【作者】 林宇亮；

【导师】 杨果林；

【作者基本信息】 中南大学 ， 道路与铁道工程， 2011， 博士

【摘要】 以无砟轨道单线铁路路堤为原型,设计和完成了4种压实度和2种加筋形式路堤结构的大型振动台模型试验,并建立了路堤数值模型,完成了振动台试验主要工况的模拟；开展了加筋格宾挡墙、绿色加筋格宾挡墙、柔性网面土工格栅挡墙等新型加筋土结构的力学特性和抗震动力特性的一系列室内试验研究；采用水平层分析法对现行抗震规范中用于地震动土压力计算的Mononobe-Okabe公式进行了拓展和补充。主要研究工作如下：(1)完成了4种压实度(95%、93%、90%和87%)和2种加筋形式(加筋2层和加筋4层)路堤结构的振动台模型试验设计。根据相似原理,推导了路堤振动台试验相似关系,确定了模型试验的模拟材料,开展了填料的大型三轴试验及其他常规土工试验,得到了填料的主要物理力学性能指标。(2)以95%压实度路堤振动台试验成果为例,分析了路堤动力特性参数变化规律及其影响因素。研究了不同地震波和不同地震动强度激励下的路堤水平加速度响应、垂直加速度响应、动土压力响应、动位移响应等内容,并分析了地震动类型、地震动强度、多向输入、时间压缩比等因素对水平和垂直加速度放大倍数的影响。同时结合路堤动力特性试验结果,从时域和频域的角度分析了地震波在路堤中的传播特性。测试了震陷变形和侧向残余变形,得出了震陷变形和侧向残余变形的分布特点。并通过FLAC3D建立了振动台试验的数值模型,模拟了振动台试验主要加载工况,数值模拟结果可作为试验结果的补充和验证。(3)完成了压实度为95%、91%、87%和83%以及加筋2层和加筋4层路堤的振动台模型试验。得到了不同压实度和不同加筋形式路堤动力特性参数,分析了路堤动力特性的变化规律及其影响因素。对比和分析了不同压实度和不同加筋形式路堤水平和垂直加速度放大倍数分布的差异性及其影响因素、动土压力响应特性、动位移响应特性,以及路堤震陷变形和侧向残余变形的分布特点,并研究了压实度、加筋形式等因素对残余变形的影响。通过FLAC3D建立了不同压实度和不同加筋形式路堤的数值模型,模拟了振动台试验主要加载工况,并将数值模拟结果同试验结果进行了对比分析。(4)通过拉伸试验研究和对比了不同加筋土筋材的拉伸力学特性。以红砂岩为填料,开展了格宾网和土工格栅的界面摩擦特性拉拔试验研究。通过在挡墙顶部施加不同荷载水平的循环加卸载,研究了加筋格宾挡墙、绿色加筋格宾挡墙、柔性网面土工格栅挡墙等3种新型加筋土结构的承载力特性。通过施加不同幅值和频率的动力荷载,研究了这3种新型加筋土结构的动变形特性。通过施加不同类型和不同强度的水平地震动激励,研究了这3种新型加筋土结构的抗震动力特性。研究表明,新型加筋土结构有优良的构造措施,且为柔性结构,当遭遇强烈地震时能消耗大量地震能量,具备良好的变形特性。(5)基于Mononobe-Okabe的破裂面假设,采用水平层分析法推导了地震作用下主动和被动土压力合力及其作用点位置、土压力强度分布情况的解析解,采用图解法得到了主动和被动土压力临界破裂角的显式解答。提出了求解主动土压力裂缝深度的迭代计算方法。推导的主动和被动土压力公式考虑了水平地震系数、垂直地震系数、墙背倾角、填料粘聚力和内摩擦角、填料与墙背的粘结力和外摩擦角、均布超载等诸多因素的影响,并对这些影响因素作了参数分析。通过与已有的主动和被动土压力公式比较表明,在相应的简化条件下,动土压力公式与已有土压力公式是完全一致的；并结合算例,证实了公式的可靠性和有效性。(6)根据所推导的地震条件下主动和被动土压力公式,基于Visual Basic 6.0开发了地震动土压力计算程序。更多还原

