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1.
In nature, soils are often composed of varying amounts of clay, silt and sand. Variation of the percentage of these compositions can affect the final strength of the soils when stabilised with cement. In this study, focus was placed on clayey soils with different gradation of sand impurities up to 40% in mass. An extensive study of such clayey soils treated with cement was investigated. For the results, it is noted that water:cement ratio was a major influence of strength development of cement-treated clayey soils. In contrast, the soil:cement ratio was found to have minor effects on the strength development. The presence of sand impurities has a significant reduction on the strength development of the cement-treated clayey soil mixture due to more free water available for hydration. The use of free-water:cement ratio is adopted which was shown to be capable of adjusting for such change in amount of free water and water holding capacity of the clay which is determined with Atterberg’s liquid limit tests. The effects of gradation (fine, coarse and well-graded) of the sand impurities were found to affect strength development minimally, owing to similarities in their liquid limits when mixed with clay. Ordinary Portland cement (OPC)-treated clayey soils produced a more rapid gain in strength but lower final strength at 28 days of curing as compared with Portland blast furnace cement (PBFC). This is found to be persistent for different gradation of sand impurities. A linear correlation can be established based on the log of the unconfined compressive strengths developed at different curing age, with slopes of these linear trends found to be similar for PBFC and OPC-treated clayey soil specimens. Finally, a strength prediction model comprising of these findings is developed. The parameters adopted in this model coincide with values proposed by past studies, thereby validating the robustness of the model. The practical benefits from this study offer a quality control scheme to forecast long-term performance of cement-treated clayey soils as well as optimise cement dosage in cement stabilisation to produce a more cost-effective and less environmental-invasive usage of the technology in geotechnical applications.
相似文献2.
Clay soils, especially clay soils of high or very high swelling potential often present difficulties in construction operations. However, the engineering properties of these clay soils can be enhanced by the addition of cement, thereby producing an improved construction material. Higher strength loss of cement stabilized clay soils after soaking in water is attributed to water absorbing capacity of the clay fraction (e.g. montmorillonite). Kaolinite and illitic soils are largely inert and resist to water penetration. These clays generally develop satisfactory strengths resulting to low strength reduction [Croft, 1967]. The swelling clays such as bentonite soaked in water, due to environmental conditions, result to volume increase causing macro and micro-fracturing in engineering structures. These fractures accelerate water penetration and consequently cause greater strength loss [Sällfors and Öberg-Högsta, 2002]. The water intrusion during soaking creates swelling and disrupts the cement bonds. The development of internal and external force systems in soil mass, due to soaking conditions, establish the initiation of slaking. Internal force system of a stabilized clayey soil consists of the resultant stresses established by the bonding potential of a cementing agent and the swelling potential of a clay fraction. In an effort to study this influence of soaking conditions and final absorbed water content on the stabilization parameters (cement, compaction, curing time), both unconfined compressive strength and slaking (durability) tests were carried out on two different cement stabilized clayey mixtures consisted of active bentonite, kaolin and sand. 相似文献
3.
对于使用水泥与上海黏性土进行混合加固的土体,其强度增长特性与水泥含量、加固土的初期pH值、养护时间有关。以上海4类黏土为研究对象,对加固土的强度增长特性进行了试验研究;探讨了加固土的养护时间、水泥含量、初期pH等与加固土强度的关系。试验结果表明,当上海黏土中水泥含量或者加固土的初期pH值大于某一临界值时,水泥加固土的强度将迅速增加,对于上海黏土,该临界pH值为11.7,对应的水泥含量为17%～20%。但当水泥含量达到一定值后,它对土体的pH值的影响开始变小,而且水泥土的强度趋于稳定的时间变长。 相似文献
4.
