纪含煤岩系原生沉积构造序列与沉积环境

通过对保留在沉积物中与水动力条件有密切联系的原生沉积构造的观察和研究,分析了淮北煤田芦岭井田二叠纪含煤岩系属于以河流作用为主的建设性三角洲沉积环境,阐明了根据原生沉积构造序列解释沉积环境的基本方法.     

福建安海湾表层沉积物粒度特征及其现代沉积过程分析

通过对福建安海湾表层沉积物的粒度分析和对比,应用系统聚类分析、粒径趋势模型和切应力计算公式,探讨了研究区粒度的分布特征、沉积环境分区、表层沉积物输运趋势及其影响因素.研究结果表明,研究区包括6种表层沉积物类型,以黏土质粉砂和粉砂为主,沉积物大体呈现自海湾两侧潮滩向潮汐通道变粗的分布趋势.表层沉积物粒度的分布特征与水动力条件和物质来源密切相关,湾口附近及湾内深槽内,细颗粒的沉积物被再悬浮带走,粗颗粒的含量增大;在湾内潮滩上,悬浮物质因水动力作用逐渐减弱发生分选沉降,形成向岸变细的横向分异.海湾外泥沙随潮流不断地向海湾东侧岸滩运移,海湾周边陆源来沙由湾顶部往湾口方向下泄,两者是导致表层沉积物出现明显的顺时针方向汇聚趋势的原因之一;表层沉积物的输运趋势、悬浮泥沙的输运、潮滩植被与湾口沙嘴的遮蔽效应共同影响了研究区内浅滩地形的形成和变化.研究区可分为四类沉积环境区,以潮滩和潮汐通道环境为主,不同沉积区内的粒度参数、粒级频率和敏感粒级均有差异,动力条件差异和不同物源的影响程度是现代沉积环境格局的主要影响因素.     

金沙江乌东德水电站坝址河床深厚覆盖层勘探取样与 试验研究

河床深厚覆盖层勘探取样与试验研究是我国西部水电工程勘察中最常见技术难题之一。金沙江乌东德水电站坝址河床覆盖层厚一般52～65m,冲积、崩积及滑坡堆积等混杂,物质组成与结构不均,因坝址适宜修建混凝土拱坝,高围堰与深基坑稳定问题突出。为了查明河床覆盖层的工程特性,本文采用不遗漏软弱层采取了标贯与钻探相结合的钻进方法,为获得原状样研制了单管式与双管内筒式锤击取样器,为分析研究其物理力学性质开展了大量原位测试(重型动力触探、超重型动力触探、旁压试验、抽水试验、声波测试、钻孔彩电等)及室内土常规试验、模拟级配样试验等,较成功地解决了河床深厚覆盖层的勘探与试验难题,为乌东德水电站围堰与基坑工程设计参数的确定提供了可靠依据。     

Geotechnical Characteristics of Volcanic Soils Taken from Recent Eruptions

Recent volcanic eruptions at Mt. Unzen (Japan) in 1990 and Mt. Pinatubo (Philippines) in 1991 produced voluminous amounts of ash and sediments which inundated widespread areas. In later rehabilitation and reconstruction, it is practical and economical to use these freshly deposited sediments as materials for foundations and embankments. However, the geotechnical properties of young volcanic products have not been fully investigated. Accordingly, we investigated the geotechnical characteristics of volcanic soils associated with three recent eruptions, namely, the Unzen and Izu-Oshima eruptions of 1990 and 1986, respectively, in Japan and the Pinatubo eruption of 1991 in the Philippines. We specifically investigated index properties, permeability and compaction characteristics, and strength and deformation behavior in drained conditions. Additionally, we examined the dynamic properties and liquefaction characteristics of samples taken from Mt. Pinatubo. The results showed that the geotechnical characteristics of the deposits generally varied with the sampling sites. Depending on the location, either upstream or downstream from a volcano, the preferential sizing due to alluvial deposition affects engineering properties of the deposits. For example, volcanic sediments upstream from Mt. Pinatubo have high compressibility and low cyclic strength, whereas those taken downstream show dilative tendencies and high liquefaction strength.     

