Ground penetrating radar for advance ground checking and crack detection during tunneling

Application of ground penetrating radar in clayey and limestone grounds during tunneling is described in this report. Two types of measurements were carried out in tunnel: in front of the tunneling shield, where large stones, water-filled lenses and other obstacles could lead to serious damage of tunneling shield during its work. In the second case the sounding was carried out through the ready tunnel wal! to detect cracks inside the wall and ground inhomogeneities beyond the wall. The obtained results show, that ground penetrating radar is a useful tooi for advance ground checking in front of the tunneling shield and sounding of radio-transparent tunnel walls and of the ground beyond the wall. Constrictions on measurements in front of the tunneling shield are stated.