CASE STUDY SERIES #10

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1 THE PROJECT PREMIER INN & RESTAURANT APPLICATION MASS GRAVITY FREE-STANDING GABION WALL LOCATION UXBRIDGE, GREATER LONDON DATE OCTOBER 2015 CLIENT ARCHITECTS DESIGN/BUILD CONTRACTOR SEGRO AXIOM ENVIROMESH MCLAREN GROUP LTD

2 PROJECT BACKGROUND SEGRO, Europe s leading owner-manager and developer of industrial property, secured detailed planning consent from the London Borough of Hillingdon to construct 501 Riverside Way a 37,240 ft 2, 80-bedroom Premier Inn hotel and Beefeater Grill restaurant, together with a speculative 26,430 ft 2 industrial unit, at Riverside Way, Riverside Estate, Uxbridge. The scheme forms the final phase of development at Riverside Way, which extends to 172,000 sq ft, and is home to companies such as Bosch, Manpower plc, Monster Energy, Kommerling UK and Aristocrat Technologies. Once completed, the hotel and restaurant will seek to create 60 jobs, with SEGRO and Whitbread committing to target around half at long-term unemployed people in the borough. Further employment opportunities will be created once the speculative industrial unit is let. The first photo (above, left) illustrates the dual core fills that are separated by the pre-fitted geotextile to prevent migration of fills. Central photo, above, highlights the need for the temporary positioning of external scaffold tubes to hold the face whilst manually filling the external face. The final wall (above right), end-on, post construction. DESIGN BRIEF The Enviromesh team were approached by McLaren in August 2015 to discuss the project at Uxbridge and the requirement for a 30 metre long, 3 metre high free-standing gabion mesh wall. The wall would be installed in a prominent location as part of the frontage and alongside the new Premier Inn and Beefeater restaurant. So the installation would be on continuous public display. As an architectural screen the finished gabion wall would play an important role in terms of its contribution to the overall visual impression of the finished site. Additional consideration for exposure to wind loadings and pedestrian traffic either side of the wall would need to be addressed by means of detailed surveys and calculations.

3 THE CHALLENGE The three key challenges on this project were quality, build time and budget. The deadline for Enviromesh to complete the wall was before the end of October 2015 as a result of the site nearing completion with areas still to be block paved and landscaped. Having assessed the structural, aesthetic and time constraints, Enviromesh allocated seven men to the job, working both week days and weekends. This would ensure that any unforeseen issues could be planned for well in advance and within the overall build schedule. Planning and coordination with timed delivery slots for heavy materials (mesh baskets, aggregate and granite rockfill) via our logistics department, enabled us to keep well ahead of schedule. The gabion wall was designed to form an architectural screen which would run adjacent to a new glass-fronted Beefeater restaurant. As a high profile installation on full public display, the finished wall understandably had to be of the highest quality in aesthetic terms. From left to right: Gabions showing the filling process. The outer cells were filled first to stiffen and align them prior to machine filling and compacting the central 20-40mm shingle core. The steel stanchion supporting the canopy was partly encapsulated within the gabion wall. Facing-off of the wall with the 6G granite stone supplied was critical to the project and is an aspect of the work that the installation team are experts in. Eventually the wall will be planted as a follow-up to the final landscaping requirements. The modification required that Enviromesh fabricate the welded gabion mesh to suit the design change, prior to installation. On this occasion we were able to easily accommodate a steel supporting column that had been installed as part of the earlier canopy construction. Following acceptance of our designs, costings and works schedule, Enviromesh commenced work on the site in October Additional build constraints included working beneath an existing canopy with a clearance of just 800mm as we moved towards completing the final course. The location of an existing steel stanchion in the line of the wall required a modification to the design that was duly accommodated within the integral structure of the wall. As with any construction site, health and safety issues are our primary consideration. Enviromesh takes time to prepare its own procedures in addition to any site-specific conditions that may be required to ensure our method statements comply with and include all necessary risk assessments for both site personnel and heavy plant equipment.

4 SERVICES PROVIDED BY ENVIROMESH Preliminary meeting with parties mentioned above to agree the design, materials specification, design life, stone type/colour and construction process Free-standing wall design, detailed design proposals and layout drawings For Construction Use Liaise, visit and provide Granite 6G gabion stone facing samples from Aggregate Industries in Leicestershire mm core gravel was sourced locally to London to obtain architect approval Purchase, supply and coordinate 100 tonnes of 6G gabion stone and 80 tonnes of 20-40mm shingle Pre-fabricated gabion mesh baskets (twin-cell, geotextile lined) at our Stoke manufacturing facility in order to separate the dual fills and speed construction Dedicated and experienced team of gabion wall construction personnel (to fabricate the gabions, joint fill and fair face the baskets on all sides) Provide a buggiescopic machine to deliver stone to the operators, scissor lift for working at height, compressor and pneumatic tools PROJECT BUILD COMPONENTS, SUPPLIED BY ENVIROMESH Gabion mesh test panel, built prior to the commencement of work undertaken (for approval by all parties on gabions, stone types and fixings) Welded steel wire mesh gabions manufactured from 75mm 75mm 3mm wire diameter (fitted with a 4mm face panel to achieve high aesthetics on both front, rear and end panel) Two grades of stone: 6G gabion stone, 20-40mm aggregate infill All fixing accessories including: CL50 C rings and lacing wire Galfan coated hog rings for jointing on site 6m long scaffold tubes to provide face alignment during the build Thermally bonded, non-woven, geotextile membrane Very impressed with the professionalism of the Enviromesh installation team they conducted themselves impeccably. Their work ethic demonstrated throughout the project by the long hours put in and the attention to detail they gave to the finished wall. MCLAREN GROUP Gabion free-standing wall material specification: Fabric type Bi-axial welded mesh BS EN Steel wire and wire products (general wire dimensions and tolerances) Tensile strength (wire) 540 to 770 N/mm 2 Weld strength 75% of the minimum ultimate tensile strength of the wire BS EN (Class A) Zinc and zinc alloy coatings on steel wire BBA certification Design lifespan up to 70 years in a mild environment

5 PREMIER INN FREE-STANDING WALL See design detail below. The wall was built on a concrete foundation to ensure no undulations would reflect through the structure. Gabion fill (Class 6G) STONE SPECIFICATION Total wall volume: 87.75m 3 6G Granite facing cell (40.50m 3 ) 20 40mm shingle-filled cell (47.25m 3 ) Granite faced with shingle infill 20 to 40mm MATERIALS Infill was 6G gabion stone, and specified as Granite supplied by Aggregate Industries in Leicestershire. The wall occupies a high profile location and the stone hand-coursed and fair-faced by hand.

6 WIND LOADING CALCULATIONS Standard wind speeds Vb m/s Site altitude Site Wind Speed, Vs Sa Sd Ss Sp Vs m/s Wall elevation 12.0m 6.0m 0.9m Stanchion to overhead canopy Hr m He m Free-standing walls and parapets Return Corners Return corners at both ends? Is return wall longer than 1m? Effective Wind Speed, Ve Distance km Sb Terrain Sb Ve m/s No Yes Wall dimensions Height (m) Dynamic Pressure qs N/m town Length (m) 3 29 End of wall A B C D h Wall elevation Size effect factor, Ca Net Pressures on wall, p Site exposure type C Zone A Zone B Zone C Zone D Diagonal dimension (m) Solidity Ca Cp p (N/m 3 )