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1.
Sulfate induced heave has been attributed to ettringite, which can form when there is an elevated pH as well as sufficient amounts of aluminum, sulfate, calcium and water present. The primary objective of this project was to study the origin and formation of sulfate in Ohio soils in order to assist with selecting appropriate soil stabilization strategies for future roadway construction. Three roadway construction project areas were evaluated: State Route 2 in Lake (LAK) County, US Highway 24 in Paulding and Defiance Counties and Interstate-71 in Morrow (MRW) County. Defiance County had the most soil samples with sulfate concentrations above acceptable risk level (3000 mg/kg SO4). Morrow County had the next highest number of unacceptable sulfate levels. Of the 42 Lake County soils analyzed, 11 contained sulfate above acceptable risk level. The soils surrounding the road construction activities along State Route 2 and US-24 had similar geological characteristics. A potential source of sulfate in Paulding and Defiance Counties was attributed to the direct deposition of gypsum as a soil amendment for farmlands. The most likely sources of soil sulfate in Morrow County were deposition of gypsum for farmland activities and the oxidative weathering of pyrite. 相似文献
2.
The role of clay minerals in marly soils on its stability 总被引：6，自引：0，他引：6
In many sub-tropical and tropical regions of the world, lime or cement stabilization of marly soils is used as a convenient and expedient means for the development of foundation base courses and inexpensive wearing courses for transport purposes. The failure of many of these natural and stabilized marly soils to perform their functions have been reported. Mechanical factors generally used to explain the causes for the foundation failures have not been satisfactorily accepted. This study uses thermodynamic modelling and X-ray diffraction analysis to explain the general basic causes for deterioration of the support capability of these types of soils. The presence of palygorskite in marly soils provides it with some very unique features in its natural state, and particularly when it is stabilized with lime or cement. Formation of an expansive mineral, ettringite, as a transformation product of palygorskite increases the swelling potential of the stabilized soils. The various interactions, reactions and factors contributing to the stability and instability of marly soils, and lime stabilized marly soils are discussed. 相似文献
3.
Ahmed S. Mohammed Cumaraswamy Vipulanandan 《Geotechnical and Geological Engineering》2014,32(1):71-83
In this study, the compressive and tensile behavior of polymer treated sulfate contaminated CL soil was investigated. Based on the information in the literature, a field soil was contaminated with up to 4 % (40,000 ppm) of calcium sulfate in this study. In addition to characterizing the behavior of sulfate contaminated CL soil, the effect of treating the soil with a polymer solution was investigated and the performance was compared to 6 % lime treated soil. In treating the soil, acrylamide polymer solution (15 g of polymer dissolved in 85 g of water) content was varied up to 15 % (by dry soil weight). Addition of 4 % calcium sulfate to the soil decreased the compressive and tensile strengths of the compacted soils by 22 and 33 % respectively with the formation of calcium silicate sulfate [ternesite Ca5(SiO4)2SO4)], magnesium silicate sulfate (Mg5(SiO4)2SO4) and calcium-magnesium silicate (merwinite Ca3Mg(SiO4)2). With the polymer treatment the strength properties of sulfate contaminated CL soil was substantially improved. Polymer treated sulfate soils had higher compressive and tensile strengths and enhanced compressive stress–strain relationships compared to the lime treated soils. Also polymer treated soils gained strength more rapidly than lime treated soil. With 10 % of polymer solution treatment, the maximum unconfined compressive and splitting tensile strengths for 4 % of calcium sulfate soil were 625 kPa (91 psi) and 131 kPa (19 psi) respectively in 1 day of curing. Similar improvement in the compressive modulus was observed with polymer treated sulfate contaminated CL soil. The variation of the compacted compressive strength and tensile strength with calcium sulfate concentrations for the treated soils were quantified and the parameters were related to calcium sulfate content in the soil and polymer content. Compressive stress–strain relationships of the sulfate soil, with and without lime and polymer treatment, have been quantified using two nonlinear constitutive models. The constitutive model parameters were sensitive to the calcium sulfate content and the type of treatment. 相似文献
4.
