Heavy Civil Exam 1 Practice 2026 - Free Practice Questions and Study Guide

Type A soils are soils with cohesion and higher strength, used in safety classifications for trenching. Clay fits this well because its fine particles stick together through cohesion, giving greater shear strength and stability. Sand and gravel are granular and rely on friction rather than cohesion, making them less stable in trenches and typically not Type A. Silt is fine-grained but lacks the strong cohesion of clay, so it’s usually categorized as Type B or C depending on strength. So clay is the material that characterizes Type A soils.