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