Development of design method for support system of cavern using cable bolt

在过去的二十年里，锚杆或锚索一直被用作地下洞室的主要支撑构件。然而，对于这些锚杆的支撑效果，人们还没有做出明确的解释。为了弄清这些锚杆的支护效果，对它们在拉拔试验中的失效机理进行了讨论。然后用锚杆与锚索的粘结强度解释了锚杆的主要支护作用，认为有必要进行更大范围的全球可视化，探讨锚注界面、注浆层和岩体的破坏机理。在此基础上，探讨了锚杆与锚索联合作用下洞室支护系统的设计方法。本研究首先利用X射线CT扫描仪对锚杆与锚索在拉拔试验中的破坏形态进行了可视化显示，为详细探讨锚杆与锚索的粘结破坏提供了基础数据。在拉拔试验中，对两种类型的锚杆和锚索进行了比较。结果表明，细观失效机制可分为不同的失效模式。其次，通过对拉拔试验的详细分析，提出了抗剪模型(SRM)。在此基础上，建立了基于开关磁阻电机的锚杆本构模型。结果表明，该本构模型可以较好地模拟锚杆在拉拔试验过程中的受力行为。在此基础上，利用SRM计算了锚索锚杆的特性曲线，并利用锚索锚杆进行了洞室支护设计。结果表明，该模型可方便地设计锚杆在洞室周围的埋深。

Rock bolts or cable bolts have been used as a primary support member of underground openings in the last two decades. However, a clear explanation for the support effect of those bolts has not been made sufficiently. In order to clarify the support effect of those bolts, the failure mechanism in a pull-out test of them has been discussed. Then a main support effect was explained by bond strength of rock bolts and cable bolts, and it is necessary to visualize wider area globally and to discuss the failure mechanism of bolt-grout interface, grout and rock mass. After the clarification, the design method for support system of cavern using rock bolts or cable bolts should be discussed.In this research, patterns of the failure in a pull-out test of rock bolt and cable bolt firstly were visualized by X-ray CT scanner to supply the basic data for the detail discussion on the bond failure of rock bolt and cable bolt. In the pull-out tests, a comparison was made between two types of rock bolts and cable bolts. From the results, it was shown that the microscopic failure mechanism is evaluated as the different failure mode. Secondly, the Shear Resistance Model(SRM) was suggested from analyses of the pull-out test in detail. Then the constitutive model of a cable bolt was constructed, based on the SRM. It was clarified that the behavior of cable bolt during the pull-out test can be simulated precisely using the constitutive model. Furthermore, the Characteristics Curve of Cable bolt(CCC) was calculated by the SRM, then a support design of cavern using cable bolts was performed, using the CCC. As a result, the suggested model was convenience for designing embedment length of cable bolt around a cavern.