Microseismic(MS)event locations are vital aspect of MS monitoring technology used to delineate the damage zone inside the surrounding rock mass.However,complex geological conditions can impose significantly adverse ef...Microseismic(MS)event locations are vital aspect of MS monitoring technology used to delineate the damage zone inside the surrounding rock mass.However,complex geological conditions can impose significantly adverse effects on the final location results.To achieve a high-accuracy location in a complex cavern-containing structure,this study develops an MS location method using the fast marching method(FMM)with a second-order difference approach(FMM2).Based on the established velocity model with three-dimensional(3D)discrete grids,the realization of the MS location can be achieved by searching the minimum residual between the theoretical and actual first arrival times.Moreover,based on the calculation results of FMM2,the propagation paths from the MS sources to MS sensors can be obtained using the linear interpolation approach and the Runge–Kutta method.These methods were validated through a series of numerical experiments.In addition,our proposed method was applied to locate the recorded blasting and MS events that occurred during the excavation period of the underground caverns at the Houziyan hydropower station.The location results of the blasting activities show that our method can effectively reduce the location error compared with the results based on the uniform velocity model.Furthermore,the obtained MS location was verified through the occurrence of shotcrete fractures and spalling,and the monitoring results of the in-situ multipoint extensometer.Our proposed method can offer a more accurate rock fracture location and facilitate the delineation of damage zones inside the surrounding rock mass.展开更多
The Early Cretaceous granitic complex in Highland 1248 of Daxing'anling successively consists of intruded granodiorite,monzonite granite and syenite granite. Through test analysis on the major,trace and rare earth...The Early Cretaceous granitic complex in Highland 1248 of Daxing'anling successively consists of intruded granodiorite,monzonite granite and syenite granite. Through test analysis on the major,trace and rare earth elements of the intrusive complex,this study focuses on the source characteristics and tectonic environment of the original magma of intrusive complex. The results show that the intrusive rocks in Highland 1248 are meta-aluminous-peraluminous rocks in calc-alkaline series with homologous characteristics in δEu negative anomalies; the complex is enriched in LILE( Rb,Cs and K) and depleted in HFSE( lanthanide,Sc,Y,U,Nb and Ta),displaying the geochemical characteristics of I-type granites in active continental-margin subduction zones. The complex also has the characteristics of granites after the collision of plate with rich aluminum and high potassium,but significantly depleted Nb,Ta,Ti,P and other elements,i. e. in the orogenic evolutionary stage. The zircon U-Pb SHRIMP isotopic apparent age of the complex in Highland 1248 is 140. 0--141. 0Ma,and the formation time is in Early Cretaceous.展开更多
基金the Key Program of National Natural Science Foundation of China(52039007)for providing financial support.
文摘Microseismic(MS)event locations are vital aspect of MS monitoring technology used to delineate the damage zone inside the surrounding rock mass.However,complex geological conditions can impose significantly adverse effects on the final location results.To achieve a high-accuracy location in a complex cavern-containing structure,this study develops an MS location method using the fast marching method(FMM)with a second-order difference approach(FMM2).Based on the established velocity model with three-dimensional(3D)discrete grids,the realization of the MS location can be achieved by searching the minimum residual between the theoretical and actual first arrival times.Moreover,based on the calculation results of FMM2,the propagation paths from the MS sources to MS sensors can be obtained using the linear interpolation approach and the Runge–Kutta method.These methods were validated through a series of numerical experiments.In addition,our proposed method was applied to locate the recorded blasting and MS events that occurred during the excavation period of the underground caverns at the Houziyan hydropower station.The location results of the blasting activities show that our method can effectively reduce the location error compared with the results based on the uniform velocity model.Furthermore,the obtained MS location was verified through the occurrence of shotcrete fractures and spalling,and the monitoring results of the in-situ multipoint extensometer.Our proposed method can offer a more accurate rock fracture location and facilitate the delineation of damage zones inside the surrounding rock mass.
文摘The Early Cretaceous granitic complex in Highland 1248 of Daxing'anling successively consists of intruded granodiorite,monzonite granite and syenite granite. Through test analysis on the major,trace and rare earth elements of the intrusive complex,this study focuses on the source characteristics and tectonic environment of the original magma of intrusive complex. The results show that the intrusive rocks in Highland 1248 are meta-aluminous-peraluminous rocks in calc-alkaline series with homologous characteristics in δEu negative anomalies; the complex is enriched in LILE( Rb,Cs and K) and depleted in HFSE( lanthanide,Sc,Y,U,Nb and Ta),displaying the geochemical characteristics of I-type granites in active continental-margin subduction zones. The complex also has the characteristics of granites after the collision of plate with rich aluminum and high potassium,but significantly depleted Nb,Ta,Ti,P and other elements,i. e. in the orogenic evolutionary stage. The zircon U-Pb SHRIMP isotopic apparent age of the complex in Highland 1248 is 140. 0--141. 0Ma,and the formation time is in Early Cretaceous.
