小净距隧道爆破施工中不同中夹岩厚度下的合理错距优化研究

Research on the Optimization of Reasonable Staggered Distanceunder Different Middle Rock Thicknesses in the Blasting Construction of Small Interval Distance Tunnels

小净距隧道是常用的隧道结构形式,因左右洞净距较小,施工期相互扰动极易造成小净距中夹岩的破坏,选择合理的左右洞开挖错距至关重要。以某公路隧道小净距段为工程背景,采用FLAC~(3D)软件模拟不同中夹岩厚度下隧道以不同施工错距开挖,分析先行洞迎爆侧的爆破振速、拱顶沉降、净空收敛及拱顶应力的变化规律,同时结合现场监测验证所得合理错距的可靠性。研究表明:1)隧道爆破掘进时,先行洞拱顶沉降和净空收敛变化率较大的影响范围大致相同,拱顶应力则略小;2)当中夹岩厚度分别为0.5B、0.75B、1B、1.5B、2B,爆破施工的合理错距分别为5B、4B、3B、2B、2B;3)现场监测结果与数值模拟大致相同,说明通过数值计算提出的左右洞合理施工错距可靠,可为类似工程提供参考。

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 FLAC 3D 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.