利用在滨海新区施工的2眼全取芯钻孔（G2和G3）,通过原状土样工程特性指标测试、固结压力试验、0-P0反复加、卸荷试验及地面沉降分层标监测数据分析等,系统阐述了滨海地区深部黏性土层弹塑性变形特征与地面沉降的关系。结果表明：天津滨海地区100 m以浅主要为欠固结土层;100～400 m土层处于超固结和微超固结状态,主要是由过去地下水超量开采造成的;400 m以下土层以正常固结为主。G2和G3孔不同层位黏性土层在反复加、卸荷试验过程中表现出塑性变形量逐渐减小,而弹性变形量几乎不变,与反复加、卸荷次数无关,表明黏性土层在水位反复升降条件下,逐渐变为以弹性变形为主。黏性土层这种特性显示,在地下水位反复升降多次后,黏性土层将会逐渐变成弹性体,在水位恢复时,将产生同步回弹,对防治地面沉降具有重要意义。分析弹塑性变形与黏性土层深度、天然含水率和黏粒含量的相关性发现：弹性变形量与黏性土层深度、天然含水率及黏粒含量呈正相关性;塑性变形量与深度相关性不明显,与天然含水率和黏粒含量呈负相关性。 相似文献
5.
Abdelaziz El-Shinawi 《Journal of the Geological Society of India》2017,89(3):339-343
This study compare liquid limit values obtained by the Casagrande apparatus, Russian and British drop cone penetrometer. Liquid limit determined for clay samples collected from 10 boreholes at the Cairo-Suez district (north western part of Badr City), Egypt. It is the most important geotechnical parameter used of fine-grained soils. The liquid limits for 40 natural clay samples varying between 27.8 and 69.7%. It is found that the liquid limit determined by the Casagrande apparatus and Russian standard (cone penetrometer) give essentially the same results with a difference of < 5%. It is observed that the values of Casagrande apparatus were generally lower than those obtained by the cone penetrometer with Russian standard. In addition, Casagrande apparatus for some samples, which had liquid limits of more than 60%, give a higher result. The liquid limits determined by the Russian and British standards are not consistent with a difference of < 1%. Besides, the results which determined by the Casagrande apparatus and British standards (BS), provide equivalent values with a difference of < 3%. 相似文献
6.
Binod Singhi Aminul Islam Laskar Mokaddes Ali Ahmed 《Geotechnical and Geological Engineering》2017,35(5):1907-1920
Clayey subgrade soil requires treatment in order to make the subgrade stable for pavement structures. Treatment of clayey soil i.e. stabilization of clayey soil by cement, lime, and fly ash are established techniques used in geotechnical and highway engineering. Stabilization by alkali activation of fly ash is reported recently but literatures are limited. Present study investigates the stress strain behavior, peak stress and ultimate strain of clayey soil stabilized by slag and slag-fly ash blending by alkali activation. The peak stress as high as 25.0 N/mm2 may be obtained at 50% slags content when 12 molar sodium hydroxide solutions were used. Peak stress, ultimate strain and slope of stress–strain curve of stabilized clay are controlled by Na/Al and Si/Al ratios. Stress–strain response and peak stress of slag and fly ash blended specimen are not governed by Na/Al and Si/Al ratios; rather the behavior is dependent predominantly on slag content. 相似文献
7.
Behzad Fatahi Thu Minh Le Behnam Fatahi Hadi Khabbaz 《Geotechnical and Geological Engineering》2013,31(5):1421-1435
In this study, effects of two types of geofibers, namely polypropylene and recycled carpet, on three dimensional shrinkage properties of cement treated kaolinite and bentonite clays are investigated. Cement treated clay specimens were prepared with cement contents of 5, 10, and 15 % by weight of dry soil for kaolinite samples, and 30, 40 and 50 % for bentonite samples. To investigate and understand the influence of different fiber types and contents, three different percentages of fiber content (i.e. 0.1, 0.2 and 0.5 % polypropylene fibers; and 0.5, 0.75 and 1 % carpet fibers) were adopted. The results of shrinkage tests on 126 cylindrical samples of cement treated clay with various cement and fiber contents were analysed to understand the relationships between these parameters and the shrinkage percentage of treated soil. Results of this study indicate that combination of cement and fiber is effective in reducing the volume change of clayey soils undergoing drying process. In the applied ranges of cement and fiber contents, the influence of cement addition on the shrinkage reduction is more significant than the addition of fibers for the treated kaolinite. However, addition of fibers in curtailing the shrinkage of bentonite clay is more significant than the cement addition. 相似文献
8.
Mousa F. Attom 《Environmental Geology》2008,55(4):781-788
Iron filling and iron filling–cement mixture were used to improve the shear strength characteristics of Irbid clayey soil.
