| 摘要: | 低放射低放射性廢棄物最終處置場設施必須考慮的安全目標，是避免放射性物質外洩，處置場必須與生物圈長久隔離，因此使用多重障壁設計概念，其使用之回填材料以砂與膨潤土混合填充。回填材料為多重障壁其中一項重要隔阻元件，其需要具備適當的回脹潛能、低水力傳導度等其他性質，針對回填材料特性因地制宜的設計最終處置場，才能有效確保處置之安全及穩定。
本研究以室內實驗探討砂與膨潤土混合物在不同配比下之工程力學性質，分別以兩種膨潤土(MX-80及K-V1)且不同膨潤土含量之混合物(30%、40%、50%、60%、70%、80%、90%)，以無圍壓縮試驗得其抗壓強度及彈性模數。試驗過程中發現，試體製作方法影響試體均勻受力與否，膨潤土含量越大之混合材料影響越大，因此為使試體皆均勻受力，試體製作方法嘗試採用單向壓製、上下翻轉壓製、分層壓製、雙向壓製四種方式施作。
試驗結果顯示，(1)使用雙向壓製之試體製作方法，大多數的砂與膨潤土之混合材料能均勻受力；(2)膨潤土與矽砂之混合材料達最佳含水量時，K-V1的混合材料在膨潤土含量為50%具有最大平均抗壓強度；MX-80的混合材料則在膨潤土含量為60%具有最大平均抗壓強度；(3) 整體平均抗壓強度隨者膨潤土含量不同而不同，就兩種膨潤土材料比較，膨潤土含量大於60%之配比，MX-80之混合材料的平均抗壓強度皆較K-V1的混合材料的平均抗壓強度大；膨潤土含量小於60%之配比，K-V1的混合材料的平均抗壓強度皆較MX-80之混合材料的平均抗壓強度大。
關鍵字：膨潤土、回填材料、抗壓強度、彈性模數。
;The multiple barriers design is the main concept for radioactive waste repository system. These barriers (host rock, backfill, buffer, …) are the isolators that help to prevent the poisonous chemical leak to biosphere. Therefore, the barriers components must be robust and durable. Backfill is an important component of the barriers system and thus it need to meet some rigorous requirements about strength, swelling potential and low hydraulic conductivity to ensure the human being safety.
This study investigated the engineering and mechanical properties of mixtures by sand and bentonite with different ratio. Two bentonites (MX-80 and K-V1) and seven bentonite contents (30%, 40%, 50%, 60%, 70%, 80% and 90%) were tested to investigate the effect of the mixture content on the mechanical properties of backfill material. Compressive strength and elastic modulus were obtained by unconfined compression test. During the testing, it was found that the sample preparation technique has a considerable effect on the uniformity of sample, the more bentonite content of mixed material the more influence on its strength. In order to apply the loading on the sample uniformly, the preparation methods were tried in four ways: one-way loading, two-way loading, up and down turning, layer-by-layer compression.
Through the experiment program some conclusions can be draw. Firstly, the use of two-way loading preparation method could produce a more uniform specimen. Secondly, for K-V1 based mixture the maximal unconfined strength is reached where the ratio of bentonite is 50%. However, the highest strength of MX-80 based mixture archived where the ratio of bentonite is 60%. Second, comparing two mixture types where the ratio of bentonite over 60% the MX-80 based mixture has a larger strength than K-V1 based material and vice versa, where the ratio of bentonite lower than 60% the K-V1 based mixture has a higher strength.
Keywords: Bentonite, Backfill, Compressive strength, Elastic modulus |
