Site Investigation and Foundations for Watermead Business Park, Leicestershire - Coursework Example

1. Salient Features of the Facility The Watermead master plan allows design and build opportunities at the derelict land. The site lies near the highway with Leicester and Nottingham as nearest major metropolitan areas. An aerial view of the site indicates land that has been levelled. Most of the surface area is barren indicating previous surface activity. There is little vegetation at the site periphery indicating that portion of the site free from previous activity. Adjacent land houses buildings with industrial activity. A four level stadium has been envisaged at the site. 2. Site Conditions Watermead is brownfield land. The derelict land could be redeveloped after chemicals/waste, derelict infrastructure, or instability problems have been removed. Redevelopment of brownfield requires planning where economic benefit is linked to environmental enhancement. An independent investigation is required to determine the site history and impact of former activities on the status of subsurface soils and groundwater. This is required for appropriate management of risk by the identification of potential environmental risks and associated liabilities at an early stage (UK Land Directory, 2009). Figure 1. Watermead Business Park Masterplan (Raynsway Properties, 2009) The Association of Geotechnical and Geoenvironmental Specialists (2005) have recommended a four phase approach to site investigation. The first phase includes gathering information from available records. This includes records such as road names, maps, published documents, aerial photographs, utility company records, interviews, and information from contacts, etc. A review of records enables the development of appropriate hypothesis about the site. This includes past and present land use, geology, surface and groundwater environment. The second phase is a limited ground investigation for appraisal of the site and suitability for development. This includes boreholes, trial pits, penetration tests, laboratory tests and geophysical methods. The ground investigator prepares the report, while the advisor sets out the hypothesis and conclusions. This allows identification of problem areas for further additional investigation and consideration. Phase three includes main or extensive ground investigation. This allows addressing or clarification of particular technical requirements or problem areas. Based on the factual report the advisor prepares an interpretative report with information on soil properties, and guidance on design and construction. Phase four includes the collection of information and its appraisal. This phase should continue during construction works for confirming the assumed ground model. Construction period is an important phase of the investigation. The model of the ground should be continually updated as more is revealed by excavation, piling or monitoring. Kruse (2006) has suggested soil testing as described in BS 5930:1990 to describe and classify samples. Soil testing allows determination of the most appropriate method for analysis and obtains soil parameters that are technically relevant. Laboratory tests include: moisture content along with liquid and plastic limits; classification of fine grained or mixed soils; particle size distribution giving relative proportions of gravel, sand, slit and clay; organic matter; mass loss of ignition; sulphate content; pH value; California bearing action; soil strength tests; soil deformation tests; and soil permeability tests. A standard description contains: mass characteristics with state and structure; density or compactness or field strength, discontinuities, bedding; material characteristics with nature and state; colour, composite soil types, and principal soil type; and stratum name including geological formation, age and type of deposit, and classification. Groundwater flow information would help decide the ideal locations and depths for monitoring wells. In a phased approach flow patterns are established and further monitoring wells could be installed where they could produce useful information. In the absence of clearly defined source monitoring wells should be installed on a non-targeted basis. If there is a potential for gas contamination, its composition and migration potential should be determined. Contaminated sites should be dealt with BS 10175:2001. The model should be tested with an intrusive ground investigation. Ground investigation and chemical testing provide whether supplemental investigation has to be carried out for delineating areas of contamination and address technical matters concerning remediation. Geoenvironmental sampling is conducted simultaneously with geotechnical sampling during excavation of trial pits. Window samplers could be installed in addition to sampling. Light cable percussion boreholes allow integrated sampling. On-site testing allows determination of groundwater and/or ground gas characteristics, while off-site testing allows testing for a whole suite of chemicals. 