酸雨湿干循环作用下百色膨胀土裂隙发育规律及其微观机制

为弄清酸雨与湿干循环共同作用对膨胀土裂隙发育的影响,以广西酸雨重灾区的百色原状膨胀土为对象,室内设置高清照相机观测记录经不同酸雨与湿干循环作用后试验土样的裂隙发展,用Image-Pro Plus(IPP)图像处理软件获取土体裂隙特征参数,并采用扫描电镜(SEM)和X射线衍射法研究试验过程中土样的微结构及化学成分演变.据...

Fissure Development Law and Micro-mechanism of Baise Expansive Soil Under Wet-dry Cycles of Acid Rain

In order to clarify the effect of acid rain and wet-dry cycles on the development of fissures in expansive soil,undisturbed Baise expansive soil in the acid rain disaster area of Guangxi was used as the object of study. The growth condition of fissures in soil samples under different acid rain and wet-dry cycles were observed by using a fixed camera device. Image-Pro Plus image processing software was used to obtain the characteristic parameters of soil fissures,and the evolution of soil micro-structure and chemical composition during the test was studied by scanning electron microscopy and X-ray diffraction.Accordingly,the law of fissures development and the micro-mechanism of expansive soil under acid rain and wet-dry cycles were explored from two aspects: the stress state of aggregate microstructures of expansive soils and the fissures development mechanism. The results show that acid rain promotes the development of fissures in the sample,and the lower the pH value of acid rain,the more evident was the development of fissures. For 17%-18% humidity samples subjected to a pH = 3 and pH = 5 acid environment with a one-time wet-dry cycle,the fissures area ratio increases by 61. 5% and 14. 3%,respectively,as compared to the neutral environment. When the wet-dry cycles increases to 4 and humidity decreases to approximately 15%-16%,the growth rate of the fissures area ratio is 18. 0% and26. 1%,respectively. Therefore,the combined effect of acid rain and wet-dry cycles has a more significant effect on the development of fissures. The micro-comparative analysis shows that the combined action of acid rain and wet-dry cycles causes the rapid loss of cemented materials in soil. The chemical cementation force Pf,electrostatic gravitation Pj,and soil self-weight Pzas well as the average strength of soil sample cross section decrease,resulting in the gradual separation of aggregate microstructures and the formation of new pore due to the reduction of mutual gravitation. With the development of new pore from surface to interior,uneven distribution of water content in the soil sample structure occurs and its dehumidification rate accelerates,which will ultimately lead to the intensification of crack development in the soil.