Tandem 170NF shows it’s worth, more powerful and lower impact than expected

Earlier this year I made a site visit to Xiapu in Ningde County, a city along the coast of Fujian Province. Zhejiang Communication Construction Group is building a highway bridge across a bay that is full of aquaculture. The initial design called for the 94m long, 4.4m diameter casings, to be hammered into the soil with an impact hammer, but the sound caused massive fish death. Plan B: vibrating the piles. A local vibratory hammer brand was brought in, but this hammer also freaked out the fish within 2km range, probably because the frequency didn’t meet the spec. Third time right, ICE 170NF tandem was what got the piles down and the fishermen mollified. It was interesting to see the pile upending method, the tandem vibro mounted on a piling rig, and to catch up with old friends!

The 170NF is attached to this leader on a piling vessel. The pile weight exceeded the line pull of the 170NF tandem, so the hammer rested on the top of the pile. When I was there was a pile-run, the pile shot down about 6 meters, and the hammer which was resting on top of the pile went down with it. The sudden jolt created when the pile reaches a firmer soil layer probably made the elastomers work very hard and it resulted in the need to replace some broken elastomers after the conclusion of the project.

Location

The coast of Fujian Province.

Equipment

ICE 170NF Twin Vibratory Hammer & 2 ICE 1400 Power Packs

Works

Driving 94m long, 4.4m diameter casings

Executor

Zhejiang Communication Construction Group

Why bigger vibratory hammers aren’t always better is easily understood:

A vibratory hammer is made up of two parts: a dynamic vibrating part (the gearcase, clamps, 50% of the weight of the elastomers) and the static weight (the yoke and the other half of the elastomer weight). The heavier the dynamic part the more eccentric weight is used up by moving the dynamic weight and less remains to create amplitude to liquefy the soil. This tends to create a vicious cycle of ever increasing weight to create more amplitude. That is why ICE is so focused on right-sizing the hammer recommended for each job as it will give the best piling result.