Research On Comprehensive Evaluation Index Of Quality Condition For CRTS Ⅲ Slab Track

With the wide application and the increase of service life,operation speed,axle load and traffic density of CRTS Ⅲ prefabricated slab track,and with the multiple effects of train load,temperature load,water pressure and environmental erosion,the overall quality of slab track gradually deteriorates,which seriously affects the traffic safety.In order to better guide the maintenance of CRTS Ⅲ prefabricated slab track,improve the informatization level of railway engineering construction and operation,and achieve life cycle management of slab track,it is very important to determine a complete evaluation method of track quality state.Therefore,starting with the typical damage forms of slab track,this paper proposes the comprehensive quality condition index QCI to evaluate the overall quality of track bed.The main research ideas are as follows: firstly,the damage evaluation indexes of cracking and gap were proposed,in which the index weight coefficient is determined based on Entropy Weight Method-Fuzzy Analytic Hierarchy Process(EWM-FAHP).Secondly,the finite element model including cracking damage and gap damage were established to modify the index weight.Finally,the comprehensive quality condition index is proposed,and applied to the engineering example,and the maintenance suggestions were given.The main research contents and conclusions of this paper are as follows:(1)Based on the theory of linear elastic fracture mechanics and extended finite element,the finite element calculation model of CRTS Ⅲ prefabricated slab track with cracking damage was established to analyze the crack propagation,in which the crack propagation laws of different crack types,crack length,crack width and acting parts were studied.(2)The finite element calculation model of CRTS Ⅲ prefabricated slab track with interlayer gap damage was established to analyze the stress and displacement of track slab,in which the influence laws of different positions and grades of interlayer gap were studied.(3)The finite element calculation model of CRTS Ⅲ prefabricated slab track with both cracking damage and interlayer gap damage was established to analyze the stress,displacement and crack propagation,which could determine the weight of the index in the comprehensive evaluation index.(4)The calculation methods of cracking condition index(CCI)and gap damage index(GDI)were proposed.In the formula,it is creatively proposed to use crack interspace volume(CIV)and gap interspace volume(GIV)to measure the degree of damage.After that,based on Entropy Weight Method-Fuzzy Analytic Hierarchy Process(FAHP),the weight coefficients of relevant indexes were determined.And then,combining with the results of the finite element modeling to modify the weights.Thus,the final weights were determined.(5)Combining with CCI and GDI,the calculation method of the comprehensive quality condition index(QCI)was proposed.In the formula,the damage correction function GDICCIf),(was innovatively proposed to measure the deterioration effect caused by the combined effect of double damage.(6)The comprehensive quality condition evaluation index was applied to three engineering examples.And the results are as follows: CCI were 88.55 points,74.56 points and 63.86 points respectively,and GDI were 86.95 points,83.68 points and 77.17 points respectively,thus,QCI were 83.26 points,74.57 points and 66.21 points respectively.The rationality of evaluation indexes and evaluation methods of proposed CCI,GDI and QCI were confirmed.And finally,the maintenance suggestions of engineering examples were put forward.