Q1.define

a) Sloping and Benching Systems

1. A sloping system means a method of protecting employees from cave-ins by excavating to form sides of an excavation that are inclined away from the excavation so as to prevent cave-ins.

2. The angle of incline required to prevent a cave-in varies with differences in such factors as the soil type, environmental conditions of exposure, and application of surcharge loads. Use charts and tables to determine the angle of incline.

3. The 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 expresses as the ration of horizontal distance to vertical rise (H:V). This varies according to the soil type which can be classified by a competent person. See Table 2 for the maximum allowable slopes.

4. The actual slope shall never be steeper than the maximum allowable slope. When there are signs of distress, the slope shall be cut back to an actual slope which is at least ½ horizontal to one vertical (1/2H:1V) less steep than the maximum allowable slope.

5. A benching system means 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 nearvertical surfaces between levels.

6. The length of the vertical sides of a benching system and the maximum allowable slope required to prevent a cave-in varies with differences in such factors as the soil type, environmental conditions of exposure, and application of surcharge loads. Use charts and tables to determine the length of the sides and the maximum allowable slope.

7. It is always better to over-compensate and make the angle flatter.

b) Riggers-

A rigger is a person that specializes in the lifting and moving of extremely large or heavy objects, often with the assistance of a crane or derrick

There are a number of different categories of riggers working in several industries. In the military, riggers are responsible for maintaining and setting up things like parachutes or airdrop equipment. In the theater industry, riggers manage pieces of a stage set, moving props and changing production scenes. Riggers in the marine industry are involved with setting up the pieces of equipment necessary to keep the ship functioning: ropes, pulleys, winches, and cables.

Most commonly, however, jobs are found within heavy construction, often in the oil or mining industry. This type of rigger is also referred to as a rig technician. In the oil industry there are several levels of rig technicians, ranging from motorhands to derrickhands to drillers, depending on skill level and job duties. Riggers in this industry are responsible for attaching pieces of heavy machinery, connecting the parts together and anchoring pieces to fixed structures with bolts and clamps. They also control and manage all the movement of the machinery while it is operational, and then take it all apart when the job is finished.

A rigger in the oil extraction industry usually works on drilling rigs. Equipment on the rig is used to bore a hole deep into the earth with the drill pipe. The rigger manages all aspects of the machinery used and monitors the rig operation. His responsibility is to ensure that the oil is being pumped out at a safe level so pipes do not burst. When oil is transported to a tanker, the rigger fits and links all the pipes together.

Some other specific job duties include:

maintaining drilling rig engines and motors, including the fluid systems managing hydraulic and mechanical systems for the whole drilling assembly ensuring proper fluid and fuel balance and making sure pressure is always maintained at a safe

level controlling and monitoring the safe movement of heavy equipment mobilizing the rig by setting it up tearing the rig down when the job is finished making sure all safety regulations are followed

Heavy construction riggers also work with cranes, and are responsible for setting up all the pulleys and cable systems that are used to move large and heavy objects. They must communicate with crane operators to guide them in moving objects and depositing them in the correct location. This can involve hand signals, radio operation or other communication. Working in a mine might involve setting up scaffolding and assembling equipment. Riggers are in particular demand during the shutdown and mobilization period, assisting with the safe tear-down of all the equipment and making sure it is all safely put back together again when operation resumes.

c) Dangerous occurrence: a dangerous occurrence can be defined as “any incident that has a high potential to cause death or serious injury” and are specified by the Reporting of Incidents, Diseases and Dangerous Occurrences Regulations 1995

You must report any work related incident that causes harm, or could have caused harm.

Also, the information may be used to defend a claim for damages, which may occur several years after the incident. It is therefore important to have a written record of what happened and what was in place.

Several types of dangerous occurrence require reporting in circumstances where the incident has the potential to cause injury or death. This assessment does not require any complex analysis, measurement or tests, but rather for a reasonable judgement to be made as to whether the circumstances gave rise to a real, rather then notional, risk. Such judgement allows for prompt reporting, and ensures that valuable information is not lost.

