Experimental Study On Bonding Characteristics And Mechanism Of Malan Loess

As a weak diagenetic,underconsolidated quaternary deposit,loess is integrated by different graded particles,which connected by various cement.Loess`cementation can be divided into three types,which are the bonding of cemention,the bonding of bound water and the flocculation of metal ions.Under the condition of low water content,the intergranular structure of the loess skeleton is relatively strong.so when the specimen is subjected to a certain external load,the interparticle structure will not break down.However,during the humidification,the inter-granular binding force of the loess decreases rapidly.At this time,under the action of the load,the intergranular structure will be deformed and destroyed.In engineering practice,the special water properties of loess will cause its strength decreasing rapidly,leading to a series of geological disasters.Therefore,the study of the cementation characteristics of loess is the basis and prerequisite for studying and solving the engineering geological problems of loess regions.On the basis of a large number of previous studies,this paper taking loess of different regions as research objects,studied and analyzed the three above-mentioned intergranular connection.Firstly,the type of loess cementation and the distribution characteristics,evolution mechanism of the main cementation in the loess region were summarized by literature research.The results show that the composition of cemented loess is complex,including clay minerals,calcium carbonate crystallites and a small amount of organic matter.With the change of time and space,the content of cement has showed obvious changes in different regions.Secondly,the determination of the bound water content in different regions of the Malan loess at different humidity levels was carried out by means of isothermal adsorption and Liquid-plastic limit combined determination.The bound water adsorption characteristics of loess under different humidity levels in different regions were studied.Combined with the shear strength test,the relationship between loess`strength and various types of bound water were revealed.The results showed that the saturated air-dried samples had firmer interparticle bonds than the direct-humidified samples.Different types of bound water have different effects on the loess`strength characteristics.Thirdly,The relative concentration and Zeta potential of loess suspensions under different types of metal soluble salts?NaCl,CaCl₂,AlCl₃?were measured by Suction method,Zeta potential test,flocculation method.The surface coordination theory was used to analyze the bonding mechanism between different metal cations and loess particles.The results show that Ca²⁺and Na⁺in the loess suspension can reduce the absolute value of the Zeta potential but can not change the surface electrical properties of the soil particles.Al³⁺can change the surface electrical properties of loess particles,so that the loess suspension can be changed from anion suspension system to cation suspension system.The valence and concentration of metal ions have a very important influence on the flocculation of soil particles in loess suspensions.With the increase of the cation concentration,the flocculation time of soil particles decreases significantly.The flocculation ability of high-valence ions is much greater than that of low-valence ions.