CASE STUDY
EX-SITU SOIL STABILISATION FOR THE CONSTRUCTION OF A PILING MAT AND LOCKING IN CONTAMINATED LAND
PORTSMOUTH, 2008
CLIENT: BALFOUR BEATY
Industry: Civils
For civils industries, we offer a permanent and temporary Soil Stabilisation solution, for projects where large areas of ground material needs treatment, whithout having to remove material from site.
Application: In-situ
Application: Ex-situ
Our ex-situ application is for large, open projects where there is an on-going requirement for stabilisation, or sub-base material in large quantities and there is space for the stockpiling of spoil material onsite.
EXECUTIVE SUMMARY
This case study highlights the successful utilization of Ex-Situ SMR application for constructing aPiling Mat in the Gunwharf Quays area of Portsmouth. By overcoming the challenge ofcontaminated spoil and the associated costs, the SMR method provided significant financialsavings, improved engineering performance, and reduced environmental impact.
PROBLEM STATEMENT
The project initially planned to remove and replace around 10,000 tonnes of spoil with Type1MOT stone for the Piling Mat, but 6,000 tonnes were found to be contaminated with mixedmetals and categorized as hazardous waste. The challenge was to find an economical andenvironmentally responsible method to create a sub-layer with a 30% CBR engineeringperformance.
THE SMR SOLUTION
The chosen solution involved on-site mixing of SMR batch-mix with the contaminated spoil todry it out, bond particles together, and achieve the required engineering performance. With thismethod, there was no need to separate hazardous waste as SMR locks in the contaminants. Allspoil would remain on site and be re used.
Upon testing, it was calculated that one and a half 25KG bags of SMR were needed per cubicmetre to treat the excavated spoil and achieve the desired result. Therefore 7425 25KG bags (atotal of 186 tonnes) of SMR were needed.
The SMR was thoroughly mixed with the excavated spoil using a 30 tonne, 360 degreeexcavator, with one bag of SMR being added per bucket load. The curling action of the bucketwas all that was needed to mix the SMR into the excavated spoil. The SMR treated spoil wasthen returned and compacted using a Bomag 140 Roller to achieve the required 550m2 PilingMat.
RESULTS
Through thorough mixing and compaction with SMR, the contaminated spoil was encapsulatedand transformed into a sub-layer with an average CBR of 500%, exceeding the engineeringperformance requirements of 30%. This success demonstrated the effectiveness of the SMRmethodology in achieving the desired outcomes.
Using our SMR solution also created substantial financial savings for the project, listed below;
*Data is correct as of the release of this Case Study
Traditional Method
Disposal of contaminated spoil at £100 a tonne x 6000 tonne
£600,000
Disposal of uncontaminated spoil at £10 a tonne x 4000 tonnes
£40,000
Replacement Type1 MOT stone at £15 a tonne x 10,000
£150,000
Total £790,000
SMR Method
186 tonnes of SMR at £284 a tonne
£52,824
Other costs (labour, plant, fuel)
£20,000
Total £72,824
As you can see, there was a saving of over £700,000!
BENEFITS
Financial Savings: The SMR solution delivered cost savings of over £700,000 compared to thetraditional approach, ensuring a highly cost-effective solution.
Enhanced Engineering Performance: Achieving an average CBR of 500% provided a sub-layerthat far exceeded the 30% CBR requirement.
Reduced Lorry Movements: Retaining and reusing all spoil on-site resulted in approximately999 saved lorry movements, minimizing transportation impact.
Contaminant Management: The SMR approach allowed contaminants to be locked in andreused on-site, eliminating costly disposal.
Zero Landfill: By diverting all 10,000 tonnes from landfill, the project significantly reduced itsenvironmental footprint and impact.
CONCLUSION
The Gunwharf Quays Piling Mat project illustrates the successful implementation of Ex-Situ SMRStabilisation, showcasing substantial financial savings, superior engineering performance, anda reduced environmental footprint. SMR’s adaptability and effectiveness makes it a valuabletool for overcoming complex challenges in construction projects.
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