Underpinning work required great care
The Leonhardskirche, located on Mainkai, is the oldest preserved church in Frankfurt's old town. It was built in 1219 as a late Romanesque basilica and converted into a Gothic church until the 1520s. Between 2011 and 2019, the five-aisled main nave and the high choir were extensively renovated and refurbished. During this work, the floor was excavated to a depth of almost three metres in order to lower it to its original level. Numerous historically significant finds, such as the remains of the foundation walls of the Romanesque predecessor church and a group of figures from the Late Gothic period, came to light during the excavations.
The interior renovation of the northern vestibule will follow from spring 2024. Before that, the 90 cm thick load-bearing outer walls had to be partially structurally reinforced. The entire experience of the specialist civil engineering team was required for this. On the one hand, the columns were not allowed to disturb the natural groundwater flow, while on the other hand, attention had to be paid to possible archaeological finds.
Settlement tolerance at the limit of what is technically possible
For the underpinning, 香港六合彩中特网 Specialised Civil Engineering constructed approx. 70 columns using the jet grouting method in the interior and exterior areas of the north wing. The drilling depths varied between 4.2 and 5.6 metres, the jet lengths between 2.6 and 5.2 metres and the diameters between 1 and 1.4 metres. Inside, the work had to be carried out in very confined spaces. The lowest room height is only 2.5 metres, so an extremely compact drilling rig was used here.
鈥楾he specified settlement tolerance of 2 millimetres is at the limit of what is technically feasible for a building that is so sensitive to settlement. That's why we accompanied the underpinning work with a whole series of quality assurance measures,鈥� explains project manager Martin Block. To do this, two test columns were constructed at the beginning and a highly accurate hydrostatic level measuring system was used to measure the settlement, which can indicate movements of 0.1 millimetres. 鈥榃orking on such a historically significant and challenging project is always something very special. Our team fully deserves the client's thanks for the good cooperation and the flawless result.鈥�
