Study on Electrical Characteristics of Magmatic Rock Intrusions in Metamorphic Rock Formations—Taking the Mupi Tunnel of Jiuzhaigou-Mianyang Highway as an Example

Abstract

The stratum lithology and geological structure of the highway tunnel in the mountainous areas of western China are complex, and the engineering geological conditions are complicated. When the highway tunnel passes through different lithological strata, its structural design and construction are completely different. Therefore, the design and construction of the supporting tunnel are used in the tunnel survey. The identification of the contact boundary between magmatic rock and metamorphic rock and the grade of surrounding rock is very important. The data processing, forward numerical simulation, 1D, 2D, and 3D inversion of the G8513 Jiuzhaigou-Mianyang Expressway Mupi Tunnel survey by magnetotelluric method reveals the ground level along the design line of the tunnel to the depth of 50m depths within the design elevation of the tunnel. Electrical characteristics, focusing on the identification of the contact boundary between magmatic rock and metamorphic rock. This study provides the electrical characteristics of the magmatic rock and metamorphic rock contact boundary of the Mupi Tunnel. It is speculated that the boundary is revealed by the tunnel construction excavation, which verifies the correctness of the geophysical inversion model and provides a more detailed design basis for the tunnel design. It is believed that taking the Mupi tunnel survey as an example, this research can provide detailed geophysical basis for the identification of magmatic rock and metamorphic rock in highway tunnels, as well as the geological survey and design of highway tunnels.