试样边壁及内部缺陷对土体渗透系数测量的影响分析
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摘要
土体的渗透系数是评价土体渗透固结性能的重要指标。在心墙坝中,准确测定心墙料的渗透系数对评价心墙的固结变形和拱效应具有非常重要的意义。测量渗透系数的方法包括渗透试验和固结试验。由于试样边壁和内部缺陷的影响,这两种方法的测量结果均可能与实际土体的渗透系数存在一定偏差。本文通过对概念模型的理论分析和推导计算,研究了试样边壁和内部缺陷对渗透试验和固结试验测量渗透系数结果的影响。分析结果表明,试样边壁和内部缺陷均对渗透试验的结果有显著影响,而对固结试验的结果则影响较小。在选择渗透系数的测量方法时,应根据具体情况。在分析心墙坝的渗漏量时,宜通过渗透试验测定心墙料渗透系数,但需要对试样边壁进行处理,尽可能消除边壁效应的影响;在分析心墙的应力变形时,则宜通过固结试验测定心墙料的固结系数或渗透系数,以免高估了心墙的固结性能。
Permeability coefficient is an important index to evaluate the consolidation performance of soil.Accurate determination of the permeability coefficient of the core wall material is very important for evalua-tion for the deformation and the arch effect of earth core rockfill dam(ECRD). The methods of measuringpermeability coefficient include seepage test and consolidation test. Because of the influence of boundaryand internal defects of the sample,the measurement results of the two methods may have certain deviationfrom the actual permeability coefficient of soil. This paper studies the influence of boundary and internal de-fects of the specimen on the measurement of permeability coefficient by seepage test and consolidation test,based on theoretical analysis and numerical calculation of the conceptual model. The results show that bothboundary and internal defects of the sample have significant influence on the results of the seepage test,while the result of the consolidation test is less affected. The choice of permeability measurement methodsshould be based on specific circumstances. When the leakage of ECRD is evaluated,it is better to mea-sure the permeability coefficient of the core wall by seepage test,but the boundary of sample should betreated to eliminate the influence of boundary defects. When the deformation behavior of ECRD is evaluat-ed, it is better to determine the consolidation coefficient or permeability coefficient through consolidationtest,to avoid overestimation of permeability of the core wall.
Permeability coefficient is an important index to evaluate the consolidation performance of soil.Accurate determination of the permeability coefficient of the core wall material is very important for evalua-tion for the deformation and the arch effect of earth core rockfill dam(ECRD). The methods of measuringpermeability coefficient include seepage test and consolidation test. Because of the influence of boundaryand internal defects of the sample,the measurement results of the two methods may have certain deviationfrom the actual permeability coefficient of soil. This paper studies the influence of boundary and internal de-fects of the specimen on the measurement of permeability coefficient by seepage test and consolidation test,based on theoretical analysis and numerical calculation of the conceptual model. The results show that bothboundary and internal defects of the sample have significant influence on the results of the seepage test,while the result of the consolidation test is less affected. The choice of permeability measurement methodsshould be based on specific circumstances. When the leakage of ECRD is evaluated,it is better to mea-sure the permeability coefficient of the core wall by seepage test,but the boundary of sample should betreated to eliminate the influence of boundary defects. When the deformation behavior of ECRD is evaluat-ed, it is better to determine the consolidation coefficient or permeability coefficient through consolidationtest,to avoid overestimation of permeability of the core wall.
引文
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[15]CHANEY,DEMARS K,FOX P J.Analysis of hydraulic gradient effects for laboratory hydraulic conductivity testing[J].Geotechnical Testing Journal,1996,19(2):181-190.
[16]朱国胜,张家发,陈劲松,等.宽级配粗粒土渗透试验尺寸效应及边壁效应研究[J].岩土力学,2012,33(9):2569-2574.
[17]MüLLER R,LARSSON S.Hydraulic conductivity and coefficient of consolidation of two sulphide clays in sweden[J].Geotechnical&Geological Engineering,2012,30(1):173-186.
