Investigation of the Influence Area of the Excavation of a Double-Line Highway Tunnel under an Existing Railway Tunnel

The research on the impact of the excavation of underpass tunnels has already had certain results, but there is a lack of research cases of double-line highway tunnels with oblique angles under the existing railway tunnels, especially the method of determining the area of the impact of the dynamic and static loads of new tunnels and existing trains, which can be enriched by considering them at the same time. This paper, is based on the tunnel project of the new double-line Shiqian highway tunnel with oblique angles under the Hurong railway in Wanshoushan. By constructing a three-dimensional finite element model and simulating the application of static tunnel excavation load, dynamic blasting load, and dynamic train operation load of the existing tunnel, the overall displacement of the existing tunnel and the settlement value of the bottom plate of the track surface by the static tunnel excavation load were analyzed. Then, the stresses, vibration speeds, and displacements of the tunnel due to the dynamic blasting loads and the dynamic train operation loads were obtained. The results show that the area of influence of the static loads of the new tunnel excavation on the existing tunnel is divided into three types of perturbations presenting strong, weak, and slight; the area affected by the blasting dynamic load of new tunnel excavation is a circular domain with the datum point in the tunnel section as the center; the area affected by the dynamic load of train operation in the existing tunnel is an ellipse with the center of the track surface of the existing tunnel as the datum; and there is an anomalous shape in the area affected by the blasting dynamic load of new tunnel excavation and the area affected by the dynamic load of the train operation in the existing tunnel.