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Journal ArticleDOI

Influence of wetting–drying cycles on swell–shrink behaviour of GPA-reinforced expansive clay beds

02 Jul 2020-Geomechanics and Geoengineering (Informa UK Limited)-Vol. 15, Iss: 3, pp 172-185
TL;DR: Granular pile-anchor (GPA) technique is an innovative tension-resistant foundation technique which can effectively ward off the dual swell shrink problem posed by expansive clays as discussed by the authors.
Abstract: Granular pile-anchor (GPA) technique is an innovative tension-resistant foundation technique which can effectively ward off the dual swell–shrink problem posed by expansive clays. The other tension...
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Journal ArticleDOI
TL;DR: In this article, the relative performance of different remedial techniques in vogue and those proposed in the recent years was studied in a site on NIT Warangal campus where natural expansive clay bed is present.
Abstract: Expansive soils being susceptible for moisture variations undergo cyclic seasonal movements that pose serious stability concerns for structures resting on them, especially when they are lightly loaded ones. The concerted efforts made by various researchers across the world enabled them to develop remedial solutions to mitigate these problems with varied degree of success. The present work is an effort to study the relative performance of the different remedial techniques in vogue and those proposed in the recent years. These techniques were adopted below the shallow footings at a site on NIT Warangal campus where natural expansive clay bed is present. This study revealed that the sand cushion and CNS cushion could reduce the heave by 56 to 64%; but in case of sand cushion, an increasing trend of heave with number of cycles of wetting and drying was observed. The chemical alteration by lime could reduce the heave by 59% and by CaCl2 and CaCl2–Na2SiO3 the heave could be reduced by 70 and 73%, respectively. The recently promulgated concrete and granular anchor piled footings have shown the heave reduction up to 63 and 78%, respectively. Further, it is found that the combined effect of CNS cushion along with chemical modification and/or tension/anchor piled footing systems were found to be synergistically more effective than individual techniques in controlling the seasonal movements of footings and flooring/lining panels. Interestingly, none of these remedial techniques could overcome the shrinkage movements though these movements are observed to be insignificant in case of piled footings.

2 citations

Journal ArticleDOI
TL;DR: In this paper, the effect of sand compaction piles on the swelling and shrinkage behavior of expansive clay soil was investigated using a modified Proctor mold and a circular footing, where the diameter of the compaction pile was selected to give a replacement area ratio equal to 57%.
Abstract: This study aims to investigate the effect of sand compaction piles on the swelling and shrinkage behavior of expansive clay soil. A series of experimental laboratory tests were carried out using the modified Proctor mold and a circular footing. The diameter of the sand compaction pile was selected to give a replacement area ratio equal to 57%. To model the swelling and shrinkage cycles, water was added to the sample and the heave was recorded at regular time intervals. The shrinkage was obtained by heating the outer surface of the modified Proctor mold at a temperature of 110°C ± 5°C by a development heating system designed for this purpose to accelerate the shrinkage process. The vertical movement was recorded at regular time intervals. The swelling and shrinkage cycles were carried out under an externally applied pressure equal to 120 kPa. The main results of this study showed that, for untreated expansive soil, the swelling potential reaches the highest value at the second cycle and started to decrease for the subsequent cycles. After the fourth cycle, the swelling potential decreases and reaches about half the value of the initial swelling potential and the equilibrium state occurs. For expansive soil treated with a sand compaction pile, it is found that there is a significant reduction in both swelling and shrinkage potential. Moreover, it is observed that after the first cycle both the swelling and shrinkage potential decrease significantly, and both reach a negligible value after the second cycle.

2 citations

Journal ArticleDOI
TL;DR: In this article, the results of laboratory-scale swell shrink tests performed in an oedometer on an expansive soil stabilised by calcium carbide residue-fly ash (CCR-FA) columns are presented.
Abstract: This paper presents the results of laboratory-scale swell-shrink tests performed in an oedometer on an expansive soil stabilised by calcium carbide residue-fly ash (CCR-FA) columns. The expansive s...

