Study on the Vehicle-Induced LTAS Law of the Tunnel in Diatomite Area

Abstract

Due to the weak characteristics of diatomite, excessive settlement may happen under long-term dynamic vibration load and affect the later operation of trains, while there are few researches on the dynamic response of highway tunnel in diatomite yet. Taking the Feifengshan high-speed railway tunnel project as the study case, the impact of different reinforcement parameters on long-term accumulated settlement (LTAS) rule of the highway tunnel in the diatomite area under train load is studied by numerical simulation and layer-wise summation method (LWSM). The results reveal that tunnel LTAS in diatomite area mainly appears in the first and the second years of the running stage of train, and the LTAS in these two years accounts for half of the ultimate stable LTAS. The longer the pile length (PL) and the larger the pile diameter (PD), the smaller the dynamic deviatoric stress (DDS) and LTAS. However, when pile lengths or pile diameter exceed a certain range (PL = 16 m or the PD = 150 mm), the control effect of increasing the PL and PD on the LTAS of the tunnel in diatomite is no longer significant. This indicates that there exist preferred values of the PL and PD. There are few cases of the construction of highway tunnels in the diatomite area before the engineering project in this paper yet. Hence, this paper will provide a reference to the construction of the foundation reinforcement scheme of high-speed railway tunnels in diatomite layer.