Microtunneling design and development for river underpass.

Throughout the world, pipe jacking and microtunneling are becoming increasingly important for the installation of sewer pipes and service lines. Microtunneling is a technique for installing underground pipes without trenching with the advantage of causing minimum disturbance along the construction route. A real case of microtunneling construction is described by focusing on each different step of the process, including the geological and geotechnical assessments based on the performed tests and on the available data. Concerning the drive pit construction the analysis of slope stability is done, a numerical model with finite elements is used to examine the static conditions when vertical and horizontal loads are present, the pit global stability is verified and the structural verification for the reinforcement is performed as well. At last the stress state generated in the jacking pipes is analyzed with different methods, by taking into account also the filling material used for the overcut; for this last element, the elastic modulus is derived from laboratory test as not known a priori.