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类型 基础研究 预答辩日期 2018-03-12
开始(开题)日期 2015-09-14 论文结束日期 2018-01-15
地点 九龙湖校区交通楼323室 论文选题来源 973、863项目     论文字数 9.8 (万字)
题目 基于融沉变形的青藏高原多年冻土区高速公路路面结构优化研究
主题词 多年冻土,高等级公路,宽幅路基,融沉变形,路面优化设计
摘要 青藏高原多年冻土区修建高速公路后,由于使用宽幅路基,总吸热面积和总体积热容均会大幅增加,导致融沉效应的加剧,严重影响着路面结构的使用寿命。针对多年冻土区宽幅路基融沉变形造成的路面结构开裂问题,本文利用有限元法模拟宽幅路基的温度场、融沉变形的变化规律,从路基路面一体化角度分析路基融沉对路面结构的损伤行为和损伤演化过程,并从路面材料和结构的角度对多年冻土地区高速公路路面结构进行优化。文章主要包括以下几个方面的内容: (1) 通过分析多年冻土区宽幅路基的特点,提出温度场分析的基本方程、计算参数、边界条件以及初始条件等,并以有限元理论为基础,利用ABAQUS及其二次开发平台建立了基于第二类、第三类温度边界条件下多年冻土区的温度场有限元计算模型,利用该模型对宽幅路基温度场进行研究,评价窄幅路基现有的降温措施对宽幅路基的适用性。结果表明,多年冻土区高等级公路的宽幅路基与低等级公路的窄幅路基相比,具有更快的升温速度、较差的热稳定性,并且对下伏天然冻土的热扰动更大。多年冻土区公路由窄幅路基变为宽幅路基时,不仅会导致多年冻土上限下移,还会造成冻土融化的不均匀性加剧。与其它三类宽幅路基相比,采用了EPS隔热层以及碎石层的复合路基考察点温度最低,温度升高幅度最小,热稳定性最好。 (2) 通过对冻土本构力学模型进行研究,选取EP本构模型来模拟冻土本构,并通过编写UMAT子程序使其在ABAQUS中实现,进而以宽幅路基温度场计算结果为基础,采用顺序耦合法,建立水热力三场耦合融沉变形有限元计算模型,分析多年冻土区宽幅路基融沉变形的变化规律。结果显示,随着时间的增加路基中心线处和左侧边坡位置处融沉变形均呈线性增加,且路基中心线处增加的更快。路基宽度由10m依次增加到18m、26m、34m、42m、50m时,横向融沉曲线逐渐由二次曲线向“盆状”曲线过渡。路基高度每增加1m,路基顶部融沉变形平均增加7.1cm。对于不同高度路基,随着路基宽度的增加,差异融沉变形均是先增加后减小,且最大差异沉降对应的宽度均在18m~26m之间。现有的多年冻土区路基降温措施虽然可以提高路基的热稳定性,但是会增加路基的不均匀融沉变形。因此,有必要研发新的多年冻土区路基降温措施,使其不仅可以降低路基(特别是宽幅路基)的温度,还能减小温度分布的不均匀性对路面结构的不利影响。 (3) 在路基温度场有限元模型和融沉变形有限元模型的基础上,结合损伤力学的基本理论,建立了考虑融沉效应的路面结构疲劳损伤模型,进而分析了路基融沉变形以及车辆荷载作用下路面结构的损伤行为和损伤演化过程,并研究了融沉效应对沥青路面各设计指标的影响。结果表明,车辆荷载与融沉变形附加应力的耦合作用使路面结构损伤度急剧增加,远大于车辆荷载或者融沉变形单独作用下路面结构的损伤。对于多年冻土区路面结构,在早期车辆荷载对路面结构的影响要大于融沉效应对路面结构的影响,占路面结构损伤的主要部分。随着时间的增加,融沉效应对路面结构的损伤影响越来越大,在后期对路面结构寿命起到决定性作用,即使没有车辆荷载的作用,路面结构在融沉效应作用下依然会发生破坏。 (4) 分别从路面材料和结构的角度对多年冻土区高等级公路路面进行优化,首先对低导热面层材料进行研究,并对其路用性能和阻热效果进行评价,而后在此基础上提出“反-阻-通”耦合路面路基一体化降温结构,并利用多年冻土区宽幅路基温度场有限元模型评价对其对宽幅路基的降温效果,然后从路面结构优化角度,提出高性能路面结构组合,并利用考虑融沉变形的路面结构损伤模型对不同路面结构寿命进行对比分析。结果表明,低导热面层中生蛭石粉的含量不宜超过12%,加入生蛭石粉后沥青混合料路用性能变化不大,且均满足规范要求。与未添加生蛭石粉的试件相比,加入生蛭石粉的沥青混合料内部温度均有所降低,因此通过在沥青下面层添加生蛭石粉而得到的低导热面层具有良好的阻热效果。“反-阻-通”耦合路面路基一体化降温结构由反射涂层、低导热面层以及通风散热路基三部分组成,并且对宽幅路基具有良好的处治效果。本文提出的高性能路面结构组合(4cmAC-13C+5cmAC-20C+12cmATB-25+6cmAC-13C+18cm级配碎石+20cm水泥稳定碎石)对融沉变形具有较强的适应能力,可应用于青藏高速公路的建设。 总之,本文提出的有限元模型可以实现对多年冻土区高等级公路宽幅路基温度场、融沉变形以及路面结构损伤度的预估,提出的路面优化措施可以有效提高路面结构的寿命。本文的研究为多年冻土区高等级公路的修筑提供了理论基础和科学依据。
英文题目 Optimization of Pavement Structures of Expressways in Permafrost Regions on Qinghai-Tibet Plateau Based on Thaw Settlement
英文主题词 Permafrost,High-grade highway,Wide embankment thaw settlement, pavement optimization design
英文摘要 Expressways to be constructed in permafrost regions on the Qinghai-Tibet Plateau may adopt wide embankment which can absorb much more heat than the existing narrow embankment. Therefore, the thaw settlement of wide embankment will be more severe and the lifespan of pavement structure will be much shortened. In order to solve the problem of pavement structure cracking caused by thaw settlement of wide embankment in permafrost regions, the finite element method was used to simulate the temperature field and thaw settlement of wide embankment. Then the damage behavior and damage evolution process of pavement exposed to thaw settlement were analyzed from the perspective of integration of embankment and pavement. And the pavements of expressways in permafrost regions were optimized in terms of material and structure respectively. The main contents of this thesis are listed as follows. (1) Considering the characteristics of wide embankment in permafrost regions, the basic equations, calculating parameters, boundary conditions and initial conditions of temperature field were put forward. According to the finite element theory, the temperature field