| With the construction of high-speed railway in seasonal frozen area,the of uneven frost heave of subgrade has become a major technical problem to be solved urgently.The subgrade frost heave will lead to irregularity and interlayer seams of slab track,which will directly affect train running quality and safety and the service performance of the structures.It is a key factor for speed limit of high-speed railway in winter in severe cold areas.In the existing studies,there are many studies on the mechanism and control measures of subgrade frost heave,and the research on the mechanical behaviors of slab track under subgrade frost heave are relatively scarce.Therefore,it is very important to carry out a series of studies related to slab track irregularity and vehicle dynamic characteristics caused by subgrade frost heave,which can provide theoretical reference for the design theory and maintenance methods of high-speed railway in cold regions.In this paper,CRTS? slab track was taken as the research object,and a vehicle-slab track-subgrade spatial static and dynamic coupling model considering the influence of concrete plasticity and steel bars was established.The mapping relationship between frost heave deformation and track irregularity,the distribution and development law of seams between layers of slab track under frost heave,and the influence of frost heave on dynamic response of vehicle-track system were analyzed.The criteria and prediction diagnosis of subgrade deformation in frost heave area were also studied.The main research results and conclusions were as follows:(1)Thermodynamic model of high-speed railway subgrade was established,and the space-time deformation characteristics of subgrade in frost heave area were studied.A convex cosine curve was proposed to simulate the uneven frost heave of subgrade.Based on the finite element method and the plastic constitutive theory of concrete,the necessity of using concrete plasticity and steel bars in slab track was revealed.In addition,the analysis shows that the influence of different frost heave location,capacity and wavelength on the amplitude transfer ratio was small,and the influence of short wave on the wavelength transfer ratio was large;the yinyang slope effect would cause lateral irregularity and increase the rail irregularity;the uniform multi-wave frost heave had little effect on the rail irregularity change rate,and it would decrease under the non-uniform multi-wave frost heave.(2)Based on the established spatial coupling static model of slab track,the seams distribution and development law of slab track under different frost heave conditions were studied.The results show that when frost heave acted in the middle of the track slab,the seams length between layers reached the maximum value;with the increase of frost heave capacity,the seams height and length increased gradually;with the increase of frost heave wavelength,the seams height and length decreased gradually.The temperature rising of the whole structure,positive and negative temperature gradient loads combined with frost heave effects would increase the seams length between self-compacting and base plate,and the seams height would increase with temperature rising and dropping of the whole structure,and negative temperature gradient combined with frost heave effects.The seams between the base plate and the surface of the subgrade extended gradually from the middle to both sides in the transverse position,and developed rapidly.When the cohesional strength reached 1.0MPa,there was almost no seams.(3)The spatial coupling dynamic model of vehicle-slab track-frost heave subgrade was established,and the effects of different frost heave and operating conditions on vehicle dynamics indexs in cold regions were analyzed.It was found that wheel load reduction rate was more sensitive to frost heave wavelength,while vertical acceleration of the carbody was more sensitive to the frost heave capacity.It is necessary to pay more attention to the frost heave section with the amplitude greater than 15mm and the wavelength less than 15m.With the stochastic slab track irregularity,the wheel load reduction rate was increased greatly,while the vertical wheel/rail force,acceleration of the carbody and sperling index changed less.Under the condition of subgrade thaw settlement,the variation trend of the wheel/rail forces and the acceleration of the carbody in the time history was opposite to that under the condition of subgrade frost heave.Additionally,the subgrade thaw settlement exerted a minor influence on the vehicle dynamic characteristics because of the small amplitude in the frost heave region.With the increase of the train speed,the dynamic indexes of the vehicle would increase.The wheel load reduction rate increased most,and the impact on the wheel/rail vertical force was minimal.The temporary speed limit in the subgrade frost heave areas can effectively ensure the safety and comfort of the high-speed railway.(4)Based on the static control index of seam between the base plate and self-compacting,the dynamic control index based on the comprehensive influence of wheel load reduction rate and vertical acceleration of the carbody,the control standard of subgrade frost heave combined with static and dynamic was put forward.The RBF neural network model was used to realize the preliminary identification of frost heave wavelength and amplitude of subgrade,and the relationship between frost heave waveform and vertical wheel/rail force was established through functional relationship.Finally,an intelligent diagnostic device for subgrade deformation in frost heave area was put forward,and a vehicle acceleration data acquisition module was made,which provides a theoretical reference for the maintenance method of high-speed railway in cold areas. |
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