Gas breakthrough in saturated compacted GaoMiaoZi (GMZ) bentonite under rigid boundary conditions

2017 ◽  
Vol 54 (8) ◽  
pp. 1139-1149 ◽  
Author(s):  
L. Xu ◽  
W.M. Ye ◽  
B. Ye
Keyword(s):  
Water Retention ◽  
Swelling Pressure ◽  
Dry Density ◽  
Gmz Bentonite ◽  
Gas Migration ◽  
Migration Process ◽  
Rigid Boundary ◽  
Capillary Effects ◽  
Entry Pressure ◽  
Breakthrough Pressure

In a geological repository for disposal of high-level radioactive waste, gas breakthrough is an important phenomenon during a gas migration process in the saturated engineered barrier. In this paper, gas injection, swelling pressure, water permeability, and water retention tests were conducted on saturated compacted GaoMiaoZi (GMZ) bentonite to investigate the gas breakthrough mechanism. Results show that, for saturated GMZ bentonite tested under rigid boundary conditions, the gas breakthrough pressure is significantly larger than the swelling pressure and slightly lower than the gas entry pressure obtained from the water retention characteristic and the van Genuchten model. Gas breakthrough pressure deviates from the swelling pressure and approaches the calculated gas entry pressure as the dry density increases. Mechanical and capillary effects are both important to the gas migration process for specimens with lower dry densities, and the capillary effect becomes more important with the increase of dry density. The desaturation and shrinkage of the specimen will result in unexpectedly high and disordered interfacial gas flux. For specimens with higher dry densities, gas will only flow through interconnected larger pores, then result in minor desaturation–shrinkage of the specimen. Finally, a new model with consideration of both mechanical and capillary effects is proposed, which can accurately predict gas breakthrough pressure for a GMZ bentonite specimen.

Swelling Behaviour of GMZ Bentonite

2013 ◽  
Vol 671-674 ◽  
pp. 1756-1760
Author(s):  
De An Sun ◽  
Hai Bo Lv ◽  
Chang Fu Wei
Keyword(s):  
Initial Conditions ◽  
Matrix Material ◽  
Swelling Pressure ◽  
Dry Density ◽  
Gmz Bentonite ◽  
Swelling Behaviour ◽  
Deep Geological Disposal ◽  
Backfill Materials ◽  
Swelling Characteristics ◽  
High Level

Gaomiaozi (GMZ) bentonite has been chosen as a matrix material of buffer/backfill materials in the deep geological disposal to isolate the high level radioactive waste in China. Swelling characteristics of GMZ bentonite and its mixtures with sand wetted with water were studied by experimental methods. The tests result shows that the relation between void ratio and the swelling pressure of compacted GMZ bentonite-sand mixtures at full saturation is independent on the initial conditions such as initial dry density and water content, and dependent on the ratio of bentonite to sand. An empirical equation is proposed to predict the swelling deformation and pressure of the mixtures with different densities and bentonite/sand ratios.

scholarly journals Swelling Properties and Permeability of GMZ Bentonite-Sand Mixtures during Different Solutions Infiltration

2021 ◽  
Vol 13 (4) ◽  
pp. 1622
Author(s):  
Yu-Ping Wang ◽  
Zhe Wang ◽  
Yu Zhao ◽  
Fa-Cheng Yi ◽  
Bao-Long Zhu
Keyword(s):  
Swelling Pressure ◽  
Development Stage ◽  
Gmz Bentonite ◽  
Test Results ◽  
X Ray Diffraction ◽  
Swelling Properties ◽  
Swelling Capacity ◽  
Slow Expansion ◽  
Expansion Stage ◽  
Chemical Solutions

In China, Gaomiaozi (GMZ) bentonite is recognized as a barrier material for isolating nuclear waste. Different chemical solutions may change the hydraulic conductivity and swelling capacity of bentonite. Consequently, a series of swelling pressure and permeability experiments was carried out on bentonite-sand mixtures with various dry densities and infiltrating solutions. X-ray diffraction (XRD) and the field emission scanning electron microscope (FESEM) were carried out on the samples experiencing the tests to identify the influence of chemistry pore solutions upon the mineralogical and microstructure changes. The results show that the swelling pressure experienced rapid swelling, slow expansion, and the stable expansion stage for the specimens of infiltrating solutions except for NaOH. For the specimens infiltrated with NaOH solutions, the swelling pressure experienced rapid increases, slow decreases, and a stable development stage. With hyper-alkaline and hyper-salinity infiltration, the swelling pressure decreased, and the permeability increased. In addition, swelling pressure attained stability more quickly on contact with hyper-alkaline and hyper-salinity solutions. Comparing the test results, the results indicate that the influence of NaOH on the expansion and permeability was higher than NaCl-Na2SO4 at the same concentration.

