GEOLOGICAL FORMATION AND THAW-SETTLEMENT CHARACTERISTICS OF FROZEN SOIL IN SULIJIAN GULLY, SOUTHERN TIANSHAN MOUNTAINS
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摘要: 气候变暖为冻土区域的工程建设带来更多不确定性,查明冻土的地质成因及其融沉特性对于工程选址以及工法选择等尤为重要。本文以南天山地区的苏力间沟内分布的山地冻土为研究对象,通过钻探、高密度电法、地温监测以及室内试验等,查明该区域冻土的空间分布,剖析冻土形成条件和形成机理模式,揭示其融沉特性及影响因素。结果表明:苏力间沟内多年冻土和季节性冻土均有分布,季节性冻土和不连续多年冻土主要分布在左岸,即阳坡坡麓;连续多年冻土主要分布在苏力间河右岸,即阴坡坡麓;冻土层分布深度和厚度不均匀,多分布在1.9~2.7 m厚的表土下,厚约1.5~10 m;在冻土地质成因模式上分为阴坡富水低温成因模式和阳坡坡面汇流成因模式;苏力间沟多年冻土区的融沉系数介于0.39%和91.25%之间,其中连续多年冻土区的融沉系数多值区间在42.5%和68.75%之间,平均值为55.62%;苏力间沟多年冻土融沉系数与总含水率、天然密度、干密度、天然孔隙比和液性指数相关性较高,皮尔森相关系数均达0.8以上。Abstract: Climate warming introduces increasing uncertainty to engineering construction in the cryosphere. It is crucial to accurately determine the geological formation and thaw-settlement characteristics of frozen soils when selecting project sites and construction methods. This paper investigated the mountainous frozen soil distributed in the Sulijian Gully in the southern Tianshan region and used the methods of drilling,high-density electrical tomography,and ground temperature monitoring. It clarified the spatial distribution of the frozen soil in the region and summarized the formation conditions and mechanisms of the frozen soil. Then,it revealed the thawing-settlement characteristics and their influencing factors with laboratory tests. The results show that both permafrost and seasonally frozen soils are distributed in the Sulijian Gully. The seasonally frozen soils and discontinuous permafrost are mainly distributed at the toe of the left bank(the sunny slope),while continuous permafrost is mainly distributed at the toe of the right bank(shady slope). The depth and thickness distributions of the permafrost layer are uneven,which are mostly distributed below the 1.9~2.7m-thick topsoil,with a thickness range of 1.5~6m. The geological formation mode of permafrost can be divided into two types: the formation mode of rich water and low temperature on the shady slope,and the formation mode of convergence on the sunny slope. The thaw-settlement coefficient of the Sulijian Gully permafrost area ranges from 0.39% to 91.25%,while the multiple value range of the continuous permafrost area is between 42.5% and 68.75%,with an average value of 55.62%. The thaw-settlement coefficient of the Sulijian Gully permafrost is highly correlated with total water content,natural density,dry density,natural void ratio,and liquid index,with the Pearson correlation coefficients exceeding 0.8.
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表 1 试验指标及方法、仪器等一览表
Table 1. List of test indicators and methods, instruments,etc.
序号 实验项目 试验方法 采用仪器 实验条件 1 颗粒尺寸 筛析法/密度计法 电热干燥箱(101A-3E)、电子天平(YP300001)、土壤筛0.075~60mm、密度计(TM-85)、量筒1000 mL 室温 2 总含水率 烘干法 电热干燥箱(101A-3E)、电子天平(ES2200) 负温环境 3 天然密度 联合测定法/环刀法 排液筒、台秤(EP-22KA)、量筒1000 mL、天平(ES2200) 负温环境 4 颗粒密度 量瓶法/虹吸筒法 量瓶100 mL、天平(FA 2004)、恒温水槽(HHS-6)、砂浴(DKS300*300)、虹吸筒、量筒2000 mL、台秤(EP-22KA) 室温 5 液限 液、塑限联合测定法 液塑限联合测定仪(GSY-2型)、天平(ES2200)、电热干燥箱(101A-3E) 室温 6 塑限 液、塑限联合测定法 液塑限联合测定仪(GSY-2型)、天平(ES2200)、电热干燥箱(101A-3E) 室温 7 融化下沉系数 室内冻土融化压缩试验 融化压缩仪(SC-15型)、恒温水槽(HHS-6) 负温环境 干密度、天然孔隙比和饱和度为计算值 表 2 冻土融沉系数与基本物理指标相关性一览表
Table 2. Pearson correlation coefficient between thawing-settlement coefficient and basic physical indexes of frozen soil
取样深度 总含水率 天然密度 干密度 颗粒密度 天然孔隙比 饱和度 液限 塑限 塑性指数 液性指数 连续多年冻土区融沉系数 0.245** 0.895** -0.845** -0.876** 0.046 0.896** 0.379** 0.359** 0.347** 0.087 0.889** 不连续多年冻土区融沉系数 -0.041 0.887** -0.865** -0.940** -0.001 0.892** 0.398 0.107 0.158 -0.155 0.893** * *相关性在0.01层上显著 -
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