湿陷性黄土隧道洞口地基处理方法

Treatment method of foundation at tunnel portal section in collapsible loess stratum

为了消除黄土隧道内黄土地基层的湿陷性,提高挤密系数使其达到相关规范要求,并且在小空间中降低施工振动,对宝鸡至兰州客运专线兰州境内范家窝隧道进口段的2种地基处理挤密桩在7种桩间距下进行了现场和室内试验。结果显示：采用潜孔钻机和自制改装夯实机械进行地基处理时,地基土及衬砌的振动均处于可控范围内;水泥土挤密桩和水泥碎石土挤密桩的桩体基本均匀;水泥土挤密桩桩间距≤65 cm时,桩间土体平均湿陷系数在0.002～0.007,挤密系数在0.89～0.98,平均挤密系数0.93,湿陷系数和挤密系数均满足相关规范要求;水泥碎石土挤密桩区域经处理后土体湿陷性完全消除,但由于桩间距过大,挤密系数不能满足相关规范要求。

Based on the Fanjiawo tunnel on Baoji-Lanzhou passenger dedicated railway line, to eliminate any foundation collapse, ensure that compaction coefficient lives up to the regulation concerned and mitigate construction- induced vibration in limited space. In this light, it carries out in-situ and indoor tests on two types of compaction piles at the tunnel portal with seven different intervals applied in the process. In using diving drill and self-modified rammer machinery for foundation treatment, the paper notices that the vibration of foundation soil and lining falls within a controllable range and the pile bodies for both cement-soil compaction pile and cement-gravel soil compaction pile remain evenly distributed. As the cement-soil compaction piles are arranged with a 65 m interval or less ,the average collapsibility coefficient for the soil in between stands within 0. 002 and 0. 007, the compaction coefficient-with an average of 0.93-falls between 0. 89 and 0.98 ,both of which live up to the relevant regulation. The treatment to cement-gravel soil piles have proven to be effective, as the loess collapse is removed. However the exceedingly large pile interval means that the compaction coefficient can yet meets the related requirements concerned.