武昌地区含粘性土粉砂承载力探讨

以武昌某高层建筑群岩土工程勘察为例,采用规范查表、理论公式计算、现场载荷试验等方法,并结合物理力学指标特征对含粘性土粉砂的承载力进行分析,结果表明：武昌地区含粘性土粉砂是一种有别于一般粉砂、粉土和粘性土的混合土,在工程性质上,它更接近于粘性土而非粉砂。含粘性土粉砂承载力的确定方法应以现场载荷试验和理论公式计算为主,且计算结果与载荷试验结果应具可比性。     

砂土地基和粉质黏土地基基坑悬臂开挖离心模型试验

分别开展砂土和粉质黏土两种典型土质条件下基坑悬臂式开挖离心模型试验,详细叙述试验过程中所要解决的关键问题,并提出合理的解决方案。通过对比分析两组试验结果,得到以下结论：非饱和土地基制备中参数控制困难,分层夯实法有待进一步改进,而砂雨法制备的砂土地基参数可控性更好;两组试验的结果有差异,砂土地基试验所呈现的土压力、地基变形、支护弯矩的变化规律更好,因此,岩土离心试验可适当考虑以砂土代替非饱和土;对于采用悬臂式支护结构的基坑,开挖引起的地表沉降曲线在砂土中呈指数型,而在粉质黏土中呈直线型;开挖引起的粉质黏土地基土体位移范围较砂土地基更大;开挖引起的砂土中挡墙弯矩较粉质黏土更大,砂土和粉质黏土中最大弯矩位置都随开挖逐渐下移;在砂土试验中开挖引起主动区土压力各处均减小,而在粉质黏土试验中开挖引起土压力在挡墙底有增大趋势。该基坑工程离心模型试验过程及数据处理方法可为进一步试验提供参考。     

Investigation of expansive soils in Obhor Sabkha,Jeddah-Saudi Arabia

Expansion or swelling of soil is a worldwide geotechnical problem that occurs in arid and semiarid regions where sabkha soils may occur as well. Expansive soil is dominated by the presence of active clay minerals. The expansive and sabkha soils are characterized by a large seasonal variation in soil moisture content leading to a large change in the volume and the consistency of the soil and, thus, causing serious damages to buildings and infrastructure. Although sabkha soil covers large and strategically important areas along the Red Sea and Arabian Gulf coasts in Saudi Arabia, no one paid proper attention to the type of clay minerals in those soils or to their expansion potential, which is a crucial step prior to any construction. The geotechnical properties, active clay mineral types, and the degree expansion potential of soils were investigated in Obhor area at the north of Jeddah City. Twenty disturbed soil samples were collected at depths of 80 and 120 cm. Three different types of soils are identified: clayey soil with high plasticity, clayey soil with low plasticity, and poorly graded silty to clayey sand soil. Furthermore, active clay minerals were identified with a significant proportion of montmorillonite (14.24 %), illite (24.65 %), kaolinite (28.78 %), and chlorite (32.34 %). The results indicated that a considerable part of the study area has high expansion potential, but most parts of Obhor area have low to none potential of soil expansiveness.     

Study on the quantitative relationship between soil in situ strength and drilling parameters

The rational use of drilling parameters is a hot issue in the field of geotechnical engineering and geological engineering. A new method, for evaluating the bearing capacity of soils using drilling parameters was proposed. First, through the mechanical analysis of the drill bit, the preconditions and theoretical formulas for calculating the bearing capacity of soils using the bit’s torque are clearly defined. Next, drilling tests and dynamic cone penetration tests were performed on miscellaneous fill, silty clay, sandy clay, medium coarse sand and gravel sand, and the empirical formula for calculating the bearing capacity of these soils were given. Then, using the new method and the empirical formula, the bearing capacity of the soil under the roadbed was examined. The test results show that the bit’s torque is a good parameter for the evaluation of the bearing capacity of the soil. Finally, the application scope of the new method and the empirical formula is discussed, and the subsequent research directions are pointed out.     

