Test Research On Vibration Attenuationsubgrade Of Light High Strength Concrete

Fast development of urbanization leads to increasing population density while urban congestion and smog became big problems of urban development.To solve the problem,the most effective method is to develop the urban rail traffic.Subway construction has become an inevitable choice for many large and mediumsized cities.However,in operation of metro,vibration energy transmission between the wheel-rail brings new problems to the subway operation safety and the surrounding environment.Currently,the cost of vibration reduction used in the metro rail is generally expensive and the effect is ragged.Therefore,looking for a kind of obviously effective measure of vibration reduction which has high cost performance became the core of the subway vibration research.Based on the full access to data as well as conclusion and analysis of the related research,this paper seeks a kind of new light ballast material which not only meets the subway operation safety,but also can decay the vibration energy.Specific research works are carried out as follow:(1)Mixing the new type lightweight concrete were hunt for to meet the strength requirements of metro subgrade through a lot of strength tests.The impacts of silicon powder,fiber,cement label,water cement ratio,content of water reducing agent were analyzed on strength of testing blocks.By adding addictives ensures lightweight concrete workability and uniform distribution of light material in block.In the configuration process of high strength lightweight concrete,the difference of strength caused by two methods was researched that concrete or stone was replaced by expanded polystyrene particles.A suitable mixing method of mixing concrete was found.The relative formula between the high strength lightweight concrete and expanded polystyrene particles volume ratio and the damage forms of concrete with different expanded polystyrene particles content were gained which is more convenient for engineering application..(2)By means of light concrete damping ratio tests,Analysis the concrete of different expanded polystyrene content under cyclic loading,the amplitude of vibration load is respectively 40kN,50kN,60kN,and the vibration number is 50,000 and 100,000 respectively(vibration loading waveform is the sinusoidal loading).Then got the relationship among lightweight concrete hysteresis loop shape with expanded polystyrene particles content,amplitude of cyclic loading,the number of cyclic loading.Study of the relationship between the lightweight concrete damping ratio and expanded polystyrene particles contents.The influence of different expanded polystyrene particles contents on sample residual strength was analyzed and the change rule of strength as different expanded polystyrene particles content concrete being experienced by long-term cyclic loading was got.(3)Vehicle vibration system and track vibration system was built,and then a systematic vibration model was formed through nonlinear coupling between the two.The model can be used to calculate the vibration response of the vehicle system and rail system in the process of train operation,as well as the size of vibration load on the all parts of rail,which can solve the problem of vibration sources for finite element method calculation.By introducing the evaluation standard of vibration level,each effect was quantitatively analyzed of cushion stiffness and damping under rail or sleeper on the vibration response of rail and sleeper.(4)Through the establishment of three-dimensional finite element model,study factors such as grid cell size,applied damping,the selection of time step effect on the computational accuracy of the finite element model.Reasonable artificial boundary conditions were selected combining with calculation time and precision.The research on influences of various expanded polystyrene particles contents on metro subgrade inherent modal frequency was carried out.Due to the extraction of vibration energy in two sensitive points,effects of different expanded polystyrene particles content concrete metro subgrade on attenuation of vibration energy transmission were studied.