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1.
Clay soil with low-bearing capacities can present great problems underlying pavement and light structures due to uncertainty associated with their performance. This paper describes a sonic based testing methodology for quality control of a surface stabilized soil. From an engineering aspect, an increase in water content has a number of disadvantageous consequences: cohesion decreases, the soil swells, the alternating dry-out/shrinkage and wetting/swelling effects destroy the rock or a soil structure. Cement is mixed into the soil to increase both the strength and the usability of local soils in constructions purposes. This is to overcome the problems by strengthening the soil underlying the structure or diminishing the leads transmitted from the foundation to the soil. The compressive strength of the stabilized soil is highly dependent on the type of soil, moisture content, cement content, and compaction work, and can therefore vary significantly in the field. The authors performed the quality control by measuring the sonic and tensile strength velocity in the stabilized soil that has been correlated to compressive strength in native materials. The improvement of the soil materials by the addition of cement could make the material suitable as filling materials, foundation and/or a road base construction. The quality control for the stabilized soils was investigated using sonic measurements and strength gain. The test methods were performed to evaluate the degree of improvement achieved through the measurement of compression and shear-wave velocities of the soil under study. Scanning electron microscopy and electron dispersive X-ray analyses were performed on raw and laboratory treated for qualitative understanding the strength minerals formed during stabilization. The sonic test showed a considerable improvement with curing time and percentages of stabilizer. Mineralogical studies indicated the formation of silica and alumina hydrates along with interwoven structure of cement treated clay particles suggesting adequate mixing of the soil and binder owing to the strength of the soil materials.  相似文献   

2.
In this article, the potential of a binder developed by admixing fly ash and ground granulated blast furnace slag (GGBS) to stabilise expansive soils is evaluated. Laboratory tests included determination of free swell index, swell potential and swelling pressure tests of the soil/binder mixtures at different mixing ratio. The test results showed decrease in the swelling behaviour of the soil with increase in binder content. The percent swell–time relationship was observed to fit the hyperbolic curves enabling us to predict the ultimate percent swell from few initial test results. Addition of 1% of lime to the binder showed further improvement in reducing swelling. A good linear relationship is established between percent oedometer swell and modified free swell index (MFSI) for soil/binder mixtures without lime but the same has not been observed in the presence of lime. The compressibility characteristics of the soil/binder mixtures reduced nominally with increase in binder content but in the presence of lime, the compressibility reduced significantly. Binder used in this study has been found to be effective and economic to stabilise expansive soils with lesser amount of chemical additives such as lime.  相似文献   

3.
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   

4.
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   

5.
Expansive soils swell on absorbing water and shrink on evaporation thereof. Because of this alternate swelling and shrinkage, civil engineering structures founded in them are severely damaged. For counteracting the problems of expansive soils, different innovative techniques were suggested. Stabilization of expansive clays with various additives has also met with considerable success. This paper presents, by comparison, the effect of lime and fly ash on free swell index (FSI), swell potential, swelling pressure, coefficient of consolidation, compression index, secondary consolidation characteristics and shear strength. Lime content (weight of lime/weight of dry soil) was varied as 0%, 2%, 4%?and 6%?and fly ash content (weight of fly ash/weight of dry soil) as 0%, 10%?and 20%. A fly ash content of 20%?showed significant reduction in swell potential, swelling pressure, compression index and secondary consolidation characteristics and resulted in increase in maximum dry density and shear strength. Swell potential and swelling pressure decreased with increase in lime content also. Further, consolidation characteristics improved. Compaction characteristics and unconfined compression strength improved at 4%?lime and reduced at 6%?lime.  相似文献   

6.
Investigations on the mechanical behavior of compacted gravel lateritic soils have been the subject of several studies. Used as road materials, soils tests were mainly performed using standard tests. Static loads as unconfined compression test (UCT) remain the only engineering approach used. Alternative testing techniques can be chosen as supplementary tests for characterizing pavement materials. These researches were conducted so as to determine the response of these particular and problematic soils in its compacted form with road traffic loads. This paper presents the results of research conducted to investigate the effect of the soil compacity on the resilient modulus of lateritic soils. The influence of the percentage of cement added so as to stabilize each sample at the optimum modified proctor (OPM) State was also determined. Soil big specimens of around 180 mm diameter (with length to diameter aspect ratio of 2:1) were prepared according to the standard procedure described by AASHTO T 307 and then were subjected to repeated load triaxial tests. The models used, analyzed and developed in this paper are mainly the Andrei and the Uzan–Witczak universal model. Test results showed that the specimen compacity has no significant influence on the resilient modulus of the investigated gravel lateritic soils. Soil specimens with variation of the percentage of cement added exhibited the highest resilient modulus values while the specimens with variation of the compacity exhibited the lowest values. The resilient modulus variation seems to be independent of the level of stress.  相似文献   

