现浇混凝土薄壁筒桩竖向承载特性分析

Study on axial bearing properties of cast-in-place concrete thin-wall tubular piles

现浇薄壁筒桩是在沉管灌注桩的基础上加以改进发展而成的一种新桩型.对筒桩的承载机理进行分析,提出了筒桩的破坏模式.假定内侧摩阻力成指数函数分布,得出单桩总的内侧摩阻力计算公式及单桩竖向极限承载力估算公式,并对一算例进行了分析.研究结果表明,筒桩承受的荷载由外侧摩阻力、桩身端阻力、内侧摩阻力和土芯顶部阻力共同承担;桩身端部土体先发生破坏,向外侧和内侧(土芯)挤出,桩身刺入土体中,桩端沉降急剧增大,达到破坏状态,而土芯端部土体未达到破坏状态.筒桩外侧摩阻力值较大,是一种摩擦型桩.

The cast-in-place thin-wall tubular pile is a new pile type with its development based on diving casing cast-in-place pile. The load-bearing mechanism of cast-in-place thin-wall tubular pile was analyzed and the destroy mode was advanced. Assuming the distribution mode of inner friction resistance to be exponential function,the formula for total inner friction resistance and estimation formula for ultimate vertical bearing capacity of single pile were proposed. One calculation was studied. It is founded that the load of tubular pile was shared by outer and inner friction resistance, resistance at the end of pile, and resistance of top soil core. Soil at the end of tubular pile was destroyed first and extruded toward inner and outer soil core. When pile penetrated into soil, its settlement increased dramatically and reached its destroy state while soil at the end of soil core hadn't. With great outer friction resistance,tubular pile was a kind of frictional pile.