【作者】 张涛；

【导师】 高波；

【作者基本信息】 西南交通大学 ， 建筑与土木工程（专业学位）， 2018， 硕士

【摘要】 论文在调研了国内外学者进行地下结构振动台试验时对刚性模型箱的设计和应用现状后,通过自由场分析及数值计算,建立了“刚性模型箱-柔性材料-土体”相互作用的多质点质量集中模型及散射波在柔性材料中传播衰减模型,推导了刚性模型箱侧壁合理设置柔性材料参数的理论公式。并分析了各参数对模型箱边界效应的影响,以及地下结构的存在、考虑土体的非线性对柔性材料选择的影响,最后对柔性材料参数公式进行了修正和验证,得出以下几点结论:(1)刚性模型箱中施加柔性材料后,在地震波作用下,刚性模型箱、柔性材料、箱内土体便组成了一个相互作用的振动系统,最终柔性材料的设计归结于求解振动系统方程。柔性材料主要承担两个作用:一是模拟周围土体的夹持作用,使箱内土体振动同自由场中土体振动响应相同或相近;二是吸收全部或大部分模型土中产生的散射波的能量,模拟散射波向无限远传播的消散作用。(2)柔性材料的弹性模量、厚度、密度、泊松比、阻尼比均会影响模型土的地震响应和边界效应。因为各参数参数方式不同,其对边界效应的贡献不同。柔性材料的弹性模量和厚度影响最大,泊松比次之,密度和阻尼比影响较小。因此在柔性材料选择时建议以柔性材料的弹性模量和厚度为首要考虑因素,其次考虑泊松比,且宜选择与土体阻尼比相近的柔性材料。同时在柔性材料设计时应注意控制柔性材料密度避免模型土振动频率与入射波频率相同产生共振。(3)由于刚性模型箱边界对模型土的影响有一个范围,因此模型土宽高比B/H(即沿振动方向土体宽度与高度之比)是一个重要参数。研究表明,随着模型土宽高比的增大,边界对模型土的影响随着与边界距离的增大逐渐越小,若以0.5作为2-范数偏差均值的限值,当模型土宽高比B/H>3时不施加柔性材料的模型土的振动响应即可满足设计要求。但为了更好地模拟土体在自由场中的剪切变形效果,对于宽高比B/H>3的土体,依然建议施加适当的柔性材料以大幅降低刚性边界对土体变形的影响。(4)由于“刚性模型箱-柔性材料-土体”系统简化与等效,理论解与数值解是有误差的。这个误差来源于等效刚度误差,等效力误差及未考虑土体非线性误差等;为使柔性材料参数公式可用,应用数值方法对公式进行了修正,论文中理论公式的修正系数可取为1;(5)由于地下结构对地层变形具有很大的依赖性和追随性,因此对于满足动力边界且柔性材料设置合理的模型箱,地下结构及散射波的存在对模型箱边界效应影响很小,在柔性材料设计时可直接将包含地下结构的地层结构模型考虑为均质地层计算。更多还原

【Abstract】 After researching the design and application status of the rigid model box when the scholars at home and abroad conducted the shaking table test for underground structures,the interaction between the "rigid model box-flexible material-soil body" was established through free-field analysis and numerical calculation.The mass concentration model of particles and the propagation attenuation model of scattered waves in flexible materials were used to derive the theoretical formula for the rational setting of flexible material parameters on the side walls of rigid model boxes.The influence of various parameters on the boundary effect of the model box and the existence of the underground structure,the influence of the nonlinearity of the soil on the selection of the flexible material were analyzed.Finally,the parameter formula of the flexible material was revised and verified,and the following conclusions were drawn.:(1)After applying the flexible material in the rigid model box,under the action of seismic waves,the rigid model box,the flexible material,and the soil in the box form an interacting vibration system.The final design of the flexible material is attributed to solving the vibration system equation.The flexible material mainly plays two roles: one is to simulate the clamping action of the surrounding soil,so that the soil vibration in the tank is the same or similar to the vibration response of the soil in the free field;the second is to absorb the scattering wave generated in all or most of the model soil,which simulates the dissipation of waves.(2)The elastic modulus,thickness,density,Poisson’s ratio,and damping ratio of the flexible material all affect the seismic response and boundary effect of the model soil.Because of the different parameters of each parameter,its contribution to the boundary effect is different.The elastic modulus and thickness of the flexible material have the greatest effect,Poisson ratio is second,and the density and damping ratio have little effect.Therefore,when selecting flexible materials,it is recommended to use the elastic modulus and thickness of the flexible material as the primary considerations,followed by considering the Poisson’s ratio,and to select a flexible material with a similar damping ratio to the soil.At the same time,in the design of flexible materials,attention should be paid to controlling the density of the flexible material to avoid resonance of the model soil with the same frequency as the incident wave.(3)Since the boundary of the rigid model box has a range of influence on the model soil,the aspect ratio B/H of the model soil(ie,the ratio of the width and height of the soil along the vibration direction)is an important parameter.The study shows that as the aspect ratio of the model soil increases,the influence of the boundary on the model soil gradually decreases with increasing distance from the boundary.If 0.5 is used as the limit of the 2-norm deviation mean value,when the model soil is wide When the height ratio B/H>3,the vibration response of the model soil without applying the flexible material can meet the design requirements.However,in order to better simulate the shear deformation effect of soil in the free field,for the soil with aspect ratio B/H>3,it is still recommended to apply appropriate flexible materials to greatly reduce the influence of the rigid boundary on the soil deformation.(4)Due to the simplification and equivalence of the "rigid model box-flexible material-soil" system,the theoretical and numerical solutions are in error.This error is derived from the equivalent stiffness error,equivalent effectiveness error and the non-linear error of the soil.In order to make the flexible material parameter formulae available,the numerical method is used to modify the formula.The correction coefficient of the theoretical formula in the paper can be taken as 1;(5)Because the underground structure has great dependence and followability on the formation deformation,therefore for the model box that satisfies the dynamic boundary and the flexible material is set reasonably,the presence of the underground structure and the scattered wave has little effect on the boundary effect of the model box.In the design of flexible materials,the formation structure model containing underground structures can be directly considered as a homogeneous formation calculation.更多还原