Alpine soil infiltration process is an important part of the hydrological characteristics of alpine soil in permafrost. This research is carried out in the source region of the Yellow River where the permafrost is severely degraded, using various methods for choosing typical sample areas, and to experiment, study and simulate the soil water curve, soil saturated hydraulic conductivity, soil infiltration and soil moisture under different characteristics of degraded vegetation. The results indicate that the empirical equation θ=AS-B, proposed by Gradner and Visser, is very reliable in simulating the soil moisture curve; soil saturated hydraulic conductivity and soil infiltration are significantly different under different vegetation coverage: in the soil surface within 0-10 cm, the saturated hydraulic conductivity and infiltration intensity of Black Beach are the strongest; respectively, in soil layers below 30 cm, vegetation has almost no impacts on the saturated hydraulic conductivity, infiltration intensity and soil moisture content. Significant reduction of soil moisture occurs in soil surfaces with degraded vegetation. The more serious the degradation, the more water loss, and it can be up to 38.6% in the worst situation. Soil moisture of developed vegetation root systems in depths within 10-20 cm has the greatest impact on the soil environment, and the loss of moisture induces difficulty in the restoration of degraded meadows. Through a comparative study, the Kostiakov infiltration equationf(t) = at-b is more applicable for studies on the process of soil moisture infiltration of the alpine meadow in the source region of the Yellow River.
Climate change and engineering activities are the leading causes of permafrost temperature increase,active layer thickening,and ground-ice thaw,which trigger changes in the engineering stability of embankments.Based on the important research advances on permafrost changes and frozen soil engineering in Qinghai-Xizang Plateau,the changes in permafrost temperature and active layer thickness,their relationships with climate factors,the response process of engineering activities on permafrost,dynamic change of engineering stability of Qinghai-Xizang Railway,and the cooling mechanism and process of crushed-rock layers are discussed using the monitoring data of permafrost and embankment deformation.Finally,solutions to the key scientific problems of frozen soil engineering under climate change are proposed.
以沈哈高速铁路沿线的粘质黄土为研究对象,在恒温状态下进行了开放系统水分迁移试验,试验结果表明:随着时间的推移,湿润锋面由底部逐渐向上迁移,含水量也由试件的底部向顶部逐渐减小,试验结束时土柱中的含水量基本表现出由底部向顶部逐渐减小的趋势.基于上述试验终态时刻土体体积含水量沿试样高度的分布,利用灰色理论预测模型GM(1,1)并结合室内冻胀敏感性试验资料确定出了东北粘质黄土的有害毛细上升高度约为1.12 m.在此基础之上,结合长春地区的最大冻深资料,计算出要保证粘质黄土不产生冻胀,其距离地下水位的最小高度约为2.92 m.