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1.
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
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.
Copper slag is a by-product obtained from production of copper metal. As copper slag contains silica and alumina, it may exhibit pozzolanic property, and hence it may be re-use in ground improvement applications as a partial replacement of cement. Present study evaluates systematically the possible pozzolanic property of copper slag as well as studies the effect of copper slag on engineering properties of cement-treated clay. X-rays diffraction method was employed to assess the possible pozzolanic property of copper slag. Effect of copper slag on engineering properties (i.e. compressive strength and compressibility) of cement-treated clay was studied with samples prepared with constant water content and workability. The test results showed that with sufficient curing time and at constant workability, the compressive strength of cement-treated clay was found to be increased with increasing amount of copper slag at high cement content but the compressive strength remained the same with increasing amount of copper slag at low cement content. Compressibility of cement-treated clay was found to be unchanged with increasing amount of copper slag. It was concluded that copper slag can be used as partial replacement of cement in treating soft marine clay. 相似文献
4.
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
5.
污水浸泡对水泥土强度和电阻率特性影响的试验研究 总被引：4，自引：0，他引：4
为了揭示污水对水泥土的影响规律,并尝试采用电阻率法作为描述强度和污染特征的手段,把粉质黏土和两种水泥（普通硅酸盐水泥、矿渣硅酸盐水泥）制作的水泥土试块分别浸泡在3种液体（自来水、生活污水、造纸厂污水）中模拟环境侵蚀。首先对比分析了污水对土体液塑限的影响,其次研究了龄期、水泥类型、污水类型等对水泥土抗压强度和电阻率的影响,考察了电阻率和抗压强度的关系。结果表明：污染后土样的液限、塑限均增大,塑性指数减小;水泥土抗压强度和电阻率均随龄期增加而增长;污水均降低了水泥土的抗压强度和电阻率,但是矿渣硅酸盐水泥土的抗压强度和电阻率均高于普通硅酸盐水泥土,说明在污水环境中,矿渣水泥对水泥土有一定的抗劣化能力;在不同的龄期、水泥类型、污水类型下,水泥土电阻率均与抗压强度呈现出一致的变化规律,二者线性相关。 相似文献
6.
An experimental study is conducted to measure small-strain shear modulus of clay-cement mixture using bender element apparatus
setup in a triaxial cell. Bender element tests were conducted on cement-treated soils and the results were analyzed to study
the variation of shear modulus properties of soil specimens at different cement contents, confining pressures, curing times,
and compaction moisture contents. Based on the obtained results increasing the cement ratio has a significant effect on the
small-strain shear modulus of the treated soils, and this effect signifies with increasing the moisture content and curing
time. Rates of shear modulus enhancements due to cement content, curing time, and compaction moisture content are quantified
and presented. In this study, a clay–cement–water ratio formulation is proposed that enables one to calculate cement and water
contents required to obtain specific small-strain shear modulus. 相似文献
7.
The mechanical behaviour of three cement-treated dredged materials (DM) was studied in the laboratory by isotropic compression and undrained triaxial tests. The intrinsic properties of the untreated and reconstituted soil were used as a reference framework to interpret the effect of cementation on the mechanical behaviour of the cement-treated DM. The isotropic compression line of the reconstituted soil is termed the intrinsic normal compression line (INCL). It is found that the isotropic compression lines of the cement-treated DM lie above the INCL, i.e. the void ratio of the cement-treated soil is higher than that of the reconstituted soil for a given confining pressure. The yield stress measured from the isotropic compression tests increases with increasing cement content and curing time. The pre-yield and post-yield shear responses of the cement-treated DM are different. Pre-yield soil specimens show a tendency to dilate, but post-yield soil specimens show a tendency to contract. Failure envelopes of the cement treated DM lie above that of the reconstituted DM. Linear Mohr–Coulomb failure envelopes were observed for the range of applied stress used in the study. The cohesion intercept increases with increasing cement content and curing time. The strength enhancement of the cement-treated DM is the result of the structures developed during cementation process. Based on a recently proposed soil water transfer model, the change in normalised bound water content, (Δmbw)N, is used to evaluate the combined effects of cement content and curing period on the mechanical behaviour of the cement-treated DM. It is found that there exists a threshold value of (Δmbw)N, beyond which the yield stress and cohesion intercept increases nonlinearly with increasing (Δmbw)N. The threshold value is equal to 0.37 for the three DM used in the study. 相似文献
8.
