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1.
This study was focused on the correlations between the physical and mechanical properties and geostatistical analysis of the clay of high plasticity (CH) soil based on the experimental data and the data collected from various research studies. Four types of CH soil with liquid limit (LL) of 50, 62, 76 and 88% were collected from the field, tested, compared with the data from literature and qualified using hyperbolic model. X-ray diffraction analyses showed the major constituents of the CH soil with LL of 50% were calcium silicate (Ca2SiO4), aluminum silicate (Al2SiO5) and quartz (SiO2) and the major constituents of the CH soil with LL of 88% were montmorillonite (Na, Ca) 0.33(Al, Mg) 2(Si4O10) (OH)2·nH2O, kaolinite (Al2Si2O5(OH)4) and quartz (SiO2). The index properties, compacted properties, free swelling and compressive strength of the CH soils were investigated and quantified with over 1000 data collected from the literature. Using the mean (μ), standard deviation (σ), variation (σ2) and coefficient of variation parameters of CH soils properties such as density (γ), index properties (LL and PL), compaction properties (OMC and γdmax), swelling index (FS), initial void ratio (eo), compression index (Cc) and undrained shear strength (Su) properties were also studied. Liquid limit of CH soils varied between 50 and 110% and plasticity index varied between 26 and 72%. The wet unit weight (γwet) for the CH soils varied from 1.30 to 2.19 g/cm3. Undrained shear strength (Su) of CH soils were varied from 10 to 184 kPa and quantified very well as a function of liquid limit, plasticity index, moisture content and dry density using the experimental data and data collected from the literature.  相似文献   

2.
The occurrence of sulfate-induced heave of roadways that were chemically stabilized with either lime or cement can require expensive road repairs. Previous research attributed the heave to the formation of an expansive mineral named ettringite. However, not all chemically stabilized soils will exhibit heave. The overall goal of this research was to determine if the sulfate concentration in water can contribute to, or even cause, sulfate induced heave. Two soils, one with a soluble sulfate level below 3000 mg/kg and one with >8000 mg/kg sulfate, were stabilized with either lime or cement and subjected to a capillary soak with distilled water or saturated sulfate water. The low sulfate soils did not swell above the accepted limit of 1.5 %. The high sulfate soils swelled significantly (p < 0.05) above accepted level regardless of the stabilizer used. Overall, stabilized soils subjected to a capillary soak with saturated sulfate water swelled more than soils soaked with distilled water. The results found in this study demonstrated that cement will increase the axial load capacity of the soil, but the soil will still have the potential to heave excessively if sulfate and aluminum are present above the stoichiometric requirements to from ettringite.  相似文献   

3.
Developing countries face the challenge of growing their economy while reducing the negative environmental impacts of industry, thus requiring treatment technologies that are economical and effective. One recent technology developed in the tropical part of Mexico for the remediation of petroleum-contaminated soil was tested in this scale-up project at an industrial level, whereas previously it had only been tested at laboratory scale; 150 m3 of bentonitic mud, contaminated with weathered hydrocarbons (3.4°API) at ~50,000 ppm, was treated with 4 % Ca(OH)2, 4 % organic amendment, and a fine-root tropical grass. Hydrocarbons in soil and in leachates, as well as pH, and acute toxicity (Microtox) were monitored for 28.8 months. At the end of the study, basal respiration, root density, and earthworm toxicity were also measured. The hydrocarbon concentration in soil was reduced to 45 %, and toxicity was eliminated. Hydrocarbons in leachates were reduced to ~1 mg/l, safe for human consumption. The pH adjustment depended on low soil moisture and was stabilized at 7.1. Intense revegetation resulted in good root density, within 90 % of nearby uncontaminated soil under pasture. Basal respiration was increased to levels comparable to uncontaminated tropical soils with agricultural use, pasture and gallery forest. At an industrial scale, strict moisture control was necessary for good pH stabilization. By controlling these conditions and applying this novel treatment process, it was possible to transform a heavily contaminated geological material into a non-toxic, fertile, soil-like substrate capable of maintaining a complete vegetative cover and microbial activity comparable to similar soils in a tropical environment.  相似文献   

