Investigation of the Effect of Soil Reinforcement of sub-way tunnels overhead Using Geogrid to Reduce the Effects of Ssurface Bblasting

Among the most important factors that influence the decision making and planning in passive defense such as structural hardening and especially underground structures such as tunnels and subways are situation estimate and their response to dynamic loading (caused by an explosion). In this regard, one of the effective factors influencing the amount and distribution of load blasting on an underground structure, is burial depth of the structure and condition of soil reinforcement. Therefore, considering the depths of the tunnel of interest (9 and 12m from the tunnel) and four layers of reinforcement (the distance of one meter from each other), computer simulations using ABAQUS software and comparing the obtained results was implemented. In fact, in many cases structural design (e.g a section of tunnel structures) the geometry and depth of the tunnel as a certain value to the project designer were considered necessary in order to achieve the specific goals of the project, while there are no restrictions in terms of soil reinforcement. In this mode, the best conditions for soil reinforcement can be selected. Simulation results show that by increasing the depth of the tunnel from the depth of 12 meters downward, the impact of blast wave on the behavior of underground structures will be depreciated and for explosive charge, depth of 12m can be introduced as the safe depth for tunnel construction with the soil characteristics and an explosion equivalent to 1000 kg TNT. Moreover, by increasing the reinforcing layers of geogrid to three layers, the reduction of possible damage to the underground structure is observable.