拉压耦合大变形锚杆作用机理及其试验研究

Mechanism of CTC-yield bolts and its experimental research

在高应力作用下,围岩发生大变形破坏的现象非常普遍,硬岩常常产生严重的岩爆灾害,软岩则会表现出挤压大变形问题,严重影响深部工程安全。在这种条件下采用的支护体系不仅要具有较高的承载力,而且要能够适应较大的围岩变形而本身不发生破坏。提出了一种拉压耦合大变形锚杆,并详细介绍了它与围岩之间的相互作用机理。新型锚杆通过改善锚固结构,优化锚杆受力状态,提高了锚固结构的极限承载力,使锚杆杆体的变形性能得到充分的发挥,避免了传统锚杆因杆体不均匀变形导致的破坏问题。因而,高应力大变形条件下新型锚杆的锚固性能更优,更有利于保持围岩稳定。室内实验研究证实,在同等条件下拉压耦合锚杆的极限承载力明显大于传统锚杆,并且具有良好的大变形特性。针对矿山深部开采中遇到的软岩大变形和硬岩岩爆等灾害,新型锚杆将实现更优的加固效应。

The high stresses acting on rock masses in deep underground can cause serious stability problems such as squeezing of soft rocks and rock burst in hard rocks. The support system applied under high in-situ stress condition should be able to bear high loads and accommodate large deformation of rock masses without experiencing serious damage. A specifically designed rockbolt, called combination of tension and compression type yield bolt(CTC-yield bolt), is proposed. The inner thread segment and anchor compose the inner anchorage section of the bolt that is firmly fixed at the bottom of the borehole, while the smooth section of the bolt will elongate in response to rock deformation when the load exceeds its capacity. Such special structure can help avoid premature bolt failure due to the stress concentrations caused by fracture/joint opening. The static pull tests show that the new bolt has larger ultimate bearing capacity and better deformation property than the conventional rock bolt. The stress distribution at bolt-grout-rock interface is effectively optimized by the combined state of tension and compression of the grout inside and outside the anchor, thereby improving the anchorage force significantly. The deformation capacity of this new bolt is closely related to the length of its smooth section between the two anchors. The new bolt is expected to provide support for both the squeezing and the rock burst encountered in tunneling and mining engineering.