Application Research On Electromagnetic Detection And Water Inflow Prediction Of A Section Of Jingzhai Tunnel On Yunnan-Mo Railwa

In China’s "14th Five-Year" Plan and the 2035 Long-Term Goals Outline,it is proposed to coordinate the advancement of traditional and new types of infrastructure,building a modern integrated transportation system.This includes the development of the "eight vertical and eight horizontal" high-speed railways,and promoting railway construction like Yuxi to Mohan,Dali to Ruili,etc.,to enhance interconnectivity with neighboring countries.This will enhance railway transport capacity,leverage Yunnan’s geographical advantages,and advance the construction of international transport channels with surrounding countries.Consequently,investment in transportation infrastructure in the Yunnan region has increased,with more high-risk tunnels in complex geological mountainous areas under construction.However,due to complex topography,hydrogeology,and the influence of geological conditions and exploration technologies,it’s challenging to fully understand the hydrogeological conditions at the tunnel excavation face.tunnels often face frequent water inrush incidents caused by water-bearing bodies like rich caves,faults,and fracture zones,posing risks to construction workers and equipment,slowing down construction progress,and causing significant casualties and economic losses.Therefore,it is of great significance to use advanced tunnel engineering geological forecasting methods to predict the geological structures ahead of the tunnel excavation face,and accurately forecast the water content and inflow in water-rich areas.This can effectively reduce the blind spots in construction,provide early warnings for upcoming water inrush incidents,improve construction plans,and ensure the safety of tunnel construction workers.1)This paper starts with the basic principles of Ground Penetrating Radar(GPR),introduces the theory of finite difference time-domain(FDTD)forward modeling and the selection of GPR parameters,and uses the MATGPR software to numerically simulate factors affecting GPR detection of water bodies.The simulation results reflect the impact of water body shape,radius,dielectric constant,burial depth,and antenna center frequency on GPR detection of water bodies.Specifically,the shallower the water body’s burial depth,the larger its radius,and the higher its dielectric constant,the better the detection results.High antenna frequencies are suitable for shallow burial depth,high-precision water body detection,while low antenna frequencies are suitable for deep burial depth,rough water body detection.2)Forward simulations were conducted for typical water-bearing disasters in tunnels: interlayer water bodies,fault water bodies,and fault fracture zone water bodies.The reflection signals from interlayer water bodies appear hyperbolic,with a clear interlayer reflection interface and discontinuous phase axis.The fault water body’s reflection signals have strong continuity in the upper and lower phase axis,but as the fault depth increases,the amplitude decreases and the energy decays faster.Reflection signals from fault fracture zone water bodies exhibit continuous and intense phase axis,large electromagnetic wave amplitudes,rapid internal energy decay,embedded hyperbolic reflection waves,scattered wave distribution,smaller reflection wave amplitudes,and discontinuous phase axis.3)Regarding the detection and prevention of water disasters in the Jingzhai Tunnel on the Yuxi-Mohan Railway,an engineering geological forward model was established based on the actual radar detection results combined with on-site geological conditions.The water-rich area cone curve model was improved according to actual detection results and forward simulation results.A tunnel seepage model was established in conjunction with exposed conditions at the working face and geological exploration data,considering the water-bearing body structure,a revised groundwater dynamics inflow prediction formula was derived.This formula was used to predict the inflow in the section of the Jingzhai Tunnel on the Yuxi-Mohan Railway.After excavation,the established groundwater dynamics inflow formula showed a deviation of 11.3% in the initial maximum inflow calculation,indicating good prediction performance and applicability.This formula optimizes and improves the traditional groundwater dynamics formula.