土压盾构穿越上软下硬地层洞内超前注浆加固技术

Advance Grouting Reinforcement Technology for Earth Pressure Shield Tunnelling through Upper-Soft-Lower-Hard Strata

以广州地铁18号线番南1号井—2号井上软下硬区段复合地层盾构隧道穿越密集房屋群为工程背景,结合超前注浆工艺和现场监测数据对地表建筑物沉降变形过程、加固效果进行分析。结果表明:(1)针对土压平衡辅助气压盾构模式提出的3次磷酸水玻璃混合液封孔及后退式超前注浆加固可有效控制地表建筑沉降,下穿龙美村期间建筑沉降变化保持在-8~5 mm范围之间;(2)注浆当日刀盘前方0~20 m范围地表房屋测点基本处于隆起状态,其中5~10 m范围注浆产生的隆起效果最明显,最大隆起值可达5.76 mm,平均值为1.21 mm;(3)注浆段刀盘通过前后的隆起与沉降趋势比较相似,受到多个注浆循环的影响,沉降槽出现向注浆搭接位置交会的趋势;(4)注浆结束标准可按定量和定压相结合方式,压力宜控制在0.3~0.5 MPa,单个循环注浆最长可达18 m,两个循环间搭接长度为3 m,掘进8~10 m,平均每循环约可完成6环,注浆加固效果良好。

This paper is based on the case of the composite stratum shield passing through a dense housing complex on the upper-soft-lower-hard section of No. 1-2 shafts of Guangzhou Metro Line 18, to analyze the process of settlement and deformation of the buildings on the ground surface and the effect of reinforcement by combining the data of advance grouting process and field monitoring. The results show that:(1) The three times of mixed sealing with phosphate and sodium silicate and backward advance grouting reinforcement proposed in this paper for earth pressure shield and auxiliary air pressure mode can effectively control the settlement of buildings on the surface. Specifically,the changes in the settlement of the buildings when the shield was passing under Longmei Village were kept between the range of-8~5 mm;(2) On the day of grouting, the measurement points of the buildings on the surface within the perimeter of 0-20 meters in front of the cutter head were basically in an upheaving state, of which the upheaving effect produced by grouting within the perimeter of 5-10 meters was the most significant with the maximum upheaving value up to 5.76 mm and the average upheaving value of 1.21 mm;(3) The tendency of upheaving and settlement in the grouting section before and after the cutter head passed was quite similar, and the settlement groove showed the tendency of intersection in the slurry lap position under the influence of multiple grouting cycles;and(4)The standard to end the grouting can be considered by combining the quantitative and fixed pressure. Specifically,the grouting reinforcement effect would be the best if the pressure is controlled at 0.3~0.5 MPa, the longest single cycle of grouting can reach 18 meters, the lap length between two cycles is 3 meters, the excavation is 8~10 meters,and each cycle can complete about 6 rings on average.