湿陷性黄土在卸荷状态下的湿陷量与恒压下不同,通过试验从宏观与微观角度研究了卸荷作用下黄土湿陷量与微观结构变化情况.对铜川地区黄土进行湿陷性试验,测得不同埋深处恒压与卸荷的湿陷性系数,对比恒压与卸荷、湿陷系数的差异性,并结合电镜扫描(scanning electron microscope,SEM)与图像分析系统 PCAS(particles and cracks analysis system)观测分析湿陷性黄土微观结构变化,得到不同埋深、卸荷量下微观参数孔隙面积占比、概率熵与平均形状系数等变化特征.结果表明:卸荷将有效提高湿陷起始压力,减少湿陷性的发生,相较于恒压条件下改变了湿陷性黄土孔隙面积、颗粒分布、排列方式等;微观结构主要以片状和蜂窝结构为主,随埋深与卸荷量增加,孔隙由疏到密、细小孔隙占比增加;概率熵逐渐增大、颗粒排列混乱且定向性变差,均一化程度降低;卸荷作用下黄土的湿陷系数、埋深与卸荷量有很强的相关性.
Unloading Test of Wet Sinking Loess and Its Microstructure
The changes of wetting and microstructure of loess under unloading from macroscopic and microscopic viewpoints was in-vestigated.The wet subsidence test was conducted on the loess in Tongchuan area,and the wet subsidence coefficients of constant pres-sure and unloading were measured at different burial depths,and the differences between constant pressure and unloading and wet sub-sidence coefficients were compared,and the microstructural changes of wet subsided loess were analyzed by combining SEM(scanning electron microscope)and PCAS(particles and cracks analysis system)observations,and the characteristics of changes in microscopic parameters such as pore area percentage,probability entropy and average shape coefficient were obtained at different burial depths and unloading.The results show these as follows.Unloading will effectively increase the initial pressure of wet sink and reduce the occur-rence of wet sink,and change the pore area,particle distribution and arrangement of wet sink loess compared with the constant pres-sure condition;the microstructure is mainly lamellar and honeycomb structure,with the increase of burial depth and unloading amount,the pore space increases from sparse to dense,and the percentage of fine pore space increases;the probability entropy gradually increa-ses,the particle arrangement becomes chaotic and poorly oriented,and the degree of homogenization.There is a strong correlation be-tween the wetting coefficient,burial depth and unloading volume of loess under the unloading effect.
万方数据
维普
