The subject of this thesis is the verification of a three-dimensional numerical modelling approach for the prediction of settlement damage to masonry buildings due to tunnelling in soft ground. The modelling approach was developed by previous researchers at Oxford, and was applied to three sites, representative of a range of practical configurations. The first involved the excavation of a shaft close to the corner of an eighteenth century church in London. The second involved tunnelling with very low cover beneath the foundations of a terrace of cottages at Ramsgate, Kent. The third was the relatively well-known case of tunnelling beneath the Mansion House, London, for construction of the extension to the Docklands Light Railway in the late 1980’s.

Growing needs for modern transportation and utility networks have increased the demand for a more extensive and elaborate use of underground space. As a result, more underground projects have to be completed in a variety of ground conditions, including weak water bearing soils and soft rocks. Significant technological advances have rendered these projects possible, but have also given rise to new challenges as many of these projects have to be completed in difficult conditions, with very strict environmental constraints, particularly in urban areas where the potential impact of tunneling on existing structures is a major concern. This report addresses the main aspects of tunneling and underground works performed in soils and soft rocks. A summary is presented of the main features related to construction techniques, ground investigations, design methods, and instrumentation and monitoring practices, as well as of some of the more recent advances in these fields.
Significant progress has been made in the area of soft ground tunneling over the past thirty years, partly because of advances in computer technologies. The scope of increasing difficult project conditions to be addressed requires that the best use be made of these technologies, as well as of lessons gained from past experience and current observational records.

This lecture deals with tunnelling under squeezing rock conditions. Following an outline of the main factors influencing squeezing, the definition of this type of behaviour, as proposed by ISRM (International Society for Rock Mechanics) in 1995, is given. An overview of the methods used for identification and quantification of squeezing is presented, along with the empirical and semi-empirical approaches presently available in order to anticipate the potential of squeezing tunnel problems. A brief historical retrospective is reported on the excavation and support methods used in Italy in order to cope with squeezing conditions at the end of 1800, when the first railway tunnels were excavated.
Based on the experiences made and lessons learned in recent years through important tunnelling works in Europe, an attempt is made to trace the state of the art in modern construction methods, when dealing with squeezing conditions by either conventional or mechanised excavation. The closed-form solutions available for the analysis of the rock mass response during tunnel excavation are described in terms of the ground characteristic line and with reference to some elasto-plastic or elasto-visco-plastic stress-strain models for the rock mass. Also described are the equations for the support characteristic lines.
Then, the use of numerical methods for the simulation of different models of behaviour and for design analysis of complex excavation and support systems is considered, also including three-dimensional conditions near the advancing tunnel face.
Finally, a brief discussion on monitoring methods is given, in conjunction with a short description of a case study.