For this purpose, five types of Irbid clay soils were obtained and mixed with iron filling and iron filling–cement mixture
at different percentages. Two sets of prepared samples were mixed with the admixture. The first set was prepared by mixing
the soil samples with iron filling alone at 2.5, 5.0, 7.5, and 10% by dry weight of the soil. The second set was prepared
by mixing with iron filling–cement mixture at equal ratio of the same percentages of the first set. An unconfined compression
test was performed in this study to measure the shear strength properties of the soils. The test results showed that the increase
in the percentages of the iron filling and iron filling–cement mixture up to 10% will result in increasing the maximum dry
density of the soil and increase the unconfined compressive strength and the secant of modulus of elasticity of the clayey
soil. Also, the addition of iron filling–cement mixture increased the unconfined compressive strength and secant modulus of
elasticity of the clayey soil higher than the addition of iron filling alone. 相似文献
9.
The combined effect of clay and moisture content on the behavior of remolded unsaturated soils 总被引：2，自引：0，他引：2
Naser A. Al-Shayea 《Engineering Geology》2001,62(4):319-342
The behavior of unsaturated clayey soil is highly influenced by the coupled interaction between water and clay content. Various aspects of the behavior of artificial clay–sand mixtures with variable water content were experimentally studied. Laboratory tests were utilized for the determination of consistency limits, the stress–strain relationship, strength parameters, hydraulic conductivity, and volume change characteristics for various combinations of water and clay content in soil mixtures.
Results presented for various clay–sand mixtures include: new normalized consistency limits; the combined effect of clay content and water content on the stress–strain relationship and on the strength parameters (c and φ); and the effect of clay content on hydraulic conductivity and swelling potential. The cohesion of clayey sand is found to increase with increasing water content to a certain limit, above which it decreases. The angle of internal friction for clayey sand is found generally to decrease with increasing water content. The degree of saturation is found to be better than the water content in explaining the strength behavior. The hydraulic conductivity sharply decreases with increasing clay content up to 40% beyond which the reduction becomes less significant. Simple empirical equations are proposed for predicting the swelling potential of clayey soils as a function of either the clay content or plasticity index. 相似文献
10.
In this study, an alternate approach to establish the e-log p relationships for clayey soils within a vertical pressure range of 10–1,000 kPa is discussed. Skempton’s compression index
equation correlating the liquid limit, w
L, and the compression index, C
c, and the reported equation correlating the void ratio at liquid limit, e
L, and the void ratio at a vertical pressure of 100 kPa, e
100, by Burland (1990), were used to establish the e-log p relationships for several reconstituted normally consolidated clayey soils. Consolidation test results of 13 clayey soils
covering a sufficiently wide range of liquid limit were selected from the literature. Also, consolidation tests were carried
out on two highly expansive soils in this study. A comparison of the experimental consolidation test results with the calculated
e-log p relationships in the current study indicated that in general, the agreements between the calculated relationships and the
experimental results are good. The agreements were found to be slightly better for soils with liquid limits less than about
70%. A comparison of the calculated e-log p relationships in the current study with that determined following methods suggested by Nagaraj and Srinivasa Murthy (1983) and Burland (1990) showed that all the three methods yielded very similar results for soils with liquid limit less than 70%. For soils with
liquid limits greater than 70%, the difference between the e-log p relationships calculated in this study and that following Burland (1990)’s method was insignificant, whereas Nagaraj and Srinivasa Murthy (1983)’s method slightly over-predicted the void ratios at larger vertical stresses. 相似文献
11.