scholarly journals Thermal Conductivity of Compacted GO-GMZ Bentonite Used as Buffer Material for a High-Level Radioactive Waste Repository

2018 ◽  
Vol 2018 ◽  
pp. 1-11 ◽  
Author(s):  
Yong-Gui Chen ◽  
Xue-Min Liu ◽  
Xiang Mu ◽  
Wei-Min Ye ◽  
Yu-Jun Cui ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Radioactive Waste ◽  
Water Content ◽  
Radioactive Waste Disposal ◽  
Dry Density ◽  
Gmz Bentonite ◽  
High Level Radioactive Waste ◽  
Buffer Material ◽  
High Level ◽  
Crucial Parameter

In China, Gaomiaozi (GMZ) bentonite serves as a feasible buffer material in the high-level radioactive waste (HLW) repository, while its thermal conductivity is seen as a crucial parameter for the safety running of the HLW disposal. Due to the tremendous amount of heat released by such waste, the thermal conductivity of the buffer material is a crucial parameter for the safety running of the high-level radioactive waste disposal. For the purpose of improving its thermal conductivity, this research used the graphene oxide (GO) to modify the pure bentonite and then the nanocarbon-based bentonite (GO-GMZ) was obtained chemically. The thermal conductivity of this modified soil has been measured and investigated under various conditions in this study: the GO content, dry density, and water content. Researches confirm that the thermal conductivity of the modified bentonite is codetermined by the three conditions mentioned above, namely, the value of GO content, dry density, and water content. Besides, the study proposes an improved geometric mean model based on the special condition to predict the thermal conductivity of the compacted specimen; moreover, the calculated values are also compared with the experimental data.

scholarly journals Numerical Modeling of Water and Gas Transport in Compacted GMZ Bentonite under Constant Volume Condition

Geofluids ◽  
2021 ◽  
Vol 2021 ◽  
pp. 1-16
Author(s):  
Jiang-Feng Liu ◽  
Xu-Lou Cao ◽  
Hong-Yang Ni ◽  
Kai Zhang ◽  
Zhi-Xiao Ma ◽  
...  
Keyword(s):  
Gas Transport ◽  
Water Saturation ◽  
Underground Water ◽  
Gas Production ◽  
Gas Pressure ◽  
Constant Volume ◽  
Gmz Bentonite ◽  
Gas Migration ◽  
Sealing Ability ◽  
High Level

During deep geological disposal of high-level and long-lived radioactive waste, underground water erosion into buffer materials, such as bentonite, and gas production around the canister are unavoidable. Therefore, understanding water and gas migration into buffer materials is important when it comes to determining the sealing ability of engineered barriers in deep geological repositories. The main aim of our study is to provide insights into the water/gas transport in a compacted bentonite sample under constant volume conditions. The results of our study indicate that water saturation is obtained after 450 hours, which is similar to experimental results. Gas migration testing shows that the degree of water saturation in the samples is very sensitive to the gas pressure. As soon as 2 MPa or higher gas pressure was applied, the water saturation degree decreased quickly. Laboratory experiments indicate that gas breakthrough occurs at 4 MPa, with water being expelled from the downstream side. This indicates that gas pressure has a significant effect on the sealing ability of Gaomizozi (GMZ) bentonite.

Coupling Swelling and Water Retention Processes in Compacted Bentonite

2011 ◽  
Vol 6 (1) ◽  
Author(s):  
Antti Lempinen
Keyword(s):  
Water Retention ◽  
Spent Nuclear Fuel ◽  
Effective Strain ◽  
Swelling Pressure ◽  
Model Parameters ◽  
Confined Water ◽  
Swelling Properties ◽  
Compacted Bentonite ◽  
Buffer Material ◽  
Swelling Factor

Compacted bentonite is the main candidate for buffer material in several plans for spent nuclear fuel repositories. One of its important properties is high swelling capacity, which is caused by interaction between water molecules and exchangeable cations. This interaction makes bentonite behave differently from capillary materials. In this article, a model for thermo-hydro-mechanical state of partially water saturated bentonite is presented. It couples the water retention and swelling properties with introduction of the swelling factor in effective strain. The Helmholz energy density determines the state with a relatively small set of independent parameters: swelling pressure, swelling factor, maximum confined water content and the reference state. The model parameters are determined from experimental data for FEBEX bentonite, and as a simple consistency check, confined suction curves are calculated and compared to test results. Consistency of the model with observations on nano- and microscale of bentonite is also discussed.

