新建隧道下穿施工对既有高速公路的影响及工法优化研究

为了探索新建隧道下穿施工对既有高速公路的影响,并为新建隧道选取更适合的施工方法,以某新建浅埋暗挖隧道为例,借助于NASYA和FLAC 3D,对其进行了数值模拟研究。研究成果表明:首先,由于覆土越大,对隧道支护的压力越大,新建隧道引起的土体的沉降值便越大,表现为路基下方围岩的沉降大于路肩下方的;第二,由于临时支撑能对土体的变形起到削弱作用,所以采取了更多临时支护的CRD法施工引起的道路沉降值明显小于台阶法施工引起的沉降值;第三,本工程中将三台阶施工方法替换为CRD法后,既有路面最大沉降值从14.7 mm减小为12.9mm,降低值为1.8 mm,但台阶法具有工期短、成本低等优点,故推荐本工程采用台阶法施工。

Influences of New Tunnel Underpass Construction on Existing Expressway and Study on Construction Method Optimization

In order to explore the impact of new tunnel underpass construction on existing expressways and select a more suitable construction method for new tunnel,this paper takes a new shallow tunnel as an example,and carries out numerical simulation research with the help of NASYA and FLAC 3D.The research results show that:firstly,the greater the overburden,the greater the pressure on the tunnel support,the greater the settlement value of the soil caused by the new tunnel,which shows that the settlement of the surrounding rock under the roadbed is larger than that under the shoulder.Secondly,because temporary support can play a weak role in soil deformation,the road settlement caused by CRD construction with more temporary support is obviously smaller than that caused by step construction.Thirdly,after replacing the three-step construction method with CRD method in this project,the maximum settlement of existing pavement is reduced from 14.7 mm to 12.9 mm and the reduction value is 1.8 mm,but the step method has the advantages of short construction period and low cost,so it is recommended to use the step method in this project.