含水率和聚丙烯酰胺分子量对重构铁尾矿砂抗剪强度的影响

Effects of Water Content and Polyacrylamide Molecular Weight on Shear Strength of Reconstructed Iron Tailing Sand

[目的]研究含水率和聚丙烯酰胺(PAM)分子量对重构铁尾矿砂抗剪强度的影响,为铁尾矿砂的边坡稳定和矿区生态修复提供科学依据。[方法]通过室内重塑铁尾矿砂开展抗剪强度试验,根据掺土率设置5种土壤(T)和尾矿砂(S)的重构模式,包括S(0),S_(3)T_(1)(25%T),S_(1)T_(1)(50%T),S_(1)T_(3)(75%T)和T(100%);每种重构模式设置两个含水率水平(15%,20%),两个聚丙烯酰胺分子量水平(3.00×10^(6),6.00×10^(6) Da)和3个紧实状态(疏松、偏紧、致密)。[结果]①在同一紧实状态下,随含水率的升高,5种重构模式的内摩擦角、黏聚力和抗剪强度均呈现出下降的趋势;②在同一含水率水平下,随着紧实度的增加,5种重构模式的内摩擦角、黏聚力、抗剪强度整体呈上升的趋势;③PAM能有效提高重构铁尾矿砂的抗剪强度,且随着分子量增加,抗剪强度增幅减小;⑤5种重构模式中添加3.00×10^(6) Da分子量的PAM,S_(3)T_(1)模式的抗剪强度提高较大,水分入渗能力也较强。[结论]含水率15%,PAM分子量为3.00×10^(6) Da时,S_(3)T_(1)的重构模式有利于矿区生态环境的修复和铁尾矿稳定性的提高。

[Objective]The effects of water content and molecular weight of polyacrylamide(PAM)on shear strength of reconstructed iron tailing sand were analyzed in order to better understand slope stability and ecological restoration of mining areas.[Methods]An indoor shear strength experiment was conducted by reconstructing iron tailing sand.Five reconstruction soil mixing rate treatments of soil(S)and tailings(T)were established:S(0%T),S_(3)T_(1)(25%T),S_(1)T_(1)(50%T),S_(1)T_(3)(75%T)and T(100%T).Treatments also included two water contents(15%,20%),two molecular weights of PAM(3.00×10^(6),6.00×10^(6) Da),and three compaction states(loose,tight,and dense)for each reconstruction pattern.[Results]①Under the same compaction state,the internal friction angle,cohesion,and shear strength for the five reconstruction patterns all decreased with increasing water content.②Under the same water content,the internal friction angle,cohesion,and shear strength of the five reconstruction patterns increased with increasing compaction.③Addition of PAM effectively improved the shear strength of reconstructed iron tailing sand,and shear strength decreased with increasing molecular weight of PAM.④When PAM with a molecular weight of 3.00×10^(6) Da was added into the five reconstruction patterns,the shear strength and water infiltration capacity of S_(3)T_(1) were greater than for the other reconstruction patterns.[Conclusion]The reconstruction pattern of S_(3)T_(1) with a water content of 15%and PAM molecular weight of 3.00×10^(6) Da were conducive to the restoration of the ecological environment in mining areas and to the improvement of the stability of iron tailing sand.