Study On The Microstructure Of High-expansion And Easily Collapsed Tuff In Laochang Lead Mine In Lancang

Tuff is a kind of special soft rock,which has the property of water swelling and collapse of soft rock.It is a thorny key issue in engineering construction.The rapid expansion and collapse of tuff is closely related to its structural characteristics.This paper takes the high-expansion tuff of cerite as the research object,taking the microstructure as the starting point,mainly from the tuff composition,micromorphology,pore size distribution characteristics,and water Microscopic changes in rock behavior and microscopic mechanism of collapse collapse have been experimentally studied systematically on the microscopic characteristics of tuff.The main achievements and understanding of the thesis are:(1)Study on the physical basis of the collapse of tuff collapse: The mineral composition of the tantalum tuff is mainly clay minerals less than 2mm and brittle minerals such as quartz,feldspar and calcite,among which the content of clay minerals exceeds 50%.Up to 90% can be achieved with three common types of montmorillonite,kaolinite and illite.The presence and content of clay minerals are important influencing factors for the collapse of water swelling in tuffs.(2)Experimental study on the microstructure of tuff: The microstructure of tuff under the electron microscope is mainly lamellar structure,and the lamellar layer is mostly curled.The lamination of the clad layer is actually the microscopic appearance of the clay mineral,and the curl of the lamination increases.The pores and specific surface area of tuffs promote the entry and reaction of water.The classification of the microscopic pore types of tuffs indicates that the pore types of tuffs are mainly divided into three types: intragranular pores,intergranular pores and microfractures;and tuffs are under microscopic scale.The three-dimensional pore throat configuration can be divided into four types: burrowing,diverging,"one" and "V",and the relative development of the pore throat configuration provides a basis for the connection of pores.(3)Characteristics of the pore structure of tuff: Indirect quantitative analysis of the pore structure of tuff is performed by low-temperature nitrogen adsorption and highpressure mercury injection experiments.Experiments show that although the appearance of tuff looks relatively dense,its pores are relatively developed.Its pore size distribution is dominated by mesopores,followed by macropores,and also contains a certain amount of micropores.A large number of developed pores increase the pores of tuff.Degrees and specific surface area provide access to water and accelerate the softening of tuff.(4)The collapse mechanism of tuff: The effect of microstructure on the collapse of tuff is mainly the micro-laminate structure and the complex and numerous pore structure of tuff,the lamellar structure and the complex structure of pore structure,both of which increase The porosity and specific surface area of tuff are favorable for the entry and circulation of water and accelerate the collapse of tuff.In addition,the strong hydrophilicity of clay minerals,the exchange of ions,and the dissolution mechanism of easily soluble minerals are also important factors affecting the collapse of tuffs.