Construction ground investigation, SBB Ergolz bridge

The Ergolz river forms a striking left-hand bend in the area of the SBB Ergolz bridge in Kaiseraugst, Aargau. The right-hand bridge column of the concrete railway bridge, built in 1976, is located on the outside of the curve (undercut slope) and is therefore situated in the main flow of the river. During floods, high flow velocities can occur in this area. Until now, this has led to a definite risk of erosion and undercutting of the right-hand column and the adjoining bank wall. This danger should be counteracted structurally.

As a basis for the necessary structural improvement measures, GEOTEST carried out a construction ground investigation in the area at risk on behalf of the SBB.
 

The investigation concept consisted of a combination of three core drillings and eleven pile-driving probes, both on the bank and in the riverbed. The probing in the riverbed was executed using a temporary platform. In addition to a geological-geotechnical survey of the drill cores, selected drill-core sections were examined for their uniaxial compression strength in a geomechanical laboratory. GEOTEST used these data and analyses to formulate geotechnical recommendations for the strengthening of the column and, optionally, the bank wall.