桩周土开挖条件下钢管桩屈曲稳定性试验研究

Experimental study on steel pipe pile bucking stability under excavation conditions

既有建筑物增设地下空间时,需要运用桩基础支撑上部建筑物,才可开挖建筑物下面的土方。随着桩周土减少,桩的屈曲稳定性会相应减少。文章在模型箱内利用杠杆加载的方式对不同开挖深度条件下的钢管桩的屈曲承载力进行了研究和测试,分析了其相应的稳定系数。结果表明:当桩顶加载达到极限荷载时,桩身会出现突然的屈曲破坏;开挖比较小时,屈曲位置出现在桩土交界面附近,随着开挖比的增加,屈曲位置明显上移;随着桩周土开挖深度增加,桩的稳定系数随之减小,当钢管桩下端处于嵌固状态时,其稳定系数比处于非嵌固状态时明显要大;钢管桩中部增设了水平拉接杆件后,其稳定性明显提高;桩周土的开挖比>0.5时,回转半径较大的钢管桩稳定性系数较大;当其值<0.5时,回转半径较大的钢管桩稳定性系数较小。

The underpinning pile can be used to support the existing building for construction of basement. The soil excavation around the pile can decrease the bearing capacity of piles. The piles bucking stability in different excavation depth was tested in model box by pry bar loading devise. Then, the stability coefficient was calculated. The test results indicate：when the loads on the top of the pile reaching ultimate load, the body of the pile appears the buckling deformation. At the beginning of soil excavation, the buckling location of pile is near the interface of the pile and soil. The deeper soil excavation, the higher location of pile buckling; The stability coefficient decreases with the soil excavation around the pile;the stability coefficient with end build-in is higher than with end non embedded ; the stability coefficient of piles increases obviously after the horizontal components installed on the piles; the stability coefficient of piles with high radius of gyration is bigger than with low radius of gyration when the ratio of excavation depth to length of pile over 0.5 ; on the contrary, the stability coefficient of piles with high radius of gyration is smaller than with low radius of gyration when the ratio of excavation depth to length of pile under 0.5.