Considerations for rock mass grouting for tunnelling in faulted rock masses with tubes á manchette

Grouting into an open borehole is a process that has been well described academically. Numerous grouting techniques and grouting criteria are available for various applications and combinations of rock mass/ground. Tube á manchette (TAM) or sleeve port grouting systems have until now mostly been used in specialized civil engineering work in soft ground. In order to be able to carry out grouting successfully in faulted rocks, cased drilling is necessary in order to maintain the stability of the borehole for the insertion of the sleeve pipe. Under these premises, fundamental considerations for successful TAM grouting in faulted rocks are presented. The rheological properties of the grout used, the form and size of the injection opening and the strength and thickness of the sheathing compound significantly influence the penetration into the surrounding rock mass. Increased effective pressure is necessary in order to break through the sheathing compound and also to overcome friction losses during the grouting process. The necessity of high effective pressure and the emergence of the grout at the sleeve ports can, in contrast to an open borehole, increase the risk of jacking the ground in the course of grouting and this has to be carefully taken into account and investigated in advance. The interaction of effective grouting pressures and friction losses of the grouting system and their effect on the grouting process in faulted rock are described through the formulation of a general grouting criteria for TAM grouting. © 2019, Ernst und Sohn. All rights reserved.