Analysis and prediction of surface vertical Z-level in granite geology

A finite element model of 'train-orbit-tunnel-stratigraphic' was established with the artificial boundary method to study the environmental vibration caused by subway train load in granite geology and its propagation law in rock formation. The dynamic finite element analysis of the geological model of six sensitive points is carried out respectively, and the variation law of surface vibration acceleration and surface Vertical Z-Level with horizontal distance is obtained. It was found that if in a tunnel-covered rock formation, the ratio of the total thickness of the strongly weathered and intermediate weathered layers to the buried depth of the tunnel is less than 0.5, then the maximum of surface Vertical Z-Level appears directly above the tunnel. If the ratio is more than 0.5, then the maximum of surface Vertical Z-Level appears at a horizontal distance of 10m from directly above the tunnel. Therefore, based on parameters such as tunnel depth and horizontal distance, the equivalent elastic modulus of the stratum and the stratum quality coefficient were innovatively introduced. Through a large number of calculations, the prediction formula of the Vertical Z-Level of the rock stratum is obtained and applied to the construction of Qingdao Metro Line 3.