Research On Water Storage Characteristics Of Igneous Rock Faults And Its Perturbed Water Inrush Mechanism

With the country’s need to build a modern and high-quality comprehensive threedimensional transportation network,my country has built a large number of high-risk mountain tunnels.During the construction of these tunnels,it is very easy to expose the disaster-causing structures of water-rich faults,and large-scale water inrush disasters occur.Damaged equipment will cause delays in the construction period,and even endanger the safety of construction workers.In essence,tunnel fault water inrush is a process in which the free water enriched in the fault quickly flows into the clearance surface through the primary or secondary fracture network of the fault,which is the product of the multi-physical field coupling of stress-seepagedamage.The multi-physics coupling mechanism in the process of penetrating the water-rich fault fracture zone has important theoretical value and engineering practical significance for the prevention and control of fault water inrush disasters.Relying on the Qinling Tiantaishan Tunnel Project,on the basis of data collection and investigation,this paper uses theoretical analysis,numerical simulation and other means to establish a stress-seepage-damage coupled numerical model,and conduct in-depth research on the mechanism and evolution of water inrush through faults under the tunnel.The main research results are as follows:(1)Using the relative relationship between the characterizing volume unit and the engineering scale,the fault fracture zone is simplified as a quasi-continuous medium.Based on the Mohr-Coulomb criterion,a macroscopic phenomenological elastoplastic damage constitutive model is established,and the dynamic evolution formula of the permeability coefficient of the faulted rock mass under the elastic-plastic state is given.Secondly,on the basis of the above research,the core control equations are subjected to finite element discretization,and the stress reflection algorithm is used to realize the numerical solution of the elastic-plastic damage model,and the discrete equations of the elastic-plastic stress field and seepage field are obtained.The seepage field is regarded as two independent subsystems,and the physical fields are independently iteratively coupled to solve,and the stress-seepagedamage coupling solver is designed.(2)Using the "three-zone theory",the fault fracture zone is regarded as a threedimensional complex geological body composed of a fault core,an induced fracture zone and a complete surrounding rock.The enrichment law of high-pressure free water.Based on the secondary development of the large-scale nonlinear finite element calculation and simulation software Abaqus,combined with the engineering geological and hydrogeological characteristics of the Qinling Tiantaishan Tunnel,a stress-seepage-damage coupling numerical model was established in the process of the tunnel passing through the water-rich fault fracture zone.The evolution law of pore water pressure field,stress field,displacement field,damage field,water inrush speed,and water inrush amount during the excavation process was numerically simulated,and the evolution process of water inrush through the tunnel fault was obtained.(3)Control the change of a single factor,compare and study the change law of multifield information under different initial in-situ stress environments and different initial fault hydraulic conditions,and further study the coupling mechanism of stress-seepage-damage field in the fractured zone of the water-rich fault under the tunnel.It shows that the greater the initial in-situ stress and the initial fault water pressure,the more severe the damage to the rock mass caused by the excavation disturbance,and the more serious the water inrush disaster.(4)This paper summarizes some beneficial attempts taken when the Qinling Tiantaishan tunnel passes through the igneous rock fault fracture zone,and believes that it is more reasonable to adopt the comprehensive treatment of "pumping and drainage + local radial grouting + full-section curtain grouting",and it is more reasonable for similar water-rich Hard rock construction has certain reference and reference significance.