Introducing The...Instant Quarry
The drive towards implementing the waste hierarchy into all aspects of government policy in the UK has led to a raft of new phrases being coined. Linear quarry and urban quarry are just two. You can now add to that list the “instant quarry”. Offering in-situ soil stabilisation without the need for excavating material, new company Eco-Basements and Foundations is keen to show the country how firms can cut back on aggregate use by using the very ground they build on as a source of stabilisation material.
The UK is getting wetter. A new study from Durham University states that the country is now moving through a “flood-rich” period in its history, compared with the “flood-poor” period of the 1960s. Its report concludeds that we need more investment in flood defences and protection.
Joining the call from academics in early May was a new Environment, Food and Rural Affairs committee report calling for greater investment in flood protection, and a British Property Federation call for more investment in flood defence engineering.
This, of course, coincides with some ambitious government plans for housing growth in the UK over the coming years. One growth area is the Thames Gateway, a part of the UK a new May-released Hermes and Southampton University study labels as a serious flood risk.
But the heady mixture of limited space, housing targets and demographics leaves the country little option but to build on flood plains. The challenge is to ensure construction mitigates the effects of flooding as much as possible. And this is something a new Stratford-based firm believes it can help with.
Seeking to ride the wave of flood alleviation, the introduction of site waste management plans (SWMPs) and increasing pressure to reduce C&D waste and improve recycling rates is Robert McGall, MD of Eco Basements and Foundations (EBF).
Together with AGD Equipment MD Robert Law, McGall is utilising machinery from German firm RTG and Finland’s Allu to introduce the concept of the instant quarry to the UK by offering both wet and dry in-situ ground stabilisation.
Former Dawson Wam director McGall explains: “Ours is a soil mixing system that utilises the aggregate and soils that are in the ground. It mixes them with cement slurry – or other binders such as pulverised fuel ash, lime or other powders – and makes concrete in-situ either in columns or over large areas.
“Rather than taking ground away, as you traditionally do with a pile for example, you use the material down there to make concrete. And it doesn’t matter if the ground is wet or dry as we have a process to suit both. We simply use the moisture in the ground if it is wet,” he told MQR.
McGall has been a civil engineer in construction and deep excavation work for 25years. Last October he got together with Law – director and co-shareholder of EBF – after seeing the RTG rig and Allu device in action.
AGD provides EBF with the equipment on a rental basis. Law: “Renting is a good way to start the business. When you start out you do not use the plant all the time and because we are a rental firm we can rent the plant out when Eco isn’t using it.”
The two pieces of kit offer two approaches. The RTG rig offers deep stabilised columns. This is achieved by means of an auger through which a cement/binder slurry is pumped. The Allu rig, however, works more as a whisk than a drill.
The Allu power mixer is attached to an excavator allowing mass stabilisation at 4,5 and 6m over a given area. The ground is split into 4m x 4m panels and is worked a panel at a time. A secondary machine follows the excavator feeding the binder through a hopper.
EBF has invested in two hoppers to improve production, says Law: “You can be filling the one while using the other. It is all crawler mounted, with a compressor built in. And there is a filter so you don’t lose material when you transfer it from the tanker.
“The dry material is blown through the machine by the compressor. Water can be added if the material is too dry. It is all about getting the mix right.”
However, while it is an interesting solution to stabilisation – one proven by years of experience on the continent – it is not suited to all grounds. McGall: “It has to be the right soil or granular material and not clay or chalk. Any thing with sand and gravel in is OK or a mixture of some clay and alluvium and soft silts.”
In case potential clients are unsure as to whether the EBF system will suit their projects, the firm has enlisted the help of the Danish consultants Rambor, who helped Allu design its stabilisation plant, to ensure project viability. They can also suggest the right mix to use.
McGall explains: “We send them samples and they say how much cement can be used or how much of any other binder is used such as blast furnace slag or lime.”
Both men see the flood protection market as key to expansion but point out that their delivery system for hydraulically bound material can also lock in contaminants as well as being a good solution to the problem of creating haul roads.
“In fact,” says McGall, “we feel the possibilities for this kind of system in the UK are very wide indeed.”
EBP: 01789 295020 or 07979 533925
Sample project: Valencia Port
An example of one of the processes being used by Eco Pavements and Foundations is the work by the Valencia Port Authority to incorporate a new area of 140,000m2 for the storage of containers.
A zone with a 65,000m2 surface area had been back-filled with around 1,000,000m3 of dredged mud of very low consistency. This created a problematic artificial lagoon.
The designers chose a soil-cement crust solution to the problem of load-bearing (see picture above) using the Allu mass-stabilisation method. The crust not only allowed equipment to move across the surface of mud but also allowed the creation of the port pavement.
A 4m thick crust was created by adding the dry cement mixture to the mud. The 90-110kg/m3 type II/BV 42.5R cement addition allowed project managers to step on the crust after 3-7days. The crust had a volume of 250,000m3.
The mixing was performed in cells with dimensions of about 4m deep, 4.5m in length and 3.2-3.8m wide. The mixer was placed in front of the cells – resting on an already stabilized zone – and started adding cement and mixing it with the mud in an operation that lasted from 60 to 90minutes.
