连拱隧道施工对洞口仰坡影响的三维数值分析

以江西某高速公路一浅埋偏压连拱隧道为例,采用Marc有限元程序对其出口段进行了动态施工的三维数值模拟.从施工过程中的应力集中、塑性区的分布形态和发展规律、仰坡轴向地表位移的分布特征等方面,系统研究了偏压连拱隧道施工对强风化岩体洞口仰坡的影响作用机制.结果表明:在模拟施工过程中塑性区和应力集中区只出现在洞体附近,可能的仰坡失稳往往是隧道施工失稳的累进性响应;洞口仰坡的轴向水平位移前缘大、后缘小,垂直位移后缘大、前缘小;隧道上方和近山脊一侧仰坡位移比近山谷一侧大,仰坡失稳往往从隧道上方和埋深较大一侧开始.

3D numerical simulation of construction effect on entrance slop of double-arch tunnel

Taking an expressway tunnel in Jiangxi Province as engineering example,this article simulates the construction effect on entrance slope of a shallow-embedded and double-arched tunnel with partial pressure using Marc method.From several aspects,such as stress concentration,plastic zone distribution and development,ground displacement along the main slope axis,the effect mechanism of construction on the entrance slope composed of highly weathered rock is studied systematically and it is found that stress concentration area and plastic zone only distribute near the tunnel lining all along,and the entrance slope failure is gradual and accumulated response to the tunnel failure during construction.For the slope at the tunnel entrance,the displacement mode is similar or identical to that of the slope with circular shear sliding surface: axial horizontal displacement of front-edge is bigger than that of the back,for vertical displacement,it is just opposite.Displacement above tunnel and on the ridge side is more prominent than the valley side,so the part above tunnel and with large buried-depth may fail firstly.