Research on the Optimization of Reasonable Staggered Distance under Different Middle Rock Thicknesses in the Blasting Construction of Small Interval Distance Tunnels
Small interval distance tunnel is a common tunnel structure form.Due to the small interval distance between the left and right tunnels,mutual disturbance during the construction period can easily cause damage to the middle rock,so it is crucial to choose a reasonable excavation stagger distance between the left and right tunnels.Taking the small interval distance section of a highway tunnel as the engineering background,the FLAC3D software is utilized to simulate tunnel excavation with different excavation distance for varying middle rock thicknesses.The investigation analyzes the variations in blasting-induced vibration velocity,arch roof settlement,clearance convergence,and arch roof stress on the detonation side.Concurrently,the study combines field monitoring data to validate the reliability of the identified optimal misalignment.The findings reveal that:1)During tunnel blasting excavation,the influence range of significant variations in arch roof settlement and clearance convergence is roughly identical,whereas the impact on arch roof stress is relatively smaller.2)The rational distances for blasting construction are determined as 5B,4B,3B,2B,and 2B,respectively,for middle rock thicknesses of 0.5B,0.75B,1B,1.5B,and 2B.3)The field monitoring results generally coincide with the numerical simulations,validating the reliability of the proposed optimal construction distances and providing valuable reference for similar engineering projects.
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