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页数:16页
时间:2019-01-09
《原状黄土冻融过程抗剪强度劣化机理试验分析》由会员上传分享,免费在线阅读,更多相关内容在学术论文-天天文库。
1、原状黄土冻融过程抗剪强度劣化机理试验分析 摘要:通过对西安Q3原状黄土在封闭系统冻融作用下的电镜扫描和直剪试验,研究了冻融作用对原状黄土微观结构和强度的影响。试验表明:冻融过程中原状黄土微观结构发生显著变化,大颗粒集粒数量明显减少,小粒径土颗粒所占比重增加,孔隙面积比增加。进一步基于损伤力学理论,得到微观结构冻融损伤度随冻融次数增加呈指数增加趋势,反映出冻融作用一定程度上破坏黄土体的结构强度,但多次冻融后黄土体结构强度趋于稳定的残余强度。冻融过程土样表面结构发生破坏,且含水率越高,土体表面特征破坏越严重。粘聚力随冻融次数增加呈指数衰减趋势,且含水率越高,粘聚力衰减幅值和速率越小;粘
2、聚力随含水率增加表现出线性衰减特征,且冻融后粘聚力与含水率的变化规律近似重合;内摩擦角无明显规律性变化。粘聚强度冻融损伤系数随冻融次数增加呈指数增加趋势,随含水率升高有增大趋势。基于试验数据规律性,进一步提出了原状黄土粘聚强度劣化模型,该模型经试验验证可较好描述原状黄土粘聚强度劣化规律。 关键词:原状黄土;冻融作用;电镜扫描;微观结构;抗剪强度 中图分类号:TU444 文献标志码:A文章编号:1674-4764(2016)05-0090-09 Abstract:SEManddirectsheartestswereconductedtostudytheinfluenceoffr
3、eeze-thawactiononthemicrostructureandstrengthofxi’anQ3undisturbedloessundertheclosedsystem.The16experimentalresultsshowedthatthemicrostructureofloesschangessignificantlyduringthefreeze-thawprocess,withthenumberoflargeparticlesaggregatedecreasing,theproportionofsmallparticlesizeincreasing,andthe
4、ratioofporeincreasing.Basedonthedamagemechanicstheory,thefreezing-thawingdamagedegreeversusfreezing-thawingtimeswasestablished.Analysisindicatedthatthefreezing-thawingdamagedegreeexponentiallyincreasedwiththeincreaseoffreezing-thawingtimes,representingthatthestructuralstrengthofloesscanbedestro
5、yedbyfreezing-thawing.However,thestructuralstrengtheventuallyreachedaresidualstrengthvalueafterrepeatedfreezingandthawing.Freezing-thawingmadethesurfacestructureofsoildestroyed,andhadabiggerinfluencewiththeincreaceofwatercontent.Thecohesionexponentiallydecreasedwithfreezingandthawingtimesincrea
6、sing,andhadasmallerattenuationamplitudeandratewiththeincreaseofwatercontent.Withtheincreaseofwatercontent,thecohesionlinearlydecreased,andhadanapproximatelysamevariationafterfreezingandthawing.Theinternalfrictionanglehadnoobviousvariationduringthewholefreezing-thawingprocess.Thefreezing-thawing
7、damagecoefficientofcohesionexponentiallyincreasedwiththeincreaseoffreezing-thawingtimes,andalsoincreasedwithwater16contentincreasing.Acohesionstrengthdeteriorationmodelwasdevelopedbasedonthelaboratorytestresults,andthemodelcanbeus
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