Laboratory Investigations on the Effectiveness of Bio-Enzyme on the Strength of Cement or Lime Treated High Liquid Limit Soil

This paper performs the strength properties of bio-enzyme improved high liquid limit soil (HLLS) treated with 4% (by weight) content of cement or lime cured for 28 days. A series of consolidated undrained (CU) triaxial tests and unconfined compressive (UC) strength tests were conducted on plain soil (untreated by cement or lime), cement-treated and lime-treated HLLS specimens improved with different bio-enzyme content (i.e., 0%, 0.2%, 0.4%, 0.6% and 0.8% by weight) to investigate the effect of bio-enzyme content on the strength properties of tested soil. The results indicate that the stress-strain relationship of bio-enzyme improved plain soil specimens exhibit strain-hardening behavior and ductile failure mode. The other specimens exhibit strain-softening behavior and brittle failure mode. Adding 0.6% bio-enzyme, the values of undrained shear strength of CS specimens are about 1.7 times, 1.8 times, and 1.9 times of LS specimens at σ₃ = 100 kPa, 200 kPa and 300 kPa. The residual strength is about 40.5% on average the peak strength for CS specimens, and 37.0% for LS specimens. The cohesion c increased 258.6% and 220.7%, and the internal friction angle φ increased 38.57% and 39.05% for CS and LS specimens respectively. The UC strength of CS specimen is 1.69 times that of LS specimen. The magnitudes of CU strength, UC strength, cohesion and internal friction angle of three types of soil specimens followed the same increase trend when the bio-enzyme content increased from 0 to 0.6%, and peak values can be observed at 0.6% bio-enzyme content. The use of bio-enzyme to improve the strength behavior of HLLS treated with cement or lime is an innovative and attractive solution in geotechnical engineering.