Characteristics of Permafrost along Highway G214 in the Eastern Qinghai-Tibet Plateau

The characteristics of the permafrost along National Highway No. 214(G214) in Qinghai province(between kilometer markers K310 and K670),including the distribution patterns of permafrost and seasonally frozen ground(SFG), ground ice content and mean annual ground temperature(MAGT), were analyzed using a large quantity of drilling and measured ground temperature data. Three topographic units can be distinguished along the highway: the northern mountains, including Ela Mountain and Longstone Mountain; the medial alluvial plain and the southern Bayan Har Mountains.The horizontal distribution patterns of permafrost can be divided into four sections, from north to south: the northern continuous permafrost zone(K310-K460),the island permafrost zone(K460-K560), the southern continuous permafrost zone(K560-K630),and the discontinuous permafrost zone(K630-K670).Vertically, the permafrost lower limits(PLLs) of the discontinuous zone were 4200/4325 m, 4230/4350 m,and 4350/4450 m on the north-facing/south-facing slopes of Ela Mountain, Longstone Mountain and Bayan Har Mountains, respectively. The permafrost was generally warm, with MAGTs between-1.0°C and0°C in the northern continuous permafrost zone,approximately-0.5°C in the island permafrost zone,between-1.5°C and 0°C in the southern continuous permafrost zone, and higher than-0.5°C in the discontinuous permafrost zone. In contrast, the spatial variations in ground ice content were mainly controlled by the local soil water content and lithology.The relationships between the mean annual air temperature(MAAT) and the PLLs indicated that the PLLs varied between-3.3°C and-4.1°C for the northern Ela and Longstone Mountains and between-4.1°C and-4.6°C in the southern Bayan Har Mountains.

高密度电法在G214公路工程地质勘察中的应用

2010年4月14日,青海省玉树藏族自治州发生了7.1级地震,给当地人民生命财产造成了严重损失。为了保证灾后重建工作的顺利实施,交通部规划G214线共和至结古段建设成为高速公路。拟建公路穿越青藏高原大片多年冻土区,工程地质条件复杂,且当前在青藏高原多年冻土区尚无修筑高等级公路的先例,因此,查明拟建公路沿线多年冻土类型和分布情况意义重大。详细介绍了高密度电法勘探的工作原理和方法,并将它在G214公路多年冻土区的勘探成果进行分析。结果表明,采用高密度电法结合工程地质钻探所获取的物性参数,可用来划分多年冻土类型、测定多年冻土上限,在特定区域可获取连续的冻土工程地质特性,结果满足工程勘探要求。

深切河谷区河流陡峭指数与岩体质量的空间分布特征及其相关关系研究

河流下切作用是深切河谷区地貌演化的重要地质营力。它常常通过对河道的下切和侧蚀过程等影响着河谷两侧斜坡的稳定性状态和斜坡演化。目前,在河流下切作用下斜坡岩体质量的空间分布特征及两者的定量化关系等方面研究较少。这在一定程度上制约着深切河谷区斜坡岩体稳定性预测及地质灾害易发性评价的发展。基于上述背景,本文依托青藏高原深切河谷区(澜沧江—金沙江)和G214左贡—虎跳峡段,基于岩体质量评价BQ系统和河流水力侵蚀模型,利用现场调查、统计和Matlab、Topotoolbox、ArcGIS、Origin等工具手段,研究了研究区河流陡峭指数(k_(sn))和岩体质量指标的空间分布特征、相关关系和内在机制。结果表明:在研究区,岩体质量与断裂密度、k_(sn)、工程岩组的皮尔逊相关性系数分别为:0.52、0.67、-0.11,即岩体质量与k_(sn)的相关性程度最高。基于横剖面形态提取和河谷边坡应力特征区分析发现:本文所研究岩体质量的特征分布区主要为对河流下切作用作出实时敏感响应的斜坡段,即河流下切作用的强烈影响段。基于研究结果,本文提出在深切河谷区,k_(sn)应该作为重要评价指标在表征河流下切作用对崩塌灾害易发性评价中进行考虑和使用。