Abstract
The Iva Valley area has one of the highest densities of landslides in Nigeria, and impacts the residents, local economy, and the environment. Slopes in the area sit on unconsolidated, cross-bedded, friable sandstone units with interbeds of claystone. Past research efforts had proposed theories explaining the mechanism of failure based on the limited-liquefaction behavior of the slope materials. But as landslide prevention works on the slopes began to fail, it became apparent that those theories were inadequate solutions to the devastating effect of mass wasting processes. This paper presents the results of landslide susceptibility assessment based on the new evidence of complete-liquefaction behavior observed in the samples when back-pressure is employed to accomplish full saturation. Loose, saturated specimens failed after attaining maximum strength at shear displacements less than 1 mm. The failure was marked by rapid reduction in shear strength and accompanied by a steady increase in pore water pressure until the ratio of pore pressure and normal stress approached unity indicating complete liquefaction. This behavior simulated the response of the slope soils to varying stress and drainage conditions in the field, and seems an adequate mechanism for the incessant failure of slopes and prevention works. Because the geology of a vast area of the South-East Nigeria is similar, the results obtained at the study area are also applicable in other areas within the region for sustainable preventive and mitigating measures.
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Acknowledgments
This research was conducted under the auspices of the International Program on Landslides (Project No. 150) supported by UNESCO, UNISDR, ISDR, and the Japanese Government. We deeply appreciate Professor Sassa Kyoji, founding president of the International Consortium on Landslides, and Professor Fawu Wang of the Department of Geosciences, Shimane University, Japan for their continuous support. The head and staff of the Department of Geology, University of Nigeria, Nsukka are acknowledged for their great role in the research.
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Igwe, O., Fukuoka, H. The effect of water-saturation on the stability of problematic slopes at the Iva Valley area, Southeast Nigeria. Arab J Geosci 8, 3223–3233 (2015). https://doi.org/10.1007/s12517-014-1398-7
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DOI: https://doi.org/10.1007/s12517-014-1398-7