Abstract:The problem of fast and accurate calibration of mesoscale parameters in the lower degraded area and the upper nondegraded area of fractured tower column unstable rock in the process of dynamic calculation of instability of fractured tower column with high slope using particle flow code (PFC) discrete element method is discussed. Taking the parallel bond constitutive model as the contact model of particle flow, a threedimensional discrete element uniaxial compression test based on orthogonal design was constructed. Combined with the laboratory test of Maokou Formation limestone in the secondorder cliffs of the Zengziyan rock, Nanchuan District, Chongqing Municipality, the grey correlation degree, multifactor variance and regression analysis were mutually verified. The quantitative expressions between six main mesoscopic parameters and three macroscopic parameters of limestone are obtained. The elastic modulus of limestone increased linearly with the contact modulus of particles, and poisson’s ratio and the particle stiffness ratio increased logarithmically. The uniaxial compressive strength increases linearly with tangential bond strength, and there are multiple function expressions between macro and meso parameters. Furthermore, the multivariate function expressions between macroscopic and microscopic parameters of limestone materials are constructed. According to this, the calibration process of mesoscale parameters of limestone materials is proposed. The numerical simulation results are consistent with the experimental results in terms of failure mode and stressstrain curve. This method can be used for rapid calibration of the mesoscopic parameters of this limestone, reducing the blind complexity of “trial and error method” in the mesoscopic parameter calibration process, and providing important support for the numerical deduction of PFC for the instability and disintegration of this type of fractured rock.