Geobear’s solutions resolved erosion issues that disrupted the port’s operations
Hernesaari Port receives thousands of cruise passengers from around the world each year, and passenger numbers are expected to grow further in the coming years. However, the corner of the cruise pier in the harbour area had begun to sink repeatedly into the pits. This issue if not addressed would affect the safety of those using the pier.
Based on the investigations, it was discovered that the root cause of the problem was seawater, which washed away the fine filling of the back wall of the pier retaining wall as it went, thus creating voids behind the retaining wall. Due to the voids, the bearing capacity of the soil deteriorated, causing the asphalt pavements at the pier to crumble and sink.
Attempts had been made to solve the problem by bringing new soil to replace the leached soil and adding new asphalt to the damaged area. However, the root cause was not addressed, which is why the corner of the pier sank and crumbled repeatedly. In 2017, a new cruise pier was built in the area, in connection with which the Port of Helsinki wanted to find a more permanent solution to the problem.
Alternative repair solutions
Because the damaged area was relatively small, no viable alternatives were found in traditional repair methods. For example, the replacement and re-compaction of the fill would have required extensive demolition and excavation work, larger construction sites and thus also higher costs. The project would also have progressed much more slowly.
The main advantage of the solution offered by Geobear was its speed. The repairs could be carried out in a few days without disrupting the day-to-day operations of the port, while alternative repairs would have closed the area to be repaired for several weeks. In addition, remedial measures could be targeted at a small and well-defined area, which is often not possible with traditional methods.
These factors were also directly reflected in the direct and indirect costs of the repair: Geobear’s solution was estimated to bring customer cost savings of up to 50%.
Geobear engineers solved the problem by injecting a geopolymer into the backfill behind the berth retaining wall, which, as it expanded and hardened, bound and compacted the loose soil. In this way, propeller currents and other water movements no longer detach the fill material as easily. This slows down the erosion of the quay structure and effectively prevents the formation of new depressions.
Injection points were drilled at a total of five different locations and were always extended to a depth of seven meters. During drilling, voids of up to half a meter in diameter were found in the soil and filled.
The repairs were over in two days, and construction work on the new cruise pier was allowed to continue at that location on schedule.