Site characterization of a dynamically compacted silty fine sand

Abstract

A reclaimed land of approximately 2400 hectares is under construction as part of an industrial development at Mail Liao Township, on the West Coast of Taiwan. Silty fine sand dredged offshore was placed hydraulically to reach a final grade of 3 m above sea level. The foundation soil consists of similar material that extends to several hundred meters below sea level. The new sand fill and the underlying foundation soil was dynamically compacted to increase the sand density within top 10 m. Earlier attempts to estimate pile shaft frictions using CPT data according to existing methods were 30 to 70% below those measured in pile load tests at Mai Liao. A new method to predict the shaft friction that considers the characteristics of the silty fine sand at Mai Liao and the effects of dynamic compaction is proposed. The new method was developed based on a series of laboratory experiments that include CPT chamber calibration tests. According to comparisons with four pile load tests, the new method provides a reasonable and slightly conservative prediction for the shaft friction of driven PC piles. The average error was - 12%.