【摘要】：多年凍土具有流變性,其長期強(qiáng)度遠(yuǎn)低于瞬時(shí)強(qiáng)度特征,基于該特征,修建于凍土區(qū)的高速公路路基病害頻發(fā),嚴(yán)重影響行車安全。S308線是青海省境內(nèi)連接國道109線和國道214線的一條重要通道,是溝通海西地區(qū)、格爾木市與玉樹地區(qū)之間的交通干線,沿線季節(jié)凍土分布較廣,地形變化差異較大,特別是玉樹地震以后,對本線路的依賴程度更加迫切,新的整治勢在必行。本課題以青海省S308線曲麻萊-不凍泉段多年凍土為研究對象,通過對依托工程的地形地貌、氣候氣象、水文地質(zhì)、凍土分布特征等分析,在原來多年凍土勘察的基礎(chǔ)上,選擇典型多年凍土路段,布設(shè)勘察斷面,通過鉆探、探地雷達(dá)等手段,對比勘察路基下伏和天然地表?xiàng)l件下多年凍土狀態(tài)差異,著重研究了道路運(yùn)營多年以后,路基下與天然地面條件下的多年凍土上限、含冰量、地溫等多年凍土狀態(tài)參數(shù)變化,分別對現(xiàn)有砂石路面下多年凍土路基和鋪筑瀝青路面后凍土路基的穩(wěn)定性進(jìn)行評價(jià)。通過本論文的研究,可以得出以下結(jié)論:(1)多年凍土分布主要受海拔控制,總體上來說下界高程為4450m,季節(jié)凍土均分布在此高度以下,丘陵區(qū)局部低于此高度地段由于含冰量高,多年凍土仍舊保存。低山區(qū)三個(gè)主要埡口兩側(cè)受局地因素影響,多年凍土下界略高于4450m,在K349附近進(jìn)入大片連續(xù)多年凍土區(qū),但海拔低于4450m的路段已經(jīng)退化為季節(jié)凍土區(qū)。(2)山區(qū)基巖區(qū)地層中地下冰含量極少;小型沖溝高含冰土層位于上限以下厚度不大的松散堆積物中,多以多冰-富冰凍土為主,局部形成含土冰層;寬大沖溝和高平原地帶上層松散堆積物下伏的泥巖中夾有純冰層,有些路段形成泥巖與冰層互層結(jié)構(gòu)。(3)天然地面條件下,沿線濕地草甸內(nèi)的上限深度在2.0m左右;其他地段多超過3.0m,局部極高溫0梯度多年凍土已經(jīng)開始了自上而下的融化,上限深度可達(dá)6~7m。(4)山區(qū)多年凍土下界高程附近的多年凍土呈現(xiàn)出強(qiáng)烈的退化趨勢,表現(xiàn)為地溫梯度近于0梯度,多年凍土上限深度超過5.0m,可能已經(jīng)出現(xiàn)不銜接狀態(tài)。(5)坡向是影響山地埡口兩側(cè)多年凍土下界高程的主要因素;地面狀況的差異可以造成多年凍土地溫的顯著差別,甚至可影響多年凍土分布態(tài)勢。(6)現(xiàn)有砂石路面條件下,全線路基穩(wěn)定性均較好,短期內(nèi)不會出現(xiàn)強(qiáng)烈的融沉等病害發(fā)生。高含冰量地段在鋪筑瀝青路面以后,由于瀝青路面強(qiáng)烈的吸熱效應(yīng)很可能會發(fā)生嚴(yán)重的融沉變形,影響路基的穩(wěn)定性。本課題的實(shí)施將為青海省在多年凍土地區(qū)后續(xù)工程的設(shè)計(jì)及施工提供經(jīng)驗(yàn)和參考。
[Abstract]:Permafrost has rheological properties and its long-term strength is much lower than that of instantaneous strength. Line S308, which seriously affects traffic safety, is an important passage connecting National Highway 109 and National Road 214 in Qinghai Province. It is a major link between Hercynian, Golmud and Yushu. The seasonal frozen soil is widely distributed along the line. The variation of topography is quite different, especially after the Yushu earthquake, the dependence on this line is more urgent, so it is imperative to renovate. In this paper, the permafrost in Qumaolai-Wujingquan section of S308 line in Qinghai Province is taken as the research object. Based on the analysis of topographic and geomorphology, climate and meteorology, hydrogeology and distribution characteristics of permafrost, and on the basis of the original permafrost investigation, The typical permafrost section is selected, the investigation section is set up, and by means of drilling and ground penetrating radar, the difference of permafrost state under the subgrade and natural surface condition is compared, and the road operation years later is emphatically studied. The upper limit of permafrost under subgrade and natural ground condition, the change of permafrost state parameters such as ice content and ground temperature, respectively, are evaluated for the stability of permafrost roadbed under the existing sand and stone pavement and the permafrost roadbed after paving asphalt pavement. Through the research of this paper, we can draw the following conclusions: (1) the distribution of permafrost is mainly controlled by altitude, the lower boundary height is 4450m, the seasonal frozen soil is distributed below this height, and the hilly region is below this height because of the high ice content. Permafrost is still preserved. The local factors influence the two sides of the three main Yakou in the low mountain area. The lower boundary of permafrost is slightly higher than 4450m, and it enters a large area of continuous permafrost area near K349. However, the sections below 4450m above sea level have been degraded to seasonal frozen soil regions. (2) the underground ice content in the bedrock strata of mountainous areas is very low, and the small gully high ice layer is located in the loose deposits with a small thickness below the upper limit, most of which are polyglacy-rich frozen soil. Local formation of soil-bearing ice layer; wide gully and high plain areas of the upper layer of loose deposits of mudstone buried in pure ice layer, some sections formed mudstone and ice interlayer structure. (3) under natural ground conditions, The upper limit depth of wetland meadow along the route is about 2.0 m, and the other areas are more than 3.0 m, and the top-to-bottom melting of permafrost with local extreme high temperature and 0 gradient permafrost has already begun. The upper limit depth can reach 6 ~ 7 m. (4) the permafrost near the lower height of permafrost in mountainous area shows a strong trend of degradation, showing that the geothermal gradient is close to zero gradient. If the upper limit depth of permafrost is more than 5.0 m, there may already be a state of disconnection. (5) the slope direction is the main factor affecting the elevation of permafrost on both sides of the mountain pass, and the difference of the ground condition can cause the significant difference in the ground temperature of the permafrost for many years. It can even affect the distribution of permafrost. (6) under the existing sand and stone pavement conditions, the stability of the whole roadbed is good, and there will be no strong thawing and other diseases in the short term. After the asphalt pavement is paved with high ice content, the strong heat absorption effect of asphalt pavement will probably result in serious melt settlement deformation, which will affect the stability of roadbed. The implementation of this project will provide experience and reference for the design and construction of follow-up projects in permafrost regions of Qinghai Province.
【學(xué)位授予單位】：長安大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2015
【分類號】：U418.5

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本文編號：2182124