A sustainable solution to stabilise the expansive soil over cement stabilisation is needed to avoid the negative environmental impact. Therefore, in this study, two biopolymers (such as xanthan gum and guar gum) were used to stabilise the expansive soil, and the study focused on the impact of curing (field and laboratory curing) conditions on the performance of biopolymer stabilisation. The compressive strength results showed that the treated sample achieved a higher strength up to 4.18 times with XG than the untreated soil sample strength with 28 days of curing (in FC) with 1.5% of the weight of the soil sample with both biopolymers. Conversely, the sample cured in LC was observed to have a very low strength increment, and the gained strength was lost with the curing period from 7 days to 28 days. The possible reason behind this phenomenon is that in moist conditions, the biopolymer presence in the hydrogel form reduces the soil particle interaction, and it is also due to the breakage of the soil-biopolymer matrix. The swelling pressure of the soil was significantly reduced compared to untreated soil. The microstructural and element composition analysis confirmed that the biopolymer treatment is not involved in any cementitious reaction.

Expansive soils, when wetted, exert swell pressure on the structures built over them, often leading to damage. To quantify this additional pressure, researchers have often measured the vertical and lateral swell pressure. However, when expansive soils surround the structures in all directions, measuring the all-round swell pressure becomes more appropriate. In this context, an Isotropic - Pressure Monitoring Device (I-PMD) was employed in the present study for the measurement of all-round swell pressure for the soils C1, C2, C3, and C4 by wetting them from different initial states at constant volume conditions and was observed to be in the range of 20 kPa to 850 kPa. Also, comparative studies have been performed to comprehend the significance of all-round swell pressure measurement over conventional methods. Additionally, a relationship was proposed to predict the all-round swell pressure of the soil based on its vertical swell pressure measured by conventional methods.

The volumetric instability of expansive soils caused by moisture variations often leads to catastrophic consequences, including geohazards, structural damage, and high repair costs. The situation becomes more intricate when expansive soils are subjected to the chemical composition present in the fluid. This study investigates the chemical effects on the swelling and mechanical properties of expansive soil through comprehensive experiments. The results indicate that chemical effects inhibit swelling deformation and pressure, while saline solutions enhance effective stress and shear strength, evidenced by upward shifts in the strength envelope. Notably, the chemical influence on bentonite exhibits a threshold around 0.5 mol/L NaCl solution; below this threshold, soil properties change significantly with increasing solution concentration, whereas beyond it, the impact diminishes. Additionally, this study considers the effects of infiltration methods, initial moisture content, and shearing rate on shear strength. Different infiltration methods result in similar maximum volume variation and swelling pressure despite varied duration curves, with double infiltration reacting the fastest, top infiltration reacting slower, and bottom infiltration reacting the slowest. For soil samples with identical solutions, low initial moisture content causes notable strain softening and peak shear strength, while higher moisture reduces strain softening and peak strength. Under the same conditions, rapid shearing leads to higher shear strength.

Highly susceptible to moisture changes, expansive soils are widely recognized as problematic soils. Swelling-induced damages to overlying engineering structures result in financial loss and billions of dollars in repair costs annually worldwide. Therefore, to mitigate swelling potential, various soil amendment approaches have been investigated to date. Sustainable soil treatment techniques such as microbially induced carbonate precipitation, although enjoying a low CO2 footprint, suffer from challenges pertinent to the use of living microorganisms at field scale treatments. Hence, the current study aims to explore the feasibility and efficiency of using enzyme-induced calcium carbonate precipitation (EICP) as an alternative eco-friendly method, yet to be examined for improving swelling characteristics of clayey soil. For this purpose, a series of laboratory experiments from macro- to microstructural scales involving free swell tests, swell pressure, pH measurement, X-ray powder diffraction, Bernard calcimeter, confocal Raman spectroscopy, and scanning electron microscopy have been conducted on the EICP-treated expansive samples. The experimental program focuses on the influence of constituent concentrations used in the EICP treatment on the swelling potential to obtain the optimal EICP solution. The study reveals that EICP can result in more than 60% reduction in the free swell index compared to untreated soil conditions. The results indicate that the EICP technique can double calcium carbonate content within expansive soil, increasing it by as much as 220%. Finally, it is demonstrated that there is a strong correlation between the amount of precipitated calcite and enhancement in the free swell index.

Expansive soils are found to be susceptible for seasonal moisture fluctuations and will undergo cyclic swell-shrink movements causing stability concerns for all the civil engineering structures which are being constructed on these soils, and particularly the lightly loaded constructions like single storied dwellings, canal linings, pavements, etc. The swelling behaviour of these soils is generally characterized either by the mobilized swelling pressure under constant volume condition or by an increase in volume with the release of swell pressure. The researchers all over the world have made efforts in developing some remedial solutions to control or reduce the potential damages by these problems. The use of recently suggested technique of piled footings and its extension to pavements resting on expansive soils is explored by conducting field investigations within N.I.T. Warangal campus. The present work deals with studying the efficiency of tension piles (granular anchor piles and concrete piles) in reducing the swell-shrink movements of model footings and pavement panels resting on these soils. For this purpose, field studies were made by constructing 13 numbers of square footings with varied dimensions (1, 1.5 and 2 m side) and 5 numbers of square pavement panels of 3.0 m side with and without these tension piles. The swell-shrink movements of all treated footings and pavement panels were compared with those untreated ones for evaluating the efficiency in reducing the swell potential of these footings and pavement panels. The maximum heave of footings and pavement panels provided with granular anchor piles reduces by about 91%, and it reduces by about 75% when they were provided with concrete piles.