高放废物处置缓冲材料砌块抗压强度特性试验研究

Compressive Strength Characteristics of Compacted Buffer Blocks for High-Level Radioactive Waste Repository

缓冲材料是高放废物处置库中最后一道工程屏障材料,起着防止废物罐发生机械破坏和维护处置库结构长期安全稳定等作用。以缓冲材料砌块为研究对象,开展了不同制样方式下缓冲材料砌块的无侧限抗压强度特性试验,探讨了常规单向压实、双向压实及大型砌块取芯制样对砌块抗压强度的影响,从试样破坏形态和干密度分布等方面分析了不同制备条件下缓冲材料砌块抗压强度的差异性。实验结果表明:小型压实试样的干密度在压制高度方向上有较大差异,单向压实试样的差异比双向压实试样更大。单向压实试样顶部干密度最大,底部干密度最小;双向压实试样中部干密度最小,逐渐向两端增大,呈对称分布。小型压实试样在单轴压缩时,裂纹总是从干密度最低的部位开始发展。在相同干密度和含水率条件下,大型砌块取芯试样的无侧限抗压强度明显高于小型压实试样的抗压强度,双向压实试样的抗压强度为大型砌块取芯试样的70%,而常规单向压实试样的抗压强度仅为大型砌块取芯试样的47%。研究结果可为高放废物地质处置库工程屏障的设计提供参数依据和理论支撑。

Buffer material is the last engineering barrier for high-level radioactive waste repository,which prevent the mechanical damage of the canister and keep the canister in its centered position in the deposition hole as long as required with respect to the safety of the repository.The unconfined compressive strength characteristics of the buffer blocks under different sample preparation methods were conducted.The influence of conventional uniaxial compaction and biaxial compaction for small samples,and the cored samples from large block on unconfined compressive strength was discussed.The difference of compressive strength of buffer blocks under different preparation conditions was analyzed from the aspects of specimen failure mode and dry density distribution.The experimental results show that the dry density is quite different in the height of small compacted samples,and the difference of uniaxial compacted samples is larger than that of biaxial compacted samples.The dry density at the top of uniaxial compacted sample is the largest,and the dry density at the bottom is the smallest.The dry density in the middle of the biaxial compacted sample is the smallest and exhibits a symmetrical distribution.Damage was first observed at the lowest dry density part in the small compacted samples during uniaxial compression experiments.Under the same dry density and water content condition,the unconfined compressive strength of cored samples from large block was obviously higher than that of small compacted samples.The compressive strength of the biaxial compacted samples is 70%of cored samples from large block,while the unconfined compressive strength of conventional uniaxial compacted samples is only 47%of cored samples from large block.The research results will provide parameter basis and theoretical support for the design of engineering barrier of high-level radioactive waste repository.