Testing of soil samples from Bell Common Tunnel

The work described in this report is part of a programme of research into the design and behaviour of embedded retaining walls which is being carried out by the Transport and Road Research Laboratory (TRRL) on behalf of the Department of Transport. During the design of the cut and cover tunnel at Bell Common, Epping, Essex for the M25 London orbital motorway, several geotechnical problems emerged with respect to the design of the in-situ retaining walls. This led to theoretical investigations of the stability, ground displacements and working stresses in the structure, (see IRRD 281207 and 271617). A small section of the Bell Common walls has been jointly monitored by the TRRL and the Building Research Establishment. This report describes a series of laboratory tests on samples of Claygate Beds and London Clay from Bell Common. The objective of the work was to use the most up to date laboratory techniques to measure the appropriate stiffness and strength parameters. These have since been used for further finite element analyses to obtain revised predictions of the Bell Common Tunnel and the results compared with the field observations (see IRRD 822044).