Schedule 2 lists three kinds of reportable dangerous occurrence:

1. General (incidents occurring at any workplace)

These dangerous occurrences apply to all workplaces and include incidents involving, lifting equipment, pressure systems, overhead electric lines, electrical incidents causing explosion or fire, explosions, biological agents, radiation generators and radiography, breathing apparatus, diving operations, collapse of scaffolding, train collisions, wells and pipelines or pipeline works.

2. Incidents occurring at any place other than an offshore workplace

These incidents do not require a report if they occur at an offshore workplace. They include structural collapses, explosions or fires, releases of flammable liquids and gases and hazardous escapes of substances.

3. Incidents occurring at specific types of workplace

Industries with specific requirements are: offshore workplaces, mines, quarries and relevant transport systems.

d) Type B soil is:

a. Cohesive soil with an unconfined compressive strength greater than 0.5 tons per square foot, but less than 1.5 tons per square foot.

b. Granular cohesionless soil including: angular gravel, silt, silt loam, sandy loam and, in some cases, silty clay loam and sandy clay loam.

c. Previously disturbed soil except that which would otherwise be classed as Type C soil.

d. Soil that meets the unconfined compressible strength or cementation requirements for Type A, but is fissured or subject to vibration.

e. Dry rock that is not stable.

f. Material that is part of a sloped, layered system where the layers dip into the excavation on a slope less steep that four horizontal to one vertical, but only if the material would otherwise be classified as Type B.

Q2.Proper Lifting 1. Plan your move.

Size up the load and make sure pathway is clear. Get help as needed.

Use a dolly or other device if necessary.

2. Use a wide-balanced stance with one foot slightly ahead of the other.

3. Get as close to the load as possible.

4. Tighten your stomach muscles as the lift begins. When lifting, keep your lower back in its normal arched position and use your legs to lift. Pick up your feet and pivot to turn – don't twist your back.

5. Lower the load slowly, maintaining the curve in your lower back. Your back can manage most lifts – if you lift correctly. Avoid lifting above shoulder height. This causes the back to arch, placing heavy stress on the small joints of the spine. Do not catch falling objects. Your muscles may not have time to coordinate properly to protect the spine.

The hazards associated with improper manual material handling are associated with:

Struck by a load Losing control of a load Physically over exerting oneself Exceeding equipment capacity Improper posture Inappropriate house keeping

Such accidents can lead to:

Small injuries Major injuries Musculoskeletal disorder Loss of life

Q3. Conveyors

As with any mechanical and electrical device, conveyors can present some safety concerns. Since they have many moving parts, anyone who works on, near, or around them should be well versed in conveyor safety and also why each rule is important and necessary

Safety issues while working with conveyors

Do not climb, sit, stand, walk, ride, or touch the conveyor at any time:

Not following this rule can lead to injury, and it happens more often than you would like to believe.

It's imperative that workers never climb, sit, stand, walk, ride or even touch the conveyor line at any time.

It's common sense, but people tend to get mischievous about it and there are injuries and equipment damage due to not following this rule every year.

Do not perform maintenance on conveyor until electrical, air & hydraulic energy sources have been locked out or blocked :

It is plain old common sense to follow this rule. Don't perform any maintenance (or even open a panel or guard) until electrical, air, or hydraulic power sources are disconnected or blocked out. There are technicians who sometimes become too confident in their ability to work on machinery even when it's connected to power because they have been around it a long time and know it well. It's this kind of thinking that can lead to injuries.

Operate equipment only with all approved covers and guards in place:

They built the conveyors with guards for a reason - safety! Operating it without the guards is one of the most unsafe, and sadly, most common occurrences in the industry.

Guards are sometimes removed by plant employees for maintenance, or because they obstruct someone's access doing work. This exposes machinery, gears, chains, and moving parts that are extremely dangerous if left unguarded

Do not load a stopped conveyor or overload a running conveyor :

Workers shouldn't ever load a conveyor when it's stopped, or overload it when it is running.

This simple safety standard helps preserve your conveying equipment because it helps prevent overheating.

Ensure that all personnel are clear of equipment before starting :

Workers should always be certain that everyone is clear of the conveyor before starting it up.