7.
One of the most important factors that determine engineering properties of soils are the type and the amount of clay present in soil. Kaolinite being a very common and non-swelling clay mineral in soil was chosen as the medium, and significance of the change in swelling property of kaolinite due to contaminant-clay interaction was investigated. The amount of change in swelling percentages of the kaolinite due to contamination with 10,000 ppm solutions of Pb(NO3)2 and Zn(NO3)2 was determined using oedometers. For uncontaminated kaolinite, the amount of swell was determined as 2.2%. For Pb-contaminated and Zn-contaminated kaolinite, these values reached to 5.8 and 5.3%, respectively. Besides heavy metals, kaolinite was also contaminated with 4 N NaOH. The biggest change in the amount of swelling was obtained from NaOH-contaminated kaolinite which is 13.9%. In addition to swelling percentages, swelling pressures were also determined. The swelling pressure of the uncontaminated kaolinite was found as 1.06 N/cm2. For Zn and Pb-contaminated kaolinite, this value reached up to 2.0 and 2.6 N/cm2. The NaOH-contaminated kaolinite has the greatest swelling pressure which was 230 N/cm2.  相似文献   

8.
电阻率法评价膨胀土改良的物化过程   总被引：4，自引：1，他引：3  
掺石灰、粉煤灰是工程中通常采用的改良膨胀土的方法。土电阻率是土的基本物理指标之一,其变化可反映土的其他物理性质指标的变化。通过掺灰改良膨胀土不同养护龄期下的电阻率测试以及膨胀量、膨胀力及无侧限抗压强度等试验研究,探讨了掺灰改良膨胀土养护过程中的物理化学反应过程。根据养护过程中的电阻率随龄期的变化规律,可将改良膨胀土的物理化学反应过程划分为瞬时反应阶段、主体反应阶段、残余反应阶段和稳定阶段4个不同阶段。针对改良膨胀土质量控制和评价体系中存在的不足,提出了基于电阻率指标的改性膨胀土的质量评价方法,通过试验证实了该方法的有效性和实用性。  相似文献   

9.
Due to the difficulties experienced with the so-called gatch soils, the Ministry of Public Works of Kuwait engaged the services of the firm DORSCH, Consulting Engineers of Munich, Germany, to study the properties of gatch and to recommend methods to improve its suitability for road construction. An investigation program was agreed upon and selected samples were obtained from Kuwait.Prior to the geotechnical tests, mineralogical analyses were carried out. Surprisingly they found no trace in the samples of gypsum which was believed to cause damage to the highways built on gatch. The geotechnical tests performed indicated that the gatch soils were very sensitive to moisture and were therefore unsuitable as highway construction materials. However, their properties could be improved by various stabilization methods. It was found that cement stabilization was the most promising method since it not only increased the bearing capacity of the soil but also reduced its swelling characteristics.  相似文献   

10.
查甫生  刘松玉  杜延军 《岩土力学》2006,27(Z1):549-554
研究掺粉煤灰对合肥膨胀土的物理性质指标以及胀缩性指标等的影响,探讨利用粉煤灰改良膨胀土的措施与效果。试验研究结果表明,在膨胀土中掺入适量的粉煤灰可有效降低膨胀土的塑性指数、降低膨胀势、减小线缩率与降低活性。在膨胀土中掺入粉煤灰还可改变膨胀土的击实特性,一定击实功作用下,随着掺灰率的增加,土体的最优含水率与最大干密度均减小,膨胀土中掺入粉煤灰后,膨胀土可在较小的含水率下通过击实或压实达到稳定。掺灰膨胀土的膨胀量与膨胀力随养护龄期的增长而减小;没有经过养护的掺灰土,其无侧限抗压强度随掺灰率的变化几乎没有变化,经过7 d养护后,土的无侧限抗压强度有所增长,并且存在一个峰值点,合肥膨胀土的无侧限抗压强度所对应的最佳掺粉煤灰率约为15 %～20 %。  相似文献   

