刘毅. 2016: 高庙子膨润土水化膨胀特性及其微观机理研究. 工程地质学报, 24(3): 451-458. DOI: 10.13544/j.cnki.jeg.2016.03.015
    引用本文: 刘毅. 2016: 高庙子膨润土水化膨胀特性及其微观机理研究. 工程地质学报, 24(3): 451-458. DOI: 10.13544/j.cnki.jeg.2016.03.015
    LIU Yi. 2016: INVESTIGATION ON THE SWELLING PROPERTIES AND MICROSTRUC-TURE MECHANISM OF COMPACTED GAOMIAOZI BENTONITE. JOURNAL OF ENGINEERING GEOLOGY, 24(3): 451-458. DOI: 10.13544/j.cnki.jeg.2016.03.015
    Citation: LIU Yi. 2016: INVESTIGATION ON THE SWELLING PROPERTIES AND MICROSTRUC-TURE MECHANISM OF COMPACTED GAOMIAOZI BENTONITE. JOURNAL OF ENGINEERING GEOLOGY, 24(3): 451-458. DOI: 10.13544/j.cnki.jeg.2016.03.015

    高庙子膨润土水化膨胀特性及其微观机理研究

    INVESTIGATION ON THE SWELLING PROPERTIES AND MICROSTRUC-TURE MECHANISM OF COMPACTED GAOMIAOZI BENTONITE

    • 摘要: 膨润土具有遇水膨胀的特性,是高放核废料深地质处置库理想的缓冲回填材料。膨胀特性是其作为缓冲材料最重要的性能之一,同时受多方面因素的影响。本文以我国首选缓冲材料高庙子膨润土为研究对象,以含水率和干密度为控制变量,以恒体积法为试验方法,研究了高压实高庙子膨润土的水化膨胀特性,采用压汞试验法(MIP)对膨润土微观结构进行了研究,并以此对水化膨胀特性进行了解释。膨胀力试验结果表明,高庙子膨润土的膨胀力发展形式和最大膨胀力均受试样含水率和干密度影响,干密度较小时,水化曲线呈明显的双峰结构,干密度较大时,水化曲线形态与含水率相关,随着含水率增大,双峰结构逐渐消失。MIP试验结果表明,高庙子膨润土的孔径分布同样受含水率和干密度影响,随着含水率和干密度降低,集合体间大孔隙体积增多。膨润土的水化膨胀曲线受集合体间大孔隙影响显著。大孔隙较多时,膨润土集合体能迅速膨胀形成临时结构,当膨胀力超过临时结构的极限荷载时发生坍塌,膨胀力回落,内部结构重组后继续水化达到最大膨胀力,因此其水化膨胀曲线呈明显的双峰结构。随着大孔隙量减少,水化膨胀曲线由双峰结构演变成一条平滑曲线。

       

      Abstract: Bentonite has the property of swelling when meeting water. It is a desirable buffer/backfill material in the deep geological disposal for high-level radioactive waste. The expansibility is one of the most important properties for bentonite as the buffer/backfill material, and is influenced by a number of factors. For study the expansibility of bentonite, Gaomiaozi(GMZ)bentonite was taken as the research object. Gaomiaozi(GMZ)bentonite had been proposed as the first choice of buffer/backfill material for the high-level radioactive waste disposal in China. Its expansibility was studied by the constant volume swelling test method which is one of the commonest methods for measuring the swelling pressure of bentonite. In these tests, water content and dry density were chosen as the control variable. Two types of dry density and three types of water content were adopted in the tests. Results of the swelling tests show that the shape of swelling curves and the maximum swelling pressure depend on the water content and dry density of the bentonite samples. There are conspicuous double-peak shapes of the swelling curve for the samples with low dry density. When the dry density is high, the swelling curves have different shapes with different water contents. The curve's shapes change from double-peak to smooth curve with the water content increasing. For analysis of the results of swelling tests, the mercury intrusion porosimetry(MIP)test has been carried out. MIP test results indicate that the pore size distribution curves of samples also depend on the water content and dry density, with the volume of inter-aggregate pores increasing as the water content or dry density decreases. In accordance with the relevant researches, the swelling curve of GMZ bentonite is deeply influenced by the volume of the inter-aggregate pores. When meeting water, the bentonite aggregates absorb water and swell quickly. When the inter-aggregate pores are large enough, there will be sufficient space for swelled aggregates to form a provisional structure. The provisional structure will collapse with the swelling pressure reach the limit load. Then the measured pressure fall and inner structure of bentonite recombination. The hydration is continuous so that the curve will get the second peak. Therefore, a double-peak structure can be observed when the space of inter-aggregate is great. With the volume of inter-aggregate pore decrease, the swell curve of bentonite changes from a double-peak structure to a smooth curve.

       

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