Prediction Of Displacements In Tunnelling

When tunnelling through fault zones under high overburden large deformations are frequently observed, creating a variety of problems. One of them is the accurate estimation of the amount of overexcavation required. So far, methods for estimating displacements are not proven. In squeezing ground the lack of effective displacement prediction may lead to reshaping or backfilling overexcavation with concrete in cases where displacement estimation was too high. Modern tunnelling methods are based on monitoring and interpreting displacement measuring data as well as geological and geotechnical information. Systematic monitoring of absolute wall displacements to determine the appropriateness of support quantity and type to control tunnel stability is an integral part of the design of underground openings and an important feature of the NATM. The NATM considers the variations in local geological and geotechnical conditions and demands flexibility of support and excavation method. For safe and economical tunnelling under squeezing conditions a continuous adaptation of the support and excavation concept is required. Simple, quick and effective tools are needed to predict displacement behaviour. On the basis of analytical functions, artificial intelligence and the use of stored experience, a method is being developed to predict displacements. The required input parameters can easily be acquired at the face. The procedure is prepared to consider several options, such as installation of support, simulation of sequential excavation and non steady tunnel advance.