ABSTRACT

The first groundwater level in the Quaternary sands is approximately 3 m below ground surface. The second groundwater level is perched and circulates in the fissured limestone banks and sand lenses. The energy level of the perched

1 GROUND INVESTIGATIONS

The ground investigations are essential preliminary to the construction of high-rise buildings. The objectives of a ground investigation are to obtain reliable information to generate an economic and appropriate design, to evaluate all conditions associated with the ground and the groundwater as well as to meet the requirement for the tendering, the construction, the time and the cost schedule. The results and the interpretation of the investigations are crucial factors for the stability and serviceability of the structure. Especially when designing highrise buildings the ground and groundwater conditions as well as all relevant geological data must be investigated in detail. The ground conditions have to be worked out by a geotechnical engineer. The investigation can consist of:

− Direct investigations (drillings, trial pits) − Geophysical methods (crosshole seismic) − Field and laboratory tests (geotechnical /

geothermal) − Load tests (plate or pile)

In order to evaluate the ground conditions within the area of the project T185 properly, 11 boreholes with length up to 110 m were interpreted. The ground encountered consists of Quaternary sands down to 5 m below the surface followed by the so called Frankfurt clay which was formed 2 to 10 million years ago as a result of the sedimentation in the Tertiary sea in the Mainz basin ( Fig. 1). This clay includes limestone banks

groundwater level in the Tertiary reaches the level of the Quaternary groundwater level.