Events & Courses

Speaker: Andrew Farrant

Time: 18:55 for 19:00 start

Location: Virtual via Zoom

The Lower Thames Crossing is a new link between the M25 in Essex and the M2 in Kent, comprising 23 km of new roads and two 4.3 km tunnels beneath the River Thames. This will be the longest road tunnel in the UK. The variable geology and wide spatial extent of the Lower Thames Crossing scheme poses multiple geotechnical challenges. These include deneholes, compressible ground, karst features, faulting and variable rockhead. Accurately predicting ground conditions is critical for overcoming these issues and for optimising the design of the scheme. Predicting the proportion of flints in the tunnel was a key concern for the design of the tunnel boring machines. The British Geological Survey and the LTC-CASCADE JV Consortium collaborated to create a high resolution geological ground model of the route. A number of techniques were used to characterise the geology including passive seismic surveys, laser scanning, borehole and section logging. This enabled us to create an enhanced 3D geological framework model of the Chalk stratigraphy beneath the Thames including estimates of flint distribution.

Speaker Bio:

Dr Andrew Farrant is a geologist and karst geomorphologist who has worked at BGS for 25 years. His research interests include chalk mapping, including digital mapping technologies and 3D modelling in southern England, as well as Quaternary terrains of the UAE. Andrew applies geological mapping and 3D modelling for geohazard assessment as well as groundwater resource management. His research interests also include landscape evolution using U-Th and U-Pb dating of speleothems, as well as karst geomorphology and hydrogeology.