The engineering-geological characteristics and classification of the major superficial soils of the Niger Delta

A study of the engineering geological properties, distribution and classification of the major superficial soils of the Niger Delta was carried out as part of a study programme to provide the much needed information and data for the infrastructural development of the region. Four major superficial soil groups were recognized on the basis of similarity in geotechnical, geological and geomorphological characteristics. The soils are generally fine grained and their geotechnical properties revealed that they are essentially clays with varying proportions of sand, silt and organic matter. The clay, silt and organic contents increase seawards. The values of the various geotechnical parameters are mainly influenced by the amounts of clay (and/or sand) and organic matter.     

2017年银川盆地1:50 000平罗站幅工程地质钻孔及取样土工试验数据集

本数据集是作者2017年在银川盆地平罗站幅施工的14个工程地质钻孔岩心中采集的234个岩土样品,经过测试分析后所得的共2 602组测试数据。这些数据主要体现了土体的抗剪强度、压缩模量、颗粒成分等。图幅内第四系分布广泛,厚度大,为区内主要的工程地质岩组,且成因多样,从西到东主要包括：上更新统洪积层,岩性主要为砾石、砂砾石;全新统灵武组细砂土;全新统湖沼积层,岩性主要为淤泥、砂质粘土及粉砂;全新统风积层,岩性主要为土黄色中-细砂、粉砂。其中,全新统灵武组占据了图幅大部分区域,岩性主要为细砂、粉砂、砂质粘土等。钻孔揭示,银川平原区地层纵向上以河湖相细砂、粉砂为主,夹粉质粘土,局部钻孔含卵砾石层。样品测试数据分析显示,图幅区内碎石土、冲积砂土、粘性土具较高的抗剪强度,工程地质条件较好;而图幅西北部砂岩、泥岩由于中等到强风化程度,且有软弱夹层,工程地质条件较差。湖沼积成因的淤泥、砂质粘土及粉砂工程地质性质亦较差。本次图幅区内的工程地质钻探工作施工规范,测试分析均由具备国家资质的实验室承担,得到的数据质量可靠,真实反映了该区域内地层信息及岩土物理力学性质。     

MK模型的拟合方程和预测方程在土-水特征曲线中的应用及参数敏感性分析

土-水特征曲线可以预测非饱和土的各种性质（如：非饱和渗透系数、剪应力和热学性能等）。但测量土-水特征曲线耗时久且花费昂贵。为了解决这一问题,目前,很多研究都致力于从基本的岩土工程性质预测土-水特征曲线。基于此,以MK（Modified Kovács）模型的2种形式（拟合方程和预测方程）为土-水特征曲线模型,以Matlab编程语言中的cftool为拟合工具,以西宁黄土、粉砂土、红黏土和冰碛土4种细粒土为研究对象,对比拟合方程和预测方程描述细粒土土-水特征曲线的效果和差异,分析MK模型中黏附饱和度 1解 的变化规律,提出了基于MK模型的饱和度进行参数敏感性分析的计算公式。结果表明：拟合曲线和预测曲线在描述4类典型细粒土土-水特征曲线时均具有较好的效果,但拟合曲线整体上优于预测曲线;土壤质地和黏粒含量影响 值;饱和度对拟合参数 的敏感性较大,对拟合参数 的敏感性较小。     

Study on the swelling behaviour of blended clay–sand soils

Soils containing expansive clays undergo swelling that can be both detrimental and beneficial in various applications. In the Arabian Gulf coastal region, natural heterogeneous soils containing clay and sand (tills, shales, and clayey sands) support most of the civil infrastructure systems. Likewise, mixes of clay and sand are used for local earthwork construction such as roads and landfills. A clear understanding of the swelling behaviour of such soils is pivotal at the outset of all construction projects. The main objective of this paper was to understand the evolution of swelling with increasing clay content in local soils. A theoretical framework for clay–sand soils was developed using phase relationships. Laboratory investigations comprised of mineralogical composition and geotechnical index properties of the clay and sand and consistency limits, swelling potential, and morphology of clay–sand mixes. Results indicated that soil consistency of mixes of a local expansive clay and an engineered sand depends on the weighted average of the constituents. Mixes with 10% clay through 40% clay capture the transition from a sand-like behaviour to a clay-like behaviour. Influenced by the initial conditions and soil matrix, the swelling potential of the investigated mixes correlated well with soil plasticity (SP(%) = 0.16 (I _p)^1.188). The parameters sand void ratio and clay–water ratio were found to better explain the behaviour of blended clay–sand soils.     

