桩底沉渣对钻孔灌注桩力学性质影响研究

钻孔灌注桩因其自身众多优点而在工程中被广泛应用，而沉渣的存在对桩的承载特性有较大影响。根据现有工程资料，利用有限元软件详细分析了桩底沉渣厚度、弹性模量、泊松比、内聚力及内摩擦角各几何、物理力学参数对桩承载特性的影响。研究结果表明:沉渣厚度对单桩极限承载力有较大影响，沉渣的存在使得单桩极限承载力快速降低。沉渣厚度对极限承载力的影响存在临界值，其值在35~45 cm；沉渣各个模量下，桩顶P—S曲线均呈现出突变型变化，极限承载力随着沉渣弹性模量影响的增大而增大；各沉渣泊松比和内聚力下桩顶P—S曲线变化趋势类似，可认为沉渣泊松比和内聚力对单桩承载特性影响较小；单桩极限承载力随着沉渣内摩擦角的增大而增大，根据tan Φ—极限承载力散点图拟合出了沉渣内摩擦角对单桩极限承载力影响评价的定量公式。

Study on influence of pile bottom sediment on mechanical properties of cast-in-place pile

Because of its many advantages，bored piles are widely used in engineering，while the presence of sediment has a great impact on the bearing characteristics of piles.In this paper，based on the existing engineering data，the influence of geometrical and physical mechanical parameters of the pile bottom sediment thickness，elastic modulus，Poisson′s ratio，cohesion and internal friction angle on load-bearing characteristics of the pile was analyzed in detail by using finite element software.The results showed that:the sediment thickness has a great influence on the ultimate bearing capacity of single pile，the presence of sediment makes the ultimate bearing capacity of single pile rapidly reduced.There is a critical value of sediment thickness which affects the ultimate bearing capacity of single pile，its value between 35~45 cm.The P-S curve showed a sudden change in the top with different sediment module，and the ultimate bearing capacity increases with the increase of sediment elasticity modulus.The Poisson′s ratio and the cohesion force of each sediment have similar trend of change of P-S curve at the top of the pile，and it can be considered that the sediment Poisson′s ratio and cohesion have little effect on the bearing capacity of single pile.The ultimate bearing capacity of single pile increases with the increase of the internal friction angle of sediment，based on the scatter diagram of tanΦ~ ultimate capacity，the quantitative formula is fitted of the influence of the internal friction angle of the sediment on the ultimate bearing capacity of single pile.