Research purposes: Anti-floating waterproof level is a very important parameter in the station foundation pit engineering. Its value is too high will greatly increase the project cost, too low and there is engineering risk. The current standard only has the principle stipulation, has not and cannot have the quantification value standard. Therefore, for the station engineering with large foundation pit, it is of great engineering significance to carry out the special investigation and study of anti-floating waterproof level. Taking the foundation pit project of Nanchang East Station of Nanchang-Jingdezhen-Huangshan High-speed Railway as an example, through the field measurement of pore water pressure, indoor and outdoor permeability tests, and model tests of groundwater seepage field, the determination of anti-floating waterproof level is studied.
Research conclusions: (1)The recommended value of anti-floating waterproof level: 0.5 m (20.00 m absolute elevation) can be used in service period, and 20.50 m absolute elevation can be used in construction period. If the site elevation of the proposed project is adjusted, the value of 0.5 m below the adjusted site elevation is recommended for the service life, and the value of the adjusted site elevation is recommended for the construction life.(2)There is no hydraulic connection between surface water and groundwater in the project sites such as Yaohu Lake, Ganfu plain main channel and Fu River. There is a direct hydraulic connection between confined water of groundwater and fissure water of bedrock. Confined water flows into fissure of bedrock. In the region where fissure water is abundant and confined, fissure water of bedrock makes up confined water. In the proposed site, the upper stagnant water and confined water are located above the basement of the proposed building, which has great influence on the project.(3)The long-term maximum water level of the upper stagnant water shall be taken into account according to the ground elevation after the construction of the project, and the long-term maximum water level of the confined water shall be taken into account according to 19.00 m.(4)The results of this study can provide reference for the determination of anti-floating waterproof level of similar projects.