砂土地基在刚性基础作用下土体变形特性的试验研究

发布时间：2018-04-17 09:22

本文选题：静载试验 + 刚性基础　；参考：《西南交通大学》2017年硕士论文

【摘要】：随着我国基础设施建设的蓬勃发展,各种建筑物拔地而起,然而所有的建筑的安全建设与运营都离不开稳固的地基,因此地基土的变形特性是一个重要的研究内容。本文依托"中国铁路总公司科技研究开发计划课题"《超深大截面沉井基础设计理论及关键技术研究》,通过室内模型静载试验为主,数值模拟为辅的研究方法,设计制作了试验槽和3个不同尺寸的混凝土模型及对应的刚性底板,开展了 5组不同基础宽度和不同埋深条件下的静载试验,通过位移计和土压力传感器监测整个试验加载过程中基础沉降数据和土中附加应力数据,对砂土地基在不同基础宽度、不同埋深刚性基础作用下,地基土的破坏过程,加载过程中的基底应力分布及变化规律,土中的应力分布及变化规律,加载至破坏后卸载回弹变形规律以及重复加载时土体承载特性进行研究。得到以下结论:(1)通过静载试验和数值模拟计算发现,砂土地基的破坏具有明显渐进破坏特征。基底应力随着地基土的渐进破坏出现显著的重分布。在荷载施加初期,基底应力分布均为均匀增长;随着加载过程的进行,当荷载增加到比例界限时,5组试验均出现了基底边缘应力不再因荷载增加而上升,说明基底边缘土体发生破坏,失去承载能力,随着荷载的继续增加到极限荷载,基底应力峰值由基础外围向基础中心移动,说明破坏范围逐渐增大,此时承载力主要由基础中心附近土体提供。(2)在加载初期,土中的竖向附加应力基本成均匀增长;当各组试验加载到比例界限时,由于基底边缘土体破坏,基底实际发挥承载能力土体的面积减小,基础中心下方土体的竖向附加应力大幅高于基底边缘位置土体,距基底较远的土体规律相似,但变化幅度不如基底附近土体。(3)在加载初期,土中的水平附加应力基本成均匀增长,土中水平应力的峰值最先在上部出现,随着荷载的增加逐渐向下移动,加载到极限荷载时,基础边缘位置下方土中的水平附加应力峰值出现在基底以下1倍基础宽度的位置;基础边缘向外0.5倍基础宽度位置下方土中的水平附加应力峰值出现在基底以下1.5倍基础宽度的位置。(4)根据土中竖向附加应力图分析计算可得,试验条件下,基底竖向附加应力扩散角θ为18.4°026.6°,与《建筑地基基础设计规范》(GB50007-2011)规定相符。(5)5组试验所得卸载回弹曲线非常平缓,总体回弹量在10mm左右且大部分回弹变形发生在卸载的最后阶段。基础宽度和埋深对地基回弹变形有影响,对比不同基础宽度时发现,在卸荷比相同时,基础宽度越大回弹量越小;对比不同埋深时发现,卸荷比相同时,零埋深组的回弹量小于两组有埋深组,但0.5倍基础宽度埋深和1倍基础宽度埋深卸载回弹规律基本相同。(6)重复加载时发现,地基在发生整体破坏之后依然具有承载能力,且承载能力较初次加载时有大幅度提高,土的压缩模量比初次加载时提高了 1.84～2.25倍,基础宽度和埋深对地基土压缩模量有影响,不同基础宽度的对比分析中可知,随着基础宽度的增加,压缩模量比逐渐增大,且基本呈线性增长;不同埋深的对比分析中可知,随着基础埋深的增加,压缩模量比逐渐增大,且呈非线性增长,基础埋深越大,压缩模量比增长越快。
[Abstract]:With the rapid development of our country's infrastructure construction, various buildings have sprung up, but the safety of construction and operation of all buildings all cannot do without a solid foundation, so the deformation characteristics of the foundation soil is an important research topic. This paper is based on China railway company of science and technology research and development program "< ultra deep caisson section the basic design theory and key technology research", the static load test with the indoor model, numerical simulation, research methods, design of rigid plate test groove and 3 different sizes and the corresponding concrete model, carry out the static load test of 5 groups of different base width and different depth conditions, through the data and additional stress in soil foundation settlement monitoring data displacement meter and soil pressure sensor test whole loading process of sand foundation in different base width, different depth of rigid foundation. Next, the failure process of foundation soil, substrate loading process of stress distribution and variation of soil stress distribution and variation of load to the unloading deformation and damage after repeated loading when the soil bearing was investigated. Get the following conclusions: (1) through static load tests and numerical simulation calculation the destruction, sandy soil has obvious characteristics of progressive failure. The base stress of foundation soil with progressive failure appeared significant redistribution. In the early days of the applied load, the stress distribution is uniform basal growth; with the loading process, when the load increased to proportional limit, 5 groups were the basal edge stress no longer due to the load increased, indicating the substrate edge soil damage, loss of bearing capacity, continue to increase with the load to the limit load, the stress of the base peak by the basic foundation of the periphery to the center, said The damage range increases, the bearing capacity of foundation soil is mainly provided by near the center. (2) in the early stage of loading, vertical additional stress in soil basically uniform growth; when the load test were proportional to the limit, due to the destruction of the edges of the foundation soil, the actual use of the bearing capacity of soil basal area decreased, vertical base center the soil under the additional stress is significantly higher than the basal edge position of soil, soil from the base rules far similar, but the change range is less than the soil near the base. (3) in the early stage of loading, the soil level of additional stress of the soil into a uniform growth peak in the horizontal stress in the upper part of the first, with the load the increase gradually moving down, loaded into the ultimate load, foundation soil in the edge position below the level of additional stress peak in the basement below 1 times the width of foundation base edge position; outward 0.5 times the foundation The width of soil in the position below the level of additional stress peak in the basement below 1.5 times the width of the foundation position. (4) according to the analysis of additional stress can be calculated from vertical soil, under the condition of test, the basal vertical additional stress diffusion angle theta is 18.4 degrees 26.6 degrees, and < > (code for design of building foundation GB50007-2011) conformity. (5) 5 groups of tests of the unloading curve is very flat, the overall springback at around 10mm and most of springback deformation in the final stages of unloading. The foundation width and depth of influence on the deformation of foundation rebound, compared different base width, the unloading ratio is the same, the greater the width of foundation springback is smaller; comparison of different depth when the unloading ratio is the same, the springback zero depth group less than two group depth group, but 0.5 times the width of the foundation depth and 1 times the width of the foundation depth unloading rule base (6) repeat the same. When loading, the bearing capacity of foundation in the overall destruction is still, and the bearing capacity of a first load is greatly increased, the compression modulus of the soil than the initial load is increased by 1.84 to 2.25 times, the base width and the depth of the foundation soil compression modulus influence, unknown compared with the width of the foundation of with the increase of the width of the foundation, the compression modulus ratio increases gradually, and the linear growth; the comparative analysis of different depth, with the depth increasing, the ratio of compression modulus increases gradually, and nonlinear growth, the foundation depth greater than the compression modulus of the faster growth.

【学位授予单位】：西南交通大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TU470

【参考文献】