Many times, factories install warning horns to alert workers that the conveyors are about to become active. This is an excellent, and relatively inexpensive safety upgrade you can make, but you shouldn't stop there. Training should also be included about what the warning horn means and how injuries can occur if it's ignored

Allow only authorized personnel to operate or maintain material handling equipment :

Only workers who have been trained should be permitted to operate and perform maintenance on conveyors.

This is for two reasons:

(1) Safety of the technician. Conveyors can be dangerous to those who do not thoroughly understand the equipment and how to safely work on it.

(2) Only trained personnel can really maintain a conveyor to perform at peak efficiency.

Do not modify or misuse conveyor controls :

Conveyor controls are not just on/off switches. They are any kind of electronic or mechanical devices used during conveyor operation.

These controls should never be modified for any reason by unqualified personnel.

Monitor your various controls to be sure no one has misused, modified, or disconnected them.

Keep clothing, body parts, and hair away from the conveyor :

It cannot be stressed enough how important it is to keep clear of conveying equipment while it is in operation. This is one of the most common ways to be injured around a conveyor.

Workers should keep their hands off of conveyors.

Those with long hair, loose clothes, or ties should be exceptionally careful (or should bind their hair and clothes before going near the machinery).

Ties should be thrown over the shoulder or tucked in. Long sleeves should be restrained or rolled up. Visitors to your plant should be briefed on safety and inspected for potential clothes or hair that could be caught before being allowed near the conveyor line.

Remove trash, paperwork, and other debris only when power is locked out and tagged out :

It's important that the area around your conveyors be kept clean and as free of dirt, oil, etc. as much as possible to insure the equipment continues to operate efficiently.

However, it is unsafe to do that cleaning and maintenance when the conveyor is powered and operating. Beyond that, you should familiarize cleaning crews with conveyor safety as well as your conveyor operators, pickers, packers, etc.

Ensure that ALL controls and pull cords are visible and accessible :

In case a conveyor needs to be stopped suddenly, all the controls and pull cords need to be easily accessible and plainly visible so that anyone working in the area can reach them.

Checklist

Guarding

SN Activity Yes NO

1.

2.

3.

4.

5.

6.

7.

8.

9.

10.

Are guards in place to prevent access to all dangerous areas during the conveyor system’s operation?

Are guards either permanently or securely fixed to ensure the guard cannot be altered or detached without the aid of a tool or key?

If a fixed barrier is not practicable, and access to dangerous areas is required during operation, is an interlocked physical barrier used?

Are nip points guarded?

Safe operating procedures

Are all stop/start controls and emergency stop switches clearly marked?

Are workers aware of the location of these?

Are these controls within easy reach for workers?

Is the conveyor locked-out or isolated before maintenance or clearing out is started?

The moving conveyor system

clean belts, pulleys, drums or troughs while the conveyor system is moving?

carry out repair or maintenance on the conveyor system while it is moving

11.

12.

13.

14.

15.

16.

Training

the correct method for stopping and starting the conveyor system?

the hazards from being inattentive or not following safe work procedures?

Starting the conveyor

access platforms are clear?

emergency stop switches are working and clearly marked?

lights are working and clean?

Q4. Lifting Tackle: Just like lifting machinery, lifting tackle such as chains, chain slings, ropes, straps, shackles and hooks must also be subjected to a load test. The load test must be done a competent person. In addition to the load testing all lifting tackle must be inspected by a competent person that has been appointed in writing at intervals not exceeding 6 months. The results of the annual load tests as well as the monthly inspections must be recorded in a register and such register must be kept up to date and be kept on the site were the tackle is being used. Lifting Tackle could be identified and color coded it in accordance with the monthly inspections. This will make it easy for supervisors, operators and workers to see if the most currently inspected tackle is used on site.

Tower Crane: Tower cranes are specialized machinery and form an integral and important part of many construction sites. A crane risk assessment must be conducted by an appointed competent person. Make sure that the crane is erected and used only as per the safe work procedures of the risk assessment, if not the crane could be very dangerous and could even collapse. It is the responsibility of the appointed operator to conduct visual inspections of the tower crane's structure whilst ascending and descending the crane's access ladder. The operator must record the findings of these inspections in a register and keep it on the crane. If any visible defects are noticed it must be report to the site supervisor or manager immediately. Care must be taken of the crane's electrical supply by making sure all the electrical-cables are secured and that the DB is closed and protected and sign posted with warning notices stating their presence. This will ensure good electrical safety when working with or around tower cranes. Bare wires or open, live DB's can be very dangerous. They can electrocute workers or be susceptible to rain and water damage creating a very dangerous environment.

