Deciphering near-surface architecture and landslide triggers in granitic environments: A regression-driven multiphysics modeling framework for geoengineering integrity

Abstract

In crystalline basement terrains, understanding near-surface crustal architecture is vital for assessing geoengineering integrity and mitigating landslide risks. This study focuses on the granitic terrain of Penang Island, Malaysia, where rapid urbanization and landslides could threaten infrastructure stability. Integrating multiphysics with statistically optimized borehole-based rock quality designation (RQD) modeling provides the first geophysical–geotechnical–statistical framework to evaluate lithological conditions and landslide triggers in granitic terrains. The innovative methodology develops lithology-based geoengineering integrity models to assess soil–rock profiles at steep and low-lying sections across four sites: Sungai Ara (east; Site 1), Batu Maung (south; Site 2), Jelutong (north; Site 3), and Balik Pulau (west; Site 4). The findings identify varied subsurface characteristics using resistivity and seismic P-wave velocity tomographic models, correlated with borehole logs and RQD data. The subsurface is categorized into residual soils, highly to moderately weathered/fractured granite, and hard/fresh granitic bedrock. The study framework revealed contrasting lithologic differentiation between southern Penang Island and the northern section, including the western and eastern parts, likely due to differences in granitic feldspar magma mineralogy and susceptibility to weathering. Sites 1, 3, and 4 are dominated by lower resistivity and seismic velocity values—indicating weaker, looser, and deeper weathered materials—whereas Site 2 is characterized by more compact, sandy-rich residual soils and hard/fresh bedrock with deeper fractures. Weathered and fractured zones amplify water–rock interactions, increasing pore pressure and landslide susceptibility in the area. Contractive clay/silt (<200 Ωm) and water-escape structures within creeping residual soils are identified as primary landslide triggers, particularly in unstable, steep sections. For infrastructure design integrity, reinforced piling foundations reaching fresh granitic bedrock (RQD Units III and IV) are recommended. These measures are crucial in Penang's rapidly urbanizing terrain with numerous tall buildings. While site-specific, the study introduces a globally adaptable framework for cost-effective, large-scale geoengineering assessments in similar geological contexts, enhancing risk mitigation and infrastructure design strategies.