Effects of Dry Density and Water Content on Mechanical Properties of Sand-Bentonite Buffer Material
Effects of Dry Density and Water Content on Mechanical Properties of Sand-Bentonite Buffer Material
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DOI：
10.1007/978-3-319-95750-0_9
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发表时间：
2018-07
期刊：
影响因子：
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通讯作者：
J. J. Kumara-J.;T. Kodaka
中科院分区：
文献类型：
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作者：
J. J. Kumara-J.;T. Kodaka
深部地质处置库缓冲材料的力学性能受多种因素的影响。深地质处置库工程屏障系统在退役后会受到当地地下水流的影响。缓冲材料含水量的变化会影响变形和吸力性能。研究了含水率和干密度对砂-膨润土缓冲材料力学性能的影响。对干密度分别为1400、1600和1800 kg/m3，含水率分别为6%、12%和18%的砂基膨润土试件进行了三轴压缩试验。利用新研制的双室式三轴试验装置，对试件的体积应变进行了测定。总吸力的标本进行了测量，使用冷却器镜湿度计技术。总吸力是在为吸力测量和三轴压缩试验准备的相同试样上测量的。结果表明，含水量降低偏应力，而干密度增加偏应力;含水量高时，含水量将饱和度相对较低的试件的应变软化行为改变为应变硬化行为。高围压（1.0 MPa）比低围压（0.1 MPa）更倾向于应变硬化行为。水含量也增加应变硬化行为。相反，干密度降低应变硬化行为，特别是在小围压下。结果还表明，干密度降低体积膨胀的幅度。高围压促进体积膨胀。虽然含水量降低摩擦性能，但在相对较低的干密度（1400和1600 kg/m3）下，它增加了粘结性能。相比之下，含水量降低了高干密度（1800 kg/m3）下的粘结性能。因此，微观尺度的分析将对此产生更多的见解。含水率对总吸力影响较大，干密度和围压对总吸力影响不大。
Mechanical properties of the buffer material of deep geological repository are influenced by various factors. The engineered barrier system of a deep geological repository is subjected to local groundwater flow after it is decommissioned. The changes in water content of buffer material could affect deformation and suction properties. In this study, the influence of water content and dry density on the mechanical properties of sand-bentonite buffer material were investigated. The triaxial compression tests were performed on sand-bentonite specimens of 1400, 1600 and 1800 kg/m3of dry density and 6, 12 and 18% of water content. The volumetric strains of specimens were evaluated using a newly built double-cell type triaxial testing apparatus. Total suction of specimens was measured using the chiller-mirror hygrometer technique. Total suction was measured on identical specimens prepared for suction measurement and triaxial compression tests. The results indicate that water content reduces deviator stress while dry density increases it. The results also suggest that water content changes strain-softening behaviour of relatively less saturated specimens into strain-hardening behaviour when water content is high. A high confining pressure (of 1.0 MPa) inclines towards strain-hardening behaviour than a small confining pressure (of 0.1 MPa). Water content also increases strain-hardening behaviour. In contrast, dry density reduces strain-hardening behaviour, particularly under a small confining pressure. The results also indicate that dry density reduces the magnitude of volumetric expansion. A high confining pressure encourages volumetric expansion. While water content decreases frictional behavior, it increases cohesive behaviour under a relatively low dry density (of 1400 and 1600 kg/m3). In contrasts, water content reduces cohesive behaviour under a high dry density (of 1800 kg/m3). Thus, a micro-scale analysis would produce more insights on this. While water content has huge influence on total suction, both dry density and confining pressure have no effects on it.