动静复合拉拔作用下锚杆结构的破坏机制研究

Damage Mechanism of Anchor Bolt Structure Under Dynamic and Static Pullout Loads

为研究锚杆结构在动静复合拉拔作用下的破坏机制,基于锚固剂的弹塑性损伤本构模型和锚固界面黏结滑移模型,引入参数“静力比”和变幅正弦式动荷载模型,建立了锚杆结构的数值计算模型。首先以锚杆加载端的荷载—位移曲线为研究对象,通过室内试验进行了模型验证。然后对不同界面强度的多组锚杆结构在复合拉拔作用下的破坏过程、破坏模式和破坏特征等展开了研究,同时对参数静力比的影响进行了分析。结果表明:(1)受锚固界面强度的影响,锚杆结构主要包括:单一破坏模式(锚固界面滑移脱黏)、三段复合破坏模式(锚固剂斜开裂—水平开裂—界面滑移脱黏)和两段复合破坏模式(锚固剂斜开裂—水平开裂)。(2)锚固界面强度较小时,锚杆沿锚固界面完全脱黏。随着界面强度的增大,锚固剂斜向开裂缝倾角越小,斜向开裂区范围越大,但尚未延伸至锚固界面。(3)静力比在70%以下时,锚杆结构的承载力随静力比的提高而逐渐增加,反之则逐渐降低。锚杆结构的极限位移和动载循环次数均随静力比的提高而逐渐降低。(4)复合拉拔作用下锚杆结构的峰值荷载低于其在静力时的值,且峰后承载力下降更为明显。工程应用中,建议增加锚固界面和锚固剂强度,适当降低静力比,减弱动力冲击荷载的作用。

Research on damage mechanism of anchor bolt structure under dynamic and static pull-out is very important to the design and construction,the numerical calculation model was established based on elastoplastic damage model of anchorage agent and bond-slip model of anchorage interface,and parameter“static ratio”and sinusoidal dynamic load model with variable amplitudes were also introduced.The numerical model was verified by laboratory test firstly taking deformation curve of anchor bolt as example,then the damage mechanisms of anchor bolt structures with different interface strengths under composite loads were studied,which includes the damage process,mode and characteristics,and the influence of static ratio was also analyzed simultaneously.Results show that three damage modes of anchor bolt structure are included under influence of anchorage interface strength,namely single damage mode(anchorage interface sliding),three phases damage mode(oblique&horizontal cracks of anchorage agent and interface sliding),two phases damage mode(oblique and horizontal cracks of anchorage agent).Anchor bolt slides with the anchorage interface when the interface strength is small,while the oblique crack of anchorage agent generates with the increase of interface strength,and the dip angle becomes smaller,the oblique crack zone becomes larger,while the oblique crack doesn’t extend to anchorage interface.Bearing capacity of anchor bolt structure increases with the increase of static ratio when it’s less than 70%,while it decreases gradually on the contrary.Ultimate displacement of anchor bolt structure and cycle time of dynamic load decrease with the increase of static ratio.Peak load of anchor bolt structure under composite loads is less than the static condition,and the decrease is apparent of post-peak bearing capacity.In engineering application,strength increases of anchorage interface and agent are suggested,and decrease of static ratio as well,especially the reduction of dynamic impact load.