Abstract
Karst geology is common in China, and buried karst formations are widely distributed in Guangdong province. In the process of shield tunneling, the abundant water resources present in karst caverns could lead to the potential for high water ingress, and a subsequent in situ stress change-induced stratum collapse. The development and distribution of karst caverns should therefore be identified and investigated prior to shield tunnel construction. Grouting is an efficient measure to stabilize karst caverns. The total volume of karst caverns along the shield tunneling alignment, and its relationship with the required volume of grouts, should be evaluated in the preliminary design phase. Conventionally, the total volume of karst caverns is empirically estimated based on limited geological drilling hole data; however, accurate results are rarely obtained. This study investigates the hydrogeology and engineering geology of Guangzhou, the capital of Guangdong province, and determines the fractal characteristics of the karst caverns along the tunnel section of Guangzhou metro line no. 9. The karst grouting coefficients (VR) were found to vary from 0.11 in the case of inadequate drilling holes to 1.1 in the case where adequate drilling holes are provided. A grouting design guideline was furthermore developed in this study for future projects in karst areas.
Highlights
IntroductionShield tunneling has been extensively used in the construction of underground infrastructures under various geological conditions with a high groundwater level and gassy conditions [1,2,3,4,5,6]
Shield tunneling has been extensively used in the construction of underground infrastructures under various geological conditions with a high groundwater level and gassy conditions [1,2,3,4,5,6].In China, there are a total of 41 cities including Beijing, Shanghai, Guangzhou, and Shenzhen with metro tunnels currently in operation or under construction
In spite of several studies on shield tunneling in karst geology, many problems are still encountered which impact the construction of metros
Summary
Shield tunneling has been extensively used in the construction of underground infrastructures under various geological conditions with a high groundwater level and gassy conditions [1,2,3,4,5,6]. In China, there are a total of 41 cities including Beijing, Shanghai, Guangzhou, and Shenzhen with metro tunnels currently in operation or under construction. In spite of several studies on shield tunneling in karst geology, many problems are still encountered which impact the construction of metros. The treatment of karst caverns remains one of the most challenging engineering construction problems in shield tunneling projects. Sectional view ofofthe the geological drilling holes
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