11.
At present, nearly 100 million tonnes of fly ash is being generated annually in India posing serious health and environmental problems. To control these problems, the most commonly used method is addition of fly ash as a stabilizing agent usually used in combination with soils. In the present study, high-calcium (ASTM Class C—Neyveli fly) and low-calcium (ASTM Class F—Badarpur fly ash) fly ashes in different proportions by weight (10, 20, 40, 60 and 80 %) were added to a highly expansive soil [known as black cotton (BC) soil] from India. Laboratory tests involved determination of physical properties, compaction characteristics and swell potential. The test results show that the consistency limits, compaction characteristics and swelling potential of expansive soil–fly ash mixtures are significantly modified and improved. It is seen that 40 % fly ash content is the optimum quantity to improve the plasticity characteristics of BC soil. The fly ashes exhibit low dry unit weight compared to BC soil. With the addition of fly ash to BC soil the maximum dry unit weight (γdmax) of the soil–fly ash mixtures decreases with increase in optimum moisture content (OMC), which can be mainly attributed to the improvement in gradation of the fly ash. It is also observed that 10 % of Neyveli fly ash is the optimum amount required to minimize the swell potential compared to 40 % of Badarpur fly ash. Therefore, the main objective of the study was to study the effect of fly ashes on the physical, compaction, and swelling potential of BC soils, and bulk utilization of industrial waste by-product without adversely affecting the environment.  相似文献   

12.
Behavior of expansive soils stabilized with fly ash   总被引：6，自引：0，他引：6  
Expansive soils cause serious problem in the civil engineering practice due to swell and shrinkage upon wetting and drying. Disposal of fly ash, which is an industrial waste in both cost-effective and environment-friendly way receives high attention in China. In this study, the potential use and the effectiveness of expansive soils stabilization using fly ash and fly ash-lime as admixtures are evaluated. The test results show that the plasticity index, activity, free swell, swell potential, swelling pressure, and axial shrinkage percent decreased with an increase in fly ash or fly ash-lime content. With the increase of the curing time for the treated soil, the swell potential and swelling pressure decreased. Soils immediately treated with fly ash show no significant change in the unconfined compressive strength. However, after 7 days curing of the fly ash treated soils, the unconfined compressive strength increased significantly. The relationship between the plasticity index and swell-shrinkage properties for pre-treated and post-treated soils is discussed.  相似文献   

13.
《Applied Geochemistry》2001,16(11-12):1413-1418
In order to understand the relationship between forms of Al in soils and the uptake of Al from soil into tea plants, tea leaves and soils were collected from 13 tea gardens in the east of China. The Al concentration measured in the tea leaves was found to be best predicted by ‘available’ Al extracted by 0.02 M CaCl2. The relationship appears to be linear, with a correlation coefficient of 0.77 (P=0.01). The Al content of tea leaves increases with a decrease of soil pH. This relationship is non-linear with a marked increase in leaf Al for soils with pH <5.0. The amounts of Al in soils extracted with 0.02 M CaCl2 was much less than other forms of Al in soils. The amount of Al measured in the tea leaves was directly related to both the ‘available’ form of Al in the soils and soil pH. Soil pH was identified as a major factor that controls the uptake of Al from soil into the tea leaves.  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.
In this paper, marble waste is evaluated as a secondary material to be utilized as potential stabilizer to improve the volume change and strength characteristics of sand-amended expansive soil, proposed as a possible landfill, pavement or sub-base material in a semi-arid climate. An experimental program was conducted on sand-expansive soil enhanced with marble waste, abundantly found as a by-product of construction industry, obtained from two different sources with different gradations, denoted as marble powder (MP) and marble dust (MD). One-dimensional swell, volumetric shrinkage, consolidation, unconfined compressive and flexural strength tests were conducted on expansive soil–sand mixtures with 5, 10 and 20% waste marble inclusions over curing periods of 7, 28 and 90 days. Test results showed that 10% marble powder and 5% marble dust by dry mass were the optimum amounts for mitigating the swell–shrink potential and compression index as well as yielding the highest unconfined compressive and flexural strength values. Moreover, the rate of reduction in swell potential versus the flexural strength over the curing periods studied is highest in 10% MP- and 5% MD-included specimens, the latter being more insensitive to this change. The soil mixtures displayed brittle behavior after marble addition, hence its utilization as a secondary additive to sand-amended expansive soil is recommended for soils exposed to lower flexural loads such as light traffic.  相似文献   

