基于Mohr-Coulomb的强盐沼泽区桩基承载特性探讨

Bearing Characteristics of Pile Foundation Based on Mohr-Coulomb Criterion in Strongly Alkaline Marsh Area

为了探究强盐沼泽区桥梁桩基的极限承载特性,采用桩基混凝土试件现场试验以及室内实验测得了桩基混凝土水养强度以及腐蚀强度,采用能谱仪(EDS)分析以及元素分析测得了桩基混凝土内部氯离子含量,采用室内电镜试验测得了桩基混凝土内部氯离子对流深度。将腐蚀性盐离子环境中的桩基混凝土试件划分为剥蚀区、腐蚀区和未蚀区,运用公式计算的方法得到现场暴露1 a桩基混凝土的腐蚀厚度与腐蚀后强度的关系。通过桩基混凝土强度与黏聚力c、内摩擦角φ之间的转换,建立了基于Mohr-Coulomb的强盐沼泽区桥梁桩基弹塑性本构模型,对强盐沼泽区桩基极限承载特性进行分析。结果表明:随着蚀径比的增大,单桩横轴向极限承载力逐渐降低,但降幅逐渐变缓;桩长增加对单桩横轴向极限承载力提升较小;随着蚀径比的增大,单桩竖向极限承载力逐渐降低,但降幅逐渐变缓;桩长不变,相同腐蚀厚度变化范围内,大直径单桩竖向极限承载力降幅大于小直径单桩竖向极限承载力降幅。

A elastoplastic constitutive model based on Mohr-Coulomb criterion was constructed to explore the limit bearing characteristics of bridge pile foundation in strongly alkaline marsh area based on the transformation among strength,cohesion,and internal friction angle.First of all,the water curing strength and corrosion strength of pile foundation concrete were measured by field test and laboratory test.The internal chloride ion concentration of concrete was measured by EDS analysis and element analysis.The convection depth of chloride ions inside the concrete was determined by an indoor electron microscopy test.In subsequence,the concrete specimens in the corrosive alkaline environment are divided into the spalling zone,the corroded zone and the non-corroded zone.The relation between corrosion depth and post-corrosion strength of concrete exposed one year was calculated by formula.Results demonstrated that with the increase of ratio of corrosion thickness to diameter of uncorroded pile,the ultimate bearing capacity of the transverse axial direction of a single pile reduced gradually,but the reduction gradually attenuated.The increase of pile length helped little to the improvement of ultimate bearing capacity of single pile transversely.The vertical ultimate bearing capacity of single pile also decreased gradually,and such decline also slowed down.Within the same range of corrosion thickness,the reduction of vertical ultimate bearing capacity of large-diameter single pile was greater than that of small-diameter single pile.