Modern pre-injection in underground construction with rapid-setting microcements and colloidal silica - applications in conventional and TBM-tunnelling

The pre-injection method of injection ahead of the excavation face in underground construction can offer significant advantages in many situations. This is particularly the case in difficult ground conditions with water ingress or in mechanically poor ground or soil, in which pre-injection can help avoid problems and serious delays. Modern cost-effective methods and material technology for pre-injection in underground construction aim to achieve the desired result as fast as possible, hence reducing downtime during the excavation as much as possible. This paper reports a successfully resolved difficult case in which pre-injection with rapid-setting microcement was employed in combination with colloidal silica. The recent further improvement of the technical performance and versatility of rapid-setting microcements through the use of controlled and precise addition of accelerators is also reported.