Browsing by Author "Agarwal, Brijesh Kumar"

Compacted expansive soil undergoes swelling and shrinkage during seasonal moisture fluctuations and causes distress to highway and railway structures built over them. Shrinkage of expansive soil is accompanied by the development of large desiccation cracks. The present research work is focused on studying the effect of different degrees of relative compaction on the desiccation cracking of soil. Different specimens were made using static compaction having different compaction states simulating the compaction process adopted in the construction of highway and railway embankments. The digital image analysis technique was used to quantify the crack propagation using ImageJ software. Desiccation cracks were quantified based on various crack parameters such as crack area, crack length, crack width, and crack intensity factor. Specimens with higher relative compaction exhibited reduced evaporation rates causing the delayed cracking response. A series of wetting-drying tests were also conducted to study the effect of wetting-drying cycles on the desiccation cracking response of specimens compacted at different relative compaction. Only a few cracks were observed during the compaction drying stage, followed by a large number of cracks on the application of the first wettingdrying cycle. However, the crack pattern remained almost similar in further wetting-drying cycles.

Combustion of coal in thermal power plants results in the generation of large quantities of ash. The finer ash (< 45 microns) is utilized by cement industries. The remaining portion along with the bottom ash is transported to the ash pond (disposal site) in the form of slurry. This disposed pond ash being a waste material needs to be utilized in raising dykes around the ash pond. However, pond ash being highly prone to liquefaction may cause catastrophic failures if used without treatment. The present study investigates the efficiency of commercially available bentonite in the mitigation of the liquefaction issues of compacted pond ash for ash dyke construction. Bentonite was used in small dosages (0%, 2.5%, 5%, 7.5%, and 10%) to treat the pond ash. Strain-controlled cyclic simple shear (CSS) tests were performed to study the effect of bentonite treatment on liquefaction behavior and dynamic properties of compacted pond ash. The hysteresis response of bentonite-treated pond ash showed higher cyclic strength than the untreated pond ash. The untreated pond ash specimens showed cyclic liquefaction in only 12 loading cycles. However, the bentonite-treated specimens showed a delayed pore pressure evolution and higher liquefaction resistance. The average shear modulus increased and the cyclic degradation parameter decreased linearly with an increase in the percentage of bentonite. Considering the liquefaction, cyclic instability, and dynamic characteristics; it was concluded that the addition of bentonite in small percentages (between 5% to 10%) could provide significant liquefaction resistance and high stiffness to the compacted pond ash under cyclic loading conditions.