季冻区公路路基低液限粉质黏土动强度指标的影响因素研究

在季节性冻土区,公路路基土动强度特性的影响因素较为复杂。以探究冻融循环作用对季冻区公路路基强度和变形特性的影响为目的,通过冻融循环作用下的室内动三轴试验,得到动强度指标随冻融循环次数、压实度和振动频率的变化规律,并采用正交试验设计方法进行显著性分析,探究各影响因素的影响程度。结果表明:随着冻融循环次数的增加,动内摩擦角呈现出一定的衰减趋势,但动黏聚力下降明显;随着压实度的增加,动内摩擦角约增加10%左右,动黏聚力值基本呈线性上升趋势,约升高1倍左右;随着振动频率的增加,动内摩擦角无明显变化,其值在31°～35°范围内波动,动黏聚力值呈上升趋势,且经历冻融循环后,上升幅度减小;各因素及其交互作用对动黏聚力的影响从大到小依次为压实度B,冻融循环次数A,交互作用A×B,振动频率C,交互作用B×C,交互作用A×C。研究成果对季冻区公路路基冻胀和融沉的防治,以及公路的服役性能和维护具有参考价值。

Study on influence factors of dynamic strength index of low liquid limit silty clay of highway subgrade inseasonal frozen region

Influence factors of dynamic strength characteristics of subgrade soil are complicated in seasonal frozen soil region. By taking the influence from the effect of freezing-thawing cycle on the strength and deformation characteristics of highway subgrade in the seasonal frozen region as the study objective，the changing law of the dynamic strength index depended on the number of freezing-thawing cycle，degree of compaction and vibration frequency is obtained through the relevant indoor dynamic tri-axial test under freezing-thawing cycle，and then the significance analysis is made with the design method of orthogonal test，while the influencing degrees of all the influencing factors are explored as well. The result shows that along with the increase of the number of freezing-thawing cycle，the dynamic internal friction angle exhibits a declining trend，while the dynamic cohesion is obviously declined. Along with the increase of the compaction degree，the dynamic internal friction angle is increased by about 10% ， while the value of dynamic cohesion basically presents an increasing trend with the increasing amplitude of about 1 times. Along with the increase of vibration frequency，the dynamic internal friction angle is not obviously changed with the fluctuation of the value within the range of 31° ～ 35°，while the dynamic cohesion exhibits an increasing trend，of which the increasing amplitude is to be decreased after freezing-thawing cycle. The influences from all the factors and their interactions on the dynamic cohesion are compaction degree B，number of freezing-thawing cycle A，interaction A × B，vibration frequency C，interaction B × C， from large to small in turn. The study result has referential value for control and prevention of frost-heave and thaw-settlement of highway subgrade in seasonal frozen region as well as the service performance and maintenance of the road.