黄河三角洲粉质土的动模量和阻尼比试验研究

结合室内共振柱和动三轴实验,对黄河三角洲饱和原状粉质土体(粉土、粉砂、粉质粘土)动模量和阻尼比的影响因素和发展规律进行了详细的研究。研究表明,在粉粒和粘粒含量对动模量的共同影响中,粉粒含量起着举足起重的作用;侧限压力对归一化剪模比和阻尼比的影响均较显著,相比粘粒含量的影响不大。通过与Seed建议的砂土及饱和粘土的G/Gmax~曲线和~曲线进行对比,结果显示研究区的粉质土相比一般的砂土和饱和粘土而言,其动力变形特性更接近于砂土,但是与砂土也存在着非常明显的差异;其发展规律与其他地区沉积粉质土也较为不同,具有明显的区域性。采用修正了的Hard in-D rnevich模型和对数模型分别对G/Gmax~曲线和~曲线进行拟合,给出了三类粉质土的归一化动力变形G/Gmax~/r关系曲线,对模型中有关参数的影响因素做了初步的探讨。     

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.     

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.     

障壁岛—潟湖沉积特征及模式:以美国普拉姆岛上更新统—全新统为例*

普拉姆岛(Plum island)是美国东北部缅因湾最大的障壁海岸,岛内向陆一侧为新英格兰地区最大潟湖和沼泽区,它们是晚第四纪末次冰期冰川作用和冰后期海岸作用的沉积响应。通过普拉姆岛研究区上更新统—全新统160个钻孔描述,识别出8种沉积物: 泥炭、冰川黏土、黏土、粉砂、细砂、中粗砂、砾、坠石。根据沉积物类型及其组合特征,结合沉积环境,共划分出8种沉积微相: 障壁沙丘、滨岸沙、水下临滨沙、河道、潮汐水道、潟湖、潮坪、沼泽。研究区在晚第四纪末次冰盛期(MIS2)被劳伦斯蒂德冰盖(Laurentide Ice Sheet)覆盖,发育冰川地貌,冰川泥覆盖在基岩之上,形成底层沉积; 冰后期(MIS1),冰盖消融,海平面发生变化,在冰川地貌鼓丘附近形成沙坝,最终沉积演化为障壁岛—潟湖环境,潟湖通过潮汐水道与广海相连通。     

Mapping the Pliocene Clay Deposits Using Remote Sensing and its Impact on the Urbanization Developments in Egypt: Case Study,East Sohag Area

In the current study, Thematic Mapper image was compiled along with field and laboratory investigation results to map the Pliocene clay deposits. These deposits have high swelling potential; consequently they will have a negative impact on the urbanization expansion surrounding the flood plain zone (Low desert zone) in Egypt. Principle Component and Minimum Noise Fraction techniques with the help of supervised classification were successful in the mapping of these deposits. The interpretation shows that the Pliocene clay deposits occupy most of the wadis terraces and part of the wadis floors, and sometimes they covered by Quaternary deposits (1–5 m of sand and gravel). The physio-chemical characteristics of these deposits indicate that the Pliocene clay ranges from silty clay to clay with small amounts of sand. Laboratory analysis (Atterberg limits, saturation degree, and cation exchange capacity) indicate the swelling characteristics of the Pliocene clay. Different classification systems were applied and all reveal the expansive nature of this soil, which should be taken into account for future development in the area.     

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.     

Evaluation of secondary compression of sands and silts from CPTU

The estimate of secondary compression behaviour of sandy and silty deposits is not routinely taken into account in the classical settlement calculation, due to its generally limited contribution to the total amount of strains. However, such soils exhibit a non-negligible time-dependent behaviour and the prediction of their long-term response may sometimes be important.

This paper explores the capability of the piezocone test as an effective tool to estimate the one-dimensional secondary compression characteristics of sands and silts. The approach is mainly based on the observation that frictional response essentially governs both secondary compression of granular soils and cone resistance, hence it seems reasonable to establish a valid correlation among them.

The study uses part of the field data assembled over the last years at the Treporti Test Site (Venice, Italy), within an extensive research project aimed at analysing the stress-strain-time response of the predominantly silty sediments forming the Venetian lagoon subsoil.

