DYWIDAG's contribution to the UK’s largest soil nailing project
The M1 motorway links London with the North of the country, and was widened to improve traffic flow. DYWIDAG was chosen as a trusted and reliable supply partner.
Context
The M1 was built in the 1950’s and is one of the most important and trafficked roads in the country. Consequently, the motorway needed to be widened north of London between junctions 10 and 13, between Luton and Milton Keynes.
Solution
For stabilizing the motorway embankments, DYWIDAG supplied 17,000 Type R38 DYWI® Drill Hollow Bar soil nails, in lengths of 6-10m and with a total length of 150,000m as well as Ø 25mm GEWI® Soil Nails for the clay areas. All the soil nails are galvanized, with formed bearing plates and domed nuts for angle compensation.
The engineer chose to use hollow bars because they allow simultaneous drilling and grouting, and ensure that grout is placed at all points within the ground as drilling is advanced.
DYWIDAG worked closely with the drilling contractor in order to design the most suitable drilling equipment that could access the embankments.
Furthermore, DYWIDAG consulted with the contractor on the selection of rotary percussive top hammers (drifters) to ensure correct rotation speeds (120 RPM) and blow rates of the hammer (400-600 BPM).
DYWIDAG also tested the soil nails and developed a testing method for the hollow bars with the designers. In this method, known as the long and short nail testing method, tests are applied to sacrificial soil nails, and the resulting design load is calculated by taking the load of the short nail away from that of the long nail. Thanks to this method, bond stress in the stable zone can be quantified.
Construction work was carried out on only one lane at a time, in order not to minimize disruptions to traffic.
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