On brownfield sites it is often essential that the geotechnical solution for a site fully takes into account the identified pollutant linkages and selected reclamation strategy. The geotechnical solution for a site should not be considered in isolation. An example of this is the re-engineering of weak near surface natural strata and Made Ground to support raft or ring-beam spread footings as an alternative to a piled foundation solution or vibro-replacement where the penetration of a an aquiclude could result in the creation of an unacceptable vertical migration pathway to an underlying aquifer for contaminants. Applied Geology’s extensive experience in both geotechnical and contaminated land disciplines enables it to provide an integrated approach to the solution of ground related problems.
Case Study 1
Applied Geology was asked to undertake a Phase I Geoenvironmental Site Assessment of some land near junction 24 of the M5, near Taunton for a proposed new dairy complex. The Phase I developed a Conceptual Model for the site and subsequently allowed a Phase II investigation to be designed and costed.
The Phase I Study suggested the site was greenfield with no identifiable pollutant linkages and hence the Phase II Investigation was designed to confirm this and to provide data for the foundation, pavement and earthworks design aspects.
The fieldwork comprised a series of trial pits followed by both cable percussion and rotary cored boreholes and did indeed confirm the greenfield nature of the site. This work allowed Applied Geology to recommend both a near surface bearing pressure within the weathered rock and a higher pressure within the more intact rock at depth. Initially a piled foundation was considered necessary but the higher allowable bearing pressure quoted at depth by Applied Geology was deemed by the engineer to be suitable for his loading regime. It was however agreed that an inspection of all foundation bases was essential to ensure that the intact rock was indeed exposed.
To this end Applied Geology developed, in conjunction with the contractor’s site team, a method of ensuring this minimum strength by visual inspection and simple control using an in-situ vane. Where the founding stratum was not of the required quality, it was deepened until it met the required criteria.
In addition to this Applied Geology also assisted the engineer in the design of his construction mat as well as the outline parameters needed for the earthworks element of the groundworks.
Case Study 2
In March 2007 Applied Geology was asked to undertake a Phase I Geoenvironmental Site Assessment and a Phase II Geotechnical Site Assessment with particular regard to slope stability and the re-use of soils in earthworks for a site near the Tunstall junction of the A500 in Stoke upon Trent for a proposed new distribution warehouse and office complex. The Phase I developed a Conceptual Model for the site and subsequently allowed a Phase II investigation to be designed and costed.
The Phase I study suggested that the site had a complex industrial history including former tileries, coal mines and shafts, brickworks, clay pits, farms, railway sidings and a coal disposal depot. Historical records indicated several areas of infilled clay pits across the western area of the site. The site was known to be underlain by areas of deep Made Ground, Alluvium, Etruria Marl and Coal Measures and sloped steeply from north to south. The projected development consisted of reprofiling the slope to allow two level platforms with slopes upto 23m being cut and fill levels of up to 4m and hence the Phase II investigation was designed to confirm this and to provide data for the foundation, slope stability, pavement and earthworks design aspects. Additional monitoring and sampling was undertaken to address the geoenvironmental aspects in conjunction with another consultant.
The fieldwork comprised a series of trial pits followed by both cable percussion and rotary cored and open boreholes and was undertaken working closely with an ecological consultancy to ensure that the resident amphibian, mammal and avian populations were not significantly disturbed. This work allowed Applied Geology to work closely with its sister company Enverity in scheduling geotechnical testing to characterise the soils on site and derive design factors for the slope stability assessment and earthworks suitability assessment.