scholarly journals Undrained Behavior of Microbially Induced Calcite Precipitated Sand with Polyvinyl Alcohol Fiber

2019 ◽  
Vol 9 (6) ◽  
pp. 1214 ◽  
Author(s):  
Sun-Gyu Choi ◽  
Tung Hoang ◽  
Sung-Sik Park
Keyword(s):  
Hydraulic Conductivity ◽  
Polyvinyl Alcohol ◽  
Friction Angle ◽  
Triaxial Tests ◽  
Calcite Precipitation ◽  
Environment Friendly ◽  
Ottawa Sand ◽  
Polyvinyl Alcohol Fiber ◽  
Constant Head ◽  
Undrained Behavior

Microbially induced calcite precipitation can cement sand and is an environment-friendly alternative to ordinary Portland cement. In this study, clean Ottawa sand was microbially treated to induce calcite contents (CCs) of 0%, 2%, and 4%. Polyvinyl alcohol fiber was also mixed with the sand at four different contents (0%, 0.2%, 0.4%, and 0.6%) with a constant CC of 4%. A series of undrained triaxial tests was conducted on the treated sands to evaluate the effects of the calcite treatment and fiber inclusion. Their hydraulic conductivity was also determined using a constant head test. As the CC increased from 0% to 4%, the friction angle and cohesion increased from 35.3° to 39.6° and from 0 to 93 kPa, respectively. For specimens with a CC of 4%, as the fiber content increased from 0% to 0.6%, the friction angle and cohesion increased from 39.6° to 42.8° and from 93 to 139 kPa, respectively. The hydraulic conductivity of clean Ottawa sand decreased by a factor of more than 100 as the CC increased from 0% to 4%. The fiber inclusion had less effect on the hydraulic conductivity of the specimen with 4% CC.

Influence of Density on the Hydraulic and Mechanical Properties of Sands

2014 ◽  
Vol 580-583 ◽  
pp. 659-664
Author(s):  
Osvaldo de Freitas Neto ◽  
Olavo Francisco dos Santos Jr. ◽  
Ricardo Nascimento Flores Severo
Keyword(s):  
Shear Strength ◽  
Hydraulic Conductivity ◽  
Triaxial Compression ◽  
Friction Angle ◽  
Coarse Fraction ◽  
Direct Shear ◽  
Direct Shear Tests ◽  
Strength Tests ◽  
Constant Head ◽  
Direct Shear Testing

This article aims at assessing the influence of relative density on the hydraulic conductivity and shear strength of two sands, denominated S01 and S02, derived from different regions and formation processes. S01 is wind-blown and S2 alluvial. The results of characterization and hydraulic conductivity in constant head tests were presented for both samples. The results of direct shear tests with sand S01 prepared with 5 different void ratios were also presented, for a vertical stress of 100kPa. The S02 sample was prepared with 4 different void ratios and these underwent direct shear testing with vertical stresses of 25kPa and 150kPa. This sample was prepared with the maximum and minimum void ratio and submitted to strength tests at CD triaxial compression with confining stresses of 50kPa, 100kPa and 200kPa. Results showed that even with different grain sizes, and under different density conditions, there were no significant variations in the permeability of the materials. With respect to shear strength, sand S01 obtained higher angle of friction values than sand S02, even though the latter had a higher percent coarse fraction. Sand S02 was relatively similar in terms of friction angle values obtained in direct shear and triaxial compression strength tests.

Shear strength, interparticle locking, and dilatancy of granular materials

2007 ◽  
Vol 44 (5) ◽  
pp. 579-591 ◽  
Author(s):  
Peijun Guo ◽  
Xubin Su
Keyword(s):  
Granular Materials ◽  
Stress Ratio ◽  
Peak Stress ◽  
Friction Angle ◽  
Substantial Effect ◽  
Triaxial Tests ◽  
Ottawa Sand ◽  
Confining Pressures ◽  
Limestone Sand ◽  
Crushed Limestone

The effect of particle angularity on the strength and dilation of granular materials is investigated through a series of laboratory tests on two materials, Ottawa standard sand (Sand O) and crushed limestone (Sand L), that are made up of rounded and angular particles, respectively. Triaxial tests on both materials at different confining pressures and initial void ratios show that particle angularity has a substantial effect on both the peak friction angle ϕp and the mobilized friction angle at the onset of dilation, ϕf. It is found that ϕf is smaller than the critical friction angle ϕcv for Ottawa sand; nevertheless ϕf is larger than ϕcv for Sand L owing to interparticle locking induced by particle angularity. The experimental results clearly show the contributions to shear resistance from both dilation and interlocking, with interlocking still largely existing at the peak stress ratio but not at the critical state. Suggestions are made to modify the stress–dilatancy formulations for sand to take into account the effect of interparticle locking associated with particle angularity.Key words: granular material, dilatancy, interlocking, and particle shape.

