Open procedure for a study of building materials and building materials at the caissons of the Hohenzollern Bridge in the Rhine in Cologne.

Due to the ever-growing traffic, the administration was commissioned by the Council to plan the expansion of the north and south sides of the Hohenzollern Bridge as well as the new construction of a left Rhine ramp. On the north side, the existing cantilever is to be extended by up to 1.40 m, and an additional 11 m wide foot and cycle path bridge is to be built on the south side. In addition, barrier-free access is to be created in the form of a ramp on the northern left side of the Rhine.

It is intended to build the southern bridge extension where the remaining abutment pockets of the old road bridge and caissons are located in the Rhine. In order to gain planning certainty, the parts of the existing caissons in the Rhine are to be examined for their condition, which have not yet been superbuilt.

The components are completely underwater and partly below the sole of the Rhine. The entire construction site can only be reached from the water side. A diving group is required to carry out the work.

As a basis for further planning to broaden the Hohenzollern Bridge, the overstream caissons from 1912, are to be investigated with regard to their condition under the two existing bridge pillars of the Hohenzollern Bridge. In addition to building material samples, visual inspection and measurement of caissons in 3D is required. In addition, in the course of these investigations, a site exploration with a corresponding report is to be carried out, which is also intended to serve as a planning basis for bridge expansion.

The existing caissons still contain pillar stumps of the old Hohenzollern Bridge from before World War II. The construction site is located at Rhine-km 688.5 at the Hohenzollern Bridge in Cologne (internal stand). The Rhine is a busy federal waterway of the inland waterway category VIc. The components are completely underwater and partly below the sole of the Rhine. The entire construction site can only be reached from the water side. A diving group is required to carry out the work.

First, 2 core holes with a length of up to 9 m per bridge pillar are to be produced through the existing pillar stump down to the sole of the caisson. After the core drilling has been carried out, the non-superbuilt pier stumps and the caisson surface south of the bridge (upper stream side) must be exposed with the help of a swimming excavator and a diving group. Soil excavation must be carried out during construction by a diver with certificate of qualification according to §19ExplorengG, as surface detection is not possible due to the inhomogeneous substrate. The excavation material must be moped or craned out in the Rhine-km 701.00 area (Leverkusen local location) in accordance with the specifications of the WSA Cologne (Cologne location). For subsequent re-filling of the manufactured excavation pits, it is also necessary to dredge 687.00 material (gravel sand) in the area of the “Deutzer Platte” at Rhein-km at Rhein-km (gravel sand) in accordance with the specifications of the WSA Rhine and installed in the excavation pits after completion of the investigation work. The excavation pit filled with gravel sand is to be covered as a colk protection with a 1.50 m thick water block fill. The maximum excavation depth of the excavation pits from the sole of the Rhine is up to about 5 m.

The exposed side surfaces of the pillar stump and the caisson surface are to be cleaned up to the upcoming concrete by means of a high-pressure device and must be visually checked directly afterwards by an engineering diver with a construction inspection certificate according to DIN 1076. The entire surfaces are to be documented using underwater video recording. Damage detected must be documented in tabular form according to type, size and location.

The exposed caisson edges and the pillar stumps are then measured three-dimensionally in position and height using a fan echo sounder image. After checking or measuring, the power boxes or bridge pillars must be filled with the inter-bearing excavation material as found.

In order to investigate the existing building land, 3 core wells and ram core probes up to a depth of 15 m from the sole of the Rhine are planned around the caisson areas concerned. Drilling and ramming probes are to be produced from the ship.

Appropriate combat gear inspection work must be carried out prior to the implementation of ground intervention measures.