板岩葉理之非線性破壞準則及其邊坡穩定分析應用

Abstract

板岩邊坡中傾倒破壞為其中一種主要破壞型態，板岩弱面的強度主導整體邊坡的安全性。為了探討板岩葉理強度與決定其破壞包絡線，本研究進行一系列之張力試驗與岩石直接剪力試驗，並且利用實驗結果建立非線性葉理破壞準則。此外，本研究將所提出之非線性葉理破壞準則運用至UDEC中模擬板岩邊坡之傾倒破壞，以探討非線性葉理破壞準則與其他準則之差異。本研究結果總結如下：(1) 板岩葉理面破壞曲線實驗結果顯示，在低正向應力時，其呈現高度非線性，此時之摩擦角明顯高於高正向應力時之摩擦角；(2) 比較乾燥與溼式實驗結果發現，試體呈現遇水弱化情況；(3) 採用非線性破壞準則模擬之結果較線性破壞準則更能表現出張裂情況與傾倒行為且其分析結果較為保守；(4) 非線性葉理破壞準則的常數項參數α與指數項參數β皆與材料強度正相關，降低α或β將使邊坡更易發生傾倒破壞及破壞面傾角下降，而破壞面傾角下降將導致破壞區擴大。

Toppling failure is one major failure types of slate slope, and the strength of the weak planes of slate dominate the safety of the overall rock slope. To determine the strength and the failure envelope of slate foliation, this study include a series of pull-off test and direct shear tests, which results are used to establish a nonlinear foliation failure criterion. Furthermore, the proposed failure criterion is implemented in UDEC to simulate toppling failure of slate slopes. It explores the difference between the nonlinear foliation failure criterion and other criteria. The results of this study are summarized as follows. First, the experiment results show that the failure criteria of foliation is highly nonlinear under low normal stress. In addition, the friction angle under low normal stress is significantly higher than that under high normal stress. Second, comparing with the results from dry and wet condition, the slate exhibits wet-weakening effect. Third, the results which are exhibited by the simulation based on the proposed failure criterion could be more reasonable and conservative than those based on the linear failure criterion. Finally, the constant term α and the exponential term β of the nonlinear foliation failure criterion positively correlate with the material strength. By decreasing α or β, the slope is prone to occur toppling failure and the decrease of the angle of failure. In fact, the latter leads to expansion of the failure zone.