Experiment And Mechanism Analysis Of Stress Arch Effect In Sand Pile And Silo

Soil is the product of weathering,transportation and deposition of rock in nature.It is mainly composed of solid particles,liquid and gas.It is a kind of granular material with complex and changeable structure.At present,the classical soil mechanics studies the soil as a continuous medium,which can explain and analyze most of the geotechnical mechanics problems,but the existing continuous medium theory can not explain some phenomena,such as the stress depression at the bottom of sand pile.This is mainly because the traditional soil mechanics ignores the particle characteristics of soil,so it can not show the sensitivity,selforganization behavior,nonlinear response and other characteristics of particles.Sand,which is composed of a large number of particles,is a common substance in nature and people's production and life.Therefore,based on previous studies,this paper selects sand particles of different sizes from the granularity of sand to study the influence of different factors on the formation of stress arch at the bottom of sand pile,and the change of stress arch at the bottom of sand pile with unloading and water content.The research results and conclusions of this article are as follows:(1)The results of stress measurement at the bottom of sand pile show that the degree of stress depression at the bottom will gradually increase with the increase of particle size,roughness of the bottom and the decrease of falling height,and the circular local friction at the bottom of sand pile is more conducive to the formation of stress arch than the central circular local friction.(2)The stress test results of the bottom of the silo show that the stress depression of the bottom decreases with the increase of the diameter of the silo,the roughness of the side wall and the decrease of the particle size.The increase of the friction coefficient of the side wall of the lower part of the silo has a greater effect on the stress distribution of the sand pile,while the change of the roughness of the bottom of the silo has no obvious effect on the stress distribution of the bottom.(3).At the same time,the stress distribution at the bottom of the silo is determined by the initial state.Changing the position of the falling point midway does not affect its final distribution,but the higher the stacking height is,the smaller the influence on the stress depression at the bottom will be.(4)The results of silo unloading test show that the influence of parallel unloading on the bottom stress is more obvious than that of vertical unloading,and decreases with the increase of the distance between the sensor and the unloading hole,but the influence of the number of unloading holes is not obvious;at the same time,with the decrease of the height of unloading holes and the increase of particle size,the disturbance of unloading process on the bottom stress arch is more obvious.(5).The capillary test results of sand pile and silo show that the stress arch at the bottom of sand pile and silo prepared by dry particles first increases and then decreases with the increase of particle moisture content,and the larger the particle size is,the smaller the effect of moisture content is.