本文關(guān)鍵詞： 道路工程 多年凍土 片塊石路基 溫度場(chǎng) 數(shù)值模擬　出處：《西安科技大學(xué)》2015年碩士論文　論文類型：學(xué)位論文

【摘要】：“溫室效應(yīng)”和人類工程活動(dòng)加速了多年凍土的退化,導(dǎo)致多年凍土區(qū)的工程建設(shè)更加困難。為了增強(qiáng)多年凍土區(qū)公路路基的穩(wěn)定性,保護(hù)路基下部多年凍土,片塊石路基作為一種主動(dòng)降溫措施得到了廣泛應(yīng)用。但是,目前片塊石路基邊坡未進(jìn)行覆蓋處理,減弱了片塊石路基對(duì)多年凍土的保護(hù)作用;其次,針對(duì)片塊石路基降溫效果的大規(guī)�，F(xiàn)場(chǎng)測(cè)試工作開展的較少,尤其缺乏對(duì)其長(zhǎng)期作用效果的有效監(jiān)測(cè)。本論文通過片塊石路基降溫效果的室內(nèi)模型試驗(yàn),結(jié)合野外試驗(yàn)路路基溫度場(chǎng)實(shí)測(cè)數(shù)據(jù),并選取適當(dāng)?shù)哪Ｐ蛯?duì)片塊石路基的溫度場(chǎng)進(jìn)行數(shù)值模擬,探討片塊石路基溫度場(chǎng)變化特征,揭示片塊石路基的降溫機(jī)理。為多年凍土區(qū)路基的設(shè)計(jì)、施工與維護(hù)提供科學(xué)依據(jù),更好地保護(hù)路基下部多年凍土,減少多年凍土地區(qū)路基病害的發(fā)生,具有較高的學(xué)術(shù)價(jià)值和重要的工程意義。主要研究?jī)?nèi)容和結(jié)論如下:(1)為了探索片塊石層的傳熱特性,通過室內(nèi)模擬試驗(yàn),對(duì)相同粒徑的片塊石層在不同的上邊界條件下降溫機(jī)理和降溫效果進(jìn)行了研究。研究結(jié)果表明,在風(fēng)的作用下,封閉邊界的片塊石層對(duì)外界的溫度變化不夠敏感,降溫速度較開放邊界要慢,此時(shí)主要以自然對(duì)流為主,依靠?jī)?nèi)部空氣自然對(duì)流傳熱來實(shí)現(xiàn)對(duì)其底部土層的降溫效果;開放邊界條件下,片塊石內(nèi)部主要以強(qiáng)制對(duì)流為主,依靠外界負(fù)溫環(huán)境下風(fēng)的作用在其內(nèi)部形成強(qiáng)制對(duì)流,以強(qiáng)制對(duì)流傳熱的方式來實(shí)現(xiàn)降溫的。(2)依托青藏公路五道梁段片塊石路基實(shí)體觀測(cè)工程,對(duì)比分析了片塊石路基和普通路基的溫度場(chǎng)變化過程,驗(yàn)證了片塊石路基的主動(dòng)降溫效果。監(jiān)測(cè)結(jié)果表明,相對(duì)于一般填土路基而言,片塊石路基很好地發(fā)揮了“熱二極管”效應(yīng),寒季能增加路基的蓄冷量,暖季可以有效阻止外界熱空氣進(jìn)入路基,對(duì)于防止多年凍土融化、主動(dòng)保護(hù)凍土起到了積極有效的作用。(3)基于多孔介質(zhì)不可壓縮流體的對(duì)流理論,建立了多年凍土區(qū)片塊石路基的對(duì)流換熱數(shù)值計(jì)算模型,并與野外實(shí)測(cè)數(shù)據(jù)進(jìn)行對(duì)比驗(yàn)證,證明該模型是合理可靠的。利用該模型對(duì)片塊石路基的速度場(chǎng)和溫度場(chǎng)進(jìn)行數(shù)值模擬。數(shù)值計(jì)算結(jié)果表明,寒季片塊石層內(nèi)自然對(duì)流最強(qiáng)烈,內(nèi)部存在對(duì)流渦包,降溫效果顯著,可以大量引入外界冷能進(jìn)入路基體;暖季,片塊石層內(nèi)部未見空氣流動(dòng),自然對(duì)流消失,片塊石層起到保溫隔熱作用,能阻擋外界熱量進(jìn)入路基內(nèi)部。對(duì)片塊石路基的長(zhǎng)期熱穩(wěn)定性研究表明,片塊石路基在短期內(nèi)降溫效果明顯,從長(zhǎng)遠(yuǎn)分析,綜合考慮全球氣候變暖和瀝青路面的強(qiáng)吸熱性,片塊石單獨(dú)應(yīng)用于多年凍土地區(qū)公路路基中難以發(fā)揮主動(dòng)降低地溫、保護(hù)多年凍土和維護(hù)路基熱穩(wěn)定性的作用,必須進(jìn)行補(bǔ)強(qiáng)。
[Abstract]:"Greenhouse Effect" and human engineering activities have accelerated the degradation of permafrost, making it more difficult to build permafrost regions. As a kind of active cooling measure, the slice block roadbed has been widely used. However, at present, the slope of the block stone roadbed has not been covered, which weakens the protective effect of the block stone roadbed on permafrost. Secondly, The large scale field test for the cooling effect of rock subgrade is less, especially the effective monitoring of its long-term effect. In this paper, the laboratory model test of the cooling effect of rock block roadbed is carried out. Combined with the measured data of roadbed temperature field in field test road, and selecting appropriate model to simulate the temperature field of rock block roadbed, the variation characteristics of temperature field of rock block roadbed are discussed. This paper reveals the mechanism of cooling of subgrade with block rock, provides scientific basis for the design, construction and maintenance of embankment in permafrost region, better protects the permafrost in the lower part of roadbed, and reduces the occurrence of roadbed disease in permafrost