Geotechnical and mineralogical characteristics of marl deposits in Jordan

Marls and marly limestone deposits cover most of Northern Jordan, where Amman City and its suburbs are located. These deposits serve as foundations for most buildings and roads as well as fill material for structural back filling, especially road bases and sub-bases. The present study aims at investigating the geotechnical characteristics and mineral composition of the marl units of these deposits through field investigations and laboratory testing. Using X-ray diffraction technique along with chemical analysis, representative samples of marl horizons were tested for mineral composition, and for a set of index and geotechnical properties including: specific gravity, grain size, Atterberg limits, Proctor compaction and shear strength properties. The test results show a positive linear relationship as expected between the clay content and both liquid and plastic limits. The tests results also show an inverse linear relationship between the clay content and the maximum dry density in both standard and modified compaction. This is attributed to the adsorption of water by the clay minerals. The relationship is more prominent in the case of modified compaction test. The results also indicate a similar relationship for the angle of internal friction. No clear correlation between cohesion and clay content was apparent.     

滇西北红粘土的工程地质特性及其灾害效应

在野外地质调查的基础上,结合室内土工试验,系统分析了滇西北红粘土的物质组成、物性特征和工程地质特性,并以此为基础探讨了其地质灾害效应。研究结果表明：滇西北红粘土粒度组成主要以粘粒为主,粘土矿物成分比较复杂,在丽江以南其矿物成分主要以高岭石（K）为主,在丽江以北则以伊利石/蒙脱石（I/S）混层矿物为主。此外,滇西北红粘土具有含水量高、重度低、塑性高、膨胀性弱等物性特征,在天然状态下比较稳定,但是随着含水量的增加其土体强度大大降低,易引发滑坡、水土流失等地质灾害。     

湛江组结构性黏土区域微观结构特性研究

形成于早更新世的湛江组地层广泛分布于雷州半岛地区,其最为典型的灰色黏土因具有强结构性,在实际工程中出现了一系列岩土工程问题,为众多学者所关注。根据地层学研究结果,雷州半岛各区域的湛江组灰色黏土具有不同沉积环境。由于地质成因的差异,灰色黏土在不同区域表现出不同的工程特性。工程实际中,灰色黏土工程特性的区域性,使得工程界及研究者对于该土层的工程力学效益更是难以掌握。利用X射线衍射试验及电镜扫描试验,研究了不同区域灰色黏土的矿物成分及含量、微结构等微观结构特性。结果表明：不同沉积环境灰色黏土矿物成分及含量存在区域性差异,各矿物成分按照不同比例组合,形成的土体微结构区域特性明显。灰色黏土具有强结构性微观机制的揭示及区域差异性的分析,有利于对该层黏土的全面认知和利用。     

粘土矿物钝化改性和钝化机理初步研究

在岩土工程中,进行灾害防治和软基处理的一个核心问题是把粘土矿物由亲水性改造成疏水性,抑制和降低其含水量,使得粘土遇水后不再吸水膨胀,从而保持土壤的稳定性。岩土力学工程中以保持土壤稳定性为目的对粘土的改性称为“钝化”。所谓钝化就是用 钝化剂与粘土矿物表面发生反应,改变粘土矿物的表面结构,提高憎水性,增加粘土整体的力学性质,从而达到稳定土体的目的。在粘土矿物钝化中表面活性剂是一个重要的组成部分 ,但是表面活性剂在固液界面的吸附,除决定于其本身的性质外,还决定于固体的性质、溶 液的pH值和温度等。因此,研究粘土矿物表面结构和性质以及与钝化剂的相互作用是提高粘 土矿物钝化效果的重要途经。利用近代分析方法（XRD、IR、Raman、MAS NMR、TEM、AFM和S EM）,对粘土矿物（高岭石、蒙脱石和伊利石）钝化前后的表面结构和性质进行了系统研究 ,并结合相关的土力学、工程力学参数的测定,阐明粘土矿物钝化的机理,剖析和研制粘土 矿物钝化剂,为解决各类工程和灾害问题中的土壤稳定提供理论依据。     

Sand–Attapulgite Clay Mixtures as a Landfill Liner

Absrtract This paper investigates the potential use of sand–attapulgite (palygorskite) mixtures as a landfill liner. The sand and attapulgite clay used in this study were brought from Wahiba (eastern Oman) and Al-Shuwamiyah (southern Oman), respectively. Initially the basic properties of the sand and clay were determined. Then the attapulgite clay was added to the sand at 5, 10, 20 and 30% by dry weight of the sand. The sand–attapulgite clay mixtures were subjected to mineralogical, chemical, microfabric and geotechnical analyses. The X-ray diffraction (XRD) qualitative analysis showed that attapulgite is the major clay mineral. The chemical compounds, exchangeable cations and cation exchange capacity (CEC) for the␣samples were determined. The CEC for the sand–clay mixtures is low but increases with the increase in clay content. The scanning electron microscope (SEM) examination showed that the addition of clay developed coating between and around the sand grains which results in filling the voids and reducing the hydraulic conductivity of the sand–clay mixtures. The hydraulic conductivity values for the pure clay and sand + 30% clay mixture prepared at 2% above optimum water content are slightly higher than hydraulic conductivity requirements for landfill liners but can be acceptable. The geotechnical study which included grain size distribution, Atterberg limits, specific gravity, compaction, hydraulic conductivity and shear strength tests showed that the sand+30% clay mixture prepared at 2% above optimum water content can be considered to satisfy the requirements for landfill liners. For all sand–clay mixtures no swelling was recorded and the addition of clay to the sand improved the shear strength.     

