Geotechnical and geomorphological investigation of rainfall induced shallow landslide at Okeigbo, Ondo State, southwestern Nigeria☆
| Autor: | Hakeem Oludare Adedeji, A. M. Gbadebo, Adedayo A. Badejo, Moyosoluwa Odunayo Adeyemi |
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| Rok vydání: | 2021 |
| Předmět: |
geography
geography.geographical_feature_category 010504 meteorology & atmospheric sciences Bedrock Geology Landslide 010502 geochemistry & geophysics 01 natural sciences Petrography Shear strength (soil) Soil water Cohesion (geology) Geotechnical engineering Direct shear test Slope stability analysis 0105 earth and related environmental sciences Earth-Surface Processes |
| Zdroj: | Journal of African Earth Sciences. 178:104163 |
| ISSN: | 1464-343X |
| Popis: | This study investigated the influence of geology, geomorphology, rainfall and land use on a recent landslide at Okeigbo. Samples of rocks and slope materials were collected during field investigation and were subjected to petrographic analysis and geotechnical tests respectively. Grain size analyses, shear strength analyses and permeability test were conducted on nine samples of disturbed slope materials site to classify the soil. Daily rainfall record for 2008, 2009, 2010, 2011 and 2013 were collected and analyzed using the rainfall duration-cumulation threshold method. Terrain and Land use analysis were carried out to evaluate the impact of landslide on the study area. Field mapping and petrographic studies showed that the bedrock were highly fractured and deformed quartzite schist with mineral composition of quartz (98%) and muscovite mica (2%). Grain size analysis showed that the residual soils consist of sand (80%), gravel (16%) and clays (4%) thus, classified as gravely sands. The coefficient of permeability derived for the soils vary between 0.01 and 1 m s − 1 indicating high permeability. Rainfall analysis showed that the landslide was triggered after a rainfall with duration of three days and total cumulation of 158 mm. The slope of the site ranged between 26.83 o and 6.73 o and the direct shear test showed that the disturbed soils had an average cohesion of 6.08 kPa and internal friction of 6.67 o which indicated poor structural and shearing strength making the soil susceptible to re-occurrence. The geomorphology of the area, nature of the slope materials, agricultural activities and rainfall were observed to have reduced the effective shear strength of the residual soils in the study area. |
| Databáze: | OpenAIRE |
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