Lateral support for cuts and fills on National Route 1, Section 21, between Lynnwood Road and Rigel Avenue

摘要

Soil nails were installed as excavation proceeded. The face of the cutting was initially machine excavated, but final trimming was done by hand. Once the lines and levels to the tolerances of +0 mm (i.e. towards the outside of the face) to -50 mm (i.e. into the soil face) had been attained, the drainage strip was applied, followed by a flash coat, 25 mm thick. The holes for the soil nails were drilled through the flash coat and the grout pumped into each hole from the base of the hole so as to ensure that the complete hole was filled with grout. When the grout overflowed from the face of the hole, the soil nails were installed with spacers to ensure that they were centrally located within the holes. Where the soil face was very stable, this procedure was altered to suit the contractor's requirements in that the soil nail and grout were in some cases installed prior to the application of the flash coat.