不同深度冲击钻桩基施工时隧道衬砌的动力响应研究

Dynamic Response of Tunnel Linings at Pile Foundation Construction Usinga Percussion Drill with Different Depths

高速铁路隧道穿越软弱地层时,常采用冲击钻打孔的桩基加固隧底地层,冲击钻施工时会对隧道衬砌产生动力影响。文章依托贵南高铁德庆隧道,采用FLAC 3D数值模拟研究冲击钻施工至隧底下不同深度(15 m,20 m,25 m和29 m)时衬砌的动力响应。结果表明:不同振源深度下,隧道衬砌位移、最大主应力及速度响应差别不大。应力最大处位于距振中约20 m的左、右边墙处;对于隧道衬砌的速度响应,其最大发生在冲击钻施工开始时,此时出现显著峰值,随后衬砌速度值逐渐稳定;冲击钻施工时位移分布存在较明显的范围,其分布由振中向隧道两端逐渐减小,由拱底至边墙至拱顶逐渐减小。但位移量较大,最大可达4.95 cm,属大变形,因此应及时做好支护,避免隧道发生塌方。

The construction of pile foundations by percussion drills is generally carried out for reforcing tunnel base ground in high-speed railway tunnels passing weak strata.However,the process can influence tunnel linings dynamically.Based on the Deqing tunnel on the Guinan high-speed railway,a series of numerical simulations are performed to acquire the dynamic response of the linings when the percussion drilling is at different depths(15 m,20 m,25 m,and 29 m)under the tunnel base.The results show that the displacement,maximum principal stress,and velocity response of the linings vary slightly at the specified depths.The maximum stress is at the left and right walls about 20 m away from the epicenter.The peak velocity,occurring at the commencement of the excitation,is detected at the tunnel bottom,and then its value gradually trends to stabilization.The displacement progressively declines from the epicenter to both the tunnel ends,and from the tunnel bottom to the sidewalls to the crown;the maximum displacement can reach a range of large deformation of 4.95 cm,thus reinforced supports are required to avoid tunnel collapses.