Importance of the conceptual ground model; former Scrap Yard
Introduction:
We have been engaged to undertake a phased series of investigations combining a desk study, intrusive ground investigations and a consolidation assessment, to aid the design for this residential development in Pontarddulais (Planning Ref: 2018/1932/FUL). The development is being undertaken by Pobl.
Details:
We have been engaged to undertake a phased series of investigations combining a desk study, intrusive ground investigations and a consolidation assessment, to aid the conceptual ground model and design for this residential development in Pontarddulais (Planning Ref: 2018/1932/FUL). The development is being undertaken by Pobl.
Our assessment commenced with a detailed desk study, including a review of the site history and environmental context through to an assessment of the contamination risks posed to site end users, controlled waters risk assessment and a consolidation assessment for proposed land raising. Former uses include a foundry, a tin plate works, a scrap yard and railway land.
The conceptual ground model established identified the site to be underlain by variable thicknesses of Made Ground, Tidal Flat and Glaciofluvial Deposits. Land raising was required for a number of aspects of the design including flood protection, drainage and protection of site end users. Generally across the site, levels are to be raised between 600mm and 1200mm and the assessment commenced by zoning the site into three areas which were decided based on ground conditions, with each “zone” comprising varying thickness of Made Ground and/or soft compressible Tidal Flat Deposits.
The assessment considered the reaction of the in-situ soils to the increased overburden load, the additional live loading from foundations and the time frame in which the in-situ soils would react to the increased loading.
Dependant on the thickness of in-situ soils in each zone and the proposed land raising, settlement timings from around two weeks to three months were identified. It was concluded that settlement would occur and cannot be prevented, however, we identified measures which could be taken to mitigate risks to the construction programme and accelerate the settlement to within an acceptable time frame and this included the potential use of surcharging and wick drains.
As a result cost/time benefits and challenges are clear to the client and project team.