4.
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   

5.
The effect of sulphates on the soil stabilisation using mineral additives such as lime, cement and fly ash has been reported by several researchers. The effect of sodium sulphate (Na2SO4) (0–6% by dry weight of soil) on the behaviour of the grey clayey soil (GS) and red clayey soil (RS) stabilised with lime (L) (0–8%), natural pozzolana (NP) (0–20%) and with a combination of lime-natural pozzolana (L–NP) was investigated. The soil specimens were subjected to testing of direct shear strength after 7, 30, 60 and 120 days of curing period. In the absence of Na2SO4, the results show that both clayey soils can be successfully stabilised with L or with a combination of L–NP, which substantially increases their shear strength and produces high values of shear parameters. However, at short curing period and for any content of Na2SO4, a further increase in shear strength and shear parameters is observed. Moreover, after 30 days of curing, the RS specimens stabilised with L or with NP alone are altered when the Na2SO4 is greater than 2%, whereas the GS specimens are not altered. However, the alteration of RS specimens is little when the L and NP are combined on curing with a high content of Na2SO4. Generally, the effect of Na2SO4 on both stabilised clayey soils depends on the curing time, percentage of additives used and their type, mineralogical composition of stabilised soils and Na2SO4 content.  相似文献   

6.
We determined the melting phase relations, melt compositions, and melting reactions of carbonated peridotite on two carbonate-bearing peridotite compositions (ACP: alkali-rich peridotite + 5.0 wt % CO2 and PERC: fertile peridotite + 2.5 wt % CO2) at 10–20 GPa and 1,500–2,100 °C and constrain isopleths of the CO2 contents in the silicate melts in the deep mantle. At 10–20 GPa, near-solidus (ACP: 1,400–1,630 °C) carbonatitic melts with < 10 wt % SiO2 and > 40 wt % CO2 gradually change to carbonated silicate melts with > 25 wt % SiO2 and < 25 wt % CO2 between 1,480 and 1,670 °C in the presence of residual majorite garnet, olivine/wadsleyite, and clinoenstatite/clinopyroxene. With increasing degrees of melting, the melt composition changes to an alkali- and CO2-rich silicate melt (Mg# = 83.7–91.6; ~ 26–36 wt % MgO; ~ 24–43 wt % SiO2; ~ 4–13 wt % CaO; ~ 0.6–3.1 wt % Na2O; and ~ 0.5–3.2 wt % K2O; ~ 6.4–38.4 wt % CO2). The temperature of the first appearance of CO2-rich silicate melt at 10–20 GPa is ~ 440–470 °C lower than the solidus of volatile-free peridotite. Garnet + wadsleyite + clinoenstatite + carbonatitic melt controls initial carbonated silicate melting at a pressure < 15 GPa, whereas garnet + wadsleyite/ringwoodite + carbonatitic melt dominates at pressure > 15 GPa. Similar to hydrous peridotite, majorite garnet is a liquidus phase in carbonated peridotites (ACP and PERC) at 10–20 GPa. The liquidus is likely to be at ~ 2,050 °C or higher at pressures of the present study, which gives a melting interval of more than 670 °C in carbonated peridotite systems. Alkali-rich carbonated silicate melts may thus be produced through partial melting of carbonated peridotite to 20 GPa at near mantle adiabat or even at plume temperature. These alkali- and CO2-rich silicate melts can percolate upward and may react with volatile-rich materials accumulate at the top of transition zone near 410-km depth. If these refertilized domains migrate upward and convect out of the zone of metal saturation, CO2 and H2O flux melting can take place and kimberlite parental magmas can be generated. These mechanisms might be important for mantle dynamics and are potentially effective metasomatic processes in the deep mantle.  相似文献   

7.
The high cost of traditional stabilizing agents such as lime and cement has led to the research on industrial and agricultural wastes as suitable alternatives. Rice growing areas of Kenya accumulate large quantities of rice husk which pose serious disposal problems. When burnt as a means of disposal, the rice husk ash formed is difficult to coagulate and thus contribute to air and water pollution, require a large space for disposal, and cause respiratory health problems when inhaled. Red coffee soil poses serious engineering problems such as swelling due to wetting, shrinkage due to drying, low bearing capacity, and differential settlement leading to cracks and needs improvement for strength and stability in service. Red coffee soil and rice husks samples were obtained from Gatundu and Mwea, respectively. The rice husk was burnt at temperatures between 500 and 700 °C to ensure maximal formation of siliceous component. Chemical analysis on the rice husk ash gave the sum of SiO2, Fe2O3, and Al2O3 as 85.5 % indicating that it has pozzolanic activity. Rice husk ash was applied at 4, 6, 8, and 10 % by weight of dry soil. Plasticity index, liquid limit, and linear shrinkage decreased from 26.1, 67.1, and 13.0 % for lean sample to 18.5, 63.6, and 9.2 %, for 10 % rice husk ash stabilized samples, whereas plastic limit increased from 41.0 to 45.15 %. The soaked California bearing ratio value for rice husk ash stabilized samples increased from 5 to 22 % corresponding to soil subgrade class S4. However, lime-stabilized samples gave higher values.  相似文献   

