变温幅度和间歇时间对土体冻胀影响的试验研究

INFLUENCES OF TEMPERATURE AMPLITUDES AND TIME INTERVALS ON FROST HEAVE

选取冻胀敏感性粉质黏土,利用人工冻土一维冻胀试验系统进行不同变温幅度和间歇时间作用下的后间歇冻结试验,以试样冻深达到稳定阶段为初始时刻分析冻结锋面、冻胀量及温度梯度变化曲线,得到冷端变温幅度和间歇时间对土体冻胀的影响规律。结果表明:不同变温幅度作用下的冻结锋面、冻胀量曲线呈周期性变化,变化周期为240 min,与间歇时间相同。随着变温幅度的增大,冻胀量分别为3.38,2.55 mm,与连续冻结模式相比,冻胀量分别减少了23.2%,42.0%。相同变温幅度,间歇时间为2,4,8 h的土体冻胀量曲线分别呈抛物型、阶梯型和折线型增长趋势,冻胀量分别为2.82,2.55和1.81 mm。土体冻胀量随着间歇时间的增大而减小,但间歇时间不宜大于8 h,否则分凝冰层融化,冻胀量衰减,对于实际冻结工程,则会影响冻土壁强度。

In this paper,frost heave tests using frost susceptible silty clay were carried out by 1-D frost heaving test system with different temperature amplitudes and time intervals in continuous-intermittent freezing mode.Freezing front,frost heave and temperature gradient were analyzed when frost depth reached in stable stage.The influences of temperature amplitudes and time intervals on frost heave were acquaired.The results show that,in different temperature amplitudes,the curves of freezing front and frost heave fluctuate periodically and the period is 240 min which is equal to time intervals.Frost heave is 3.38 mm and 2.55 mm in different temperature amplitudes.With the increase of temperature amplitudes,frost heave reduce 23.2% and 42.0% respectively than that in continuous freezing mode.In different time intervals,frost heave increase in the parabolic,step and broken line type.Frost heave is 2.82 mm,2.55 mm and 1.81 mm when time intervals are 2 h,4 h and 8 h respectively.It is clear that frost heave reduces with the increase of time intervals.However,if time intervals are longer than 8 h,segregation ice and frost heave decrease.In that case,the strength of frozen wall will decrease in artificial freezing project.