We haven’t reported on Shanghai ‘s Elevated highway construction project for a while, partly because where does one start? Steel foundations for elevated highways are all the rage in the city with numerous projects all around the city ongoing. Resonance Free vibratory hammers are used to drive 60m long steel foundations piles into the soil. 9-12 piles make up the foundation platform. The installation method is safe, fast and clean. The road elements are prepared offsite, trucked in and lifted in place with 300t crawler cranes.

Safe close to metro and buried utilities

Fast one platform consisting of 10 60m long piles can be installed in a day

Clean     no soil excavation, no bentonite, no concrete

We visited the Jiyang Road Elevated Highway project recently to join a progress meeting and shared some advice about conditions that effect pile driving operation. I’d like to share some key points from the progress meeting that may be helpful for all our users:

1.  We look at working pressure to assess whether the hammer is working correctly, the max working pressure is 350 bar. If the pile doesn’t go down but working pressure is low the guideline is to add extra weight to the hammer to help the pile overcome soil friction. While there is no direct correlation with bearing capacity with working pressure, high working pressure is in an indicator of faster bearing capacity loads.

2. We also recommend monitoring of the verticality of the pile, a minor deviation may result in the 60m long pile hitting adjacent piles deep underground. We will post an article about a verticality sensor next week.

3. Operator related; we find that even experienced operators need a little extra guidance, do not over emphasize installation speed, adjust the variable moment of the hammer in steps and aim to work at max frequency. Control driving speed by crane operator.

4. Why do some piles go all the way and do some meet refusal? Shanghai’s 7-2-layer soil profile doesn’t have the same sand compactness everywhere, a rule of thumb is that when N-Values go over 50, liquefaction of the soil is too poor to drive the pile down. Some ways to get the pile down is to use an impact hammer, or by adding high pressured water to the bottom of the pile, pre-boring, or even emptying the inside of the pile, taking careful consideration of the impact this may have n the bearing capacity of the pile. A stray boulder or other debris that halt pile driving are also possible reasons for refusal.

5. In case you missed it, you may be interested in reading a previously published article about how frequency-controlled driving can shorten the period needed for reaching the intended bearing capacity of your steel foundations.

After the meeting we did a site visit and I took some photos of the project that I’m sharing with you all today. At Jiyang road the piles are 60m long and installed by the Greenland Group team. They are one of the first users of ICE RF equipment in Shanghai and reach very high daily production rates. One of their insights is that using the PLD device increases efficiency significantly. After welding two lifting hooks on the pile at exact distance off the pile tip, the PLD’s shackles are attached and the hammer lifts the pile into position, eliminating the need for an auxiliary crane or hook.

PLD is picking up the pile

The space reserved for the construction work is in the middle of the highway, with only limited impact to regular traffic flow. The super-fast pre-fab highway construction method also limits the duration of the work and reduces sound and dust impact on neighboring communities.

Piles are prepared ahead of time, allowing both high efficiency as well as enough time for the welds too cool down.

Some further optimization would be to use the auxiliary hook for lifting the hydraulic hoses. This makes handling much easier and avoids a lot of wear and tear on the hoses. Where possible we also recommend positioning the power pack on the counterweight of the crawler crane or piling rig. In this specific situation the room to maneuver is not so big, adding the power pack would increase the turning radius of the crane.

Please don’t hesitate to get in touch with ICE if you have questions about your foundation work. We have a wealth of application knowledge gained together with our users and some cutting-edge tools that help our users reach higher efficiencies, we welcome all inquiries large and small. Give us a call at 021+-34688990 or leave your details in the comment section below.