8.
盐渍土化学固化法是解决盐渍土盐胀、溶陷和腐蚀等不良工程问题的有效方法之一。通过无侧限抗压强度试验、X射线衍射试验、化学成分分析和扫描电镜试验研究了石灰粉、煤灰、水玻璃联合固化硫酸盐渍土的强度特征,分析探讨了其固化机制。试验结果表明：石灰含量小于8%时,石灰、粉煤灰、水玻璃联合固化硫酸盐渍土的抗压和抗剪强度较石灰粉煤灰固化土有大幅度提升,固化土强度随水玻璃浓度几乎呈线性增长。水玻璃固化硫酸盐渍土强度增加的机制在于：水玻璃的碱激发粉煤灰作用和水玻璃与盐渍土中化学成分的吸附作用所生成各类凝胶的填充和包裹,使得骨架颗粒的接触面积增大,颗粒之间的孔隙逐步减小,骨架颗粒由点接触变为面接触,固化盐渍土通过凝胶而黏结成为一个紧密的空间网状整体结构,土体强度得以提高。同时,复杂的物理化学作用大幅度降低了固化盐渍土中 含量,有效地抑制了硫酸盐渍土的盐胀特性。  相似文献   

9.
Oil fields present a potential ecological risk to nearby farmland soil. Here we present a new method designed to evaluate the ability of winter wheat (Triticum aestivum) to contribute to the dissipation of polycyclic aromatic hydrocarbons (PAHs), which are priority pollutants in soils contaminated by oily sludge. The influence of different doses of oily sludge on the dissipation of PAHs was studied along with individual PAH profiles in soils after different periods of plant growth. Five soil samples were artificially contaminated with different percentages of oily sludge (0 %, 5 %, 10 %, 15 % and 20 %). Winter wheat grew in the oily sludge–amended soils for 265 days. PAH content in the soils was monitored over the course of the study. The rate of PAH dissipation is related to the properties of different PAHs, period of winter wheat growth, and oily sludge application dose. Analysis for treated soils indicates that the dissipation of PAHs increased significantly over the first 212 days, followed by minimal changes over the final 53 days of treatment. In contrast, PAH dissipation slowed with increasing oily sludge application. For each PAH, the experimental results showed a significant compound-dependent trend. Winter wheat in the present study significantly enhanced the dissipation of PAHs in oily sludge–contaminated soil.  相似文献   

10.
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   

11.
The mechanism for reclaiming sodic soils using calcium sulfate (CaSO4) could provide a theoretical basis for the field application of CaSO4 substitutes, including the by-products of flue gas desulfurization (BFGD), fly ash, and phosphorus gypsum. In this study, Ca2+ application experiment was conducted to analyze the dynamic changes of the cations in the reclamation of sodic soils with CaSO4. A multicomponent solute transport model (UNSATCHEM) that considers ion adsorption exchange and dynamic changes in the soil’s hydraulic conductivity was subsequently used to simulate and predict the movement of ions. The Ca2+ application experiment consisted of four treatments with four CaSO4 concentrations (0.5, 1, 1.5, and 2 g L?1). When the Ca2+ concentrations in the supplied water were 14.71, 22.06, and 29.41 mmol L?1, Ca2+ achieved penetration, and this process was faster when the Ca2+ concentration in the supplied water was higher. Ca2+ did not achieve penetration when the Ca2+ concentration was 7.35 mmol L?1. UNSATCHEM was able to simulate the transportation mechanism of Ca2+ and Na+ in the soil solution in the Ca2+ application experiment, the adsorption and exchange between the Na+ in the soil colloid and Ca2+ in the soil solution, and the precipitation and dissolution of CaSO4 with a high degree of accuracy. Sodic soil reclamation with CaSO4 was not a short-term process. Compared with applying CaSO4 only once, applying CaSO4 in batches decreased the accumulation of soil salts and promoted its dissolution.  相似文献   

