Soil stiffness from back-analysis of pile load tests in Al Burrullus

Abstract

Estimation of soil stiffness plays an essential role in settlement computations associated with the design of foundations. Full-scale pile load testing is the best means for defining the load displacement response. The results of 17 pile load tests (compression, tension, and lateral) are analyzed to determine pile capacity and operational soil stiffness. Tests are conducted in Al Burrullus area located north of Egypt. Three-dimensional modeling of the pile load tests is performed using PLAXIS 3D. For each pile load test, the operational soil stiffness is obtained to match the load–displacement response. Ratios of the operational to small-strain stiffnesses G/G max are compared to the mobilized load ratios Q/Q ult and pseudo-strain w/d. As the mobilized load ratio Q/Q ult and pseudo-strain increase, the ratio of the operational to small-strain stiffnesses G/G max decreases. The results provide guidance for choosing the appropriate operational soil stiffness based on the mobilized load ratio or pile head movement and small-strain stiffness.