隧道锚喷支护体系拉拔性能及破坏形态试验研究

Experimental Study on Pull-out Performance and Failure Mode of Bolt and Shotcrete Supporting System in Tunnel

利用自行设计的多功能锚杆受力测试系统,开展不同形式托盘与不同强度素混凝土喷层组合工况下的锚杆轴心拉拔试验,研究托盘和喷层耦合作用下的杆体应力应变规律及喷层裂纹扩散形态。试验结果表明:锚杆伸长量-拉拔力关系曲线大致可分为弹性阶段、屈服阶段、强化阶段3个阶段;喷层混凝土强度对线性弹性阶段的锚杆刚度有显著影响,锚杆刚度随喷层混凝土强度增大而增大;喷层素混凝土强度采用C20时,蝶形托盘和新型托盘条件下锚杆的屈服平台宽度达到最大,分别达到50,47 mm,表现出让压功能;采用平板托盘和蝶形托盘时复喷层裂纹沿钻孔中心呈网状辐射,采用新型托盘时复喷层上裂纹贯通于一个方向。

Based on self-designed multi-function mechanical test system for bolts,axial pull-out tests of the bolt werecarried out with consideration of different plates and shotcrete of different strength. The stress-strain state of bolts andshotcrete cracking were studied under the coupling action of plates and shotcrete. Experimental results show that therelationship between elongation and pull-out force may be divided into three phases including elastic,yielding andstrengthening phase. The shotcrete strength has a significant impact on the bolt stiffness during the linear elastic phaseand the latter increases with the shotcrete strength. When C20 plain concrete is used as the shotcrete,the yield platformwidth of bolt for butterfly plate and new-type plate are more significant,and the value for each plate reach 50 and 47 mmrespectively,which shows the yield function. When flat plate or butterfly plate is used,the cracking of the uppershotcrete is net radiation around the drilling center. When new-type plate is used,the cracks of the upper shotcrete gothrough one direction.