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既存亀裂を考慮した粒状体個別要素法によるHLW処分坑道の力学挙動解析

Distinct element analysis for mechanical behavior in HLW disposal tunnel considering pre-existing cracks

清水 浩之*; 小山 倫史*; 千々松 正和*; 藤田 朝雄; 中間 茂雄

Shimizu, Hiroyuki*; Koyama, Tomofumi*; Chijimatsu, Masakazu*; Fujita, Tomoo; Nakama, Shigeo

本研究では、スウェーデンのエスポ地下研究所で実施されたHLW地層処分に向けた原位置試験を対象とした、既存亀裂の存在を考慮した二次元粒状体個別要素法による熱-応力連成解析を行った。解析の結果、既存亀裂の割合が多くなるほど一軸圧縮試験及び圧裂試験のシミュレーションから得られるモデル全体としてのヤング率や圧縮・引張強さが小さくなり、既存亀裂を導入することで実際の岩石における寸法効果と同様の効果を定性的に再現できることが確認できた。また、掘削による応力解放及び加熱による岩盤内の亀裂進展をシミュレーションによって表現することができ、原位置試験で観測された結果と比較的良い一致を示した。

In this paper, the coupled thermal-mechanical processes in the $"A$sp$"o$ pillar stability experiments (APSE) were simulated using Distinct Element Method (DEM). By considering pre-existing cracks in the rock model, mechanical response of the rock during excavation phase and heating phase were successfully represented by DEM. Simulation results agree qualitatively well with the experimental results. However, the microcracks in the simulation were widely distributed around the heater and exfoliation of rock surfaces observed in the ${it in-situ}$ experiment was not formed accurately. To simulate more realistically the experimental results by the DEM models, the calibration of the microscopic parameters considering the model scale should be done. Moreover, more detailed discussion on the excavation damaged zone around the borehole and the distribution of pre-existing cracks are required.

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