Geotechnical subcontractor Geocisa has brought Spanish technology to Crossrail.
When Geocisa arrived in the UK just over two years ago, it brought with it an innovation developed at its Madrid head office.
It’s essentially a grout plant in a box, which, aside from its compactness, can do some pretty sophisticated ground improvement and stabilisation work.
“We’ve been using it at two sites: a compensation grouting job at [Crossrail’s] Farringdon [site] where they are doing tunnel widening work, and my job here at the Royal Victoria Dock Portal [Crossrail site],” says Geocisa site agent Jesús Miguel Gil.
“Here we are improving the river terrace layer to avoid settlement for when the tunnel boring machine comes through.”
The plant is packed into a 6 m container, meaning it can be easily transported to site. Once connected to a power supply and silos, it can be ready to work in about two hours.
Mr Gil says that where a typical grout plant employs two pumps with two lines, the Geocisa version, with its incorporated mixer and agitator, can supply four lines.
“However, the main innovation is the system control and software we have developed,” says Mr Gil.
This can mix water with cement, bentonite or silicate gel with a hardener, depending on what the job requires.
It can also control the mix by weight and adjust the proportions of the mix.
“With a USB memory stick, we can set up the boreholes with mixes, pressures, volumes and flows for each part of the job,” he says.
“This avoids operator errors. You may be doing 400 pours in a 12-hour period, for example, and there is room for human error.”
The system can grout 4 to 5 cu m per line per day, meaning 16 to 20 cu m can be pumped with a degree of certainty as to the resulting ground improvement.
However, this isn’t quite as straightforward as it sounds because the system can self-regulate within certain parameters, such as pressure, volume or minimum flow, to ensure the most efficient pumping regime.
But it can also be set by hand, in the event that there isn’t a pre-configured memory stick.
Mr Gill also points out that the software had to be modified to simulate a continuous flow, to cater for what is a rhythmic pumping action.
Finally, he notes that another advantage of the system is that it also records details of the operator and the site so that when grouting operations have completed, a complete record of the job can be downloaded for the client’s records.
In something as out of sight as completed ground improvement, this can only be a good thing.