琼州海峡西线跨海通道工程地质评价

为开展琼州海峡跨海通道地壳稳定性评价,避免潜在的地质灾害对跨海通道工程安全性产生不利影响,利用侧扫声纳、单道地震、多波束等地球物理探测方法对琼州海峡海底展开了地形地貌调查,获得了琼州海峡跨海通道工程区海域活动断层分布、西线规划区地形地貌及地质条件等基础地质资料。工程地质评价认为西线线路断裂、地震、火山活动性弱,海底水深小、地形较为平坦、地貌简单,上新世望楼港组低液限粘土及上新世浅海相砂层作为基础持力层,岩土工程力学性质尚可,利于开展跨海通道桥梁方案施工。规划线路穿越1处侵蚀沟槽,影响长度约5 km,地形高差达60 m,且线路东临1处海釜,分布有陡坎,且部分地段分布有滑塌堆积。建议西线线路北段局部西移约1.5 km,同时关注西口潮流侵蚀沟槽、规划区南部淤泥质软土、古河道砂性土沉积、海峡谷底活动沙坡等不良地质作用影响。      

Geotechnical mapping for alluvial fan deposits controlled by active faults: a case study in the Erzurum,NE Turkey

Erzurum, the biggest city of Eastern Anatolia Region in the Turkey, is located in Karasu Plain. Karasu Plain, located on the central segment of the Erzurum Fault Zone, is an intermountain sedimentary basin with a Miocene-Quaternary volcanic basement, andesitic-basaltic lava flows and fissure eruptions of basaltic lava. It was filled in the early Quaternary by lacustrine fan-delta deposits. The basin is characterized by NNE-SSW trending sinistral wrench faults on its eastern margin and ENE-WSW trending reverse faults on its southern margin. Both systems of active faults intersect very near to Erzurum, which is considered to be the most likely site for the epicenter of a probable future large earthquake. Historical records of destructive earthquakes, morphotectonic features formed by paleo-seismic events and instrument seismic data of region indicate to a very high regional seismicity. The residential areas of Erzurum are located on thick alluvial fan deposits forming under the control of faults on the central segment of the Erzurum Fault Zone, which is one of the most active fault belts of the East Anatolian Region. Over time, the housing estates of city such as Yenisehir and Yildizkent have been expanded toward to the west and southwest part of Erzurum as a consequence of rapid and massive construction during the last 30 years. Geotechnical investigation has therefore been undertaken the residential areas of city in order to characterize geotechnical properties over the varied lithologies examine the potential for geotechnical mapping and assess the foundation conditions of the present and future settlement areas. The geological field observations and operations have been performed to make the soil sampling and characterize the lateral and vertical changes in thickness of the alluvial deposits in trenches, excavations and deep holes with 6–12 m sections. The soil samples have been subjected to a series of tests under laboratory conditions to obtain physical and mechanical properties. Furthermore, the standard penetration tests have been applied to the soils under field conditions. The geological field observations, geotechnical data and distribution of bearing capacity have been considered for the geotechnical mapping. Based on the geotechnical map, there are five geotechnical zones distinguished in the study area.     

