针对黏性土胶质联结特征的SEM-EDS试验研究

Experimental study of SEM-EDS for cementation bond characteristics of Zhanjiang clay

采用"整区→微区→胶结点"的逐步分区测试方法,对湛江原状黏土与重塑土开展SEM-EDS试验研究,观察土体微观结构的胶质联结特征,确定胶结物质的元素组分及其空间分布状态,建立微观结构-化学物质-宏观力学行为的相互关系与灵敏性分析。结果表明,土的基本性质很大程度上取决于微观层面的颗粒联结特征。湛江黏土的结构单元实际上是以许多黏土矿物薄片堆叠而成的黏土畴,开放式的絮凝结构加上以游离氧化铁为主要成分的胶质联结特征是导致湛江黏土具有高灵敏性、强结构性的根本原因。当应力水平超过土体的结构屈服应力后,力学性能迅速劣化,结构单元体逐步转为联结强度弱,分散性强的凝聚体或叠聚体。研究还表明,土的颗粒联结强度、结构形态特征及其对结构强度的贡献是导致原状土与重塑土性质差异的本质,天然状态下的湛江黏土土性受控于微观结构特征,而重塑土土性受控于黏土矿物颗粒本性。

In order to observe microstructure cementation bond, determine the element composition and its spatial distribution microstructure, a series of SEM-EDS tests for Zhanjiang clay using the method of‘whole area to micro zone, consolidation point’ are carried out. Moreover, the relationship between microstructure, chemical composition and mechanical behavior is discussed. The results show that the soil properties depend largely on the particles connection performance. In fact, Zhanjiang clay structure unit is actually many clay mineral plates stacked clay domain;the open flocculation structure combined with the free iron oxide as the main component of Zhanjiang clay is as a result of the cementation bond characteristics of the basic reason of the high sensitivity, strong structure. When stress level exceeds the structural yield stress, mechanical performance degrades rapidly; the structural unit body gradually transfers into aggregation and lamina of weak connection strength and strong dispersion. Studies also show that connection strength of soil particles, the structure morphology and its contribution to the structural strength are the essences of undisturbed soil and remolded soil properties difference;Zhanjiang natural clay is controlled by microstructure features, however, the remolded soil is controlled by clay mineral particles features.