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1.
膨润土加砂混合物膨胀特征试验研究 总被引：1，自引：0，他引：1
运用自行研制的膨胀仪对膨润土加砂混合物进行了一系列膨胀力及膨胀应变等膨胀特性的试验研究,分析了膨胀力随时间的变化规律、两向膨胀力之间的关系和膨胀应变与时间及吸水量之间的关系。试验研究表明,膨润土加砂混合物的最大膨胀力以及最大膨胀应变主要取决于混合物的最初干密度和膨润土含量,并且随着二者的增大而增大;膨润土加砂混合物的水平膨胀力与竖向膨胀力之比随着混合物干密度的增大减小,并且与干密度近似成线性关系;不同膨润土含量的膨润土加砂混合物的膨胀应变与时间成双曲线关系,与吸水量近似呈S型曲线关系,并且其最大膨胀应变与膨润土含量存在指数关系。试验结果对高放废物深处置库中的缓冲回填材料设计具有一定的参考价值。 相似文献
2.
Simplified evaluation for swelling characteristics of bentonites 总被引：9，自引：0，他引：9
Bentonite is currently planned to be used as buffer and backfill materials for repositories of high-level nuclear waste because these materials must have the swelling characteristics to seal the waste. In the design for buffer and backfill materials, we must choose the adequate bentonite among many kinds of bentonite in the world. The database of the swelling characteristics of various bentonites and its evaluation will be available when we will select the adequate bentonite. For this purpose, this study performed the laboratory tests on the swelling pressure and swelling deformation of four kinds of bentonite produced in Japan and the United States. These bentonites have different physicochemical properties. This study investigated the characteristics of swelling pressure and swelling deformation from the viewpoint of the physicochemical properties of each bentonite. Furthermore, this study also proposed the simplified evaluation of swelling characteristics of various bentonites on the basis of microscopic analysis. 相似文献
3.
膨润土与砂混合物的膨胀特性是评估核废料深层地质处置工程长期性能的重要指标。对比不同膨润土及其与砂混合物的膨胀试验结果可知,对纯膨润土及其低掺砂率混合物,浸水膨胀完成后蒙脱石孔隙比em与竖向应力?v在双对数坐标内呈惟一的线性关系,利用该线性关系可预测浸水完成后不同竖向应力下的体积变化量及不同初始状态对应的膨胀力;对高掺砂率混合物,在砂骨架形成之前,em-?v线性关系成立,随着竖向应力的增大,砂骨架形成,对应的em值脱离em-?v线性关系,混合物中掺砂率越大,脱离该线性关系时的竖向应力就越小。砂骨架形成前,砂颗粒被蒙脱石包围,外力由蒙脱石承担,最终变形量由试样中单位体积蒙脱石的含量决定;砂骨架形成后,竖向应力最终由砂骨架和蒙脱石共同承担。利用砂骨架孔隙比的概念可确定各种不同掺砂率混合物形成砂骨架时的应力起偏点。同时,还可确定混合物能够形成砂骨架的掺砂率范围。 相似文献
4.
混合型缓冲回填材料膨胀力试验研究 总被引：7，自引：1，他引：6
与纯膨润土相比,混合型缓冲回填材料（膨润土与石英砂混合物）能够实现防渗阻隔能力、热传导性能、力学强度和可施工性能的最佳组合。选用高庙子钠基膨润土（GMZ001）为缓冲回填材料的主料,添加不同比例的石英砂,对掺砂比分别为0、10%、20%、30%、40%和50%的膨润土-砂混合物压实试样进行室内试验。结果表明,混合物的液限、塑限随掺砂率的增大而线性降低;膨胀力随时间呈指数增长。初始含水率较大时,最大膨胀力随初始含水率的增大略有降低。掺砂率一定时,最大膨胀力随初始干密度指数增长。提出了有效黏土密度的概念,建立了一定初始含水率条件下,任意掺砂率和初始干密度的高庙子膨润土-砂混合物最大膨胀力归一化模型,为混合型缓冲回填材料膨胀力的预测与控制提供了依据。 相似文献
5.
