Cumulative damage effect and support optimization of tunnel anchored surrounding rock under coupled dynamic-static loads
Periodic excavation blasting causes the gradual accumulation of damage to the anchored sur-rounding rock of the tunnel,and its plastic zone expands or even becomes unstable,seriously threaten-ing the subsequent safe construction and operation of the tunnel.By establishing a stress model for the anchored surrounding rock unit under coupled dynamic-static loads,based on the principle of coordina-ted deformation between anchor bolts and rocks and the attenuation law of blasting main frequency,the damage deformation mechanism of the anchored surrounding rock under static loads such as in-situ stress,pore water pressure,anchor bolt support force,and dynamic loads of excavation blasting was studied.The calculation formulas for the plastic zone and broken zone radius of the anchored surround-ing rock after the cumulative damage under coupled dynamic-static loads were derived,and the evolu-tion law of deformation range of anchored surrounding rock under different factors was analyzed.The re-sults show that:The deformation range of tunnel anchored surrounding rock under coupled dynamic-static loads gradually increases with the increase of pore water pressure,blasting impact force,number of surrounding blast holes,and damage variables,and decreases with the increase of geological strength indicators;The range of disturbance damage area for the anchored surrounding rock of K85.0～K195.7 section of shangnan tunnel 4#of the west east gas pipeline is 8 m,with the radii of plastic zone and bro-ken zone are 5.08 m and 3.74 m,respectively;After the implementation of the optimized support scheme,the subsidence of the tunnel roof has decreased by 58%,and the relative displacement of the sidewalls has decreased by 60%.The deformation control effect of the surrounding rock is good.The re-search provides reliable guarantees for the safe and efficient construction of the tunnel.
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