降低黄土液化势的改性技术分析
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摘要
提出针对低黏性粉土等易液化土样采用酸化学改性方法。改性后的低黏性土液化试验曲线表明,在50~80kPa动应力下孔隙水压力上升很小,应力降低很小。该方法能达到有效降低液化势,提高土体强度的目的。
Loess in China are mainly distributed in the terraces of the Yellow River,including in the Gansu,Ningxia,Inner Mongolia,and Shanxi provinces,covering an area of 6.4×106 km2 that accounts for about 6.6% of China's territory.The loess in western Gansu belongs to the class of unsaturated loess with a wide distribution range.Formed near the sand source,the eolian loess mainly includes sand loess,low-viscosity loess,and clay loess.Low-viscosity loess in Gansu has large thickness,with development pores and aerial weak cementation,which under dynamic loading is likely to produce large settlement deformation.It also has strong water-collapse characteristics and a tendency toward liquefaction.Such material brings arduous engineering challenges and foundation treatment construction problems.Low-viscosity loess in general has weak alkaline and poor cementation strength,with large deformation under a force dynamic.Because underground water easily uplifts after loading,liquefaction is a serious problem.Acid-modified and chemically modified technology can effectively improve the loess seismic subsidence problem.The principle of acid-modified loess chemical modification is using phosphoric acid and a weak acid as a loess acidification treatment,considering that the loess formed in a dry climate gives priority to calcium carbonate.Then,other salts(Boric salt)are added to form the cementation bonds such as boron bridge bonding and hydrogen bonding.Filling material(calcium salt)is added to adjust the ratio of particle size to reduce the liquefaction potential.The acid-modified method reduces the low-cohesion loess' ability to liquefy.The liquefaction test showed that under50~65kPa dynamic stress,the modified loess had a very slow rise in pore water pressure,a very small deformation,and almost no stress reduction.Under a dynamic stress of 65 kPa,its liquefied deformation was no more than 0.2%,corresponding to resistance to an IX-level earthquake.The following ratio was confirmed:10% ~30% calcium,6% ~13% boron material with 3%phosphoric acid.If a higher level of anti-seismic resistance is required,add 8%~13% of boron material.The acid-modified method creates no chemical toxicity,and the price of the raw boron material is lower than that of the lime cement.Therefore,this method has some economic and social benefits.
Loess in China are mainly distributed in the terraces of the Yellow River,including in the Gansu,Ningxia,Inner Mongolia,and Shanxi provinces,covering an area of 6.4×106 km2 that accounts for about 6.6% of China's territory.The loess in western Gansu belongs to the class of unsaturated loess with a wide distribution range.Formed near the sand source,the eolian loess mainly includes sand loess,low-viscosity loess,and clay loess.Low-viscosity loess in Gansu has large thickness,with development pores and aerial weak cementation,which under dynamic loading is likely to produce large settlement deformation.It also has strong water-collapse characteristics and a tendency toward liquefaction.Such material brings arduous engineering challenges and foundation treatment construction problems.Low-viscosity loess in general has weak alkaline and poor cementation strength,with large deformation under a force dynamic.Because underground water easily uplifts after loading,liquefaction is a serious problem.Acid-modified and chemically modified technology can effectively improve the loess seismic subsidence problem.The principle of acid-modified loess chemical modification is using phosphoric acid and a weak acid as a loess acidification treatment,considering that the loess formed in a dry climate gives priority to calcium carbonate.Then,other salts(Boric salt)are added to form the cementation bonds such as boron bridge bonding and hydrogen bonding.Filling material(calcium salt)is added to adjust the ratio of particle size to reduce the liquefaction potential.The acid-modified method reduces the low-cohesion loess' ability to liquefy.The liquefaction test showed that under50~65kPa dynamic stress,the modified loess had a very slow rise in pore water pressure,a very small deformation,and almost no stress reduction.Under a dynamic stress of 65 kPa,its liquefied deformation was no more than 0.2%,corresponding to resistance to an IX-level earthquake.The following ratio was confirmed:10% ~30% calcium,6% ~13% boron material with 3%phosphoric acid.If a higher level of anti-seismic resistance is required,add 8%~13% of boron material.The acid-modified method creates no chemical toxicity,and the price of the raw boron material is lower than that of the lime cement.Therefore,this method has some economic and social benefits.
