Flat Earth theory

Excavation works are not always needed in case of ground subsidence. There are solutions, such as injectable geo-polymers from Uretek, that aim to add stability without requiring the arrival of the diggers.

What it is

Geo-polymer injection is a non-disruptive, efficient alternative to conventional underpinning and piling which Uretek has advanced due to over 30 years of research, development, testing and installation. The implementation of the Uretek geo-polymer injection system can be be categorised as proactive (improving the strength of soils to facilitate an increase in loading or combating long term settlement) or reactive (remediation of subsidence).

The application of geo-polymer injection can be categorised into two phases: 1. Surface consolidation; 2. At depth consolidation.

With regards to surface consolidation, geo-polymer is injected into the shallow area beneath a foundation, with the intent of fully re-establishing contact between the underside of the foundation and the underlying soils by filling any voiding within the treated soil.

At depth consolidation relates to soils being treated at greater depth and thus most concerned with the forces provoked by loading. The objective of at depth treatment is to densify the ground via:

• Elimination of voids by filling and compacting/consolidating 

• Expulsion of air and water

• Agglomeration of the soil (in granular cases)

Verification

Whether geo-polymer injections are used to combat future settlement, or to increase soil strength, a standard on site check is used by Uretek technicians; structural movement. Throughout the geo-polymer injection process, relevant parts of the overlying structure are monitored using rotary lasers and mounted sensors, with sensors placed in the vicinity of the active injection point. Each injection will be prolonged until a reaction is registered (< 0.5mm). This indicates when a degree of compaction/consolidation has been achieved. This also shows that the treated soil has been reinforced sufficiently enough to carry the load of the structure, as an upward force will be acting upon the underside of the above foundation, causing the upward movement.

In order to quantify the increase in soil strength achieved by geo-polymer injections, Dynamic Cone Penetrometer (DCP) testing is typically used. This testing allows an insight to be gained into treated ground conditions and also to clarify the bearing capacity of the tested soil at 100mm increments. By comparing the results of the testing carried out prior to treatment with the results of the DCP testing carried out after treatment, the improvement in the strength of the soils can be shown.

Conclusion

Uretek is constantly striving to make developments both in terms of geo-polymers (developing existing materials and creating new geo-polymers) and of best practice for installation/verification. As a result of this Uretek is able to adapt to meet the requirements of both our clients and the sites we work on. This ensures that Uretek’s non disruptive ethos is upheld, as well as enabling Uretek to continue to demonstrate the main benefits of geo-polymer injection. These are:

• Speed

• Lack of disruption

• Efficiency

• Minimal plant

• Minimal environmental impact 

• No need to excavate.

For a structural engineer, a key benefit of utilising geo-polymer injection over traditional methods is the efficiency of the system. The wider economic impact of invasive methods caused by disruption and lengthy timeframes is becoming more accountable. By having the option to reinforce soils and increase load bearing capacity within days using geo-polymer injection, stakeholders can focus on the long term goals of the overall project.

With the body of research substantiating the use of geo-polymer injection and over 200,000 projects delivered by Uretek alone in the last 30 years, the use of geo-polymers is now a mainstream consideration for consultant engineers around the world.

You can download a Uretek technical paper on this subject from: http://bit.ly/2s8vmea