隧道下穿松散地层高填方路堤施工技术研究

Study on the Construction Technology of High Fill Embankment under the Tunnel

隧道下穿既有高填土路堤施工中,隧道开挖极易造成高填方路堤层失稳,诱发填方路堤发生变形产生裂缝,甚至直接影响高速公路交通安全。文章以成都一贵阳铁路大方隧道下穿杭瑞高速公路为研究背景,考虑下穿工程区松散地质条件及上覆高填方路堤易失稳变形等问题,并结合工程实际,对路堤坡脚及边坡加固技术、洞口施工技术和下穿高速公路施工等关键技术进行了系统研究。首先依次从注浆方式、注浆材料和注浆顺序三方面对坡脚与路堤注浆方案进行了分析;其次结合P-Q-T曲线、注水试验和钻孔取芯试验三种手段对注浆效果进行了相互验证;然后详细介绍了洞口施工关键技术和下穿高速公路施工关键技术;最后根据现场监测数据进行了验证。结果表明,通过注浆加固技术,高填土路基层沉降有效地控制在5～20 mm范围,满足设计文件要求。施工结束后,高填方路基层未产生明显开裂,说明该高填方路堤施工技术对控制路堤变形具有显著成效,可为今后类似施工提供参考。

As for a tunnel passing beneath the existing high fill embankment,the construction of tunnel is likely to cause the deformation,cracking and instability of the filled embankment,even directly affecting the highway traffic safety.Taking the Dafang tunnel on Chengdu-Guiyang railway,which passes beneath the Hangrui expressway,as an example,and considering the loose ground condition and the instability of overlying high filling embankment,the key technologies of embankment and slope reinforcement,tunnel portal construction and construction of tunnel beneath freeway were systematically studied.Firstly,the grouting mode,grouting material and grouting sequence were analyzed.Secondly,the grouting effect was verified by three methods:P-Q-T curve,water injection test and core test.And then the key technologies of portal construction and tunnel construction beneath the highway were introduced in detail.Finally,the construction effect was verified by the field monitoring data.It shows that the settlement deformation of high filled road base is effectively controlled at 5~20 mm through grouting reinforcement technology,with no obvious cracks.The proposed tunnel construction technology can provide reference for similar project construction in the future.