Masonry renovation of the "Michael" bastion on the Petersberg

The City of Erfurt, Office for Property and Building Management, took measures to renovate the masonry of the retaining wall of the "Michael" bastion on Petersberg. The wall showed localised deformation (bulging) and two break-outs, meaning that further collapses of the wall were possible. The wall was no longer stable and needed to be renovated. 

The two pieces of the wall that had broken out first had to be cleared in order to then permanently secure the pressing slope with the help of boreholes and grouted piles. Finally, both excavations were faced with natural stone masonry and filled by injection. The section of wall with the bulge was also secured with grouted piles to permanently prevent further excavation. Concrete pockets were cut out so that the piles were no longer visible at the end. The same procedure, only with a larger drilling diameter, was used for the support pillars. Here too, the cavities behind the wall were filled by injection. In addition, the neighbouring masonry and the masonry crown in this area had become unstable due to partially broken joints. These allowed water to penetrate and the stones to weather or loosen.