大直径PHC管桩锤击贯入特性现场试验研究

Field test study on hammer penetration characteristics of large-diameter PHC pipe piles

为研究大直径PHC管桩锤击贯入荷载传递机理,依托于某高速桥梁桩基工程,对外径0.8m、长度43m的开口PHC管桩进行锤击沉桩试验,分析沉桩过程中桩顶荷载、桩端阻力、桩侧摩阻力以及桩身轴力与桩基贯入深度变化规律。研究表明随着贯入深度的增加,相同深度下的桩身轴力逐渐增大;在同一贯入深度下,桩身轴力沿深度自上而下非线性递减。在同一土层内随着贯入深度的增大,贯入阻力逐渐增大,桩端阻力受土层变化的影响更为显著。桩侧摩阻力的变化受土体软硬程度与锤击次数的影响,连续打桩时锤击次数不断增大,桩侧摩阻力出现了显著的疲劳衰退现象,桩端土体强度明显降低。

In order to study the transmission mechanism of large-diameter PHC pipe pile hammering through load,the hammering sinking pile tests are carried out based on the open PHC pipe pile with an outer diameter of 0.8m and the length 43m in the high-speed bridge pile foundation project.The variation laws of pile top loads,the pile end resistance,the pile side friction resistance,the pile shaft axial force and the pile foundation penetration depth during pile foundation penetration are analyzed.The study shows that with the increase of penetration depth,the axial force of pile body at the same depth increases gradually.At the same penetration depth,the axial force of the pile body decreases nonlinearly from top to bottom along the depth.With the increase of penetration depth in the same soil layer,the penetration resistance gradually increases,and the pile end resistance is more significantly affected by the soil layer change.The change of pile side friction resistance is affected by the hardness of soil and the number of hammering strikes,and the number of hammer strikes increases continuously during continuous piling,the pile side friction resistance shows significant fatigue decline,and the soil strength at the pile end is significantly reduced.