CONDITIONS IMPACTING UNDERGROUND PROJECTS

To develop a tunnel PROJECT is more than to just produce drawings to visualize a structure which later should become a tunnel. The tunnel developer has to be the manager of the tunnel project including construction, as development is a management tool in design and construction. As tunnel failure analysis show, financial conditions are major factors impacting tunnel development and management by design summarizes the state of the art of contracting in tunnelling, including both conventional and mechanized tunnelling. A detailed brief description will be given in regard to development stages, contractual implications, and project organization. Fundamental requirements for the development of an underground structure are -evaluation and classification of ground conditions with respect to particular project requirements -design with subdivisions in stages, following the project and construction development, which provides the framework for a range of potential applications -construction methods suitable for standard plant, equipment and material backchecking of predictions by geotechnical monitoring and adjustment to the conditions encountered -flexible contractual models for fair compensation, Demand for proper developed Underground Works has been continuously growing since decades. Conventional Tunnelling Method is well suited for tunnelling in difficult, complex and changing geological and geotechnical conditions. The main purpose is to minimise construction cost by selecting optimum driving cross section, driving methods and lining during the design and construction phases. During tunnel excavation simultaneous and joint decision by the contract partners must be realized within predetermined limits to manage flexible response to changing ground and ground behaviour conditions.Tunnelling needs trained, qualified and experienced owners, designers and contractors, it needs qualified and experienced engineers on site, and qualified and experienced workforce. It needs a suitable design as well as a suitable contract model. This goes hand in hand with a contract system which had to be developed for being able to cope with changes in ground behaviour together with the character and scope of the works in a fair and objective way. In the past most tunnels have been excavated using Conventional Tunnelling Methods.The risk of cost overrun and schedule delays caused by uncertainties of the ground must be identified in the very early beginning of the project development. The risk register needs to be developed and continuously further developed during the project development.