Study On The Influence Of S-wave Arrival Time On The Location Of Microseismic Source And How To Deal With It

As a safe and effective monitoring method,microseismic monitoring technology has been widely used in rock engineering such as mines and tunnels.Location of microseismic source is one of the main contents of this technology,its results can directly affect the early warning and prediction work in the dangerous area of the project,so it has always been a research hotspot at home and abroad.But most of the research and application on the location of microseismic source only use the arrival time of P wave of microseismic signal.P-wave arrival is easy to be affected by the surrounding environment and other factors,so it is difficult to accurately locate.The actual monitoring range is also easy to be limited when P-wave arrival is used only which cannot guarantee the positioning accuracy and stability outside the sensor array.Therefore,the S-wave arrival time is added in the process of micro-source location.Firstly,the P-wave and S-wave arrival characteristics of two types of microseismic signals are collected and analyzed through field tests.Secondly,taking the microseismic events of tunneling blasting as the research object and using three kinds of arrival time collocation methods to calculate the source location respectively,and then studied the effect of S-wave arrival time on the location of microseismic sources under several bad sensor arrays.Finally,to solve this problem that it is difficult for the S-wave arrival time to be automatically picked up by the algorithm,a new location algorithm based on maximum amplitude is proposed and applied in tunnel engineering.The main conclusions are as follows:(1)Compared with the rock fracture microseismic signal,the P-wave energy of the microseismic signal of tunneling blasting is larger,the amplitude change around the time is more obvious,so it has better pickup characteristics.However,the S-wave arrival time of these two microseismic signals is superimposed on the P-wave coda,which makes it difficult to be automatically picked up by the algorithm.With the attenuation of the signal or other interference,the difficulty of picking up will increase,even seriously affecting the results of manual experience pickup.(2)When the microseismic event is located outside the sensor array,the positioning result error is large when only P wave arrives,but when the trigger sensor is small,the positioning calculation or the positioning instability will be impossible.When S wave arrives,the positioning accuracy can be indirectly controlled by reducing the positioning error of the microseismic source relative to the direction of the array.The problem of positioning instability caused by using the least P-wave arrival time is effectively solved.In addition,under some special conditions,the positioning results can also play a certain monitoring and early warning effect by using P-wave and S-wave arrival positioning of two sensors.(3)Micro-source localization algorithm based on maximum amplitude can effectively avoid S-wave arrival pickup error and has achieved good localization effect in actual tunnel engineering,but there are some limitations.