Elasto-plastic analysis of stresses in the pillar zone of twin interacting horse shoe tunnels
imran ahmad khan1; Kumar Venkatesh1; R.K. Srivastava1
1 Civil Engineering Department, Motilal Nehru National Institute of Technology, Allahabad
Resumo
In urban areas due to scarcity of land, development of modern infrastructure system has now become a big challenge for geotechnical engineers. The problem can only be resolved by maximum utilization of area under the ground surface. As the underground openings are very complex in nature, the situation becomes more complex when two or more tunnels are excavated simultaneously or sequentially because the interaction effects plays an important role in multiple tunneling system. Therefore proper analysis is required in the form of observation of in situ stresses, induced stresses and related deformations when multiple tunnels are excavated. In Indian subcontinent single horse shoe tunnel section has been generally used in the hydroelectric power projects as well as in railways and highways projects. But with increasing demand multiple horse shoe tunnels are also a feasible option. Therefore the need arises for a detailed interaction analysis between multiple horse shoe tunnels and hence a systematic parametric analysis has been carried out and reported in this paper. The present study depicts the plain strain elastic and elasto-plastic finite element analysis of two parallel interacting horse shoe deep tunnels. For the elasto-plastic analysis Hoek-Brown yield criteria has been adopted. Three pillar width (W) to diameter (D) ratios (W/D) have been introduced for each of three considered insitu stress ratio (K0) in the rock mass. The tunnels have been considered to be excavated simultaneously. Variation of principal stresses in the pillar zone and at the tunnel boundary have been studied in the analysis. The results have also been compared with the results of that excavation of a single horse shoe tunnel. It is concluded that for W/D = 0.3, in the case of elasto-plastic analysis of interacting tunnels most of the rock mass in the pillar zone gets yielded resulting in the development of very low principal stresses. For elasto-plastic analysis of interacting and single tunnels, it is founded that the difference in major
Palavras-chave: deep tunnels; finite element analysis; Hoek-Brown yield criterion; underground opening