Upload
cruz
View
142
Download
2
Tags:
Embed Size (px)
DESCRIPTION
Excavation, Trenching, and Soil Mechanics. Subpart P Jim Howry. Points To Be Covered:. 1926.650: Scope and Application 1926.651: Specific Excavation Requirements 1926.652: Requirements for Protective Systems 1926 Subpart P Appendix A: Soil Classification - PowerPoint PPT Presentation
Citation preview
04/22/23 www.oshainfo.gatech.edu 2
Points To Be Covered: 1926.650: Scope and Application
1926.651: Specific Excavation Requirements
1926.652: Requirements for Protective Systems
1926 Subpart P Appendix A: Soil Classification
Other Appendix and Tabulated Data!
4www.oshainfo.gatech.edu04/22/23
Number of Serious Violations - FY 00 2
1468
994
948
785
783
755
660
609
595
522
501(b)(1) - M
100(a) - E
451(g)(1) - L
21(b)(2) - C
451(e)(1) - L
652(a)(1)- P
451(b)(1) - L
503(a)1)- M
20(b)(2) - C
1053(b)(1) - X
Most Frequently Cited Serious Violationsin Construction – FY00
Employee training
Head protection
Scaffolds - Platform construction
Excavations - Protection of employees
Inspections by competent persons
Scaffolds - Fall protection
Fall protection - Unprotected sides & edges
Portable ladder 3 feet above landing surface
Fall hazards training program
Scaffolds - Safe access
Standard & Subpart
-1926.
5www.oshainfo.gatech.edu04/22/23
Number of Serious Violations - FY 00 16
Subpart P - Excavations(1926.650 - 652)
83
263
345
351
755652(a)(1)
651(c)(2)
651(k)(1)
651(j)(2)
651(k)(2)
Standard - 1926.
Employee protection in excavations - Protective system use
Inspections by competent person
Protection from falling/ rolling materials/ equipment
Egress from trench excavations
Competent person inspection - Employees removed from hazard
04/22/23 www.oshainfo.gatech.edu 6
Fatal Facts! An employee was installing a small
diameter pipe in a trench 3’ wide, 12-15’ deep and 90 feel long. The trench was not sloped or shored nor was there a box or shield to protect the employee. Further, there was evidence of a previous cave-in. The employee apparently reentered the trench, and a second cave-in occurred, burying him. He was found face down in the bottom of the trench.
04/22/23 www.oshainfo.gatech.edu 7
Four employees of a mechanical contractor were laying a lateral sewer line at a building site. The foreman, a plumber by trade, and a laborer were laying an eight-inch, 20-foot long plastic sewer pipe in the bottom of a trench 36 inches wide, nine feet deep, and approximately 50 feet long. The trench was neither sloped nor shored, and there was water entering it along a shale seam near the bottom. The west side of the trench caved in near the bottom, burying one employee to his chest and completely covering the other. Rescue operations took two and five hours - too late to save the men.
04/22/23 www.oshainfo.gatech.edu 8
1926.650Scope and Application
“This subpart applies to all open excavations made in the earth’s surface. Excavations are defined to include trenches.”
04/22/23 www.oshainfo.gatech.edu 9
What Is Soil?
A soil is a mixture of rock, water, air and a variety of other substances.
Soil is made up of rock in the form of small particles and spaces called voids. Normally some part of these voids is filled with water.
04/22/23 www.oshainfo.gatech.edu 10
Solid Rock weighs about 167 lbs. Per cubic foot. Since a cubic foot of soil is about ½ rock it will weigh about 83 lbs. Add in water and the weight begins to rise to around 114 lbs. (if saturated).
Do the math and a simple cubic yard of soil can weigh over 3000 lbs! That is a ton and a ½!
Weighing in on Soil…
04/22/23 www.oshainfo.gatech.edu 14
Protecting Employees in Excavations
1926.652 (a)(1) “Each employee in an excavation shall be
protected from a cave-ins by an adequate protective system designed in accordance with paragraph (b) or (c) of this section except when:
(I) Excavations are made in entirely stable rock; or
(ii) Excavations are less than 5’ in depth and examination of the ground by a competent person provides no indication of a potential cave-in.”
04/22/23 www.oshainfo.gatech.edu 15
Protective Systems “a method of protecting employees
from cave-ins, from material that could fall or roll from an excavation face or into and excavation, or from the collapse of adjacent structures. Protective systems include support systems, sloping and benching systems, shield systems, and other systems that provide the necessary protection”
04/22/23 www.oshainfo.gatech.edu 16
So…We have Options: Slope, or Bench according to allowable
configurations… Use a Registered Professional Engineer
to design a sloping or benching system. Use support systems in accordance with
requirements set forth in the standard. Purchase an engineered system,
(example..a trench box or shield.) Have a PE design a shielding or shoring
system specific to your task.
04/22/23 www.oshainfo.gatech.edu 17
29 CFR 1926.652(b)(4)(i) Design by a registered
professional engineer… Any system not found within the
guidelines set forth in the standard, or within the tabulated data tables in the standard requires use of a Professional Engineer.
*No where in the standard or tabulated data does it allow for excavations deeper than 20 feet.
04/22/23 www.oshainfo.gatech.edu 18
Competent Person “one who is capable of identifying
existing and predictable hazards in the surroundings, or working conditions which are unsanitary, hazardous, or dangerous to employees, and who has the authorization to take prompt corrective measures to eliminate them”
(Knowledge & Authority)
04/22/23 www.oshainfo.gatech.edu 19
1926.651(k)(1)Inspections
•Daily Inspection of excavations shall be conducted by a ‘competent person’ prior to the start of work and as needed throughout the shift.
•Inspections shall also be conducted after every rainstorm or other hazard increasing occurrence.
