UNDER-TRACK CROSSING INSTALLATIONS AT WESTON-SUPER-MARE

Excavation process was initiated following the marking of shaft pit locations by our setting engineer in accordance with the AFC design and the permit approval, utilizing a dig-and-push technique to create a 3.4m-deep drive pit (4m x 4m) and a 2m x 2m reception pit, both with a depth of 3.4m.  

In order to accommodate the guided auger-boring equipment, reinforced concrete thrust walls were constructed in the drive pits, with two sides measuring 300mm thick and the other two sides measuring 500mm thick. The construction of formwork walls involved the use of shuttering ply, timbers, and reinforcement A393 mesh. Once the concrete was poured into the formwork, the walls underwent testing to ensure that they had achieved the required strength as per the design specifications.

Following confirmation of the bore’s set-out and mark line gradient by Enable Design engineers, as well as the signing of the drilling permit, the auguring process commenced. This involved using a sacrificial steel sleeve, which was connected through welding of additional sections. The sleeve, flight auger, and cutting head were loaded onto a 13t machine and lowered under the supervision of a qualified slinger signaller and banksman. The cutting head was attached to the rear of the pilot rod, while the flight auger was connected to the drive of the auger machine.

We began Boring with the auger being filled, and as the sacrificial steel sleeve was pushed into the ground, the flight augers were simultaneously rotated. The flight augers were then retracted to the drive shaft, clearing any loose spoil that remained inside the sleeve. Each section of the flight auger was disconnected and lifted to the surface as it arrived in the drive shaft. The spoil from the augers was discharged into the drive shaft, loaded into skips, and removed from the pits using the 13t machine. The spoil removal process was closely monitored to assess its correspondence to the volume of the installed sleeve, with an expected increase of approximately 15-20% after accounting for bulking. Upon completion of the auger-boring, the auger machine master frame and ancillary items were removed.