覆盖层压力效应影响下的土钉抗拔性能评价

EVALUATION OF PULLOUT RESISTANCE OF SOIL NAILING CONSIDERING PRESSURE EFFECT OF OVERBURDEN

以天津市某冲积层区域为研究对象,考虑覆盖层压力效应对土钉抗拔和粘结性能的影响,进行了抗拔性能测试。在冲积层区域中选取粗粒土和粘性土,进行了42次原位拉拔试验。通过单因素方差分析,评价了土压比例和覆岩压力对抗拔阻力的影响。将所得结果与常规规范进行了比较,得出标准贯入试验地基抗拔力是比较保守的土钉抗拔力评价方法。结果表明,粗粒土中土钉的粘结抗力随覆盖层压力的增大而增大,而在粘性土中覆盖层压力对土钉的粘结抗力影响不显著。覆岩压力效应是通过颗粒间应力传递来调动的。此外,土钉粘接强度与施工质量有关。随着施工质量的降低,粘结强度也随之降低。靠近开挖地表的土钉对施工质量影响较大。

The alluvium in Tianjin was taken as the research object,and the effect of overburden pressure on the pullout and bond properties of soil nailing was considered.In order to study its pull-out resistance,42 in-situ pull-out tests of coarse-grained soil and clayey soil were carried out in Tianjin alluvial zone.At the same time,the influence of soil pressure ratio and overburden pressure on pullout resistance was evaluated by one-way analysis of variance.The results obtained in this paper were compared with the conventional standard,and it was concluded that the pullout resistance of standard penetration test foundation was a conservative evaluation method of soil nail pullout resistance.The results show that the bond resistance of soil nailing in coarse-grained soil increases with the increase of overburden pressure,but the effect of overburden pressure on the bond resistance of soil nailing in cohesive soil is not significant.The pressure effect of overburden rock is adjusted by stress transfer between particles.In addition,the bond strength of soil nailing is related to the construction quality.With the decrease of construction quality,the bond strength also decreases.The soil nailing near the excavation surface has great influence on the construction quality.