Assessment of Rocks competency for pre-foundation study using ultrasonic approach

Abstract

The aim of the current research is to use the ultrasonic wave velocity for assessment of rock competence for pre-foundation study at engineering site near Rawa city. Thirty seven (37) rock samples were gathered from different depths of well drilled at the site. Both compressional and shear waves velocity (Vp and Vs) were measured in the laboratory. To assess the competency of rocks as foundation materials, some geotechnical properties include Poisson’s ratio(σ), Effective angle of internal friction (ϕ), Material index(Im), and Coefficient of lateral earth pressure at rest (Ko) were calculated. The results of the study showed that the first layer characterized by incompetent to fairly competent materials, the second layer (Anah Formation) composed of alternation of the moderately competent (limestone) with thin incompetent (fractured coralline limestone) rocks, while the third layer (Baba Formation) which composed of dolamatic limestone characterized by good competent rocks. Depending on above mentioned results, the third layer (Baba Formation) is more suitable as foundation rocks for constructions purposes at the investigated site. The results also confirm that the ultrasonic wave velocity is effective method in evaluating the geotechnical properties of rock in pre-construction works.