为解决路基加固工程中传统胶凝材料造价高、生产过程排碳量高的问题,并实现工业固废资源化和高值化利用,以氢氧化钠作为碱激发剂,制备粉煤灰-矿渣-赤泥三元复合胶凝材料,通过无侧限抗压强度(UCS)试验,研究固废基胶凝材料配合比和氢氧化...为解决路基加固工程中传统胶凝材料造价高、生产过程排碳量高的问题,并实现工业固废资源化和高值化利用,以氢氧化钠作为碱激发剂,制备粉煤灰-矿渣-赤泥三元复合胶凝材料,通过无侧限抗压强度(UCS)试验,研究固废基胶凝材料配合比和氢氧化钠掺量对固化土7 d UCS的影响,并利用SPSS软件对UCS结果进行相关性分析,结合SEM-EDS和XRD手段探讨固废基胶凝材料对土体的固化作用机理。结果表明:不同配合比的固化土试样呈现出劈裂破坏、剪切破坏及拉剪复合破坏三种类型;固废基原材料和碱激发剂间的交互作用对固化土UCS有显著影响,当粉煤灰、矿渣、赤泥质量比为1∶3∶1时,固化土7 d UCS最高,可达1.795 MPa;氢氧化钠掺量与UCS之间存在显著的正相关性,相关系数达到0.76;随着固化土内部水化反应的进行,大量生成的水化硅酸钙、水化铝酸钙凝胶相包裹土颗粒并填充颗粒间孔隙,从而显著提升固化土的强度;随着氢氧化钠掺量的增加,其对水化反应的促进作用更为显著,固化土内部微孔和小孔之和的占比逐渐增加,中孔和大孔之和的占比则逐渐降低。展开更多
Water-sand gushing(WSG)disasters in confinedaquifers pose significantchallenges to the utilization of deep underground spaces in soft soil areas.Since few studies have considered the impact of confined aquifer thickne...Water-sand gushing(WSG)disasters in confinedaquifers pose significantchallenges to the utilization of deep underground spaces in soft soil areas.Since few studies have considered the impact of confined aquifer thickness and confinedwater pressure on WSG disasters,a novel visual model test system was developed to investigate the influencingcharacteristics and mechanisms of the two aforementioned factors.The test results showed that the WSG process in clay aquiclude-confinedaquifer composite strata exhibits two prominent stages.First,the sand loss zone expands vertically in an ellipsoid shape.Then,it expands horizontally once the ellipsoid reaches the boundary of the clay layer.The sand loss continues until the overlying clay sinks to the bottom to clog the gushing crack,creating a large sinkhole at the surface.Increasing the confinedaquifer thickness can increase the vertical expansion of the ellipsoid and delay the clay-clogging effects,thereby considerably increasing the severity of sand loss,stratum deformation,and surface settlement.An increase in the confinedwater pressure markedly increases the hydraulic gradient along the seepage path,which contributes to increasing the gushing rates of water and sand.As a result,substantial sand loss occurs before the clay clogs the gushing crack,inducing more cracks and deeper sinkholes at the surface.All the aforementioned results provide insights into the effects of confinedaquifer on WSG disasters in clay aquiclude-confinedaquifer composite strata.展开更多
文摘为解决路基加固工程中传统胶凝材料造价高、生产过程排碳量高的问题,并实现工业固废资源化和高值化利用,以氢氧化钠作为碱激发剂,制备粉煤灰-矿渣-赤泥三元复合胶凝材料,通过无侧限抗压强度(UCS)试验,研究固废基胶凝材料配合比和氢氧化钠掺量对固化土7 d UCS的影响,并利用SPSS软件对UCS结果进行相关性分析,结合SEM-EDS和XRD手段探讨固废基胶凝材料对土体的固化作用机理。结果表明:不同配合比的固化土试样呈现出劈裂破坏、剪切破坏及拉剪复合破坏三种类型;固废基原材料和碱激发剂间的交互作用对固化土UCS有显著影响,当粉煤灰、矿渣、赤泥质量比为1∶3∶1时,固化土7 d UCS最高,可达1.795 MPa;氢氧化钠掺量与UCS之间存在显著的正相关性,相关系数达到0.76;随着固化土内部水化反应的进行,大量生成的水化硅酸钙、水化铝酸钙凝胶相包裹土颗粒并填充颗粒间孔隙,从而显著提升固化土的强度;随着氢氧化钠掺量的增加,其对水化反应的促进作用更为显著,固化土内部微孔和小孔之和的占比逐渐增加,中孔和大孔之和的占比则逐渐降低。
文摘为抑制碱激发胶凝材料(AASM)因水化反应集中、孔隙失水引起的显著自收缩,本文提出采用MgO与Na_(2)SiO_(3)复配为复合激发剂,系统研究其对AASM凝结行为、水化产物组成、孔结构特征、强度发展与自收缩性能的影响规律。通过XRD(X-ray diffraction)与NMR(nuclear magnetic resonance)等手段表征发现:随着复合激发剂中MgO比例的增加,体系内类水滑石相生成显著增多,同时最可几孔径向10~20 nm区间集中,孔隙率有所上升。上述微观结构演变导致以下宏观性能变化:一方面,MgO的弱碱性质延缓了矿渣的水化进程,凝结时间延长,抗压强度随其掺量增加而降低;另一方面,类水滑石相的体积膨胀效应与孔隙率的提高共同缓解了毛细孔应力,使AASM的自收缩显著减小。研究表明,MgO与Na_(2)SiO_(3)在调控反应进程与水化产物组成方面具有协同作用。Na_(2)SiO_(3)提供强碱性环境以保障早期强度发展,而MgO则通过促进膨胀性产物生成,优化孔隙结构,有效抑制收缩开裂。该复合激发策略为兼顾AASM力学性能与体积稳定性提供了可行途径。
基金financedby the National Natural Science Foundation of China(Grant No.52090083)the Shanghai Rising-Star Program(Grant No.23QB1404800).
文摘Water-sand gushing(WSG)disasters in confinedaquifers pose significantchallenges to the utilization of deep underground spaces in soft soil areas.Since few studies have considered the impact of confined aquifer thickness and confinedwater pressure on WSG disasters,a novel visual model test system was developed to investigate the influencingcharacteristics and mechanisms of the two aforementioned factors.The test results showed that the WSG process in clay aquiclude-confinedaquifer composite strata exhibits two prominent stages.First,the sand loss zone expands vertically in an ellipsoid shape.Then,it expands horizontally once the ellipsoid reaches the boundary of the clay layer.The sand loss continues until the overlying clay sinks to the bottom to clog the gushing crack,creating a large sinkhole at the surface.Increasing the confinedaquifer thickness can increase the vertical expansion of the ellipsoid and delay the clay-clogging effects,thereby considerably increasing the severity of sand loss,stratum deformation,and surface settlement.An increase in the confinedwater pressure markedly increases the hydraulic gradient along the seepage path,which contributes to increasing the gushing rates of water and sand.As a result,substantial sand loss occurs before the clay clogs the gushing crack,inducing more cracks and deeper sinkholes at the surface.All the aforementioned results provide insights into the effects of confinedaquifer on WSG disasters in clay aquiclude-confinedaquifer composite strata.
