Pile Load Capacity using Static and Dynamic Load test

Abstract

ABSTRACT Piles are common for construction of deep foundation in Bangladesh. Confirming the pile capacity is a job for a geotechnical engineer. From the soil investigation data, piles can be designed but it need to be confirmed by static pile load test or dynamic pile load test. Generally, static pile load test is used to estimate pile capacity whereas dynamic pile load test is a relatively new method for the engineers of Bangladesh. This study presents an evaluation of ultimate pile load capacity by static and dynamic load test methods. To establish a comparison, a field experiment was conducted on two full scale driven precast piles. Both piles were tested using dynamic and static load test. For dynamic load test pile capacity was determined using CAPWAP (CAse Pile Wave Analysis Program). In case of static load test pile capacity was calculated using Davission, Butler and Hoy, British standard and BNBC (Bangladesh National Building Code) 1993 methods. The capacity of two test piles was also calculated using soil investigation data applying BNBC-2015 (Draft version), AASHTO-2002 method. For these two driven piles capacity calculations were also investigated following driving equations. The relationship among capacity of static load test, dynamic load test, predicted capacities (using BNBC-2015, BNBC SPT, AASHTO-2002, driving equations) were compared and correlation values were obtained. To generalize the study, ten cast-in-situ and fifteen precast test pile data were collected. In each case, soil investigation report of the particular site, pile properties, CAPWAP capacity was available for detailed study. From the collected data, it was found that predicted capacity of precast driven piles using BNBC-2015 static bearing capacity has a very good co-relation with CAPWAP capacity confirmed by dynamic load test. For BNBC-15 Static method, CAPWAP capacity=1.10X BNBC 2015 Static capacity (r2=0.81).However, pile capacity calculated using BNBC-2015 SPT method also showed good correlation compare with the CAPWAP capacity. In this method CAPWAP capacity=1.06X BNBC 2015 SPT capacity (r2=0.77). Similarly, cast-in-situ pile capacity matched fairly well with all the considered methods like: BNBC-2015 static bearing capacity, BNBC-2015 SPT, AASHTO-2002 comparing with the CAPWAP capacity. From this study three relations were established. They are CAPWAP capacity=1.15X BNBC 2015 Static capacity (r2=0.81), CAPWAP capacity=1.04X BNBC 2015 SPT capacity (r2=0.89) and CAPWAP capacity=0.91X AASHTO-2002 capacity (r2=0.92). Recommendation and conclusions were also made for piles of Bangladesh considering different alternative methods.