PREDICTION OF SURFACE SETTLEMENT AND INNER FORCES OF LINING OF HORSESHOE-SHAPED TUNNELS BY USING ARTIFICIAL NEURAL NETWORKS

Generally, the Earth is under the force of actual stress, and any disturbance such as tunnel excavation disarranges the stress condition and surface displacements. If these displacements are not in a standard range, it can cause some problems to the surface and lower level of structures.At the time of tunnel excavation, some parameters such as cohesion, friction angle, elasticity modulus, tunnel diameter, and tunnel space affect the surface settlements and inner forces of tunnel lining. Therefore, the prediction of these displacements and forces plays a vital role in tunnel design. In this research, at first, three base models in the Plaxis software are modeled; then, the effects of the mentioned parameters on surface settlements tunnel lining forces are assessed. In these models, geometry range is rectangular such that two lateral sides are allowed to have vertical displacement. In addition, nether side in vertical and horizontal direction has closed. Closed nether side shows a stone bed. The model is considered to be plane strain, and tunnel shape is considered as a horseshoe-shaped section. Ordinarily, soil environment has different properties and behavior varieties. There are several behavior models for soils from which Moher-Columb model is selected and used in this research. According to the analysis, an increase in cohesion and elasticity modulus causes a decrease in the surface settlement; however, increasing the friction angle or tunnel diameter causes surface settlement enhancement. In the following, attempt has been made to forecast the surface settlement and inner forces of tunnel lining by using artificial neural network (ANN). Obtained results of software have been modeled by artificial neural network (ANN). For this purpose, at first, the network is
expanded; then, the mentioned parameters are analyzed to evaluate the results. In this paper, considering different parameters, sensitivity analysis for displacement and inner forces of lining is conducted. Results indicate that these parameters have significant effect on surface settlement and forces of lining.