ABSTRACT
In an urban environment the need for construction of tunnels for transportation or utility systems is always present. For practical reasons such as accessibility, serviceability and economy these tunnels are constructed at shallow depths. Since the ground near the surface consists very often from soils or weak rocks, the shallow tunnels are usually constructed using either tunnel boring machines or tunnelling methods based on NATM (New Austrian Tunnelling Method) principles often combined with certain type of soil or rock improvement and reinforcement. These techniques are used to modify stresses within the layers of soil adjacent to underground works and/or to modify geotechnical parameters of the soil. So-called prelining methods form one important group of available improvement processes.
