Groundwater inflow during tunnel excavation is a common problem in practice. How to accurately predict its occurrence during the construction is still a challenging problem for tunnel designers. A numerical method, based on the coupled model involved in artery fractures described by a discrete fractured network model and ramification fractures and rock matrix described by the equivalent continuum medium model, is developed to calculate the groundwater inflow of underground tunnel. The model is calibrated with the observed groundwater levels in the study domain. The results in the model calibration show that calculated and measured groundwater inflows agree well. Sensitivity analysis indicates that groundwater inflow increases with the increase of precipitation rate, hydraulic conductivity of rock matrix and fracture aperture. The effect of fracture aperture on groundwater inflow is predominant, owing to the occurring of many artery fractures around the tunnel, which leads to much groundwater flowi...

Leakage is a common phenomenon in dams, and its early detection is critical for dam safety. In the present study, a new method based on tracer tests is applied to detect and quantify leakage in the Wanyao Dam, Jiangshan City, China. The objective is to detect the leakage zone of a dam wall by combining the natural tracer test and the artificial tracer test. Temperature, electrical well-logging tests with nature tracers, and the artificial tracer test with salt (NaCl) were conducted using 48 and 5 pre-existing boreholes, respectively. Using natural tracer tests, the 48 boreholes are categorized into 4 leakage classes: (1) Class 1, high connectivity within whole borehole; (2) Class 2 high connectivity at lower depths; (3) Class 3, weaken connectivity; and (4) Class 4, safe boreholes with no connectivity. Using the proposed method, specific leakage rates of some boreholes were estimated. The results of the new method are validated by comparison with those from natural tracer tests, site-investigation, and historical observation data. Overall, the new tracer test has the following merits: (1) low cost, (2) environment friendliness, and (3) is simple to apply. Moreover, the proposed method improves the accuracy of traditional tracer tests for detecting leakage zones.

Based on the geological and hydrogeological conditions of the Jurong Pumped Storage Hydroelectric Power Station (JPSHP), a 3D groundwater flow model was developed in the power station area, which took into account the heterogeneity and anisotropy of fractured rocks. A control inversion method for fractured rock structural planes was proposed, where larger-scale fractures were used as water-conducting media and the relatively intact rock matrix was used as water-storage media. A statistical method was used to obtain the geometric parameter values of the structural planes, so as to obtain the hydraulic conductivity tensor of the fractured rocks. Combining the impermeable drainage systems of the upper storage reservoir, underground powerhouse and lower storage reservoir, the 3D groundwater seepage field in the study area was predicted using the calibrated model. The leakage amounts of the upper storage reservoir, powerhouse and lower storage reservoir were 710.48 m³/d, 969.95 m³/d and 1657.55 m³/d, respectively. The leakage changes of the upper storage reservoir, powerhouse and lower storage reservoir were discussed under the partial and full failure of the anti-seepage system. The research results provide a scientific basis for the seepage control of the power station, and it is recommended to strengthen the seepage control of the upper and lower storage reservoirs and the underground powerhouse to avoid excessive leakage and affect the efficiency of the reservoir operation.