model with the second type and third type of temperature boundary conditions was established using ABAQUS and its secondary development platform. The model was used to study the temperature field of wide embankment and the cooling effect of existing engineering measures on wide embankment. The applicability of existing cooling measures of narrow embankment to wide embankment was also evaluated. The results show that the wide embankment of high-grade highways in permafrost region has faster heating rate and poorer thermal stability compared with the narrow embankment of low-grade highways. It also has greater thermal disturbance to the underlying natural frozen soil. When the highway in permafrost regions utilizes wide embankment instead of narrow embankment, the permafrost table will descend and the heterogeneity of frozen soil thawing will be intensified. Compared with other three types of wide embankment, the composite embankment with EPS insulation layer and crushed stone layer has the lowest temperature, the smallest temperature rise and the best thermal stability. (2) After studying the constitutive model of frozen soil, EP model was selected to simulate the mechanical behaviour of permafrost, which was programmed in ABAQUS through the UMAT subroutine. Then a moisture-heat-stress coupling model was constructed to calculate the thaw settlement of wide embankment using the sequential coupling method based on the temperature data obtained by the temperature field model. The results show that with time increasing, the thaw settlements both at the centerline of the embankment and the left side of the slope increase linearly, but the thaw settlement at the centreline increases faster. When the width of embankment increases from 10m to 18m, 26m, 34m, 42m and 50m, the transverse thaw settlement curve changes gradually from quadratic curve to basin shaped curve. The thaw settlement on the top of embankment increases on average by 7.1cm when the embankment height rises 1m. For embankments with different heights, when the embankment width increases, the differential thaw settlement first increases and then decreases. The maximum differential thaw settlement happens when the width is between 18m to 26m. The existing embankment cooling measures in permafrost regions can improve the thermal stability of embankment, but it will also increase the uneven settlement of embankment. Therefore, it is necessary to develop new permafrost cooling measures, which can not only lower the temperature of embankment (especially wide embankment), but also reduce the adverse effects of uneven temperature distribution on the lifespan of pavement structures. (3) Based on the finite element models of temperature field and thaw settlement, the fatigue damage model of pavement structure considering the thaw settlement effect was established according to the basic theory of damage mechanics. Then the damage behavior and damage evolution process of pavement structures subjected to vehicle loads and thaw settlement are analyzed, and the influence of thaw settlement on the design indexes of the asphalt pavement is also studied. The results show that the coupling effect of vehicle load and settlement additional stress leads to sharp increase of the damage of pavement structure, which is much larger than the damage cause by vehicle load or thaw settlement alone. The influence of vehicle load on pavement structure in permafrost regions is greater than the influence of thaw settlement