Experimental Study On Deformation Characteristics Of Rockfill Constituted By Mudstone Excavation Materials

With the advancement of the well-off society in an all-round way,the southwestern region,where social and economic development is relatively backward,has gradually stepped a period of new economic construction and development.The red bed in the southwest is the most widely distributed and representative in China.As an unavoidable engineering material in the construction of southwestern engineering projects,the deformation characteristics of red bed mudstone are particularly important.Therefore,this paper starts with the analysis of the physical and mechanical characteristics of the field rock samples,and makes some research on the morphological characteristics and load deformation characteristics of the rockfill constituted by mudstone excavation materials.The main studies and conclusions are as follows:(1)By using standard samples made from the original rock,experimental study on physical properties and uniaxial compression and triaxial compression mechanical properties of mudstone was carried out,which shows that mudstone exhibits fracture-type hard and brittle characteristics and low uniaxial compressive strength.(2)By using standard samples,creep test study on deformation characteristics of saturated mudstone with lateral restraint under different axial loads was carried out,which shows that the axial deformation of mudstone samples under vertical load in natural and saturated state is dominated by instantaneous deformation;in the saturated and loading condition,the expansion deformation of mudstone samples is controlled by the stress when the stress is greater than the critical stress and is controlled by the crack distribution when the stress is less than the critical stress.(3)By using the particles of mudstone rockfill obtained from engineering site,digital image analysis on the characteristics of fractal distribution and morphological composition of particle groups was carried,which shows that the fractal structure of the scaled particle groups is obvious and the stability of the rockfill with more obvious fractal structure is higher;the mass fractal dimension can reflect the gradation of rockfill,and the size of rockfill is more discrete with the increase of the mass fractal dimension,and vice versa;when the particle diameter is less than 20mm,the roundness and contour fractal dimension of different size groups do not have positive and negative correlation,and the morphological characteristics of particles perform similar;with the particle size increasing,the particle shape becomes more irregular,at the condition that the particle size interval is large.(4)By using the particles of mudstone rockfill through three different scaling methods,creep test study on deformation characteristics of saturated mudstone rockfill with lateral restraint under load was earried out,which shows that the particle size between 2?5mm is not easily broken;the morphological characteristics of rockfill particles range before and after the experiment between the square and the 3:1 ellipse,and the particle morphology is relatively stable;the mudtone rockfill has similar time-deformation curve to the mudstone sample in the saturated and loading condition,the main deformation in the whole process is caused by the instantaneous deformation of loading and adding water,and the saturation of the rockfill damages its stability.(5)By using the particles in uniform large size taken from construction site,experimental study on the variation law of particle morphology and the structure characteristics and the law of deformation of the rockfill with lateral restraint was earried out,which shows that the main reason for the deformation of the rockfill is the destruction of the spatial structure of the particles,and the secondary cause is the destruction of the particles;the deformation of the rockfill can be predicted by logarithmic mathematical model;the design of gradation parameters of the rockfill in construction can refer to the gradation index of the third level of uniform large particles rockfill after loading experiment.