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KNOWING THE OPERATION

Part of developing a successful project plan and then managing it as well as a project budget - is understanding the sequence of activities applicable for a particular job site and optimizing the site logistics to reduce the cycle time and ensure continuity of work. 

Let us briefly touch upon a few basics that hold good for all Diaphragm Wall job sites :

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  1. Minimum walling area for economic feasibility of Diaphragm Wall operation : 1200 m2;

  2. Target productivity : min. 90 m2 /grab/work-day or 50 m3/grab/work-day;

  3. Mobilization and Installation cost (upto 200 miles) : min. $ 170,000.00 / grab ,  $20,000 for every additional grab;

  4. Daily operational expenses : min. $ 4400/day or $ 220/m3 excavated;

  5. Daily fuel consumption : 1200 L/day (for grab carrier + crawler crane + diesel generator + air compressor);

  6. Power requirement : 90 kWh;

  7. Water requirement : 15 m3/h;

  8. Each primary panel can end up requiring at least 15t of rebar and 18 m3 of concrete. Hence, site logistics and concrete batching is highly critical to ensure timely completion of activities;

  9. Quality Control esp wrt verticality, dimensions, slurry, concrete and blockout positions is highly critical to the success of the system;

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The following videos try to depict :

  1. An interview cum short documentary on setting up a Diaphragm Wall unit on a constricted job site in Australia;

  2. A timelapse of a construction job site depicting the need for site logistics planning in a dynamic setting where plants and equipment are always on the move;

  3. The Quality control measures which are adopted in major projects (The rehabilitation of Sylvenstein Dam, Bavaria by BAUER);

  4. The scope for innovation in terms of incorporating parametric modelling and pre-fabrication on a job-site

Management & Safety: Watch
Management & Safety: Watch
Management & Safety: Watch
Management & Safety: Watch

JOB SAFETY

No matter how many trenching, shoring, and backfilling jobs an employer has done in the past, it is important to approach each new job with care and preparation. Especially during the first 5m of excavation depth, where utility lines and temporary structures are mostly housed, the risk is immense. Any job site should be ready to deal with any safety hazard and the following basic practices can go a long way in ensuring safe working conditions :

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  1. Heavy Equipment Operators (for grab carriers) and Cranes and Derricks Operator to be certified as per the local DoT and OSHA;

  2. Provide a warning system (such as barricades, hand or mechanical signals, or stop logs) when mobile equipment is operated adjacent to an excavation, or when such equipment must approach the edge of an excavation, and the operator does not have a clear and direct view of the edge;

  3. Ensure that any worker who works near the guide wall wears a harness with a lifeline. The lifeline must be attached securely to the harness and must be separate from any line used to handle materials. Also, the lifeline must be individually attended by an observer at all times when the worker wearing the lifeline is descending within the trench;

  4. Know where underground utilities are located before digging;

  5. Keep excavated soil (spoils) and other materials at least 2 feet (0.61 meters) from trench edges;

  6. Keep heavy equipment away from trench edges;

  7. Walkways shall be provided where employees or equipment are required or permitted to cross over excavations. Guardrails which comply with §1926.502(b) shall be provided where walkways are 6 feet (1.8 m) or more above lower levels.

  8. Identify any equipment or activities that could affect trench stability;

  9. Test for atmospheric hazards such as low oxygen, hazardous fumes, and toxic gases when workers are more than 4 feet deep;

  10. Inspect trenches at the start of each shift;

  11. Inspect trenches following a rainstorm or other water intrusion;

  12. Inspect trenches after any occurrence that could have changed conditions in the trench;

  13. Do not work under suspended or raised loads and materials;

  14. Ensure that personnel wear high-visibility or other suitable clothing when exposed to vehicular traffic

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While OSHA doesnot have specific guidelines related to Diaphragm Wall construction , the following video by the Association of Soil and Subsoil Technology COMPANIES

Management & Safety: Watch
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