高铁运行引起的三相路基振动和屏障隔振研究

Ground vibration caused by the moving high-speed trains (HST) frequently annoys the living and working of adjacent residents, and affects the normal operation of precision instruments. Current studies on HST induced vibration are mainly focused on single-phase and two-phase saturated media. The researches show that gas in soils has obvious significance on the wave propagation and ground vibration under a fixed load, while the study on three-phase subgrade (quasi saturated and unsaturated subgrade) under a moving load, which is more practical, is rarely reported. Based on dynamic triaxial test and 2.5 dimensional finite element method of three-phase soil, this research intends to establish a train-track-three phase subgrade (including homogeneous, layered and transversely isotropic) coupled dynamic model. Combining the established model with vibration isolation model, HST induced ground vibration, vibration propagation and attenuation and screening mechanism of the ground barriers in three-phase subgrade will be studied. The effects of soil parameters including gas phase and its contents, vehicle speed and track irregularity on vibration characteristics of three-phase subgrade will be analyzed. By the contrast analysis of field measurements and theoretical calculations, a new method on the basis of energy distribution will be proposed to evaluate the three-phase subgrade vibration attenuation caused by high-speed trains. The screening effectiveness of ground barriers will also be analyzed and compared by setting up the different vibration isolation techniques on the three-phase subgrade model, and the design method of ground barriers suited for the three-phase subgrade will be proposed. The research results will provide theoretical guidance and technical supports for the evaluation and control of HST induced ground vibration in three-phase subgrade, and meanwhile enrich the knowledge of the fundamental theories in engineering geology and soil dynamics, etc.

高铁运行引起的地面环境振动时常干扰周边人们的生活、工作和精密仪器正常使用。目前高铁引起路基振动研究多限于单相弹性及两相饱和介质，研究表明固定荷载下土中气体相对波的传播和振动影响显著，而移动荷载下三相准饱和及非饱和土路基振动成果鲜有报道。本课题拟通过三相土动三轴试验和三相路基2.5维有限元方法，建立列车-轨道-三相路基（均质、分层、横观各向同性）耦合计算模型，结合屏障隔振模型并通过开发计算程序，研究高铁运行引起的三相路基振动、地面振动传播衰减和屏障隔振机理。分析土中气相及含气量等土参数、车速、轨道不平顺对三相路基地面振动特性的影响；结合现场振动实测与理论分析，基于能量分配角度提出高铁运行引起的三相路基地面振动衰减评价方法；研究三相路基地基屏障隔振效果，提出三相路基的屏障隔振设计方法。本研究将完善工程地质学、土动力学等理论，为高铁运行引起的三相路基振动评价和防治对策提供理论依据和技术保障。

高速列车运行引起的地面环境振动问题备受关注。自然界中土多处于非饱和状态，存在的孔隙气体对土中波的传播影响显著，而三相路基的振动研究严重不足。本课题通过理论推导，得到了横观各向同性饱和、准饱和与非饱和路基振动的2.5维有限元控制方程，建立列车-轨道-路基的动力模型，编制Fortran计算程序研究路基的振动特性。建立了桩网复合路基三维有限元计算模型，研究车速和桩网设计参数对复合路基振动的影响。基于桩网复合路基土工离心机模型试验研究了复合路基的破坏机理。提出了弹塑性路基振动与变形的2.5维有限元计算方法。研究了地震和列车荷载共同作用下的路基变形。结果表明：横观各向同性饱和土体竖向弹性模量对地面振动的影响大于水平向，泊松比对孔隙水压力的影响较大，剪切模量的影响可忽略。土体饱和度减小引起路基振动增大，超孔隙水压力减小；车速达到土体瑞利波速时，路基振动与超孔隙水压力骤然增大，近轨道处振动由共振决定，距轨道远处振动由车速决定。桩网复合路基自身减振效果显著，增加路堤高度、加筋体层数、桩体模量、桩径和减小桩间距可有效减小地面振动；土体阻尼比越大，振动衰减越快。桩网复合路基嵌岩桩的潜在破坏模式主要为弯拉破坏，斜坡桩的潜在破坏模式为弯剪或倾倒破坏，摩擦桩的潜在破坏模式为倾倒及横移破坏；斜桩的加固效果显著。减小波阻板埋深和增加波阻板厚度可提高隔振效果，上软下硬地基中波阻板的隔振效果优于上硬下软地基；增大填充沟深度可有效减小沟后地面振动；适当增加建筑物筏板厚度和埋深可有效减小建筑结构振动。地震与列车共同作用下，路基和轨道的位移主要受地震作用影响；从安全性考虑，提出把钢轨脱轨系数和轨道结构横向位移共同作为列车脱轨评判指标。本研究将完善工程地质学、土动力学等理论，为高铁运行引起的三相路基和桩网复合路基振动评价和防治对策提供理论依据和技术保障。