Experimental Study On Mechanical Properties Of Waste Foundry Sand Used As Embankment Filler

The global foundry industry has been developing for about 6000 years and is still developing.Nowadays,the global foundry production is stable at over 100 million tons.During the casting process,approximately one ton of waste foundry sand is generated for each ton of cast metal produced.However,the current recycling rate of waste foundry sand(WFS)is only 20%.WFS has similar properties to coarse-grained soil and can replace coarse-grained soil as embankment filler.However,one of the main obstacles to using WFS as embankment fill is the uncertainty in its engineering properties caused by the content of bentonite.In order to improve the utilization rate of WFS and consume a large amount of WFS,this article conducts a systematic study on the mechanical properties of WFS with different bentonite contents,to provide a theoretical basis for the application of WFS in highway embankments,this study conducted experiments and the results are as follows:(1)By conducting constant head permeability experiments on WFS with different bentonite contents under different cyclic conditions and cycle times,the effects of cyclic conditions,cycle times,and bentonite content on the permeability characteristics of WFS were explored.The influence of dry-wet cycle,axial restricted dry-wet cycle,and freeze-thaw cycle on the permeability coefficient of WFS with different bentonite content is similar:After three cycles,its permeability coefficient can enter a stable stage;Quantify the degree of cyclic influence on the permeability coefficient of WFS as a sensitivity index A’,By comparing A’,it can be concluded that the permeability coefficient of WFS with higher bentonite content is greatly affected by cycling,with the greatest impact of dry-wet cycling on the permeability coefficient and the least impact of freeze-thaw cycling.(2)By conducting one-dimensional consolidation compression(rebound)tests on WFS with different bentonite contents,the influence of bentonite content on the compression(rebound)characteristics of WFS was explored.WFS with higher bentonite content has smaller compression modulus and more compressibility;WFS with higher bentonite content has smaller rebound modulus and more Resilience;By calculating the compressibility coefficient a,it can be judged that WFS in the market today belongs to medium compressibility materials;(3)By conducting one-dimensional compression creep tests on WFS with different bentonite contents,the influence of bentonite content on the long-term compression characteristics of WFS was explored.After three weeks of compression,when the bentonite content increases from 0%to 12.9%,ε_V increased by 364%;By calculating the secondary consolidation coefficient of WFS with different bentonite contents,the total settlement formula of the embankment affected by the bentonite content is obtained.(4)By conducting triaxial consolidation drainage tests on WFS with different bentonite contents,the influence of bentonite content on the strength characteristics of WFS was explored.The WFS strength index cohesion c increases linearly with the increase of bentonite content.This is because as the content of bentonite increases,fine particles fill the WFS pores,the particle spacing decreases,and the force between particles increases.At the same time,the particle bonding effect strengthens,leading to an increase in cohesion c;WFS strength index internal friction angleφincreases linearly As the content of bentonite increases,but the increase ofφis very small,This is because as the content of bentonite increases,the specific surface area of particles increases,more contact points between soil particles per unit area are generated,leading to an Slight increase in cohesion c.(5)By conducting triaxial creep tests on WFS with different bentonite contents,the influence of bentonite content on the creep characteristics of WFS was explored.Due to the effect of creep deformation,When the content of WFS bentonite increases from 6.9 to 12.9%,the Strength of WFS decreases by 40%;Derive a three parameter empirical creep model considering the influence of bentonite content for predicting WFS creep deformation,And the calculated values of the model were compared with the measured values in the experiment,and the results showed that the model was effective within the error range of 27%.