Coupling Of Spectral/Hp Element Method And Rigid Immersed Boundary Method And Numerical Analysis Of Water Inrush

At present,a large number of national infrastructures such as traffic,water conservancy and hydropower were built in western mountainous areas and karst areas with extremely complicated topographical conditions and geological settings.In the process of construction,many kinds of geological disasters are likely to occur.Among them,water inrush was one of the most serious geological disasters in engineering construction.80%of major safety disasters were caused by water inrush during the tunnel excavation in China.The casualties and property losses caused by water inrush were more than caused by other geologic hazards.And it is also made serious concern to public.Because water inrush has the natures of suddenness and diversity,the disaster mechanism is very complex.It is difficult to understand the process of water inrush through the existing programs.The disaster-causing mechanism of water inrush was studied based on water inrush types.Several typical water inrush were investigated through the IB-SEM system.(1)Water inrush types is divided into two major categories and six minor groups.The two major categories are water inrush through filling structures and water inrush through the destruction of water resisting rock mass structure.Each category include three models.The first category includes direct water inrush,slip water inrush and piping water inrush respectively.The second category includes direct water inrush,key block water inrush and splitting water inrush respectively.(2)The finite element method of Semtex was used in this study which is the spectral/hp element method.The spectral/hp element method is a combination of finite element method and traditional spectral element method.It has not only the geometrical flexibility of the finite element method,but also the high accuracy of the spectral element method.Comparing with the low order finite method such as the finite element method,the finite volume method and the finite difference method,the spectral/hp element method is more efficient and less error to obtain an approximate solution for sufficiently problems.The spectral/hp element method has the following main characters:? The shape function was used in the spectral/hp element method,which based on the orthogonal polynomial.The spectral accuracy of each element is obtained by using the Lagrange interpolation method.? Comparing with the traditional gauss integral method,the quick tensor integration is used in the spectral/hp element method.Its characteristic is that it can guarantee the integral efficiency and also evaluate the validity of the element integration.? The unstructured grid is used to ensure the efficiency of computation and reduce the resource occupied by runtime.(3)The interaction between particles and fluid was investigated by the rigid immersed boundary method.The accuracy of this method was verified based on the computed results with the traditional body-fitted mesh in numerical simulation of the flow through the cylinder.Then the governing equations of particles motion and contact in fluid are constructed.The movement of the particles and the interaction between the fluid and the particles are investigated.This method avoided the problem of low computational efficiency and error caused by the re-division of the grid when the solids moved.Finally,the movement simulation of multi particles in the fluid was carried out,which can provide a completely new numerical simulation method.(4)In the first category of water inrush through filling structures,the interaction of particles-fluid and particles-particles were studied.Then the direct water inrush was investigated by the IB-SEM system.The slices method was modified and applied into the slip water inrush research.The strip analytical calculation model of fillings was built.The calculating equation of the minimum safe thickness was deduced by the force balance condition.A new engineering practical analytical method was formed.Finally a new numerical method for the realization of skeleton particles and fine particles was used by IB-SEM system,which simulated the whole process from the formation of seepage channel to the water inrush.(5)Based on Semtex simulation,the influence of different fracture width on the flow distribution under different Reynolds number was investigated.The instability mechanism of key block water inrush was researched through the force analysis of water resisting block.Then the key block water inrush was investigated by the IB-SEM system.Finally,according to the fracture theory,three different types of hydraulic fracturing were considered.(6)Based on the Fourier transformation and 3D immersed boundary method,the 3D IB-SEM system was established.Then using the open MPI and Hamilton HPC service,computing efficiency has greatly increased.The three dimensional pore flow was successfully investigated.(7)In the water inrush risk assessment,an attribute recognition model of water inrush risk evaluation was established based on attribute mathematic theory.The water inrush risk of the whole tunnel was evaluated by using this method.The results indicated that the attribute recognition model of water inrush risk evaluation is verified.