Xu等[1] 提出基于膨润土表面分形模型的膨胀变形计算方法 Vw／Vm=kPDs-3(式1),并得到了Tsukinuno膨润土、Wyoming膨润土和MX-80膨润土的膨胀变形和膨胀压力(统称膨胀变形)的膨胀试验数据的验证。当时由于条件限制,存在两个问题:(1)膨润土的表面分维一般采用氮吸附法测量,由膨胀变形试验数据反算得到的膨润土表面分维没有得到氮吸附试验数据的验证; (2)在归一化吸水体积与压力的分形模型(式1)中,K是膨润土的物性常数,没有给出理论表达式,只是经验系数。本文采用氮吸附方法测量了高庙子Na基膨润土、高庙子Ca基膨润土、商用膨润土和Tsukinuno膨润土的表面分维,根据式(1)由表面分维计算膨胀变形,并与膨胀试验数据比较,验证膨胀变形的分形模型; 根据双电层理论,导出用双电层参数表示式(1)中K值的理论表达式,用于膨胀变形的计算,并与膨胀变形试验结果进行比较验证。 相似文献
6.
In the present study, influence of wetting–drying cycles on swelling pressures of sand–bentonite mixtures used in the construction
of sanitary landfills to have an impermeable liner was investigated before and after lime treatment of the mixtures. Swelling
pressure tests were conducted to see if the swelling pressures were affected by wetting–drying cycles. First series of specimens
were prepared as a mixture of sand and bentonite only. In the first series of specimens, sand was mixed with bentonite in
various proportions with their optimum water contents and compacted by using standard proctor energy. In the second series
of the specimens, lime in various proportions was added to the mixtures of sand–bentonite. Then, the sand–bentonite mixtures
stabilized by lime were compacted with the standard proctor energy at their optimum moisture contents. Five wetting–drying
cycles were performed on each specimen and values of swelling pressures were measured at the end of each cycle. Results of
swelling pressure tests indicated that the swelling pressure is decreased when lime is added to the mixtures. In addition,
decrements were observed on swelling pressures by wetting–drying cycles. The results of the experiments of this investigation
showed that the beneficial effect of lime stabilization to control the swelling pressures was partly lost by the wetting–drying
cycles. However, the test results indicated that the swelling pressures of the specimens made of sand–bentonite mixtures stabilized
by lime were lower than the swelling pressures of the specimens made of only sand–bentonite mixtures. 相似文献
7.
高庙子膨润土与砂混合物的土-水特征曲线 总被引：1，自引：0，他引：1
用滤纸法和压力板法对高庙子膨润土与福建砂的混合物进行试验研究,在不同孔隙比和不同膨润土与砂配合比情况下量测脱湿过程的土-水特征曲线,研究土-水特征曲线与孔隙比和配合比之间的关系。试验结果表明：在同一配合比下用饱和度与吸力表示土-水特征曲线时,其曲线随着孔隙比的减小向右上方移动,即当土样的吸力一定时,土样的饱和度随着孔隙比的减小而增大,当吸力小于10 MPa时,这种现象较为显著;在同一孔隙比下膨润土与砂混合物的土-水特征曲线随着膨润土的比例增加而向右上方移动,即混合物的进气值随着膨润土的比例增加而增大;另外,配合比以及孔隙比相同时,膨润土与福建砂的混合物的土-水特征曲线与日本产Kunigel膨润土与丰浦砂的混合物的土-水特征曲线非常接近。 相似文献
8.
Agapitus Ahamefule Amadi 《Environmental Earth Sciences》2013,70(6):2437-2442
Compacted soil–bentonite mixtures are finding wide application as buffer material for waste repositories for their favorable self-sealing qualities. The swelling properties of such materials which serve as a measure of their self-sealing capabilities and, thus, the efficiency of the repository in sealing off their contents from the environment are closely related to the chemistry of the leachate that emanate from the wastes. For this reason, the swelling parameters (namely swelling potential and pressure) of compacted lateritic soil–bentonite mixtures under consideration for use as barrier in municipal waste landfill were evaluated. Series of swelling potential and pressure tests were performed using variable content (0–10 %) of bentonite at predetermined optimum moisture content. Soil mixtures were compacted with British Standard Heavy compactive effort and saturated with processed tap water as well as three leachate solutions of varying ionic strength that were generated in active open dump landfills. Experimental results showed that swelling potential based on the free swell together with the maximum swell pressures of compacted soil mixtures measured at equilibrium increased approximately linearly with increase in the amount of bentonite when inundated with processed tap water and the three leachate solutions. On the other hand, these swelling parameters decreased as the ionic strength of the leachate solutions measured by their electrical conductivity increased for the various soil mixtures. These results provide an insight into the swelling behavior and the possible degradation in the efficiency of the proposed lateritic soil–bentonite mixtures in relation to their use as buffer material in waste landfills. 相似文献
9.
