Contractors field trials

The consolidation rate can be accelerated by installing prefabricated vertical drains. The design of the vertical drain system is usually the responsibility of the Contractor, since it is related to the adopted construction program. Sometimes the drain spacing (triangular or rectangular) and depth are specified in Contract documents. Since the performance of a vertical drain system is not accurately predictable, field trials are recommended. Sufficient time for such trials should then be foreseen in the project schedule or executed before tender stage. 

If a ground densification technique is to be adopted to meet the performance criteria detailed herein, for each particular type of ground densification, prior to the main ground densification a preliminary field trial shall be carried out. Each trial area shall be of minimum plan dimensions of 10 metres by 10 metres and the location of the preliminary field trial shall be agreed between the Engineer and the Contractor. 

If the trial is planned through the services of a contract research company, their estimate should include a time and cost accounting which specifies the exact services they will perform for the trial. Services not included are the responsibility of the Study Director and sponsor. When contracting out a field residue study, the contractor s cost estimate will only be a part of the total cost to the sponsor. Make sure that costs... 

The area identified in the stores area of the north field compound was stripped of existing hardcore to expose the sub-grade, which was sandy and similar to that in the rest of the north field. The area was trimmed to level, compacted and inspected by all parties (the contractor, WRAP and the technical gioup fiom Coventry University). Figures 99 and 100 show the preparation of the trial area using Skanska s heavy excavator. 

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