Study On Acoustic Emission Characteristics And Assessment Of Cement Emulsified Asphalt Mortar Compression Damage

Cement asphalt mortar(CA mortar)is widely used in high-speed rail plate-type ballastless track structure because of its good toughness and certain strength.It can support the track plate and slow down the vibration of the track plate,and is one of the key materials to ensure the safety and smooth operation of the train.Therefore,it is very important to study the damage evolution law of CA mortar in the use process.As a real-time and dynamic nondestructive testing method,acoustic emission technology has been applied to the study of mechanical properties of ordinary concrete and other materials,so it can also be used in the mechanical properties and damage assessment of CA mortar.In this paper,through experimental research and theoretical analysis,acoustic emission characteristics and damage assessment of CA mortar under compression failure process are studied.The main research contents and conclusions are as follows:The CA mortar with different leaching ratio,loading rate and initial static load was subjected to compression failure test,and the acoustic emission test was carried out simultaneously.The test and test results show that the increase of leaching-cement ratio will enhance the toughness of CA mortar,weaken the brittleness,and significantly reduce the compressive strength,slow down the damage process,and increase the acoustic emission signal accumulation value.With the increase of loading rate,the compressive strength of CA mortar increases,the strain rate also increases,the loading time is shortened,and the cumulative value of acoustic emission signal decreases.With the increase of initial static load,the compressive strength of CA mortar decreases,the loading time prolongs,and the cumulative value of acoustic emission signal increases.Combined with the stress-strain curve and the macroscopic phenomenon of the specimen in the test process,the failure process was divided into stages,and the acoustic emission signals in the failure process were analyzed by the experience diagram and distribution diagram of acoustic emission characteristic parameters.The results show that with the increase of leaching ratio,the number of AE events with higher energy value and ringing count increases,and the AE signals generated in the late loading period increase.With the increase of loading rate,the AE signals generated before and during the loading period are relatively reduced,and the number of AE events with high energy and high ringing count is increased.When the initial static load acts on the acoustic emission signal,it presents a "low-high-low" winding growth trend.The larger the initial static load is,the more uniform the distribution of acoustic emission signal is,and the growth trend is closer to linearity.Combined with the basic theory of damage mechanics,the relationship between damage variables and acoustic emission characteristic parameters is established.Based on the acoustic emission characteristic parameters,the damage process of CA mortar is analyzed.It is found that when the strain level is greater than 0.363,the damage develops rapidly.Combined with the ae rate process theory,has established the CA mortar strain level and accumulated acoustic emission ringing count and cumulative energy five order polynomial model,and the experimental data fitting,get the probability density function and damage model,the analysis of the income curve,found the damage factor D is greater than 0.64,the CA mortar destroyed;Based on the analysis of acoustic emission rate parameter A obtained by fitting,the damage assessment method of CA mortar compression damage based on the variation law of A value is proposed.This method can evaluate the safety of the CA mortar without damaging the original structure,thus realizing the purpose of nondestructive testing.