ABSTRACT
Swelling and squeezing rocks have different deformation mechanisms. However, significant deformations may occur in both rock types in rock engineering. Determining the most appropriate support system in swelling and squeezing rocks is one of the major challenges for rock engineers because there are many facts and issues to be considered, such as the type and performance of the support, the support elements, the rock mass parameters, the condition of the rock mass structure and the creation of an appropriate support strategy. Alongside all of these issues, parameters such as excavation geometry, round length (distance from face to the support) and excavation rate affect the support performance directly. The TH-type steel supports, developed by Toussaint and Heintzmann, that were first used in deep underground mine headings in the 1930s, have recently been used in tunnels as ‘yield-control support systems’. However, the sliding capability of the TH steel support allows cross-section contractions. If the amount of convergence cannot be calibrated, reshaping studies have to be carried out at the excavated areas due to the occurrence of time-dependent creeps, especially in swelling and squeezing rocks. This situation increases the project costs and causes significant delays.
There are many support-system analysis techniques, including the convergence–confinement method, the yielding support system, and empirical and semi-empirical support analysis. The Non-Deformable Support System is one such support-system analysis method. It is typically seen as a numerical analysis and although numerical modeling is the key tool of this system, it is not the only one. Although the name of the system gives the impression that there is no deformation in the support system, this is not the case. The system contains some deformation but only to a certain tolerance determined by numerical analyses of the time-dependent deformation behavior of rock masses.
