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Analysis of the Results of General Dewatering and Drainage Measures and Ground Stability of Tunnel in Water-rich Hypabyssal Rock
(1. YCIC Yunling Construction Co., Ltd., Kunming 650041; 2. Department of Geotechnical Engineering, College of Civil Engineering,Tongji University, Shanghai 200092; 3. Key Laboratory of Geotechnical and Underground Engineering of the Ministry of Education,Tongji University, Shanghai 200092)
Abstract In order to investigate the results of the general dewatering and drainage measures for a tunnel in waterrich hypabyssal rock stratum and how these measures will affect the tunnel stability, the Wangjiazhai Tunnel of Lincang-Qingshuihe Expressway is used as an example in this study. By using the extracted water quantity on site and the stratum water level monitoring data, the finite element model for dewatering and drainage of tunnel in water-rich hypabyssal rock stratum is created, so as to calculate and analyze how the general dewatering and drainage measures will affect the distribution of pore water pressure/moisture content. Given the shear corrected strength of the soil masses with different moisture contents, the sequential coupling method is used to analyze the tunnel stability after dewatering and drainage. As the results indicate: the general dewatering and drainage measures will effectively reduce the moisture content of the tunnel face and increase the strength of soil mass. After dewatering, the deformation on site is reduced by 80% maximally. The stratum water pressure decreases linearly as the extracted water quantity increases, the moisture content decreases in inverse proportion, and a dewatering funnel is formed between the left and right deep wells. The deep wells play the main role in dewatering. When the average water discharge of single well reaches 400 m3/d, the unsaturation state appears in the grouting circle. After the general dewatering and drainage measures are implemented at the site of Wangjiazhai Tunnel, the strength of hypabyssal rock increases, and the safety factors of the left and right tunnels are 1.99 and 1.62.
Abstract：
In order to investigate the results of the general dewatering and drainage measures for a tunnel in waterrich hypabyssal rock stratum and how these measures will affect the tunnel stability, the Wangjiazhai Tunnel of Lincang-Qingshuihe Expressway is used as an example in this study. By using the extracted water quantity on site and the stratum water level monitoring data, the finite element model for dewatering and drainage of tunnel in water-rich hypabyssal rock stratum is created, so as to calculate and analyze how the general dewatering and drainage measures will affect the distribution of pore water pressure/moisture content. Given the shear corrected strength of the soil masses with different moisture contents, the sequential coupling method is used to analyze the tunnel stability after dewatering and drainage. As the results indicate: the general dewatering and drainage measures will effectively reduce the moisture content of the tunnel face and increase the strength of soil mass. After dewatering, the deformation on site is reduced by 80% maximally. The stratum water pressure decreases linearly as the extracted water quantity increases, the moisture content decreases in inverse proportion, and a dewatering funnel is formed between the left and right deep wells. The deep wells play the main role in dewatering. When the average water discharge of single well reaches 400 m3/d, the unsaturation state appears in the grouting circle. After the general dewatering and drainage measures are implemented at the site of Wangjiazhai Tunnel, the strength of hypabyssal rock increases, and the safety factors of the left and right tunnels are 1.99 and 1.62.
DUAN Xianbiao1 HUANG Xuanbo2,
3 ZHANG Qingzhao2,
3 XU Yongjin1
.Analysis of the Results of General Dewatering and Drainage Measures and Ground Stability of Tunnel in Water-rich Hypabyssal Rock[J] MODERN TUNNELLING TECHNOLOGY, 2024,V61(1): 146-155
2024, Vol. 61 