Weldgrip Gripforce ® Rockbolts, Drilling Machines, Drill Steels and PVC Coated Steel Mesh

Project Title Flood Risk Management - Reinforcement of Riverside Wall Client Environment Agency Consultant Halcrow Main Contractor Jackson Civil Engineering Drilling Sub Rockbolting Technology Featured Products Weldgrip Gripforce ® 22mm Anchors withGrout Retention Sock. Weldgrip Turmag hand held drilling machine.

The Matlock Bath floodwall encountered high flood levels from the river Derwent in 2000 and as a result a section of wall partially collapsed, leaving nearby properties exposed to the floodwaters. Considerations to rebuild the wall were discontinued due to the high traffic levels on both the road and footpath.

Halcrow were then appointed to carry out a structural survey and it was later identified that 330m of the floodwall was at risk from collapse. These findings lead to the Environmental Agency to propose a scheme to both raise and reinforce the wall to give a 1 in 100 year flood protection. Trials were carried out to prove if reinforcing the wall could be carried out successfully. Due to the make up of the wall grouting trials proved that grout could not be contained in open holes, and could contaminate the river and damage underground services.

Further trials using a grout retention sock and hollow fibreglass tube, in 44mm holes drilled with Turmag hand held drilling machine proved successful. The grout could be pumped down the tube filling the grout retention sock from the bottom up. The grout was retained and the sock would expand at the mouth to confirm the hole was full.

This gave quality assurance on the reinforcement being fully encapsulated. From these trials the suitability testing was carried out using 22/12mm Weldgrip Gripforce ® anchors in lengths between 1.5m and 2.4m fitted with grout retention sock along their length. The pull tests proved successful with the anchors being tested to 45 kN proving their bond strength in the stone wall.

The Gripforce ® anchors are BBA approved (certificate no. 01/R123) which details the design criteria for up to 120 years design life, and includes the use of grout retention sock. Work began in February 2005 and the drilling was completed in 4 weeks. In total 440 reinforcing anchors were installed and grouted successfully, and the wall height was increased in some areas to minimise the flooding risk.

Gripforce ® Anchors with a grout retention sock were chosen because:

• They have high corrosion resistance.
• They have a 120 year design life.
• The use of anchors allowed better operational grouting.
• They satisfied the required anchor performance.
• The quality controls for installation and grouting were satisfied.

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Weldgrip are also proud to have attained BBA accreditation and ISO 9001 standards in recognition of our continuing excellence in Geotechnical products and services.