Predicting of Seismic Performance on Tunnel in Weak Soil

Abstract

Main seismic situations have appeared that the tunnels in weak soil may be suffer large seismic damage. Suitable modeling can have great significance for predicting and estimating their seismic acting. This paper examines the effect of the tunneling process and the seismic effect on the tunnel model and the surrounding soil on it. The data of this research is from Almafraq overhead intersection project in the Diyala government, the soil consists of clay and sand layers in which the tunnel is set up. The data obtained from field and laboratory investigations of soil layers and the analysis of the tunneling model by three-dimensional finite element analyses using PLAXIS 3D (V 20), the Mohr-Coulomb (MC) model is employed to demonstrate the behavior of soil-structure interaction in a soil tunnel. Plastic counting was used to act as an elastic-plastic distortion. Three sections are chosen in the vertical direction to experiment with the tunnel's impact and seismic effect on nearby soils. From proceeding FE analysis, the results of calculation by math measurement appeared to main variations in stresses that happen in soils zones nearby the tunnel edges and below the tunnel essentially affect nearness to soils. The increasing pressure becomes smaller as much as you went away horizontally from the tunnel and start to decrease for lengths more than 15m from the tunnel edge's, so it was observed that the most probable safe distance (2D) from the tunnel, which D represents the diameter of the tunnel, this for tunneling. Also, the upper zone of the tunnel considers safer at 58% because it is far from the influence of the earthquake and its soil is clay, while the critical zone locates in contact with the tunnel. Furthermore, it was noted that the amount of settlement of the soil is so little in a phase of tunnelling compared to the dynamic rate of 86%.