Geomechanical Characteristics of Micaceous Sand under Static and Repeated Loading Conditions

The geomechanical characteristics of sand are adversely affected by the presence of mica due to its resilient and rebound nature and crushing upon repeated loading. This behavior of micaceous sand triggers major challenges in highway applications exposed to repeated traffic loading. This study consisted of a series of geotechnical experiments for evaluating the influence of mica particle breakage on the macroscopic response such as compaction, permeability, compressibility, and shear strength properties of micaceous sand. Micaceous sand specimens were subjected to repeated impact loading simulated using the standard Proctor compaction test procedure to obtain precrushed samples with different degree of crushing. The study also included cyclic California bearing ratio (CBR) (cCBR) loading tests to evaluate the resilient modulus variation in micaceous sand at different degrees of crushing. Additionally, micro X-ray computed tomography (X-ray CT), scanning electron microscopy (SEM), and particle-size distribution analyses were conducted to investigate the microscopic alterations within the soil matrix and their macroscopic implications. The presence of uncrushed mica particles in micaceous sand resulted in more nonuniform void spaces, contributing to low density, high compressibility, and low shear strength. The gradual crushing of mica reduced mica bridges and decreased the resilient nature, which in turn initiated the pore-filling phenomenon, leading to increased density, improved shear strength, and compressibility. However, shear strength was reduced due to increased nonplastic fines content at the highest degrees of crushing as a result of breaking of coarser mica to numerous smaller mica particles. The uncrushed micaceous sand had a low resilient modulus (Mr), whereas the highly crushed soil had the highest Mr, indicating the reduced detrimental resilient nature of crushed mica particles.