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

Abstract

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

Research on Nanoeffect of Penetration and Consolidation under Nonlinear Characteristics of Saturated Soft Clay

“…M. Kotilek summarized 12 kinds of NON-Darcy V-I relations and believed that the experimental method and errors in the experimental process were the main reasons for the deviation of the seepage law from Darcy's law. Zhang Zhong explained the deviation phenomenon from the perspective of bound water and believed that the non-Darcy seepage in clay was due to the non-Newtonian behavior of pore water [ 7 ]. L. Erge believed that whether Darcy's law applies to clay should be further discussed [ 8 ].…”

State-of-the-Art Review of the Applicability and Challenges of Microbial-Induced Calcite Precipitation (MICP) and Enzyme-Induced Calcite Precipitation (EICP) Techniques for Geotechnical and Geoenvironmental Applications

“…Chittoori et al tested the effect of porosity, consolidation, and the unit weight of expansive clays. Their study was important in the wake of soil treatment with microbes because pore size and size of pore throat play important roles in microbial treatment [118]. Figure 4 shows the maximum reduction of permeability in percentage achieved by different researchers in their studies after the biomineralization of soils.…”

Microbial-Facilitated Calcium Carbonate Precipitation as a Shallow Stabilization Alternative for Expansive Soil Treatment

“…There are very few studies that explored the application of MICP in expansive soils. To test the hypothesis that the low pore space in these soils is not compatible for MICP application, Chittoori et al [27] performed a mercury intrusion porosimetry (MIP) study on two expansive soils to observe the pore size and pore volume at different compaction levels. It was found that 30% to 50% of the pore volume was larger than 1.5 µm (the average cell size of typical urease-producing soil bacteria) at the MDUW [27].…”

“…The presence of urea works as a nitrogen source, and the increase in the pH level as a result of the presence of ammonium from urea hydrolysis creates an environment for bacteria that can survive in a high-pH environment and use urea or ammonia as a nitrogen source [14]. As the number of ureolytic bacteria increases, the rate of hydrolysis increases, which increases the rate of precipitation [27].…”

“…In this research, two types of cementation solutions were used. In the cementation solution, the concentration of calcium chloride is 250 mM, and in another cementation composition, the concentration of calcium chloride is 500 mM [27]. Two concentrations of calcium chloride were used to observe the effect of the concentration of calcium chloride in calcium carbonate precipitation.…”