THE EQUIPMENT

A typical Diaphragm Wal construction operation employs equipment which can be broadly classified into the following heads :

1. Trenching Equipment;

2. Lifting Equipment;

3. Miscellaneous Equipment

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Although the equipment are important to the success of the operation, the Diaphragm Wall Grabs in particular are the heart and soul of the operation.

TRENCHING EQUIPMENT

The principal equipment used in the trenching process are crawler rigs mounted with the following :

1. Reverse mud circulation jig;

2. Mechanical clamshell grab;

3. Kelly clamshell grab;

4. Hydraulic clamshell grab;

5. Hydrofraise or Hydromill cutters.

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Incidentally, these equipment are also the most expensive and repair cum maintenance intensive.

LIFTING EQUIPMENT

The principal equipment used in the lifting process are :

1. Crawler cranes with a derrick or telescopic boom;

2. Gantry cranes;

3. All terrain Mobile cranes.

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Incidentally, these equipment are also the largest and riskiest on the job site.

MISCELLANEOUS EQUIPMENT

As compared to the trenching and lifting equipment, some of the miscellaneous equipment are in continuous use throughout the work day and hence are sometimes more critical to the success of the operation than the others. Some of these "critical" equipment are :

1. Bentonite Slurry plant;

2. Desander plant;

3. Tremie pipe assembly;

4. Rebar cutting and bending machines;

5. Welding machines;

6. Pneumatic pumps;

7. Diesel generators;

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The importance of spares cannot be emphasized enough. 

PRODUCTIVITY

• Productivity range : 80 - 150 m2/grab/work-day;

• Use one grab for a job size of upto 1200 m2 and add one for every 2000 m2 thereon;

• Employ a chiseling attachment to increase productivity by 10% in soild of SPT > 30 

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EQUIPMENT SPECIFICATION

The following are minimum equipment specifications of the required to achieve the target productivity as discussed earlier :

1. Power of Grab Carrier : 250 hp;

2. Capacity of Crawler Crane : 75 t;

3. Closing force of Grab : 900 kN;

4. Track width : 500mm