【Abstract】 Based on the prototype of single-line unballasted track railway embankment, shaking table model tests of 4 types of compaction embankments and 2 patterns of reinforced embankments were designed and carried out. Numerical models of embankments were established and the main shaking table test conditions were simulated. A series of laboratory tests on mechanical properties and seismic behaviors of new patterns of reinforced earth structures including reinforced gabion retaining wall, green reinforced gabion retaining wall, and geogrid reinforced earth retaining wall of flexible wall face were widely carried out. Horizontal slices analysis method was adopted to deduce seismic earth pressure formulas to compensate the shortcomings of Mononobe-Okabe formula which was widely used in current seismic codes. The main researches can be concluded as follows:(1) Shaking table model tests of embankments with compactions of 95%,93%,90% and 87%, and reinforced embankments with 2-layer or 4-layer reinforcements were designed. According to similarity theory, the similarity relations of main physical quantities for shaking table model tests were deduced, and simulation materials were selected. Large-scale triaxial tests and other routine soil tests were carried out and the main physical and mechanical properties of filler were obtained.(2) Taking the shaking table test results of embankment with compaction of 95% as example, dynamic characteristics of embankment and their influencing factors were analyzed. The behaviors of horizontal acceleration response, vertical acceleration response, seismic earth pressure response, and dynamic displacement response under different intense excitations of different seismic waves were studied. The factors which influenced horizontal and vertical acceleration magnification were analyzed including the types of seismic waves, the intensity of excitation, multi-directional input, time compression ratio, etc. Combined with the dynamic characteristics of embankment, seismic wave propagation characteristics were studied by time domain analysis and frequency domain analysis. Seismic settlement and lateral residual deformation of embankment were measured, and the distributions of residual deformation were obtained. Numerical model was established by FLAC3D based on shaking table test model, and the major loading conditions of shaking table test were simulated. Numerical simulation results could be taken as a supplement or verification for shaking table test.(3) Shaking table model tests of embankments with compactions of 95%,93%,90% and 87%, and reinforced embankments with 2-layer or 4-layer reinforcements were carried out. Dynamic parameters of different types of compaction embankments and different patterns of reinforced embankments were obtained, and the dynamic characteristics and their influencing factors were analyzed and compared. The differences of horizontal and vertical acceleration magnification distribution among different types of compaction embankments and different patterns of reinforced embankments were analyzed. The behaviors of the dynamic earth pressure response, dynamic displacement response, seismic settlement and lateral residual deformation of different types of compaction embankments and different patterns of reinforced embankments were compared. And the influencing factors such as the compaction of filler, the reinforced forms of embankments were analyzed. Meanwhile, numerical models were established by FLAC3D based on shaking table test models of different types compaction embankments and different patterns of reinforced embankments, and the major loading conditions of shaking table test were simulated. Numerical simulation results were compared with shaking table model test results.(4) Tensile mechanical properties of different reinforcements were studied and compared according to the tensile tests. With red sandstone as filler, pull out tests of gabion meshes and geogrid were carried out. By applying cyclic loading and unloading of different magnitudes at the top of retaining wall, bearing capacity behaviors of reinforced gabion retaining wall, green reinforced gabion retaining wall and geogrid reinforced earth retaining wall of flexible wall face were studied. By applying dynamic load of different amplitudes and frequencies, dynamic deformation behaviors of these three new patterns of reinforced earth structures were studied. By applying different intense horizontal excitations of different seismic waves, the seismic behaviors of new patterns of reinforced earth structures were studied. Test results showed that the new patterns of reinforced earth structures, as flexible structures with excellent structural measures, could consume lots of seismic energy and presented good deformation behaviors even under strong seismic excitations.(5) Based on planar rupture surface assumption of Mononobe-Okabe theory, horizontal slices analysis method was adopted to deduce analytical formulas of resultant force of active and passive earth pressure, application position of resultant force and distribution of seismic earth pressure. The explicit solutions of critical rupture angles both for active and passive earth pressure were obtained by graphic method. And iterative method for crack depth calculation of active earth pressure was proposed. The influencing factors were considered in formulas such as horizontal and vertical seismic acceleration, batter angle of wall back, cohesion and internal friction of filler, cohesive force and external friction angle between filler and the back of retaining wall, equispaced overloading, etc. And parameters analysis was made on these factors. It was shown that the formulas were the same as the existing active and passive earth pressure formulas under corresponding simplified assumptions. The formulas were also proved reliable and valid by examples.(6) According to the active and passive earth pressure formulas under seismic condition deduced by horizontal sliced analysis method, calculation program was designed by Visual Basic 6.0.更多还原