计算静压桩沉桩阻力的综合调节系数法

Adjusting-coefficient Method to Calculate Penetration Resistance of Jacked Piles

利用静力触探的资料,结合图形显示技术计算沉桩阻力,并通过调节桩端阻力和桩侧摩阻力的两个修正系数α、β来使计算曲线和实测曲线吻合。计算中可以变化选取桩尖以上、桩尖以下不同深度范围内土的静力触探锥尖阻力qp,以考察对沉桩阻力的影响;并可将压桩力分离为桩侧摩阻力和桩端阻力,分别加以研究和调整。文中称这种计算压桩力的新方法为综合调节系数法。计算实例表明,在压桩过程中,入土浅时主要是克服桩端阻力;随着桩入土深度的增加,桩侧摩阻力累计值也逐渐增大,占沉桩阻力的比例提高。当桩端进入较硬在持力层后,桩端阻力有明显的提高。用静力触探侧摩阻力fs计算桩的侧摩阻力时,土层性质不同调整折减的幅度不一样,在粘性土中调整幅度较大,而在砂性土中调整的幅度较小。

This paper takes advantage of the data from static penetration testing （SPT） combined with graphic display technology to calculate penetration resistance of jacked piles. Two adjusting-coefficients and , one for pile toe resistance and the other for pile skin friction resistance. are employed to make the calculated press-in force curves fit with the measured one. Different soil thicknesses were permitted in pile toe calculating in order to analyze the influence upon total press-in resistance. The pile toe resistance and skin friction resistance are studied and adjusted respectively. This new kind of calculating method is called the adjusting-coefficient method. Two engineering computation examples verified the feasibility of this method. The calculated result shows that the pile toe resistance is dominant when the pile is penetrating in shallow ground, but the skin friction resistance gradually increases as the penetration deepens and may exceed the toe resistance value. Toe resistance greatly develops when the pile tip enters the hard soil layer.