Hafiz Muhammad Awais Rashid J. A. D. K. Wanigarathna L. C. Kurukulasuriya N. H. Priyankara A. M. N. Alagiyawanna Takeshi Saito Ken Kawamoto 《Environmental Earth Sciences》2017,76(11):396
This study aimed to develop a low-cost and effective clay liner material for solid waste landfills in Sri Lanka. A locally available clayey soil and its admixtures with 5 and 10% bentonite were examined for this purpose. Laboratory experiments to determine soil plasticity and swell index were carried out on the tested samples. Hydraulic conductivity (k) tests were carried out in the laboratory using water and an aqueous solution of CaCl2 on unconsolidated samples prepared by either dry or slurry packing and pre-consolidated samples with five different consolidation pressures (p) from 10 to 200 kPa. Measured liquid limits for tested admixtures increased with increasing bentonite contents and correlated well with measured values of the swell index. The difference in permeant solutions had little effect on measured k values for both unconsolidated and pre-consolidated samples. The hydraulic conductivities were highly affected by changing p, i.e., the k values decreased on two orders of magnitude as p increased from 10 to 200 kPa. The Kozeny–Carman equation, a theoretical permeability model that expresses the k-porosity relationship, was applied to measured data including reported values. Results showed the Kozeny–Carman equation captured well the porosity-dependent k values for tested soils and their admixtures with bentonite under a wide range of void ratios, suggesting that the Kozeny–Carman equation is a useful tool to estimate the magnitude of k values for differently compacted soil and its bentonite admixtures. 相似文献
12.
13.
Evangelos I. Stavridakis 《Geotechnical and Geological Engineering》2006,24(2):379-398
Major geotechnical problems in construction involving silty–clayey soils are due to their low strength, durability and high
compressibility of soft soils, and the swell–shrink nature of the overconsolidated swelling soils. Confronted with these problems,
a suitable ground improvement technique is needed, for deep excavations in soft clays, for stability, durability and deformation
control. Cement-stabilization is one of the alternatives. An increase in strength and durability, reduction in deformability
are the main aims of this method. Conventional cement-stabilization methods are used mainly for surface treatment. However,
the use of cement has recently been extended to a greater depth in which cement columns were installed to act as a type of
soil reinforcement (deep cement–soil mixing and cement jet grouting). In situ engineering properties of these silty–clayey soils are often variable and difficult to predict. For this reason cement-stabilization
methods have a basic target to control the aforementioned engineering properties of these clays so that the properties of
a silty–clayey soil become more like the properties of a soft rock such as clayey shale or lightly cemented sandstone. So
cement-stabilization of these soils is essential to control their engineering properties and to predict their engineering
behaviour for construction. In an effort to predict, classify and study the suitability of silty–clayey soils for cement-stabilization
both slaking and unconfined compressive strength tests were carried out on clayey–sand mixtures consisted of two types of
clays, kaolin and bentonite. Finally diagrams were prepared to study the variation of slaking and strength due to compaction,
curing time and cement percentage and also to predict areas of efficient cement-stabilization. 相似文献
14.
Adnan Aqeel 《Arabian Journal of Geosciences》2016,9(4):314
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. 相似文献
15.
Shahid Azam 《Geotechnical and Geological Engineering》2007,25(3):369-381
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. 相似文献
16.
黏土岩作为高放废物地质处置库的备选介质,目前得到世界各国的高度重视。黏土岩地质处置库巷道施工过程中,一方面,围岩因开挖损伤生成裂隙使得渗透性增强,对核素的阻滞作用降低;另一方面,在应力和水的耦合作用下,黏土岩良好的裂隙渗透损伤自修复能力使得围岩的渗透性逐渐恢复接近于原始状态。基于电阻率测试,首先开展了黏土岩试样在不同条件下的饱和过程试验研究,得到了黏土岩试样饱和过程中等效电阻率的变化规律,分析了不同损伤程度试样、盐溶液对等效电阻率的影响,进而揭示黏土岩饱和过程中水分运移规律。试验结果表明：（1）等效电阻率随着含水率增加而逐渐减小,并逐渐趋于一个稳定值;（2）等效电阻率的大小不仅与含水率有关,试样内部裂隙的存在也会影响等效电阻率分布,这一发现为电阻率法可以探测试样中裂隙的存在提供了依据;（3）水流在黏土岩中扩散,内部裂隙成为优先通道,水流在裂隙中的快速扩散加快了黏土岩的饱和速度。同时,随着黏土岩中水分与黏土矿物的水化膨胀反应,内部裂隙有一定程度闭合,加深对裂隙闭合机制认识,通过电阻率测试可以有效地揭示这一过程。 相似文献
17.
