Crucial to the success of Contract 102 of the Jubilee Line Extension Project (JLEP) was the detailed analysis of the impact of the construction process on the surrounding ground, structures and tunnels under construction. The construction works were to pass under or alongside some of London's most historic and prestigious buildings, consequently stringent limits were imposed upon ground and structure movements. To control these movements and remain within the limits set, a comprehensive monitoring system was required, comprising a wide variety of instruments linked to a geotechnical database. An extensive and integrated instrumentation system was designed to produce quality data and as no monitoring system existed that covered the unique requirements of the contract and of the Balfour Beatty Amec Joint Venture (BBA), the option was taken by BBA to design and develop a system in house.
The result was Geosys, a windows based monitoring system that could handle data from the various instruments on site, fulfilling a major role in the successful observational approach that was taken to control ground movement from both the tunnelling and the grouting. Geosys enabled electronic data to be reviewed in “real time” and the surveyed precise levelling results could be reviewed within half an hour of survey, if required; feedback loops into the design resulted in a major impact upon the construction decision making processes. The data handling and processing developed within Geosys are described. The subsequent geotechnical benefits to the contract, through the application of high quality processed monitoring data to the control of the ground movements and the construction works, are discussed.