Load Testing of Permanently Cased Drilled Shafts Founded in Hartford Shale

by Thomas G. Lewis, Louis Berger & Associates, East Orange, United States,



Document Type: Proceeding Paper

Part of: Design and Performance of Deep Foundations: Piles and Piers in Soil and Soft Rock

Abstract: The axial and lateral load testing of three, 30 inch (76cm) diameter, permanently cased drilled shafts is analyzed herein. The prototype shafts were founded in (or on) Hartford Shale bedrock, overlain by approximately 30 feet (9m) of layered fill and soils. The three shafts were tested vertically, one for end-bearing, one for rock socket side-shear, and one for end-bearing combined with side-shear. The center shaft was tested for pure socket shear by using a double casing. The two outer shafts were then tested laterally by simultaneously jacking outward against the center shaft. Load test instrumentation included two pressure cells, three inclinometer tubes, nine rock extensometer/telltales and over fifty vibrating wire strain gauges. Laboratory testing was performed on rock and concrete core samples. Stress-strain response is computed for the bedrock, concrete, and soil. The resulting test values are compared with expected and published values. End-bearing and socket side-shear strengths are also analyzed and discussed.

Subject Headings: Load tests | Shafts | Drilled shafts | Shale | Load factors | Stress strain relations | Lateral loads | Axial loads | North America | Hartford | Connecticut | United States

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