G.F. Ngon Ngon R. Yongue&#x;Fouateu D.L. Bitom P. Bilong 《Journal of African Earth Sciences》2009,55(1-2):69
A geological survey carried out in the Yaoundé (Cameroon) region has revealed the presence of homogeneous clayey laterite in the upper part of a laterite cover on interfluves, thickest on hills (780–800 m altitude) where ferricrete is absent, and clayey heterogeneous hydromorphic material in valleys. We present in this paper the physical, mineralogical and geochemical properties of these occurrences and discuss their potential as raw material for pottery, manufacture of bricks and tiles. These clayey raw materials are mostly made up of fine particles (ranging from 55 to 60% clay + silt in the clayey laterite, more than 70% clay + silt in the clayey hydromorphic material). Their chemical composition is characterized by silica (<60% SiO2), alumina (<35% Al2O3) and iron (ranging from 3 to 14% Fe2O3). Their main clay minerals are disorganized and poorly crystallized kaolinites. The average limits of liquidity (44.56% versus 91.58%) and limits of plasticity (22.4 versus 45.93) revealed that clayey hydromorphic material has the greatest plasticity. The studied raw materials are suitable for making pottery as well as the manufacture of bricks and tiles. However, the high iron content in the clayey laterite (between 11 and 12% Fe2O3) prevents their efficient use in the manufacture of ceramics. 相似文献
18.
针对低、中、高3种干密度的低液限和高液限压实黏土,开展经历干湿循环过程的渗透系数和孔隙结构变化特征对比研究。结果表明：经3次干湿循环后,相同液限条件下,高压实黏土渗透系数增加比例高于低压实黏土;相同干密度条件下,高液限黏土渗透系数增加比例高于低液限黏土。干湿循环过程中,压实黏土孔隙结构损伤对渗透系数影响随着压实度和液限的提高而加大,而裂隙的发育对渗透系数影响随着压实度的增加和液限的降低而降低。干湿循环过程中低液限压实黏土试样只收缩不开裂,而高液限黏土裂隙发育明显,小尺寸渗透试样无法完全反映裂隙发育对渗透系数的影响,其渗透系数的变化更多是孔隙结构的变化所致,建议通过现场渗透试验或室内大尺寸渗透试验对干湿循环作用下不同液限黏土渗透系数的差异作进一步研究。 相似文献
19.
The presence of heavy metals at high concentrations (percent levels) in soils has been a growing concern to human health and the environment, and the cement stabilization is considered to be an effective and practical approach to remediate such soils. The compressibility of such stabilized soils is an important consideration for redevelopment of the remediated sites for building and/or roadway construction. This paper investigates the effects of high levels of zinc concentration on the compressibility of natural clay stabilized by cement additive. Several series of laboratory compression (oedometer) tests were conducted on the soil specimens prepared with the zinc concentrations of 0, 0.1, 0.2, 0.5, 1, and 2 %, cement contents of 12 and 15 %, and curing time of 28 days. The results show that the yield stress and compression index at the post-yield state decrease with an increase in the zinc concentration regardless of the cement content. The observed results are attributed to the decrease in the cement hydration of the soil. Overall, this study demonstrates that the cementation structure of the soils is weakened, and the compressibility increases with the elevated zinc concentration, particularly at relatively high levels of zinc concentration. 相似文献
20.
高放废物地质处置岩体材料选取中,黏土岩因具有低渗透性、损伤自修复特性、对放射性核素具有良好的吸附作用等优点,被认为是一种合理的高放废物地质处置屏障。以黏土岩为研究对象,从黏土岩短期、长期力学特性等方面开展研究工作,主要内容如下：（1）进行黏土岩短期自然固结试验,确定了黏土岩的基本物理力学参数,主要包括前期固结压力、压缩指数等;（2）进行流-固耦合固结试验,试验结果表明盐水作用对黏土岩力学特性具有重要影响,且流-固耦合过程中的膨胀现象与黏土岩的黏土矿物含量和类型密切相关;（3）通过对黏土岩进行固结流变试验,研究黏土岩渗流-应力耦合作用下的长期力学特性,试验表明黏土岩具有明显的流变特性,且流变现象与载荷密切相关;（4）根据固结流变试验建立黏土岩一维流变本构模型,同时将模型计算结果与试验结果进行对比,分析表明,该模型能够很好地反映黏土岩一维固结流变特性。该研究对我国未来黏土岩高放废物处置库的规划、设计、选址和运营等具有重要的参考意义。 相似文献