United States. Department of Transportation. Federal Highway Administration
Abstract
DTFH61-93-C-00047Research has been conducted on the potential improvement of dynamic wave equation analysis methodology using in-situ soil testing techniques. As a basis for this investigation, the literature was reviewed and a summary was compiled of efforts made to date on the development of models and associated parameters for pile driving analysis. Furthermore a data base was developed containing more than 150 cases of test piles with static load tests, dynamic restrike tests, soil information, driving system data and installation records. One hundred data base cases were subjected to correlation studies using both wave equation and CAPWAP. This work yielded dynamic soil model parameters which did not indicate a specific relationship with soil grain size. The in-situ soil testing device utilized was a Modified SPT which yielded data from both static and dynamic measurements. Either static uplift or torque tests yielded static ultimate shaft resistance, and uplift tests also indicated a shaft resistance quake. Static compressive tests on a special tip indicated ultimate end bearing and associated toe quake. Indirectly, by signal matching, soil damping parameters were calculated. These quantities were then used for the prediction of full-scale pile behavior. Data from the Modified SPT were gathered and analyzed on six sites with previous full-scale static pile tests and on three sites where static load tests were to be performed at a later date. Recommendations derived from these tests pertain to the current soil model and to proposals for future changes. In general, the current approach was found to yield, on the average, very reasonable results for end of installation situations. For restrike tests, standard parameters may be misleading. Any necessary modifications to the current approach, for example, the use of particularly large toe quakes or low toe damping factors, should be based on Modified SPT measurements. Differences between prediction and full-scale pile field behavior were attributed to soil strength changes over relatively small distances which cannot be detected with standard SPT spacings of 5 ft (1.5 m)
