Abstract The complex geological conditions such as high water pressure and overlying silt layer are the key factors that affect the seepage characteristics and the waterproofing and drainage design of subsea tunnels. In order to systematically investigate the ambient water pressure distribution pattern and water inflow characteristics of subsea tunnel, the analytical solution for seepage field of subsea tunnel that takes into account overlying silt layer has been deduced by using the hydromechanical theories, and the corresponding numerical model has been created. Through comparison and analysis of the theoretical results, the suitability and accuracy of the numerical model have been verified. Through numerical simulation, the optimum limited drainage scheme and rational depressurization value for subsea tunnel have been obtained, the laws by which the factors such as silt layer thickness and coverage rate will affect the tunnel water inflow and the water pressure distribution pattern behind the lining have been further investigated, and the mechanism of action of overlying silt layer on the seepage characteristics of subsea tunnel have been revealed. As the results indicate: (1) As the depressurization value increases, the water drainage of tunnel decreases linearly, while the water pressure behind the lining increases linearly. With the same depressurization value,as the spacing between the circumferential French drain pipes increases, the water drainage of tunnel gradually decreases, while the water pressure behind the lining gradually increases. (2) When the silt layer thickness is 12 m,the optimum limited drainage scheme for mined subsea tunnel is as follows: for semi-closed waterproofing method,the waterproofing system is "circumferential French drain pipe + longitudinal circumferential French drain pipe with 6 m spacing", and the depressurization value is 400 kPa. (3) Increase of the silt layer thickness and coverage rate will decrease the water drainage and, to certain extent, decrease the water pressure behind the lining. At the junction between weakly weathered granite and silt overburden, the water pressure behind the lining changes abruptly,so priority should be given to optimizing the water drainage parameters of the drainage system according to the known silt layer coverage rate or local silt layer thickness.
Abstract：
The complex geological conditions such as high water pressure and overlying silt layer are the key factors that affect the seepage characteristics and the waterproofing and drainage design of subsea tunnels. In order to systematically investigate the ambient water pressure distribution pattern and water inflow characteristics of subsea tunnel, the analytical solution for seepage field of subsea tunnel that takes into account overlying silt layer has been deduced by using the hydromechanical theories, and the corresponding numerical model has been created. Through comparison and analysis of the theoretical results, the suitability and accuracy of the numerical model have been verified. Through numerical simulation, the optimum limited drainage scheme and rational depressurization value for subsea tunnel have been obtained, the laws by which the factors such as silt layer thickness and coverage rate will affect the tunnel water inflow and the water pressure distribution pattern behind the lining have been further investigated, and the mechanism of action of overlying silt layer on the seepage characteristics of subsea tunnel have been revealed. As the results indicate: (1) As the depressurization value increases, the water drainage of tunnel decreases linearly, while the water pressure behind the lining increases linearly. With the same depressurization value,as the spacing between the circumferential French drain pipes increases, the water drainage of tunnel gradually decreases, while the water pressure behind the lining gradually increases. (2) When the silt layer thickness is 12 m,the optimum limited drainage scheme for mined subsea tunnel is as follows: for semi-closed waterproofing method,the waterproofing system is "circumferential French drain pipe + longitudinal circumferential French drain pipe with 6 m spacing", and the depressurization value is 400 kPa. (3) Increase of the silt layer thickness and coverage rate will decrease the water drainage and, to certain extent, decrease the water pressure behind the lining. At the junction between weakly weathered granite and silt overburden, the water pressure behind the lining changes abruptly,so priority should be given to optimizing the water drainage parameters of the drainage system according to the known silt layer coverage rate or local silt layer thickness.
JING Yifeng1 WANG Bo1 MEI Jie1,
2 XIONG Wenwei1 MENG Qingyu3
.Study on Water Pressure Distribution Pattern and Limited Drainage Design of Mined Subsea Tunnel[J] MODERN TUNNELLING TECHNOLOGY, 2024,V61(1): 84-95
2024, Vol. 61 