Detailed field surveys and geotechnical evaluation of soils in Iguosa and its environs, Southern Nigeria, were undertaken to determine the root causes, mechanisms, and impacts of landslides and gully erosion. This was done to suggest appropriate mitigation measures to reclaim the affected land and prevent future occurrences in the study area. Field study revealed high elevations, a steep slope, high rainfall and inadequate drainage systems. Also, human activities and socio-cultural activities have contributed to the large lateral extents in depths and widths of the landslides and gullies in the study area. The geotechnical analyses reveal that soil samples from SB1, SB2, SB6 and SB7 lithological units are mainly sandy clay with a coefficient of permeability ranging from 3.5 × 10−4 to 4.2 × 10−4 cm/s, the cohesion ranges from 27 to 28 kƿa and angle of internal resistance ranges from 27° to 30° respectively. The plastic limit ranges from 2 to 4, and liquid limit ranges from 33 to 38, and the plasticity index ranges from 30 to 36. Ajali sand units SB3, SB4, SB8 and SB9, consist of coarse-grained sand with no plasticity. The coefficient of permeability ranges from 2.8 × 10−4 to 3.2 × 10−4 cm/s, the cohesion range from 10 to 18 kƿa, angle of internal resistance 24° to 26°, respectively. The soil samples from SB5 and SB10 lithological units are silty-clay with a coefficient of permeability of 4.6 × 10−4 to 4.8 × 10−4 cm/s. The cohesion of 45 to 46 kƿa, and angle of internal resistance of 37° to 40°, respectively. The plastic limits ranges from 35 to 36, and liquid limit is 76, and the plasticity index ranges from 40 to 41. Field survey and geotechnical evaluations of the soils revealed that high elevation, a steep slope and the geotechnical properties of the soils were the initial conditions that initiated landslides and gully developments in the study area. This has also been influenced by rainfall, poor vegetation, inadequate drainage systems, and human activities as well as socio-cultural activities. Over four hundred and thirty-two houses and farmlands and other properties have been damaged and abandoned in the study area. Covering the landslide areas with impermeable layers/materials, diverting surface water away from the landslide areas, enacting laws to prevent the erection of structures on landslide prone-areas, sound drainage systems, the use of biotechnical slope and bioengineering methods, afforestation and re-vegetation were the proposed mitigation measures to tackle this menace in the study area.

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尼日利亚南部伊戈萨及其周边地区沟壑侵蚀和滑坡材料的岩土工程评价及其影响

对尼日利亚南部伊戈萨及其周边地区的土壤进行了详细的实地调查和岩土工程评估，以确定滑坡和沟壑侵蚀的根本原因、机制和影响。这样做是为了建议适当的缓解措施，以开垦受影响的土地并防止研究区未来发生此类事件。实地研究显示海拔高、坡度陡、降雨量大且排水系统不足。此外，人类活动和社会文化活动导致了研究区滑坡和沟壑的横向深度和宽度较大。岩土分析表明，SB1、SB2、SB6和SB7岩性单元的土样以砂质粘土为主，渗透系数为3.5×10-4～4.2×10-4 cm/s，内聚力的范围分别为27至28 kƿa和内阻角的范围分别为27°至30°。塑限范围为2～4，液限范围为33～38，塑性指数范围为30～36。Ajali砂单元SB3、SB4、SB8和SB9由粗粒砂组成，无塑性。渗透系数范围为2.8×10−4～3.2×10−4 cm/s，内聚力范围为10～18 kƿa，内阻角分别为24°～26°。SB5和SB10岩性单元土样为粉质粘土，渗透系数为4.6×10-4～4.8×10-4 cm/s。内聚力为 45 至 46 kƿa，内阻角分别为 37°至 40°。塑限35～36，液限76，塑性指数40～41。对土壤的实地调查和岩土工程评估表明，高海拔、陡坡和土壤的岩土特性是导致研究区滑坡和沟壑发展的初始条件。这也受到降雨、植被贫乏、排水系统不足、人类活动以及社会文化活动的影响。研究区内有超过四百三十二处房屋、农田和其他财产遭到破坏和遗弃。用不透水层/材料覆盖滑坡区，将地表水从滑坡区引开，制定法律以防止在滑坡易发区建造建筑物，健全排水系统，使用生物技术斜坡和生物工程方法，