Crane hooks must be pop marked and if the hook has opened beyond the safe limit the hook must be replaced. All hooks must be fitted with safety latches and they must be functional. Make sure the MML is displayed and that the limit devices for both the mass and wind overloads are operational at all times. Make sure the condition of the crane's access components have been checked. This will include the ladder, backrests and landing platforms. It is highly recommended that all crane access ladders be fitted with appropriate fall arrest systems. This will ensure ultimate safety for the operator.Make sure the cabin has been well constructed, not damaged and free from rust. Check the windscreen to make sure it is intact insuring visibility from the cabin is never impaired. The hooter and siren must be in working order.

Mobile Crane: The fundamental advantage of a mobile crane is its ease of transportation and its flexibility in handling different types of load or cargo quickly; this makes a mobile crane very useful and an ideal solution for work on a construction site.Here are the items one needs to check before using a mobile crane. Inspect the Rear view mirrors, Windscreen, Windscreen wipers and Indicators to make sure that they are fitted correctly, are in good condition and are operational. Hooters must be checked that they are working. Tyre condition and pressure must be checked on a regular basis while the all wheel nuts are fitted. Lights must be operational; it is important that headlights and taillights are in good condition. Inspect all grease nipples and all joints must be greased. There are to be no oil leaks, if any report it to the supervisor immediately. Hydraulic pipes must be in good condition, attachments in working order with no leaks. Do not operate the mobile crane if you see any hydraulic leaks! Battery condition must be inspected: Batteries must be secured, terminals secured and no corrosion present. The boom must be in good condition with no visible damage. If this is not the case, degradation and defects must be reported. Cable and sheaves must be greased, and they are to have no visible damage or corrosion. Any defects must be reported. Brakes must be checked to be in good working order. By-pass valves must be fitted correctly, securely mounted, functional and no leaks must be present. A Deflection chart must be fitted, in good condition and visible to the operator along with ASLI in working condition all the time. Outriggers' condition must be inspected, foot plates fitted correctly when used, when lifting. Do not use the mobile crane unless a risk assessment has been performed by a competent person on the outriggers and ground conditions on which the outriggers are going to be placed.

Gantry Crane: Gantry cranes are used to lift and move items around a working area, this makes them ideally suited for work in a factory, plant or machine shop.

The Gantry Crane must always, be in good working condition, load tested and inspected. The Gantry Crane's logbook must be kept up to date and available in the yard where it is used.

The operator must be trained and appointed in writing. Make sure the SWL is clearly displayed on the crane as well as the crawler beams.

The operator must at all times observe and adhere to the hand signals, given by the Rigger or Slinger. The area where there are Gantry Cranes in use must be marked with warning notices. Signage such as "Crane Overhead" must be strategically placed and in good condition as to ensure safety to those working in the area.

Make sure the hooks are throat pop marked, with the safety latch fitted and functional. Make sure load limiting switches are fitted and fully operational.

Checklist:

Inspection ItemTagged Crane or Hoist

Control Devices

Brakes

Hook

Hook Latch

Wire Rope

Reeving

Limit Switches

Oil Leakage

Unusual Sounds

Warning and SafetyLabelsHousekeeping andLighting

Description of Inspection Check PointsCheck that crane or hoist is not tagged with an out-of-order sign.

Test run that all motions agree with control device markings.

Check that all motions do not have excessive drift and that stopping distances are normal.

Check for damage, cracks, nicks, gouges, deformations of the throat opening, wear on saddleor load bearing point, and twist. Refer to the manual furnished by the original manufacturerof the crane.

If a hook latch is required, check for proper operation.

Check for broken wires, broken strands, kinks, and any deformation or damage to the rope structure.

Check that the wire rope is properly reeved and that rope parts are not twisted abouteach other.