3. Technology for Construction of Foundation System A project has been planned at the derelict land. This includes a major international stadium with state-of-the art facilities. The facility would have four levels. The ground floor would house sporting facilities, service facilities, and other associated facilities. The first level would house VIP facilities. The second, third, and fourth facilities would house facilities for visitors, guests, and recreation activities. Bristol City Football Club (2009) found that trial pits in the area would influence the choice of planning strategy. A significant portion of the existing material would be excavated, moved and reworked to achieve a certain level of development of platform to construct the foundation for the stadium. It is likely that the land, underlying surface is not suitable to be used as a founding stratum in the current condition. Ground improvement techniques should be deployed for improving the engineering properties of the made ground, as the ground is anticipated to support only very light loads. The primary loads associated with the stadium being sufficiently large would not allow natural or improved shallow soils to provide adequate foundation potential (Riley and Cotgrave, 2004). All foundation loads would be transferred to suitable surface underlying at the site, which could be several meters deep. A range of pile foundations should be considered including driven precast concrete, hybrid driven cast insitu, or cast insitu continuous flight auger piling. When time is of essence a driven precast concrete pile solution should be preferred. Also, it offers other advantages such as ease of driving through the landfill materials or absence of significant arisings for disposal. Figure 2. Excavating Test Pit and Cable Percussion Rig (Kruse, 2006) Figure 3. Test Pit (Kruse, 2006) Figure 4. Excavation (Western Builder, 2002) The construction of the Olympic Stadium has been illustrated in figures 2-3. Approximately 800000 tonnes of soils was excavated from the Stadium area to create the Stadium bowl. 6,500 m3 of crushed concrete has been spread on the top of the soil forming a solid platform for construction. The concrete was recycled from other parts of the Park. 4,000 concrete columns would be inserted or cast into the ground to reinforce the area where the Stadium will sit. This forms the first step in the construction of the sub-structure, which forms the foundation for the Stadium structure. Figure 5. Olympic Stadium Site in April 2007 (Olympic Delivery Authority, 2008) Figure 6. Olympic Stadium Site in March 2008 (Olympic Delivery Authority, 2008) Floor slabs are being laid at the base of the bowl and lower tier structures. This would be followed by columns for supporting the pedestrian concourse. This would be followed by the construction of steel structures for supporting the stadium roof (Olympic Delivery Authority, 2008). Figure 7. Construction of Foundation (Olympic Delivery Authority, 2008) Soil stabilization system provides foundation support in organic of other unsuitable soils, penetrating high water tables, while eliminating the risk of undermining foundations of adjacent buildings (Chudley and Greeno, 2006). Alternatives include soil replacement, sugur-cast piles, or soil reinforcement systems. Deep foundation system is an alternative. Driven piles have the risk of vibration and settlement risk on adjacent foundations (Emmitt and Gorse, 2006). Soft organic soils and high water table could be addressed by piers with temporary steel casing. Holes could be augered through a casing and the casing could be withdrawn as the gravel is rammed into the shaft (Western Builder, 2002). Figure 8. Pier Construction (Western Builder, 2002) The Manchester Stadium had boreholes that were 85 m deep along with trial pits and in situ testing. Landfill gas and groundwater installations were monitored and samples were tested for geotechnical and chemical properties. There were geological succession made of 2-3 m made ground with 7-15 m clay deposits above coal measure rocks. Ground characteristics were granular and cohesive with variable densities and length. The groundwater was shallow. There were minor water entries in glacial deposits. The made ground had contamination of varying degrees with hydrocarbons, heavy metals, waste containing obstructions from previous foundations. Coal measures had alternating mudstones, siltstones, sandstones, and thin coal seams. Coal workings were collapsed when encountered. Groundwater was encountered below rockhead. Remedial works were carried out to mitigate abnormal features identified previously. There was large amount of earthwork to form the platform. A strategy adopted was to limit import of material and disposal offsite by maximizing re-use of excavated material. Approximately 250000m3 of material was excavated of which only 10% left the site. Most of the materials were used as fill or processed with concrete and brick crushed for capping and marginal material was treated with lime for stabilization (Manchester City Council, 2003). References Association of Geotechnical and Geoenvironmental Specialists. (2005). A Client’s Guide To Site Investigation. Available: http://www.ags.org.uk/site/clientguides/ClientsGuideSiteInvestigation.pdf. Last accessed 9 December 2009. Bristol City Football Club. (2009). Foundations Management Strategy. Available: http://e2edocs.bristol-city.gov.uk/. Last accessed 9 December 2009 . Chudley R. & Greeno R. (2006). Building Construction Handbook. Oxford: Butterworth-Heinemann. Emmitt S. & Gorse C. (2006). Barry’s Advanced Construction of Buildings. Blackwell. Kruse, F. (2006). Geotechnical and Geoenvironmental Jobs Resource. Available: http://www.bajr.org/Documents/GeoTec.pdf. Last accessed 9 December 2009. Manchester City Council. (2003). Designing the City of Manchester Stadium. Available: http://www.getyourkitsout.com/designing%20the%20COMSTAD.pdf. Last accessed 9 December 2009. Olympic Delivery Authority. (2008). Start. In: London 2012. London. 7. Raynsway Properties. (2009). Masterplan. Available: http://www.watermeadbusinesspark.co.uk/masterplan/index.php?cat_id=12. Last accessed 9 December 2009. Riley M. & Cotgrave A. (2004). Industrial and Commercial building: Basingstoke UK Land Directory. (2009). Brownfield Land Development Information. Available: http://www.uklanddirectory.org.uk/brownfield.asp. Last accessed 9 December 2009. Western Builder. (2002). Scratching the Surface. Available: http://www.geopier.com/uploadedFiles/WesternBuild_503.pdf. Last accessed 9 December 2009. Read More