Abstract: For the purpose of improving the strength and stability of soft soil, studying the effects and mechanical properties of fibre reinforced soil; the polypropylene fibre has been chosen as the reinforcement material of soft soil. Therefore, in the present investigation, fibre was randomly included in to the raw soil, lime soil (with 5 % and 8 % lime content) and cement soil (with 5% and 8% cement content) at three different mass percentages of fibre content, i.e.0.05,0.15 and 0.25 %.Twenty groups of samples were prepared at different percentages of fibre, lime and cement and were subjected to the unconfined compression test; the main objective of this investigation had been focused on the effect and strength mechanism of the soil reinforced with randomly included fibre. The test results have clearly shown that increasing the fibre content resulted in a small increase in the unconfined compressive strength of raw soil; while the inclusion of little fibre dramatically enhanced the unconfined compressive strength of lime soil and cement soil, the brittle characteristic was weakened and the stability in water was improved with the addition of fibre in lime and cement soil.

Key words: soft soil, fibre, reinforcement, lime soil, cement soil, strength