Application of 2D electrical resistivity imaging and coneudpenetration test (CPT) to assess the harzadous effect of nearudsurface water on foundations in Lagos Nigeria

摘要

Adequate information on the condition of the subsurface is very important for siteudevaluation for engineering purposes. In this study two dimensional (2D) geoelectricaludresistivity survey and cone penetration tests were conducted to study the hazardous effect ofudexcess near surface water on the foundation of building in a reclaimed land located at VictoriaudIsland area of Lagos State. The results of the inverted 2D geoelectrical resistivity data revealedudthree distinct geoelectrical layers characterized by low to moderate electrical resistivity of 2.23udand 129 Ωm and 9.46 to 636 Ωm respectively. The topsoil is characterized by wet sandy soil,udwhich is underlain by sandy clay and banded at the below by a geologic formation of lowudresistivity which is suspected to be clay. The clay material may be responsible for the excessudwater retention observed in the area. The CPT method on the other hand revealed a geologicaludformation of low resistance to penetration between 2-3 kg/cm2 from the topsoil to a depth of 7udm, which may be the effect of excess water in the near surface. This study revealed that theudfoundation of building may not be founded directly on the soil in any reclaimed land as thisudmay result in collapse as a result of upward migration of water to the near surface