Check that the upper limit device stops lifting motion of the hoist load block before strikingany part of the hoist or crane.

Check for any sign of oil leakage on the crane and on the floor area beneath the crane.

Check for any unusual sounds from the crane or hoist mechanism while operating the crane or hoist.

Check that warning and other safety labels are not missing and that they are legible.

Check area for accumulation of material, trip or slip hazards, and poor lighting.

Q5. INGRESS AND EGRESS for excavation: -

Access to and exit from the trench require the Following conditions: Trenches 1.5 M or more in depth should be provided with a fixed means of egress. Spacing

between ladders or other means of egress must be such that a worker will not have to travel more than 15 MT or fraction thereof in case of hazardous work & per 30 M of length in case of less hazardous work.

Another good safety practice is to ensure that ladders extend three feet above the surface of the excavation and be tied off if possible.

Laterally to the nearest means of egress. Ladders must be secured and extend a minimum of 1.0 mt. above the landing. Metal ladders should be used with caution, particularly when electric utilities are present

Requirements of Excavation Protective Systems: - TRENCHING PROTECTION

Sloping:- Sloping the walls is one way to keep a trench from collapsing. We cut trench walls back at an angle of 1-to-1 or 45 degrees. Or an angle produced from calculation from the design department that’s 1.0 meter back for each meter up. Walls should be sloped starting at 1.2 metres up the wall. Loose material or rocks must be removed from the face to ensure debris does not roll in on the Workers. Excavated soil cannot be placed closer than one meter from the edge of the cut.

Benching is similar to sloping with steps cut into sides of the trench

Shoring:- Shoring is a system which shores up or supports walls to prevent soil movement. It also helps to support underground utilities, roadways and foundations. The two types of shoring used most commonly are timber and hydraulic. Both consist of posts, wales, struts and sheathing. One major advantage of hydraulic shoring is that you don't have to enter the trench to install the system. Installation can be done from the top of the trench. Whenever possible, shoring should be installed as excavation proceeds. If there's any delay between digging and shoring, no one should enter the unprotected trench.

Trench Boxes:- Trench boxes aren't really meant to shore up or support trench walls. They're only meant to protect Workers in case of a cave-in. Boxes are capable of supporting trench walls if the space between the box and the trench wall is backfilled. Otherwise a cave-in or collapse may cause the trench box to tilt or turn over. It's also easier to enter the box if soil comes right up next to it. Trench boxes are commonly used in open areas away from utilities, roadways and foundations. As long as you're in the trench, you should stay inside the box and leave only when the box has to be moved.

SAFETY INSTRUCTION FOR EXCAVATION AND TRENCHING Any construction building worker engaged where in excavation is exposed to hazard of falling or

sliding material or article from any bank or side of such excavation which is more than one 1.5 m

above his footing, such worker is protected by adequate piling and bracing against such bank or side.

Where banks of an excavation are undercut, adequate shoring is provided to support the material or article overhanging such bank.

Excavated material is not stored at least 0.65 m from the edge of an open excavation or trench and banks of such excavation or trench are stripped of loose rocks and the banks of such excavation or trench are stripped of loose rocks and other materials which may slide, roll or fall upon a construction building worker working below such bank

Metal ladders and staircases or ramps are provided, as the case may be, for safe access to and egress from excavation where, the depth of such excavation exceeds 1.5 m and such ladders, staircases or ramps comply with the IS 3696 Part 1&2 and other relevant national standards.

Trench and excavation is protected against falling of a person by suitable measures if the depth of such trench or excavation exceeds 1.5 m and such protection is an improved protection in accordance with the design and drawing of a professional engineer, where such depth exceeds 4m.

Q6.

a). Loading and unloading operation at dock

Loading and unloading ships requires knowledge of the operation of loading equipment, the proper techniques for lifting and stowing cargo, and correct handling of hazardous materials. In addition, workers must be physically strong and be able to follow orders attentively.

