Membership - Overview
Deep Foundations Institute (DFI) is an international association of contractors, engineers, suppliers, academics and owners in the deep foundations industry.
Bedrock: Strongest. Slate and shale: fine textured soft rock. Boulders: Rocks detached from the bedrock. Decomposed rock: Disintegrated rock masses that were originally solid. Hardpan: Consolidated mixture of gravel, clay, and sand, and is a good foundation base for buildings. Gravel: granular rock particles ranging in size from 1/4" to 3-1/2". Sand: loose rock particles about .002" to 1/4". Silt: fine-grained sedimentary material .002" or less in particle size. Clay: Firm cohesive.