| With the increase of high-speed railway mileage in China,high-speed railway trains travel faster and faster.Therefore,there are more strict requirements for the compaction quality and standard of high-speed railway subgrade.How to detect the compaction quality of filler quickly and effectively in the filling process of high-speed railway subgrade has become a research difficulty and faces many challenges.It is mainly reflected in the following three aspects: 1)in the process of subgrade filling,the compaction quality inspection index specified in the current specification is mainly single point sampling inspection,which is not representative.2)There are many human interference factors in the rolling process of vibratory roller,and the compaction quality of high-speed railway subgrade is closely related to the vibration frequency,driving speed,rolling conditions and other factors of vibratory roller,so the compaction quality in different areas is quite different.3)There are many kinds of continuous detection indicators of compaction quality,and these continuous detection indicators are greatly affected by the vibratory roller itself,and the model and working condition of the vibratory roller are not considered.Therefore,the continuous compaction index is discrete,which is difficult to be applied in practical engineering.This paper studies the distribution and attenuation law of peak acceleration and vibration energy through laboratory test,field test and finite element numerical simulation analysis,and obtains the high energy and high attenuation area in the process of vibration rolling.The acceleration measurement points are arranged in the high-energy and high attenuation area,the characteristic wave in the process of subgrade compaction is extracted through vibration wave decomposition,and a nondestructive direct detection index based on vibration wave velocity is proposed.A large-scale full-scale indoor model test was carried out to verify the correlation between the detection index of vibration wave velocity and filler density.The research work of this paper mainly includes the following parts:(1)The vibration response of the surface vibration compaction test to the vibration of the exciter and the filler in the compaction process shows that there is an obvious decoupling phenomenon between the exciter and the filler in the surface vibration compaction process,and this decoupling phenomenon becomes more and more obvious with the increase of vibration frequency;When the displacement of exciting head increases with the increase of compaction time and the displacement of filler decreases with the increase of compaction time,the vibration condition is conducive to vibration compaction;Because the compacted barrel wall has obvious reflection effect on the vibration signal,the vibration signal has obvious frequency band widening phenomenon;The total energy of the vibration signal of the exciting head in unit time increases with the increase of compaction time,while the total energy in the filler decreases with the increase of compaction time.(2)The field test is carried out to explore the dynamic response characteristics of the horizontal direction of the vibration wave on the subgrade surface,and it is obtained that the acceleration amplitude and energy of the filler in the subgrade decrease significantly with the increase of the rolling speed of the vibratory roller;The vibration frequency does not change during the propagation of the vibration wave,and the amplitude of the fundamental wave decreases obviously with the increase of the propagation distance of the vibration wave;During the rolling process of vibratory roller,with the increase of subgrade horizontal distance,the energy attenuation rate of vibratory roller shows the trend of first fast and then slow,and the micro energy is stably transmitted at 4-6m.(3)The finite element numerical simulation model of vibratory roller filler coupling is established,and the propagation laws of vibration waves in the subgrade along the horizontal,vertical and three-dimensional directions during the compaction process are studied.In the propagation process of vibration waves in the virtual paving layer and underlying layer,the peak acceleration attenuation of vibration waves in the propagation process is first fast and then slow;In the process of vibration wave propagation,the amplitude attenuation of vibration wave acceleration in horizontal and vertical directions is an exponential function;In the process of vibratory compaction,the vibration wave decays in the shape of jujube core in the three-dimensional direction,and the theoretical attenuation model of vibration wave acceleration and energy is proposed according to its attenuation curve.(4)A large-scale full-scale test model of indoor vibratory roller filler coupling is established,and the decomposition of subgrade surface vibration wave is carried out.It is found that a single signal wave is similar to the original signal in time and frequency domain,and its signal frequency is the fundamental frequency with the most obvious spectral characteristics of the original signal,while other components do not have this law,and there is only one single signal component with triangular fractal characteristics.This single signal wave is called subgrade compaction characteristic wave;The acceleration measuring points are arranged in the high-energy and low attenuation area of the subgrade surface,the characteristic wave of subgrade compaction is extracted,and the characteristic wave velocity is obtained according to the phase difference between adjacent measuring points;Carry out the calculation and verification of characteristic wave velocity,and prove that the wave velocity calculation method proposed in this paper has strong reliability;The correlation between characteristic wave velocity and filler dry density is established,and it is verified that there is a strong correlation between characteristic wave velocity and subgrade surface filler density. |
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