Engineered hardstanding, crane pads and skid landing areas

How does Engineered hardstanding, crane pads and skid landing areas work, step by step?

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   Step 1: Start from the lift plan and the delivery schedule

   The hardstanding design follows the lift plan. The appointed person and the temporary works designer between them establish what is being lifted, from where, by what crane, in what configuration and in what sequence. That determines where crane positions are needed, what loads arrive at the ground and for how long. On most projects the delivery schedule then fixes the order in which the areas are built, because a crane pad needed in the first delivery window has to exist before one needed six months later.

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   Step 2: Design the platform against the ground investigation

   The temporary works designer takes the ground investigation and designs the platform: thickness, material grading, any geogrid or geotextile reinforcement, and the formation preparation beneath it. Reclaimed and filled ground normally needs more than people expect. Where the water table is high or the fill is variable, the design may include ground improvement or a piled solution beneath the crane position. The output is a drawing and a certificate, not a verbal instruction to the groundworks foreman.

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   Step 3: Check proximity to excavations, services and piles

   Crane positions on a plant site are rarely in open ground. They sit next to piled foundations, over buried service corridors, alongside open excavations and near drainage runs. The designer sets stand-off distances from open excavations and checks the imposed loads against anything buried. On most projects the buried services are proven by survey and trial holes rather than trusted from a drawing, because these sites frequently contain services left by a previous occupier.

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   Step 4: Prepare the formation and build the platform

   The formation is stripped, proof-rolled and inspected before any fill is placed. Soft spots are dug out and replaced rather than bridged. Fill is placed in layers, compacted and tested to the specification, with geogrid installed where the design calls for it. The platform is graded to shed water, because a platform that ponds loses strength exactly where the crane needs it. Records of layer thickness, compaction and testing are kept as the platform is built.

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   Step 5: Certify the platform and control access to it

   The completed platform is inspected against the design and certified in writing before any crane tracks on. The certificate names what it covers and what loads it was designed for. On most projects the platform is then re-inspected at agreed intervals and after any heavy rainfall, and re-certified after repair. Rutting, ponding and edge damage are the early signs that a platform is degrading, and the recorded fatal accidents in this area involve platforms that were adequate on day one and were never looked at again.

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   Step 6: Build the skid landing and move-in surfaces

   The areas where packaged units are landed and moved into final position are built to a level tolerance as well as a strength requirement, because the package will be skated or jacked across them into a bolt group that cannot move. The surface is designed for the jacking and skating loads, which are concentrated and mobile rather than static. Falls are set so water runs away from the landing position, and the surface is protected from other site traffic once it is complete.

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   Step 7: Provide drained laydown for packages awaiting installation

   Packages frequently arrive before the foundation that will receive them is ready. Laydown areas are therefore designed for the storage loads, drained so units do not stand in water, and set out so that a package can be picked up and moved without double handling. On most projects the technology supplier states storage and protection requirements for its equipment, and the laydown design has to satisfy them or the supplier's warranty position changes.

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   Step 8: Convert construction areas to permanent hardstanding

   Once the lifting is finished, many of these areas become permanent operational access, parking and maintenance hardstanding. Where that is known from the outset the designer normally specifies the permanent construction from the start and uses it through the build, which avoids building twice. Surfaces are then repaired where construction has damaged them, final falls and drainage connections are completed, and markings and demarcation are applied to the operational layout.