考虑静压桩挤土应力影响的室内试验研究

Laboratory test study on compacting stress effect of jacked pile

通过GDS应力路径三轴仪进行饱和淤泥质粉质黏土的应变保持和剪切试验,模拟静压桩沉桩过程中及沉桩后桩周土体孔隙水压力、有效应力的变化以及剪切模量的变化。研究结果表明:桩周土体的超静孔隙水压力u与应变ε、初始应力σ0有关;最大超静孔隙水压力umax与应变ε之间近似双曲线分布关系;最大超静孔隙水压力umax与初始应力σ0之间、有效应力增量?σa′与初始应力σ0之间近似直线变化关系;剪切模量G_(50)与距桩轴相对距离r/r0之间近似双曲线分布,与深度有关;归一化后的剪切模量G_(50)/G_(50∞)与深度的关系不明显,仅与距桩轴相对距离r/r0有关,7.5倍桩径之外的剪切模量G_(50)不再受到桩贯入的影响。

Based on the strain-holding test and shearing test of saturated muddy silty clay by using GDS stress path triaxial apparatus, the changes of effective stress, excess pore water pressure and shear modulus of soil around the pile were simulated during and after pile jacking respectively. The results show that excess pore water pressure of soil around the pile is related to strain value and initial stress. Relationship between maximum excess pore water pressure and strain indicates approximate hyperbola distribution relationship. Furthermore, relationships between maximum excess pore water pressure and initial stress as well as effective stress increment and initial stress display approximately linear relationship. The approximate hyperbola distribution is revealed between shear modulus and normalized radial distance. Shear modulus also has some relationship with depth. The normalized shear modulus is related to normalized radial distance, while it has no obvious relationship with depth. The shear modulus is not affected by pile jacking beyond 7.5 times pile diameter.