渤海湾西部表层沉积物粒度特征与沉积混合

根据渤海湾西部135个表层沉积物样品的粒度分析结果,分析了表层沉积物的粒度特征与规律。整体上由研究区东北部沿海岸向南沉积物粒度变细,由砂和粉砂质砂变为砂质粉砂,再变为粘土质粉砂。沉积物粒度频率曲线显示,由研究区东北部至北部,沉积物粗组分含量减少,由单峰逐渐过渡为主峰或弱峰,到中部粗组分减少为粗尾形态,到南部粗组分几乎缺失;而沉积物细组分的变化趋势则与之相反。沉积物粗组分在粒度频率曲线上的表现由单峰逐渐过渡至主峰或次峰,粗峰含量减少,到中部粗组分减少为粗尾形态,到南部粗组分几乎消失;而沉积物细组分的变化趋势则与之相反。沉积物粒度参数的平面分布规律和粒度参数之间的相关性变化形态显示出粗细2种母质组分以不同比例的沉积混合的特征,即来自东北部的粗组分与来自南部的细组分发生混合,这可能主要与区内双向的沿岸环流输运有关。     

海南四更沙海域沉积物分布及其受控机制

基于海南西部四更沙及其邻近海域185个底质的粒度数据,并结合研究区动力状况和水深地形特征,研究表层沉积物的组分和类型分布、粒度参数及其沉积环境分区。结果表明:①研究区沉积物类型多样,包括12种沉积类型,以砂质粉砂、粉砂、粉砂质砂和含砾砂为主,沉积物平均粒径变化范围较大(-0.70~7.13 φ),且大体呈现由北向南逐渐变细的分布趋势;②运用Fleming的三角图式,结合物源状况及地形地貌条件,对沉积环境进行划分,将研究区划分为四更沙岸外海滨沉积区、北黎湾中部沉积区和八所港近岸沉积区等3个沉积区;③研究区沉积物分布特征受沉积物来源和水动力及地形条件共同影响。横向分布上,西部主要受强潮流输沙影响,东部近岸则主要受波浪掀沙和搬运作用影响,表现为两侧粗,中间相对较细的特征。纵向上,四更沙岸外海滨沉积区,沉积物主要受昌化江影响,粒径粗,表现为河口沉积特征;北黎湾中部沉积区,沉积物粒径分布范围广,表现为较强的过渡区特性;八所港近岸沉积区,沉积物粒径最细,泥沙来源主要为外海带来的泥沙。     

黄河三角洲饱和粉质土液化性能试验研究

在黏粒含量和干密度恒定的情况下,进行了一系列重塑黄河三角洲饱和粉质土不排水动三轴试验,试样直径为50 mm、高为100 mm,重点研究了有效围压、动荷载和粉粒含量等因素对饱和粉质土液化特性的影响。试验结果表明:（1）在粉粒含量不小于50%的情况下,粉粒含量的增加降低了黄河三角洲饱和粉质土的液化势;（2）重塑黄河三角洲饱和粉质土的动强度随有效围压的增大而增大,与初次液化振动次数的对数近似呈线性关系;（3）与砂土相比,粉质土的动孔压很难达到有效围压,并且随有效围压的增大,相同条件下动孔压达到有效围压的比率降低;随粉粒含量的增加,其对动孔压的影响有减小的趋势;粉粒含量的增大减缓了动孔压的增长;（4）根据本次试验结果,给出了重塑黄河三角洲饱和粉质土的动孔压计算模型及相关参数取值。     

渤海中部表层沉积物分布特征与粒度分区

为了解渤海中部海区表层沉积物分布特征与物质来源和水动力环境的关系,高密度采集了海区1448个表层沉积物样品,并进行粒度参数的相关分析。结果表明,研究区表层沉积物类型主要有砾石、砂质砾、砾质砂、砂、粉砂质砂、砂质粉砂、粉砂、黏土质粉砂、砂-粉砂-黏土和粉砂质黏土10种类型。海区中分布范围最广泛的是粉砂质砂和黏土质粉砂,而砾石和粉砂的分布范围相对较小。海区主要由老铁山水道、冲刷槽砂砾区、渤中砂质浅滩和辽东砂质浅滩、渤中粉砂质平原、渤海湾黏土层粉砂三角洲平原和渤西滨岸倾斜砂质平原五个沉积物粒度分区。主导海区沉积物分布模式的动力机制是进入渤海的黄海暖流余脉形成的渤海环流,另外,渤海海峡强潮流、辽东湾环流和莱州湾环流也是控制区域表层沉积物的重要动力因素。这些动力驱动因素促成了渤海物质与黄海物质之间“北进南出”的交换模式。     

