An investigation on the strain accumulation of the lightly EICP-cemented sands under cyclic traffic loads

Industrial production of chemical cement leads to extreme emissions of greenhouse gases. Biological or bio-inspired sustainable materials for soil treatment projects can be employed instead of chemical cement to heal the carbon cycle in the ecosystem. The enzyme-induced calcite precipitation (EICP) method is one of the novel bio-inspired technologies that can be employed in soil treatment projects to increase desired properties of soils. While the monotonic and cyclic behavior of the enzymatically treated sands has been investigated comprehensively, the strain accumulation pattern in these improved soils under cyclic traffic loads has not been evaluated yet. In this paper, confined and unconfined cyclic compression tests are applied to the enzymatically lightly cemented sands, and the effects of the different parameters on their strain accumulation pattern are investigated for the first time in the literature. This study uses two types of specimens with unconfined compression strengths (UCS) equal to 42 ​kPa and 266 ​kPa. It is shown that the treated specimens have a rate-dependent behavior where cyclic loads with low frequencies lead to more resilient and plastic strains in the specimens. The results show that by approaching the maximum applied stresses to the UCS of the specimens (by breaking more calcite bonds between sand particles), the rate dependency behavior of specimens will reduce. Investigation of the effects of the cementation level demonstrated that by increasing the amount of the precipitated calcite from 0.38% to 0.83%, accumulated plastic strains are reduced almost 95% under the same loading condition. Effects of the initial static loads, confining pressures, the number of cycles, and amplitudes of the cyclic loads are also evaluated.