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
9.
Consoli Nilo Cesar Párraga Morales Durval Saldanha Rodrigo Beck 《Acta Geotechnica》2021,16(5):1473-1486
The presence of lateritic soils occurs in tropical and subtropical regions. The improvement of lateritic soils that are not suitable for a particular purpose through techniques that combine modification of grain size through the insertion of sand, incorporation of Portland cement and densification through compaction is seen as an alternative. In this context, a dosage method to use a local lateritic soil as construction material in a most rational way reducing the economic and environmental impacts related to this activity is still missing. Therefore, the current research aims to evaluate the performance of a lateritic soil via modification of grain size through the insertion of sand, incorporation of Portland cement and densification through compaction. For this, unconfined compression, and durability (wetting and drying) tests were carried out on specimens of compacted clayey gravel lateritic soil, whose granulometry was modified by the insertion of distinct amounts (from zero to 45%) of weathered sand, treated with distinct Portland cement contents (from 4 to 10%), molded at different dry unit weights (from 16.8 to 20.1 kN/m3) and cured for 7 and 28 days. Results of the mechanical tests have shown the significant influence exerted by cement content and dry unit weight of the blend, followed by curing time and finally sand insertion. Satisfactory correlations between the response variables (qu and ALM) and the adjusted porosity/cement index (η/Cv) were obtained. Furthermore, an innovative approach to replacing the laborious durability test is proposed.
相似文献10.
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
11.
S. M. Haeri A. Hamidi S. M. Hosseini E. Asghari D. G. Toll 《Geotechnical and Geological Engineering》2006,24(2):335-360
The behavior of a cemented gravely sand was studied using triaxial compression tests. Gypsum, Portland cement and lime were
used as the cementing agents in sample preparation. The samples with different cement types were compared in equal cement
contents. Three cement contents of 1.5%, 3.0% and 4.5% were selected for sample preparation. Drained and undrained triaxial
compression tests were conducted in a range of confining pressures from 25 kPa to 500 kPa. Failure modes, shear strength,
stress–strain behavior, volume and pore pressure changes were considered. The gypsum cement induced the highest brittleness
in soil among three cement types while the Portland cement was found to be the most ductile cementing agent. In lower cement
contents and lower confining pressures the soil cemented with Portland cement showed the highest shear strength. However,
in the same range of cement content, the soil cemented with gypsum showed highest shear strength for highest tested confining
stress. For higher cement contents the shear strength of soil cemented with Portland cement is higher than that for the two
other cement types for the range of confining pressures tested in the present study. The samples cemented with lime had the
least peak and ultimate shear strength and the highest pore pressure generation in undrained tests. Contrary to the soil cemented
with lime, the brittleness of soil cemented with gypsum and Portland cement reduces in undrained condition. Finally it was
found that the effect of cement type on the shear strength of cemented soils is more profound in drained condition compared
to undrained state. 相似文献
12.
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
13.
为研究水泥砂浆固化土剪切强度特性和合理确定水泥砂浆固化土工程应用的配比,从掺砂量、水泥掺入比、原料土含水率及砂料粒径入手,对水泥砂浆固化土进行了室内固结不排水三轴（CU）试验研究。结果表明,掺砂可以改善固化土强度;随掺砂量的增加,黏聚力和有效黏聚力先增加后减小,转折点的掺砂量为最佳掺砂量（10%左右）,内摩擦角和有效内摩擦角不断增加,一定掺砂量下增加水泥掺入比可有效地提高固化土的强度;随着含水率的增加,固化土的黏聚力呈近似线性减小的关系,而内摩擦角几乎保持不变,采用水泥砂浆处理高含水率软弱地基时适当提高掺砂量,可以较大幅度改善固化土的力学性质;在掺料配比一定的情况下砂料粒径对固化土的抗剪强度指标存在一定的影响。采用单一粒径砂料的固化土抗剪强度更高,该单一粒径在固化土级配良好的前提下,不均匀系数Cu趋于最大、曲率系数Cc趋于最小 相似文献
14.
