CHST Practice Test – Complete Exam Preparation

The maximum allowable angle for the walls of a trench dug in clay material, particularly at a depth of five feet, is 53 degrees. This angle is based on the stability of the soil and the specific properties of clay. In geotechnical terms, this angle corresponds to the angle of internal friction typically found in clay, which acts to prevent slides and collapses within the trench.

Understanding the angle of repose for clay materials is crucial for ensuring safety when working in excavation sites. The 53-degree angle provides a balance between the necessary wall inclination to maximize space and the support needed to prevent cave-ins. Trench safety standards dictate that this angle is recommended for maintaining structural integrity in such environments.

Other angles listed, like 45 degrees, are generally more suitable for less cohesive soils, while higher angles beyond 53 degrees may not provide sufficient support for the walls of the trench, increasing the risk of soil failure.