04/22/23 www.oshainfo.gatech.edu 20
Access and Egress1926.651 (c)(2)
“A stairway, ladder, ramp or other safe means of egress shall be located in a trench excavations that are 4’ or more in depth so at to require no more than 25’ of lateral travel for employees.”
04/22/23 www.oshainfo.gatech.edu 21
Soil Tests 1926 Subpart P appendix A, Soil
Classification (c)(3) In order to classify a soil A, B, or C
at least one visual and one manual test must be performed by a competent person.
04/22/23 www.oshainfo.gatech.edu 22
Visual Test “Visual analysis is conducted to
determine the qualitative information regarding the excavation site in general, the soil adjacent to the excavation, the soil forming the sides of the open excavation, and the soil taken as samples from the excavated materials.”
04/22/23 www.oshainfo.gatech.edu 23
Manual Tests “Manual analysis of soil samples is
conducted to determine quantitative as well as qualitative properties of soil to provide more information in order to classify soil properly.”
Examples: Thumb penetration, Pocket penetrometers, Drying tests, Sedimentation…
04/22/23 www.oshainfo.gatech.edu 24
Thumb Penetration Test 1926 Subpart P Appendix A(2)(iii) …type A soils with an unconfined
compressive strength of 1.5 tsf can be readily indented by the thumb;however they can only be penetrated by the thumb only with great effort…Type C soils with an unconfined compressive strength of .5 tsf can be easily penetrated several inches by the thumb, and can be molded by light finger pressure.
04/22/23 www.oshainfo.gatech.edu 25
SOLID ROCK “Natural solid mineral matter that
can be excavated with vertical sides and remain intact while exposed”
04/22/23 www.oshainfo.gatech.edu 26
Type A Soil Cohesive soil with an
unconfined, compressive strength of 1.5 Tsf
Examples of this type of soil are: Clays, silty clay, sandy clays, and clay loam.
04/22/23 www.oshainfo.gatech.edu 27
A Soil is NOT type ‘A’ IF: The soil is fissured The soil is subject to vibration The soil has been previously
disturbed The material is subject to other
factors that would require it to be classified as a less stable material.
Water is present
04/22/23 www.oshainfo.gatech.edu 28
Sources of Vibration Traffic Railroad Operations Heavy Equipment Operations Jack Hammer Operations Tamping Machine Operations Thumping Car Stereos that make
you want to pull your hair out and to…never mind…
04/22/23 www.oshainfo.gatech.edu 29
Type B Soil Cohesive soil with an unconfined
compressive strength greater than .5 Tsf
Granular cohesionless soils including; silt, silt loam, sandy loam, and some sandy clay loam
Previously disturbed soils except those which would otherwise be classified as Type ‘C’ soil
04/22/23 www.oshainfo.gatech.edu 30
Type ‘C’ Soil Cohesive soils with an unconfined
compressive strength of 0.5 Tsf or less
Granular soils including gravel, sand, and loamy sand
Submerged soil, or soil from which water is freely seeping
04/22/23 www.oshainfo.gatech.edu 31
Sloping Requirements by Soil Type
Soil or Rock TypeMaximum
Allowable Slope for Excavations less
than 20’Stable Rock Vertical (90 Deg.)
Type A ¾ to 1 (53 Deg.)
Type B 1 to 1 (45 Deg.)
Type C 1 ½ to 1 (34 Deg.)
04/22/23 www.oshainfo.gatech.edu 35
Trench Boxes or Shield Systems:
“A structure that is able to withstand the forces imposed on it by a cave-in and thereby protect employees.”
04/22/23 www.oshainfo.gatech.edu 37
Is this allowable?
YES! If the Trench boxes are designed to be stacked and are used in accordance with their tabulated data.
04/22/23 www.oshainfo.gatech.edu 38
Trench Boxes and Sloping or Benching
Trench boxes are generally used in open areas, but they may also be used in combination with sloping and benching. The box should extend at least 18 inches above the surrounding area if there is sloping toward the excavation.
04/22/23 www.oshainfo.gatech.edu 42
Shoring (Shoring System)
“A structure such as metal hydraulic, mechanical or timber shoring system that supports the sides of an excavation and which is designed to prevent cave-ins.”
04/22/23 www.oshainfo.gatech.edu 46
Surface Encumbrances Adjacent
Structures Roads and/ or
Sidewalks Curb and Gutter Light poles Utilities Mailboxes
1926.651 (a) “All surface
encumbrances that are located so as to create a hazard to employees shall be removed or supported as necessary to safeguard employees”
04/22/23 www.oshainfo.gatech.edu 47
Utilities
1926.651(b) The estimated location of utility
installations, such as sewer, telephone, fuel, electric, …that reasonably may be expected to be encountered during excavation work, shall be determined prior to opening an excavation…
04/22/23 www.oshainfo.gatech.edu 48
Locates
Red = Power Blue = Water Orange = Communications Yellow = Gas
04/22/23 www.oshainfo.gatech.edu 49
Can an Excavation be a Confined Space…?
Oxygen deficient atmospheres: less than 19.5% oxygen.
Potential for other gasses to be present include but not be limited to:
Natural Gas from potential leaks or cut lines.
Methane from decayed matter.
04/22/23 www.oshainfo.gatech.edu 50
Summary Call before you dig.
Use at least one visual and one manual soil test to determine soil type.
A Ladder is required for access and egress at 4’
The ladder must be
within 25’ lateral travel at all times.
At 5’ depth some type of ‘protective system is required’.
Treat all soil as Type ‘C’ and slope at 1 ½ : 1 and you are covered.
If not: Use some type of shoring or shielding to protect your employees.
Excavations over 20’ require the use of a P.E.