Sharp curve auxiliary method
Sharp curve tunnel construction contains a high degree of technical difficulty and therefore requires additional methods to be applied during the tunnelling process. Conventionally, surplus material around the machine was supported via additional construction which was undertaken from ground level. Due to increasing restrictions from road traffic, over-ground inconvenience caused by these processes as well as underground obstructions such as neighbouring buildings, TAC has developed the “Clay Shock Mini-Packer” construction method. Due to the effects of infiltration, the risk of unsatisfactory backfill grout injection back of segmental lining become high. The segmental lining behind TBM will be free from the ground, and very unstable. This is an additional method which totally removes the need for ground level obstruction, and which can carry out sharp curve construction safely while reducing the damage and deformation imposed on the segment by the thrust force generated by the TBM while at the same time being friendly to the environment.
The Characteristics of Clay-Shock and Mini-Packers.
TBM Progression without Clay Shock or Mini-Packers
TBM Progression with Clay-Shock and Mini-Packers in use
While the wider overcut produced by the copy cutter is un filled, it is extremely unstable. With Clay-Shock injected into this oversized portion of the annular overcut, ground collapse from the cut can be prevented and a reduction of the thrust force needed to propel the TBM due to lower friction between the TBM and the excavated void is produced. The Clay-Shock also, by design, prevents infiltration of the Backfill Grout material into the overcut when Simultaneous Backfill injection is being carried out, killing two birds with one stone. Quick setting Backfill Grout Material is injected into the Mini-Packer bags via the segmental lining, which has the effect of totally eradicating deformation of the segmental lining from thrust from the TBM. This produces more stable tunnels, much more improved attitude control and makes for all round stable advance of the TBM.
Mini-Packer is a Limiting Injection Bag for Backfill Grout, which prevents the infiltration of backfill grout material into the outer periphery of the TBM, and fixes the segmental lining securely to the ground, while providing essential thrust stability for the TBM while cornering.