引文
[1]王兰民.黄土动力学[M].北京:地震出版社,2003:12-82.WANG Lan-min.Loess Dynamics[M].Beijing:Seismological Press,2003:12-82.(in Chinese)
[2]徐实,杨有海,耿煊,等.石灰改性黄土的强度特性试验研究[J].兰州交通大学学报,2007,25(6):97-100.XU Shi,YANG You-hai,GENG Xuan,et al.Lime Modified Loess Experimental Study of the Strength Characteristics[J].Journal of Lanzhou Jiaotong University,2007,25(6):97-100.(in Chinese)
[3]曾正中,马力鹤,南忠仁.粉煤灰对垃圾填埋场黄土垫层的改性试验[J].环境工程,2009(4):105-108.ZENG Zheng-zhong,MA Li-he,NAN Zhong-ren.Loess Cushion of Modified Fly Ash on the Landfill Test[J].Journal of Environmental Engineering,2009(4):105-108.(in Chinese)
[4]王峻,王谦,王平,等.粉煤灰掺入量对改性黄土动本构关系的影响[J].岩土工程学报,2013,35(增1):156-160.WANG Jun,WANG Qian,WANG Ping,et al.Effect of Adding Amount of Flyash on Dynamic Constitutive Relationship of Modified Loess[J].Chinese Journal of Geotechnical Engineering,2013,35(S1):156-160.(in Chinese)
[5]邓津,王兰民.非饱和黄土改性处理方法:中国,103184052A[P].2013,07.DENG Jin,WANG Lan-min.Unsaturated Loess Modification Processing Method:China,103184052A[P].2013,07.(in Chinese)
[6]邓津,王兰民,吴志坚,等.黄土抗震陷变形的酸改性方法及其微观结构分析[J].岩土力学,2012,33(12):3624-3631.DENG Jin,WANG Lan-min,WU Zhi-jian,et al.Aci-modified Method for Loess Seismic Subsidence and its Microstructure Analysis[J].Rock and Soil Mechanics,2012,33(12):3624-3631.(in Chinese)
[7]邓津,王兰民,张振中,等.我国黄土的微观结构类型与震陷区域划分[J].地震工程学报,2013,35(3):664-670.DENG Jin,WANG Lan-min,ZHANG Zhen-zhong.et al.The China Loess Microstructure Type and its Seismic Subsidence Zones Divided[J].China Earthquake Engineering Journal,2013,35(3):664-670.(in Chinese)
[2]徐实,杨有海,耿煊,等.石灰改性黄土的强度特性试验研究[J].兰州交通大学学报,2007,25(6):97-100.XU Shi,YANG You-hai,GENG Xuan,et al.Lime Modified Loess Experimental Study of the Strength Characteristics[J].Journal of Lanzhou Jiaotong University,2007,25(6):97-100.(in Chinese)
[3]曾正中,马力鹤,南忠仁.粉煤灰对垃圾填埋场黄土垫层的改性试验[J].环境工程,2009(4):105-108.ZENG Zheng-zhong,MA Li-he,NAN Zhong-ren.Loess Cushion of Modified Fly Ash on the Landfill Test[J].Journal of Environmental Engineering,2009(4):105-108.(in Chinese)
[4]王峻,王谦,王平,等.粉煤灰掺入量对改性黄土动本构关系的影响[J].岩土工程学报,2013,35(增1):156-160.WANG Jun,WANG Qian,WANG Ping,et al.Effect of Adding Amount of Flyash on Dynamic Constitutive Relationship of Modified Loess[J].Chinese Journal of Geotechnical Engineering,2013,35(S1):156-160.(in Chinese)
[5]邓津,王兰民.非饱和黄土改性处理方法:中国,103184052A[P].2013,07.DENG Jin,WANG Lan-min.Unsaturated Loess Modification Processing Method:China,103184052A[P].2013,07.(in Chinese)
[6]邓津,王兰民,吴志坚,等.黄土抗震陷变形的酸改性方法及其微观结构分析[J].岩土力学,2012,33(12):3624-3631.DENG Jin,WANG Lan-min,WU Zhi-jian,et al.Aci-modified Method for Loess Seismic Subsidence and its Microstructure Analysis[J].Rock and Soil Mechanics,2012,33(12):3624-3631.(in Chinese)
[7]邓津,王兰民,张振中,等.我国黄土的微观结构类型与震陷区域划分[J].地震工程学报,2013,35(3):664-670.DENG Jin,WANG Lan-min,ZHANG Zhen-zhong.et al.The China Loess Microstructure Type and its Seismic Subsidence Zones Divided[J].China Earthquake Engineering Journal,2013,35(3):664-670.(in Chinese)
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