挖掘作业安全

1、Excavation Safety共三十四页Objectives:Highlight the hazards of working in a excavation.How to protect employees from cave-ins.Factors that pose a hazard to employees working in excavations.The role of a competent person at an excavation site.共三十四页Introduction:Cave-ins are perhaps the most feared trenchin

2、g hazard.But other potentially fatal hazards exist including:Asphyxiation due to lack of oxygen in a confined spaceInhalation of toxic fumes, drowning, etc.Electrocution or explosions can occur when workers contact underground utilities. 共三十四页Definitions: Cave-In: Means the separation of a mass of s

3、oil or rock material from the side of an excavation, or the loss of soil from under a trench shield or support system, and its sudden movement into the excavation, either by falling or sliding, in sufficient quantity so that it could entrap, bury, or otherwise injure or immobilize a person.共三十四页Defi

4、nitions: Excavation Falling onto the Personnel: A RELATIVELY SMALL COLLAPSE MIGHT INVOLVE A CUBIC METRE OF SOIL, BUT A CUBIC METRE OF SOIL WEIGHS OVER A TONNE.PERSONNEL BURIED AT THE BOTTOM OF THE TRENCH UNDER THIS VOLUME OF MATERIAL WOULD BE UNABLE TO BREATHE DUE TO THE PRESSURE ON THEIR CHESTS, AN

5、D SO WOULD QUICKLY SUFFOCATE AND DIE.共三十四页Anatomy of a Cave - In:There is usually no warning before a cave-in共三十四页Definitions Continued:Excavation a man-made cut, cavity, trench, or depression formed by earth removal.Trench a narrow excavation. The depth is greater than the width, but not wider than

6、 15 feet.Shield - a structure able to withstand a cave-in and protect employeesShoring - a structure that supports the sides of an excavation and protects against cave-insSloping - a technique that employs a specific angle of incline on the sides of the excavation. The angle varies based on assessme

7、nt of impacting site factors. 共三十四页Excavation Hazards:Surface encumbrancesUtilitiesAccess/EgressVehicle trafficFalling loadsMobile equipmentHazardous atmospheresWater accumulationAdjacent structuresLoose rock or soilFallsCave-in共三十四页General Requirements:Before any excavation actually begins, the emp

8、loyer must determine the estimated location of utility installations: Sewer, telephone, fuel, electric, water lines, or any other under ground installations that may be encountered during digging.A competent person will inspect, on a daily basis, excavations and adjacent areas for possible cave-ins,

9、 failure of protective systems and equipment, hazardous atmospheres, or other hazardous conditions.Takes prompt corrective measures to eliminate hazards.Adequate protective systems will be utilized to protect employees. This can be accomplished through: Sloping, Shoring, or Shielding.Workers must be

10、 supplied with and wear any PPE deemed necessary to assure their protection. Mechanical excavators and power tools should not be used within 0.5 mIf a trench is 4 feet or deeper, stairways, ramps, or ladders will be used.The employees must not have to travel any more than 25 feet to reach the stairw

11、ays, ramps, or ladders.4 feet and more trenches Toxic and hazardous atmosphere will be tested daily.共三十四页Access:The ladder should extend 3 feet above the excavation共三十四页Access:These two ladders which are lashed together are not an adequate means of egressThe ladder should extend 3 rungs above the to

12、p of the excavation共三十四页Ladder to be 1 Meter Above Wall:共三十四页Excavation Protection Systems:There are three basic protective systems used in excavations and trenches:Sloping and Benching SystemsShoring SystemsShielding Systems共三十四页Simple Sloping:共三十四页Benching:共三十四页Shoring Systems:Support system for t

13、rench faces used to prevent movement of soil, underground utilities, foundations.There are two basic types of shoring, timber and aluminum hydraulic.共三十四页Shoring Systems:共三十四页Timber Shoring Installations:共三十四页Hydraulic Shoring:共三十四页Pneumatic Shoring:共三十四页Shielding Systems:A- Trench Boxes:The space b

14、etween the outside of the trench box and the face of the trench should be small as possible, and backfilled to prevent lateral movement of the box.共三十四页Excavation Inspections:Daily Inspections of ALL excavations by Competent Person at Start of shift, or as needed, following rainstorms or other hazar

15、d-increasing event:Possible cave-insProtective system failureWater accumulationHazardous atmospheresCompetent person has authority to remove workers fromthe excavation共三十四页Causes of Cave Ins:共三十四页Causes of Cave Ins:When water is present in an excavation it is extremely hazardous to enter. Also no he

16、ad protection共三十四页Causes of Cave Ins:Note: telephone pole adjacent to excavation, not supported / removed共三十四页Inadequate Protective System:This excavation has inadequate support posts and egress access.共三十四页Inadequate Protective System:This worker is in a trench with no protective system, that is no

17、t sloped or benched and has no means of egress.共三十四页Hazardous Condition:The weight and vibrations of the machinery above make this a very hazardous condition. They should not be working under any machinery.共三十四页Hydraulic Trench Support:Using hydraulic jacks the operator can easily drop the system in

18、to the hole.Once in place, hydraulic pressure is increased to keep the forms in place.Trench pins are installed in case of hydraulic failure.共三十四页Hazardous Atmosphere:Test excavations more than 4 feet before an employee enters the excavation for:Oxygen deficiency.High combustible gas concentration.High levels of other hazardous substances.共三十四页Means of Egress:A stairway, ladder, or ra