Development of stress conditions around a tunnel excavated in argillaceous rock related to change of saturation conditions

含水状態の変化による泥岩層内トンネルの応力条件の変化について

上原 真一*; 小林 晃*; 千々松 正和*; 大西 有三*; 藤田 朝雄 

Uehara, Shinichi*; Kobayashi, Akira*; Chijimatsu, Masakazu*; Onishi, Yuzo*; Fujita, Tomoo

本論では、フランスTournemireにおける泥岩トンネルにおける水理-応力連成問題に関する数値解析結果について論ずるものである。その結果、過去の応力状況を表現することができ、これにより、坑道の飽和-不飽和サイクルが岩盤強度を低下させEDZを引き起こしたことが考察された。

This paper reports the results of calculations about coupled hydro-mechanical process in the domain around excavations at clay rock site at Tournemire, France. We operated the numerical modelling by using a Finite Element Method code named THAMES, on the assumption that swelling pressure is parallel to saturation ratio. The results of modelling indicated that saturation ratio changes seasonally at the domain within several tens cm from tunnel wall. This extension is similar to that of damage zone observed in the tunnel at Tournemire site in 1881, which supports the idea that the saturation-desaturation cycles has decreased the rock strength and caused damage zone extension. The modelling results also suggested that the consideration of swelling pressure could affect evolution of stress state abruptly.