GEOLOGICAL AND GEOTECHNICAL ASSESSMENT OF SELECTED GULLY SITES IN LAINDE FULANI AREA NE NIGERIA

Gabriel Ike Obiefuna,¹ Clement Ojodale Agbo,¹ and Danjuma Bawa²

¹Department of Geology, Modibbo Adama University of Technology, Yola, Nigeria

²Department of Urban and Regional Planning, Federal Polytechnic Mubi, Nigeria

Email: gobiefuna2000@mautech.edu.ng

ABSTRACT

The Geological and Geotechnical assessment of selected gully sites in Lainde-Fulani and environs is presented. Field geological study of the area revealed that the area is underlain by Basement Complex rocks. The soils of the area are products of in situ weathering of the underlying basement rocks.  Results of sieve analyses show that the soils at the gully sites have sorting values ranging between 0.42 and 2.3, coefficient of uniformity values ranging between 3.0 and10 , and coefficient of curvature values ranging between 0.2 and 1.3. These indicate that the soils are poorly to well sorted and well to poorly graded. The plasticity indices values ranges between 11.0 and 29 with a mean value of about 20 indicating moderate plasticity with slight dry strength and easily friable. Values of maximum dry density ranges between 1.83g/cm³ and 2.09g/cm³ at optimum moisture contents of between 7.4% and 11.3% revealing that the soils are generally loose. The hydraulic conductivity and transmissivity values as determined from statistical grain-size method ranges between 3.8×10^-4 cm/s to 6.4×10²cm/s and 3.8×10^-2cm²/sto 9.6×10⁴cm² respectively. These indicate moderate seepage fluxes and adverse pore pressures and are thus erodible. From the results of the study, recommendations for erosion control such as; afforestation, construction of drainages, grouting and concrete rip-raps were suggested.