A Comparison of Dynamic and Static Pile Test Results

Abstract

Abstract Class A predictions of static pile capacity for three projects are presented. Pile driving is monitored using strain transducers and accelerometers attached near the pile top. The CAse Pile Wave Analysis Program (CAPWAP) is used to estimate the distribution of the soil resistance to driving along the length and at the toe of the pile. The static capacity is predicted from dynamic pile test results and compared to the actual static load tests. Our first case history is for two 1235-mm-diameter steel pipe piles driven to penetrations of 12.5 and 20 m with a Junttan HHK 14S hydraulic hammer. When the piles were redriven, there was little change in the shaft resistance and end bearing. Therefore, the shaft resistance obtained from the CAPWAP analyses was compared directly to the results of tension tests performed about 50 days after redriving. Our second case history is for a 914-mm-diameter steel pipe pile redriven using a Berminghammer B-6505 diesel hammer in dense to very dense silty sand to sand, stiff to very stiff clay, and very dense silty sand. The pile was redriven 46 blows for 25 mm of movement, and CAPWAP analyses were performed at the beginning and end of restrike at 47.5-m penetration. The minimum compressive pile capacity was predicted by adding the shaft resistance for Segments 1 through 13 at the beginning of driving and the shaft resistance for Segments 14 through 24 at the end of driving, and compared to a load test performed 5.5 months after driving. Our third case history is for a 2000-mm-diameter steel pipe pile driven with a Menck MRBS 5000 steam hammer to a penetration of 30.6 m in very silty clay. The compressive pile capacity was predicted for a load test performed 52 days after driving using CAPWAP results for the end of initial driving and the beginning of restrike after a delay of 43 hours for one of the reaction piles and an estimated dissipation in pore pressures.