旋喷桩加固黄土隧道基底及仰拱数值模拟

Numerical simulation of jet grouting piles reinforcement in loess tunnel basement and inverted arch

应用MIDAS GTS NX软件数值模拟的方法,研究了旋喷桩群加固黄土隧道基底和仰拱效果,对有旋喷桩和无旋喷桩两种工况下,隧道基底、仰拱及拱顶变形量的差异,及旋喷桩地基加固段隧道仰拱不同施工阶段的内力和竖向变形进行分析,并与现场实测数据进行对比研究,发现采用旋喷桩加固隧道工况下时间t=22时仰拱最大隆起为5.62 cm,且沿深度方向围岩变形变化趋势平稳,变形均匀;而无旋喷桩隧道在开挖后时间t=16时仰拱最大隆起15.9 cm,且沿竖直方向围岩变形剧烈减小,变形不均匀,与现场实测结果相比变化趋势无明显变化。研究结果表明:施加旋喷桩能够提高隧道地基的承载能力和稳定性,减小地基变形量;隧底竖直旋喷桩可以改善隧道地基的土体工程力学性质,使其变形量在竖直方向随着深度的增加均匀减小,从而可以缓解隧道仰拱各部分的不均匀变形现象,防止了仰拱开裂破坏;旋喷桩受力情况与隧道围岩地应力的大小有关,高地应力区域隧道开挖后要释放的应变能越多,旋喷桩就要产生越大的轴向力来抵抗围岩的竖向变形。

The effect of jet grouting pile on tunnel foundation and inverted arch in loess area was studied by the numerical simulation of the MIDAS GTS NX.This paper analyzed the deformation differences of tunnel basement、inverted arch and top of the arch under two construction conditions as jet grouting pile and non-jet grouting pile.It analyzed the internal forces and vertical deformation of tunnel inverted arch in different construction stages,and compared with the measured data of the field.It is pointed that the maximum uplift of the inverted arch under the condition of tunnel with jet grouting pile is 5.62 cm when the excavation time t =22,while the maximum uplift of the inverted arch without jet grouting pile is 15.9 cm at the time t =16 after excavation,compared with the field measurement results,the trend did not change significantly.The results indicate that applying the jet grouting pile can increase the bearing capacity and stability of the tunnel foundation and reduce its deformation.The vertical jet grouting pile at the bottom of the tunnel can improve the soil properties of the tunnel foundation so that the deformation of the tunnel can be reduced vertically along with the increase of the depth,which can alleviate the uneven deformation of each part of the tunnel arch and prevent arch cracking damage.Stress characteristics of jet grouting pile is related to the stress of tunnel surrounding rock.The more strain energy to be released after tunnel excavation in high ground stress region,the larger axial force should be produced by jet grouting pile to resist to the vertical deformation of the rock.