Effect of Unit Weight on Porosity and Consolidation Characteristics of Expansive Clays

This study investigated the relationship between pore characteristics and unit weight of clayey soils. This relationship was particularly important in case of expansive soils, as the pore characteristics determine moisture flux boundaries, which in turn represent volume change behavior. Current research tried to evaluate the effect of compaction unit weight on the pore size and pore volume along with consolidation and swell characteristics on two expansive clays from semi-arid environment. The two selected clays represent soils with different degrees of expansion, particle size and mineralogy. Pore size characterization for these two soils was performed using Mercury Intrusion Porosimetry, while swell and consolidation characteristics were determined using a conventional oedometer test. Samples for both tests were compacted at different unit weights including, 100, 95, 90, 80, 75, and 70 % of maximum dry unit weight (MDUW) obtained from standard proctor. The compaction water content was kept constant for all unit weight levels. Both pore volume and pore size distribution was analyzed with varying unit weight characteristics and particle sizes. In addition, swell strains and compression indices were studied with varying unit weight of compacted specimens. It was observed that, in the case of samples compacted at 100 % MDUW, about 50 % of the pores were larger than 0.1 µm, and this value increased with reduction in unit weight. Current research is of practical importance, especially in the wake of microbial treatments for clayey soils where the passage of microbes depends on the pore size and more specifically pore throat size

Effect of Density on the Pore Size and Pore Volume of Expansive Clays

It is a well established fact that, both pore size and volume govern the density and particle size characteristics of any soil. For clayey soils, higher densities followed by lesser particle size result in low pore volumes. However, not many studies were conducted on how these pore characteristics alter with variations in density and particle size. This paper presents the results of a study conducted to understand the effect of compaction effort on the pore size and pore volume characteristics on two semi-arid expansive clays. These two clays selected represent soils with different degrees of expansivity, particle sizes and mineralogy. Mercury Intrusion Porosimetry tests were conducted to study the pore size characteristics at 100, 95, 90, 85, 80, 75 and 70% of maximum dry density (MDD) at corresponding optimum moisture content values. Both pore volume and pore size were analysed with varying density characteristcs and particle sizes. It was observed that in case of samples conducted at 100% MDD, about 50% of the pores were larger than 0.1 μm and this value increased with reduction in density. The current observations assume practical importance especially in the wake of microbial treatments for soils where the the passage of microbes depends on the pore size and more specifically pore throat size

Leachate studies on lime and portland cement treated expansive clays

Chemical stabilization of clays is widely accepted in many countries and was proved to be effective in mitigating the expansive behavior. Several cases are reported that described premature failures in clay subgrades after stabilization. The reasons for these failures could be the ineffectiveness of stabilizer dosage or due to loss of stabilizer from soil over a period of time due to rainfall infiltration. The main objective of the present research project was to study the cause of premature failures in stabilized clays. Four soils showing expansive behavior were selected for this study and were studied with different stabilizer dosages of Lime and Portland cement. Accelerated curing was adopted in the current research as it saves time and provides better results. Leachate apparatus, an experimental set up used to study the soil specimens for stabilizer loss and how it replicates the moisture inflow was used in this research. Calcium concentration, pH and Unconfined Compressive Strength (UCS) of the soil specimens were monitored thorough out the experiment. It was found out that stabilizer loss has not much impact on the stabilizer ineffectiveness of a treated soil