长江下游地区软土工程地质特征及其成因类型分析

在长江下游地区软土分布广泛,在工程建设中以软土为地基和作为路堤填料情况越来越多,由于软土最突出的特征是孔隙比大、高压缩性、高含水率、强度低,而且不同成因的软土,其工程地质性质也有较大的差异。在工程中若处理不当可能会产生诸多岩土工程问题甚至造成工程事故。因此,正确认识软土的工程地质性质是非常重要的。本文就长江下游地区的软土工程地质性质作以分析,并从软土矿物成分探讨其成因类型,为软土正确处理和利用奠定理论基础。     

新时代岩土力学基本问题探究北大核心CSCD

“一带一路”新时代背景下大规模的工程建设,推动着岩土工程学科的繁荣和蓬勃发展。土动力学、非饱和土与特殊土力学与环境岩土工程是未来土力学的重点研究方向,有必要进行系统梳理分析。本文从土工动力测试技术、动本构关系和土-结构动力相互作用方面对土动力学的主要内容进行了阐释,然后从非饱和土有效应力原理、非饱和土本构模型及黄土力学特性方面对非饱和土与特殊土力学的基本理论进行了分析,最后对垃圾填埋处置和水土污染等环境岩土工程亟待解决的问题进行了探索,并提出了合理的应对措施。土力学学科面临着极大的发展机遇,也面临着严峻的挑战,这一系列核心问题的解决,必将为全面提升岩土工程项目建设的质量和效益作出贡献。     

Environmental geological and geotechnical investigations related to the potential use of Ankara clay as a compacted landfill liner material, Turkey

Clay-bearing Upper Pliocene red clastics and Quaternary alluvial deposits occupy the Ankara basin. The clayey levels of the Upper Pliocene deposits, referred to as Ankara clay, is considered as a source for compacted clay liners due to their low coefficients of permeability and widespread distributions throughout Ankara. This study investigates the geological, geotechnical and mineralogical properties of the founding clayey soils at two sites of the Ankara region. The geotechnical index properties along with the hydraulic conductivities of the clayey soil samples collected from these sites were determined. A mathematical relation between the clay mineralogical content and hydraulic conductivity was established. The results of this investigation show that, from a geotechnical point of view, Ankara clay may be regarded as a highly suitable material for a compacted clay landfill liner given that its mineralogical compatibility with leachate is confirmed.     

Geotechnical evaluation of Turkish clay deposits: a case study in Northern Turkey

Clay deposits in Oltu-Narman basins (Erzurum, northern Turkey) have been studied to determine their engineering properties and to evaluate their uses for geotechnical applications. These deposits are concentrated in two different stratigraphic horizons namely the Late Oligocene and the Early Miocene sequences. Clay-rich fine-grained sedimentary units are deposited in shallow marine and lagoonar mixed environments. Their clay minerals originated by the alteration of Eocene calc-alkaline island-arc volcanics, preferably from pyroclastics (trachite and andesite flow), which form the basement for the Oltu depression. Smectite group clay minerals are found abundant in clay deposits. The experimental results show that the clay soils have high plasticity behaviors and low hydraulic conductivity properties. The optimum water content, the free swell, and the swelling pressure of clay samples decreased and the maximum dry unit weight of clay samples increased under high temperature. Consequently, it is concluded that the expanding of clay soils is an important soil problem that cannot be avoided in the significant parts of Oltu city and its villages. However, the soils of clay-rich layers in the outcrops-section of clay deposits can be successfully used to build compacted clay liners for landfill systems and to construct vertical and horizontal barriers for protection of ground water and for preventing soil pollution in geotechnical applications.     

山西中奥陶世石膏岩的成因类型及生成环境

山西中奥陶世石膏岩的沉积受到机械沉积作用的影响。区内九种石膏岩分别是不同水深条件下的沉积及交代产物,并可归纳为浪基面下洼地、浅水、滩岛潮坪等三种沉积环境。在空间上,它们彼此依存、转换并连为一体形成一个巨大的浅水蒸发岩沉积。     

On the black cotton soils of North Cameroon

During detailed geotechnical prospecting in North Cameroon, extensive black cotton soil deposits were encountered. Based on classification tests, three samples were selected for mineralogical analysis. The results indicated that the predominant clay mineral was the halloysite governing the geotechnical properties and behaviour of the cotton soils. New correlations were established between clay mineral content and Atterberg limits of the investigated materials.