Research On Evaluation Index Of Interface Damage For CRTS Ⅲ Slab Track

With the wide application of CRTS Ⅲ slab ballastless track and the increase of its service life,under the coupling effect of train load,temperature and other environmental factors,it is inevitable to cause damage,among which the interface damage between track slab and selfcompacting concrete is one of the common damage.In order to guide the maintenance work of slab ballastless track after interface damage,relevant departments are also revising and improving the maintenance rules of CRTS III slab ballastless track.However,the index proposed in the current maintenance rules are often defined for a single damage type,and the evaluation of damage index is only qualitative analysis.Therefore,it is of great significance to study the evaluation index and evaluation method of interface damage,and put forward an evaluation index that can comprehensively evaluate the impact of interface damage on ballastless track bed,so as to guide the daily maintenance of CRTS Ⅲ slab ballastless track and ensure the long-term sound condition of CRTS Ⅲ slab ballastless track.In this paper,the numerical analysis method is used to explore the stress of ballastless track under different interface damage.In addition,the interface damage index is proposed,and the specific calculation method is given.Firstly,the research status of concrete spalling theory and concrete bonding theory is summarized and analyzed,and the causes of interface damage are analyzed based on the theoretical research status and field damage.The results show that the curing conditions during construction,the filling of self-compacting concrete is not full,the warpage deformation of track slab under the action of temperature gradient,and the train load all affect the bond state of track slab and self-compacting concrete.The emergence and development of interface damage are usually the result of a variety of factors.Secondly,the effects of different position,length,width and combination of the interface damage on the stress and displacement of the track slab are calculated.The results show that under the combined load,slab end interface damage has the greatest impact on the stress and displacement of ballastless track.In practical engineering,we should pay attention to the generation of slab end interface damage,and the slab end interface damage should be found in time and repaired as soon as possible.Considering the transverse penetration of the interface damage,the transverse tensile stress of the track slab first increases and then decreases with the increase of the longitudinal length of the interface damage,and reaches the maximum value of 3.635 MPa when the longitudinal length of the interface damage is equal to 1000 mm.Considering that the longitudinal length of the interface damage is 1 m,the transverse tensile stress of the track slab first increases and then decreases with the increase of the transverse length of the interface damage,and reaches the maximum value of 3.589 MPa when the transverse width of the gap is equal to 350 mm.Therefore,in practical engineering,attention should be paid to the interface damage with width greater than 350 mm and length greater than1000 mm.Finally,the interface damage of track slab and self-compacting concrete layer is divided into 9 types.According to these 9 types of interface damage,the interface damage effect index(IEI)is proposed,and the specific calculation formula is given.The paper puts forward the evaluation standard of i interface damage effect index,adopts the "score deduction system",divides the technical grades of IEI scores into four grades,which are: ≥90 is excellent,<90and ≥80 is good,<80 and ≥60 is medium,and < 60 is poor,and gives corresponding maintenance suggestions.Delphi method(expert investigation method)is used to determine the weight coefficient of 9 kinds of interface damage,and the calculation method of interface damage effect index is applied to a specific example,and the corresponding maintenance decision scheme is given.