An efficient biotreatment process for polyvinyl alcohol containing textile wastewater

2013 ◽  
Vol 8 (3-4) ◽  
pp. 469-478 ◽  
Author(s):  
Sandip S. Magdum ◽  
Gauri P. Minde ◽  
Upendra S. Adhyapak ◽  
V. Kalyanraman
Keyword(s):  
Polyvinyl Alcohol ◽  
Process Optimization ◽  
Textile Wastewater ◽  
Cost Effective ◽  
Chemical Oxidation ◽  
High Rate ◽  
Microbial Consortia ◽  
Environment Friendly ◽  
Candida Sp ◽  
Textile Wastewater Treatment

The aim of this work was to optimize the biodegradation of polyvinyl alcohol (PVA) containing actual textile wastewater for a sustainable treatment solution. The isolated microbial consortia of effective PVA degrader namely Candida Sp. and Pseudomonas Sp., which were responsible for symbiotic degradation of chemical oxidation demand (COD) and PVA from desizing wastewater. In the process optimization, the maximum aeration was essential to achieve a high degradation rate, where as stirring enhances further degradation and foam control. Batch experiments concluded with the need of 16 lpm/l and 150 rpm of air and stirring speed respectively for high rate of COD and PVA degradation. Optimized process leads to 2 days of hydraulic retention time (HRT) with 85–90% PVA degradation. Continuous study also confirmed above treatment process optimization with 85.02% of COD and 90.3% of PVA degradation of effluent with 2 days HRT. This study gives environment friendly and cost effective solution for PVA containing textile wastewater treatment.

Enhancing the crystallization of biodegradable poly(ε-caprolactone) using a polyvinyl alcohol fiber favoring nucleation

2021 ◽  
pp. 179065
Author(s):  
Yi Li ◽  
Shilong Yao ◽  
Hechang Shi ◽  
Ye Zhang ◽  
Changyu Han ◽  
...  
Keyword(s):  
Polyvinyl Alcohol ◽  
Polyvinyl Alcohol Fiber ◽  
Biodegradable Poly

scholarly journals Formation Behavior of Polyiodine Complex in Photocrosslinked Polyvinyl Alcohol Fiber Spun by Electrospinning Method

2018 ◽  
Vol 31 (4) ◽  
pp. 569-574
Author(s):  
Sho Fujisawa ◽  
Masumi Yamamoto ◽  
Daiki Kashiwai ◽  
Pedram Azari ◽  
Ying Ying Khaw ◽  
...  
Keyword(s):  
Polyvinyl Alcohol ◽  
Polyvinyl Alcohol Fiber ◽  
Electrospinning Method ◽  
Formation Behavior

scholarly journals Geotechnical engineering behaviors of gellan gum biopolymer treated sand

2016 ◽  
Vol 53 (10) ◽  
pp. 1658-1670 ◽  
Author(s):  
Ilhan Chang ◽  
Jooyoung Im ◽  
Gye-Chun Cho
Keyword(s):  
Geotechnical Engineering ◽  
Friction Angle ◽  
Soil Improvement ◽  
Gellan Gum ◽  
Strengthening Effect ◽  
Calcite Precipitation ◽  
Unconfined Compression Test ◽  
Sand Particles ◽  
Engineering Practices ◽  
Moisture Conditions

Biological approaches have recently been explored as environmentally friendly alternatives to engineered soil methods in geotechnical engineering practices. The use of microbial induced calcite precipitation, reactive enzymes, and microbial polymers, such as biopolymers, in soil improvement has been studied by researchers around the world. In the present study, gellan gum, a microbial polysaccharide generally used in the food industry due to its hydrogel rheology, was used to strengthen sand. The effects of gellan gum on the geotechnical behaviors of cohesionless sand were evaluated through a series of experimental programs including an unconfined compression test, direct shear test, falling head permeability test, and scanning electron microscopy. The geotechnical properties (friction angle, cohesion, and unconfined compressive strength) of gellan gum–treated sands were determined based on varying moisture conditions: initial, dried, and re-submerged. Gellan gum has a distinct strengthening effect on cohesionless sands through artificial cohesion that varies with the moisture conditions. The strengthening effect of gellan gum on sand appears to be a result of the combination of enhanced bonding between unreactive sand particles and the agglomeration of sand particles through hydrogel condensation, in which the agglomerated sand particles behave as enlarged aggregates in soil.

scholarly journals Experimental Study of Stress-Seepage Coupling Properties of Sandstone under Different Loading Paths

Geofluids ◽  
2021 ◽  
Vol 2021 ◽  
pp. 1-21
Author(s):  
Xi Chen ◽  
Wei Wang ◽  
Yajun Cao ◽  
Qizhi Zhu ◽  
Weiya Xu ◽  
...  
Keyword(s):  
Elastic Modulus ◽  
Pore Pressure ◽  
Complex Loading ◽  
Friction Angle ◽  
Confining Pressure ◽  
Triaxial Tests ◽  
Compression Tests ◽  
Biot Coefficient ◽  
Cyclic Loading And Unloading ◽  
Loading And Unloading

The study on hydromechanical coupling properties of rocks is of great importance for rock engineering. It is closely related to the stability analysis of structures in rocks under seepage condition. In this study, a series of conventional triaxial tests under drained condition and hydrostatic compression tests under drained or undrained condition on sandstones were conducted. Moreover, complex cyclic loading and unloading tests were also carried out. Based on the experimental results, the following conclusions were obtained. For conventional triaxial tests, the elastic modulus, peak strength, crack initiation stress, and expansion stress increase with increased confining pressure. Pore pressure weakened the effect of the confining pressure under drained condition, which led to a decline in rock mechanical properties. It appeared that cohesion was more sensitive to pore pressure than to the internal friction angle. For complex loading and unloading cyclic tests, in deviatoric stress loading and unloading cycles, elastic modulus increased obviously in first loading stage and increased slowly in next stages. In confining pressure loading and unloading cycles, the Biot coefficient decreased first and then increased, which indicates that damage has a great impact on the Biot coefficient.

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