Study on "three-section and four-layer" reinforcement technology of tunnel vault subsidence in the karst basement
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摘要: 为有效治理岩溶基底城市隧道拱顶地层沉陷地质灾害，在充分探明沉陷区水文地质、工程地质特征的基础上，提出了“三段四层控制技术”，将治理区划分为沉陷区重点加固段、影响区次重点加固段和超前加固段；再根据治理深度和治理顺序进一步把沉陷区重点加固段分为顶部阻浆层、拱顶止浆垫层、拱顶加固层和中间加固层，研究了每段、每层注浆加固机理、浆液类型选择和控制注浆参数。研究成果表明，采用孔内复合止浆技术满足不同深度地层分段注浆为主、垂直孔和定向斜孔相结合，充填注浆、劈裂-挤密注浆相结合，以速凝浆液为主、单液水泥浆为辅，严格控制安全注浆参数，是“三段四层控制技术”安全有效注浆的技术关键，该技术方案在岩溶基底城市隧道拱顶地层沉陷地质灾害治理方面，取得了较好的注浆加固效果，有良好的推广应用价值。Abstract:
In order to effectively control the geological disaster of tunnel vault subsidence in the karst basement, the "three-section and four-layer" control technology is proposed, based on the full analysis of engineering geology and hydrogeological characteristics of the subsidence stratum. In this technology, the treatment area is divided into the key reinforcement section, the sub-key reinforcement section of the affected area and the pre-excavated reinforcement section. According to the treatment depth and order, the key reinforcement section of the subsidence area is divided into the top slurry barrier layer, the vault cushion layer of slurry-stopping, the vault reinforcement layer and the intermediate reinforcement layer. In terms of grouting mechanism, filling grouting and splitting-compacting grouting are adopted in both the top slurry barrier layer and the intermediate reinforcement layer. The alternate mode with filling-splitting-compacting grouting is implemented in the intermediate reinforcement layer, and the filling grouting mode is adopted in the vault cushion layer of slurry-stopping. Splitting-compacting grouting is conducted in both the pre-excavated reinforcement section and the sub-key reinforcement section in the affected area. In order to reduce the leakage of grout in the top slurry barrier layer and vault cushion layer of slurry-stopping, C-GT quick setting mixed grout is selected, and the initial setting time of the grout is controlled at 30-50 seconds, while the final grouting pressure is no more than 0.5 MPa and 0.8 MPa. In order to realize the effective diffusion of slurry in the vault reinforcement layer and intermediate reinforcement layer, the initial setting time of C-GT mixed slurry is extended to 50-90 seconds, even up to 150 seconds, and the final grouting pressure is up to 0.8-1.2 MPa. To improve the slurry diffusion and overall reinforcement strength of the pre-excavated reinforcement layer and the sub-key reinforcement layer in the affected area, the alternate and continuous grouting mode of single and double cement slurry is implemented based on the high consolidation strength of single cement slurry and the quick setting characteristics of C-GT mixed slurry. The above-mentioned technology is the key to the success of grouting reinforcement. Besides, the combined grout-stopping method is used to effectively deal with the segmented grout-stopping at the place where the hole wall collapses and shrinks, and the diameter of borehole is greatly oversized. Hence, the isolated grouting at different depths of those four layers is realized. The directional inclined hole is used to effectively avoid the hidden underground pipeline, and the grouting pipe is used as the pipe roof to improve the shear resistance of stratum. Combined with grouting, this technology can effectively improve the overall strength and stability of the reinforcement stratum by tunnel vault grouting. Research results indicate that "the three-section and four-layer" treatment scheme is the basis to effectively control the subsidence of soil overlying the tunnel. The combined grout-stopping technology in the hole is the guarantee to meet the requirement of segmented grouting at different depths. The combination of vertical hole and directional inclined hole and of filling grouting and splitting-compacting grouting, taking quick setting slurry as the primary part supplemented with single cement slurry, and the strict control of safe grouting parameters are the technical keys of safe and effective grouting. The application of the above technology has achieved good grouting reinforcement effect and hence should be popularized. -
