砂卵石地层超前管棚和深孔注浆复合预支护效果研究

Combined pre-support with advanced piping and deep-hole grouting in sandy cobble stratum

以北京地铁12号线区间下穿京张高铁盾构隧道为工程背景,数值模拟了砂卵石地层超前管棚和深孔注浆复合预支护工法的地层变形控制效果,探讨了预支护方法对下穿工程地层变形规律、地表沉降规律、盾构管片变形规律、塑性区分布以及管棚受力特征的影响。结果表明:下穿工程地铁施工引起上部高铁盾构管片最大变形区在双区间中心截面±15m范围内,这是布置超前支护以控制地层变形的关键区;深孔注浆加固条件下增设超前管棚,可减小拱顶围岩塑性区开展范围,改善注浆体受力状态,有效降低隧道中上部围岩变形;超前管棚和深孔注浆复合预支护可充分利用深孔注浆的拱效应,又可利用管棚的梁效应,发挥各自力学优势,联合承担上部围岩压力。

Taking the shield tunnel in the subway section with minimum spacing of Beijing metro line 12 under passing the Beijing Zhangjiakou high-speed rail as an engineering case study,the deformation control effect of advanced piping and deep-hole grouting combined pre-support method in sandy gravel stratum is numerically simulated.The effect of presupport method on the deformation pattern of stratum,surface subsidence patterns,deformation patterns of shield segment,distribution of plastic zone and stress characteristics of piping of under passing works are discussed.The results are shown that the maximum deformation zone of the upper highspeed rail shield segment caused by the construction of the subway in the lower section is within positive and negative 15 meters in the central profile of the double sections,which is the key area for laying out advanced support to control the stratum deformation.The deformation of the surrounding rock in the middle and upper part of the tunnel is reduced.The combined pre-support of advanced piping and deephole grouting makes full use of the arch effect of deep-hole grouting,and also makes use of the beam effect of piping to exert their respective mechanical advantages and jointly bear the pressure of the surrounding rock in the upper part.