Physical and engineering properties of soil are improved with various binders and binder combinations. Fly ash and lime are commonly used to improve the properties of expansive soils. An attempt has been made, in this paper, to examine the role of gypsum on the physical and strength behaviour of fly ash-lime stabilized soil. The change in strength behaviour is studied at different curing periods up to 90 days, and the mechanism is elucidated through pH, mineralogical, microstructural and chemical composition study. The strength of soil-fly ash mixture has improved marginally with the addition of lime up to 4 % lime and with curing period for 28 day. Significant increase in strength has been observed with 6 % lime and enhanced significantly after curing for 90 days. The variations in the strength of soil with curing period is due to cation exchange and flocculation initially, and binding of particles with cementitious compounds formed after curing. With addition of 1 % gypsum to soil-fly ash-lime, the strength gain is accelerated as seen at 14 day curing. The accelerated strength early is due to formation of compacted structure with growth of ettringite needles within voids. However, strength at curing for 28 day has been declined due to annoyance of clay matrix with the increase in size of ettringite needle; and again increased after curing for 90 days. The rearrangement of clay matrix and suppression of sulphate effects with formation of cementitious compounds are observed and found to be the main responsible factors for strength recovered. 相似文献
5.
Hydro-mechanical evaluation of stabilized mine tailings 总被引：3，自引：0，他引：3
6.
7.
Xu Zhaoyi 《吉林大学学报(地球科学版)》1989,(2)
在有渗流坝体中,支持毛细水在垂向与横向上都传递静水压力;它与饱水带构成统一的渗流场,一起进行着横向渗流。因此,对坝体应力分布的研究要同时考虑孔隙水压力和渗流驱动力的作用。如将坝体两坡的静水压力(面力)转做渗流驱动力(体力)时,则其分布范围不仅包括浸润曲面以下的饱水带,而且也包括支持毛细水带;在任一点的作用方向与流向相同。横向渗流速度在垂向上呈不等值分布,存在高速带,故渗流驱动力的大小也不是均布的。 相似文献
8.
固化铅污染土的干湿循环耐久性试验研究 总被引：2，自引：0，他引：2
在商用高岭土、膨润土与商业黄砂混合物中加入硝酸铅溶液,添加水泥和石灰两种固化剂,采用室内压实制样方法获得固化的铅污染土试样。进行干、湿循环试验,测试固化体的质量损失和无侧限抗压强度等参数随干、湿循环次数的变化规律,评价固化铅污染土的干、湿耐久性。测试结果表明,本试验8种配比的试样都满足干、湿循环的要求;黏土矿物为膨润土的试样干、湿循环耐久性比黏土矿物为高岭土的试样要差;水泥固化土的干、湿循环耐久性要略优于石灰固化土;加入 8 000 mg/kg的铅可略增大土体的抗干、湿循环耐久性。水泥和石灰固化/稳定化重金属污染土时,土体中含水率是保证加固效果的关键参数之一。土体中含水率应能满足固化剂充分水化、水解、火山灰和碳酸化反应之需要。 相似文献
9.
Chemical stabilisation of expansive soils has been quite efficacious in reducing swelling characteristics, namely, swell potential (S%) and swelling pressure (ps). When chemicals such as lime and cement are added to an expansive clay, flocculation and cementation take place. Flocculation, which is an immediate reaction, is instrumental in reducing plasticity and swell potential significantly. It also reduces the time required for equilibrium heave. This paper presents experimental data on lime-blended and cement-blended expansive clay specimens. Free swell index (FSI), heave, rate of heave and swelling pressure were studied. FSI, heave and rate of heave decreased with increasing lime content and cement content in the blends. But, during a 3-day inundation (a period, generally allowed for the sample to attain to equilibrium heave), cementitious products developed and resisted the applied compressive loads stiffly, resulting in high swelling pressures in the case of lime-blended specimens. Swelling pressure could not be determined in the case of cement-blended specimens. Hence, short inundation tests (inundating the specimens only for 15 minutes) were performed. But, even from these tests, swelling pressure could not be determined for cement-blended specimens. This indicated the development of strong cementitious products in them. It was interesting to find that, in both long and short duration, the lime- and cement-blended specimens attained to equilibrium heave in the same time period. FSI decreased from 185% to 63.63% when lime content was increased from 0% to 4%, and from 185% to 110% when cement content was increased from 0% to 20%. Swell potential reduced by 42.5% at 4% lime and by 46.4% at 20% cement. Swelling pressure increased from 210 kPa to 320 kPa when lime content was increased from 0% to 4%. Linear shrinkage of the specimens also decreased with increasing additive content. 相似文献
10.
