细粒土空间不均匀分布对水分迁移的影响

Effect of unevenly distributed fine-grained soil in space on moisture migration

为了研究冻土地区高速公路路基粗粒土填料中细粒土空间不均匀分布引起的水分迁移易规律,测量常温和冻融循环条件下具有细粒土空间不均匀分布特点试样的水分迁移量,对比分析细粒土空间不均匀分布、粒径空间分布差异和温度对水分迁移量的影响,研究试样初始状态参数对细粒土空间不均匀分布和粒径空间分布差异的影响,建模预测水分迁移极限情况。研究结果表明:在冻融循环和常温情况下,细粒土分布越不均匀,试样上层与下层含水率的差值越大,即水分由试样下层向上层迁移越明显;2种温度条件下,试样水分迁移程度都随着细粒土空间不均匀分布程度和粒径空间不均匀分布程度增大而增大;当粒组平均直径差异引起的粒径空间不均匀分布程度大于78.33%时,水分迁移程度迅速增长;细粒土空间不均匀分布和粒径空间分布差异增加主要是由细颗粒质量分数增加和最大粒组的平均粒径减小引起的,初始孔隙比的影响排在第3位;温度一定时,水分迁移程度与细粒土空间不均匀分布参数有二次函数关系。水分迁移主要发生在常温放置条件下的第1天内或第1次冻融循环的融化阶段;冻融循环条件下具有不均匀分布特点试样的水分迁移程度明显高于常温条件下试样的水分迁移程度;冻融循环条件下细粒土空间不均匀分布试样下层迁移至上层中最大含水量约为38%。

To study the water migration caused by unevenly spatial distribution of fine-grained soil in the roadbed filling of coarse-grained soil of expressway in permafrost area,the water migration of unevenly specimens under the condition of normal temperature and freeze-thaw cycle was measured.The effect of spatial non-uniform distribution of fine-grained soil,spatial distribution difference of particle size and temperature conditions on moisture migration degree was contrastively analyzed.The effects of initial state parameters on the spatial distribution of fine-grained soil and the spatial distribution difference of particle size were studied.The threshold condition of moisture migration was predicted by modeling.The results show that under the condition of freezethaw cycle and normal temperature,the more uneven the distribution of fine-grained soil is,the greater the difference of water content between upper and lower layers of samples is,which means that the water migration from the lower layer to the upper layer is more obvious.The degree of water migration increases with the increase of non-uniformly spatial distribution degree of fine-grained soil and particle size under two temperature conditions.When the spatial non-uniform distribution of particle size caused by the difference of particle group average diameter is greater than 78.33%,the degree of water migration increases rapidly.The increase of spatial non-uniform distribution and difference of particle size distribution of fine-grained soil are mainly caused by the increase of fine-grained mass fraction and the decrease of average particle size of the largest particle group,and the effect of initial void ratio ranked the third.When the temperature is constant,there is a quadratic function relationship between the parameters of water migration degree and the spatial non-uniform distribution of finegrained soil.The main stage of water migration occurs in the first day at normal temperature or in the melting stage of the first freeze-thaw cycle.The moisture migration degree of specimens with the characteristics of nonuniform distribution during freeze-thaw cycles is significantly higher than that at normal temperature.The maximum content of moisture migrating from the lower layer to the upper layer of unevenly specimen under the condition of freeze-thaw cycle is 38%.