The aim of expanding the B15 federal highway is to relieve the city of Rosenheim from truck traffic. In the course of this extension of the B15 with the Rosenheim west bypass, a new railway overpass is being constructed at Wernhardsberg over the Munich-Rosenheim railway line.
The joint venture Spezialtiefbau BW 8.2 Rosenheim, comprising BAUER Spezialtiefbau GmbH (technical management) and Menard GmbH (commercial management), was tasked with the required specialist foundation engineering works. For the bridge foundation, 74 fully cased large-diameter bored piles are being constructed with a diameter of 1,200 mm up to a depth of 40 m. Due to the unfavorable soil conditions, the load of the structure will be transferred into the subsoil with the help of a mixed foundation consisting of piles, vertical drains, and displacement columns.
Not only is all work being carried out during ongoing railway operation, but the construction soil also poses a particular challenge: It consists of Rosenheim marine clay, a fine-grained, soft, water-logged soil with low load-bearing capacity.
“This difficult and sensitive soil places very high demands on the pile installation as well as the accompanying documentation. This is because Rosenheim marine clay is highly unstable due to its properties.”
explains Project Manager Klaus Stauber.
The marine clay was created approximately 10,000 years ago, after the last Ice Age. When the Inn glacier melted, a lake was formed, generating these fine-grained deposits. The vertical drains and displacement columns provide an additional improvement of the marine clay’s load-bearing capacity.
The work is being carried out with a Bauer BG 46 and a BG 39. The project commenced in summer 2021 and is expected to continue until summer 2022.