scholarly journals Soil-Water Characteristic Curves And Hydraulic Conductivity of Gaomiaozi Bentonite Pellet-Contained Materials

2021 ◽  
Author(s):  
Jianghong Zhu ◽  
Zhenyan Su ◽  
Huyuan Zhang
Keyword(s):  
Particle Size ◽  
Hydraulic Conductivity ◽  
Soil Water ◽  
Dry Density ◽  
Characteristic Curves ◽  
Factors Affecting ◽  
Unsaturated Hydraulic Conductivity ◽  
Long Time ◽  
Soil Water Characteristic Curves ◽  
High Level

Abstract The bentonite pellet-contained material (PCM) is a feasible material for the joint sealing of high-level radioactive waste repository. During the operation of the repository, the PCM will be unsaturated for a long time, and its water retention and permeability directly affect the buffer barrier seepage, nuclide migration, and joint healing. Moreover, the particle size of bentonite pellets and dry density are important factors affecting the performance of PCM. In this work, the pressure plate method and vapour equilibrium technique were utilized to test the soil-water characteristic curves (SWCCs) of the PCMs with different particle sizes and dry densities. The unsaturated hydraulic conductivity of the PCMs was predicted by combining the SWCC model and saturated hydraulic conductivity. The results showed that in the low suction range (20–1150 kPa), the dry density and particle size had a negative correlation with the water content at the same suction. In the high suction range (4200–309000 kPa), the dry density and particle size had little effect on the SWCC. The Gardner model was appropriate for describing the SWCC of PCM. In addition, the hydraulic conductivity of the PCM decreased with the increase in dry density, while increased with the increase in particle size. The influence mechanism of the SWCC and hydraulic conductivity was further discussed based on the scanning electron microscopy images and pore size distribution curves.

Factors affecting drying and wetting soil-water characteristic curves of sandy soils

2004 ◽  
Vol 41 (5) ◽  
pp. 908-920 ◽  
Author(s):  
Hong Yang ◽  
Harianto Rahardjo ◽  
Eng-Choon Leong ◽  
D G Fredlund
Keyword(s):  
Grain Size ◽  
Size Distribution ◽  
Soil Water ◽  
Grain Size Distribution ◽  
Sandy Soils ◽  
Water Entry ◽  
Matric Suction ◽  
Dry Density ◽  
Characteristic Curves ◽  
Soil Water Characteristic Curves

Drying and wetting soil-water characteristic curves (SWCCs) for five sandy soils are investigated using a Tempe pressure cell and capillary rise open tube. The test data are fitted to two SWCC equations using a least-squares algorithm. The obtained fitting parameters and some hysteretic behaviour are discussed and correlated with grain-size distribution parameters. A concept of total hysteresis is proposed to quantify the hysteresis of SWCC. The measured SWCC for one soil is also compared with the SWCC estimated from its grain-size distribution. The SWCC was also obtained at a high dry density for one of the soils. The results show that the shapes of the SWCCs are similar to the grain-size distributions of the soils and are affected by the dry density of the soil. A coarse-grained soil has a lower air-entry value, residual matric suction, and water-entry value and less total hysteresis than a fine-grained soil. The residual matric suction and water-entry value tend to approach the same value when the effective grain size D10 of the soil is small, in the range of 3-6 mm. SWCCs of uniform soils have steeper slopes and less total hysteresis than those of less uniform soils. Soils with a low dry density have a lower air-entry value and residual matric suction than soils with a high dry density. The SWCC predicted from grain-size distribution is found to be sufficiently accurate.Key words: soil-water characteristic curve, water content, suction, hysteresis, grain size.

scholarly journals A comparative study of soil-water characteristic curves for compacted lateritic soil – bacillus coagulans mixtures

2021 ◽  
Vol 337 ◽  
pp. 01001
Author(s):  
Kolawole Juwonlo Osinubi ◽  
Paul Yohanna ◽  
Adrian Oshioname Eberemu ◽  
Thomas Stephen Ijimdiya
Keyword(s):  
Hydraulic Conductivity ◽  
Comparative Study ◽  
Soil Water ◽  
Bacillus Coagulans ◽  
Lateritic Soil ◽  
Characteristic Curves ◽  
Suspension Density ◽  
Microbial Density ◽  
Soil Water Characteristic Curves ◽  
Set Up

A comparative study of soil-water characteristic curves (SWCCs) for compacted lateritic soil ̶ Bacillus coagulans (B. coagulans) mixtures for municipal solid waste (MSW) application was studied. Soil treatment was performed at approximately about one-third pore volume of the microbes (i.e., B. coagulans) for suspension densities of 0, 1.5×108, 6.0×108, 1.2×109, 1.8×109 and 2.4×109cells/ml, correspondingly. Soil specimens were prepared at optimum moisture content (OMC) of British Standard light (BSL) compaction energy. Cementation reagent was applied on the compacted soil and permitted to penetrate until partial saturation was achieved. A set-up of pressure plate extractor was employed to measure the volumetric water content, θ (VWC) in the laboratory for varying matric suctions with a minimum of 10 kPa up to a maximum of 1,500 kPa. The unsaturated hydraulic conductivity (UHC) and VWC were assessed using Brooks - Corey (BC) and Fredlund - Xing (FX) models. Largely, BC and FX models overrated the VWC. Also, the VWC decreased with higher matric suction for the two models considered and the laboratory measured values. The UHC predicted for matric suctions of 500 and 1,500 kPa initially decreased for B. coagulans suspension density up to 1.2×109 cells/ml for BC and FX models, with the exception of a few cases, but thereafter increased with increase in microbial density. For FX model at 1,500 kPa, UHC values of 2.42×10–9, 2.02×10–9, 9.31×10–10, 8.09×10–10 , 1.29×10–9 and 2.27×10–9m/s were recorded at 0, 1.5×108, 6.0×108, 1.2×109, 1.8×109 and 2.4×109cells/ml, respectively. In the case of BC model, values of 2.26×10–17, 1.41×10–14, 2.2×10–14, 4.6×10–19 , 3.25×10–17 and 2.45×10–14m/s were recorded at 0, 1.5×108, 6.0×108, 1.2×109, 1.8×109 and 2.4×109cells/ml, respectively. Thus, the FX model met the design maximum hydraulic conductivity value of 1 x 10–9 m/s requirement for MSW system when lateritic soil was treated with B. coagulans suspension density of 1.2×109 cells/ml, while the BC model satisfied the requirement for all the microbial densities considered and it is recommended for modelling of UHC of lateritic soil admixed with B. coagulans for MSW containment application.

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