大断面黄土隧道变形规律及预留变形量研究

Study on the Deformation Regularity and Preset Deformations for Large Section Tunnels in Loess

文章统计分析了大断面黄土隧道初期支护变形量,研究了大断面黄土隧道变形规律及预留变形量合理取值范围。大断面黄土隧道变形规律表现为:隧道拱顶、拱脚下沉差异小,隧道开挖后拱部将产生一定程度的整体下沉;隧道拱顶下沉量均大于水平收敛;初期支护封闭后,隧道周边位移基本上不再发展;当隧道埋深小于40m时,隧道变形量较大且规律不明显;当隧道埋深大于40m时,隧道变形量分布相对集中。经过对现场量测数据的统计分析可知:在Ⅳ级围岩条件下,大断面黄土隧道预留变形量可取10～15cm;在Ⅴ级围岩条件下,大断面黄土隧道预留变形量可取25～28cm。

Primary support deformations of large section tunnels in loess were analyzed statistically, their deformation regularity and the reasonable selection ranges of preset deformations for them were studied. The deformation regularity of large section tunnels in loess is manifested that the settlement difference between the arch crown and spring line is small, the total subsidence of the tunnel crown will occur in a certain extent after tunnel excavation; the subsidence of the arch crown is always larger than the horizontal convergence; the displacement around the tunnel will not increase again after the primary lining closed into a whole section; when the overburden of tunnel is less than 40 m, the tunnel deformations are larger and the regularity is not obvious, and when the overburden of tunnel is larger than 40m, the distribution of tunnel deformations is relatively concentrated. Based on the statistical analysis of in-situ measurement data, the recommended preset deformation range of the large section tunnels in loess for grade IV surrounding rocks is 10cm to 15cm, and 25cm to 28cm for grade V surrounding rocks.