12.
Number 6 fuel oil is one of the most used energy sources for electricity generation. However, leaks can contaminate soil and also groundwater due to leaching. At old sites, the oil may have low toxicity but still contaminate groundwater with foul-tasting compounds even at low concentrations. The purpose of this study was to evaluate the feasibility of applying H2O2 to reduce the leaching potential of a fuel oil contaminated soil. A silt-loam soil was collected from a contaminated thermal-electric plant with a hydrocarbon concentration of 3.2% in soil producing 4.3 mg/l in leachate. Hydrogen peroxide was applied (0.1, 0.2, 0.3, 0.6, 1.2% dry weight basis), and petroleum hydrocarbons were measured in soil and leachate pre- and post-treatment (72 h). At first, the soil and leachate concentrations diminished linearly (24.4 and 27.3% in soil and leachate, respectively). This was followed by a phase in which the concentration in leachate diminished greatly (75.8%) although the concentration in soil was reduced only moderately (15.1%). Overall, hydrocarbons in leachates were reduced 82.4% even though concentrations in soil were only reduced 35.8%. Correlation analysis showed that at only 1.0% w/w H2O2 a concentration of petroleum hydrocarbons in leachate safe for human consumption (≤ 1 mg/l) could be obtained even with a final hydrocarbon concentration in soil > 2%. Thus, this study presents an alternative strategy for remediation of fuel oil contaminated soils in urban environments that protects water sources by focusing on contamination in leachates, without spending extra financial resources to reduce the hydrocarbon concentration in low-toxicity soil.  相似文献   

13.
Soil treatment is commonly resorted in order to improve the strength, stiffness properties of road foundations, and reduce the swelling potential of expansive soils. In Jordan, considerable amount of construction activity is carried out at relatively shallow depths where soil is likely to be unsaturated and subjected to low stresses level. Road damage is frequently observed when it is founded on weak sub-grade in Karak. Therefore, chemical stabilization of the base course, sub base course and sub-grade is essential. The soil will be treated by using sodium silicate and lime with different percentages. An experimental program was designed to study the behavior of soil as the percent of additive agent changes. The results showed that; the geotechnical properties have been improved when soil is treated by mixing lime and sodium silicate. The initial consumption of lime is of 4 and 2?% for sodium silicate. The reaction time is a significant parameter where strength improves as time increases.  相似文献   

14.
A pot experiment was conducted to monitor the dynamic response of photosynthesis of Amorpha fruticosa seedlings to different concentrations of petroleum-contaminated soils from April to September. The results showed that the photosynthetic rates, stomatal conductance and transpiration rate of seedlings significantly decreased in 5–20 g kg?1 petroleum-contaminated soil during the three given sampling period of July 31 (early), August 30 (mid-term) and September 29 (late). However, the intercellular CO2 concentration significantly increased in 10 g kg?1 contaminated soil, while declined in 20 g kg?1 contaminated soil during the early sampling period as well as in 20 g kg?1 contaminated soil during the late sampling period. The leaf relative water content of seedlings significantly increased in 20 g kg?1 contaminated soil during the early sampling period, while it dropped dramatically in 15–20 g kg?1 contaminated soil during the late sampling period. The contents of chlorophyll a, chlorophyll b and the total chlorophyll of seedlings showed a sharp decline during the three sampling periods in contaminated soil. Comprehensively, considering the negative effects of petroleum on the photosynthesis, growth performance and remediation effect on petroleum of A. fruticosa seedlings, this plant was tolerant of petroleum-contaminated soil and was potentially useful for the phytoremediation of petroleum-contaminated sites in northern Shaanxi, China.  相似文献   

15.
Summary The presence of mica in pavements can be detrimental due to the effects of high compressibility and low compacted density it imparts to the soils. Three residual micaceous compressible soils derived from granite, granitic gneiss and phyllite can neither be used as base nor sub-base course in their untreated form. In this study, these soils have been treated with a range of lime and sand contents to determine their effects on consistency, compactability, bearing and compressive strengths and volume stability against swell. With 6–8% lime, soils derived over phyllite and granitic gneiss were rendered suitable for use as sub-base course as their plasticity index, 96 hour soaked CBR values and unconfined compressive strengths (UCS) were improved to satisfy existing local criteria. Similarly, with 30% sand both soils became suitable for sub-base course construction. The use of both additives markedly improved the volume stability of all the soils against swell.  相似文献   

