Measuring Velocity And Direction Of Groundwater In Borehole And Numerical Simulation Of Groundwater In Beishan Area,gansu Province

The radionuclides released from the high-level waste geological repository will be dispersed into the water and migrate from the geosphere to the biosphere through the carrier effect of groundwater.Research on velocity and direction of groundwater is helpful to understand the occurrence status of groundwater and to identify the groundwater circulation pattern,and it can provide a basis for the research of nuclide migration and long-term safety evaluation of disposal sites.A full understanding of the local hydrogeological conditions and movement laws of groundwater of the Beishan high-level radioactive waste geological disposal site in Gansu can help to evaluate the safety and reliability of the geological repository.Velocity and direction of groundwater has become an indispensable component in the hydrogeological study of high-level radioactive waste geological disposal.The study of velocity and direction of groundwater can offer data support for groundwater seepage field simulation and hydrogeological evaluation of high-level waste disposal repository area.The related achievements are also very important to promote the application of the charging method to determine the flow velocity and flow direction in low-permeability fractured rock areas.In this paper,the topography and geomorphic characteristics,meteorological and hydrological characteristics,basic geological characteristics of the area were obtained by collecting information.The charging method was divided into three test conditions to measure actual velocity and direction of groundwater of the borehole BSQ11 on the basis of the analysis of hydrogeological conditions The infiltration velocity of groundwater BSQ11 was obtained through water injection test.a three-dimensional numerical simulation study of groundwater in the study area was carried out,and the groundwater flow field around the borehole BSQ11 was calculated according to establishing a three-dimensional geological model.and generalizing the geological structure and aquifer characteristics of the study area The following results were achieved:1.The groundwater type in the area is mainly bedrock fissure water.in the area The groundwater hydrochemical type is mainly Na-Cl-SO_4.and the average of TDS is4.35g/L in the area.2.?¹⁸O and?D are relatively enriched in shallow groundwater in the study area.The maximum value of Soil Permeability(K_fs)is 7.39×10^-4 m/s and the minimum is1.94×10^-6 m/s in typical gully aerated zone.It decreases exponentially with depth in the vertical direction.3.During the measurement of the actual groundwater velocity in the borehole BSQ11 by charging method,a total of 33 potential observations were carried out,and25 actual groundwater velocity were obtained.Overall,the actual groundwater velocity lies between 4.48×10^-4?4.58×10^-3 m/s in the shallow part of the borehole.The average is 1.26×10^-3 m/s and the direction of groundwater is between 41?70°.4.The permeability coefficient of the borehole BSQ11 lies between 7.04×10^-6?1.03×10^-5 m/s and the average is 8.31×10^-6m/s according to water injection test.Infiltration velocity of groundwater is between 2.11×10^-7?3.08×10^-7m/s and the average is 2.49×10^-7m/s through water injection test.5.Numerical simulation of groundwater shows that the direction of groundwater around the borehole BSQ11 is from southwest to northeast.Groundwater flows along the stike of faults F1 and F2,flows along perpendicular to the strike of fault F3.The long-average annual supply of the groundwater system calculated by the model for many years is 46.61m³/a.and the total discharge is 45.38m³/a.The equilibrium difference is 1.23m³/a.The total recharge of the groundwater system calculated by the model is approximately equal to the total discharge.