in the early stage, which accounts for the main part of pavement structure damage. With the increase of time, the effect of thaw settlement on pavement structure damage keeps increasing, which plays a decisive role in the pavement structure life. The pavement structure will still crack under the effect of thaw settlement even without vehicle load. (4) The pavement of high-grade highway in permafrost regions is optimized in terms of pavement material and structure respectively. The asphalt pavement with low thermal conductivity was studied first and its road performance and heat resistance effect were evaluated. Then a reflective-resistant-ventilated coupling structure was proposed and its cooling effect for wide embankment was evaluated using the temperature field model built previously. After that, high-performance pavement structure was proposed from the perspective of pavement structure optimization and the pavement structure damage model considering the thaw settlement was used to compare the lifespan of different pavement structures. The results show that the vermiculite powder added into the low thermal conductivity pavement should not exceed 12%. The addition of vermiculite has little effect on road performances of asphalt mixtures, which meet all the requirements of technical specifications. Compared with the samples without vermiculite powder, the internal temperature of asphalt mixture with vermiculite powder decreased obviously. Therefore, the low thermal conductivity layer has good thermal resistance effect. The reflective-resistant-ventilated coupling structure, which consists of re?ective coating, heat-resistant pavement, and crushed-stone embankment, provides a promising way to protect the wide embankment of expressway in permafrost zones. The high-performance pavement structure proposed in this paper (4cmAC-13C+5cm AC-20C + 12 cm ATB-25 + 6cm AC-13C + 18cm unbounded aggregate+20cm cement stabilized macadam) has a strong adaptability to thaw settlement deformation, which can be used in the construction of the Qinghai-Tibet Expressway. In conclusion, the finite element model proposed in this paper can predict the temperature field, thaw settlement deformation and pavement structure damage of high grade highway in permafrost regions. The optimized pavement measures can effectively improve the life of pavement structure. The study provides a theoretical and scientific basis for the construction of high-grade highways in permafrost regions.
学术讨论
主办单位时间地点报告人报告主题
交通学院 2014-11-12 道桥试验室二楼会议室 金光来 基于扩展有限元的疲劳损伤-断裂全过程模拟方法
交通学院 2015-08-28 道桥试验室二楼会议室 程永振 黑棉土路基处治不路面结构一体化技术研究
交通学院 2015-12-15 道桥试验室二楼会议室 程永振 肯尼亚内罗毕绕城公路南环线工程黑棉土路基路面试验段方案
交通学院 2016-12-06 道桥试验室二楼会议室 唐皓 东非黑棉土的膨胀特性及处治技术研究
交通学院 2014-12-16 道桥试验室二楼会议室 汤涛 多年冻土区宽幅路基温度场模拟分析
交通学院 2015-10-19 道桥试验室二楼会议室 汤涛 多年冻土区宽幅路基融沉变形研究
交通学院 2016-05-03 道桥试验室二楼会议室 汤涛 融沉变形作用下路面结构损伤演化规律分析
交通学院 2017-12-27 道桥试验室二楼会议室 汤涛 Bio-oil viscosity test
     
学术会议
会议名称时间地点本人报告本人报告题目
阿斯顿大学公路工程技术交流会 2017-05-17 英国伯明翰 Thermal regime analysis for wide embankment in permafrost regions of Qinghai-Tibet plateau
阿斯顿大学博士生论坛 2017-10-06 英国伯明翰 Design and evaluation of heat-resistant asphalt mixture for permafrost regions
     
代表作
论文名称
青藏高速公路宽幅路基温度场模拟分析
青藏高速公路路基降温措施有效性模拟分析
Laboratory Characterization and Field Validation of ROADMESH-Reinforced Asphalt Pavement in China
 
答辩委员会组成信息
姓名职称导师类别工作单位是否主席备注
赵永利 正高 教授 博导 东南大学
江瑞龄 正高 教授级高工 博导 江苏交通控股有限公司
杜延军 正高 教授 博导 东南大学
许涛 正高 教授 博导 南京林业大学
马涛 正高 教授 博导 东南大学
      
答辩秘书信息
姓名职称工作单位备注
廖公云 副高 副教授 东南大学