Geophysical Investigation of the Causes of Borehole Failure in the Crystaline Basement Complex: A Case Study of Kaura Area of Kaduna State, Nigeria

Thesis Abstract

Vertical Electrical Soundings (VES) using Schlumberger array were carried out at different points along five (5) profiles. This research investigates the causes of massive borehole failure at Kaura area of Kaduna state using the resistivity tomography techniques. Terrameter SAS300 is the instruments used to acquire the data. A total of 19 boreholes are functioning, while 31 boreholes are non-functioning within the area. The investigation has portrayed the possible factors which are most probably causative to borehole failures in the area which involves the design and construction, groundwater potential/hydrogeological factors and operational and maintenance factors. It was found out that it is possible for one factor to lead to the other. For example, a borehole poorly designed, constructed and completed could result in sand/clay pumping and eventually affect the rubber seals in the hand pumps or the impellers in the case of submersible pumps. The boreholes tap the weathered and fractured basement aquifers of the area with yields ranging from 2 litre/min to 20 litre/min. However, yields from Sandy soil aquifers were found to be extensive. The survey shows that boreholes with initial recorded yield less than 10 litre/min have failed over time. The survey reveals that the areas where wells and boreholes are drilled through sandy soil and fracture zones have sustainable aquifers for groundwater exploitation, while boreholes that are constructed through clayey formation usually fail.