Workingplatform are geotechnical structures which support the forces of heavy trackplants such as piling rigs and cranes providing a stable working platform over softsubsoils, this preventing failure or over-turning of the tracked plants. It isa foundation for large plants weighting in the region of 5 – 150 tonnes whichmost soils are unable to bare the weight. Theplatform needs to be of a certain thickness in order for the usage of heavytrack plant to be used and resist failure soil failure and overturning of theplants. It is constructed for the reduction of the ground pressure imposed onthe underlying soils, the material used are stronger than the formation. Inadequatedesign of working platform can result in dangerous accidents, delays in theprogrammes and damaging the reputation of the company. Hence, the workingplatform should be monitored and maintained throughout the duration of the useof heavy tracked plants to ensure failure doesn’t occur, the main contractor isresponsible for all of this. Acertificate has to be in place to confirm the platform has been adequatelydesigned and constructed in accordance with the design, and to ensure it willbe maintained throughout.
The main contractor must sign it and hand it to thepiling contractor prior to any piling or foundation works commencing. Thecertificate highlights the specific responsibilities, increases safetyawareness and the importance of maintaining the platform in good condition. Theuse of working platform certificated is to ensure correct measures have beenfollowed, the ground is sufficient to support the piling rig, there are noirregularities that could result in subsidence or toppling.
A daily check isrequired using checklist form to review the general condition of the platform. Consequently,a working platform is designed, constructed and maintained with use of the BRE-470.However, some users have reported that the thickness size given is unnecessaryand uneconomical which leads to additional expense. Groundsurface can deteriorate over time, trenches and excavations must beappropriately backfilled to avoid forming soft spots that will give away whenpiling rigs are on tracks. Thereare two types of working platforms which needs to be considered;· Permanent workingplatforms which are designed and built to be permanently integrated with thedesign of the structure which will be constructed. · Temporary workingplatforms which are designed and built as long as the work commence after theconstruction of the heavy tracked plants are completed the working platformsare dismantled. Therehave been numerous incidents which have occurred of piling rigs toppling, andresearch has indicated it is due to the isolated areas of weakness or theground collapsing beneath the platform due to exceeding the bearing capacity ofthe soil.
However,when constructing any type of working platform, a foundation is a necessity totransmit the load on a large area of soil. The foundation should be designedand constructed so the soil beneath does not fail in excessive settlement orshear. Bearingcapacity is the maximum load per unit area which the soil can take withoutyielding or displacing.
The resistance to deformation of the soil depends onfactor such as the water content, angle of friction, bulk density and thetechniques in which loads are applied on the soil.