乙酸和碳酸对粘土土工性状影响的试验

对加入不同浓度乙酸和碳酸的土样做室内土工试验,并进行机理分析。试验结果表明:乙酸根、碳酸根通过改变粘土颗粒双电层的厚度、极性水分子的吸附量,使土的结构发生凝聚或分散,引起压实粘土的塑性、渗透性等变化。其中,乙酸根是通过溶解粘土矿物中的铝,提高了粘土的渗透系数和塑性指数;而碳酸根是以其与金属离子发生化学反应生成难溶性碳酸盐的方式,降低了粘土的渗透系数。这为判断垃圾堆放场粘土衬垫工程的稳定性提供了依据。     

城市河道淤泥特性及改良试验初探

以南京内秦淮河疏浚淤泥为例,通过土工试验、XRD和X射线荧光光谱试验等方法,研究了城市河道淤泥的物理性质、矿物成分、化学成分等特性。试验结果显示:秦淮河淤泥粘粒含量低、有机质含量极高,矿物成分主要有石英和少量粘土矿物等。为了实现淤泥的资源化处理,运用水泥、石灰无机固化材料对淤泥进行固化改良试验及改性土无侧限抗压强度试验,结果表明随着水泥掺量增加,水泥固化土由塑性破坏向脆性破坏过渡,破坏应变在1.8%~2.2%,而石灰固化土均表现为脆性破坏,且破坏应变小于水泥土,为1%左右。水泥固化土28d强度为670kPa,固化效果优于石灰,但略低于处理一般软土的固化土强度。研究结果对处置城市河道淤泥有一定参考价值。     

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.     

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.     

三峡库区泥灰质岩石及其残坡积土化学成分及粘土矿物的定量研究

由于二峡库区三叠系巴东组(T2b)泥灰质岩石特殊的化学矿物组成和所处亚热带湿热环境,决定了三峡库区移民迁建场地工程地质环境的复杂性。通过泥灰质岩石及其不同风化岩和残坡积土的化学成分、粘土矿物成分定量研究和扫描电镜观察,揭示了CaCOs溶蚀和粘土矿物富集过程及粘土矿物的复杂成分,发现了风化过程中伊利石()向伊利石／蒙脱石(I／S)混层粘上矿物的转化,解释了岩土工程性质恶化的原因,从而提高了地质研究和地质灾害研究的水平。     

Rn and CO2 soil–gas geochemical characterization of thermally altered clays at Orciatico (Tuscany,Central Italy)

The physical properties of clay allow argillaceous formations to be considered geological barriers to radionuclide migration in high-level radioactive-waste isolation systems. As laboratory simulations are short term and numerical models always involve assumptions and simplifications of the natural system, natural analogues are extremely attractive surrogates for the study of long-term isolation. The clays of the Orciatico area (Tuscany, Central Italy), which were thermally altered via the intrusion of an alkali-trachyte laccolith, represent an interesting natural model of a heat source which acted on argillaceous materials. The study of this natural analogue was performed through detailed geoelectrical and soil–gas surveys to define both the geometry of the intrusive body and the gas permeability of a clay unit characterized by different degrees of thermal alteration. The results of this study show that gas permeability is increased in the clay sequences subjected to greater heat input from the emplacement of the Orciatico intrusion, despite the lack of apparent mineral and geotechnical variations. These results, which take into consideration long time periods in a natural, large-scale geological system, may have important implications for the long-term safety of underground storage of nuclear waste in clay formations.     

金属离子对粘土土工性状影响的实验

在正交实验设计的基础上,通过大量的室内实验,对粘土吸附性的影响因素加以分析,为金属离子影响下的粘土土工性状研究奠定基础。在粘土吸附性的基础上,对粘土吸附离子后的基本土工特性进行实验研究,得出了粘土土工特性的变化趋势。结果表明:在单离子体系中粘土对离子的吸附量明显大于混合离子体系中对该离子的吸附量;在多离子体系中,则表现为高价离子具有更强的竞争力;粘土的塑性指数基本是随离子含量的增加而增大;粘土强度随着离子总含量的增高而逐渐降低。      

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.     

