Research Of Propagation Law And Forward-inversion Modeling Of Spherical Wave In Mined-out And Multilayer Rock-soil

Spherical wave of point source in homogeneous medium is an important elastic dynamics model in engineering.In practical application,if the propagation distance of spherical wave is far,the scope of spherical wave front is too larger than that of the wave source,the wave source can be treated as a point.Mining shocks can be treated as spherical wave model of point source.For mining shocks,the heterogeneity of rock and soil medium underground is necessary to consider.Spherical wave propagation law,positive and inversion method of spherical wave in rock and soil media with mined-out areas and multilayer rock and soil have important theoretical and application value.For instance,the propagation laws of seismic waves through the coal mining area is an important subject in the study of focal mechanism.Stratification feature is another reflection of the complexity of rock mass underground in diggings.Spherical wave transmitted in multilayered parallel media,wave front become a hyperboloid.Research of forward modeling and inversion modeling of spherical wave in multilayered parallel media in diggings,and apply it to positioning of seismic sources in multilayered horizontal or inclined media in diggings,have important theoretical and application value in accurate positioning of the mine earthquake,will lay a foundation to improve the positioning accuracy in the way of making full use of imaging results of three dimensional tomographic of crust in diggings.By the method of theoretical derivation,model test and numerical calculation method,study spherical wave propagation law of point source in isotropic media and mined-out areas.Test model of the mechanisms of mining subsidence and building damage induced by the ground settlement under the action of coupling of dynamic load of mining shocks and mined-out area was established.In order to get spherical wave propagation law in isotropic media,the d'Alembert solution is applied.Differential equations of longitudinal and shear spherical wave of point source are solved.Central symmetry displacement field of point source is represented.It is a superposition of displacement flux source and displacement vortex source.The study reveals the analytical expression and mechanism of central symmetry displacement field of point source.In order to get spherical wave propagation law in mined-out areas,percussion test model of circular plate with hole is established.Radius where mined-out holes located,can be separated by mined-out holes for two.One is connecting the center of the circle,the other is far away from the center of the circle.The Simplify model test shows that,negative acceleration point to the center of the circle is monitored at the one far away from the center of the circle.Not only radial acceleration but also tangential acceleration is monitored at the edges of the circular plate perpendicular to the attachment of center of the circle and mined-out hole.The results can be used as a test basis of the mechanisms of intensified mining subsidence and intensified building damage induced by the ground settlement under the action of coupling of mining shocks dynamic load and mined-out area,horizontal acceleration is created in shared rock pillars of mined-out area and so on.Proposed to establish positioning method of mining shocks sources in multilayered horizontal or inclined media based on first arrival time of P wave.In order to study whether the propagation characteristics of stress wave in multilayer medium will affect localization algorithm or not,design a tapping test of double layer concrete.Double-layer percussion test results of the equivalent model show that:when wave velocity difference of dielectric layer increases,seismic refraction effect will not abate.This feature was beneficial for seismic phase identification of P-wave,and it is very good for picking up first arrival time of P-wave.Test results prove the fact that the positioning method based on the first arrivals time of P wave is reasonable and effective.According to the deduction of the forward and inversion modeling formula of spherical wave in multilayered horizontal media,take the method combined with inversion of source parameters and forward modeling for wave front of spherical wave,three positioning methods are established.They are the method of geometric average,the method combined with forward and inversion and the method based on forward of wave front.Based on the isochron concept in the process of deriving the law of refraction based on the Huygens principle,under the defined conditions,the method of geometric average is an analytical method of source depth calculation in double-layer horizontal media.Based on the obtaining of time when the earthquake happens through inversion and the forward modeling method for wave front of spherical wave in double-layer horizontal media,and the positioning method combined with forward and inversion in double-layer horizontal media is established.The new method can maintain positioning accuracy of the method of geometric average,and not only determine the source depth,but also calculate the horizontal coordinates of the source accurately.The larger values of positioning error of depth and horizontal coordinates derived by the positioning model combined with forward and inversion are all not greater than those by the geometric average method.Original time of earthquake is substituted into the wave front surface equation in multilayered horizontal medium as an unknown quantity.Based on the arrival time difference of monitoring stations,establish nonlinear equation set of which unknowns is equal to the number of nonlinear equations,thus a seismic sources positioning method based on forward of wave front is established.It established the positioning scheme based on the arrival time difference of monitoring stations.It is a positioning method which is based on arbitrary observation system.The error analysis of positioning calculation shows that:In several positioning conditions examined,the position error of method based on forward of wave front is less than the model combined with forward and inversion and the method of geometric average.In several special conditions of field setup,the positioning accuracy of the model combined with forward and inversion and the method of geometric average are poor.But the positioning accuracy of the model based on forward of wave front is far better in these special conditions of field setup.The positioning model based on forward of wave front is extended to the positioning of seismic sources in multilayered horizontal or inclined media,the results of calculation example show that,the positioning model based on forward of wave front is an effective method to solve the problem of source positioning in multilayered horizontal or inclined media.Spherical wave propagation and attenuation law,forward modeling and inversion modeling method of spherical wave in complex media are the theoretical basis of the research.And the research is combined with experimental verification and applied to corresponding engineering application.The research provides a new way of thinking for solving related problem.