What is benching in excavation?
Benching is a method of protecting employees from cave-ins by excavating the sides of an excavation to form one or a series of horizontal levels or steps, usually with vertical or near-vertical surfaces between levels.
At what depth does OSHA require shoring?
5 feet
Trenches 5 feet (1.5 meters) deep or greater require a protective system unless the excavation is made entirely in stable rock. If less than 5 feet deep, a competent person may determine that a protective system is not required.
What is the fatality rate for excavation work?
Research done by OSHA during the course of the revision of the Standard in the 1980’s showed that the fatality rate in excavation work was as much as 112% greater than the rate for construction in general (. 508 per 1000 employees in excavation work as opposed to . 248 per 1000 for construction in general).
What causes most deaths in excavation?
Trenching and excavation work accounts for 112% more fatalities than that of just general construction work. Trenching involves working in deep dig outs, deaths usually happen when soil is piled to closely to the edge and it collapses onto workers causing asphyxiation or drowning.
What is the 1 2 depth RULE?
TABLE B-1 Footnote(2) A short-term maximum allowable slope of 1/2H:1V (63º) is allowed in excavations in Type A soil that are 12 feet (3.67 m) or less in depth.
At what depth is benching required?
The trench shield must extend at least 18 inches above the top of the vertical side. For combination slope/bench systems in TYPE C soil and a trench depth of less than 20 feet, the steepest maximum allowable slope is 34 degrees from the horizontal is allowed only if a trench support or shield is used.
What is the proper slope for excavation?
Footnote(2) A short-term maximum allowable slope of 1/2H:1V (63 degrees) is allowed in excavations in Type A soil that are 12 feet (3.67 m) or less in depth. Short-term maximum allowable slopes for excavations greater than 12 feet (3.67 m) in depth shall be 3/4H:1V (53 degrees).
At what depth must an excavation be supported?
For example, OSHA in the United States still specifies a depth that trench shoring must be used, which is currently 5 ft or 1.5 metres deep. However, if the trench is less than this depth, a competent person must determine if a protective system is required.
How do you calculate excavation work?
So, the formula is: Ab = Wb * Lb, where Wb and Lb are the width and length of the bottom of the excavation. At = Wt * Lt, where Wt and Lt are the width and length of the top of the excavation.
What type of soil must never be benched?
Type C soil
Type C soil cannot be benched.
What are the three methods of excavation?
Each process may require different tools and techniques to ensure you can safely complete your task.
- Bridge Excavation.
- Borrow Excavation.
- Channel Excavation.
- Drainage Excavation.
- Dredge Excavation.
- Stripping.
- Earth Excavation.
- Muck Excavation.
How do you calculate excavation for foundation?
How do you calculate trench excavation? Determine the volume of the trench by using the formula: Volume = Width x Length x Depth. As an example, a trench 12 feet long with an average width of 2.3 feet and an average depth of 5 feet has a volume of (12 x 2.3 x 5) cubic feet.
How much does excavation cost?
Excavation in an area with loose soil, no trees and no rocks in the dirt will be much simpler, and therefore cheaper than removing dozens of mature trees and dealing with boulders stuck in clay-like soil. Cut and fill rates can vary greatly from $1 to $12 per cubic yard. Haul distance will affect excavation more than size.
What does excavation mean in construction?
Excavation levels the ground for new foundations, additions to existing structures, new outbuildings—such as sheds and garages, new driveways, or new sod or landscaping. The excavation site should be surveyed and cleared of any underground pipes or utility lines to prevent dangerous ruptures during a project.
What factors affect the cost of an excavation project?
Several cost factors affect small- and large-scale excavation projects. Some excavation contractors charge an hourly rate for their services, especially for smaller jobs. Excavation contractors sometimes also charge by the hour for clearing jobs, also known as “topsoil excavation.”
How much does it cost to dig up rock?
Inaccessible areas with rocky terrain can cost as much as $20,000. Rock excavation, if it involves blasting to create small, movable chunks of rock from shelves or large boulders runs $40 to $100 per cubic yard. Rock presents the largest cost increase for digging if it’s larger than an excavator or backhoe can handle.