水泥土搅拌桩处理风积沙地层复合地基静载荷试验数值分析

Numerical Analysis of Static Load Test on Composite Foundation of Aeolian Sand Layer Treated with Cement-soil Mixing Pile

以榆林地区水泥土搅拌桩处理风积沙地层复合地基工程为背景,基于ABAQUS有限元分析软件,对水泥土搅拌桩处理风积沙地层的复合地基静载荷试验进行数值模拟,并分析风积沙复合地基桩土荷载传递机制及变形特性。结果表明:合理设置褥垫层厚度能有效减小桩顶应力集中,降低桩土应力比。提高褥垫层模量可减小复合地基的沉降,改善其承载性能。设置褥垫层的桩侧摩阻力在桩顶附近出现负摩阻力,随着深度向下快速增加至零,并转为正摩阻力。桩身的附加轴应力在桩顶附近先增加到峰值,然后逐渐衰减。水泥土搅拌桩处理风积沙地基时存在临界桩长。在相同荷载水平下,随着桩长的增加,桩土应力比先增大后趋于稳定,桩侧摩阻力分布随着桩长的增加趋于稳定。按规范设计的风积沙复合地基承载力特征值偏于安全,有较大的富余度。

Using the composite foundation project involving cement-soil mixing pile treatment for the aeolian sand layer in Yulin,Shaanxi Province as the context,numerical simulations of static load tests on this composite foundation were performed using ABAQUS finite element analysis software.The study aimed to explore the load transfer mechanism and deformation characteristics of the pile-soil system in aeolian sand composite foundations.The results show that appro-priately adjusting the thickness of the cushion layer can effectively reduce stress concentration at the pile top and de-crease the pile-soil stress ratio.Increasing the modulus of the cushion layer can reduce the settlement of the composite foundation and enhance its bearing capacity.The side friction resistance of the pile with a cushion layer is negative near the pile top,rapidly decaying to zero with depth,and then turning into positive friction resistance.Corresponding-ly,the additional axial stress of the pile body first increases to its peak near the pile top,and then gradually decreases along the depth.There is a critical pile length when using cement-soil mixing piles to treat aeolian sand foundations.Under the same load level,as the pile length increases,the pile-soil stress ratio initially increases and then stabilizes,while the distribution of lateral frictional resistance along the pile body also tends to stabilize with the increase in pile length.The characteristic values of the bearing capacity of the aeolian sand composite foundation,designed according to the specifications,show a safety bias with a significant margin.