低渗透性地层隧道超前加固改进研究

Preceding Reinforcing Improvement Research on the Tunnel with Low Permeability Stratum

研究目的:武汉地铁二号线施工过程中穿越渗透性较差的黏土或黏土夹碎石地层时,应用常规的"超前注浆小导管"加固技术,存在加固效果不明显和施工难度大的问题。为了解决这一问题,采用型钢支护代替超前锚杆或钢管进行超前支护,并通过应用离散元法对比矩形和圆形断面型钢的成拱效果,建议采用矩形断面型钢,为类似工程积累经验。研究结论:通过研究得出:(1)对于相同宽度和间距的矩形和圆形断面型钢而言,矩形型钢具有更好的成拱效果,能承受更高的土体荷载;(2)从抗弯性能和价格上来说,矩形截面型钢都优于圆形钢管;(3)在地层渗透系数较小、注浆效果较差的情况下,可以用矩形断面型钢来代替超前注浆小导管进行超前支护;(4)该研究成果可应用于隧道超前支护的设计。

Research purposes： When Wuhan metro line 2 went through poor permeability of clay or clay gravel stratum, as a conventional construction method, ＂ small duct grouting in advance＂ in tunnel arch was difficult to construct, and its advanced reinforcement effect was not obvious. In order to solve this problem, this paper put forward a scheme that the application of steel instead of leading anchor rod or steel tube. By comparing arching effect between rectangular cross -section steel and circular cross -section steel, this paper suggested to adopt the rectangular cross section steel. The results show that the rectangular cross -section steel could improve strengthening effect. And it can accumulate the experience to similar projects. Research conclusions： According to the research, it can be drawn： （ 1 ） For the same width and spacing of the rectangular and circular cross section steel, rectangular steel has better the arching effect, and it can bear higher soil load ; （2） In terms of the bending capacity and price, rectangular section steel is better than that of circular steel tube ; （ 3 ） In the small percolation coefficient strata, grouting effect is poor, rectangular steel can be used in place of the small duct grouting in advance for supporting in advance ; （ 4 ） The research results can be applied in the tunnel advanced support design.