摘要
戈壁是广泛分布于我国西北地区的一类特殊土地基,由粗粒、细粒、细粒-粗粒间的相互接触与胶结作用而形成骨架颗粒结构,粒间胶结效应明显,工程性质也不同于一般"土石混合体"。以新疆和甘肃典型戈壁碎石土为对象,完成了戈壁碎石土p H值及可溶盐含量测试,并采用X射线衍射、扫描电子显微镜镜下观察和能谱分析等方法,测试获得了戈壁碎石土胶结矿物成分及其微观结构特征与元素组成,揭示了戈壁碎石土粒间胶结作用力类型与形成机制。根据戈壁碎石土胶结物组分及微细观结构测试结果,分析了戈壁碎石土中黏土矿物晶胞吸附其他胶结物或土颗粒中的阳离子所形成胶结的可能化学结构,建立了戈壁碎石土胶结力作用微观力学模型。以胶结黏土矿物含量为变量,得到了戈壁碎石土抗剪黏聚强度与颗粒胶结力间的关系式,并与现场试验结果对比。结果表明,戈壁碎石土宏观强度来源多样,是盐分胶结及土体胶结物微观晶面上离子键作用的综合结果;戈壁碎石土粒间黏土矿物胶结作用实质是黏土矿物或碳酸钙中非金属原子(如O原子)与土体中金属阳离子相结合而形成离子键,胶结力大小由连接胶结物微观晶面间的多个离子键综合贡献确定。
Gobi is a common geological formation in Northwest China. The gobi gravel soil is made up of the coarse-grained soil, the fine-grained soil, and the bond particles among them. Gobi gravel soil contains soluble salts and exhibits salt cementation, which makes it different from other soil-rock mixtures. In this study, the p H values and the soluble concentrations are tested on gobi gravel soil obtained from Xinjiang Autonomous Region and Gansu Province. The mechanism and the type of salt cementation are analyzed. The microstructure, mineral composition, and bond character of structural soil particles were examined by the techniques of X-ray, SEM, and moss-Bauer spectroscopy to investigate the physicochemical mechanism of bond forces. According to the results on the mineral composition and the microstructure, the possible chemical bond types and the physicochemical mechanism of bond forces were suggested. Finally, the mechanical model and the corresponding formulae of the relationship between the shear parameter and the cementation were established, in which the content and distribution of the cementing agent was suggested as the variables. The cohesion values were calculated and compared to the in-situ shearing test results. The results show that the essence of chemical bond is the formation of the ionic bond by the non-metal atoms in the minerals or Ca CO_3(for example, by the oxygen atom). The magnitude of this chemical bond force is determined by the ionic bonds. In addition, the contribution of the salt cementation must be taken into consideration in the determination of the shearing strength for gobi gravel soil.
出处
《岩土力学》
EI
CAS
CSCD
北大核心
2017年第S2期138-144,共7页
Rock and Soil Mechanics
基金
国家自然科学基金(No.51208480)~~
关键词
戈壁碎石土
胶结力
微观结构
强度参数
gobi gravel soil
bond force
microstructure
strength parameters
