Anchoring Parameters Optimization of Tunnel Surrounding Rock Based on Particle Swarm Optimization

In the highway tunnel project, due to the uncertainty and complexity of geotechnical parameters, it is difficult to design and optimize the anchorage parameters. In order to solve this problem, based on the Zhenfengling tunnel project as the research object, 3D tunnel model was established by ANSYS software, the model was imported into FLAC^3D software for numerical analysis and calculation for the displacement and stress of surrounding rock during construction, using orthogonal experiment methods to analyze factors affecting the stability of surrounding rock. The influence of anchor length, anchor spacing, anchor diameter, the thickness and elastic modulus of spray layer on the displacement of arch waist, arch crown and arch bottom of the tunnel was obtained by using range and variance analysis. The regression model of the relationship between arch surrounding rock displacements and anchorage parameters was determined by fitting regression. The particle swarm optimization algorithm was used to optimize the anchorage parameters in combination with the tunnel section cost formula, and the parameters were compared with those not optimized. Finally, the anchor length is designed as 3 m, the anchor spacing is designed as 1.4 m, the anchor diameter is designed as 21 mm, the thickness of spray layer is designed as 24 cm, and the elastic modulus of spray layer is designed as 24 GPa. The stability requirements can be met, and the economic efficiency is also greatly improved. The cost of support with optimized parameters is 19.4% lower than that of the original design parameters.