喷灌挤压组合桩工作机理现场试验研究?

通过5棵喷灌挤压组合桩破坏性静载试验,获得该桩工作机理,明确荷载传递机制、桩身轴力、侧摩阻力分布规律。不同荷载作用下,轴力沿桩身逐渐减小,在翼板顶轴力小幅度增大;桩身侧摩阻力随着外载的增加而逐渐增大,上部土体侧阻力先于下部土体发挥作用;揭示喷射注浆效应范围为7～8 m。喷灌挤压综合效应承载力增长显著,主要表现在侧摩阻:存在翼板时,喷射注浆与翼板共同作用,其侧摩阻极限值在砂土层中提高3～4倍,在黏土层中提高2～2.5倍。无翼板存在,但存在喷射注浆效应时,其侧摩阻力极限值提高了2～2.5倍。与普通长螺旋灌注桩相比其极限承载力提高25%～100%。

Study on Work Mechanism and In-situ Test of Pressure-grouting and Squeeze Combined Pile

Through five destructive static load tests of pressure-grouting and squeeze combined pile, the working mechanism of the pile was obtained, and the load transfer mechanism and pile axial force and lateral friction resistance distribution were clarified. Under different loads, the axial force gradually decreases along the pile body, while increases slightly at the top of the wing; the lateral friction of the pile gradually increases with the increase of the external load, and the lateral resistance of the upper soil precedes the lower soil; the jet grouting effect range is 7~8 m. The comprehensive bearing capacity of pressure-grouting and squeezing has increased significantly, mainly for the side friction. When there is a wing plate, the combined effect of jet grouting and wing plate leads to an increase in side friction limit value by 3 to 4 times in the sand layer, while by 2 to 2.5 times in the clay layer. For cases without wing plates but with a jet grouting effect, the side friction limit is increased by 2 to 2.5 times. Compared with ordinary long spiral cast-in-place piles, the ultimate bearing capacity of pressure-grouting and squeeze combined pile is increased by 25% to 100%.