Key words:
- karst basement /
- tunnel /
- stratum subsidence /
- disaster control /
- segmented grouting
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图 1 路面沉陷及拱顶破裂沉降情况
Figure 1. Situation of pavement subsidence and the rupture and settlement of vault
图 2 地下水位差异及钻孔喷水图
Figure 2. Diagram of groundwater level differences and borehole water spray
图 3 揭露地下水的部分钻孔位置及其连通串喷深度
Figure 3. Locations of some boreholes of exposed groundwater and the depth of the interconnected spray
图 4 路面沉陷、拱顶破裂沉降的原因分析图
Figure 4. Reasons of pavement subsidence and the rupture and settlement of vault
图 5 治理区横向三段划分示意图
Figure 5. Schematic diagram of the horizontal three-section division of the treatment area
图 6 沉陷区重点加固段分层治理示意图
Figure 6. Schematic diagram of layered treatment of the key reinforcement sections in subsidence areas
图 7 影响区次重点加固段注浆加固层示意图
Figure 7. Schematic diagram of the grouting reinforcement layer in the sub-key reinforcement section in the affected area
图 8 未开挖超前加固段注浆加固层示意图
Figure 8. Schematic diagram of the grouting reinforcement layer in the pre-excavated reinforcement section
图 9 不同类型注浆钻孔间隔布置示意图
Figure 9. Schematic diagram of interval layout of different types of grouting boreholes
图 10 顶部阻浆层钻探注浆原理示意图
Figure 10. Schematic diagram of the drilling grouting principle of the top slurry barrier layer
图 11 拱部止浆垫钻探注浆原理示意图
Figure 11. Schematic diagram of the drilling grouting principle of the vault cushion layer of slurry stopping
图 12 拱顶加固层钻探注浆原理图
Figure 12. Schematic diagram of drilling and grouting of the reinforcement layer at the top of vault
图 13 中间加固层钻探注浆原理示意图
Figure 13. Schematic diagram of drilling and grouting principle of intermediate reinforcement layer
图 14 孔内复合式止浆技术原理图
Figure 14. Schematic diagram of the combined technology of slurry-stopping in the hole
图 15 YK2+683-YK2+710治理区域三段注浆量分布图
Figure 15. Distribution of grouting amount in the third section of YK2+683-YK2+710 treatment area
图 16 拱顶各监测点每日沉降数据曲线
Figure 16. Daily settlement curve of each monitoring point of the vault
图 17 YK2+693处注浆压力与拱顶沉降量关系曲线
Figure 17. Relationship between grouting pressure and vault settlement at YK2+693
图 18 YK2+693处每日注浆量与拱顶沉降量关系曲线
Figure 18. Relationship between daily grouting amount and vault settlement at YK2+693
表 1 治理段部分钻孔地下水位及互相串通情况
Table 1. Groundwater levels and the interconnection of some boreholes in the treatment section
喷水孔号 喷水深度/m 串喷孔号 串喷深度/m 喷水孔号 喷水深度/m 串喷孔号 串喷深度/m B3-2补 2.0 X4-4 7.2 X4-6 7.5 B3-1 6.3 C2-3补 6.1 C2-2 7.0 B4-1 6.1 C2-4补 6.5 C2-2补
C2-3补7.0
6.2X5-1 7.2 X3-2
X4-58.0
7.5B4-7补 6.9 B3-7 8.5 X2-4 6.3 B4-10补 6.3 B4-9补 5.0 B4-3补 6.1 B3-4 8.0 X2-3 4.5 注：B3-2补是指原设计B3-2孔遇到障碍无法施工，移位重打的钻孔编号，以下同。 
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表 2 各加固层注浆机理、浆液类型和控制注浆参数表
Table 2. Grouting mechanism, slurry type and grouting control parameters of each reinforcement layer
序号 注浆加固
层位注浆
类型浆液
类型水泥浆平均
密度/g·cm−3Vc∶Vgt 混合浆液
初凝时间/s注浆速率
/L·min−1终压
(不大于)/MPa1 顶部阻浆层 充填注浆 C-Gt混合浆液 1.5 1∶1 50~90 40 0.3 2 劈裂—挤密注浆 C-Gt混合浆液 1.6 2∶1 30~50 20 0.8 3 拱顶止浆垫层 充填注浆 C-Gt混合浆液 1.6 1∶1~2∶1 30~50 20 0.5 4 拱顶加固层 充填注浆 C-Gt混合浆液 1.5 1∶1 50~90 40 0.5 5 劈裂—挤密注浆 C-Gt混合浆液 1.5 1∶1 30-50 20 0.8~1.0 6 中间加固层 充填—劈裂—挤密 单双液交替 1.5 1∶1 90~150 20~40 1.0~1.5 7 未开挖超前加固层 劈裂—挤密 单双液交替 1.5 1∶1 50~90 20~40 1.0~1.2 8 影响区加固层 劈裂—挤密 单双液交替 1.5 1∶1 50~90 20~40 1.0~1.2 注：配浆使用普通硅酸盐水泥，水泥标号P.O 42.5R；GT浆液密度控制在1.2-1.3 g·cm−3。单液浆密度平均1.5 g·cm−3。
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表 3 沉陷区重点加固段各加固层钻孔数量、注浆量和注浆终压统计表
Table 3. Statistics of drilling quantity, grouting quantity and final grouting pressure of each reinforcement layer in the key reinforcement section of the subsidence area
钻孔种类 设计钻孔数/个 优化后钻孔数/个 注浆量/m3 注浆终压范围/MPa 顶部阻浆层(A序)/垂直孔 30 26 91.59 0.3~0.8 拱顶止浆垫层(B序)/垂直孔 30 28 42.72 0.3~0.5 拱顶加固层(C序)/定向斜孔 35 31 96.60 0.5~1.0 中间加固层(D序)/垂直孔 30 24 108.63 1.0~1.5 补强孔/垂直孔 6 6 10.06 0.8~1.0 共计 131 115 349.54
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