中国东部海域表层沉积物粒度组成及影响因素

基于海洋区域地质调查获取的1 438个粒度数据,利用Folk分类方法将中国东部海域表层沉积物划分为砂质粉砂、粉砂质砂、粉砂、砂、砂质泥、泥质砂、泥7种沉积物类型,阐述了不同沉积物类型的粒度组成和参数特征.其中,砂质粉砂、粉砂质砂和粉砂是3种最主要的沉积物类型,分别占样品总数的34.70%、24.20%和15.51%.粉砂质砂呈条带状分布在研究区的南部且向北延伸.粉砂主要分布在长江口-浙闽沿岸、渤海西部和南黄海中北部.砂主要分布在东海外陆架、扬子浅滩和苏北浅滩、朝鲜湾等海区,其中在东海外陆架海区分布最广.影响沉积物分布的主要因素有物源、水动力环境以及水深、地形、地貌等.晚第四纪冰期旋回中海平面变化和海洋环流控制陆源沉积物的入海通量和陆架沉积体系的发育过程.综合沉积物物源供给、海洋环流、冰后期海平面变化过程,基于Folk分类的动力学属性和表层沉积物类型分布,将中国东部海域表层沉积物分布划分为河口沉积、陆架泥质沉积、潮流沉积以及残留沉积等分区.不同沉积分区的形成机制和影响因素差异显著,反映出在中国东部陆架的特殊地形影响下,不同海平面时期陆源碎屑物质的运移过程.      

广西膨胀土的孔隙结构特征

对冻干法制备的广西膨胀土不扰动样进行了微结构测试研究。通过压汞试验结果对膨胀土的孔隙分布进行分形研究表明其具有多重分维特征。对孔隙分布曲线拐点的物理意义进行了探讨,并用扫描电镜照片加以印证,认为可将膨胀土的孔隙划分为大、小、微3类,其中微孔隙为蒙脱石类晶层之间的宽度可变间隙。说明压汞试验无法提供微孔隙的信息,建议今后应重视膨胀土全孔隙分布的研究。     

海南昌化江入海口底表沉积物粒度特征及输运趋势

对海南岛昌化江入海口110个底表沉积物样品进行了粒度分析,并利用二维沉积物粒径趋势分析模型对沉积物粒度参数开展趋势分析.研究结果表明,按照Folk沉积物分类三角图解法,昌化江入海口外底表沉积物可划分为含砾砂、砂、砾质泥质砂、砂质砾、粉砂、泥、砂质泥、砾质砂、砂质粉砂和粉砂质砂共10种沉积物类型,其中砂和砾组分的分布范围...     

雷州半岛红树林湿地表层沉积物粒度分布特征

对采自雷州半岛8个红树林湿地典型分布区的37个表层沉积物样品进行粒度分析,结果显示:(1)研究区表层沉积物粒度组成粉砂含量最高,占52. 9%;其次为砂,占27. 8%;黏土含量最低,占19. 3%。(2)研究区表层沉积物有砂质粉砂、黏土质粉砂、砂和粉砂质砂4种类型,其中砂质粉砂和黏土质粉砂主要分布在南山、高桥和观海长廊等地,砂和粉砂质砂主要分布在特呈岛、企水等地。(3)研究区沉积物平均粒径为5. 7,沉积物颗粒整体偏细;分选系数平均值为1. 90,分选较差;偏态平均值为-0. 14,为负偏;峰态平均为1. 07,峰态等级为中等。(4)通过系统聚类分析方法将研究区沉积环境分为三种类型,不同沉积环境水动力条件和环境特征差异明显。(5)沉积物砂粒含量与有机质含量、盐度呈极显著的负相关关系,与p H值呈正相关;粉砂含量与有机质含量、盐度呈极显著正相关,与p H值呈负相关;黏土含量与有机质含量、盐度正呈相关,与p H值则呈负相关。     

