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Deformation Monitoring and Analysis during the Excavation of Deep Circular Shafts in Intercity Railway Tunnels
（1. Shenzhen Metro Group Co.,Ltd., Shenzhen 518000; 2. School of Aeronautics and Astronautics, Sun Yat-Sen University,Shenzhen 518107; 3. School of Civil Engineering, Sun Yat-sen University, Zhuhai 519082; 4. Southern Marine Science Engineering Guangdon Laboratory, Zhuhai 519082; 5. The Third Engineering Co.Ltd of China Railway Seventh Group, Xi′an 710032）
Abstract The selection and design of the support system for the launching and receiving shafts of shield tunnelling are critical issues in the construction of deep-buried tunnels. Circular enclosure structures can fully utilize the arch effect of soil and do not require internal supports, providing better mechanical performance and cost-effectiveness compared to general polygonal structures. To reduce the construction difficulty and improve efficiency in the rockembedded section of composite strata, the Shenzhen International Airport-Dayawan intercity railway tunnel′s Pingju shield working shaft adopts an upper circular diaphragm wall combined with a ring beam and a lower layer of rock support using shotcrete and anchor bolts. This study analyzes changes in external groundwater, ground surface, and enclosure structure deformation during the excavation of the deep circular foundation pit. The results indicate that: surface overload and uneven external groundwater levels cause differential deformation of the wall and ground surface; the maximum horizontal deformation of the wall is generally within 0 to 0.05%H (H is the excavation depth);most ground surface settlement deformation is within 0 to 0.08%H; the vertical settlement at the top of the wall mostly ranges from 0 to 0.25%H; compared to general irregular polygonal foundation pits, the cylindrical support system shows better stability and deformation performance; the combined use of diaphragm walls with ring beams in the upper section and shotcrete and anchor bolts in the lower rock layer ensures the stability and safety of the foundation pit in composite strata.
Abstract：
The selection and design of the support system for the launching and receiving shafts of shield tunnelling are critical issues in the construction of deep-buried tunnels. Circular enclosure structures can fully utilize the arch effect of soil and do not require internal supports, providing better mechanical performance and cost-effectiveness compared to general polygonal structures. To reduce the construction difficulty and improve efficiency in the rockembedded section of composite strata, the Shenzhen International Airport-Dayawan intercity railway tunnel′s Pingju shield working shaft adopts an upper circular diaphragm wall combined with a ring beam and a lower layer of rock support using shotcrete and anchor bolts. This study analyzes changes in external groundwater, ground surface, and enclosure structure deformation during the excavation of the deep circular foundation pit. The results indicate that: surface overload and uneven external groundwater levels cause differential deformation of the wall and ground surface; the maximum horizontal deformation of the wall is generally within 0 to 0.05%H (H is the excavation depth);most ground surface settlement deformation is within 0 to 0.08%H; the vertical settlement at the top of the wall mostly ranges from 0 to 0.25%H; compared to general irregular polygonal foundation pits, the cylindrical support system shows better stability and deformation performance; the combined use of diaphragm walls with ring beams in the upper section and shotcrete and anchor bolts in the lower rock layer ensures the stability and safety of the foundation pit in composite strata.
SONG Yuepeng1 FAN Xiaofeng2 LIANG Yu2,
3,
4 PENG Hongguo5 ZHANG Hanwei5
.Deformation Monitoring and Analysis during the Excavation of Deep Circular Shafts in Intercity Railway Tunnels[J] MODERN TUNNELLING TECHNOLOGY, 2024,V61(5): 219-226
2024, Vol. 61 