Simulation Analysis Method And Application Of Grouting Diffusion In Complex Karst Fracture And Pipeline

The construction of underground engineering in karst area is usually accompanied by complex geological conditions,crisscross karst fractures and conduits,and abnormally complex groundwater runoff conditions,which lead to the frequent occurrence of water inrush disasters and great difficulty in treatment.In the treatment of water inrush in underground engineering,grouting is the most commonly used method.The law of slurry diffusion and migration is of great significance to engineering design and construction.Because of the complexity of karst medium,the diffusion process of slurry is very hidden,and the diffusion law of slurry can not be judged directly.Therefore,the construction of three-dimensional geological model of complex karst medium is the basis for the study of grouting diffusion mechanism.On the other hand,the engineering geological environment in karst area is complex and changeable.The diffusion law and plugging mechanism of slurry under the condition of dynamic water are lack of effective research means.The numerical method can realize the visual simulation of the slurry diffusion process,but its application is limited by the imperfection of the slurry water interaction theory.In addition,the different media of rock mass will inevitably lead to the great difference of slurry diffusion process,and the grouting diffusion theory involved will also be different.At present,there is still a lack of a unified grouting simulation and analysis method for complex karst fracture and conduit media.In view of the above problems,through theoretical analysis,numerical simulation and experimental verification,this paper puts forward a three-dimensional geological modeling method of complex karst fracture and conduit media,establishes a unified simulation analysis method of dynamic water grouting diffusion of fracture and conduit media,and carries out the verification and application research of numerical method.It can provide theoretical basis for the selection of grouting material,the determination of grouting parameters and the optimization of grouting technology.The main research work and results are as follows:(1)According to the characteristics of joints and bedding in exposed rock mass,data collection is carried out respectively,and the occurrence information of key joints is extracted by regional growth algorithm.Combined with 3D point cloud data and real image data,the semi-automatic bedding information collection is carried out.From the perspective of geometry and geostatistics,the grouping and spatial density distribution functions of complex structural planes in three-dimensional space are given,and the corresponding calculation program is compiled to complete fracture network model construction.Finally,a deterministic-stochastic identification and modelling method of discrete fracture networks using(DSIM)is proposed to reduce the uncertainty in the rock mass.Based on the improved coupled Markov chain theory,a fractured rock mass model considering the variation of strata is established.Surface model of rough conduit is constructed by Fourier transform.Based on existing three-dimensional spatial datavisualization technology,the three-dimensional spatial data modeling analysis of limestone mine is carried out.The key technologies of integrated management and spatial analysis of multi-source complex spatial data are explored.It provides a basic model for simulation and analysis of grouting diffusion.(2)The diffusion solidification model of grouting and the corresponding numerical simulation method(SDS)are proposed.The grouting process is divided into a slurry diffusion and solidification process in order,which has obvious advantages over the traditional method.The slurry of different order obeys their respective viscosity time-varying function.The time characteristic of viscosity change of the slurry is reasonably characterized.Based on the theory of computational fluid dynamics and multiphase flow,the spatial position changes of slurry injection of defferent order are tracked and updated,and then the spatial characteristics of slurry viscosity changes are reasonably characterized.Finally,the problem of time-space dual variation of slurry viscosity is solved.Based on SDS method and incompressible multiphase flow model,volume of fluid method is used to track the movement of phase interface of different order in a fixed Eulerian grid.The method of inverse gradient is introduced to ensure the sharpness of phase interface.Flux modified transport algorithm is used to ensure the boundedness of the fraction of slurry phase and water phase.Furthermore,the problem of fine description and tracking of slurry phase and water phase interfaces is solved.In view of the non convergence of calculation caused by the increase of viscosity of slurry,based on experimental test and theoretical research,a viscosity threshold model of slurry is proposed,which solves the convergence of calculation under complex problems such as double variation of viscosity in time and space,spatial search of slurry diffusion area and tracing of slurry diffusion morphology.The simulation of slurry diffusion and phase change solidification in the process of dynamic water grouting is realized.SDS method uses unified multiphase flow theory and numerical algorithm to characterize the interactions between slurry and water.The model and numerical algorithm do not depend on the media characteristics of injected fracture or conduit.This method can be applied to laminar flow,turbulent flow and pipe turbulent flow.Therefore,SDS method unifies dynamic water grouting simulation analysis of fracture and conduit media.It avoids the problem of media coupling simulation caused by different models and algorithms.The simulation analysis of the whole process of viscosity-pressure-velocity spatiotemporal evolution in the slurry diffusion process of fracture and conduit media is carried out.(3)The validity and feasibility of SDS method in the condition of static and dynamic water are analyzed.The influences of Dynamic water flow rate on grouting pressure,upstream diffusion distance and downstream diffusion form are studied.This model can describe the sedimentary form of fracture dynamic water grouting diffusion.Furthermore,the feasibility of the model in study of grouting diffusion mechanism of wide fracture and three-dimensional complex fracture network is verified in engineering scale.Using the self-developed conduit dynamic water grouting simulation test system,the laboratory test of dynamic water grouting for rapid setting slurry was carried out.The validity and feasibility of SDS calculation method in the simulation of conduit dynamic water grouting are verified by comparison.Furthermore,the feasibility of SDS method in the study of diffusion mechanism of dynamic water grouting in rough conduit is verified in engineering scale.It provides a reasonable and effective method for revealing the plugging mechanism of dynamic water grouting for conduit media in engineering scale.(4)Aiming at the plugging problem of dynamic water grouting in large flow karst conduit,the mechanism of flow control,rate control and double-hole joint grouting was revealed by SDS simulation analysis.In order to provide a theoretical basis for the actual grouting production,optimize the grouting design scheme,and provide a basis for the rational selection of grouting material.The research results of flow control,rate control and double-hole joint grouting are applied to the pingnan superlarge water gushing project in guangxi.It guides the design of grouting scheme,realizes the successful plugging of large flow karst conduit,and liberates the mineral resources under the influence of water damage.