Study of the law of strength attenuation and microstructure damage to cement improved loess under acid rain erosion

Abstract

This study examines how acid rain affects the microstructure and mechanical properties of cement-amended loess, crucial for ensuring the safety of engineering projects. We aimed to investigate how acid rain influences the micro-mechanical behavior of cement-amended loess and its damage characteristics under combined acid rain and loading conditions. Cement-amended loess samples were exposed to artificial acid rain with varying pH levels, and changes in their strength and microstructure were analyzed using unconfined compression tests, SEM, NMR, and XRD techniques. Our findings reveal that acid rain erosion of cement-amended loess triggers hydration and erosion reactions. As acid rain concentration increases, the unconfined compressive strength of the amended soil gradually decreases, accompanied by an expansion of pore spaces from small to large-medium pores. Additionally, particle contacts shift from face-to-face and side-to-side to point-to-point and side-to-side configurations. Furthermore, prolonged erosion time exacerbates pore space expansion, indicating a time-dependent effect on soil integrity. To characterize these effects, we developed a constitutive equation within the framework of damage mechanics that incorporates both erosion and loading. This equation successfully aligns with experimental data, providing a comprehensive understanding of the coupled effects of acid rain erosion and mechanical loading on cement-amended loess. These insights are pivotal for designing resilient engineering solutions in environments prone to acid rain erosion.