干湿循环作用下膨胀土改性前后宏观裂隙性及微观结构演化特征分析

Study of the Fissures and Microstructure Under Dry-wet Circulation of Expansive and Modification Soil

膨胀土具有典型的裂隙性,对工程性质影响巨大。研究了干湿循环作用下,素土和改性土的宏观裂隙性和微观结构演化特征,揭示了干湿循环作用下试样宏观裂隙和微观结构的发育规律,研究了离子土固化剂对膨胀土裂隙性的抑制作用,并简单探讨了其改性机理。研究结果表明:干湿循环作用下,膨胀土裂隙性呈现明显的缓慢增长、迅速增长和缓慢下降3个阶段;试样的微观结构从密实状态逐渐变到松散状态,黏土矿物片由卷曲片状逐渐变为单片状,卷曲程度降低,试样的结构变松散;经过离子土固化剂改性后,试样裂隙的峰值面积可降低20%,裂隙宽度降低值可达到30%;黏土矿物卷曲片状的卷曲程度降低,黏土矿物片开始出现“黏土片-片聚体-微聚体”的团聚现象,出现较大的团聚体。说明离子土固化剂能够改善膨胀土的黏聚性和水稳性,能够有效抑制膨胀土的裂隙发育,改善其工程性质。

Expansive soil has the characteristics of developing fissures,and it has great influence on its engineering geological properties.In this paper,it analyzed the macrostructure and microstructure of samples under dry-wet circulation.It reveals the development pattern of sample cracks under the action of dry wet cycles,and it studies the suppression of expansive soil cracking by ionic soil stabilizer,and briefly explored its modification mechanism.The main research conclusions were as follows,under the action of dry wet cycles,the fissures of expansive soil exhibit three distinct stages:slow growth,rapid growth,and slow decline.The dominant microstructure constituents of these two types of samples were flake structure and flat structure,and the connection mode of clay minerals were“surface-surface”and“edge-surface”,so the microstructure is flocculation structure.Under the effect of dry-wet circulation,the microstructure of soil samples varied from compaction state to the loose state gradually.After ionic soil stabilizer modification,peak value of the sample fracture area can reduce 20%and the reduction in crack width can reach 30%.The state of clay mineral changed from curled sheet gradually into single chip,the reunion phenomenon,which contained the process of"the clay-pills polymers-micro polymers",occurred and larger reunion piece appeared.Furthermore,the addition of the ISS caused the beneficial changes in the cohesiveness and water stability,and it can effectively suppress the development of cracks in expansive soil and improve its engineering properties.