滑坡冲击作用下的阶地砂质粉土层液化机理

为探究阶地饱和砂质粉土在黄土滑坡冲击荷载作用下的力学机理,选取泾阳南塬典型黄土滑坡LD37为研究对象。通过基本性质测试获取了阶地砂质粉土的物理、水理、颗粒级配和矿物组分等指标。采用自制冲击设备进行了3种饱和度条件下的冲击试验,并对水分迁移和剪切强度变化等问题进行了分析,在此基础上探讨了冲击液化机理。结果表明:冲击荷载会使砂质粉土内部的总应力与孔隙水压力剧增,在应力波的作用下,出现多个峰值,且孔隙水压力在1 s内难以完全消散;80%与90%饱和度的砂质粉土受冲击会在深度方向上形成不同程度的液化,而70%饱和度的砂质粉土受冲击后沿深度方向并未发生液化;砂质粉土发生冲击液化时下部水分会向上部迁移,导致其上部土层含水率骤增,剪切强度骤减;冲击液化过程可划分为初始阶段、冲击挤压阶段和冲击回弹阶段。砂质粉土的冲击液化机理是一种由于快速冲压土体的不排水行为,导致其颗粒原始骨架结构破坏重组,从而引起其内部孔压快速积累的一种液化行为。     

Effects of Non-Plastic Silts on Liquefaction Potential of Solani Sand

Loose saturated cohesionless soils are most susceptible to liquefaction, however there are strong historical evidence suggesting that soils containing fines such as silty sands are also prone to liquefaction during earthquakes. The liquefaction of silty sands has been observed in a number of recent case studies. This paper presents the effects of fine silts on liquefaction potential of sandy soil. Tests have been conducted on the vibration table at different accelerations and pore water pressure is measured. During the lab investigation, locally (Roorkee, India) available Solani Sand and Dhanauri Silt have been used. The soil samples have been prepared by varying silt content and the initial relative density. The results of the study performed are used to clarify the effects of non-plastic fines content on the Solani sand. As the silt content increases, the number of cycles required to produce maximum pore water pressure increases. For a particular level of excitation, rate of pore water pressure generation is maximum at critical silt content. It is observed that critical silt content to generate maximum pore water pressure is different for different accelerations. Further, effect of silt content is very much dependent on relative density.     

Undrained shear strength response under monotonic loading of Chlef (Algeria) sandy soil

During the last mid-century, the Chlef area was strongly affected by two earthquakes. From the geological context, there were numerous ejections onto the ground level of great masses of sandy soils and large displacements of various forms of some building foundations. These damages are due to soil liquefaction problem. This loss of shear strength can be attributed to many factors. History of recent cases indicates that sand deposited with silt content is much more liquefiable than clean sand. Therefore, a deep understanding of silty sand behavior is needed for the liquefaction assessment of silty sandy soils. Moreover, during seismic shaking, the post-liquefaction behavior of silty sand and, consequently, the stability of structures founded on liquefied soil depend on the steady-state shear strength of soil. The objective of this laboratory investigation is to show the effect of silt contents and the relative density on the mechanical behavior of such soils in monotonic loading. In this context, a series of undrained triaxial tests were performed on reconstituted saturated silty sand samples with different fines content ranging from 0% to 40%. In all tests, the confining pressure was held constant to 100 kPa. The fines content and the global void ratio are expressed by means of the equivalent void ratio. Linear correlations relating the undrained residual shear strength of loose, medium dense, and dense (D _r?=?12%, 50%, and 90% before consolidation) sand–silt mixtures to the equivalent void ratio are obtained. The concept of the equivalent void ratio will then be used as a key parameter to express the dilatancy behavior of both clean and silty sand soils. Moreover, from the experimental results obtained, it is clear that the global void ratio cannot be used as a state parameter and may not represent the actual behavior of the soil as well.     

全风化花岗岩孔径分布-颗粒组成-矿物成分变化特征及指标相关性分析

孔径分布、颗粒组成和矿物成分是全风化花岗岩微观和结构特征的3个主要方面,也是决定其工程地质性质的关键因素。理论研究和实际工程中,常用大、中小和微孔隙、角砾、砂粒和粉粘粒、三大矿物（石英、长石和粘土矿物）含量等指标表征这3方面的特征。3方面指标在一定范围上变化幅度多大？数值间相关性及作为土结构模型组份因子,它们相对权重多大？通过对香港九龙两处边坡51件全风化花岗岩试样压汞测试、颗粒分析和X射线衍射（XRD）等微观结构特征分析,结果表明：两处边坡粗粒和细粒结构全风化花岗岩有明显区别,前者主要属于砾石土和砂砾土,部分为含砾土,大孔隙多,石英和粘土矿物多,而后者部分属含砾土,部分为细砂土和亚砂土,微孔隙多,长石多;两者长石和粘土矿物含量变化正好相反。借助于多因素关系矩阵法,对3方面共9个指标作相关分析发现,相关性较好的指标是：角砾和砂粒 (0.948);大孔隙和微孔隙(0.846);石英和长石(0.827);长石和粘土矿物 (0.747)。从土结构因子角度考虑,权重从大到小指标是：微孔隙、长石、粘土矿物、砂粒、角砾、大孔隙、中小孔隙、粉粘粒和石英。其分析结果可为该类土微观结构特征细化及分类提供依据,为其微结构力学研究提供基础材料。     

