土钉支护结构破坏模式和加固机制分析

对不同土质中土性参数和支护参数共同影响下基坑土钉支护结构的内力和位移进行了系统的数值试验研究。结果表明，从砂土到粉土，再到软黏土介质变化时，基坑位移大小剧增，位移形态也发展成下部凸出的流鼓状，而且中下部土钉不能满足承载力要求。土性参数中，内摩擦角和凝聚力是导致位移形态发生改变的主要因素，侧压力系数主要引起位移大小的变化。支护参数中，土钉密度突出控制钉间土体位移；土钉长度在砂土中控制上部位移显著，软黏土中抑制下部位移更明显；土钉刚度的影响体现为钉土刚度比的影响，主要由插筋刚度控制，而随土类变化并不明显；并得出了各支护参数的临界值。

Failure mode and reinforcement mechanism of soil-nailing structure

A series of numerical tests for soil-nailing structure in the sandy, silty and soft soil media are performed. Test results show that, in soft soil medium, the pit displacement is much larger than sandy medium, and the failure mode will change from overturning mode of sandy soil to flowing mode of soft clay; and the structure can not meet the demand of bearing capacity. Among soil parameters, c & ? values are the main factors causing above-mentioned change of failure mode; otherwise K0 value mainly change the magnitude of displacement. Among supporting parameters, nail-density evidently controls the displacement of soil between two rows nails. Nail-length remarkably controls the displacement of upside soil in sandy medium and of underside soil in soft soil medium respectively. The influence of nail-rigidity is embodied as that of rigidity ratio of nail to soil, which is not basically controlled by soil type, but reinforcing bars. Also, the critical supporting parameters are achieved.