1 citations

References
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Journal ArticleDOI
TL;DR: In this paper, a new elasto-plastic framework for unsaturated soils is proposed, involving coupling of hydraulic hysteresis and mechanical behaviour, and a specific constitutive model for isotropic stress states is proposed.
Abstract: Consideration of the different roles of pore air pressure, pore water pressure within bulk water and pore water pressure within meniscus water suggests that the degree of saturation will have a significant influence on the stress–strain behaviour of an unsaturated soil, in addition to any influence of suction. This suggestion is supported by experimental evidence. In the light of this, a new elasto-plastic framework for unsaturated soils is proposed, involving coupling of hydraulic hysteresis and mechanical behaviour. Within the proposed framework, plastic changes of degree of saturation influence the stress–strain behaviour, and plastic volumetric strains influence the water retention behaviour. A specific constitutive model for isotropic stress states is proposed, and model predictions are compared with experimental results, in order to demonstrate some of the capabilities of the new framework. Forms of behaviour that can be represented include proper transitions between saturated and unsaturated types ...

719 citations


"Influence of wetting–drying cycles ..." refers background in this paper

  • ...Expansive soils swell when they absorb water and shrink when water evaporates from them (Walsh et al. 1993, Wheeler et al. 2003, Lu and Lykos 2004)....

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Journal ArticleDOI
TL;DR: In this article, the authors found abundant thaumasite, a complex calcium-silicate-hydroxide-sulfate-carbonate-hyd rate mineral, forming a solid solution series with ettringite.
Abstract: Expansive reactions between lime and sulfate-bearing clay soils have attracted little attention until relatively recently. Lime treatment of Stewart Avenue in Las Vegas, Nevada, had induced heave in excess of 12 in. Heaved areas are found to contain abundant thaumasite, a complex calcium-silicate-hydroxide-sulfate-carbonate-hyd rate mineral. Thaumasite forms a solid solution series with ettringite, a calcium-aluminum-hydroxide-sulfate-hy drate mineral. In the presence of aluminum, ettringite forms first and is replaced by thaumasite only at temperatures below 15°C. The mechanism of heave is a complex function of available water, the percentage of soil clay, and ion mobility. Only the long-term possolanic chemistry of normal lime-soil reactions is disrupted. Cation exchange, agglomeration, and carbonation are unaffected. With the present state of knowledge, lime-induced heave is difficult to predict for all but most obvious conditions.

365 citations

Journal ArticleDOI
TL;DR: In this paper, the effect of fly ash content on the free swell index, swell potential, swelling pressure, plasticity, compaction, strength, and hydraulic conductivity characteristics of expansive soil was evaluated.
Abstract: This note presents a study of the efficacy of fly ash as an additive in improving the engineering characteristics of expansive soils. An experimental program has evaluated the effect of the fly ash content on the free swell index, swell potential, swelling pressure, plasticity, compaction, strength, and hydraulic conductivity characteristics of expansive soil. The plasticity, hydraulic conductivity and swelling properties of the blends decreased and the dry unit weight and strength increased with an increase in fly ash content. The resistance to penetration of the blends increased significantly with an increase in fly ash content for a given water content. Excellent correlation was obtained between the measured and predicted undrained shear strengths.

348 citations

Journal ArticleDOI
TL;DR: A 3.5 km (2.2 mi) section of a road in Georgia developed unexpected transverse bumps within 6 months after construction and the source of the bumps appeared to be expansion within the cement-stabilized base course as discussed by the authors.
Abstract: A 3.5-km (2.2 mi) section of a road in Georgia developed unexpected transverse bumps within 6 months after construction. The source of the bumps appeared to be expansion within the cement-stabilized base course. Laboratory examination of samples from areas showing distress revealed the presence of ettringite, a calcium sulfoaluminate the formation of which can be accompanied by severe expansion. This expansive materials was the probable cause of the volume changes causing the transverse bumps. The calcium and alumina needed to form ettringite ware available from the portland cement and the stabilized soil`s clay minerals. The source of the sulfur was identified as the well water that was mixed with the cement-stabilized base. Sulfate attack of cement-stabilized soils is a relatively infrequent problem, but it is highly destructive when it occurs. Currently, there are no firm criteria for identifying when sulfate attack of a cement-stabilized soil is a potential problem nor are there established methods of preventing the attack.

165 citations

Journal ArticleDOI
B. R. Phanikumar1
TL;DR: In this article, 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 was compared.
Abstract: 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 pote...

79 citations


"Influence of wetting–drying cycles ..." refers background in this paper

  • ...…of artificial sand-clay and gravel-clay mixes and (iii) chemical stabilisation using cement, lime, CaCl2 and fly ash (Chen 1988, Petry and Little 1992; Hunter 1998, Rollings et al. 1999, Acosta et al. 2003, Hoyos et al. 2004, Phanikumar and Sharma 2004, Phanikumar 2009, Phanikumar et al. 2009)....

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