浸水作用下二灰黄土的稳定性

Stability of lime-fly ash loess under action of water immersion

对二灰黄土进行了不同干湿循环次数和不同浸水时间2种浸水作用下的强度试验和压汞试验,分析了二灰黄土水稳定性。分析结果表明:二灰黄土强度较高,7d龄期无侧限抗压强度可以达到1.33MPa;随着干湿循环次数的增加,二灰黄土强度出现衰减,经过2次干湿循环后二灰黄土强度就大幅度降低,并趋于稳定,经过10次干湿循环后二灰黄土无侧限抗压强度和抗剪强度降低幅度分别为42.8%、47.4%;随着干湿循环次数的增加,二灰黄土的总孔隙体积呈线性增加,经过10次干湿循环后二灰黄土的总孔隙体积从0.200 1mL·g-1增大到0.238 3mL·g-1,增加了19%;在干湿循环过程中,不同孔径孔隙体积变化规律不同,大孔隙体积呈线性增加,小孔隙体积和微孔隙体积基本上没有发生变化;随着浸水时间的延长,二灰黄土强度出现衰减,经过2d浸水后强度产生大幅度降低,并随着浸水时间继续延长强度逐渐趋于稳定,经过4d浸水后二灰黄土无侧限抗压强度和抗剪强度降低幅度分别为33.6%、54.7%。可见:在石灰与粉煤灰掺量较小的情况下,水对二灰黄土的强度有明显的弱化作用,浸水作用可导致二灰黄土强度降低,干密度略微减小,总孔隙体积增大,但相对于未改性黄土,二灰黄土仍然具有较高的强度和较好的水稳定性,可以在黄土地区作为道路的底基层推广使用。

The strength tests and mercury injection tests on lime-fly ash loess under 2 actions of water immersion with different times of wetting-drying cycle and different saturation times were conducted, and the stability of lime-fly ash loess was analyzed. Analysis result shows that the unconfined compressive strength of lime-fly ash loess at 7 d is higher and about 1.33 MPa. With the increase of the times of wetting-drying cycle, the strength of lime-fly ash loess decays. After 2 times of wetting-drying cycle, the strength falls drastically and tends to be stable. After 10 times of wetting-drying cycle, the unconfined compressive strength and shear strength of lime-fly ash loess decrease by 42. 8% and 47. 4%, respectively. With the increase of the times of drying-wetting cycle, the total void volume of lime-fly ash loess increases linearly. After 10 times of wetting-drying cycle, the total pore volume of lime-fly ash loess increases from 0. 200 1 mL·g^-1 to 0. 238 3 mL·g^-1 , which is equivalent to 19%. During drying-wetting cycle, the pore diameter variation rules are different, the large void volume increases linearly, but the small and micro void volumes do not change basically. With the increase of saturation time, the strength of lime- fly ash loess decays, decreases significantly after 2 d water immersion, and gradually stabilizes with the continuous immersion. After 4 d water immersion, the unconfined compressive strength and shear strength of lime-fly ash loess decrease by 33.6% and 54.7%, respectively. The result indicates that when the contents of lime and fly ash are less, the water can weaken the strength of lime-fly ash loess obviously, the action of water immersion can lead to the decrease of strength, the dry density slightly decreases, and the total pore volume increases. But compared with the unmodified loess, the lime-fly ash loess has higher strength and better water stability, and can be used as road subgrade in loess area. 7 tabs, 21 figs, 26 refs.