天津滨海软土力学性质较差,不能直接满足工程需要,在软土中加入固化剂能有效提高软土的工程力学性能,但若在固化剂中再添加适量外加剂,又能再次提高固化土的强度。本文以石灰作为主剂,水泥、石膏作为辅剂改良天津滨海软土,以无侧限抗压强度作为固化效果判断标准,同时进行相应的微观结构测试,并对破坏后的试样进行抗压试验。试验结果表明:水泥的最佳掺量仅随石灰掺量不同而变化,如12%的石灰固化土中,水泥掺量不超过3%可以最好地提高石灰固化土强度; 石膏则不能改善土体强度,并且会使土体水稳定性差,遇水开裂。纯石灰固化土及掺外加剂的石灰固化土都是低压缩性土,各种力学性质都得到明显提高,其破坏形式为脆性破坏,破坏后强度很低且不能恢复,在实践中值得重视。微观结构分析表明:固化土中有CSH网状胶凝(水化硅酸钙)、针状钙矾石、无定形文石(CaCO3)、Ca(OH)2晶体等能够填充孔隙、胶结颗粒的物质生成,有效、适量的生成物有利于固化土强度的提高。土体中总孔隙个数及总颗粒个数都随荷载的增加而增多,孔隙面积、孔隙等效直径及颗粒等效直径都随荷载的增加而减少。 相似文献
11.
石灰稳定土工程翻修改造后会产生大量的石灰土弃渣,为避免污染环境和节约工程投资,需重新利用破碎的石灰土进行填筑。但石灰土破碎后强度急剧降低,需要添加胶凝材料提升其力学性能。以重塑石灰土为研究对象,通过添加5%石灰或水泥进行再改良,对比分析两种再改良土的强度和压缩性等力学指标,结果表明,石灰再改良土的力学特性优于水泥再改良土。借助粒度分析、电镜扫描、X衍射和热重分析试验手段揭示了石灰再改良土性能优越的内在机制,发现石灰再改良土中的石灰和石灰土团粒能形成很好的胶结;但水泥未能和石灰土团粒形成有效胶结,自身形成了边-面和边-边接触的片状多孔架构。重塑石灰土残存的氢氧化钙是引起水泥再改良土性能劣于石灰再改良土的主要诱因。 相似文献
12.
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
13.
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
14.
Omar Saeed Baghabra Al-Amoudi 《Engineering Geology》1994,36(3-4):279-291
Vast expanses of arid, saline soils that occur along the Arabian Gulf seaboard and elsewhere possess a very low density and strength that necessitate improvement before any actual construction takesplace. For large-scale constructions, several field improvement techniques have recently been implemented with various degrees of success. In surficial, small-scale applications, chemical stabilization provides a potential technique to improve the inferior properties of these soils, known locally as sabkha. A literature search indicates that chemical stabilization of soils usingasphalt, lime and cement is usually conducted at lower moisture contents than the optimum. Such moisture contents are also much lower than the natural moisture content of sabkha, and if applied to sabkha in the field, this wouldrequire lowering the moisture content before any stabilization commenced; whichwould be neither feasible nor economical.
In this investigation, an eastern Saudi sabkha soil was chemically stabilized at its natural moisture level, which varies from 16% to 22%. In addition to the characterization of the soil and standard compaction tests, cement and lime sabkha mixtures were prepared at five additions and cured for up to 90 days in plastic wrap. Results indicate that cement-stabilized sabkha gained high strength with time and proved to have a potential use in construction. 相似文献
15.
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
16.
《矿物学报》2013,(Z1)
In this paper, a high calcium high sulfate ash as the main material, adding fly ash, lime, cement, gypsum and some modifiers to prepare autoclaved aerated concrete. The products complies with the technical requirements of GB/T11968-2006. This paper also studies the influence of the physical methods and water ratio on autoclaved aerated concrete by high calcium high sulfate ash aerated concrete. The best ratio of water and Grinding time were found in practice study. 相似文献
17.
为研究CaO的赋存形态及含量对钙矾石固化/稳定化重金属铅污染土效果的影响,采用高铝水泥提供AlO2-,纯石膏或磷石膏提供SO42-,高铝水泥、石膏、普通硅酸盐水泥或生石灰提供CaO,制备不同组分固化剂配比的固化土,测试试样强度和孔隙溶液pH值等宏观物理力学指标,通过醋酸缓冲溶液法测试试样的铅溶出量,对比分析不同固化剂固化土的矿物成分与微观结构特征。结果表明,钙矾石固化/稳定化重金属铅污染土效果显著;钙矾石对孔隙的填充作用带来的增强效果不能代替水化硅酸钙胶结土颗粒的胶结作用,普通硅酸盐水泥对试样的强度更有利,但其后期强度增幅不大,而生石灰有利于固化土强度的持续增长;生石灰较普通硅酸盐水泥对钙矾石的形成、稳定和重金属Pb2+的固化/稳定化更有利;磷石膏和纯石膏对试样的pH值、无侧限抗压强度及钙矾石固化/稳定化重金属Pb2+的效果影响较小;固化土体微观结构特征表明,CaO含量对钙矾石生成形态及作用效果影响显著。当CaO含量较低时,早期生成的钙矾石将向单硫型硫铝酸钙转化。研究成果可丰富重金属污染场地原位处理技术,具有重要的理论意义和工程应用价值。 相似文献
18.
