软土地区地铁盾构施工端头土体加固要求探讨

 软土地区土压平衡盾构施工中，端头土体加固要求目前基本上都是参照日本经验,设计为始发端头6m、到达端头3.5m，加固土体强度0.8~1.5MPa。根据现场施工经验总结，基于一般的土体加固强度均会大于1.5MPa，提出了一般情况下始发端头和到达端头的合理加固长度为3.5m，针对砂性地层的特殊情况提出了端头加固的形式；同时根据加固土体的防水目的和目前现场施工实际所使用的方法,建议更改现有的加固土体防水要求。

Discussions on Criteria for Soil Reinforcement during EPB Shields&rsquo|Launching &|Arrival Construction in Soft Ground

The present criteria for the soil reinforcement during EPB shields’ launching and arrival construction in soft ground adopted in China are mainly based on Japanese experience, i.e., the length of the soil reinforcement for the shield launching is 6m, the length of the soil reinforcement for the shield arrival is 3.5m and the strength of the soil reinforcement ranges from 0.8MPa to 1.5MPa. Due to the fact that the normal strength of the reinforced soil is higher than 1.5MPa, the authors, based on the construction experience in the job site, suggest that the reasonable length of the soil reinforcement for the launching and arrival of shield machines under normal conditions should be 3.5m. On basis of the special features of sand ground, the authors recommend the reinforcement patterning for shield arrivals in sand ground. Furthermore, the authors, on basis of the water proofing purpose of the reinforced soil and the construction methods adopted in the job site, suggest that the existing soil reinforcement criteria should be modified.