原状铁尾矿砂工程性质研究
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摘要
细粒含量是影响尾矿砂的工程性质的重要因素,目前的研究成果均主要集中于特定粒径范围的细砂含量对砂土强度特征的影响,对原状尾矿砂的工程性质研究较少。为了研究原状尾矿砂的空间级配特征、孔隙比变化特征、渗透特性和力学性质,通过现场钻孔取样、筛分试验、常规物性试验、渗透试验、快剪试验和不排水三轴试验,确定了0.075 mm以下细粒含量对上述性质的影响。研究表明:0.075 mm以下细粒含量随钻孔深度与距子坝距离增加而升高,且和分维值之间具有较高的相关性;30%左右的0.075 mm以下细粒含量是原状尾矿砂工程性质的分界点。当0.075 mm以下细粒含量小于30%时,随着细粒含量的增加,孔隙比减小,黏聚力增大,内摩擦角减小,渗透系数快速减小;当0.075 mm以下细粒含量大于30%时,随着细粒含量的增加,孔隙比增大,黏聚力减小,渗透系数缓慢减小。同时,随着细粒含量的增加,水平渗透系数与垂直渗透系数差值逐渐减小。0.075 mm以下细粒含量的增加,是引起尾矿砂工程性质发生变化的主要原因,其临界值在0.075 mm以下细粒含量30%左右。在尾矿坝建造过程中,控制0.075 mm以下细粒含量在30%左右,有利于尾矿坝稳定。
Fine particle content is an important factor affecting the engineering properties of tailings. The current research results mainly focus on the influence of strength characteristics of fine content in specific particle size range. But the engineering properties of undisturbed tailings have not been studied. In order to study the spatial gradation characteristics,pore ratio variation characteristics,permeability characteristics and mechanical properties of undisturbed tailings,on-site drilling sampling,screening test,conventional physical property test,penetration test,fast shear test and undrained triaxial test are operated. The effect of the fine particle content below 0.075 mm on the above properties has been found. The research shows that the content of fine particles below 0.075 mm increases with the distance to the dam,and has a high correlation with the fractal dimension. About 30% of the fines content below 0.075 mm is the demarcation point of the engineering properties of the original tailings. When the content of particles below 0.075 mm is less than 30%,as the content of fine particles increases,the void ratio decreases,the cohesive force increases,the internal friction angle decreases,and the permeability coefficient decreases rapidly;when the content of particles below 0.075 mm is greater than 30%,as the grain content increases,the void ratio increases,the cohesive force decreases,and the permeability coefficient decreases slowly. At the same time,with the increase of fine particle content,the difference between the horizontal and vertical permeability coefficients decrease.The threshold of the fine particle content below 0.075 mm is approximately 30% according to the difference in contact state.During the construction of the tailings dam,control the fine content below 0.075 mm to about 30%,which is conducive to the stability of the tailings dam.
Fine particle content is an important factor affecting the engineering properties of tailings. The current research results mainly focus on the influence of strength characteristics of fine content in specific particle size range. But the engineering properties of undisturbed tailings have not been studied. In order to study the spatial gradation characteristics,pore ratio variation characteristics,permeability characteristics and mechanical properties of undisturbed tailings,on-site drilling sampling,screening test,conventional physical property test,penetration test,fast shear test and undrained triaxial test are operated. The effect of the fine particle content below 0.075 mm on the above properties has been found. The research shows that the content of fine particles below 0.075 mm increases with the distance to the dam,and has a high correlation with the fractal dimension. About 30% of the fines content below 0.075 mm is the demarcation point of the engineering properties of the original tailings. When the content of particles below 0.075 mm is less than 30%,as the content of fine particles increases,the void ratio decreases,the cohesive force increases,the internal friction angle decreases,and the permeability coefficient decreases rapidly;when the content of particles below 0.075 mm is greater than 30%,as the grain content increases,the void ratio increases,the cohesive force decreases,and the permeability coefficient decreases slowly. At the same time,with the increase of fine particle content,the difference between the horizontal and vertical permeability coefficients decrease.The threshold of the fine particle content below 0.075 mm is approximately 30% according to the difference in contact state.During the construction of the tailings dam,control the fine content below 0.075 mm to about 30%,which is conducive to the stability of the tailings dam.
引文
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[15]Thevanayagam S,Shenthan T,Mohan S,et al.Undrained fragility of clean sands,silty sands,and sandy silts[J].Journal of the Geotechnical and Geoenvironmental Engineering,2002,128(10):849-859.
[16]Naeini S A,Baziar M H.Effect of fines content on steady-state strength of mixed and layered sampled of sand[J].Soil Dynamics and Earthquake Engineering,2004,24(3):181-187.
