兰州大学机构库 >土木工程与力学学院
膨润土颗粒材料的工程性能研究
Alternative TitleEngineering properties of granular bentonite materials for HLW disposal
马国梁
Thesis Advisor张虎元
2018-04-01
Degree Grantor兰州大学
Place of Conferral兰州
Degree Name硕士
Keyword高放废物处置 膨润土颗粒材料 微观结构 水力学性质 压缩性质
Abstract

膨润土颗粒材料是一种优良的缓冲回填材料,它由高密度的膨润土颗粒与膨润土粉末组成。膨润土颗粒材料可以填充砌块与围岩之间的接缝,也可以回填运输通道等。它具有易于压实、较好的膨胀性能、防渗性能以及可以填充不规则孔隙等优点。由于硐室空间的限制,膨润土颗粒材料较难压实,部分膨润土颗粒材料将会以堆积状态存在于硐室中。作为工程屏障的组成部分,堆积膨润土颗粒材料的工程性能将会对高放废物处置库的工程屏障造成一定影响。为了评价处置库的整体性能,有必要对堆积状态下的膨润土颗粒材料的工程性能进行研究。为探讨级配对堆积膨润土颗粒材料的膨胀性能、渗透性能和压缩变形性能的影响,本文选取了四种膨润土颗粒材料,并以膨润土粉末材料作为对比,开展了自由膨胀率试验、膨胀率试验、渗透试验以及压缩试验。五种材料的分别为K5F材料(0%颗粒率,5-2 mm粒组的颗粒与粉末组成)、K2F材料(70%颗粒率,2-1 mm粒组的颗粒与粉末组成)、KAF材料(粒径小于5 mm的颗粒,按富勒级配组成)、K材料(5-0.5mm粒径范围内的颗粒组成)以及F材料(膨润土粉末)。

试验结果表明:在天然含水状态下,四种膨润土颗粒材料的堆积干密度比膨润土粉末的堆积干密度大。其中K5F材料和KAF材料的堆积密度较大且相近。膨润土颗粒材料的自由膨胀率与堆积密度呈正比,但是相同质量的膨润土颗粒材料膨胀后的体积与颗粒率呈负相关关系。级配主要通过堆积密度来影响膨润土颗粒材料的无荷载最终膨胀率。膨润土颗粒材料的堆积密度越大,最终膨胀率越大。但是,膨润土颗粒材料的初始结构对最终膨胀率也具有一定影响,K5F的堆积密度比膨润土粉末压实样的干密度小0.003 g/cm3时,K5F的最终膨胀率比膨润土粉末压实样的最终膨胀率大2.9%。

四种堆积膨润土颗粒材料饱和后的渗透系数在10-9 cm/s的数量级。干密度不再是控制膨润土颗粒材料渗透性能的主要影响因素。当含水量小于13%时,在相同压力作用下,膨润土颗粒材料压缩后的干密度比膨润土粉末压缩后的干密度大,并且堆积膨润土颗粒材料的压缩系数比膨润土粉末材料堆积后的压缩系数小,抗压性能高。其中K5F材料和KAF材料的堆积密度较大,并且压缩后具有较大的干密度。当含水量大于13%时,在低压力作用下,膨润土颗粒材料压缩后的干密度甚至比膨润土粉末压缩后的干密度低;在高压力作用下,膨润土颗粒材料压缩后的干密度与膨润土粉末压缩后的干密度差异较小,曲线表现出收敛的趋势。

Other Abstract

Granular bentonite materials are some kinds of buffer/backfill materials with good performance, which are constituted by bentonite pellets and bentonite powder. The materials can be used to backfill pores between bentonite blocks and surrounding rocks, transportation tunnels and so on. The materials have several advantages, such as, easy to compaction, strong expansibility, low permeability and self-healing ability. The materials can also fill irregular pores. However, as a result of limited sizes of tunnels, some granular bentonite materials will not be compacted, and stay in their packing state. In order to evaluate overall performance of HLW depository, as a component of engineering barrier, the performance of packing granular bentonite materials need to be studied solely.In order to study expansibility, permeability and compressibility of packing granular bentonite materials, four kinds of granular bentonite materials, as the compacted/packing bentonite powder had been selected. Including K5F (70% pellets sized between 5-2mm, mixed with powder), K2F (70% pellets sized between 2-1mm, mixed with powder), KAF (Mixed by pellets sized smaller than 5mm with Fuller grain size distribution), K (Mixed by pellets sized between 5-0.5mm), F (Bentonite powder). Free swelling ratio tests, swelling strain tests, permeability tests and compressibility tests had been conducted on these four granular bentonite materials as powder the reference.

The results showed that, under natural moisture conditions, granular bentonite materials had higher packing dry densities than bentonite powder. Among these four selected materials, K5F material and KAF material had almost the same dry densities and their densities higher than the other two materials.

Free swelling ratio of granular bentonite materials was proportional to packing dry density. The volume of full-expanded granular bentonite materials was in reverse proportion to pellet ratio.Gradation influenced the final swelling strains through the packing dry densities of granular bentonite materials. The final swelling strains were in proportion to packing dry densities of granular bentonite materials. However, initial structures of granular bentonite materials had some influences on final swelling strains. When packing dry density of K5F is 0.003 g/cm3 smaller than dry density of compacted bentonite powder, the final swelling strain of K5F is l2.9% larger than bentonite powder.

Saturated permeability of four granular bentonite materials had been in the order of 10-9 cm/s. Dry density is no longer the control factor.When the moisture contents were smaller than 13%, compacted dry densities of granular bentonite materials under a constant load were larger than those of bentonite powder. Compressibility of granular bentonite materials was smaller than that of bentonite powder. Among these four granular bentonite materials, K5F and KAF had higher packing and compacted dry densities. When the moisture contents were higher than 13%, under lower pressure, compacted dry densities of granular bentonite materials were smaller than those of bentonite powder. Under higher pressure, compacted dry densities of granular bentonite materials were almost the same as those of bentonite powder.

URL查看原文
Language中文
Document Type学位论文
Identifierhttps://ir.lzu.edu.cn/handle/262010/226052
Collection土木工程与力学学院
Recommended Citation
GB/T 7714
马国梁. 膨润土颗粒材料的工程性能研究[D]. 兰州. 兰州大学,2018.
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