Excavation and Trench

Excavation and Trenching


Each year there are many deaths and many injuries resulting in work stoppages, which are directly related to trenching. Fatalities related to trenching are mainly caused by the collapse. Fatalities occur from suffocation or crushing a worker is buried in the ground collapsing. The following are the main causes of injuries resulting in work stoppages related to the digging of trenches:

• Materials falling into the trench;
• Handling and disposal of materials;
• Falls when workers enter or leave;
• Maneuver on the equipment or cuttings
• Fall in the trench;
• Exposure to toxic gases.

The work should not be done in a trench unless another worker is working above the ground near the trench or the means of access to the trench.
Definitions

Excavation:

Any cut, cavity, trench or depression in the earth's surface resulting from the displacement of rock or soil. The excavation includes any work, operation or activity including the resulting disturbance of the earth, without limitation, excavating, digging, slicing, plowing, drilling, tunneling, drill, fill, mine, a strip topsoil, level the
land, move the peat, quarrying, piling, identify and assess.

Trench

An excavation that is less than 3.7 m.
(12 feet.) Wide at the bottom, and over 1, 5 deep, and of any length.
 
Exposure (use) manual

The use of hand shovels, other similar instruments, or a water aspirator to expose buried cables, pipes or other objects buried.
Causes of collapse

Often, soil properties vary considerably from top to bottom and along a trench.
Many factors such as crackle, water, vibration, time and previous excavations may affect the stability of the trench
(Figure 1). Time is also a critical factor.
Some trenches remain open for a long time and suddenly collapse for no apparent reason.

 

 
Figure 1 - Many factors can affect the stability of the trench

 
 
Figure 2) shows the main causes of collapse. The main factors affecting the stability of the trench are: soil type, moisture, vibration, overload, and the earlier excavations, the existing foundations, and time.

Soil type

Soil type determines the strength and stability of the walls of the trench. The Regulations for Construction (Ontario) described four general types of soil from dry and dense (Type 1) in wet, muddy and unable to support himself (Type 4).

Identify soil types requires knowledge, skill and experience. Even the hard floors may contain defects in the layers making them unstable when excavated. Supervision should be aware of the soil types encountered in a work plan for protection accordingly.
 
(Figure 2) shows the main causes of collapse.
The main factors affecting the stability of the trench are: soil type, moisture, vibration, overload, and the earlier excavations, the existing foundations, and time.
 
Soil type
Soil type determines the strength and stability of the walls of the trench. The Regulations for Construction (Ontario) described four general types of soil from dry and dense (Type 1) in wet, muddy and unable to support himself (Type 4).

Identify soil types requires knowledge, skill and experience. Even the hard floors may contain defects in the layers making them unstable when excavated. Supervision should be aware of the soil types encountered in a work plan for protection accordingly.
 
Moisture content
The amount of moisture in the soil has a great effect on the strength of the soil. Once a trench is dug, the shores of the open excavation is exposed to air. The moisture content of the soil begins to change almost immediately and the strength of the walls may be affected. Over a long excavation is open to the air, the greater the risk of collapse.

Vibrations
The vibrations from different sources can affect the strength of the trench. Often the walls of trenches are subject to vibrations from vehicle traffic or construction operations such as moving of soil, compaction, pile driving and blasting. These issues can all contribute to the collapse of trench walls.

Overload
A surcharge is a load or overweight can affect the stability of a trench. For example, the excavated earth piled near the trench can put pressure on the walls. The location of the piles of debris is important. The cuttings should be kept as far from the edge of the trench as is practical. Mobile equipment and other materials stored near the trench also add a surcharge that will affect the stability of the trench.

One meter from the edge of the base of the pile of rubble is a minimum requirement. The distance should be greater for deeper trenches
 
Excavation
prior


The old trenches utilities, they cross or they go in parallel with the new trench, can affect the strength and stability (Figure 3). The soil around and between these ancient excavations is very unstable. At best, it is considered a Type 3 soil - that is to say, furniture, and the internal force lower.
In some unusual circumstances, it may be of Type 4 - wet, muddy and unable to support himself. This type of soil does not support unless they are set slope or stop
 
 
Existing foundations



Around most of the trenches and excavations, there is a rupture zone where the surcharges, changes in soil conditions or other disturbances can cause collapse. When the foundation of a building adjacent to the trench or excavation extends to the rupture zone, this may result in a collapse (Figure 4). The soil in this situation is generally considered to be Type 3.

