A Study of Underpinning Methods Used in the Construction Industry in Nigeria

------------------------------------------------------ABSTRACT---------------------------------------------------Foundation and retaining wall failures account for the highest case of structural failures. This is a report on a study of underpinning methods used in the construction industry in Nigeria. In view of the fact that underpinning, just like most engineering decisions, there is no unique solution, the research investigated technique of remedying foundation defects and whether there are innovations as regards to the underpinning methods used in Nigeria. To achieve the desired objective structured questionnaire, oral interviews and case study of an ongoing underpinning work were carried out. Result shows that differential settlement with a mean of 2.28 is the most frequent cause of foundation failure. While the continuous strip and reinforced mat with mean of 2.7 and 2.67 respectively, are most frequently used underpinning methods in Nigerian construction industry. Also 81.3% of the respondents agree that underpinning methods adopted are suitable and effective. Professionals in Nigeria have devised unique method of underpinning. It was recommended that proper and adequate site investigation should be carried out. Heavy penalties and sanctions should be meted on those construction firms that employ quack professionals.