EARTH PRESSURE DETERMINATION IN TRENCH RESCUE SHORING SYSTEMS

Abstract

Despite Occupational Health and Safety Administration (OSHA) excavation safety requirements, victims continue to be trapped in collapsed excavations every year. The fire service has been tasked with developing technical rescue practices and procedures for efficient rescues and/or body recoveries in trenches or shallow excavation failures. Rescuers and victims depend on the performance of the standardized trench rescue shoring system developed by the technical rescue industry for their safety and welfare. The system has undergone little technical analysis. This dissertation presents a building block towards developing a technical understanding and analysis of the behavior of a shoring system that is used in trench rescues or as a bracing in shallow excavations.

The accepted engineering practice widely used for determining earth pressure in a braced excavation is based on soil type and deep excavations and does not account for strut loading, whereas, it has been shown that shallow braced excavations respond differently. This research evaluated the applicability of present engineering practice on the current standardized trench rescue shoring system. A new method was developed for calculating the earth pressure developed using the rescue shoring system. The method determines the earth pressure as a function of strut loading. The method can also be used to determine the maximum strut loading that can be used without causing the soil to fail. The method can be used for any type of soil as field work validated the concept that soil type has little effect on the shape of the earth pressure distribution in shallow braced excavations.