All simple slope excavations 20 feet or less in depth shall have a maximum allowable slope of 1½:1. 2. All excavations 20 feet or less in depth which have vertically sided lower portions shall be shielded or supported to a height at least 18 inches above the top of the vertical side.
In this post
When a trench is 4 feet or more in depth?
A stairway, ladder, ramp or other safe means of egress shall be located in trench excavations that are 4 feet (1.22 m) or more in depth so as to require no more than 25 feet (7.62 m) of lateral travel for employees.
What is the maximum allowable slope?
Maximum allowable slope means the steepest incline of an excavation face that is acceptable for the most favorable site conditions as protection against cave-ins, and is expressed as the ratio of horizontal distance to vertical rise (H:V).
How do you calculate slope of excavation?
Slope Angle Calculations
This simple equation will tell you the proper opening width: (depth x 2) x type slope ratio + width of original excavation = top width. As an example, let’s calculate the slope angle of a simple trench that is 6 feet deep by 2 feet wide, factoring in the type of soil. Type A: (6 feet x 2) x .
What is the maximum depth of a benched excavation in Alberta?
6 metres
See Figure 32.11; (4) the maximum depth of a benched excavation is limited to 6 metres. Increasing the depth of the excavation or increasing the height of the slope and benches increases the risk of slope failure, compromising the safety of workers within the excavation.
How deep can a trench be without 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 difference between a trench and an excavation?
What is the difference between an excavation and a trench? OSHA defines an excavation as any man-made cut, cavity, trench, or depression in the Earth’s surface formed by earth removal. A trench is defined as a narrow excavation (in relation to its length) made below the surface of the ground.
What type of soil Cannot be benched?
Type C soil cannot be benched.
What depth is benching required?
Sloping and Benching
Sloping, benching, or other approved cave-in protection systems must be utilized in excavations 5 feet or greater in depth. For excavations greater than 20 ft depth, the slope or bench shall be designed by a registered professional engineer.
What is a Kick Out in excavation?
“Kickout” means the accidental release or failure of a cross brace. “Protective system” means a method of protecting employees from cave-ins, from material that could fall or roll from an excavation face or into an excavation, or from the collapse of adjacent structures.
How is excavation depth calculated?
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. In our example, Wb = Lb = 5 and Wt = Lt = 15, so Ab = 5 * 5 = 25 and At = 15 * 15 = 225, and D = 5.
How do you calculate depth?
Worked Example
- Step 1: List the known quantities. Wave speed, v = 1500 m/s.
- Step 2: Write out the wave speed, distance and time formula.
- Step 3: Rearrange the equation to make distance (x) the subject. x = v × t.
- Step 4: Put known values into the equation. x = 1500 × 0.12 = 180 m.
- Step 5: Half the distance to obtain the depth.
What is the maximum allowable slope for Type A soil?
3/4:1
Type A Soils shall have a maximum allowable slope of 3/4:1 (53 degrees).
Why is 1.2 meter excavation confined space?
The 1.2m rule for trenches used to be in older health and safety regulations and is often still quoted today. The basis of the rule is that, if a trench is under 1.2m deep, then people can enter the trench without the sides of the excavation being supported or battered back.
When excavating to depths of 1.2 m or more what three methods are used to prevent cave-ins?
What are the different types of protective systems used to protect against cave-ins? There are two basic methods of protecting workers against cave-ins: Sloping. Temporary protective structures (e.g., shoring, trench boxes, pre-fabricated systems, hydraulic systems, engineering systems, etc.)
What is the minimum depth of excavation of soil from its natural level?
The Contractor shall perform the clearing and grubbing (if any), of top soil consisting mainly of loose soil, vegetable and organic matters, drift sand, unsuitable soil and rubbish by scarifying the areas to be excavated and sidewalks to a minimum depth of 300 mm from the natural ground level.
Can a trench be wider than 15 feet?
According to OSHA, a trench is a narrow excavation (compared to its length) made beneath the ground’s surface. Usually, a trench’s depth is relatively larger than its width, whereas the width at the bottom is never greater than 4.6 meters or 15 feet.
Does a trench shield prevent a cave-in?
A good and strong trench shield helps keep the work space safe and protects workers from hazardous trench collapses. Trench shields function to keep the side walls of the trenches secure and prevent them from caving-in.
Can you use a metal ladder in a trench?
Leaning a portable step ladder that has been folded closed against the side of a trench is a practice that is prohibited by most portable step ladder manufacturers, and must be avoided unless the manufacturer states their step ladder is designed to do that.
How can a person buried only up to their neck suffocate during a cave-in?
Suffocation can occur even if your nose and mouth are not buried. That’s because in a cave-in, heavy soil can put 800 pounds of pressure on your chest and make it impossible to breathe.
How do you prevent soil collapse during excavation?
Soil collapse in a trench can be prevented either by side slope or by benching of side wall or by shoring. Selection of a particular method is made depending on the site and soil condition.