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Maccaferri: Evolving solutions

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Maccaferri has developed a range of ground stabilisation products.

Although it has been in business since 1879, it was only in the 1960s that Maccaferri introduced rockfall mitigation to the market followed by geosynthetics in the 1990s.The gabion, which is the solution most people associate with Maccaferri, is now only a minor part of an increasingly service and solution driven portfolio which is focused on overcoming problems facing the industry.

The demands on infrastructure are increasing due to greater usage and worsening operating conditions. Consequently, clients rightly demand higher performance, increased resilience to environmental change and better value, yet they have reduced maintenance budgets. This apparent dichotomy can be mitigated through intelligent selection of solutions and the materials used.

The North Bexhill Access Road(NBAR) project links the A269 to thenew Combe Valley Way and future development land north of Bexhill. Threading the road over poor groundand in close proximity to protected ancient woodland fell to consultant Campbell Reith working for client Sea Change Sussex in conjunction withcontractor Breheny Civil Engineering.

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maccaferri 3

ParaDrain allowed marginal fill to be used on the North Bexhill Access Road scheme

Collaboration between the team and Maccaferri concluded that, as the approach embankments to the highway were to be constructed over soft soils and would require steep faces, a combination of geosynthetics could efficiently address soil reinforcement, foundation improvement and slope drainage.

Designed to BS8006, the foundation design incorporated unique ParaLink high strength uniaxial grids which have the lowest long-term design strength reduction factors in the industry, enhancing the efficiency of the solution. ParaLink reinforcement was placed at formation level to prevent shear failure in the embankment fill and in the foundation soil, improving embankment stability.

The 7m high approach embankment required 70° (approx) side slopes and soil reinforcement techniques were used. Traditional geogrids require that the structural backfill has to have certain minimum performance parameters to function efficiently with the geogrids, but the marginal quality soils on the NBAR would have needed cement stabilisation (or similar improvement) to achieve this. Using ParaDrain geogrids to reinforce the marginal fills overcame this limitation. ParaDrain is a unique soil reinforcing geogrid with a built-in drainage capability. Each of the straps in the primary strength direction features a profile shape that acts as a drainage channel. This creates a multitude of drainage paths through the reinforced soil.

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maccaferri 4

Almost 500m of catch fences were installed along the Handsworth Cutting

The ParaDrain is placed within the compacted layers of the marginal fill,reinforcing it. The drainage function of the geogrids rapidly reduced pore water pressure within the soil. It enabled the reuse of the marginal fills on the Bexhil lsite that would otherwise have been disposed off -site or replaced with imported materials, both of which impact on the environment.

The fascia of the reinforced soil embankments incorporated rock-faced Terramesh and vegetating Green Terramesh units to ease construction and achieve the specified overall slopeface angle. Both these fascia systems utilise “off -site” manufacturing, with all fascia components factory-fitted to reduce work and potential errors on site.

ParaLink and ParaDrain are made in Yorkshire by Maccaferri-owned Linear Composites. The North Bexhill AccessRoad scheme received the Brassey Award (Kent and East Sussex) fo rEngineering Excellence at the ICE South East England Engineering Excellence Awards in 2017.

Enhancing the safety and reliability of a railway was the objective of a project at Handsworth Cutting on the Deepcar to Cleethorpes line.

Originally constructed as Darnall Tunnel with two lines, this was increased to four lines in the early 20th century due to increased coal traffic to Immingham Docks. To create the space for the four lines, the tunnel was demolished in 1912 and the Handsworth cutting was formed. A more recent decommissioning removed the outer two lines, leaving a 5m to 6mwide cess on either side of the remaining tracks.

The cutting consists of coal measures, banks of sandstone and siltstone/mudstone, and has a maximum height of 25m with slope angles of 70° to 80° for the rock faces and 35° to 50° for the soil slopes.

These cut slopes have a history of instability due to weathering, and rockfalls caused a derailment in the mid-1990s.

maccaferri (1)

maccaferri (1)

Steep rock faces were protected by netting at Handsworth

Contractor CML and its designers Aecom with technical support from Maccaferri, proposed a variety of rockfall protection measures. The steeprock faces would be protected with secured rockfall protection netting and rock bolts. Rock and debris falls from the shallower slopes would be prevented from impacting the tracks with a series of rockfall catch fences.

Nearly 500m of catch fences were installed including a Maccaferri RMC050 barrier, with an energy absorption capacity of 500kJ. Tested and certified in accordance with ETAG027, the barrier is also CE marked. The RMC 050 has low deflection under impact, ideal for operating in a restricted area. This is a result of the patented compression brakes which absorb the energy of the impact as the fence progressively deforms.

This innovation reduces the forces transmitted to the uphill and ground anchors. At Handsworth Cutting, the barriers were supplied with a larger base element than normal due to the necessity to spread the impact loadsover the soft ground at foundation level.

RMC 050 is delivered to the site in a kit form; all above-ground elements are delivered direct from the factory and bolted to foundations installed on site to suit the design conditions. Rockfall catch fences within the Maccaferri range are available up to 8,600kJ energy absorption capacity with rockfall embankments up to 20,000kJ capacity utilising our soil reinforcement technology.

Maccaferri managing director Steve Miller believes clients are becoming increasingly open to innovative solutions.“We are encouraged that the infrastructure market is embracing these innovations and see the environmental and value benefits of the reuse of site won materials.  In 2017 we invested in five more engineers to strengthen our ability to meet these demands”.

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