分形计算方法能较准确地计算膨润土的膨胀变形,但系数K没有确切的计算方法,限制了该方法的广泛应用。基于双电层（DDL）理论和分形方法在双电层膨胀下都适用的理论事实,提出在双电层膨胀条件下采用DDL理论推导出分形方法中系数K的方法,并计算出商用膨润土的K值为9.15。对商用膨润土进行了N2吸附试验,利用等温吸附数据计算出该膨润土的表面分维为2.65,然后根据得出的系数K和表面分维采用分形方法计算了膨润土的最大膨胀率并与膨胀试验结果作对比。结果表明,分形方法的理论计算和试验结果基本一致,尤其是在施加压力较大而膨胀变形较小的情况下,分形计算方法计算结果比起双电层理论更符合试验数据。 相似文献
10.
G.R. Alther 《Engineering Geology》1987,23(3-4):177-191
11.
Setianto Samingan Agus Yulian Firmana Arifin Snehasis Tripathy Tom Schanz 《Acta Geotechnica》2013,8(2):155-165
This paper presents results of an experimental work to determine a relationship between swelling pressure and suction of heavily compacted bentonite–sand mixtures. For comparison, tests were also carried out on heavily compacted bentonite specimens. A series of swelling pressure tests were performed using multi-step constant-volume method where suction of the specimens tested was reduced in a stepwise manner toward a zero value. The suction reduction was induced using vapor equilibrium and axis-translation techniques. It is shown that compacted specimens did not exhibit any collapse upon suction decrease and exhibited maximum swelling pressures at zero-equilibrium suction. The development of swelling pressure with decreasing suction of the specimens showed threshold suctions below which a further reduction in suction yields an increase in the swelling pressure of the same magnitude. The magnitude of threshold suction was found to be a function of bentonite content in compacted specimens. 相似文献
12.
对两种高庙子钠基膨润土（简称GMZ001和GMZ07）在不同初始干密度下进行膨胀力试验、常压力下的膨胀变形试验以及压缩试验。试验结果表明,GMZ001的膨胀能力要比GMZ07的大,并且GMZ001比GMZ07更难压实。对饱和后两种膨润土进行压汞试验和扫描电子显微镜测试后发现,在相同孔隙比下,GMZ07集聚体间孔隙较多,并且GMZ001集聚体的水化程度大于GMZ07。结合土工和微观试验的结果,认为导致两者力学性能差异的主要原因是由于颗粒粒径大小的差异以及蒙脱石含量的不同。最后利用蒙脱石孔隙比的概念对两种膨润土的浸水膨胀试验结果进行归一化,并对膨润土的膨胀特性进行了预测。 相似文献
13.
Liu Xiaoyan Congress Surya Sarat Chandra Cai Guojun Liu Songyu 《Acta Geotechnica》2021,16(5):1487-1507
Buffer/backfill material is an important engineering barrier in a deep geological repository of high-level radioactive waste (HLW). Its thermo-hydro-mechanical (THM) performance is very important for the safe and stable operation of the HLW repository system. Natural graphite powder mixed with sodium bentonite forms a buffer/backfill material that can dissipate heat quickly and provide strong isolation. In this paper, the THM characteristics of bentonite–sand–graphite–polypropylene fiber (BSGF) mixtures, used as a buffer/backfill material, were studied through a series of laboratory tests. The influence of graphite and polypropylene fiber contents on thermal conductivity, swelling pressure, hydraulic conductivity, and strength properties of BSGF mixtures with different sand contents was analyzed. Experimental results indicated that the graphite content, the maximum graphite mesh number, and the initial dry density of bentonite–graphite mixtures influenced the thermal conductivity of bentonite–graphite mixtures. The addition of polypropylene fiber was found to enhance the shear strength and inhibit cracking without significantly affecting the expansivity, permeability, and thermal conductivity of the BSGF mixtures. This study provides a new buffer/backfill material that can improve the stability, functionality, and thermal efficiency of the HLW repository.
相似文献14.
在不同初始条件下试验研究了静置时间对高庙子钠基膨润土GMZ07和MX80膨润土压实样热传导性能的影响。在保持试样干密度和含水率不变情况下,将不同初始状态试样分别静置1、5、30、60、100 d,随后采用热探针法进行热传导系数测试,并对部分试样进行压汞试验。试验结果表明：GMZ07和MX80膨润土的热传导系数均随静置时间的增长而减小,静置早期热传导系数减小较快,随着静置时间延续,热传导系数逐渐趋于稳定。在相同干密度下,静置时间引起的热传导系数减小量随含水率的增大而增大。结合压实膨润土试样的微观孔隙结构变化,认为膨润土热传导系数随静置时间发生变化的主要原因是：试样静置过程中,蒙脱石发生水化膨胀,部分土中水转变成热传导性能较差的惰性水,导致膨润土的热传导系数减小。 相似文献
15.