洞庭湖砂纹淤泥质土固结过程微观结构变化

砂纹淤泥质土是一种特殊的夹有微薄层粉细砂的洞庭湖湖相沉积软土,具有独特的薄砂层构造。该软土固结过程中的微观结构变化,对解释宏观的工程现象、揭示土体变形的本质和采取合理的地基处理措施具有重要意义。本文利用X射线微区衍射试验和扫描电子显微镜试验,研究洞庭湖砂纹淤泥质土的矿物成分和微观结构,同时结合固结试验探讨砂纹淤泥质土微观孔隙与结构单元体参数变化特征。研究结果表明:洞庭湖砂纹淤泥质土主要矿物成分为绿泥石、白云母和石英,微观结构为片状或板状聚体结构;随着固结压力增加,等效粒径增长呈先快速后放缓的规律,结构单元体形态参数则先增大后减小;砂纹淤泥质土压缩系数与竖直切面结构单元体定向概率熵呈明显负相关关系。     

Experimental evaluation of shear strength behaviour of plastic and non-plastic silts

Silt is available in many parts of the world in combination with sands and clays. However, due to lack of clear understanding of its engineering behaviour, most of the time it is interpreted in terms of either sands or clays. Structures that are usually built on silty soils are designed to take into account design procedures developed for sandy or clayey soils. Presence of silts in combination with varying amount of sand and clays produces silt that is either plastic or non-plastic in nature. Silt is available in and around the Delhi region, in a majority mixture along with fine sands, which is non-plastic in nature. On the other hand silty deposits found in offshore Bombay High region are found in abundance along with significant amounts of clays and are termed as plastic silts. In this paper a comparison of the stress-strain behaviour of plastic and non-plastic silts is carried out under triaxial compression loading during both drained and undrained conditions. Two representative samples each from Delhi and Bombay High regions were considered for this comparison and results of stress-strain under four sets of confining pressure are discussed in detail. It is observed from this study that behaviour of silts is mainly dependent on the composition and structure of the resultant soil matrix. It is concluded from the results that shear strength parameters as well as volume change/pore pressure response of silty soils is dominated by the constituent soil present along with the silt. It is seen from the comparative behaviour of non-plastic and plastic silts that the presence of sand and clays has a governing effect on pore pressure development and the resultant friction angle. The study also corroborated that the nature of silt is transitional both in the case of plastic and non-plastic forms.     

活性氧化镁碳化固化粉质黏土微观机制

以活性氧化镁碳化固化粉质黏土为研究对象,通过无侧限抗压强度试验、酸碱度测试、X射线衍射试验、压汞试验和扫描电镜试验,研究了不同初始含水率和碳化时间影响下活性氧化镁碳化加固粉质黏土的强度、pH值、碳化产物和微观结构等变化。根据碳化固化土强度与碳化产物含量及累积孔隙体积间的内在联系,提出了粉质黏土的碳化反应微观模型。结果表明：随碳化时间增加和初始含水率减小,碳化固化土的碳化产物含量增加、累积孔隙体积减小,同时氧化镁碳化加固土的强度提高;碳化固化土的pH值随碳化时间不断减小,而随初始含水率变化不大;最后提出了粉质黏土的碳化反应微观模型,确定了活性氧化镁固化粉质黏土在碳化约6.0 h时可获得最高强度。     

细粒含量对粉土动孔压发展模式影响的试验研究

采用多功能静动液压剪切仪进行了粉土动荷载下的孔压试验,探讨了黏粒含量和粉粒含量对重塑粉土动孔压发展的影响。试验模拟大震时细粒含量影响的孔压发展规律,对已有的指数形式孔压模式进行修正,以便模拟初始液化发生后达到一定液化程度的实际情况,该模式包含2个参数a和b。研究结果表明,细粒含量对粉土动孔压发展影响较大,其影响主要体现在孔压发展模式参数b上。粉土中粉粒含量与孔压参数b的关系呈单调的线性关系,而黏粒含量与孔压参数b的关系则不是单调的线性关系,是在黏粒含量为8 %时孔压参数b达到的最大值,试验数据验证该修正的动孔压模式有更广泛的应用性。     