16.
中国北部沿海地区夏季多雨,春季干燥多风,土体吸水膨胀、脱水收缩,降低了固化土的抗压强度,研究固化土干湿交替条件下的力学稳定性是实现其工程利用的前提。室内模拟干湿循环,借助无侧限抗压强度指标探究石灰粉煤灰固化石油污染土的力学分布规律。结果表明:经历干湿循环后固化污染土的质量前6次下降较小,7~8次下降明显,9次后趋于稳定,最大下降幅度为4.5%;固化污染土的抗压强度随干湿循环次数的增加而增强,3次循环后抗压强度较初始强度增加了35%,之后逐渐减弱,7次循环后强度趋于稳定,稳定时强度达到初始强度的70%;固化污染土强度的水稳性随含油率的提高逐渐降低,破坏形态随干湿循环次数的增加由软化型逐渐向硬化型转变;当二灰比为0.75,抗干湿循环稳定性较好。石油污染土重新利用时应注意干湿循环对工程的影响。  相似文献   

17.
Isobaric (200 MPa) experiments have been performed to investigate the effects of H2O alone or in combination with P, S, F or Cl on liquid-phase separation in melts in the systems Fe2SiO4–Fe3O4–KAlSi2O6–SiO2, Fe3O4–KAlSi2O6–SiO2 and Fe3O4–Fe2O3–KAlSi2O6–SiO2 with or without plagioclase (An50). Experiments were heated in a rapid-quench internally heated pressure vessel at 1,075, 1,150 or 1,200 °C for 2 h. Experimental fO2 was maintained at QFM, NNO or MH oxygen buffers. H2O alone or in combination with P, S or F increases the temperature and composition range of two-liquid fields at fO2 = NNO and MH buffers. P, S, F and Cl partition preferentially into the Fe-rich immiscible liquid. Two-liquid partition coefficients for Fe, Si, P and S correlate well with the degree of polymerization of the SiO2-rich liquid and plot on similar but distinct power-law curves compared with equivalent anhydrous or basaltic melts. The addition of 2 wt% S to the system Fe3O4–Fe2O3–KAlSi2O6–SiO2 stabilizes three immiscible melts with Fe-, FeS- and Si-rich compositions. H2O-induced suppression of liquidus temperatures in the experimental systems, considered with the effects of pressure on the temperature and composition ranges of two-liquid fields in silicate melts, suggests that liquid-phase separation may be stable in some H2O-rich silicate magmas at pressures in excess of 200 MPa.  相似文献   

18.
An expansive soil (black cotton soil) treated with up to 10 % cement kiln dust (CKD), a waste obtained from the manufacture of cement, was evaluated for use as a flexible pavement construction material. Laboratory tests were carried out on specimens compacted with British Standard light, British Standard light or standard Proctor (relative compaction = 100 %) energy. Results obtained show that the index properties of the soil improved with CKD treatment. Peak unconfined compressive strength of 357.07 kN/m2 and California bearing ratio (CBR) of 7 % as well as resistance to loss in strength of 44 % were recorded at 10 % CKD treatment. Reduction in the particle sizes with curing period was observed when samples were viewed through the scanning electron microscope. The study showed that CKD can be beneficially used to improve the subgrade of lightly trafficked roads and as admixture in lime stabilization during construction of flexible pavements over expansive soil.  相似文献   

19.
Using various additives has been considered as one of the most common stabilization methods for improvement of engineering properties of fine-grained soils. In this research the effect of sewage sludge ash (SSA) and hydrated lime (HL) on compressive strength of clayey soil was investigated. For this purpose, 16 kinds of mixtures or treatments were made by adding different amounts of SSA; 0, 5, 10 and 15% by weight and HL; 0, 1, 3 and 5% by weight of a clayey soil. First, compaction characteristics of the treatments were determined using Harvard compaction test apparatus. So that, 12 unconfined compressive strength test specimens were made using Harvard compaction mold from each treatments taking into account four different curing ages, including 7, 14, 28 and 90 days in three replications. Therefore, a total of 192 specimens were prepared and subjected to unconfined compressive strength tests. The results of this study showed that the maximum dry density of the treated soil samples decreases and their optimum water content increases by increasing the amount of SSA and hydrated lime in the mixtures. It is also found that the adding of HL and SSA individually would increase the compressive strength up to 3.8 and 1.5 times respectively. The application of HL and SSA with together could increases the compressive strength of a clayey soil more efficiently even up to 5 times.  相似文献   

20.
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