Study on the Strength Properties and Micromechanisms of Nano-Al 2 O 3 -Modified Predisintegrated Carbonaceous Mudstone Based on Orthogonal Design

Abstract

This study aims to improve the mechanical properties of predisintegrated carbonaceous mudstone (PCM) used as an embankment fill. The four factors used in the orthogonal design test are nano-Al 2 O 3 content, cement content, water content and compaction. Afterward, the strength characteristics and micromechanisms of PCM modified by nano-Al 2 O 3 and cement are studied through triaxial compression tests, X-ray diffraction analysis and SEM observations. The results show that the failure mode of PCM changes from bulging failure to shear failure when the nano-Al 2 O 3 and cement contents are increased. The order in which the factors affected the cohesion of PCM is cement content, nano-Al 2 O 3 content, water content and compaction. At a given cement content, the cohesion of PCM with an optimal compaction of 96% and a water content of 8% increases and then decreases with increasing nano-Al 2 O 3 content. The increase in the internal friction angle is proportional to the nano-Al 2 O 3 content when the cement content is between 0 and 4%. Controlling the contents of nano-Al 2 O 3 and cement to 0.3% and 8% results in a synergistic effect of both materials on shear strength. Nano-Al 2 O 3 improves the cohesion and friction strength of PCM through accelerating the hydration of cement and optimizing the structure of hydration products.