Study On Cracking Characteristics Of Cement-stabilized Macadam Materials Based On Acoustic Emission Technology

Cement stabilized macadam is widely used in China’s road base because of its high stiffness and strong load diffusion capacity.However,it is relatively brittle and sensitive to temperature and humidity,which makes it easy to be damaged.The study on the initiation and propagation of micro-cracks in pavement structure has always been a hot topic in pavement mechanics.Analyzing the crack mechanism of cement stabilized macadam at the micro and micro level is an important basis for describing its macro-crack behavior and improving its crack prevention and control performance.As an efficient non-destructive testing technology,acoustic emission technology can identify the stress wave signal of material in the process of fracture and deformation,and establish the relationship between acoustic emission parameters and material fracture parameters and strength,which has been widely used in the field of material crack detection.Based on this,this paper USES acoustic emission,CT scan detection technology,numerical simulation,etc.,to study the crack propagation characteristics of cement stabilized macadam,so as to provide theoretical basis and reference for the crack prevention and control technology of pavement structure.The relevant studies and main conclusions are as follows:(1)According to the analysis of acoustic emission characteristic parameters such as acoustic emission cumulative ringing count,accumulated energy and amplitude,the crack development and failure process in unconfined compression test of cement stabilized macadam specimens can be divided into four stages:compaction,microcrack initiation,crack stable propagation and failure deformation.The arc trend of acoustic emission characteristic parameters such as acoustic emission ringing count,energy and amplitude reflects the development and expansion law of microcracks in the specimen,and the second increase of ringing count and amplitude before the peak load is taken as the precursor characteristics of peak failure,which can effectively judge the cracking degree of cement stabilized macadam.(2)Different stages of unconfined compressive strength test of standard specimens of the cement stable macadam mixture,layered scanning,by two-dimensional CT tomography(CT)images of the specimens,through the analysis of the mesoscopic structure of pore distribution of the image,get the cement stabilized gravel material in the cracking pattern is down load,reveals that the material of the cement stable macadam mixture,the evolution process of the mesoscopic compression damage;At the same time,acoustic emission characteristic parameters and two-dimensional positioning images are combined to verify the accuracy of acoustic emission technology.(3)The PFC2D technique was used to simulate the unconfined compressive resistance process of cement stabilized macadam,and the microcosmic mechanism of fracture development and failure was analyzed.The simulated stress-strain curve is consistent with the four stages of the cumulative event number curve,which verifies the scientificity and rationality of acoustic emission in predicting the failure of cement-stabilized macadam.