低净空大直径MJS工法在盾构穿越地下通道中的应用——以珠三角城际新白广机场T1—T2区间为例

Application of Large-Diameter Metro Jet System in Shield Crossing Underground Passage with Low Clearance:A Case Study of Airport T1~T2 Section on Xintang-Baiyun Airport-Guangzhou North Railway Station of Intercity Railway in Pearl River Delta

为解决在低净空内实现大直径MJS垂直桩的施工精度与质量控制难题,针对该工法在珠三角城际轨道交通新白广机场T1—T2区间盾构下穿机场地下通道工程中的应用,开展施工技术研究。首先根据项目概况与地质条件,制定本次下穿方案与土体预加固作业安排。然后,针对本工程中的MJS施工难点,对关键控制技术进行研究。最后,分别从成桩质量、结构位移、效益评价3方面综合分析其加固效果。研究结果表明:1)通过改造吊物装置系统,可在低净空内实现加固作业,极大地提高施工适应性;2)采用特制的合金钻头与主机水准仪可实现高精度成孔,且使用高压注浆系统可实现大直径优质桩体;3)改进后的MJS工艺既保证了加固效果,又可有效规避地下障碍物及管线,其微扰动效果也确保了施工期间机场地下通道结构的正常通行。

To improve the construction accuracy and quality of large-diameter metro jet system(MJS)vertical reinforcement under a low clearance,a case study is conducted on the Airport T1~T2 Section on the Xintang-Baiyun Airport-Guangzhou North Railway Station of Intercity Railway in Pearl River Delta,and construction technologies are introduced.First,according to the project overview and geological conditions,the under-crossing scheme and the soil pre-reinforcement arrangement are determined.Then,the construction challenges and essential construction control technologies are studied specifically.Finally,the reinforcement effect is comprehensively examined from three aspects:pile-forming quality,structural displacement,and benefits evaluation.The research results show the following:(1)By transforming the lifting device system,the reinforcement construction can be realized under low clearance,thus greatly improves the construction adaptability.(2)The specially-designed alloy drill head and the level can realize pore-forming with high precision,and the high-pressure grouting system can realize the high-quality pile with large diameter.(3)The improved MJS process not only ensures the reinforcement effect,but also effectively avoids underground obstacles and pipelines, and its micro-disturbance effect also ensures the normal operation of the underground passage duringconstruction.