The Study of Hydrochemical Kinetics Fractal Index Assessment Technology for Karst Development Degree: An Example from Xin Gaopo Tunnel

The karst form and the water gushing are two major geological disasters in the construction of karst tunnels, which seriously threaten the safety of tunnel construction. This paper adopts the hydrochemical kinetics fractal index for karst development degree evaluation model, starting from the macroscopic and microscopic characteristics of karst development, combining the evaluation index of conventional karst development degree, fractal characteristics of karst form, hydrochemical kinetics parameters and hydrochemical fractal characteristics, and passing the karst morphological fractal index and hydrochemical fractal index to comprehensively evaluate the degree of tunnel karst development. At the same time, based on the evaluation results of hydrochemical dynamics-fractal theory, the advanced geological prediction scheme of karst tunnel is adjusted timely. The evaluation results can provide a reference for the construction of karst tunnels, and can also be used as a basis for the preliminary tunnel waterproof and drainage design to prevent the threat of groundwater diseases during the operation period of the karst tunnel caused by improper waterproof and drainage design. Relying on a karst tunnel under construction in the southwest slope area as an example, according to the evaluation model, the karst stratum that the tunnel passes through is “Moderately severe”, when the tunnel passes through the stratum, there is a high possibility of encountering a underground river or karst cave. The rationality and accuracy of this method are verified by tunnel construction.