Empirical, site-specific correlations for estimating the secondary compression coefficient from cone resistance are proposed. The regression analyses indicate that the estimate is slightly improved if the cone resistance-based correlations include a variable accounting for the different pore pressure response associated to the drainage conditions around the advancing cone.     

层状土毛细水上升过程中Lucas-Washburn模型评价及修正

受界面效应影响,毛细水在层状土中运移规律还难以用描述均质土中水分运移规律的Lucas-Washburn（LW）渗吸模型进行描述。基于此,本文设计了层状土室内模型试验,采用分布式的主动加热光纤法（简称AHFO）监测毛细水上升过程。根据AHFO测试结果,进一步对LW模型进行了修正,提出了适用于描述层状土中毛细水上升规律的ILW模型,并对ILW模型进行了试验验证。试验结果表明:（1）当毛细水湿润锋抵达“黏土（下部）-砂土（上部）”界面时,会产生“毛细屏障作用”,从而导致上部砂土中毛细水含水率急剧下降;（2）“毛细屏障作用”由砂土和黏土中的基质吸力不均衡造成,基质吸力大小由含水率决定;（3）当毛细水湿润锋抵达“砂土（下部）-黏土（上部）”界面时,在界面处出现“反毛细屏障作用”,从而导致上部黏土层中的含水率比相邻下部砂土层含水率更高;（4）虽然常见的LW模型可准确预测均质土中毛细水上升高度及速率,但受“毛细屏障作用”和“反毛细屏障作用”影响,LW模型在层状土中失效;（5）相比LW模型,ILW模型精度更高,能够更加准确地描述层状土中毛细水上升规律。     

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.     

鄂尔多斯盆地东缘大宁—吉县地区山西组页岩岩相与沉积相特征

以鄂尔多斯盆地东缘大宁—吉县地区二叠系山西组为研究对象,综合应用岩心、薄片及测井资料,开展山32亚段岩相类型、岩相组合和沉积相研究,研究结果表明:山32亚段包括粉砂质泥岩/页岩相、纹层状层理含粉砂泥岩/页岩相、透镜状层理粉砂质泥岩/页岩相、钙质页岩相、煤层、碳质页岩相、黑色页岩相、波状层理泥质粉砂岩相、交错层理中—细砂...     

福州地区典型土动剪切模量与阻尼比的试验研究

通过对福州地区淤泥、淤泥质土、粉质黏土、粉质黏土与粉砂互层土、粉砂、残积土等6类典型土的共振柱试验,详细探讨了围压大小、土的性质对这6类典型土的动剪切模量G及阻尼比? 的影响。通过试验和理论分析,给出了福州地区6类典型土在不同围压下的G/Gmax和? /?max随? 变化的平均曲线及其参数的推荐值,并定量地给出围压对这6类典型土G/Gmax和? /?max随? 变化的平均曲线的参数的影响规律,对实际工程具有一定的借鉴作用。     

江汉平原土壤饱和渗透系数变化规律及影响因素

目前对影响土壤饱和渗透系数规律的机理缺乏深刻认识.以不同沉积环境、不同岩性及不同土地利用方式的江汉平原汉江下游浅层土壤为对象,采用改进的TST-55型土壤渗透仪开展室内变水头达西实验.结果表明,研究区内土壤饱和渗透系数平均值为4.94×10-5cm/s,服从对数-正态分布;粉砂壤土冲积物和湖积物的饱和渗透系数平均值为3.53×10-5cm/s和1.98×10-5cm/s,粉砂质粘壤土中,两者分别为8.13×10-7cm/s和5.88×10-7cm/s,同一岩性冲积物的饱和渗透系数较湖积物大;冲积物中,砂壤土、粉砂壤土和粉砂质粘壤土饱和渗透系数平均值为1.98×10-5 cm/s、3.53×10-5 cm/s和8.13×10-7 cm/s,表现为砂壤土>粉砂壤土>粉砂质粘壤土;耕作土壤中,粉砂壤土、粉砂质粘壤土的饱和渗透系数平均值为3.75×10-5 cm/s和8.11×10-7cm/s,非耕作土壤中,两者分别为1.88×10-6cm/s、5.93×10-7cm/s,同一岩性耕作土壤饱和渗透系数较非耕作土壤大.