Subsurface Engineering Geological Investigation and Prediction of Axial Pile Capacities for the Design and Construction of Deep Foundations in the Calabar River Channel, Nigeria

Abstract

Pile foundation was proposed to support a 444.8kN loading jetty in the shoreline of the river channel. To determine the pile bearing capacities, engineering geological investigation involving the boring of 6 geotechnical boreholes to a depth of 30m, sampling, in situ standard penetration test and laboratory analysis were carried out. Foundation subsoil profile depicted low shear strength, intermediate plasticity (CI) inorganic clays to high plasticity organic clays (CH) of soft to medium consistency with high compressibility, and medium to high swell potential. 3.7% of the specimens were of intermediate plasticity while 96.3% were of high plasticity. 3.7% were of medium swell potential, 7.4% of high swell potential while 88.9% were of very high potential class. On the basis of consistency limits, 48.15% of the clays are Ca - montmorilonite, 29.63% Illite while 14.81% were Kaolinitic clays. The sand layers were of medium density, medium to coarse grained size fractions occurs to 30.0m with clay interval ranging from 13.0 to 17.5m in thickness. The top clay layer's pile capacity varies from 29kN at 1.5m increasing linearly to 288kN at 15.0m in sand for the 406mm diameter tubular steel pile. The clay layer within a depth range of 16.5m and 18.0m recorded a decrease in pile capacity. The trend of variation in pile capacity was similar for all pile diameters (508mm- 900mm). The largest pile diameter (900mm) depicted a pile capacity of 76kN at 1.6m depth and 3311kN at 30m. Pile under reamed bulbs are recommended for placement in the stable, medium to coarse grained, medium density and stiff to very stiff sand layers and pile installation should commence from the centre towards the edges. Pile interval should be determined to limit drainage effects.

Publication Info:

Author: Abija, F.A. , Oboho, E.O. ,Edet, A. and Esu,E.O.

Volume: 57

Issue: March

Published By: Journal of Mining and Geology, 2024-03-01