Subsoil Bearing Capacity from Load Test Results In Two Locations in Rivers State, Nigeria

Vertical pile load tests using the maintained load test and twice the safe working load (SWL) were used in two different locations (A & B) in Rivers State. Four pre-cast concrete piles of dimension 400mm by 400mm were tested using Kentledge method in location A while three cased piles of 406mm diameter were tested in location B using reaction method. The range of pile head movement (settlement) at maximum load of 1000KN (200% of SWL) was 2.76mm 5.73mm while the range of 10% of the pile width was 11.04mm 22.92mm. The elastic rebound varies from 80.49% 97.65%. In location B, where reaction method was employed, the cumulative settlement at maximum load of 544.4KN was between 1.088mm and 5.70mm while the range of 10% of the pile width was 8.16mm 23.142mm. The elastic rebound varied from 39.20% 66.83%. The soil bearing capacity values at depth of 15.0m ranged from 570KN/m 2 710KN/m 2 while the pile bearing capacity at depth of 12.0m was 6350KN/m 2 in location A. A pile bearing capacity of 4188KN/m 2 and pile allowable load of between 361KN and 2275KN were respectively recorded at depth of 30m in location B. The pile bearing capacity was greater than soil bearing capacity. Results showed that the piles did not fail the test in both locations since cumulative settlements were much lower than 10% of the pile width. This could be due to factors like skin friction of the piles, elasticity, stiffness and pore water pressure of the soil. Therefore, test piles are capable of withstanding anticipated imposed stress from the super structure without failure. The Kentledge system produced greater influence on the test piles probably because weight used was higher than the safe load capacity of the test pile for safety consideration. The Kentledge weight increased the pile –soil interaction by increasing the unit shaft resistance of the piles. This could probably account for the high values of elastic rebound in location A. Insufficient time interval between driving and testing affected the elastic rebound values of test piles in location B. This is because piles in cohesive soil should be tested after sufficient time has elapsed for excess pore water to dissipate.