Geotechnical Services
A geotechnical investigation including preliminary foundation design is a requirement of the NHBC warranty.
Crofty Consultancy offers a range of geotechnical services to the construction industry and small builders alike.
We can carry out this work during contamination and mining investigations, effectively moving preliminary groundwork forward into the phase of work normally carried out as part of planning conditions.
We tailor geotechnical site investigations to meet specific project requirements. Our experienced engineers and technicians are well versed in gathering the highest quality data from the site visit.
Percolation Testing
Sustainable Urban Drainage Systems (SUDS) are fast becoming a requirement of a planning application. We can offer a range of tests to establish the feasibility of a soakaway on your site and give a Soil Infiltration Rate Value (SIRV).
Pit Soakaways. Pit soakaways are the most common type of soakaway we are asked to test for. These tests are performed in accordance with BRE Special Digest 365, and are normally undertaken concurrently with a Geotechnical or Environmental Site Investigation. The test gives an infiltration rate value for the soil, in l/m2/s for you to base your design upon.
Field Drains. Where soakage is poor we can undertake soakage testing for field drains. This is in accordance with BS 6297.
Surface infiltration tests. In some circumstances, a two-dimensional surface infiltration test is required. We can undertake this using the ‘two ring test’ method.
Road & Pavement Design
We can undertake a range of tests to enable the design of roads and pavements. The two tests we commonly use are:
CBR tests (In situ or ex situ) at a pre determined depth.
Dynamic Cone Penetrometer (Gives a CBR profile over a range of depths).
Foundation Design
Most developments will require a foundation design. We design for sites ranging in size from single house developments to 25+ hectare brownfield development sites.
Our design process always starts with a comprehensive site investigation. We use numerous techniques to gather as much data as possible on the site. Our highly trained staff will supervise the works, and log the soils where intrusive holes are excavated. We perform a number of in situ tests to measure ground strength. Once the fieldwork is complete, we assess the data and where possible provide information on the ground bearing pressure. We can also draft a preliminary foundation design including information such as foundation type, dimensions, and the predicted settlement. This is based upon loading strengths, which should be provided by the client.
Slope Stability Assessment
We can undertake both Phase 1 and Phase 2 slope stability assessments.
The Phase 1 Assessment involves visiting the site, and undertaking a walkover survey. We look for changes in slope angle, tension cracks, movement to trees and structures and any other signs that might indicate that a slope failure may have taken place.
The Phase 2 Assessment involves a site investigation, which may include a full topographical survey, borehole excavation, trial pitting, laboratory testing, and installation of piezometers and inclinometers. The data gathered from the site investigation is then used, in conjunction with a computer analysis programme to establish the factor of safety for the site. At this stage, remediation measures are recommended, if required.