人类活动影响下伶仃洋沉积格局演变特征

根据2016年伶仃洋128个表层沉积物粒度参数以及前人对伶仃洋表层沉积物的研究成果,结合Flemming沉积动力判别图解和粒径趋势分析模型（GSTA）,分析伶仃洋40年来的沉积格局演变特征,并探讨了人类活动在伶仃洋沉积格局演变中的作用。结果显示:1）2016年,伶仃洋表层沉积物中粉砂组分含量最多（56.67%）,黏土组分含量其次（26.08%）,砂含量最少（17.23%）,湾内表层沉积物总体较细,主要有砂、砂—粉砂—黏土、砂质粉砂、粉砂质砂和黏土质粉砂5种类型,各类型沉积物呈现斑块状分布。2）近40年来,伶仃洋表层沉积物的平均粒径、粒级组分的空间格局发生了显著变化,从之前的条带状分布变为斑块状分布,但沉积格局的剧烈演变主要集中于2004—2016年这十多年间,Flemming三角图分区变化显示出40年来伶仃洋沉积环境整体表现出动力增强的趋势。3）受人类大规模采砂影响,中滩区域原有的完整沉积中心被分散,分别向北和向南形成“两格局、三中心”的新型沉积模式,从而改变伶仃洋的沉积物源—汇过程。4）伶仃洋沉积物空间分布、沉积动力环境、运移趋势等特征的变化与采砂、航道浚深等人类活动有着密切的联系,反映出人类工程活动已成为影响伶仃洋沉积格局演变的重要因素。     

Microstructures of different soil layers caused by the high-rise building group in Shanghai

The engineering characteristics of soils are controlled by the state of the microstructure of soils to a great extent. With the withdrawal of groundwater controlled reasonably, the engineering-environmental effect of the high-rise building group becomes the main cause of land subsidence in Shanghai. This paper studied the microstructure of each soil layer under the building loads in the centrifuge model by the scanning electron microscopy and the mercury intrusion porosimetry (MIP) for qualitative analysis and quantitative analysis, respectively. The shape, size and contact condition of the basic unit of the soil microstructure were analyzed. The pore structure of each soil layer was studied by MIP, and the pore distribution of each soil layer was studied by the fractal theory. The ink-bottle effect exists in the intrusion stage in the MIP test. There are four different fractal dimensions for silty clay of layer No. 4 and clayey soil of layer No. 8 and three different fractal dimensions for silty sand of layer No. 7 and layer No. 9. The micro and macro mechanisms of land subsidence caused by the high-rise building group were analyzed.     

土体适用MICP技术的渗透特性条件研究

影响土体适用微生物诱导碳酸钙沉淀（MICP）技术的主要因素有颗粒的有效粒径、孔隙直径、颗粒级配以及水动力学参数等,实际工程土中复杂的孔隙结构难以通过单一的参数来衡定,而土体的渗透性能够综合反映诸多因素。针对分步、低速工艺下的定容量饱和渗透灌浆,提出了在满足土壤颗粒粒径和微生物尺寸相容性的前提下,以渗透系数表征的土体适用MICP技术的条件判断公式;并通过涵盖砂土、粉土、砂质黏性紫色土、膨胀土等9种土（控制粒径 0.040～0.913 mm,初始孔隙率 31.5%～54.9%）的固化试验、渗透试验和强度试验进行了验证。结果表明：结合渗透性折减参数 值的选取（无黏性土 ,黏性土 ）,渗透条件Ⅲ可适用于多种土体;渗透条件Ⅰ适用于MICP技术广为应用的砂土。同时得出了灌浆浆液总量和灌浆总时长的计算公式,为MICP固土技术可行性评估和进一步推广应用提供参考。     

广从断裂带金沙洲段最新活动性研究

广从断裂带在金沙洲段以3条近平行的北东向分支断裂展布,钻孔岩芯及显微构造分析表明,研究区基岩受断裂活动影响无疑,且断裂活动时代较新。以金沙洲基岩之上普遍存在的土黄色-褐黄色粉砂质黏土(或黏土)标志层为样品进行粒度分析,所得粒度参数及概率累积曲线表明,该层沉积物可与珠江三角洲其他区域进行对比,为晚更新世晚期(10~20 ka B.P.)沉积,该地层之上灰黑色-黑色淤泥质层(或细砂层)出现了明显的全新世高海面沉积异常,淤泥层中腐木的~(14)C年龄为6~7 ka B.P.,确认广从断裂金沙洲段的最新活动年龄为6~7 ka B.P.。