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Use of a 10.22   m diameter EPB shield: a case study in Beijing subway construction

View Article: PubMed Central - PubMed

ABSTRACT

Introduction: Beijing subway line 14 includes four stations and approximately 2.8 km of tunnels between the Dongfengbeiqiao and Jingshunlu areas of the city. Due to the surface and underground space limitations of this section, a double-track running tunnel instead of two single-track running tunnels was adopted to connect the two stations. The double-track tunnels were excavated by a 10.22 m diameter earth pressure balance (EPB) shield. It was the first time that an EPB shield more than 10 m in diameter was used in Beijing subway construction.

Case description: The shield, which passes underneath densely built-up areas of the city and is equipped with a spoke-type cutterhead, with balance between the ground pressure and the earth chamber pressure at the tunnel face, is of great importance. Referring to experiences gained in the EPB shield tunneling, attention was paid to the function of soil conditioning and simultaneous backfilling grouting of the shield, and some special designs were considered in manufacturing the machine.

Discussion and evaluation: In addition to the agitating rods welded to the cutterhead, two independently driven agitators were added to fully mix everything in the earth chamber. Independent pipelines were arranged for injecting different conditioning agents. Indoor tests in combination with field tests were conducted to find suitable additives and injection ratios of the additives, and determine the mix ratio of the two-component grout for simultaneous backfilling grouting. A scheme was employed for simultaneously injecting the bentonite slurry at 8% concentration and the foam liquid at 5% concentration to condition the excavated soil. The cement–sodium silicate grout was adopted to fill the tail void and the injection volume per ring was 14.1–15.3 m3.

Conclusions: The performance of the shield and evaluation of the corresponding tunneling technologies are introduced in terms of the shield tunneling induced ground surface settlements. The success of the project is of great significance to Beijing subway construction and underground space utilization. The findings serve as a useful reference for similar projects.

No MeSH data available.


Beijing subway line 14 route between Dongfengbeiqiao station and Jingshunzhan station
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Fig1: Beijing subway line 14 route between Dongfengbeiqiao station and Jingshunzhan station

Mentions: The project includes three stations (Dongfengbeiqiao station 298.7 m in length, Jiangtai station 166 m in length and Gaojiayuan station 179 m in length) and approximately 2507.9 m of double-track tunnels on Beijing subway Line 14, as shown in Fig. 1. Instead of two single-track running tunnels, one double-track running tunnel was adopted to connect two neighboring stations due to the limited surface and underground space. A 10.22 m diameter EPB shield was chosen, after overall considerations, to excavate the double track tunnels. To reduce the project duration, the construction plan employed involved completing the continued 3151.6 m long shield driving first, followed by construction of the two stations (Jiangtai and Gaojiayuan stations) by expanding the finished shield tunnel. The enlargement was realized by using a modified PBA method (Liu et al. 2015). The PBA method is a manual excavation method, which is widely used in Beijing to build subway stations.Fig. 1


Use of a 10.22   m diameter EPB shield: a case study in Beijing subway construction
Beijing subway line 14 route between Dongfengbeiqiao station and Jingshunzhan station
© Copyright Policy - OpenAccess
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC5121113&req=5

Fig1: Beijing subway line 14 route between Dongfengbeiqiao station and Jingshunzhan station
Mentions: The project includes three stations (Dongfengbeiqiao station 298.7 m in length, Jiangtai station 166 m in length and Gaojiayuan station 179 m in length) and approximately 2507.9 m of double-track tunnels on Beijing subway Line 14, as shown in Fig. 1. Instead of two single-track running tunnels, one double-track running tunnel was adopted to connect two neighboring stations due to the limited surface and underground space. A 10.22 m diameter EPB shield was chosen, after overall considerations, to excavate the double track tunnels. To reduce the project duration, the construction plan employed involved completing the continued 3151.6 m long shield driving first, followed by construction of the two stations (Jiangtai and Gaojiayuan stations) by expanding the finished shield tunnel. The enlargement was realized by using a modified PBA method (Liu et al. 2015). The PBA method is a manual excavation method, which is widely used in Beijing to build subway stations.Fig. 1

View Article: PubMed Central - PubMed

ABSTRACT

Introduction: Beijing subway line 14 includes four stations and approximately 2.8 km of tunnels between the Dongfengbeiqiao and Jingshunlu areas of the city. Due to the surface and underground space limitations of this section, a double-track running tunnel instead of two single-track running tunnels was adopted to connect the two stations. The double-track tunnels were excavated by a 10.22 m diameter earth pressure balance (EPB) shield. It was the first time that an EPB shield more than 10 m in diameter was used in Beijing subway construction.

Case description: The shield, which passes underneath densely built-up areas of the city and is equipped with a spoke-type cutterhead, with balance between the ground pressure and the earth chamber pressure at the tunnel face, is of great importance. Referring to experiences gained in the EPB shield tunneling, attention was paid to the function of soil conditioning and simultaneous backfilling grouting of the shield, and some special designs were considered in manufacturing the machine.

Discussion and evaluation: In addition to the agitating rods welded to the cutterhead, two independently driven agitators were added to fully mix everything in the earth chamber. Independent pipelines were arranged for injecting different conditioning agents. Indoor tests in combination with field tests were conducted to find suitable additives and injection ratios of the additives, and determine the mix ratio of the two-component grout for simultaneous backfilling grouting. A scheme was employed for simultaneously injecting the bentonite slurry at 8% concentration and the foam liquid at 5% concentration to condition the excavated soil. The cement–sodium silicate grout was adopted to fill the tail void and the injection volume per ring was 14.1–15.3 m3.

Conclusions: The performance of the shield and evaluation of the corresponding tunneling technologies are introduced in terms of the shield tunneling induced ground surface settlements. The success of the project is of great significance to Beijing subway construction and underground space utilization. The findings serve as a useful reference for similar projects.

No MeSH data available.