ABSTRACT

On the investigated tunnel line there are two groundwater horizons above the till layer. The upper water horizon above the clay complex lies in marine sands and the fill deposit and gets its recharge from precipitation. The water table lies 0,3…1,0 meters beneath the ground level and the water there is fairly polluted, containing nitrates and phosphates. Under the clay complex there lies a layer of artesian groundwater that is connected with the upper unconfined groundwater horizon via the occasional “openings” in weak clay. From the onset of the excavation works, the pressure level

1 INTRODUCTION

The tunnel is 2,2 meters in diameter is and it is supported with reinforced concrete elements; the length of the tunnel is 3 kilometres.