This report deals with the loading of the geomembrane during the construction phase of the inner shell of a tunnel. In a systematic parameter analysis at the institute for underground construction at FH Munster the geomembrane and the geotextile were tested under different realistic conditions. Laboratory testing showed a dependence on the seal support surface of the shotcrete and on the characteristics of the geotextile. The deformations of the membranes due to fresh concrete pressure are significantly smaller than the permitted values in the technical regulations. The main results of the investigations are described below.