Alain Le Kouby Antoine Guimond-Barrett Philippe Reiffsteck Anne Pantet 《Geotechnical and Geological Engineering》2018,36(3):1463-1474
Nowadays, improving the strength and deformation properties of soft soils by deep soil mixing is a commonly used technique. There is also an increasing interest in the use of this technique for foundation/structural elements and excavation retaining walls applications. The compressive strength and elastic modulus of the soil mix material are key parameters in the design of these structures. However, there is very limited information available on the impact of exposure to air drying (in the case of retaining wall) on the strength and stiffness of cement stabilized soils. The aim of this study is to investigate the effects of different curing conditions (immersion in water, cycles of wetting and drying, continuous air drying) on the mechanical properties of soils treated with cement in the laboratory. Free–free resonance tests and unconfined compression tests were performed on specimens of silt and sand treated with blastfurnace slag cement. Strength increases more rapidly than stiffness between 7 and 30 days. The strength of stabilized soils submitted to cyclic wetting and drying before the cement hydration process is complete continues to increase. As long as the periods of drying do not induce microcracks, the stiffness of the treated soil specimens also increases with time. However, the stiffness is lower than for the specimens cured in water indicating a disruptive effect of the imposed wetting–drying cycles on stiffness. Continuous exposure to air drying inhibits strength development due to insufficient water for hydration. Significant stiffness decreases were observed on specimens of stabilized silt and are attributed to microcracking. 相似文献
19.
Amin Eisazadeh Khairul Anuar Kassim Hadi Nur 《Geotechnical and Geological Engineering》2012,30(6):1435-1440
Studies on the chemically stabilized soils have shown that the effectiveness of treatment is largely dependent on soil??s natural environment. In this research, the time-dependent changes induced in permanent cation exchange capacity of lime and phosphoric acid treated soils, comprised mainly of montmorillonite and kaolinite minerals, were investigated. Also, in order to study the relationship between the exchange capacity and acidity/alkalinity of pore water, pH measurements were performed on cured samples. Based on the collected data, it was found that the pH of stabilized soils showed a tendency for reaching soil??s natural pH with increasing curing time. In addition, the increase in number of broken bonds around the edges of soil particles and also the formation of cementitious compounds that acquired negative charges contributed to achieving higher CECp values at longer curing periods. Nevertheless, the kaolinite mineral with pH-dependent structural properties, showed a rather limited behavior in the acidic medium. From engineering point of view, the lime treated samples revealed the highest degree of improvement with an approximately ten-fold strength increase in comparison to the natural soil over an 8?months curing period. 相似文献
20.
Lime treatment of loess in foundation engineering modifies the soil structure, leading to changes in mechanical and hydraulic properties of soil, which in turn will affect the flow of water and transport of contaminants in the loess. In light of this, it is essential to identify the dominant effects of different lime treatments on hydraulic conductivity, and to ascertain the optimum lime treatment. For this purpose, we investigated the effects of dry density and lime content on changes in hydraulic conductivity and microstructure of loess in Yan’an City, China. The results indicate that hydraulic conductivity has a log negative correlation with dry density, and lime addition can result in a decrease of hydraulic conductivity of loess at the same dry density. Under a given degree of compaction, however, lime addition can lead to a decrease in dry density due to an increase in flocculation and aggregations. The significant decrease of dry density leads to an increase in hydraulic conductivity when lime content (in mass percentage) is lower than 3%. Nevertheless, when lime content is higher than 3%, the reactions between loess particles and lime will be intensified with an increase in lime content, and become the primary factors affecting pore characteristics. These reactions can further decrease the hydraulic conductivity of lime-treated loess, and the lowest hydraulic conductivity was obtained for lime-treated loess with 9% lime content. The excess lime (above 9% lime content) dramatically increased pore size, leading to a significant increase in hydraulic conductivity. Therefore, 9% is the optimum lime content for loess treatment, and the degree of compaction in engineering should be higher than 95%. In addition, statistical analysis of microstructure of lime-treated loess shows that the distribution trends of macro- and meso-pores coincided with that of saturated hydraulic conductivity, which indicates that lime content affects saturated hydraulic conductivity of lime-treated loess by changing the soil structure, especially the properties of pores larger than 8 µm. 相似文献