隧道式锚碇在碎裂岩体中成洞及承载特性数值模拟

Numerical Simulation on Cave Forming and Bearing Characteristics of Tunnel Type Anchorage in Fractured Rock Mass

与重力式锚碇相比,隧道式锚碇更为经济、环保,在峡谷地区悬索桥建设中具有广阔的应用前景。我国西南地区某在建铁路大跨度悬索桥隧道式锚碇在IV—V级工程岩体中承担4.3×10^(5) kN的超大主缆荷载,通过三维数值模拟方法对该隧道式锚碇的成洞特性、主缆荷载及超载作用下的围岩响应特征进行研究。结果表明:按设计支护措施,碎裂岩体在锚洞开挖后处于轻微挤压变形状态。主缆荷载作用下,锚碇周边围岩主要表现为弹性变形,锚塞体的位移增量属毫米级,围岩变形受地层岩性影响显著,锚塞体周边围岩位移梯度较大,主缆荷载的扩散范围有限;超载作用下,锚塞体围岩塑性区由后锚面逐步沿着锚塞体周边围岩向中前部发展,其最终破坏模式为锚岩接触周边围岩的剪切破坏。隧道式锚碇在围级基本质量较差的碎裂岩体中同样具有很强的适应性。

Tunnel type anchorage has wide application range in the building of suspension bridge as it is more economical and environmentally friendly than gravity anchorage.The tunnel type anchorage of a large-span suspension bridge on a railway in southwest China bears a super-large main cable load of 430,000 kN in the IV-V grade engineering rock mass.In the present research,the cave forming characteristics and the surrounding rock response characteristics under the main cable load and overload of the tunnel type anchorage were analyzed by using 3D numerical simulation method.Results unveil that according to the current support design,the fractured rock mass is in a state of slight squeezing deformation after the excavation of anchorage hole.The surrounding rock of tunnel type anchorage mainly displays elastic deformation under main cable load,and the displacement increment of the anchor plug body is only a few millimeters.The deformation of surrounding rock is significantly affected by the lithology of the stratum,and the gradient of surrounding rock displacement around the anchor plug body is large.Under overload,the plastic zone of surrounding rock of the anchor plug body gradually develops from the back anchor surface to the middle and front part along the surrounding rock of the anchor plug body,and the final failure mode is the shear failure of surrounding rock from the back anchor surface to the front anchor surface of anchor plug body.Tunnel type anchorage structure also has strong adaptability to rock mass environment with inferior basic quality.