在高放废物处置库长期运营过程中包封容器将发生破坏,核素会向外界迁移,缓冲回填材料的水力传导系数是评价处置库工程屏障性能的重要指标。采用柔性壁渗透仪,研究2.0×10-5 mol/L的Eu(III)溶液作为渗入液时膨润土-砂混合物的渗透特性。结果表明,膨润土-砂混合物的水力传导系数K=(2.075.23)×10-10 cm/s;在05.23)×10-10 cm/s;在050%掺砂率范围内,膨润土-砂混合物吸水膨胀过程中渗透性能随掺砂率增大时没有明显的变化,能够满足高放废物处置库缓冲回填材料低渗透性的要求。使用有效黏土密度的概念,得到膨润土-砂混合物的体积膨胀率随初始有效黏土密度的增大呈指数增大的趋势;混合物水力传导系数的对数值与有效黏土密度存在良好的线性衰减关系;与蒸馏水相比,渗入液(ECDD)为2.0×10-5 mol/L的Eu(III)溶液时,膨润土-砂混合物的水力传导系数较小,可能是由于渗入液黏滞性的影响。 相似文献
16.
高放废物（HLW）深地质处置中,在膨润土中添加一定比例的石英砂能优化缓冲/回填材料的性能。利用水汽平衡法,对高庙子压实膨润土-砂混合物在不同温度、掺砂率和干密度条件下的土-水特征曲线（SWCCs）进行试验研究,分析温度、掺砂率与干密度对混合物土-水特征曲线的影响。试验结果表明,随着温度升高,混合物的持水能力明显下降;在试验控制吸力范围内,低吸力段掺砂率对土-水特征曲线影响明显,高吸力段掺砂率对混合物土-水特征曲线的影响逐渐降低;干密度对混合物的土-水特征曲线基本没有影响。根据试验数据建立了不同温度和掺砂率条件下膨润土-砂缓冲/回填材料土-水特征曲线的经验公式,可用来预测不同温度和掺砂率条件下的膨润土-砂混合型缓冲/回填材料土-水特征曲线 相似文献
17.
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。 相似文献
18.
M. L. Kuleshova N. N. Danchenko V. L. Kosorukov V. I. Sergeev T. G. Shimko 《Moscow University Geology Bulletin》2017,72(4):290-298
Five bentonite samples of different compositions and geneses were saturated with Cs and Sr in the static regime. Desorption is examined during the filtration of distilled water through saturated samples. Both elements are firmly retained to most of the bentonite samples. The Cs and Sr desorption values were 12–20%, and 2.5–23%, respectively. Structural changes in the clay fraction of bentonites resulted from the sorption–desorption of Cs and Sr were studied by the method of X-ray diffraction. 相似文献
19.
Tadikonda Venkata Bharat Puvvadi Venkata Sivapullaiah Mehter M. Allam 《Environmental Earth Sciences》2013,70(1):303-314
Bentonite clays are proven to be attractive as buffer and backfill material in high-level nuclear waste repositories around the world. A quick estimation of swelling pressures of the compacted bentonites for different clay–water–electrolyte interactions is essential in the design of buffer and backfill materials. The theoretical studies on the swelling behavior of bentonites are based on diffuse double layer (DDL) theory. To establish theoretical relationship between void ratio and swelling pressure (e versus P), evaluation of elliptic integral and inverse analysis are unavoidable. In this paper, a novel procedure is presented to establish theoretical relationship of e versus P based on the Gouy–Chapman method. The proposed procedure establishes a unique relationship between electric potentials of interacting and non-interacting diffuse clay–water–electrolyte systems. A procedure is, thus, proposed to deduce the relation between swelling pressures and void ratio from the established relation between electric potentials. This approach is simple and alleviates the need for elliptic integral evaluation and also the inverse analysis. Further, application of the proposed approach to estimate swelling pressures of four compacted bentonites, for example, MX 80, Febex, Montigel and Kunigel V1, at different dry densities, shows that the method is very simple and predicts solutions with very good accuracy. Moreover, the proposed procedure provides continuous distributions of e versus P and thus it is computationally efficient when compared with the existing techniques. 相似文献
20.
我国各地膨润土的矿物学性质 总被引：24，自引：3，他引：24
运用X射线衍射分析技术对我国不同产地膨润土的矿物学性质进行考察；利用K值法测蒙脱石含量。实验表明，各地膨润土具有蒙脱石的含量较高且均为二八面体的矿物学特点；可能由于所处的矿层或局部地球化学环境不同，使得相同矿床的不同颜色膨润土矿物的蒙脱石含量有所差异。 相似文献