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
This study proposes to use the unconfined compressive strength(UCS)and the bender element(BE)tests for determining the strength and the initial small-strain shear modulus of Bangkok soft marine clay improved by cement...This study proposes to use the unconfined compressive strength(UCS)and the bender element(BE)tests for determining the strength and the initial small-strain shear modulus of Bangkok soft marine clay improved by cement and polyester fibers.This study varies the content of admixed cement(1%–20%)and polyester fibers(0–20%),including the curing time(3–28 d)for preparing 360 samples.Moreover,this study uses the Michaelis-Menten kinetics concept to model cement hydration saturation.From the study,it is concluded as follows.The modelled results reveals that at least 10%cement and 1%polyester fiber are recommended to attain the 28-d UCS standards(294 kPa)for highway subgrade materials in Thailand.This also fulfils sustainable construction due to reducing normal-use cement from 20%to 10%.Unfortunately,the addition of polyester fibers into the Bangkok clay with at least 5%cement reduces shear modulus by 1.12–1.32 times.The Abram's relationship between shear modulus and the mixing-water-to-cement ratio is found time-dependent.From the composite theory,the BE detects the polyester fiber zone as a defect in the Bangkok clay(matrix)with 5%–20%cement.So,the 28-d shear modulus in the polyester fiber zone is negative(up to0.034 MPa for 20%fiber),similar to softening phenomenon in concrete cracking(negative stiffness).For the 28-d shear modulus of fiber zone,the optimum cement content is around 2%for the positive influences of polyester fibers.Experimentally,the timedependent normalized UCS for 10%and 20%cement is compatible with other studies,and its development rate increases with the cement content as 0.3017,0.3172 and 0.3204 for 5%,10%and 20%cement,respectively.The 28-d relationship between shear modulus and UCS shows that low-cement soft clay requires high polyester fiber content(5%–20%)to activate UCS improvement.However,the soft clay with enough cement(20%)causes the uniformly distributed UCS improvement.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。
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.
基金allocated by National Science,Research and Innovation Fund(NSRF)King Mongkut's University of Technology North Bangkok(project no.KMUTNB-FF-67-B-44 and KMUTNB-FF-67-B-45)supported by the NSRF through the Program Management Unit for Human Resources&Institutional Development,Research and Innovation(grant no.B40G660036).
文摘This study proposes to use the unconfined compressive strength(UCS)and the bender element(BE)tests for determining the strength and the initial small-strain shear modulus of Bangkok soft marine clay improved by cement and polyester fibers.This study varies the content of admixed cement(1%–20%)and polyester fibers(0–20%),including the curing time(3–28 d)for preparing 360 samples.Moreover,this study uses the Michaelis-Menten kinetics concept to model cement hydration saturation.From the study,it is concluded as follows.The modelled results reveals that at least 10%cement and 1%polyester fiber are recommended to attain the 28-d UCS standards(294 kPa)for highway subgrade materials in Thailand.This also fulfils sustainable construction due to reducing normal-use cement from 20%to 10%.Unfortunately,the addition of polyester fibers into the Bangkok clay with at least 5%cement reduces shear modulus by 1.12–1.32 times.The Abram's relationship between shear modulus and the mixing-water-to-cement ratio is found time-dependent.From the composite theory,the BE detects the polyester fiber zone as a defect in the Bangkok clay(matrix)with 5%–20%cement.So,the 28-d shear modulus in the polyester fiber zone is negative(up to0.034 MPa for 20%fiber),similar to softening phenomenon in concrete cracking(negative stiffness).For the 28-d shear modulus of fiber zone,the optimum cement content is around 2%for the positive influences of polyester fibers.Experimentally,the timedependent normalized UCS for 10%and 20%cement is compatible with other studies,and its development rate increases with the cement content as 0.3017,0.3172 and 0.3204 for 5%,10%and 20%cement,respectively.The 28-d relationship between shear modulus and UCS shows that low-cement soft clay requires high polyester fiber content(5%–20%)to activate UCS improvement.However,the soft clay with enough cement(20%)causes the uniformly distributed UCS improvement.
