Research On Mechanisms Of Key Factors And Reliability For Microseismic Source Location

The microseismic (MS) monitoring technique is a real time, dynamic, and continuousmonitoring method which has been widely used in the general area of geotechnicalengineering, such as: mining, petroleum, and slopes engineering. Source location is thefoundation of the MS technique. It has been the research focus and hotspots in the MS area.The influence factors and their mechanisms of MS source location, and the reliabilityevaluation of source location are the key scientific and technical issues which need to addressurgently at present. Thus, this paper focuses on the MS source location and reliabilityevaluation problems by using theoretical analysis, laboratory physical experiment, numericalsimulation, field testing and practice. The influence law of MS source location affected by keyfactors, and the key factors in the mechanisms of MS source location are revealed. On thisbasis, the automatic identification model of MS arrival wave types (APSIM), Simplex MSsource location method based on APSIM (APSIM-Simplex), and comprehensive evaluationsystem for source location reliability (SLRES) are built. In the end, a new MS source locationand reliability evaluation system is developed. The verification tests and applications arecarried out.The influence law of MS source location affected by the MS network, velocity model, andarrival time are studied by laboratory physical experiments. Results show that the sourcelocation accuracy is relative high inside of MS network. The accuracy and stability of thesource location consistently reduce with the source away from the network center. Theinfluence of MS network to the source location is directional. Both the accuracy and changecharacteristics of source location in different directions are different, and there exists thequickest-decline-direcion of location accuracy. The source location accuracy decreases withthe increasing of velocity and arrival time errors, and the decline rate of location accuracybecomes faster and faster. The source locations at different places are affected differently bythe same input errors. Specifically, the source locations at the central region of the networkhave been less affected by the input errors than the outside of the network.Based on the arrival-time-difference source location theory, the hyperbolic governingequation of MS source location (MHGE) is established, and the non-uniformity geometricalcharacteristic of hyperbolic field is analyzed as well. And then, the geometrical spreadingeffect and the directional control effect of the MS network are revealed. Additionally, thethree-dimensional space quantitative models of these two effects are constructed respectively.The direction angle of pairing sensors is proposed. And then, based on the geometrical spreading effect, the directional control effect, and the direction angle, the basic principles ofMS network layout are concluded. The propagation characteristics of velocity error andarrival time error are compared analytically. Based on the critical hyperbola and the networklayout, the monitoring area can be divided into two regions. In general, the arrival time errorshave the major influence in the central region, and the velocity errors have the majorinfluence in the remaining area.There are observed arrival time differences, theoretical limit arrival time differences of Pwave and delayed wave between two sensors. According to the geometrical characteristics ofMS network and monitoring space, the arrival time differences analysis as well as and stationresiduals, the arrival time difference analysis table and station residual analysis table areformed, and then the APSIM and APSIM-Simplex are built. Results from field tests showsthat P wave, S wave, delayed waves and external outlier waves can be identified correctly andeffectively by APSIM. The accuracy and stability of source location are greatly improved byusing APSIM-Simplex.The event residual index, sensitivity index, and hit sequence index are proposed, andevaluation criteria of these3indexes are defined. The SLRES is established based on theabove indexes, and verification tests are carried out. Results indicate SLRES can evaluate thesource location accuracy and stability comprehensively and effectively. The evaluation resultsof SLRES accordant with the actual situation.Based on the APSIM, APSIM-Simplex, and SLRES, a MS source location and reliabilityevaluation system is developed. In the end, this system is applied to the engineering practiceand applications. The successful applications show this system can achieve the identificationof MS arrival wave types, high accuracy source location, and comprehensive evaluation forsource location reliability. It meets the needs of field MS monitoring.This paper profoundly reveals the key factors in mechanisms of MS source location. Theresearch results have important theoretical and practical significance for improving the MSsource location accuracy and stability, and driving the research of MS monitoring and earlywarning for rockbursts.