T. Thyagaraj

Laboratory Studies on Stabilization of an Expansive Soil by Lime Precipitation Technique

Lime stabilization prevails to be the most widely adopted in situ stabilization method for controlling the swell-shrink potentials of expansive soils despite construction difficulties and its ineffectiveness in certain conditions. In addition to the in situ stabilization methods presently practiced, it is theoretically possible to facilitate in situ precipitation of lime in soil by successive permeation of calcium chloride (CaCl2 ) and sodium hydroxide (NaOH) solutions into the expansive soil. In this laboratory investigation, an attempt is made to study the precipitation of lime in soil by successive mixing of CaCl2 and NaOH solutions with the expansive soil in two different sequences.Experimental results indicated that in situ precipitation of lime in soil by sequential mixing of CaCl2 and NaOH solutions with expansive soil developed strong lime-modification and soil-lime pozzolanic reactions. The lime-modification reactions together with the poorly de- veloped cementation products controlled the swelling potential, reduced the plasticity index, and increased the unconfined compressive strength of the expansive clay cured for 24 h. Comparatively, both lime-modification reactions and well-developed crystalline cementation products (formed by lime-soil pozzolanic reactions) contributed to the marked increase in the unconfined compressive strength of the ex-pansive soil that was cured for 7–21 days. Results also show that the sequential mixing of expansive soil with CaCl2 solution followed by NaOH solution is more effective than mixing expansive soil with NaOH solution followed by CaCl2 solution. DOI: 10.1061/(ASCE)MT .1943-5533.0000483.

Influence of Osmotic Suction on the Soil-Water Characteristic Curves of Compacted Expansive Clay

Unsaturated clays are subject to osmotic suction gradients in geoenvironmental engineering applications and it therefore becomes important to understand the effect of these chemical concentration gradients on soil-water characteristic curves (SWCCs). This paper brings out the influence of induced osmotic suction gradient on the wetting SWCCs of compacted clay specimens inundated with sodium chloride solutions/distilled water at vertical stress of 6.25 kPa in oedometer cells. The experimental results illustrate that variations in initial osmotic suction difference induce different magnitudes of osmotic induced consolidation and osmotic consolidation strains thereby impacting the wetting SWCCs and equilibrium water contents of identically compacted clay specimens. Osmotic suction induced by chemical concentration gradients between reservoir salt solution and soil-water can be treated as an equivalent net stress component, ( pπ ) that decreases the swelling strains of unsaturated specimens from reduction in ...

Physico-Chemical Effects on Shrinkage Behavior of Compacted Expansive Clay

AbstractPhysico-chemical effects have a significant impact on the behavior of clay barriers due to the interactions between the pore fluid and clay particles, and they pose a great challenge because the efficiency of clay barriers and cover systems may be altered. Therefore, this paper highlights the effect of physico-chemical factors on shrinkage behavior of compacted expansive clay. To achieve this, the compacted clay specimens were inundated with distilled water, NaCl, and CaCl2 salt solutions in separate oedometer cells at a vertical pressure of 6.25 kPa and allowed to swell. The swollen specimens were gradually shrunk until the specimens attained constant mass, and the changes in void ratio and water content were monitored during drying. The experimental results showed that magnitude of induced osmotic suction and type of pore fluid had a significant impact on shrinkage behavior of compacted clay specimens due to the changes in soil structure. The average pore size of compacted specimens significantl...

Laboratory Investigations of In Situ Stabilization of an Expansive Soil by Lime Precipitation Technique

AbstractThe present investigation examines the efficiency of an in situ lime precipitation technique in stabilizing expansive soil through laboratory-scale model tests. Expansive soil was compacted in a cylindrical mold and sequentially permeated with CaCl2 and NaOH solutions into the expansive soil through a central hole filled with coarse sand. Successive permeation of CaCl2 and NaOH solutions into the compacted expansive soil resulted in precipitation of lime in the expansive soil mass. The precipitated lime reduced the plasticity index, controlled the swell–shrink potentials, and increased the unconfined compressive strength of the expansive soil by both strong lime modification reactions and soil–lime pozzolanic reactions. The results are corroborated with microfabric studies on lime precipitation treated specimens, which showed the formation of cementation bonds.

In-situ stabilization of an expansive soil in desiccated state

Abstract This paper examines the efficiency of in-situ stabilization of expansive soil by lime slurry technique in desiccated state through laboratory and field experimental studies. The laboratory and field studies consists of permeating 34% hydrated lime slurry into the desiccated soil through vertical holes and measuring the physico-chemical, index and engineering properties before and after treatment at different radial distances. The distinct changes in the physico-chemical and index properties of the expansive soil indicate the occurrence of lime modification reactions and pozzolanic reactions on lime migration into the inter-connected shrinkage cracks. The lime slurry treatment increased the soil pH (≍ 12) to the levels that are conducive for the pozzolanic reactions to occur. The soil-lime reactions reduced the swelling potential and increased the unconfined compressive strength of lime slurry treated expansive soil. The test results encourage the application of lime slurry technique to expansive soil deposits during dry season upon development of shrinkage cracks.

Relative efficiencies of electrolytes in stabilization of an expansive soil

Sequential permeation of calcium chloride and sodium hydroxide solutions into the soil mass leads to the formation of lime in the in-situ soil mass owing to chemical reactions. Previous studies have demonstrated that the lime precipitation modifies the expansive soil properties both by lime modification and pozzolanic reactions. However, the independent contributions of either calcium chloride solution or sodium hydroxide solution in stabilizing the expansive soil are not known. Therefore, an attempt is made in the present investigation to examine the relative efficiencies of calcium chloride solution, sodium hydroxide solution and lime precipitation in stabilizing the expansive soil by comparing the physico-chemical and index properties, oedometer swell potentials and unconfined compressive strength of treated specimens. The present investigation also brings out the relative efficiencies of hydrated lime and precipitated lime in stabilizing the expansive soil. The experimental results showed that treating the expansive soils with calcium chloride and sodium hydroxide solutions independently promoted only the short-term reactions whereas the sequentially treating the expansive soil with calcium chloride and sodium hydroxide solutions resulted in the formation of lime precipitation, which could mobilize both short-term lime-modification reactions and long-term soil-lime pozzolanic reactions.

Collapse behaviour of compacted red soil

The phenomenon of collapse assumes significance in the geotechnical engineering applications such as earth dams and highway and railway embankments as the compacted soils in these applications are susceptible to wetting-induced failures. Therefore, the present study focuses to understand the influence of placement conditions and vertical stress on the wetting-induced collapse behaviour of compacted red soil through series of single oedometer collapse tests. The loading–collapse (LC) curves of compacted red soil for different dry unit weights were established over a large range of matric suctions in order to analyse the experimental results in the context of Barcelona basic model (BBM) elasto-plastic framework and also the experimental results were supported using the concept of LC curves defined in the BBM framework. The experimental results showed a path-dependent relationship of collapse potential with the water content at a given dry unit weight and vertical stress. The position of LC curves of the compacted specimens with respect to the wetting path illustrated a decrease in the soil collapse with the increase in dry unit weight. Thus the present experimental results demonstrate that the BBM framework aids in predicting the nature of volume change and the point of maximum collapse.

Determination of volumetric shrinkage of an expansive soil using digital camera images

AbstractThe volume change during drying of compacted expansive soils occurs in the form of reduction in overall volume and development of cracks. Accurate determination of volume of shrunken soil s...