寒区冷却路基参数优化及冷却效果分析

发布时间：2018-05-25 09:45

本文选题：多年冻土 + 冷却路基　；参考：《重庆交通大学》2014年硕士论文

【摘要】：冻土是一种特殊的土体,其对外界气候条件的变化以及人类的工程活动相当敏感。随着全球气候变暖,以及人类工程活动在多年冻土区日益频繁,冻土原有的热平衡受到破坏,伴随而来的就是冻土区工程病害的发生。对于我国冻土分布广泛的青藏高原地区,路基工程的开展面临着许多困难,路基铺设于冻土上,位于路基下方的冻土因热平衡失调导致冻土上限下降而造成路基的不均匀沉降,是造成冻土区路基遭到破坏的主要原因,如何降低路基工程对多年冻土的影响成了一个研究课题。为此,学者提出了新的冷却路基结构,这种结构能够通过在路基中埋设水箱,利用水箱中储存的水进行热交换,来实现冻土与路基外界之间的热平衡,从而达到保护冻土的目的,但未就有关参数提供参考值。针对这一问题,采用有限元软件ANSYS对这种路基结构的有关参数进行参数优化,首先在一个气温条件下,初步分析水层厚度与埋设位置对冷却效果的影响,并与普通路基进行对比,在此基础上进一步分析不同气温条件、水层厚度、埋设位置之间的关系。主要结论如下： ①相对于普通路基,设置水层的路基在长期使用的过程当中,具有明显的保护路基下冻土的作用。 ②对于任何一种水层厚度和埋设位置的组合,在长期使用的过程当中,随着外界气温的增加,冻土上限会逐渐下移,但相对于通路基而言,冻土上限的下降速度比较缓慢,这也说明了这种路基结构形式对保护冻土起到非常积极的作用。 ③水层厚度和水层在路基中的埋设位置这两个参数对冷却效果有着直接的影响,水层厚度越大、水层在路基中埋设的位置越浅,冷却效果就越明显。但这两个参数对冷却效果的影响也是有差异的,水层厚度对于冷却效果的影响相对于水层在路基中的埋设位置要大。 ④得到了水层厚度、埋设位置、气温条件之间的关系曲线,并从曲线中分析得知：要达到较好的冷却效果,相同埋设位置所需的水层厚度随着年平均气温的升高而增大,当气温升高时,水层厚度增大值与其埋设位置也存在一定的关系,水层在路基中设置的位置越浅,所需增加的厚度逐渐减小；在气候变暖的背景下,使用年限越长,所需要的水层厚度越大；当年平均气温相同时,要达到较好的冷却效果,所需的水层厚度随着埋设位置加深而增大,随着水层埋设位置由深变浅,所需增加的厚度逐渐减小。
[Abstract]:Frozen soil is a special kind of soil, which is sensitive to the change of external climatic conditions and human engineering activities. With the global warming and the increasing frequency of human engineering activities in permafrost regions, the original thermal balance of frozen soil has been destroyed, which is accompanied by the occurrence of engineering diseases in permafrost regions. For the Qinghai-Tibet Plateau, where the frozen soil is widely distributed in China, the roadbed engineering is faced with many difficulties. The roadbed is laid on the permafrost, and the permafrost below the roadbed is caused by the uneven settlement of the roadbed due to the decrease of the upper limit of the permafrost due to the imbalance of the thermal balance. It is the main reason that the roadbed in frozen soil region is destroyed. How to reduce the influence of subgrade engineering on permafrost has become a research topic. Therefore, a new cooling subgrade structure is proposed, which can realize the thermal balance between the frozen soil and the roadbed by embedding water tank in the roadbed and using the stored water in the water tank for heat exchange. Thus, the aim of protecting frozen soil is achieved, but the reference value of relevant parameters is not provided. In order to solve this problem, the parameters of the subgrade structure are optimized by the finite element software ANSYS. Firstly, under a temperature condition, the influence of water layer thickness and buried position on the cooling effect is preliminarily analyzed. On the basis of comparison with ordinary subgrade, the relationship among different temperature conditions, water layer thickness and buried position is analyzed. The main conclusions are as follows: Compared with ordinary subgrade, subgrade with water layer has obvious function of protecting permafrost in the process of long-term use. (2) for any combination of water layer thickness and buried position, with the increase of outside temperature, the upper limit of frozen soil will gradually move down during the long-term use, but the rate of decline of the upper limit of frozen soil is slower than that of roadbed. This also shows that this subgrade structure form plays a very positive role in protecting frozen soil. (3) the thickness of water layer and the location of water layer in roadbed have direct influence on cooling effect. The greater the thickness of water layer, the shallower the position of water layer embedded in the roadbed, the more obvious the cooling effect will be. However, the influence of these two parameters on cooling effect is also different. The influence of water layer thickness on cooling effect is greater than that of water layer buried in subgrade. (4) the relation curves of water layer thickness, buried position and temperature condition are obtained, and the analysis shows that the water layer thickness required by the same embedding position increases with the increase of annual mean temperature to achieve better cooling effect. When the temperature increases, the increasing value of water layer thickness also has a certain relationship with its buried location. The shallower the water layer is in the roadbed, the required thickness gradually decreases; under the background of climate warming, the longer the service life, the longer the water layer is placed in the roadbed. When the average air temperature is the same, the required water layer thickness increases with the depth of the buried layer, and decreases gradually with the depth of the buried layer.
【学位授予单位】：重庆交通大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：U416.16

【参考文献】