region. It has high academic value and important engineering significance. The main research contents and conclusions are as follows: 1) in order to explore the heat transfer characteristics of the lamellar layer, the laboratory simulation test is carried out. The cooling mechanism and cooling effect of the lamellar layer with the same diameter under different upper boundary conditions are studied. The results show that the lamellar layer with closed boundary is insensitive to the outside temperature change under the action of wind. The cooling rate is slower than the open boundary. At this time, the natural convection is the main factor, and the internal natural convection heat transfer is relied on to realize the cooling effect on the bottom soil layer; under the open boundary condition, the internal convection is mainly forced convection. Relying on the action of wind in the negative temperature environment to form forced convection in its interior and to realize cooling by forced convection heat transfer. (2) relying on the solid observation project of block rock subgrade in the section of five beams of Qinghai-Tibet Highway, The variation process of temperature field of block rock subgrade is compared with that of ordinary subgrade, and the active cooling effect of block stone subgrade is verified. The monitoring results show that, compared with general fill subgrade, the temperature field of block rock subgrade is different from that of normal embankment. The "thermal diode" effect is well played by the block rock subgrade. In the cold season, the storage capacity of the roadbed can be increased, and the warm season can effectively prevent the external hot air from entering the roadbed, thus preventing the permafrost from thawing. Based on the convection theory of incompressible fluid in porous media, a numerical calculation model of convection heat transfer of a piece of rock subgrade in permafrost region is established and compared with the field measured data. It is proved that the model is reasonable and reliable. The velocity field and temperature field of rock subgrade are numerically simulated by using the model. The numerical results show that the natural convection is strongest and the convection vortices exist inside the subgrade in cold season. The cooling effect is remarkable, the external cold energy can be introduced into the roadbed in large quantities; in the warm season, there is no air flow inside the lamellae, the natural convection disappears, and the lamellae plays the role of heat preservation and insulation. The study on the long-term thermal stability of the block subgrade shows that the cooling effect of the subgrade is obvious in the short term. In the long run, considering the strong heat absorption of the global climate warming and asphalt pavement, It is difficult to take the initiative to reduce the ground temperature, protect the permafrost and maintain the thermal stability of the roadbed.
【學(xué)位授予單位】：西安科技大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2015
【分類號(hào)】：U416.1

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