 
 
Time


Rain, melting snow, thawing and overflow from streams adjacent to storm drains and sewer systems all produce changes in soil conditions (illustration5). In fact, water from any source can increase the infiltration rate and reduce the cohesion of the soil.
 
 
 
Responsibilities

Direction

• Ensure that employees who expose pressurized pipes or cables are activated sufficiently trained;

• Provide adequate training and equipment to locate underground facilities (eg markers of electrical cables, probes, shovels);

• Provide adequate resources, including time, to ensure that any excavation work may be carried out safely and within acceptable levels of risk for the work included.

HSE Supervisor

• Obtain and review all drawings and leaves the existing alignment.

• At least two working days before starting work (except for emergencies):

i) Contact any other business or individual who may have buried pipe or cable in the vicinity of the proposed excavation and ask them to locate their hose, cable, or other buried structure.
ii) The office sector should also be contacted when staff is not doing the excavation sector.

• If the excavation is done on property not owned by the company, they should contact the landowner to explain how excavation and other work you will perform.

• Complete a visual inspection of the area before the meeting before work, and identifying details such as fences, power lines, the warning signs of pipeline and soil conditions.

Work site supervisor

• Collect and review all relevant schemas and alignment sheets, and conduct a visual inspection of the work site before work is initiated;
• Ensure that landowners and foreign owners of cable and pipe work have been notified at least 2 working days (except in emergencies) before work is initiated;

• Ensure that all piping pressurized phase cables and other buried hazards are at hand before using a shovel backloading within 60 inches of the pipe or cable;

• Ensure that excavation to be left unattended are adequately fenced or barricaded;

• Ensure that all company employees and subcontractors who will be involved in or affected by excavation work, knowledgeable and fully understand the place of work, schedule, risk, management systems
risks and safety measures for the tasks to be performed;

• Ensure that all company employees and subcontractors who will be involved in or affected by excavation work there know and understand fully their duties and responsibilities when they complete the excavation.

Company employees and subcontractors
 
 
Work permit safe
A work permit safely should be established before the earth is shaken to any excavation on the site of the company or others.


technology

Any excavation of more than 6 m deep should be made in the written instructions of a professional engineer or a scientist of the earth.

Written instructions are required:

• Be certified by the professional engineer or a scientist of the Earth
• Be available on the site, and,
• Specify the conditions of the subsoil and the support provided and the requirements of inclination (slope)

The technology is also required where:

There is a deviation from regulatory requirements;
• There is a structure adjacent to the excavation;
The excavation is subject to vibration (traffic) or the hydrostatic pressure and,
The job is located on a slope greater than 33%.

excavation
Identification of the location of the pipe, cable or other underground hazards

• Before starting the excavation, pipe, cable, or other hazards shall be located underground with a reference probe and / or pipe;

• The position of buried objects must be identified on the ground by staking the center line of pipe in each direction (the pious, using color coding standards, must extend well beyond the area to be excavated)
 


• Attend pre-work and visual inspection of the sector, and provide appropriate feedback to their supervisor or representative of the site of work provided;

• Ensure that they know and understand their duties, responsibilities and safety measures to accomplish the work of excavation;

• Do not let the backhoe operated within 60 inches of pipe, cable or other buried structure until it has been manually set and 30 inches from the pipe, cable or other buried structure after
exposure manually;
Procedures for excavation and trenching CRESU
General Procedures

• An analysis of safety should be carried out excavations at risk for significant and high (eg excavation near the facilities, underground and above ground piping, valves, buried cables, slopes and unstable soil conditions, water main crossing the overhead power lines) to ensure that all hazards are identified, risks are assessed and, where necessary, risk management systems are developed to
execution.

• Whenever possible, before any procedure on earth not controlled by the company, re-confirm the entry and access roads with the landowner.

• Locate any pipe, cable, or other hazards buried with a probe and / or positioning point of the pipe, and stake the center line of pipe in each direction (the stakes, using a standard color code, must of
extend beyond the area to be excavated)

• Ensure that a visual inspection of the area is performed, noting details such as fences, power lines, warning signs of pipelines, livestock and soil conditions.

• When working near overhead power lines, ensuring that work is done in a way that does not reduce the original support provided for the posts of energy.
Contact the local energy companies to determine the minimum spaces.

• Benchmarks, utilities, roads and edges must be protected against damage from vehicular traffic or pedestrians.

• The temporary roadways, driveways, spacers (sub-beams), barricades, blankets and turns, over and around the excavations for the movement of vehicles and pedestrians must be provided and maintained.
Such provisions shall comply with orders and regulations.

