Enhancing geotechnical zoning through near-surface geophysical surveys: a case study from eastern Agadir, Morocco

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中文题名通过近地表地球物理调查加强岩土分区:摩洛哥阿加迪尔东部的案例研究
作者Ismaail Khadrouf
作者单位Hassan II University,Morocco
刊名Mediterranean Geoscience Reviews
2024
6
03
摘要
The eastern Agadir (Morocco) was selected for the urban expansion. However, it faces challenges owing to its location within an alluvial basin of weak and heterogeneous sediments, compounded by the scarcity of geotechnical data. This study aimed to create the first geotechnical zoning map of the area to support informed urban planning. Geophysical surveys were employed with available in situ investigations to address this data gap and delineate and characterize the main geotechnical zones. The electrical resistivity tomography (ERT) method was used to map the soil distribution horizontally and vertically, complemented by laboratory tests. The multichannel analysis of surface waves (MASW) and seismic refraction tomography (SRT) methods provided insights into important geotechnical and elastic-dynamic parameters. This analysis revealed three distinct geoseismic layers. The surface layer consisted of sand, silt, pebble, weathered limestone, and marlstone, whereas the underlying layer contained compacted silt, dense sand, conglomerate, sandstone, limestone, and marlstone. This layer exhibited higher seismic velocities and lower soil heterogeneity than the surface layer. The third layer, characterized by limestone, marlstone, and compacted deposits, serves as geotechnical bedrock. The VS30 velocities were calculated and classified according to the EUROCODE 8 scheme, which categorizes sites based on their geological characteristics and associated seismic risks. The study area was divided into Class A (rock), Class B (dense soil and soft rock), and Class C (medium dense sand and gravel). This classification is essential for assessing seismic response and designing earthquake-resistant structures. The majority of the sites were categorized as Class B. The final zoning map reveals five distinct geotechnical zones: Tagragra's Dome, the alluvial fans and floodplain, the alluvial terrace, the limestone plateau, and the sand dune zone. The calculated parameters revealed soil heterogeneities in horizontal and vertical directions. These results provide valuable key parameters for informed urban planning, with special attention paid to areas with weak soil during foundation design.

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