[On-site Trouble Case] 10 cm settlement of a bridge pier immediately after construction.

Discovered during inspection after the pull-out of the arrow board! Introducing the estimated causes and proposed countermeasure methods.

This is a case study about a new bridge construction project with a length of approximately 40 meters and two spans, where differential settlement of the bridge piers occurred after the construction of the substructure. Upon examining the collected data, it was found that a cohesive soil layer exists at a depth of more than 2 meters, which is shallower than the depth of the sheet piles. During the extraction of the steel sheet piles, there was soil adhesion from these cohesive soils, resulting in voids within the ground due to the thickness of the steel sheet piles and the attached soil. It is estimated that the surrounding ground moved into the voids that formed within the ground, leading to settlement of the foundation ground. 【Countermeasure Proposal】 - Apply a friction-reducing agent (friction cutter agent) to the temporary steel sheet piles in advance to prevent the adhesion between the temporary steel sheet piles and the ground soil, thereby minimizing the ground voids that occur during the extraction of the steel sheet piles. - By filling the voids that have formed with materials such as cement-bentonite, it is possible to bring the displacement close to zero. *For more details, please download the PDF or feel free to contact us.*

Bridge ConstructionPiles, caissons, sheet pilesGround foundation construction method