The impact of cyclic wetting and drying on the swelling behaviour of stabilized expansive soils

Black cotton soil (BCS) deposits, stabilized with waste materials-wood-ash and organic matter (leaves, grass, etc.) exist in BCS areas of North Karnataka, India. These ash-modified soils (AMS) are apparently stabilized by hydrated lime produced by biochemical, dissolution, and hydration reactions. The influence of cyclic wetting and drying on the swelling behaviour of wood-ash-modified BCS and laboratory lime-treated BCS specimens are examined in this study. Such a study is required to assess the long-term behaviour of chemically stabilized soils in geotechnical applications. Cyclic wetting and drying caused the AMS specimens to become more porous and less saturated. Consequently, the cyclically wetted and dried (or desiccated) AMS specimens collapsed significantly at the experimental flooding pressures. The beneficial effects of lime-stabilization of the BCS specimens were also partially lost in cyclically wetting and drying them. The clay contents of the lime-treated BCS specimens increased on cyclic wetting and drying. The increased clay contents in turn, affected their Atterberg limits and swell–shrink potentials. Partial loss of inter-particle cementation, increased porosity, and reduced degree of saturation, also imparted small to moderate collapse potentials to the desiccated lime-treated BCS specimens.     

Geological and engineering characteristics of expansive soils and rocks in northern Oman

The geology and former climate of northern Oman favoured the formation of smectite clay minerals in certain materials which are implicated in ground heave problems. Investigations have shown that the smectite content of these expansive materials was developed in Oligocene, Miocene and Pliocene times. No evidence of a significant content of smectite was found in pre Eocene strata or in Quaternary strata, except for Desert Fill. It is shown that the main types of expansive materials in northern Oman are bentonitic mudstones, marls and silty mudstones, argillaceous dolomitic limestone, altered conglomerates and the desert fill derived from these. These swelling materials exist as impersistent bands within the bedrock Tertiary conglomerates and limestones. A geotechnical testing program was carried out on undisturbed samples from Sultan Qaboos University staff housing areas where building damage had occurred, to evaluate mineralogical composition, cation content and swelling characteristics. The test results characterized these soils/rocks as highly expansive type with Na-smectite as the dominant clay mineral.     

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.     

无定形态游离氧化铁脱水老化对粘性土物理性质的影响

无定形态游离氧化铁以其自身的特性及其脱水老化作用,对粘性土的物理性质、水理性质乃至工程性质产生了一定程度的影响。本文就粘性土的物理性质、水理性质及力学性质在无定形态游离氧化铁脱水过程中的变化进行了初步研究,期望对粘性土的土工测试方法及参数的合理测定有所裨益。     

西南喀斯特地区不同石漠化阶段土壤黏土矿物组成及其含量变异研究

为了探索西南喀斯特地区土壤中黏土矿物组成及其含量的变异规律,以贵州省普定县和荔波县不同石漠化阶段典型土壤的黏土矿物为例,采用x-射线衍射仪图谱分析方法,计算得到黏土矿物组成及其含量,探讨不同石漠化阶段黏土矿物组成变化规律及其含量之间的线性关系。结果表明：不同石漠化阶段黏土矿物的组成是相同的,均为高岭石、蒙脱石和伊利石;在未石漠化、轻度石漠化、中度石漠化阶段,蒙脱石在剖面表层的质量分数分别为27．82％、29．34％、58．32％,高岭石分别为21．39％、31．81％、36．93％,伊利石分别为50．79％、38．85％、4．75％;在西南喀斯特地区,各石漠化阶段伊利石与蒙脱石的含量之间以及伊利石和高岭石的含量之间都呈显著的线性相关,相关系数分别为-0．9703、-0．9456;西南喀斯特地区土壤相似的成土作用和成土环境造成了黏土矿物相同的组成,而黏土矿物含量的差异说明各成土作用的程度或阶段是不同的;粉粒中的黏土矿物主要为石英和白云母,而砂砾中的黏土矿物主要为石英。     

The role of clay fractions of marly soils on their post stabilization failure

This paper focuses attention on the some basic aspects of the role of clay fraction of marly soils including palygorskite and sepiolite upon marl behaviour. The clay fraction of marl is generally dominated by palygorskite and/or sepiolite. It is the performance of these clay soil fractions that are the root cause of many of the problems encountered in the use of such soils as load-bearing materials. This makes it necessary to investigate the role of palygorskite and sepiolite on marly soil's performance. In this paper, some geotechnical and geoenvironmental aspects of marl behaviour is investigated and a new definition and classification of marly soils is presented. This classification focuses attention on the presence of palygorskite or sepiolite as the major fraction of marl, which governs its geoenvironmental and geotechnical behaviour.     

采用不同加固方案处理软土地基的对比研究

采用强夯法，排水固结法和动力排水固结法3种不同方案对某地基进行了加固处理，并且从孔隙水压力消散，动力触探，静力触探及室内土工试验等方面对不同方案的加固处理效果进行对比研究，证实了动力排水固结法是处理饱和软粘土地基的有效方法。