• Access roads will remain free of vehicles and equipment clogged.
Public and private roads used to haul the equipment will be kept free of deposits and excessive discharge.

Planning a Pre-excavation

Before the excavation activities occur, work must be carefully planned.
The representative said the work site shall:

• Obtain and review all drawings and leaves existing alignment;

• At least two working days (except in emergencies) before work:

- Contact any other company or individual who may have buried the pipe or cable in the vicinity of the proposed excavation and ask that they locate their pipes, cable, or other buried structure;

- Where the staff outside the area doing the excavation, contact the office sector to ensure they are informed about the work;

• If the excavation is done on a ground other than that of the company, contact the property owner to explain how excavation and other work to be done;

• Perform a visual inspection of the area prior to the meeting before work, noting details such as fences, power lines, pipeline warning signs, livestock, and soil conditions.
NOTE: Agreements may be required for crossing the cables, roads, railways or not the company.
These should be properly applied before the starting day as they often take several days for reception.

Meeting before work

A meeting before work (process review meeting before work) to be held with staff of the company and the subcontractor who will perform the excavation or who will be affected by the work of excavation. During the meeting before work, the work site supervisor or representative of the work site indicated will ensure that all company personnel and subcontractors will be directly involved with or affected by, work planned excavation, and be knowledgeable on the subject and fully understands the scope of work, schedule, risk, systems risk management and security measures for the tasks to be performed. In addition, the site supervisor of the work or the site representative of the work shown will ensure that all company personnel and subcontractors that will be directly involved with or affected by, the work planned excavation or knowledgeable about the subject and they fully understand their respective duties, responsibilities and safety measures that must be followed while the excavation is about to be completed.
 
Exposure (use) manual


• Expose the pipe, cable or other hazards buried by hand digging or vacuum cleaner water
Excavation work

• After the pipe was exposed by hand, a minimum distance of 1m (3pds) must be maintained between the pipe, cable and other hazards and buried the bucket (seal) of the excavation machine;

• After the pipe was exposed, the minimum interval between the bucket (seal) of the excavator (extracaveuse) and the pipe must be reduced by 30cm (1pieds);

• If the pipe, cable, or other buried hazards have not been exposed after a hand digging to a depth of 1 .1 m, a backhoe should be used to expand the excavation, and provide that:

- The shovel extracaveuse does not dig in an area or soil has not been polled and do not exceed the depth of the excavation dug by hand

- The center line of the pipe is checked using a probe or a marker of the pipe.

- The machine is used, as required, to extend and tilt the excavation;

- The process of manual exposure is used to dig 30cm, and a probe is used to probe more than 60cm deep, after that the machine is used to expand the area of ​​the excavation;

- Repeat this process until the pipe is located by a probe and exposed by hand digging.

• Where possible, the machines of energy that excavate the embankment should be positioned so that the operator is on the side and away from the edge of the excavation and the flat strip is positioned closer relation
alongside the excavation.

NOTE: A competent assistant should be provided for working with the backhoe at any time.
Until the pipe is exposed by hand, the backhoe must be held parallel and close to the pipe, cable and other hazards buried.

NOTE: A supervisor or a representative of the designated work site must direct the work of the excavator machine at the site of work.
Stripping of topsoil

• Before excavating in an area of ​​work, all the topsoil must be stripped and stored on site, in locations selected by the company.

• During stripping operations and storage, the contractor shall ensure that the subsoil and topsoil are not mixed.

• The topsoil should not be stripped when wet (saturated)

The Excavation Excessive valve on Foundations, the Pipe and Installation

• Excavations must be carried out according to the elevations and dimensions shown on the drawings or adapted for installation which will be installed;

• Where the excavation of the foundations are laid below the levels shown on drawings, elevations, foundations should be corrected;

• The base of the excavation should be balanced, dry, and shall not contain debris and loose material, before proceeding with any other work;

• Excavations must be in more or less than 50mm of elevation indicated for general excavations.

• Excavations for footings and beams should be graduated in more or less than 25mm of elevation required, with tolerances to the formwork;

• Where excavations excess of 50mm granular lime elevation indicated should be provided to allow sufficient support for plants, pipe or valve.
 
Protection against collapse
There are three basic ways to protect workers against cave-ins of trenches:

• slope
• shielding
• Shoring

The most fatal crashes occur at odd jobs such as short-term connections and excavations for drains and sinks. Too often, people believe that this work is not dangerous enough to require safeguards against the collapse.