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[19]王鸣宇,王秀艳,孙琳.饱和黏性土渗透系数测定方法综述[J].南水北调与水利科技,2015,13(6):1162-1167.
[20]谢新宇,张继发,曾国熙.饱和土体一维主固结解析方法研究[J].浙江大学学报:工学版,2002,36(4):347-351.
[21]李西斌,谢康和,陈福全.考虑软土流变特性和应力历史的一维固结与渗透试验[J].水利学报,2013,44(1):18-25.
[2]喻和平,张聪,郭英,等.小浪底大坝心墙渗透压力预测模型研究[J].人民黄河,2015,37(1):130-132.
[3]陈继平,曹林曦,刘明华,等.砾石土心墙堆石坝施工期孔隙水压力分析[J].岩土力学,2008,29(S1):180-184.
[4]沈珠江.鲁布革心墙堆石坝变形的反馈分析[J].岩土工程学报,1994,16(3):1-13.
[5]陈立宏,陈祖煜,张进平,等.小浪底大坝心墙中高孔隙水压力的研究[J].水利学报,2005,36(2):219-224.
[6]南京水利科学研究院.SL237-1999土工试验规程[S].北京:中国水利水电出版社,1999.
[7]黄达,曾彬,王庆乐.粗粒土孔隙比及级配参数与渗透系数概率的相关性研究[J].水利学报,2015,46(8):900-907.
[8]邓永锋,刘松玉,章定文,等.几种孔隙比与渗透系数关系的对比[J].地震工程学报,2011,33(S1):64-66.
[9]党发宁,刘海伟,王学武,等.基于有效孔隙比的黏性土渗透系数经验公式研究[J].岩石力学与工程学报,2015,34(9):1909-1917.
[10]KENNEY T C,CHAN H T.Field investigation of permeability ratio of new liskeard varved soil[J].Canadian Geotechnical Journal,1973,10(3):473-488.
[11]CARPENTER G W,STEPHENSON R W.Permeability testing in the triaxial cell[J].Geotechnical Tesing journal,1986,9(1):3-9.
[12]朱建华.土坝心墙原状土的三轴渗透试验[J].岩土工程学报,1989,11(4):57-63.
[13]雷红军,卞锋,于玉贞,等.黏土大剪切变形中的渗透特性试验研究[J].岩土力学,2010,31(4):1130-1133.
[14]蒋中明,王为,冯树荣,等.砂砾石土渗透变形特性的应力状态相关性试验研究[J].水利学报,2013,44(12):1498-1505.
[15]CHANEY,DEMARS K,FOX P J.Analysis of hydraulic gradient effects for laboratory hydraulic conductivity testing[J].Geotechnical Testing Journal,1996,19(2):181-190.
[16]朱国胜,张家发,陈劲松,等.宽级配粗粒土渗透试验尺寸效应及边壁效应研究[J].岩土力学,2012,33(9):2569-2574.
[17]MüLLER R,LARSSON S.Hydraulic conductivity and coefficient of consolidation of two sulphide clays in sweden[J].Geotechnical&Geological Engineering,2012,30(1):173-186.
[18]RAISINGHANI D V,VISWANADHAM B V S.Evaluation of permeability characteristics of a geosynthetic-reinforced soil through laboratory tests[J].Geotextiles and Geomembranes,2010,28(6):579-588.
[19]王鸣宇,王秀艳,孙琳.饱和黏性土渗透系数测定方法综述[J].南水北调与水利科技,2015,13(6):1162-1167.
[20]谢新宇,张继发,曾国熙.饱和土体一维主固结解析方法研究[J].浙江大学学报:工学版,2002,36(4):347-351.
[21]李西斌,谢康和,陈福全.考虑软土流变特性和应力历史的一维固结与渗透试验[J].水利学报,2013,44(1):18-25.