Effect And Energy Consumption And Transference Rule Of Red Sandstone Under Multiple Impact

In our country red sandstone soils has very widely distribution.Red sandstone soils is widely used to backfill foundation,we usually use impaction load methods to reinforce the foundation, it has significant strengthening effect.But the theoretical study of the impaction load methods for reinforcing red sandstone soils foundation is lag behind.This paper use the refitted manual compaction text equipment to do impact expriment on red sandstone soil,research the effect in soil column which surrounded by impact point under three-point tamping and four-point tamping of multipoint tamping,and the energy transfer and energy consumption law in soil column which surrounded by impact point,the main conclusions are as fallows:(1) Under multipoint tamping the density in soil column which surrounded by impact point decrease with the increase of the distance from the center of tamping point on the horizontal direction,on the vertical direction the density first increase then decrease with the increase of depth; on the horizontal direction the shear strength decrease with the increase of the distance from the center of tamping point,the increase of fall distance will significantly enhanced the shear strength of soil column.(2) Under multipoint tamping the average density in soil column which surrounded by impact point increase with the increase of the total energy,in the end the average density will become a constant value;the average density of the upper soil and the lower soil will has a turning point,at first the average density of upper soil is greater than the average density of lower soil,then the average density of upper soil will less than the average density of lower soil.(3) Under three-point tamping and four-point tamping energy along horizontal direction and vertical direction increase with the increase of the fall distance and the impact number,and the energy growth on vertical direction is greater than the growth on horizontal direction;when has the same impact number,the greater number of single tamping energy is,the more energy will into the vertical direction;when has the same number of single tamping energy,with the increase of impact number will distribute more energy into the horizontal direction.(4) Under three-point tamping and four-point tamping the energy absorbed by soil increase with the total energy increase,but there is a limit number of energy which soil canabsorbed;under three-point tamping the energy use rate is less than 40%, the limit number of energy which soil can absorbed is no more than 40% of the total energy;under four-point tamping the energy absorption rate is less than 50%, the limit number of energy which soil can absorbed is no more than 50% of the total energy.The research results have some theory and reality significance on enriching foundation reinforcement theory and guiding the practice and design of foundation reinforcement under impact loading.