Petr Salak to Present at Eastern European Tunnelling Conference in Prague

The ITA-AITES Czech Tunnelling Association is preparing for its 13th International Conference entitled “Underground Construction Prague 2016”, taking place in Prague, from 23rd to 25th May 2016. This is the largest Czech tunnelling conference which is held every three years. The 13th International Underground Construction Prague Conference is enhanced this year as it is combined with the 3rd Eastern European Tunnelling Conference (EETC 2016), a biennial regional tunnelling conference. The event aims to promote the sharing of knowledge, experience, skills, ideas and achievements in the design, financing and contracting, construction, operation and maintenance of tunnels and other underground facilities throughout the countries of Eastern Europe, with agreed aims and in a structured manner.

On Monday 23rd May, Petr Salak (Senior Tunnel Engineer at Dr. Sauer & Partners) will present a paper entitled: Determining trigger values for in-tunnel monitoring of shallow tunnels. The paper was authored by A. Nasekhian, A.R. Onisie-Moldovan and P. Spyridis from Dr. Sauer & Partners, London, UK. The abstract for the paper follows below:

On determining trigger values for in-tunnel monitoring of shallow tunnels
It is a common practice to define a traffic light monitoring system to manage the in-tunnel deformations occurring during tunnelling. This system comprises four zones including green, amber, red and black. The purpose of this paper is to present a methodology to determine trigger values for each individual zone. A three dimensional Finite Element Analysis is used to simulate a metro size platform tunnel, modelling the excavation sequences of an SCL tunnel in detail. The amber trigger value is set based on the 3D model predictions of lining displacements expected to occur using a “best estimate” parameter set. In order to determine the red and black trigger values a sensitivity analysis is carried out, varying certain properties of the soil that influence the lining deformations. The purpose of the sensitivity study is to assess how the variation of input parameters can affect the model predictions and whether the impacts can be still sustained by the lining capacity.

The coefficient of earth pressure at rest (K0) and elastic modulus of the soil layer (E) have been identified as key parameters that impact the lining internal forces and the ground deformations. The impact of the parameters on the ground movement is examined within the range of uncertainty available in the project. The results of the sensitivity analysis are used to determine the relationship between the lining deformations and the induced internal forces (Axial force and Bending Moment) for different scenarios, which are the basis to derive the formulation for red and black trigger values.