16.
Expansive soils undergo alternate swelling and shrinkage due to cyclic wetting and drying when left to nature. This property of Expansive soil affects its strength and stiffness characteristics thereby causing damage and distress to structures built on them. Industrial wastes can be added scientifically to these soils in modifying and reducing their swelling and shrinkage behaviour and increasing their strength and stiffness. In this technical article, an attempt has been made to study the compressibility and drainage characteristics of these soils using economic and ecofriendly industrial wastes such as Fly Ash and Dolochar as stabilizers. This paper also focuses on many other improved engineering properties of base soil like liquid limit, plasticity index, differential free swell, compaction and consolidation characteristics of Expansive (BC) soil stabilized with Fly Ash and Dolochar in different proportions. The virgin Expansive soil has been collected from eastern part of India (Odisha) and different percentages of Fly Ash (5, 10, 15, 20, 25 and 30 %) and Dolochar (5, 10, 15, 20, 25 and 30 %) were added to it, to predict the influence of these additives on compaction and consolidation characteristics of Expansive soil. Addition of both Fly Ash and Dolochar were found to decrease the index properties such as liquid limit, plastic limit, plasticity index, swelling index and enhancing the consolidation as well as drainage characteristics of Expansive soil. However, the maximum dry density of soil was found to decrease with addition of Fly Ash and increase with addition of Dolochar.  相似文献   

17.
Stabilization of lateritic soils with phosphoric acid   总被引：1，自引：0，他引：1  
Summary This paper describes a laboratory study on the stabilization of lateritic soils with phosphoric acid-H3PO4. This method is most promising for road and airport pavement construction in tropical regions where fine textured lateritic soils (red clays and silts) occur over large areas. The iron and aluminum phosphates formed are hard and insoluble. The main source of iron is free iron oxide, and the aluminum sources are free aluminum oxide, exchangeable cations and clay minerals (hydrated aluminum silicates). Four different soil samples were studied, but the most comprehensive study was carried out with a lateritic soil evolved from weathered basaltic bedrock. The variables of the test specimens were: percentage of acid, moulding water content, compaction energy, and curing time. Strength tests performed were the axial or unconfined compression test and the indirect tensile or diametrical compression test. With 5% of phosphoric acid to dry weight of soil, values of compressive strength around 4.0 MPa were obtained after 28 days curing.  相似文献   

18.
季节冻土区含盐土公路路基在季节性冻胀、盐胀和融沉作用下,发生大量的道路病害,给道路的安全运营带来了严重的隐患。在考察大量现场道路病害的基础上,针对甘肃省季节冻土区公路沿线盐渍化道路病害比较严重的地段,选取几种典型的盐渍土进行室内冻融循环试验来研究它们在周期波动温度条件下冻胀、盐胀和融沉特性,进一步探讨盐渍土地区道路病害产生的机制。试验结果发现,含盐量对路基土冻胀、融沉和盐胀等变形过程有明显的影响,不同的含盐量路基土膨胀机制不同。含盐量较高的土体,变形主要由盐胀引起,没有明显的融沉变形;含盐量较低的路基土,变形主要由冻胀和融沉引起,可能存在盐胀;对于无盐但冻胀敏感性路基土,其变形主要由冻胀和融沉引起。另外,开放系统下盐渍土反复冻融循环后含水率重新分布,含水率普遍增加,且形成了两端含水率高、中间低的现象。  相似文献   

19.
南水北调中线工程实践研究表明,膨胀土的电导率与自由膨胀率呈现线性关系。引江济淮试验工程为开发膨胀土判别快速方法以及提出针对江淮地区土质的电导率法判别适用标准,开展膨胀土电导率特征实验研究。工程现场取多组土样进行基本性质、膨胀性和不同含水率下的电导率实验,寻求该地区膨胀土电导率与含水率和自由膨胀率的关系。研究表明,电导率随土体含水率增加呈现先增加后减小的变化趋势,土体处于液限含水率附近状态下,具有最强的导电性,电导率具有峰值特征。相同含水率条件下,土体的膨胀性越强电导率越大;电导率和自由膨胀率总体上线性相关,试样在液限含水率附近时相关性最大;线性经验模型的精度由相关性水平控制,本试验提出的江淮地区弱膨胀土电导率经验模型的精度控制标准为R2=0.78,可以达到自由膨胀率实测值的精度水平,具有实用价值。  相似文献   

20.
The factors controlling the expansive nature of the soils and rocks in Northern Oman were studied. Basic geotechnical data from over 40 sites were collected and using empirical relationships, swelling potentials were identified. A laboratory testing program was carried out using undisturbed samples from these swell pressures up to 3.5 MPa, and swell percent values up to 30 were measured. The clay minerals and cations of these samples were determined and Na-smectite was identified as being the main clay-mineral present. Microfabric studies showed generally dense clay matrices. However, these swelling materials exist as impersistent bands with non-swelling soils and rocks which makes prediction of the ground heave problematic.  相似文献   

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