Experimental Study On The Mechanical Properties Of Cracked Dolomite

The law of crack extension,the destruction of the cracked dolomite and strength analysis process in geotechnical engineering is an important are of reserch.The expansion and interconnection of cracks in the rock during construction is a major hidden danger of engineering safety.The uniaxial compression test,the cleavage test and SEM test based on developed microfissure dolomite in the construction area of Guiyang subway Line 1 below the railway station section of Guizhou province is for the influence of cracks on dolomite mechanical properties.And come to the following conclusions:(1)Analysis of fracture mechanics,The smaller the microcrack inclination angle of the dolomite and the smaller the friction coefficient of the fracture surface,the greater the compressive strength.And the longer the length of dolomite microfracture,the smaller the compressive strength.(2)According to the investigation and analysis of the geological conditions of the sampling area,the micro fissure development of the dolomite strata in this area is high,the lithology is single and the distance from the ground to the surface is short,which meets the sampling requirements of the test.(3)The failure of microfracture dolomite is affected by crack length,fissure dip angle and friction coefficient of fracture surface.The main failure modes are tensile failure and the failure modes of natural cracked dolomite are mainly tensile failure,shear failure along the fracture surface and Tensile shear failure.The uniaxial compressive strength of the fractured dolomite increases with the increase of the friction coefficient,and decreases with the increase of the crack length.With the increase of the fissured angle,it decreases first and then increases,and the strength of the dolomite is the least when the fracture angle is 30°.(4)The greater the dip angle of dolomite microfracture,the greater the tensile strength. The tensile strength is minimum when the fracture angle is 0°and The tensile strength is max when the fracture angle is 90°. But the maximum tensile strength is still less than the tensile strength of intact dolomite.(5)The cracked structure of microfissure dolomite specimens is divided into three forms: root shape,"fog zone" shape and step shape.The elastic modulus and uniaxial compressive strength of the step-shaped rock specimens are the highest and the elastic modulus and uniaxial compressive strength of the root-shaped rock specimens are the lowest.The elastic modulus and uniaxial compressive strength of the rock specimens in the "fog zone" are between the step-shaped rock specimens and the root-shaped rock specimens.