In earlier days before the introduction of containerization, men who loaded and unloaded ships had to tie down cargoes with rope. A type of stopper is called the stevedore knot. The methods of securely tying up parcels of goods is called stevedore lashing or stevedore knotting. While loading a general cargo vessel, they use dunnage, which are pieces of wood (or nowadays sometimes strong inflatabledunnage bags) set down to keep the cargo out of any water that might be lying in the hold or are placed as shims between cargo crates forload securing.

b). Ropes or slings

Wire Rope

Many factors influence the selection of wire rope. Rope strength, although of major importance, is

only one factor. Pay attention to the other factors such as size, grade, type, and construction thatare specified by equipment or rope manufacturers who base their recommendations on actualworking conditions.

Always consider six basic requirements when selecting wire rope:1. The rope must possess enough strength to take the maximum load that may be applied, with adesign factor of at least 5 to 1 – and 10 to 1 when the rope will be used to carry personnel.2. The rope must withstand repeated bending without failure of the wires from fatigue.3. The rope must resist abrasion.4. The rope must withstand distortion and crushing.5. The rope must resist rotation.6. The rope must resist corrosion.

Procedures and Precautions with Wire Rope• Ensure that the right size and construction of rope is used for the job.• Inspect and lubricate rope regularly according to manufacturer’s guidelines.• Never overload the rope. Minimize shock loading. To ensure there is no slack in the rope, startthe load carefully, applying power smoothly and steadily.• Never use frozen ropes.• Take special precautions and/or use a larger size rope whenever- the exact weight of the load is unknown- there is a possibility of shock loading- conditions are abnormal or severe- there are hazards to personnel.• Use softeners to protect rope from corners and sharp edges.• Avoid dragging rope out from under loads or over obstacles.• Do not drop rope from heights.• Store all unused rope in a clean, dry place.• Never use wire rope that has been cut, kinked, or crushed.• Ensure that rope ends are properly seized.• Use thimbles in eye fittings at all times.• Prevent loops in slack lines from being pulled tight and kinking. If a loop forms, don’t pull it outunfoldit. Once a wire rope is kinked, damage is permanent. A weak spot will remain no matterhow well the kink is straightened out.• Check for abnormal line whip and vibration.• Avoid reverse bends.• Ensure that drums and sheaves are the right diameter for the rope being used.• Ensure that sheaves are aligned and that fleet angle is correct.• Sheaves with deeply worn or scored grooves, cracked or broken rims, and worn or damagedbearings must be replaced.• Ensure that rope spools properly on the drum. Never wind more than the correct amount of rope

on any drum. Never let the rope cross-wind

SlingsSlings are often severely worn and abused in construction. Damage is caused by:• failure to provide blocking or softeners between slings and load, thereby allowing sharp edgesor comers of the load to cut or abrade the slings• pulling slings out from under loads, leading to abrasion and kinking• shock loading that increases the stress on slings that may already be overloaded• traffic running over slings, especially tracked equipment.Because of these and other conditions, as well as errors in calculating loads and estimating slingangles, it is strongly recommended that working load limits be based on a design factor of at least5:1.For the same reasons, slings must be carefully inspected before each use..

Sling AnglesThe rated capacity of any sling depends on its size, its configuration, and the angles formed by its legs with the horizontal.For instance, a two-leg sling used to lift 1000 pounds will have a 500-pound load on each leg at a sling angle of 90°. The load on each leg will go up as the angle goes down. At 30° the load will be 1000 pounds on each leg!Keep sling angles greater than 45° whenever possible. The use of any sling at an angle lower than 30° isextremely hazardous. This is especially true when an error of only 5° in estimating the sling angle can be so dangerous.

Q7. Reasons of an accident due to “scaffold collapse during casting of concrete1. above scaffold capacity2. bamboo scaffold was not heat resistant3. defective wood planks4. Cross bracing not adequate 5. defective ropes6. improper structure7. unsuitable land8. unsuitable weather condition9. area of sole plate10. MASONRY BLOCKS & BRICKS NOT ACCEPTABLE AS SCAFFOLD BASE11. width of wood plank12. inspected by competent person

Q8. A cofferdam is a temporary structure designed to keep water and/or soil out of the excavation in which a bridge pier or other structure is built.

