This paper compiles new and existing information relating to features frequently referred to as drift-filled hollows located within London. The key aim of this paper is to update the article written by Berry (1979), producing a resource for both engineering projects and academic research. Fifty-four additional drift-filled hollows have been identified and their physical characteristics are tabulated where available information allows. A case study of the Nine Elms area is presented. The drift-filled hollows have been identified through examination and critical quality assessment of historical borehole records, site investigation records, construction records and published articles. This enlarged dataset illustrates the high level of variability between features and as a result it is proposed that these features did not form due to a single process, but to differing processes.
Water and fine sand ingressed into a section of running tunnels on the Jubilee line of the UK's London Underground railway in 2010. Concern arose that voids around the tunnel would lead to tunnel instability due to a reduction of lateral confining pressure from the soil. Ground investigation works identified that the running tunnel passed through a very large buried sand channel in the Lambeth Group. Initial attempts to arrest the ingress using an expanding grout were unsuccessful, and manual monitoring showed a slow but continuing deformation of the tunnel. A detailed tunnel investigation revealed that intermittent voiding was present over a wide area. A more comprehensive tunnel investigation and grouting solution was procured and carried out successfully by a group of specialists working together with London Underground. An important aspect of the design was the use of an observational approach, a key component of which was an innovative wireless monitoring system with trigger levels linked to the grouting injection system.
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