PDF(9178 KB)
PDF(9178 KB)
PDF(9178 KB)
砂土-钢板界面剪切试验与PFC细观模拟分析
Shear Test and PFC Meso-simulation Analysis of Sand-Steel Interface
针对砂土-钢板接触界面,通过大型界面剪切试验和PFC细观模拟,探究法向应力和界面粗糙度对砂土-钢板接触界面剪切力学特性的影响及内在机理。结果表明:界面粗糙度增大,界面摩擦角随之增大,界面剪切强度、残余强度提高,砂土剪缩、剪胀性显著;法向应力增大,界面剪切强度、残余强度提高,砂土剪缩性提升,剪胀性降低;界面剪切过程中砂土颗粒向剪切方向移动聚集,强接触力链合并,数量减少,传力性能提升;界面粗糙度通过改变钢板槽内砂土颗粒的数量使其与钢板的接触面积发生变化,从而对界面剪切力学特性产生影响;法向应力影响砂土与钢板接触的密实度和作用力,使得其界面剪切力学性状产生变化。
This study investigates the influence of normal stress and interfacial roughness on the shear mechanical properties of sand-steel plate contact interface and explores the underlying mechanisms through large-scale interface shear tests and PFC mesoscopic simulations. The findings indicate that increased interfacial roughness leads to a higher interfacial friction angle, enhanced interfacial shear strength and residual strength, and more pronounced shear shrinkage and dilatancy of the sand. As normal stress increases, interfacial shear strength and residual strength improve, shear shrinkage of the sand increases, and dilatancy decreases. During the shear process, sand particles move and aggregate in the shear direction, resulting in the merging of strong contact force chains, with a decrease in their numbers but improved force transmission performance. The interfacial roughness affects the contact area between sand particles and the steel plate by altering the number of sand particles in the steel plate grooves, thereby influencing the interface’s shear mechanical properties. Normal stress affects the compactness and contact force between sand and steel plate, leading to changes in the interface’s shear mechanical properties.
砂土-钢板接触界面 / 界面剪切试验 / PFC / 细观模拟 / 界面粗糙度 / 法向应力
sand-steel plate contact interface / interface shear test / PFC / mesoscopic simulation / interface roughness / normal stress
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桩基表面粗糙程度与砂粒径大小对砂土层桩侧摩阻力有显著影响。本文利用改装的室内直剪仪开展了不同粗糙界面的木板、钢板、混凝土板与北京标准砂间的直剪试验,研究界面剪切应力剪切位移关系、界面抗剪强度构成和界面摩擦角变化规律。结果表明:剪切应力位移关系可用对数幂函数模型拟合,硬化阶段采用对数模型,软化阶段采用幂函数模型,模型峰值剪切应力与试验峰值剪切应力的比值集中在0.92～1.02之间;峰值剪切应力与平均灌砂深度呈正相关关系,其从未刻纹路的界面Ⅰ到刻有纹路的界面Ⅱ增加值最大;刻有纹路的界面抗剪强度由未刻纹路区域、纹路棱角和纹路内的砂三部分提供,未刻纹路区域提供的抗剪强度最大,纹路棱角次之,纹路内的砂最小;木、钢和混凝土与标准砂的界面摩擦角分别集中在11°～23°、14°～23°和22°～27°范围内。研究成果可为砂土层桩侧摩阻力估计提供试验参考。
Surface roughness of pile foundation and particle size of sand play an important role in the shaft resistance of pile in sand strata.The interface shear test of standard sand with wood plate,steel plate and concrete plate were performed using an improved direct shear apparatus to investigate the interface shear stress-shear displacement curves,composition of the interface shear strength and interface friction angle.Test results indicated that the shear stress-displacement relationship can be fitted by the logarithmic-power function model.Logarithmic model is used in hardening stage and power function model is used in softening stage.The ratio between the peak shear stress and the peak shear stress of the model ranges from 0.92 to 1.02.The peak shear stress increases with average sand filling depth,and the most increase of the peak shear stress is found from interface I of without lines to interface II of with lines.The shear strength of interface with engraved lines is provided by the region of without lines,the grain edge and the sand in the grain.The area without lines is the largest,followed by the grain edge,and the sand in the grain is the smallest.The interfacial friction angle of wood,steel and concrete with standard sand ranges from 11 to 23°,14 to 23°,22 to 27°,respectively.The research results can provide experimental reference for shaft resistance estimation in sand strata.
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为研究土工织物加筋尾矿砂界面力学特性,在不同的尾矿砂含水率、试验拉拔速率和竖向压强下开展一系列土工布及土工格栅的拉拔试验。比较相同条件下的土工格栅与土工布拉拔试验结果可知:土工布对细粒尾矿砂的加筋效果优于土工格栅的加筋效果,竖向压强较大时两者的拉拔力峰值差值增大;随尾矿砂含水率增加,界面剪应力峰值明显减小,界面剪应力峰值在含水率1.2%时比含水率8.4%时增加50%以上,表观黏聚力先增加后减小,在最优含水率附近时达到最大,界面摩擦角先快速减小后缓慢减小;随试验拉拔速率增加,界面剪应力峰值缓慢增加,表观黏聚力先增加后减小,界面摩擦角先减小后增加;各工况下剪应力峰值均随竖向压强的增大而增大。研究结果可为土工织物加筋尾矿坝工程设计提供参考。
In order to study the mechanical properties of the reinforced interface between geotextile and fine tailings sand, we carried out pull-out tests on geogrid and geotextile under different test pull-out rates and different vertical pressures with varying moisture content of tailings sand. By comparing the pull-out test results of geogrid and geotextile under the same conditions, we conclude that geotextile has stronger reinforcement effect on fine tailings sand, and when vertical pressure is higher, the difference between the reinforcement effect on geotextile and geogrid is larger. With the rising of moisture content of tailings sand, the peak value of interfacial shear stress drops obviously: the interfacial shear stress at a moisture content of 1.2% is 1.5 times that when moisture content is 8.4%. Apparent cohesion increases at first but then decreases, with the peak value appearing near the optimal moisture content, whereas interfacial friction angle reduces rapidly at first and then declines slowly afterwards. With the augment of pull-out rate, the peak value of interfacial shear stress climbs slowly, and the apparent cohesion increases at first and then decreases, while the interfacial friction angle decreases at first and then increases. Under all working conditions, the peak value of shear stress increases linearly with the rising of vertical pressure.
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