青海省S308线曲麻莱—不冻泉段多年冻土特征研究
发布时间：2018-08-13 20:41
【摘要】：多年冻土具有流变性,其长期强度远低于瞬时强度特征,基于该特征,修建于冻土区的高速公路路基病害频发,严重影响行车安全。S308线是青海省境内连接国道109线和国道214线的一条重要通道,是沟通海西地区、格尔木市与玉树地区之间的交通干线,沿线季节冻土分布较广,地形变化差异较大,特别是玉树地震以后,对本线路的依赖程度更加迫切,新的整治势在必行。本课题以青海省S308线曲麻莱-不冻泉段多年冻土为研究对象,通过对依托工程的地形地貌、气候气象、水文地质、冻土分布特征等分析,在原来多年冻土勘察的基础上,选择典型多年冻土路段,布设勘察断面,通过钻探、探地雷达等手段,对比勘察路基下伏和天然地表条件下多年冻土状态差异,着重研究了道路运营多年以后,路基下与天然地面条件下的多年冻土上限、含冰量、地温等多年冻土状态参数变化,分别对现有砂石路面下多年冻土路基和铺筑沥青路面后冻土路基的稳定性进行评价。通过本论文的研究,可以得出以下结论:(1)多年冻土分布主要受海拔控制,总体上来说下界高程为4450m,季节冻土均分布在此高度以下,丘陵区局部低于此高度地段由于含冰量高,多年冻土仍旧保存。低山区三个主要垭口两侧受局地因素影响,多年冻土下界略高于4450m,在K349附近进入大片连续多年冻土区,但海拔低于4450m的路段已经退化为季节冻土区。(2)山区基岩区地层中地下冰含量极少;小型冲沟高含冰土层位于上限以下厚度不大的松散堆积物中,多以多冰-富冰冻土为主,局部形成含土冰层;宽大冲沟和高平原地带上层松散堆积物下伏的泥岩中夹有纯冰层,有些路段形成泥岩与冰层互层结构。(3)天然地面条件下,沿线湿地草甸内的上限深度在2.0m左右;其他地段多超过3.0m,局部极高温0梯度多年冻土已经开始了自上而下的融化,上限深度可达6~7m。(4)山区多年冻土下界高程附近的多年冻土呈现出强烈的退化趋势,表现为地温梯度近于0梯度,多年冻土上限深度超过5.0m,可能已经出现不衔接状态。(5)坡向是影响山地垭口两侧多年冻土下界高程的主要因素;地面状况的差异可以造成多年冻土地温的显著差别,甚至可影响多年冻土分布态势。(6)现有砂石路面条件下,全线路基稳定性均较好,短期内不会出现强烈的融沉等病害发生。高含冰量地段在铺筑沥青路面以后,由于沥青路面强烈的吸热效应很可能会发生严重的融沉变形,影响路基的稳定性。本课题的实施将为青海省在多年冻土地区后续工程的设计及施工提供经验和参考。
[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.
【学位授予单位】：长安大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：U418.5
[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.
【学位授予单位】：长安大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：U418.5
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