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Abstract
In the design of underground excavation supporting structures, vehicle loads are generally considered as a constant distributed load of 20 kPa in the practical design method, and the equivalent soil layer method is also used. However, these methods do not take into account the dynamic properties of vehicle loads, and are relatively conservative in considering the influence of vehicle loads. Aiming at this problem, an improved method is presented to better solve this issue. Following the vehicle dynamics theory, vehicle loads are composed of static and dynamic loads; the quarter-truck model with two-degrees of freedom is introduced to simplify vehicle loads. According to motion differential equations of the two degrees of freedom vibration system, the dynamic vehicle load is deduced and expressed as a simple harmonic load. In an underground subway station, this simple harmonic load conversion method was introduced to convert the vehicle load, and was compared to the equivalent soil layer method and practical design method through numerical simulations. Some lateral displacement curves of supporting structures and settlements of road surfaces were obtained. The results revealed that the simple harmonic load conversion method can effectively reflect the influence of vehicle loads in the design of underground excavation-supporting structures..