矿渣胶凝材料固化软土的力学性状及机制 总被引：4，自引：0，他引：4
利用矿渣胶凝材料固化软土,既可利用工业废渣,又能减少水泥的用量。以矿渣胶凝材料固化黏土、砂土二种软土。发现矿渣胶凝材料加固软土的效果远好于水泥、石灰,其9 %掺量的固化土28 d的无侧限强度达到2.0 MPa以上,普遍高于15 %掺量的水泥固化土,且其28 d固化土的软化系数普遍高于90 %以上,固化黏土后CBR值远高于同掺量的石灰固化土。X衍射结构分析表明,矿渣胶凝材料水化时产生的高强难溶的矿物晶体是其固化软土效果好的主要原因。因此,矿渣胶凝材料是一种性能优异的软土加固材料。 相似文献
15.
Jin Liu Bin Shi Hongtao Jiang He Huang Gonghui Wang Toshitaka Kamai 《Engineering Geology》2011,117(1-2):114-120
The topsoil of clayey slope is easy to erosion because it is weak in its strength, water stability and erosion resistance. A new organic polymer soil stabilizer, which was developed for the stabilization treatment of clay slope topsoil and was named as STW, was introduced in this study. In order to understand the effect of STW on the stabilization of clayey soil, laboratory tests on the unconfined compressive strength, shear strength, water stability and erosion resistance of untreated and treated soil specimens are performed, The results indicated that STW soil stabilizer can significantly increased the unconfined compression strength, shear strength, water stability and erosion resistance of clayey soil. The unconfined compression strength increased with the increasing of curing time and the variation mainly occurs in the first 24-hour. With the addition amounts of STW increasing, the strength, water stability and erosion resistance increased at the curing time being 48 h, but in the case of friction angle, no major change was observed. Based on the scanning electron microscopy (SEM) analysis of the stabilized soil, the stabilization mechanisms of STW soil stabilizer in the clayey soil were discussed. Finally, a field test of the stabilization treatment of clay slope topsoil with STW was carried out, and the results indicated that the STW soil stabilizer on the stabilization treatment of clay slope topsoil is effective for improving the erosion resistance of slope topsoil, reducing the soil loss and protecting the vegetation growth. Therefore, this technique is worth popularizing for the topsoil protection of clay slope. 相似文献
16.
用似水灰比对水泥土无侧限抗压强度的预测 总被引：12，自引：1，他引：11
对以连云港地区的海相软土为原料的水泥土进行了一系列物理、强度试验,分析了含水量、水泥用量和龄期对水泥土强度的影响,提出了似水灰比的概念用于水泥土强度的预测。采用提出的水泥土强度预测公式,根据某一似水灰比、龄期28 d某种的水泥土室内试验强度,可以预测不同含水量、不同水泥用量和不同龄期的水泥土室内试验强度。通过比较分析发现,得出水泥土强度预测公式可以很好地应用于其他研究者已经发表的水泥土试验数据,进一步验证了所提出的强度预测公式的有效性。 相似文献
17.
