The present work aimed to study the effect of slurry conditioning on flocculant-aided filtration of coal tailings by the analysis of filtration kinetics and filter cake structure.Laboratory filtration tests of the coa...The present work aimed to study the effect of slurry conditioning on flocculant-aided filtration of coal tailings by the analysis of filtration kinetics and filter cake structure.Laboratory filtration tests of the coal tailings showed that both the shear rate and agitation time have significant effects on filtration rate and cake moisture.Moderate agitation at the shear rate of 92 s^-1 was favorable for fast filtration,but high cake moisture was encountered.The low-field 1H nuclear magnetic resonance(NMR)measurements of the filter cake showed that the slurry conditioning has a significant effect on the residual water in large pores and a negligible effect on the residual water in small pores.The X-ray micro-tomography(XRM)measurements indicated that the filter cake formed at the shear rate of 92 s^-1 has more macro-pores and higher porosity than that formed at the shear rate of 53 s1,hence more residual water was entrapped in filter cake.The slurry conditioning in the presence of flocculant will change the structure of filter cake and affect the filtration performance.There was a paradox between fast filtration rate and low filter cake moisture.The findings enable better understanding of the effect of slurry conditioning on flocculant-aided filtration of coal tailings.展开更多
Soil conditioning is essential for addressing the stratum applicability problem of earth pressure balance(EPB)shields.Under high water pressures,EPB shields spew water and soil when excavating coarse-grained strata.Ty...Soil conditioning is essential for addressing the stratum applicability problem of earth pressure balance(EPB)shields.Under high water pressures,EPB shields spew water and soil when excavating coarse-grained strata.Typically,foam combined with polymers and slurry is used to solve spewing.However,in current techniques,slurry,foam,and the other agents are mixed with soil separately,their synergistic effect is seldom realized.In this study,an anionic surfactant was used to foam in bentonite slurry to form bubble-slurry to maximize the synergy between bubbles and slurry.The slump,volume stability,and permeability test of bubble-slurry-conditioned sand was conducted to examine the conditioning effect,and the stratum applicability of bubble-slurry was determined from the perspective of permeability.It was found that the conditioning effect of bubble-slurry in coarse gravel soil was excellent and could expand the applicability of EPB shields.The main stabilization mechanism of bubble-slurry is that bentonite particles provide a space barrier for bubbles.And three seepage modes of bubble-slurry-conditioned sand were innovatively defined,and the occurrence conditions of the three seepage modes were analyzed according to the permeability coefficient of sand,initial dynamic shear force of bubble-slurry,and hydraulic gradient.展开更多
为解决土压平衡盾构及车站基坑开挖过程中产生大量废弃粉质黏土的现状,提出一种利用废弃粉质黏土调制泥浆改良盾构渣土的新方案。以沈阳地区粉质黏土为研究对象,通过添加不同的外加剂对粉质黏土泥浆进行改性,研究泥浆土水比、外加剂种...为解决土压平衡盾构及车站基坑开挖过程中产生大量废弃粉质黏土的现状,提出一种利用废弃粉质黏土调制泥浆改良盾构渣土的新方案。以沈阳地区粉质黏土为研究对象,通过添加不同的外加剂对粉质黏土泥浆进行改性,研究泥浆土水比、外加剂种类及掺量变化对改性泥浆的漏斗黏度、酸碱度、滤失量和胶体率的影响。通过扫描电镜(scanning electron microscope, SEM)研究了粉质黏土泥浆的微观改性机理。结果表明:纯粉质黏土泥浆自身稳定性差、泌水量大,无法有效改良渣土;碳酸钠和焦磷酸钠对粉质黏土泥浆的改性效果较好,合理掺入量为1%~3%;改性后的粉质黏土泥浆可有效改良砾砂地层渣土的塑流性,合理粉质黏土泥浆土水比为9∶11、焦磷酸钠掺量为3%,注入比为24%~28%。研究结果验证了粉质黏土泥浆用作盾构渣土改良剂的可行性,为废弃粉质黏土再利用提供了新思路。展开更多
基金the Natural Science Foundation of Jiangsu Province(BK20180657)。
文摘The present work aimed to study the effect of slurry conditioning on flocculant-aided filtration of coal tailings by the analysis of filtration kinetics and filter cake structure.Laboratory filtration tests of the coal tailings showed that both the shear rate and agitation time have significant effects on filtration rate and cake moisture.Moderate agitation at the shear rate of 92 s^-1 was favorable for fast filtration,but high cake moisture was encountered.The low-field 1H nuclear magnetic resonance(NMR)measurements of the filter cake showed that the slurry conditioning has a significant effect on the residual water in large pores and a negligible effect on the residual water in small pores.The X-ray micro-tomography(XRM)measurements indicated that the filter cake formed at the shear rate of 92 s^-1 has more macro-pores and higher porosity than that formed at the shear rate of 53 s1,hence more residual water was entrapped in filter cake.The slurry conditioning in the presence of flocculant will change the structure of filter cake and affect the filtration performance.There was a paradox between fast filtration rate and low filter cake moisture.The findings enable better understanding of the effect of slurry conditioning on flocculant-aided filtration of coal tailings.
基金funded by National Key R&D Program of China (2022YFC3202705)the Fundamental Research Funds for the Central Universities (B200203081)the Postgraduate Research and Practice Innovation Program of Jiangsu Province (KYCX20_0436).
文摘Soil conditioning is essential for addressing the stratum applicability problem of earth pressure balance(EPB)shields.Under high water pressures,EPB shields spew water and soil when excavating coarse-grained strata.Typically,foam combined with polymers and slurry is used to solve spewing.However,in current techniques,slurry,foam,and the other agents are mixed with soil separately,their synergistic effect is seldom realized.In this study,an anionic surfactant was used to foam in bentonite slurry to form bubble-slurry to maximize the synergy between bubbles and slurry.The slump,volume stability,and permeability test of bubble-slurry-conditioned sand was conducted to examine the conditioning effect,and the stratum applicability of bubble-slurry was determined from the perspective of permeability.It was found that the conditioning effect of bubble-slurry in coarse gravel soil was excellent and could expand the applicability of EPB shields.The main stabilization mechanism of bubble-slurry is that bentonite particles provide a space barrier for bubbles.And three seepage modes of bubble-slurry-conditioned sand were innovatively defined,and the occurrence conditions of the three seepage modes were analyzed according to the permeability coefficient of sand,initial dynamic shear force of bubble-slurry,and hydraulic gradient.
文摘为解决土压平衡盾构及车站基坑开挖过程中产生大量废弃粉质黏土的现状,提出一种利用废弃粉质黏土调制泥浆改良盾构渣土的新方案。以沈阳地区粉质黏土为研究对象,通过添加不同的外加剂对粉质黏土泥浆进行改性,研究泥浆土水比、外加剂种类及掺量变化对改性泥浆的漏斗黏度、酸碱度、滤失量和胶体率的影响。通过扫描电镜(scanning electron microscope, SEM)研究了粉质黏土泥浆的微观改性机理。结果表明:纯粉质黏土泥浆自身稳定性差、泌水量大,无法有效改良渣土;碳酸钠和焦磷酸钠对粉质黏土泥浆的改性效果较好,合理掺入量为1%~3%;改性后的粉质黏土泥浆可有效改良砾砂地层渣土的塑流性,合理粉质黏土泥浆土水比为9∶11、焦磷酸钠掺量为3%,注入比为24%~28%。研究结果验证了粉质黏土泥浆用作盾构渣土改良剂的可行性,为废弃粉质黏土再利用提供了新思路。
