考虑荷载影响的黄土冻胀特性研究

Frost heaving characteristics for loess under different load

黄土的冻胀特性与土体的含水率、土体的密度以及外部荷载关系密切。在室内对不同含水率、不同密度的黄土试样施加不同荷载,进行了冻胀试验研究。结果表明:黄土试样的冻胀率随着荷载增加呈指数形式递减;冻胀率在土样含水率越大时随干密度的变化越大;在自由冻胀状态下,冻胀率随干密度的变化较大,施加荷载后随干密度的变化较小。在荷载水平较高时,冻胀率随着含水率增大而增大,但增加幅度相较于自由冻胀显著降低。对于密度相同、作用荷载相同的土样,含水率增大时冻胀率线性增大。黄土地区的冻胀影响因素中,荷载、含水率、干密度对冻胀影响是依次减小的。对不同含水率、不同干密度以及不同作用荷载条件下的黄土冻胀试验结果进行拟合,得到了可综合考虑含水率、干密度和荷载的冻胀预报模型。

The frost heave is obviously restrained by the load,but it still exists when the load is quite large. At present,there are few studies on the frost heave under high load. To evaluate high load effected frost heave,the frost heaving test of loess samples considering the effect of water content,density and load was carried out,which revealed the close relationship between the frost heaving rate of loess and soil water content,density and load. The tests indicated that,when the upper load of soil sample is small,the frost heave rate decreases greatly compared with that under the natural state. While the load continues to increase,the restraining effect of load increment on frost heave decreases. The frost heave rate decreases exponentially with the increase of load. The freeze-heaving rate of loess varies greatly with the dry density under free freeze-heaving condition. The frost heaving rate of loess samples has little change with the dry density after the load is applied. The greater the water content of soil sample,the greater the change of frost heave with dry density. The frost heave ratio increases linearly with the increase of water content. When the load level is high,the frost heaving rate increases with the increase of water content,but the increase amplitude is significantly lower than that of free frost heaving. Among the factors affecting frost heaving in loess area,the load has greatest influence on frost heaving,followed by the water content and the dry density. Moreover,by fitting the test results of soil samples with different water content and dry density under different loads,the frost heaving prediction model of unsaturated loess is obtained.