【作者】 张青哲；

【导师】 戴经梁； 杨人凤；

【作者基本信息】 长安大学 ， 道路与铁道工程， 2010， 博士

【摘要】 交通量的增长及汽车荷载的增大,对公路压实质量提出了更高的要求。实践证明,对公路路基进行必要的有效压实,可以增加路基土和路面材料的不透水性和强度稳定性,增强路面的使用性能并延长路面的使用寿命。由于振动压路机比同吨位的静力压路机不仅有更好的压实效果,而且有更高的压实效率,所以,振动压路机被广泛应用于压实施工的各个领域。本文分别从动力学理论模型分析、试验研究、土压应力信号的分析与处理及有限元数值分析等方面,对土体振动压实系统的力学模型、模型参数对振动压实效果的影响规律、压应力及压实能量在土层中的分布与传递规律及土内压应力的三维分布特性进行深入研究。根据机械系统动力学理论,建立了“振动压路机—土”系统的动力学模型,对振动压实过程中的接地振压和跳振压实两种工况进行动力学分析,推导了振动轮与土体间动态作用力只的计算公式,在此基础上,分析了模型中激振频率、振幅等振动参数及土体参数对振动压实效果的影响关系。通过振动压实试验研究,以压实度为评价指标,得到了振幅、振动频率、碾压速度等压实作业参数对压实效果的影响规律为：振幅对压实度影响最大,其次是碾压速度,振动频率对压实度的影响不如振幅和碾压速度明显,但存在最佳振动频率。结合所建立的动力学模型,对土体刚度和阻尼进行动态识别,结果表明：土体刚度随土体不断趋于密实状态逐渐增大,土体阻尼随土体不断趋于密实状态逐渐减小；振动压实系统的固有频率和振动轮加速度随着土体刚度的增加逐渐增大,但增幅越来越小。土压应力信号包含了振动压实物理过程的重要信息。通过对土压应力信号的时频域分析,研究了压应力在土体各层的分布情况以及压实能量在土内的吸收状况与传递规律。由于试验中采集的土压应力信号是一个含噪的非平稳瞬态突变信号。为了从含噪信号中提取理想的压应力信号,分析信号的联合时频特性,对信号去噪方法进行了对比研究,提出了基于小波变换去噪和奇异值检测的土体振动压实压应力信号分析方法。计算出压应力从出现到达峰值的历经时间和压应力在土中作用时间,以此研究名义振幅、振动频率和碾压速度等压实作业参数对土基振动压实效果的影响关系。结果表明：压应力在各层土体内的作用时间与振幅基本上呈线性增长关系,与碾压速度呈下降关系,但碾压速度越高,其降低趋势变缓,与振动频率呈先增长后下降的关系,即存在最佳振动频率。综合压实度测试结果和土压应力信号的小波变换去噪与奇异值检测结果,得到最佳的振动压实作业参数为：振幅1.6mm,振动频率30Hz到32Hz之间,碾压速度1.12km/h-1.30km/h之间。为了研究振动压实作用下土中压应力的三维分布特性,将振动压实系统的动力学理论模型与有限元方法相结合,首次建立了土体振动压实系统的三维数学物理模型,并利用有限元方法对土体振动压实过程进行仿真。仿真结果显示：激振力在任一瞬时的作用区域内,土内应力场分布基本一致,在轮宽方向,压应力分布不均匀,而在压实深度方向,压应力具有递减性。本文工作将理论分析、试验研究和有限元仿真有机结合,为优化土体振动压实作业参数、提高压实效果和效率、揭示土的振动压实机理提供理论依据,并对现场压实具有重要的工程指导意义。更多还原

【Abstract】 With the increase of the traffic and vehicle load, the requirement for the compaction quality of highway is improved. The experiments show that if the necessary compaction is carried out on the highway subgrade, the non-permeability and strength stability of the subgrade soil and pavement material can be increased. The utility performance can be strengthened and the life of the pavement can be lengthened. For the vibration roller is superior to the same weight static roller in that good compaction quality and compaction efficiency, the vibration roller is widely applied in the compaction construction field.From the dynamic theory model analysis, experimental study, the analysis and treatment of the stress signals of the soil compaction and the finite element numerical analysis, the studies are carried out on the dynamic model of the soil vibration compaction system, the effect of the model parameters on the compaction quality, and the three-dimensional distribution and transmit of the stress and compaction energies in the soil, and the distribution characteristics of soil internal stress in deep.According to the dynamic theory of mechanical system, the "vibration roller-soil" models are presented. The dynamic analysis is carried out on two work conditions of near ground compaction and jump ground compaction during the vibration compaction. The calculation equation Fs of the dynamic force between the vibration wheel and the soil is derived. Based on the equation, the relation between the vibration parameters and the soil parameters, as for vibration frequency and vibration amplitude, and the compaction quality is analyzed.Through the vibration compaction experiments, based on the evaluation index of compactness, the law between the work parameters, such as the amplitude, vibration frequency and roller compaction velocity and the compaction quality is gotten. The effect of amplitude on the compactness is the most. The second is the compaction velocity. The effect of vibration frequency on the compactness is not obvious as that both the amplitude and compaction velocity. But the optimal frequency exists. Combing the established dynamic model, the soil stiffness and dampness are identified. The experiments showed that the soil stiffness increased with the dense of the soil. The soil dampness decreased with the dense of the soil. The more the soil stiffness is, the more the natural frequency of the vibration system and the acceleration of the vibration wheel. However the increase domain becomes small.The stress signals of the soil compaction are rich in the important information during the vibration physical progress. Through the time domain analysis on the soil stress signals, the distribution of the compressive stress in the soil and the absorption status and the transmit law of the compaction energy in the soil.The stress signal is unstable and transient salutation signals accompanied by strong noise, which are acquired from the soil by the experiments. To extract the ideal signal from the noise signals and study the joint time-frequency property of the soil stress signal during vibrating compaction, the wavelet transform method for de-noising and the singular value identification method are proposed. The time of the stress appearance and the time of the stress peak arrival can be calculated, further the function time. So the relation between the work parameters, such as the amplitude, vibration frequency and the rolling velocity, and the vibration rolling effect can be analyzed. The results show that the function time of stress on the soil is increased linearly to the amplitude, which decreased with the increase of the rolling velocity. However the high the rolling velocity is, the slower the decrease tendency is. The function time increase with the vibration frequency first then decrease. So the optimal vibration frequency exits.Combining the compactness test and the wavelet transformation and singular value detect of the soil stress signal, the optimal compaction parameters are that the amplitude is 1.6 mm, the vibrating frequency is 30-32 Hz and the roller compaction velocity is 1.12km/h～1.30km/h.To study the three dimensional distribution of the compact stress of the soil under the vibration compaction, the dynamic theoretical model is combined with the finite element method. The three-dimensional mathematic and dynamic model of the soil vibration compaction system is proposed for the first time. By the finite element method, the simulations of the vibration compaction of the soil are carried out. The simulated results showed that the distribution of the soil internal stress is uniform for the instantaneous region of the exciting force. Along the wheel width, the compact stress is not uniform. Along the compaction depth direction, the compact stress decreased little by little.This dissertation combined the theoretical analysis, experimental study and finite element simulation, which pave for the parameter optimization of the soil compaction, the improvement of the compaction quality and efficiency and discovering the compaction mechanism of the soil. The study is of importance in guiding the infield engineering construction of compaction.更多还原