A considerable proportion of sewer renewal, replacement and new construction involves deep trenching which not only causes disruption and delays to road traffic, but also gives rise to ground movements both during and after construction. As part of an on-going study to assess the effect of these ground movements on roads and adjacent buried services, observations are being made of the magnitude and distribution of ground movements produced by deep trenching in a range of ground conditions. This report describes a full-scale trenching trial in which a 5.4m deep by 20m long by 1.1m wide trench was constructed in soft alluvial soil. Information is provided on the effect of the component activities of the trenching operations on the ground movements which develop both at and below the ground surface in the short and long term and also on the magnitude of the strut loads and the porewater pressure changes caused by the construction.

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