When construction must take place below the water level, a cofferdam is built to give workers a dry work environment. Sheet piling is driven around the work site, seal concrete is placed into the bottom to prevent water from seeping in from underneath the sheet piling, and the water is pumped out

The word "cofferdam" comes from "coffer" meaning box, in other words a dam in the shape of a box.

TYPES• Braced• Earth-Type• Timber Crib• Double-Walled Sheet Pile• Cellular

1.BRACED COFFERDAM• Formed from a single wall of sheet piling• Driven into the ground to form a box• around the excavation site• The "box" is then braced on the inside• Interior is dewatered• Primarily used for bridge piers in• shallow water (30 - 35 ft depth)

2.EARTH TYPE• It is the simplest type of cofferdam. • It consists of an earth bank with a clay core or vertical sheet piling enclosing the excavation. • It is used for low-level waters with low velocity and easily scoured by water rising over the top.

3. TIMBER CRIB• Constructed on land and floated into place. • Lower portion of each cell is matched with contour of river bed.• It uses rock ballast and soil to decrease seepage and sink into place, also known as “Gravity

Dam”. • It usually consists of 12’x12’ cells and is used in rapid currents or on rocky river beds. • It must be properly designed to resist lateral forces such as tipping / overturning and sliding

4. DOUBLE WALLED SHEET TYPE• They are double wall cofferdams comprising two parallel rows of sheet piles driven into the

ground and connected together by a system of tie rods at one or more levels.

• The space between the walls is generally filled with granular material such as sand, gravel or broken rock.

5. CELLULAR• Cellular cofferdams are used only in those circumstances where the excavation size precludes

the use of cross-excavation bracing. • In this case, the cofferdam must be stable by virtue of its own resistance to lateral forces.

Principal hazards and risks

falls from height from dam walls into excavation or into water health hazards from contaminated water, hazardous gases in confined spaces, noise and

vibration from piling operations hazards from services such as cables in river bed, temporary power cables in water etc contact with moving equipment such as collisions between boats, pontoons, crane barges and

cofferdam. moving plant and slewed equipment in confined space flooding caused by failure of cofferdam walls

Some design options to reduce hazards

consider a temporary causeway instead of floating rigs can prefabricated caissons towed into place be used instead of driven piled cofferdams to lessen

the work in the water and reduce the noise? consider the level of the working platform or causeway with respect to high tide and flood levels provide for structural enhancement to respond to adverse monitoring reports plan the shape of the cofferdam to suit working space and construction plant as well as final

structure consider the use of different construction or of remotely controlled techniques to design out the

need for underwater working incorporate lugs and holes in design to aid fixing of equipment

Q9. DOCK WORKERS (SAFETY, HEALTH AND WELFARE) REGULATIONS, 1990G.S.R 80 (E), dated 16th February, 1990.-Whereas the draft of the Dock Workers (Safety, Health and Welfare)

Regulations, 1987, was published as required by sub-section (1) of Sec. 22 of the Dock Workers (Safety, Health and Welfare) Act,makes the following regulations, namely:PART IGeneral1. Short title, application and commencement2.Definitions.3. Powers of Inspectors4. Notice of Inspection5. Appeal6. Penalties7. Responsibilities. 8. Exemption SafetyA.-Working Places9. Surfaces. -10. Fencing of dangerous places. -11. Passages to be kept clear.-12. Railings and fencings. -13. Staging construction and maintenance.-14. Work on staging.15. Lifesaving appliances. 16. Illumination.17. Fire protection.18. Excessive noise, etc.19. Construction.20. Floor loading.-21. Stairs. -22. Openings. -23. Means of escape In case of fire.24. Access between shore and ship.25. Access between ship and another vessel.26. Access between deck and hold.27. Fencing of and means of access to lifting appliances. 28. Ladders. 29. Bulwarks or rails. -30. Deck ladders. -31. Skeleton decks. -32. Working spaces. -33. Fencing around hatchways. -34. Hatch coverings, hatch beams, etc.-35. Opening and closing of hatches. -36. handling of hatch coverings and beams. -37. Securing of hatch covering and hatch beams. -38. Escape from holds. -39. Dangerous and harmful environment.-40. Construction and maintenance of lifting appliances41. Test and periodical examination of lifting appliances. -42. Automatic safe load indicators. -