本文選題：多年凍土 + 冷卻路基　； 參考：《重慶交通大學(xué)》2014年碩士論文

【摘要】：凍土是一種特殊的土體,其對(duì)外界氣候條件的變化以及人類的工程活動(dòng)相當(dāng)敏感。隨著全球氣候變暖,以及人類工程活動(dòng)在多年凍土區(qū)日益頻繁,凍土原有的熱平衡受到破壞,伴隨而來的就是凍土區(qū)工程病害的發(fā)生。對(duì)于我國(guó)凍土分布廣泛的青藏高原地區(qū),路基工程的開展面臨著許多困難,路基鋪設(shè)于凍土上,位于路基下方的凍土因熱平衡失調(diào)導(dǎo)致凍土上限下降而造成路基的不均勻沉降,是造成凍土區(qū)路基遭到破壞的主要原因,如何降低路基工程對(duì)多年凍土的影響成了一個(gè)研究課題。 為此,學(xué)者提出了新的冷卻路基結(jié)構(gòu),這種結(jié)構(gòu)能夠通過在路基中埋設(shè)水箱,利用水箱中儲(chǔ)存的水進(jìn)行熱交換,來實(shí)現(xiàn)凍土與路基外界之間的熱平衡,從而達(dá)到保護(hù)凍土的目的,但未就有關(guān)參數(shù)提供參考值。針對(duì)這一問題,采用有限元軟件ANSYS對(duì)這種路基結(jié)構(gòu)的有關(guān)參數(shù)進(jìn)行參數(shù)優(yōu)化,首先在一個(gè)氣溫條件下,初步分析水層厚度與埋設(shè)位置對(duì)冷卻效果的影響,并與普通路基進(jìn)行對(duì)比,在此基礎(chǔ)上進(jìn)一步分析不同氣溫條件、水層厚度、埋設(shè)位置之間的關(guān)系。主要結(jié)論如下： ①相對(duì)于普通路基,設(shè)置水層的路基在長(zhǎng)期使用的過程當(dāng)中,具有明顯的保護(hù)路基下凍土的作用。 ②對(duì)于任何一種水層厚度和埋設(shè)位置的組合,在長(zhǎng)期使用的過程當(dāng)中,隨著外界氣溫的增加,凍土上限會(huì)逐漸下移,但相對(duì)于通路基而言,凍土上限的下降速度比較緩慢,這也說明了這種路基結(jié)構(gòu)形式對(duì)保護(hù)凍土起到非常積極的作用。 ③水層厚度和水層在路基中的埋設(shè)位置這兩個(gè)參數(shù)對(duì)冷卻效果有著直接的影響,水層厚度越大、水層在路基中埋設(shè)的位置越淺,冷卻效果就越明顯。但這兩個(gè)參數(shù)對(duì)冷卻效果的影響也是有差異的,水層厚度對(duì)于冷卻效果的影響相對(duì)于水層在路基中的埋設(shè)位置要大。 ④得到了水層厚度、埋設(shè)位置、氣溫條件之間的關(guān)系曲線,并從曲線中分析得知：要達(dá)到較好的冷卻效果,相同埋設(shè)位置所需的水層厚度隨著年平均氣溫的升高而增大,當(dāng)氣溫升高時(shí),水層厚度增大值與其埋設(shè)位置也存在一定的關(guān)系,水層在路基中設(shè)置的位置越淺,所需增加的厚度逐漸減��；在氣候變暖的背景下,使用年限越長(zhǎng),所需要的水層厚度越大；當(dāng)年平均氣溫相同時(shí),要達(dá)到較好的冷卻效果,所需的水層厚度隨著埋設(shè)位置加深而增大,隨著水層埋設(shè)位置由深變淺,所需增加的厚度逐漸減小。
[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.
【學(xué)位授予單位】：重慶交通大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2014
【分類號(hào)】：U416.16

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