寒区冻土层退化条件下桩基础稳定性劣化评价方法  

Assessment method of degradation of pile stability for frozen soil decreasing in cold region

作　　者：王若林[1] 朱道佩 刘小燕[1] 司马军[1] 

机构地区：[1]武汉大学土木建筑工程学院,湖北武汉430072

出　　处：《中南大学学报（自然科学版）》2016年第9期3148-3153,共6页Journal of Central South University:Science and Technology

基　　金：国家自然科学基金资助项目(51278387)~~

摘　　要：在寒区冻土层季节性退化演变过程和未冻土层存在的情况下,对发生典型冻拔破坏的桩基础进行受力分析,得到季节冻融循环演化过程中各土层桩侧摩阻力的计算公式,并在此基础上,对桩基础抗拔稳定性劣化进行研究,建立寒区深层冻土退化、土体出现未冻土层状况下桩基础发生冻拔破坏的临界承载力数值模型。以工程实例对桩基础的各个土层状况进行分析,在假设土的干容重、冻土的总含水量、地中热流值、冻土的导热系数不变,季节冻融层为强冻胀土条件下,分析桩长范围内各层土厚度随时间的变化以及最大冻深处截面应力随未冻土层厚度与桩长之比的关系,对季节循环演变中土体的冻拔力和桩侧摩阻力进行计算、比较,并对群桩基础的抗冻拔稳定性验算方法进行讨论。研究结果表明:部分多年冻土层退化为未冻土层,将导致桩基础的总抗拔力和临界失稳冻结深度减小。桩侧未冻土层厚度与桩长的比值和临界比值的比较结果可作为桩冻拔稳定性的判断标准。得到的临界承载力模型可以为寒区冻土层演化过程中桩基础稳定性评估提供数值分析依据。In the evolution process of deterioration of the permafrost layer, the force analysis of pile foundation which has a typical frost heaving damage was carried out with the presence of unfrozen soil layer. In the evolution process of seasonal freezing and thawing cycle, the calculation formulas of lateral friction resistance of pile foundation of each layer were proposed. Based on this, the degradation mechanism of uplift pile foundation stability was studied, then the numerical model of the critical bearing capacity of pile foundation in frost heaving damage was established with the existence of the unfrozen layer and the degradation of the permafrost layer. Based on the suppositions that factors such as the unit dry weight of the soil, total water content of frozen soil, thermal current in the earth, thermal conductivity of frozen soil were kept constant and the seasonal freeze-thaw soil was strong frost heaving soil, soil condition of the pile foundation of an engineering example was analyzed and thickness of each layer soil that changed over time within the scope of the pile length was established. Also the uplift and tangential frost heaving force change with the thickness of the unfrozen layer ratio to the length of the pile was analyzed. In the evolution process of seasonal freezing-thawing cycle, the frost heaving force and lateral friction resistance of pile foundation were calculated and compared. The calculation method of the uplift pile group foundation stability was discussed. The results show that the degradation of part of permafrost layer will decrease the total uplift force and critical freezing depth of pile foundation. The comparison results of unfrozen soil layer beside pile and length of pile ratio and critical ratio can be used as the criterion of pile frost heaving stability. The critical capacity model provides the basis of numerical analysis for the stability estimation in the evolution process of the permafrost layer

关 键 词：冻土 季节冻融 冻拔 桩基础稳定性 未冻土 

分 类 号：TU45[建筑科学—岩土工程]