[17]Rahman M M,Lo S R,Gnanedran C T.On equivalent granular void ratio and steady state behaviour of loose sand with fines[J].Canadian Geotechnical Journal,2008,45(10):1439-1456.
[18]Thevanayagam S.Effect of fines and confining stress on undrained shear strength of silty sands[J].Journal of Geotechnical and Geoenvironmental Engineering,1998,124(6):479-491.
[2]朱建群,孔令伟,钟方杰.粉粒含量对砂土强度特性的影响[J].岩土力学,2007,29(11):1648-1652.Zhu Jianqun,Kong Lingwei,Zhong Fangjie.Effect of fines content on strength of silty sands[J].Rock and Soil Mechanics,2007,29(11):1648-1652.
[3]衡朝阳,何满潮,裘以惠.含黏粒砂土抗液化性能的试验研究[J].工程地质学报,2001,9(4):339-344.Heng Chaoyang,He Manchao,Qiu Yihui.Experimental study of liquefaction-resistant characteristics of clayey sand[J].Journal of Engineering Geology,2001,9(4):339-344.
[4]张超,杨春和.细粒含量对尾矿材料液化特性的影响[J].岩土力学,2006,27(7):1133-1137.Zhang Chao,Yang Chunhe.Effect of fines content on liquefaction properties of tailings material[J].Rock and Soil Mechanics,2006,27(7):1133-1137.
[5]Phan V T A,Hsiao D H,Nguyen P T L.Critical state line and state parameter of sand-fines mixtures[J].Procedia Engineering,2016,142:298-305.
[6]党发宁,刘海伟,王学武.基于有效孔隙比的粘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):1910-1917.Dang Faning,Liu Haiwei,Wang Xuewu.Empirical formulas of permeability of clay based on effective pore ratio[J].Chinese Journal of Rock Mechanics and Engineering,2015,34(9):1910-1917.
[7]Prakash S,Dakoulas P.The influence of fines type and content on cyclic strength in ground failures under seismic conditions[J].Sessions of ASCE National Convention,1994:56-61.
[8]E Takch A,Sadrekarimi A,E Naggar H.Cyclic resistance and liquefaction behavior of silt and sandy silt soils[J].Soil Dynamicsand Earthquake Engineering,2016,83:98-109.
[9]王亚琴.红土镍矿深度还原-磁选工艺研究[D].沈阳:东北大学,2011.Wang Yaqin.Deep Reduction-Magnetic Separation Research on Nickel Laterite Ore[D].Shenyang:Northeastern University,2011.
[10]刘志祥,李夕兵.尾砂分形级配与胶结强度的知识库研究[J].岩石力学与工程学报,2005,24(10):1789-1793.Liu Zhixiang,Li Xibing.Study of fractal gradation of tailings and knowledge bank of its cementing strength[J].Chinese Journal of Rock Mechanics and Engineering,2005,24(10):1789-1793.
[11]Xenaki V C,Athanasopoulos G A.Liquefaction resistence of sandslit mixture:an experimental investigation of the effect of fines[J].Soil Dynamics and Earthquake Engineering,2003,23:183-194.
[12]Thevanayagam S.Liquefaction potential and undrained fragility of silty soils[C]//Proceeding of the 12th World Conference Earthquake Engineering.New Zealand Society of Earthquake Engineering.Wellington[:s.n.],2000.
[13]Sitharam T G,Dash H K,Jakka R S.Postliquefaction undrained shear behavior of sand-silt mixtures at constant void ratio[J].International Journal of Geomechanics,2013,13(4):421-429.
[14]Thevanayagam S,Martin G R.Liquefaction in silty soils-screening and remediation issue[J].Soil Dynamics and Earthquake Engineering,2002,22(9/10/11/12):1035-1042.
[15]Thevanayagam S,Shenthan T,Mohan S,et al.Undrained fragility of clean sands,silty sands,and sandy silts[J].Journal of the Geotechnical and Geoenvironmental Engineering,2002,128(10):849-859.
[16]Naeini S A,Baziar M H.Effect of fines content on steady-state strength of mixed and layered sampled of sand[J].Soil Dynamics and Earthquake Engineering,2004,24(3):181-187.
[17]Rahman M M,Lo S R,Gnanedran C T.On equivalent granular void ratio and steady state behaviour of loose sand with fines[J].Canadian Geotechnical Journal,2008,45(10):1439-1456.
[18]Thevanayagam S.Effect of fines and confining stress on undrained shear strength of silty sands[J].Journal of Geotechnical and Geoenvironmental Engineering,1998,124(6):479-491.