Influence of Strain Rate on Unconfined Compressive Strength of Bentonite and Sand Mixes

Abstract

Sand is a pervious material in nature, and bentonite has highly swelling and shrinkage property. Compacted layers of bentonite and sand mixes have been used in a variety of geotechnical structures. The objective of this paper is to investigate the strain rate effect on unconfined compressive strength (UCS) of compacted bentonite and sand (B:S) mixes. For this, bentonite of different proportions was mixed with 60, 70, 80 and 90% sand and the UCS of all the mixes with varying strain rate was determined. Three different strain rates—2 mm/min (fastest), 1.75 mm/min (medium) and 1.5 mm/min (slowest) were used in this study. Results indicate that for all the B:S mixes, the UCS increases gradually with increasing strain rate. The highest increase in UCS due to an increase in strain rate was observed for the mix B:S = 40:60. For all the strain rates, the UCS of B:S mixes increases gradually up to a bentonite content of 30% and further increase in bentonite content reduces the UCS of the mixes. Therefore, mix B:S = 30:70 can be considered as the optimum mix. The UCS of the mix B:S = 30:70 was found to be maximum when the highest strain rate of 2.00 mm/min was applied.