ICE 815C salvages submersed casing

In 2018 Typhoon Mangkhut damaged sheet piles and casing piles that had been part of the land reclamation at Hong Kong’s Tseung Wan O’s Cross Bay Link project, so after the reclamation work was completed these piles needed to be cut off or extracted. The foundation for the cross-bay bridge has now started, foundations are built with a drilling rig machine. One of the drilling teams ran into trouble, the drilling rig hit a hard object. The first explanation was that the drill had encountered a hard boulder, but a diver investigation found a cut-off casing that was buried in the seabed to be the obstruction. The 22m long casing had to be removed the same way it had been installed, by hydraulic Vibratory Hammer, so that the drilling could be resumed.

The drilling work platform was right above the spot where the buried casing was found. The first step was to cut a larger opening in the working platform so that a Vibratory Hammer could go down through it to reach the pile. As space on the platform was limited, the client chose the smallest Vibratory Hammer available, the ICE 416L. The pile top was located 9 meters below water, level with the seabed. A diver went down to clear about 30cm of soil around and in the pile so that the clamps could fit on the pile rim. Divers than guided the hammer down to position the clamps onto the casing. Above the waterline, the “clamp closed” indicators on the power pack were helpful for the operator to determine that the clamps were closed and in correct position and were the sign to start up the hammer. Unfortunately, the 416L’s eccentric force turned out to be insufficient to extract the casing. In the end an 815C, providing 125t of eccentric force, was needed to overcome the soil friction to extract the 800mm casing. Once using the correct sized hammer, the pile was extracted within a few minutes.

As there was limited space on the platform, the 600 Power Pack was placed in a barge alongside. The wireless remote enabled the operator to stand away from the power pack, on top of the platform, with an excellent sight of the operation.

To ensure no soil would contaminate the water during extraction the contractor took the precaution to position a net around the platform to keep the suspended soil  within its bounds.

The project is located in the very east side of Hong Kong, a new tunnel and a bridge will relieve traffic congestion in Tseung Kwan O and allow for easier access to/from Lam Tin. There are two projects happening in one jobsite; a tunnel that connects Tseung Kwan O to Lam Tin and a bridge that provides a link across the bay. The projects are right next to each other so people that are coming to Lam Tin can go directly to the other side of the bay through the bridge.

This article shows how ICE Vibratory Hammer can be adapted to various working conditions. ICE Vibratory Hammers can operate in marine applications, dipping the gearbox under the water line is possible. For full submersion of the hammer some precautions need to be taken, and for depths over 10 meters the gear box must be pressurized. Please consult the operation manual and contact us before your job so that we can guide you to the best solution for your problem!