Abstract
Large groundwater flow into the tunnel during construction of a tunnel can cause crucial problems. It is therefore important to investigate the location, flowrate, and hydraulic pressure of the flow paths ahead of the tunnel face in advance to tunnel excavations. One of the effective ways to characterize the flow paths is measurement of flowrate and pressure in the advanced horizontal boreholes using a packer system. However, with the conventional method, it is often difficult to carry out the installation of packer systems due to the risks of borehole collapse and delay in the construction schedule caused by pulling out the drilling string before packer installation. Therefore, the authors have developed a new measurement system that can be installed packer without pulling out the drilling tools. This paper describes the concept of this system, and a result of its successful application to a tunnel construction site.
