分離元素法之岩栓支撐模式研究

Abstract

岩栓為現代隧道工法中主要使用的支撐構件，主要用途為抵抗節理面滑動及穩定懸浮岩塊。對於岩體力學行為之分析，由於塊體分離及滑動，以往連體力學較難詳盡的分析與探討，基於此因認為採用離散元素法(discrete element method，DEM)探討岩體力學行為是一條有效的研究途徑。基於顆粒力學分離元素法發展的PFC軟體，即為一常用之分析軟體，然而PFC中較少考慮到支撐工法對於模擬結果的影響且缺乏相對應之支撐元件，故本研究希望發展出岩栓支撐模式，使未來在模擬上能依情勢加入工程手法進行分析。 在考慮運算效率及岩栓建置速度上，本研究以平滑節理模式搭配平行鍵結作為岩栓支撐模式建構的基礎發展出一套新的岩栓模式，不僅能達到支撐效果，亦能更有系統性的打設所需之岩栓。首先透過與前人所進行的岩栓拉拔、受剪實驗結果比對並觀察曲線尖峰強度、勁度與試體破壞型態了解此模式的可行性。完成岩栓模式可行性驗證後，接著進行隧道案例模擬，比較在有無設置岩栓、不同岩栓長度、覆土深度等的情況下對隧道位移量之影響，探討本研究之岩栓在實際案例中的效果為何。本研究模擬結果結論如下: (1)本研究之岩栓模式能有效模擬岩栓之力學行為；(2)在相同條件下，此岩栓確實能有效降低隧道內的位移量；(3)此岩栓模式之模擬結果與實際案例大致相符，當岩栓長度越長、勁度越大時隧道之位移量則越低。

Rockbolt is one of the major support system for tunnel excavation. It is widely used to resist sliding of joint and stabilize suspension rock blocks. For the analysis of the mechanical behavior of rock mass, the conventional continuum mechanics was difficult to consider the separation and sliding of blocks. Therefore, discrete element method (DEM) provides an effective tool to investigate the rock mechanical behavior. However, in the DEM software PFC, the rock bolt behavior is less taken into account and the supporting element is lack. Hence, this study develop a rock bolt supporting model for the engineering practice. In this study, the proposed model was firstly verified with laboratory tensile and shear tests. Then a series of tunnel case simulations are conducted to compare the influence on the displacement of the tunnel under different conditions, such as with or without rockbolts, different rock bolt lengths, different overburden, and different rock bolt number. The simulation results of this study are summarized as follows: (1) The rock bolt model of this study can effectively present the mechanical behavior of the rock bolt; (2) Under the same conditions, the rock bolts can effectively reduce the inward displacement of the tunnel; (3) The simulation results are generally consistent with the actual cases.