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The interaction mechanisms between surface structures and tunnelling-induced ground movements were investigated through centrifuge testing. Although numerous studies have considered this soil-structure interaction problem, previous experiments have neglected important building characteristics and field data inherently contain numerous uncertainties related to the soil, the structure and the tunnelling procedure. Consequently, the interpretation of results and validation of computational models can be problematic. In this study, tunnelling beneath three-dimensional printed structural models with varying building characteristics (i.e. position, length and facade openings) was simulated in a centrifuge. The experimental results demonstrate that tunnelling induces soil displacements at the surface and subsurface that are notably altered due to nearby structures. Specifically, different amounts of vertical and horizontal ground movements, soil dilation and widening of settlement troughs were observed. Building distortions and horizontal building strains were also affected by the relative position of the building to the tunnel, the building length and the area of facade openings. The experimental results provide important data for the evaluation of current design methods and verification of computational models. [ABSTRACT FROM AUTHOR]

A series of centrifuge model tests in clay was carried out to investigate the response of an existing tunnel at different clear distances to new tunnelling. A three-dimensional (3D) staged tunnelling model was adopted to simulate a wide range of tail void volume losses for the new tunnel construction while monitoring detailed 3D soil surface settlements and tunnelling-induced strains in the existing tunnel lining. This paper also presents a detailed case study of a similar scenario in the London Underground redevelopment of Bond Street station; various state-of-the-art instrumentation methods, including fibre optic Brillouin optical time domain reflectometry, instrumented tunnel bolts and photogrammetry, were deployed to monitor the response of the existing Royal Mail tunnel due to the new tunnelling works close beneath. The combination of field and centrifuge modelling data provides important new insights into the deformation mechanisms encountered in such complex tunnelling scenarios. [ABSTRACT FROM AUTHOR]

This paper examines the effect that tunnel size, depth and volume loss have on greenfield soil displacements above tunnels in sandy ground. The results of a series of plane-strain centrifuge tests performed on tunnels in a dry silica sand are examined. The cover-to-diameter ratio, /, of the tunnels ranged from 1·3 to 4·4. Features of greenfield settlement trough shape, both surface and subsurface, are illustrated by examining soil displacement data obtained using an image-based deformation measurement technique. The effects of tunnel size, depth and volume loss are demonstrated, and the suitability of typical fitting curves is discussed. The complex volumetric behaviour of drained soil is illustrated by comparing tunnel volume loss with the volume loss experienced by the soil. A set of equations is developed that provide a method of evaluating the change of settlement trough shape with tunnel size, depth and volume loss. [ABSTRACT FROM AUTHOR]

New developments in both the theory and the practice of tunnelling are covered in the lecture. The important relationship between tunnelling and geotechnics is highlighted, and recent advances in research and practice are described, drawing on model studies, theoretical developments and field measurements from case histories from around the world. Simplified plasticity models are presented that can be used by designers to assess ground movements and tunnel lining loads in complex ground conditions. The important role of pilot tunnels and in situ measurements to validate such models, drawing on a case history from Bolu, Turkey, and on other tunnelling projects, is described. Recent technical advances in earth pressure balance tunnelling are considered, illustrated by measurements from the Channel Tunnel Rail Link project, with emphasis on key factors influencing volume loss, such as face pressure, soil conditioning and effective screw conveyor operation. A recent case history in Bologna is described, in which the innovative use of directional drilling to install curved grout tubes was employed for a compensation grouting project in granular soils. Timedependent ground movements and tunnel lining distortions occurring after tunnelling are discussed, their magnitude depending on the relative permeability of the tunnel lining and soil, the degree of anisotropy of the soil permeability, and the initial pore pressure prior to tunnelling. The effects of tunnelling-induced settlements on pipelines are considered, drawing on centrifuge tests and analytical solutions, and a new design approach is presented, taking into account the reduction of soil stiffness with increasing shear strain as a result of tunnel volume loss. The lecture concludes with a description of a distributed strain sensing technique using fibre optic technology, based on Brillouin optical time domain reflectometry (BOTDR), and its innovative application to field monitoring of a masonry tunnel subjected to new tunnel construction beneath it. [ABSTRACT FROM AUTHOR]

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This paper presents an experimental study of the effects of soil loading on large-diameter, close-fitting, nonbonded, flexible sewer liners as typified by ‘cured-in-place pipes’ (CIPP). CIPP is the process whereby a polymeric pipe lining is cast directly against the wall of a deteriorating sewer pipe. The transfer of soil loading to CIPP liners is strongly influenced by the interaction between the existing host pipe and the surrounding soil. In adjusting to deterioration events of the host pipe and possible void formation in the soil, the existing pipe-soil structure deforms and interacts with the liner inside it. By monitoring deformations of the liner and host structure the magnitude of load transfer can be inferred. The paper describes 1/30th scale physical models tested in dry sand under 30g of centrifugal acceleration. The models included: (a) a host pipe with two simulated modes of deterioration; (b) an instrumented close-fitting, nonbonded, flexible liner; (c) voids in the soil; and (d) moving, heavy traffic loading. The tests showed that, even under extreme loading conditions, the deformations of the liner are relatively small (2-3% of diameter), implying that the presence of a thin, flexible non-bonded and close-fitting liner has an important stiffening effect on the response of the deteriorating host pipe. The important influence of void position in the surrounding soil was also demonstrated. [ABSTRACT FROM AUTHOR]