白垩系粉砂岩隧道下穿既有公路沉降特性研究

Research on Settlement Characteristics of Cretaceous Siltstone Tunnel Underpassing Existing Highway

为研究粉砂岩地层铁路隧道下穿既有公路施工沉降规律,基于杭州-绍兴-台州铁路隧道下穿新蟠线公路施工参数和现场实测数据,结合数值分析方法对比两台阶法、三台阶法、CD法施工对地表沉降的影响,对沉降曲线进行分析。研究结果表明:分部开挖可减少地表沉降值,CD法可有效控制地表沉降量;掌子面通过交叉点正下方时,地表沉降值急剧增大,后趋于稳定,沉降主要发生在距掌子面1倍隧道洞径范围内;隧道施工引起的地表沉降曲线为V形,沿隧道中线对称分布,沉降槽宽度约为2倍隧道洞径;经计算两台阶法施工也可满足地表沉降要求,为加快施工进度,建议采用两台阶法。在类似地质条件下,此工程施工参数和方法可为同类工程提供参考。

In order to study the settlement law of railway tunnel under-passing existing highway in siltstone stratum,the settlement curve is analyzed based on the construction parameters and field measured data of Hangzhou-Shaoxing-Taizhou HSR tunnel under-passing Xinpan Line,in combination with numerical analysis method to compare the influence of two-bench cut method,three-bench cut method and CD method on surface settlement.The results show that partial excavation can reduce the surface settlement value,and CD method can effectively control the surface settlement;when the tunnel face passes directly below the intersection,the surface settlement value increases sharply and then tends to be stable.The settlement mainly occurs within 1time of the tunnel diameter from the tunnel face;the surface settlement curve caused by tunnel construction is Vshaped and symmetrically distributed along the center line of the tunnel.The width of the settlement tank is about 2 times the tunnel diameter;after calculation,the two-bench cut method can also meet the requirements of surface settlement.In order to speed up the construction progress,it is recommended to adopt the two-bench cut method.Under similar geological conditions,the construction parameters and methods of this project can provide reference for similar projects.