3D High Resolution Survey of Natural Seeps in the Campeche Sound

2003 ◽  
Author(s):  
Jaime Nu´n˜ez Farfa´n ◽  
Diego Cruz Roque ◽  
Pro´coro Barrera Nabor ◽  
Wilbert Koh Cambranis
Keyword(s):  
High Resolution ◽  
Oil Field ◽  
Geophysical Survey ◽  
Migration Route ◽  
Gas Migration ◽  
Migration Process ◽  
Shallow Gas ◽  
Volume Increase ◽  
Geophysical Study ◽  
Shallow Strata

In order to define the zones at risk by the shallow gas and natural seeps of hydrocarbons in the Campeche Sound, a 3D geophysical study of 4 areas has been carried out in the region of the Cantarell oil field [1]. The results of this high resolution survey were correlated with previous explorations and it was possible to define the migration route and evolution of the shallow gas accumulations. The volume increase of the accumulations detected can not be explained by the lack of precision of the instruments and is more likely connected to the exploitation of the reservoir. The faults that transport the hydrocarbons from the reservoir to shallow strata define an area that contains several important platforms likely to be affected by the gas migration process. This geophysical survey was also used to define the location of three geotechnical borings for studying the degradation on the properties of the soils due to the presence of hydrocarbons that support the platforms.

scholarly journals The Characteristics of Swelling Pressure for Superabsorbent Polymer and Soil Mixtures

Materials ◽  
2020 ◽  
Vol 13 (22) ◽  
pp. 5071
Author(s):  
Jakub Misiewicz ◽  
Arkadiusz Głogowski ◽  
Krzysztof Lejcuś ◽  
Daria Marczak
Keyword(s):  
Soil Structure ◽  
Water Retention ◽  
Swelling Pressure ◽  
Coarse Sand ◽  
Loamy Sand ◽  
Superabsorbent Polymer ◽  
Soil Water Retention ◽  
Proposed Model ◽  
Soil Mixtures ◽  
Time Required

Superabsorbent polymers (SAPs) are used in agriculture and environmental engineering to increase soil water retention. Under such conditions, the swelling pressure of the SAP in soil affects water absorption by SAP, and soil structure. The paper presents the results of swelling pressure of three cross-linked copolymers of acrylamide and potassium acrylate mixed at the ratios of 0.3%, 0.5% and 1.0% with coarse sand and loamy sand. The highest values of swelling pressure were obtained for the 1% proportion, for coarse sand (79.53 kPa) and loamy sand (78.23 kPa). The time required to reach 90% of swelling pressure for each type of SAP differs. Samples of coarse sand mixed with SAP K2 in all concentrations reached 90% of total swelling pressure in 100 min, while the loamy sand mixtures needed only about 60 min. The results were the basis for developing a model for swelling pressure of the superabsorbent and soil mixtures, which is a fully stochastic model. The conducted research demonstrated that the course of pressure increase depends on the available pore capacity and the grain size distribution of SAPs. The obtained results and the proposed model may be applied everywhere where mixtures of SAPs and soils are used to improve plant vegetation conditions.

WATER RETENTION AND SWELLING PRESSURE OF CLAY SOILS

1962 ◽  
Vol 42 (1) ◽  
pp. 189-196 ◽  
Author(s):  
B. P. Warkentin
Keyword(s):  
Water Retention ◽  
Swelling Pressure ◽  
Clay Soils

Water retention curves for three clay soils are compared with the best available estimates of swelling pressure to determine whether the expected equivalence is obtained. Between pF 3 and 4 swelling pressures show agreement with water retention forces. Above pF 4, the clays become unsaturated; below pF 3, forces of attraction not accounted for in the swelling pressure estimates make water retention lower than swelling pressure.A method for calculating theoretical swelling pressures is outlined.

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