The Implication Of Subsoil Geology In Foundation Failure Using Geotechnical MethodsA Case Study Of Lagos Southwestern Nigeria

Building failure in Lagos has been persistent in recent time even though diverse possible sources have been emphasized. Regrettably the subsurface geology has rarely been given an attention even though it serves as base upon which these structures seat. This study focused on investigating the implication of the subsoil geology on the variation in the occurrence of foundation failure in Pen-Cinema Agege and Ogudu Kosofe local government area of Lagos using standard penetration test SPT and cone penetration test CPT. Boreholes were drilled and samples were collected and subjected to Atterberg test quick undrained triaxial test and Oedometer consolidation test. The result from the above test carried out showed that the Pen-Cinema is majorly underlain by very hard sandy silty lateritic clay with hard pans at the depth of 2.25m while Ogudu is underlain by dark grey stiff medium grained clayey sand at the depth of 13m. results from Ogudu on plastic limit was in the range of 20-40 liquid limit 40-70 and natural moisture content 25-30 while for Pen-Cinema plastic limit was in the range of 28-30 liquid limit 45-48 and natural moisture 17-19. Based on undrained triaxial test an allowable bearing capacity of 68.53KNm2 calculated for the CPT in Pen-Cinema while in Ogudu allowable bearing capacity of 10.96 KNm2 was calculated. However based on results from the above test carried out for any proposed structure in Ogudu pile foundation will be suitable for engineering structures while in Pen-Cinema raft foundation will be more preferable.