The creation of initial site compounds, working platforms and haul roads can have a huge impact on resources for contractors who must take on the associated costs and risks. Shahid Raza, business and technical manager for geosynthetics at Wrekin Products, discusses how these costs are often a neglected hindrance for contractors who could be benefiting from these under-utilised value-engineered solutions
When it comes to creating a safe and practical site, a dedicated compound – comprising a site office, welfare facilities, parking and storage – and haul roads, which enable construction traffic to get from A to B, are vital components.
Geogrid solutions have been around for decades, but many aren’t taking advantage of how they can break down the barriers contractors face when constructing preliminary project works.
Universal challenges faced by contractors
Contractors have a primary requirement to create and maintain a safe environment, both on the construction site itself and the surrounding network, which builds a more positive relationship with the public and key stakeholders.
The conventional approach to the design of temporary works can cause unnecessary congestion and inconvenience for residents and highway users. Site compounds and haul roads are constructed in the preliminary stages of a project. However, these measures are temporary and, understandably, contractors don’t want to spend a large proportion of the project’s time and money on these works – no matter their importance.
As a result, the preliminary works need to be as cost and time effective as possible without impacting on solution performance or project scope. Luckily, value engineering the preliminary works can keep costs under control, while also accelerating the construction programme.
How can solutions solve these problems?
This is where value-engineered geogrid solutions come to the fore. They can reduce the thickness of a haul road, compound or working platform, typically by 30%, resulting in substantially reduced construction cost and time. Along with significant cost reductions, geogrids improve site health and safety, accelerate construction timescales and reduce the project’s overall environmental impact.
This is because, when granular particles are compacted over these grids, they partially penetrate and project through the apertures to create a stiff and positive interlock, offering lateral restraint. The load dispersal effect from the interlocking mechanism increases shearing resistance within the aggregates, improving compaction and allowing the granular thickness to be decreased – ultimately reducing construction time and cost.
The intelligent adoption of geogrid solutions is a two-pronged approach. Not only will there be significant upfront savings during the construction works, but there will be further cost reductions once the infrastructure is in place and it comes to returning the land to its original use. For example, removing a haul road that is 250mm thick as opposed to one that is 600mm won’t require as many resources – this is only effective if using a separation geotextile under the geogrid.
Supporting tender bids
If an engineering manager is engaged at the tender stage, the impact on the savings to reduce time and money can also assist a contractor in winning the tender. However, all isn’t lost if engagement comes afterwards as savings can still be introduced.
Early engagement also means the geogrids can be manufactured to the exact width that the contractor needs, suiting the site-specific requirements and creating an even more cost-effective grid. Simply removing a longitudinal overlap in the geogrid layout can save a further 10% in product costs alone.
An example: Reducing costs ahead for Hinkley Point C nuclear power station
The team at Wrekin Products recently value-engineered a 10km haul road with geogrids in support of contractor J. Murphy & Sons and Balfour Beatty, for the first new nuclear power station to be built in the UK in more than 20 years. When complete, Hinkley Point C, in Somerset, will provide low carbon electricity for around six million homes.
The power station will generate a lot of additional electricity and the existing network and infrastructure isn’t sufficient enough to cope. As a result, previous experience had highlighted the need to engage Wrekin’s technical services as a temporary access road was required so construction traffic could efficiently operate on the site where high voltage underground ducts and cables were being installed.
The site itself had a high level of variability in soils, so a constant cross-section that suited those differing ground conditions was needed.
Without a geogrid value-engineered solution, the client would have needed to install a cross-section in two compaction layers, totalling 550mm of aggregates. However, as the haul road was 10km long, this would have been an additional drain on the resources required for installation – when a single compaction layer at 250mm would suffice. As a result, 100,000 sqm of Wrekin’s products were used. Wrekin’s E’GRID SX 3030 was installed over a layer of its Fastrack FT609 separation geotextile – both with a manufactured width of 4.5m to suit the subgrade interface.
This substantial reduction in founding thickness significantly reduced the impact on costs and the environment. But most importantly, it accelerated the construction process, therefore recouping time and money. The ultimate exhuming of the temporary access road once the project is complete will also be much more cost and time-effective.
The project also highlighted the importance of early contractor involvement as it enabled J. Murphy & Sons to make the savings upfront, which was of prime importance to keep costs and risks under control, while accelerating the programme.
Here, we focus on a scheme in the power sector, but preliminary works are a prerequisite and yet often overlooked part of most construction projects across all sectors. Value engineering offers a simple and efficient way to save time and money while reducing the environmental impact of a project.
Contractors not only need to recognise this, but also that value engineering with geosynthetics goes well beyond financial rewards – it can accelerate the construction programme and reduce haulage, which positively impacts all road users. Fewer HGVs on our network won’t just lower carbon emissions, it also means less damage caused to the existing networks. Value engineering reduces resources and any such reduction in resources will improve the health, safety and wellbeing on a project and could ultimately save lives.
Shahid Raza BEng(Hons) CEng MICE
Business and technical manager for geosynthetics
LinkedIn: Wrekin Products Ltd