多年冻土区新型路桥过渡段结构试验研究

发布时间：2018-06-09 11:38

本文选题：多年冻土 + 路桥过渡段　；参考：《兰州交通大学》2017年硕士论文

【摘要】：自青藏铁路修建以来,在多年冻土区的路桥过渡段处出现了大量病害问题,其中最为严重的是桥台与过渡段的差异性沉降问题。而目前针对多年冻土地区的路基病害问题,已有片块石路基以及通风管道路基等多种以降低路基温度,抬升冻土人为上限的方式的冻土路基,其主要的降温机理是对流换热。但是对于冻土地区的路桥过渡段病害问题,目前还没有统一的过渡段结构形式。通常的处理措施为:在差异沉降造成的凹陷坑内用道砟或碎石进行回填,这种方式从短期治理效果看来是具有修复速度快,修复成本低,且不影响正常的列车运营等优点,但是从长期看来,这种处理方式修复频率高,修复后维持时间短,且容易造成新的病害问题。因此,有必要针对冻土地区的路桥过渡段病害问题特点提出一种新型的路桥过渡段结构,以减小该区域的病害温度,提高铁路运营质量。为此,本文通过将冻土地区的路基病害防治措施与一般非冻土地区路桥过渡段的病害治理措施相结合的思路,提出了一种新型的冻土地区路桥过渡段结构形式,并通过室内模型试验和数值模拟,对该路桥过渡段在冻土地区的水分场、温度场以及沉降规律和使用效果与传统片碎石路基结构形式进行对比分析。得出了以下结论:(1)新型路桥过渡段结构中心底下的平均温度较传统块碎石路基结构下的温度低,表明新型路桥过渡段结构对地基具有较好的冷却效果,并且新型路桥过渡段结构顶层的块碎石层温度明显低于传统块碎石路基结构填料层的温度,说明了新型路桥过渡段中的碎石层具有较强的自然对流换热过程。(2)路基体中的温度、冻融循环过程以及加载作用均对地基冻土层中的未冻水含量有较大的影响,随着温度的降低未冻水含量降低,随着加载作用,未冻水含量增加,随着冻融循环过程增加未冻水含量减下。(3)新型路桥过渡段结构在荷载作用下,路桥沉降差比传统块碎石路基结构的路桥沉降差小很多,说明新型冻土地区路桥过渡段结构对缓解路桥过渡段的差异性沉降具有较好的效果。(4)通过数值数值模拟计算,对三种过渡段温度场进行了对比分析,发现其具有较好的降温效果。在对其50年的长期热稳定分析发现,新型过渡段长期热稳定性较好。
[Abstract]:Since the construction of the Qinghai-Tibet Railway, a large number of diseases have appeared in the transitional section of the road and bridge in permafrost region, among which the most serious one is the differential settlement between the abutment and the transitional section. In view of the problem of roadbed disease in permafrost region, there are many kinds of roadbed which can reduce the temperature of roadbed and lift the upper limit of permafrost. The main cooling mechanism is convection heat transfer. However, there is no uniform structural form of transition section in frozen soil region. The usual treatment measures are as follows: backfilling with ballast or gravel in the pit caused by differential settlement. This method has the advantages of fast repair speed, low repair cost and no influence on normal train operation. However, in the long run, this treatment has the advantages of high repair frequency, short maintenance time, and easy to cause new diseases. Therefore, it is necessary to propose a new structure of road and bridge transition section to reduce the disease temperature and improve the quality of railway operation. In this paper, a new structural form of road and bridge transition section in frozen soil region is put forward by combining the prevention measures of roadbed diseases in permafrost region with the disease treatment measures of road and bridge transition section in general non-frozen soil area. Through indoor model test and numerical simulation, the moisture field, temperature field, settlement law and application effect of the transition section of the road and bridge in frozen soil area were compared with the traditional structure form of crushed stone subgrade. The following conclusions are drawn: (1) the average temperature at the center of the transition section of the new type road and bridge is lower than that under the traditional crushed stone subgrade, which indicates that the new structure of the transition section of the road and bridge has a better cooling effect on the foundation. And the temperature of the top layer of the new road and bridge transition section is obviously lower than that of the packing layer of the traditional block crushed stone subgrade structure, which indicates that the gravel layer in the new type road bridge transition section has strong natural convection heat transfer process. The freeze-thaw cycle and loading have great influence on the content of unfrozen water in the frozen soil of foundation. With the decrease of temperature, the content of unfrozen water decreases, and the content of unfrozen water increases with the action of loading. With the increase of freeze-thaw cycle, the difference of settlement between road and bridge is much smaller than that of traditional crushed stone subgrade. The results show that the structure of the new type of road and bridge transition section in frozen soil area has a better effect on alleviating the differential settlement of the road and bridge transition section. The temperature field of the three transition sections is compared and analyzed by numerical simulation. It is found that it has better cooling effect. The long-term thermal stability of the new transition section is better than that of the new one after 50 years of long-term thermal stability analysis.
【学位授予单位】：兰州交通大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：U213.1;U446.1

【参考文献】