Mineralogical, Geotechnical Characterization and Stability of the Cut Slopes of Widikum and its Surroundings (North-West Cameroon)

Oscar Rodrigue Michel Kenmoe,Armand Sylvain Ludovic Wouatong,Francois Ngapgue,Valentine Katte Yato

doi:10.5539/esr.v8n1p1

Abstract

The Widikum highlands and its surroundings are located in the North West Region of Cameroon. These five last years, landslides are frequently affecting movement on this portion of the highway. An investigation for understanding the mechanism of these phenomena was recently performed to clarify and to propose suitable remediable solutions. The study included mineralogical and geotechnical characterization of the local soil materials. The X-ray diffraction mineralogical analysis on clay fractions reveals the presence of phyllitic minerals (kaolinite, gibbsite, montmorillonite, illite and biotite). Associated minerals are mainly represented by quartz. Montmorillonite has the small crystal and largest surface which aid in increasing its adsorptive capacity. Clayed minerals can cause swelling and consequently the change or variation of the mechanical characteristics of the materials. The natural water content of weathered products vary from 27 to 47.4% which are close or even lower than the liquid limit included between 59.4 and 71.9%, this justify their unstable character. In addition, the high plasticity index ranges between 17.9 and 29.3% and is indicative of plastic materials thus very sensitive to creep. Moreover, the saturation ratio is very high (60 - 96%) thus attesting to their quasi saturated state. It is advisable to reduce the height of the steps to 2.3m by opting for a bench of 3m and adopting an inclination angle of β = 37.5°. Building retaining structures as well as eucalyptus and vertiva grass planting is recommended to reduce landslide incidences.

Highlights

The Cameroon Volcanic Line, direction N30°E and 1600 km long, forms a series of horst and graben, comprising the Bamenda Mountains and it is marked by a succession of volcanic, plutonic and metamorphic formations resting on the crystalline base subject to intensive weathering
The main objective of this study is to analyze the stability of Widikum and its surroundings cut slopes by means of the mineralogical and geotechnical studies and to propose suitable remediable solutions
Three localities namely Fifty One, Ofen Tiben and Ogwei Tiben were affected by landslides

Summary

Introduction

The Cameroon Volcanic Line, direction N30°E and 1600 km long, forms a series of horst and graben, comprising the Bamenda Mountains and it is marked by a succession of volcanic, plutonic and metamorphic formations resting on the crystalline base subject to intensive weathering These are dominated by three great geomorphological units varying between 250 and 1550 m laid out in successive steps and separated by more marked escarpments (steep slopes greater than 45°) favorable to instabilities. Landslides represent a major threat to human life, constructed facilities, and infrastructure in most mountainous regions of the world (Delmas et al 1987; Lulseged et al 2005; Zangmo et al 2009; Kouayep et al 2009) They are controlled by diversity of factors such as substratum composition, geotechnical parameters of the whole lithological and pedological set up, climatic conditions, geometry and geomorphology of the site (Delmas et al 1987). That of Kekem, on the night of October 20, 2007 killed one person esr.ccsenet.org

Objectives

Methods

Results

Discussion

Conclusion