非饱和红粘土和膨胀土抗剪强度的比较研究 总被引：24，自引：4，他引：20
红粘土是对环境湿热变化敏感的塑性粘土,具有一般膨胀土吸水膨胀失水收缩的特性。与普通粘性土相比,红粘土与膨胀土的强度特性更为复杂。它既是土体抵抗剪切破坏能力的表征,也是计算路堑、渠道、路堤、土坝等斜坡稳定性以及支挡构筑物土压力的重要参数。通过试验研究讨论了红粘土与膨胀土的强度特性以及与一般粘性土的差别及其各种影响因素,并探讨了非饱和红粘土与膨胀土的抗剪强度指标与含水量之间的相关关系。试验结果表明,红粘土与一般膨胀土的吸水膨胀规律完全相同。其试验结果可为红粘土与膨胀土地区工程设计与建设提供参考依据。 相似文献
18.
The liquefaction of clayey soils under cyclic loading 总被引：4，自引：0，他引：4
This paper seeks to investigate the liquefaction of clayey soils, a phenomenon that has been the trigger for many natural disasters in the last few decades, including landslides. Research was conducted on artificial clay-sand mixtures and natural clayey soils collected from the sliding surfaces of earthquake-induced landslides. The undrained response of normally consolidated clayey soils to cyclic loading was studied by means of a ring-shear apparatus. For the artificial clay-sand mixtures, it was found that the presence of a small amount of bentonite (≤ 7%) would cause rapid liquefaction, while a further increase in bentonite content (≥ 11%) produced the opposite effect of raising soil resistance to liquefaction by a significant degree. It was demonstrated that the bentonite-sand mixture was considerably more resistant to liquefaction than the kaolin-, and illite-mixtures, given the same clay content. The test results of plastic soils revealed the significant influence of plasticity on the liquefaction resistance of soil. The microfabric of clayey soil was investigated by means of a scanning electron microscope. The analysis showed that the liquefaction potential of soil was strongly related to certain particle arrangements. For example, soil vulnerable to liquefaction had an open microfabric in which clay aggregations generally gathered at the sand particle contact points, forming low-strength “clay bridges” that were destroyed easily during cyclic loading. On the other hand, the microfabric of soil that was resistant to liquefaction appeared to be more compact, with the clay producing a matrix that prevented sand grains from liquefying. In the case of the natural soils, the obtained results indicated that their cyclic behavior was similarly influenced by factors such as clay content, clay mineralogy and plasticity. The relation between the liquefaction potential of natural soil and its microfabric was thus also established. On the basis of the obtained results, the authors posited an explanation on the mechanism of liquefaction for clayey soil. 相似文献
19.
Cement stabilization of soil is a useful method to improve the mechanical behaviors and engineering performance of soils in geotechnical design and construction projects involving weak or liquefiable soils. Among the factors affecting the strength of cement-stabilized soils, water content and water–cement ratio are important but less well understood because of controversial views. This paper presents a systematic laboratory study to investigate the effects of water content and water–cement ratio on the unconfined compressive strength, with good control of the packing density and void ratio of the tested specimens. The effects of void ratio and cement content are also investigated. The strength of the cement-stabilized sand continuously decreased with increasing water–cement ratio within the range of 0.5 to about 3. A general equation is suggested to evaluate the unconfined compressive strength of cement-stabilized soil. Finally, a new conceptual characterization chart is proposed with consideration of the effects of cement content, water content, and water–cement ratio.
相似文献20.
Effect of Cement and Quarry Dust on Shear Strength and Hydraulic Characteristics of Lithomargic Clay
The lithomargic clay constitutes an important group of residual soils existing under lateritic soils. This soil is found on
the western and eastern coasts of India over large areas. This soil is a problematic one and is very sensitive to water and
loses a greater part of its strength when becomes saturated. These high silt deposits have invited many problems such as slope
failures, foundation failures, embankment failures, uneven settlements etc. In this investigation an attempt is made to study
the effect of cement and quarry dust on shear strength and hydraulic characteristics of the lithomargic clay after the stabilization.
Microfabric and mineralogical studies were carried out to find out the reason for the strength development of the stabilized
soil using SEM and XRD analysis. The results indicated that there is an improvement in the properties of the lithomargic clay
with the addition of cement and quarry dust. The XRD results indicated the formation of CSH and CAH, which are responsible
for strength development in the stabilized soil. 相似文献