Experimental Investigation On The Stress-strain Characteristics Of Diatomite

Diatomite is a type of special soils formed by the microbial diatom sedimentary. It is widely spread on the surface of the earth. Recently, with the increasing numbers of highway, railway and housing construction projects, this type of geological formation is often encountered. The current study for the diatomite soil is relatively rare; especially in its mechanical related aspects including the stress-strain and strength characteristics of the soil. Therefore, research on the properties of the diatomite in geotechnical mechanics related aspects has important engineering significance.With the diatomite from Yunnan Tengchong area where the highway was being constructed, the related research on the physical and mechanical properties and deformation characteristics was conducted. Uniaxial test based on PIV measurement and triaixal test based on digital image measurement were the primary experimental work conducted in this research.The deformation characteristics of the typical diatomite in the Yunnan Tengchong region were studies by the uniaxial test. Using the PIV technology, the displacement vector and displacement field on the surface of the specimen was obtained at different time. With the obtained node displacement and based on the finite element theory, the strain component and the maximum shear strain field was calculated. By comparing the two types of diatomaceous soils, we found that the main components of both diatomite are silicon dioxide, but their mechanical properties, the color of the specimens and the deformation characteristics were totally different. Firstly, comparing the stress-strain curve of these two types of soil, the maximum stress is different significantly. Secondly, the deformation characteristics of two types of soil were analyzed in the pixel coordinates and obtained the development of of the crack and strain field. Finally, the real displacement and strain were obtained by using the neural network, the pixel coordinates was mapped to the space coordinates.Triaxial test is one of the most important geotechnical experiments. It plays a very important role in determining the strength properties and deformation mechanism of soils. By applying different confining pressure in the triaxial test, the stress-strain relationship curve of the specimen was acquired. Through analyzing the changing trend of the curve, we found the relation between the confining pressure and deformation characteristics. Using the peak values of the stress-strain curve, the shear strength parameters of the specimen were obtained by the Mohr circle theory. The surface deformation images of the specimen were captured by the double cameras. The three dimensional deformation of the specimen was obtained by tracking the white grid corner points of rubber membrane on the surface of the specimen from the obtained images. The deformation and formation of the shear band of the specimen was obtained by drawing the displacement and strain field on the whole surface of the specimen.