风积砂-黄土混合料与钢界面的环形剪切力学特性

Ring Shear Characteristics Between Aeolian Sand-Loess Mixtures and Steel Interface

黄土高原北侧与诸多沙漠接壤,形成了广泛分布的风积砂-黄土混合区。不同比例条件下的风积砂-黄土混合料会呈现不同的物理力学特征,且风积砂-黄土混合料地基现场施工和使用过程中常与其他材料产生界面接触力学行为,相关研究目前鲜有述及。鉴于此,本工作获得了不同掺砂率条件下的混合料最大干密度,配制相同压实度和不同掺砂率的风积砂-黄土混合料环状试样,开展不同竖向压力和剪切速率条件下的混合料与钢制界面的环形剪切试验,借助扫描电镜观测不同混合料的颗粒分布特征以及颗粒破碎特征,揭示风积砂-黄土混合料与钢制界面环形条件下的残余强度形成机制。结果表明,随着掺砂率的增大,风积砂-黄土混合料的物理力学特征由黄土向砂土过渡。竖向压力小于100 kPa条件下,混合料产生剪胀的概率增大。混合料与钢界面之间的残余强度与竖向压力呈线性关系,变化趋势符合摩尔-库仑定律。随着掺砂率的增大,风积砂颗粒破碎效应增大,混合料与钢界面之间的残余内摩擦角及残余黏聚力均会减小。剪切速率的增大会缩短混合料与钢界面之间的接触时间,两者之间的接触、咬合效应尚不足以发挥作用进而减小了界面残余强度。研究结果预测了风积砂中掺入黄土的比例,可以为风积砂地基处理提供有益参考,也可为风积砂-黄土混合料施工力学行为研究提供科学借鉴。

The northern side of the Loess Plateau is bordered by many deserts,forming a widely distributed mixed distribution area of aeolian sand and loess.The aeolian sand-loess mixture(ASLM)presents different physical and mechanical characteristics under different proportion conditions,and the interfacial contact mechanical behavior of the ASLM foundation of ten occurs with other materials during field construction,and the relevant research is rarely mentioned at present.This work obtained the maximum dry density of the ASLM under different sand content conditions,prepared circular specimens of the ASLM with the same compaction degree and different sand content,and conducted ring shear tests on the interface between the ASLM and steel under different vertical pressures and shear velocities.The particle distribution properties and particle fragmentation characteristics of different sand content were observed using scanning electron microscopy,and the formation mechanism of resi-dual strength of ASLM with steel in ring shear condition was revealed.The test results show that the physical and mechanical characteristics of ASLM transition from loess to sandy soil with the increase of sand content.When the vertical pressure is less than 100 kPa,the probability of dilatancy of the mixture increases.There is a linear relationship between the interface residual strength and vertical pressure between the ASLM and the steel,which is consistent with the Mohr-Coulomb law.As the sand content increases,the crushing effect of aeolian sand particles increases,and the interfacial residual internal friction angle and the interfacial residual cohesion between the ASLM and steel decrease.An increase in shear rate shorten the contact time between the mixture and the steel interface,making it difficult to exert the contact and bite effects between the two,thereby reducing the residual strength of the interface between ASLM and steel.The research results predict the proportion of loess added to aeolian sand,which can provide useful reference for the treatment of aeolian sand foundation and also provide scientific reference for revealing the construction mechanics of ASLM.