Ground movements and deflections of an anchored sheet pile wall in granular soil

Abstract

Abstract For road construction and improvement schemes in urban areas, the restricted space available has led to an increase in the use of earth retaining structures. The effect of ground movements caused by the retaining wall construction, on adjacent roads, buildings and buried services, is frequently a prime concern in design. The complexity of the construction sequence and the effect of soil-structure interaction generally precludes accurate predictions of ground movement, although an assessment of their upper and lower bounds can be obtained from previous field measurements. This paper describes the pattern of ground movements and deflections of an anchored sheet pile wall forming part of the temporary works for the A1(M) Improvement Scheme at Hatfield, Hertfordshire. This scheme involved the construction of an 1150 m long cut and cover tunnel together with a 350 m length of retained cutting for the tunnel approach. The ground conditions over the tunnel depth consisted of glaciofluvial sands and gravels (Westmill Upper Gravel) overlying a lodgement till deposit (Ware Till). Approximately 2 km of anchored sheet pile walls were used on the scheme to retain the ground during construction of the permanent works. A section of the temporary sheet pile wall was extensively instrumented and observations made both during its construction and over the ten month period when the wall was in service. Measurements of ground movement and wall deflection formed part of a wider research study at the site designed to investigate the behaviour of the sheet pile wall and of the prestressed ground anchors.