Electrokinetic strengthening of a marine sediment using intermittent current

2001 ◽  
Vol 38 (2) ◽  
pp. 287-302 ◽  
Author(s):  
S Micic ◽  
J Q Shang ◽  
K Y Lo ◽  
Y N Lee ◽  
S W Lee
Keyword(s):  
Shear Strength ◽  
Water Content ◽  
Marine Sediment ◽  
Land Reclamation ◽  
Soil Improvement ◽  
Offshore Structures ◽  
Experimental Program ◽  
Electrokinetic Treatment ◽  
Surcharge Preloading ◽  
Potential Applications

An experimental program on electrokinetic strengthening of a marine sediment using intermittent current was conducted on a high-salinity marine clay recovered from a land reclamation site on the Korean coast. The study focused on the use of electrokinetics to enhance the effect of surcharge preloading consolidation to improve mechanical and physical properties of soil. This paper presents the design, execution, and results of the electrokinetic tests performed in a custom-designed electrokinetic cell. The test results demonstrate that electrokinetic treatment combined with preloading consolidation is an effective method of increasing the shear strength and decreasing the water content of the marine sediment beyond that achievable by preloading consolidation alone. For the same consolidation pressure over the identical time period, the increase in the average undrained shear strength of the marine sediment after electrokinetic treatment combined with preloading consolidation was up to 145% greater than that achieved by the preloading consolidation alone. A corresponding decrease in the soil water content of approximately 125% was measured. The power consumption and electrode corrosion are reduced by using intermittent current. The process developed in this research has potential applications in strengthening soft clayey soils at and around foundations of new onshore and offshore structures embedded in marine sediments and for rehabilitation of existing offshore platforms.Key words: marine sediment, electrokinetics, preloading consolidation, soil improvement, soil shear strength, land reclamation.

scholarly journals Improving Shear Strength Parameters of Sandy Soil using Enzyme-Mediated Calcite Precipitation Technique

2018 ◽  
Vol 20 (2) ◽  
pp. 91 ◽  
Author(s):  
Heriansyah Putra ◽  
Hideaki Yasuhara ◽  
Naoki Kinoshita ◽  
Erizal . ◽  
Tri Sudibyo
Keyword(s):  
Shear Strength ◽  
Sandy Soil ◽  
Friction Angle ◽  
Soil Improvement ◽  
Soil Mass ◽  
Shear Strength Parameters ◽  
Calcite Precipitation ◽  
Strength Parameters ◽  
Direct Shear Tests ◽  
Potential Applications

Several methods have been established for their various potential applications as soil improvement technique, and recently the application of grouting technique using biological process have been proposed. This study discussed the applicability of enzyme-mediated calcite precipitation (EMCP) in improving the shear strength parameters of sandy soil.  In this study, soil specimens were prepared and treated with the grouting solutions composed of urea, calcium chloride, magnesium sulfate and enzyme of urease. Evolutions in the cohesion and internal friction angle of the improved soil were examined through the direct shear tests. The presence of the precipitated materials, comprising 4.1 percent of the soil mass of the treated sand, generated a cohesion of 53 kPa. However, contrary to the improvement of cohesion, the friction angle is relatively constant. It indicated that the application of the EMCP technique has no significant impact on the friction angle

scholarly journals Analysis of the suction evolution during direct shear test in a silty sand soil

2020 ◽  
Vol 195 ◽  
pp. 03031
Author(s):  
Omar AL-Emami ◽  
Gabriela M Medero ◽  
Fernando A M Marinho ◽  
Melis Sutman
Keyword(s):  
Shear Strength ◽  
Water Content ◽  
Large Scale ◽  
Matric Suction ◽  
Vertical Stress ◽  
Silty Sand ◽  
Experimental Program ◽  
Direct Shear ◽  
Initial Void Ratio ◽  
Study Results

Shear strength of soils is one of the essential parameters for analysing and solving divers geotechnical problems (e.g. the bearing capacity of shallow footings pile foundations, slope stability and earth embankments). In this study, a series of conventional large-scale (300 X 300 mm) direct shear tests were carried out on saturated and constant water content silty sand specimens at ei = 0.6 and 1.0 tested under applied vertical stresses of 100, 200, or 400 kPa to investigate the influence of matric suction on the shear strength characteristics of the tested material. A loading steel cap was modified to allow the direct measurements of the matric suction using two commercial available Equitensiometer suction probes (EQ3). The experimental program indicated that, for both studied void ratios, the obtained shear strength of specimens under constant water content is found to be distinctly greater than those obtained from saturated samples. The results showed that the samples compacted at ei = 1.0 exhibited collapse behaviour during saturation stage, whereas same samples did not show any volume change during stabilisation stage when tested under constant water content condition. The study results also showed that the matric suction reduction during consolidation stage depends on initial void ratio of the tested samples as well as the level of applied vertical stress. Moreover, the matric suction evolution during shearing process of both studied void ratios specimens decreased with increasing the level of applied vertical stress.

Electrical strengthening of clays by dielectrophoresis

1994 ◽  
Vol 31 (2) ◽  
pp. 192-203 ◽  
Author(s):  
K.Y. Lo ◽  
J.Q. Shang ◽  
I.I. Inculet
Keyword(s):  
Shear Strength ◽  
Electric Field ◽  
Soil Improvement ◽  
Nonuniform Electric Field ◽  
Experimental Program ◽  
Effective Polarizability ◽  
Clay Particles ◽  
Shearing Resistance ◽  
Preconsolidation Pressure ◽  
Sensitive Clay

The theory of dielectrophoresis in clay–water–electrolyte systems is developed in this paper. Dielectrophoresis is the motion of particles generated by a nonuniform electric field. The dielectrophoretic forces on clay particles are determined by the effective polarizability and configuration of the nonuniform electric field. In most clay–water–electrolyte systems, including natural clays, the dielectrophoretic forces are directed towards the lower field intensity, determined by the negative polarizability. In the experimental program, an ac voltage of 60 Hz and 15 kV was applied through insulated electrodes on block samples of Leda clay for 28 days. The relationship between the soil undrained shear strength after treatment and the distribution of electric field provides direct experimental support for the theory developed. Under three electrical-field configurations, the overall shear strengths increased up to 44.0%, concurrent with significant reduction of sensitivity. The improvement of soil properties was also reflected as increases of preconsolidation pressure and shearing resistance in terms of effective stresses. The electrochemical reactions associated with electric current were minimized by insulation to the electrodes. Key words : dielectrophoresis, electrokinetics, soil improvement, sensitive clay, shear strength.

Model Test of Using Vacuum Preloading to Improve Dredge

2011 ◽  
Vol 374-377 ◽  
pp. 1908-1911
Author(s):  
Shu Wang Yan ◽  
Qun Hua Zhou ◽  
Li Qiang Sun
Keyword(s):  
Water Content ◽  
Model Test ◽  
Land Reclamation ◽  
Ground Surface ◽  
Soil Improvement ◽  
Field Investigation ◽  
Vacuum Preloading ◽  
Undrained Strength ◽  
Soil Foundation

Dredge materials with the water content more than 80% have been used for land reclamation in Tianjin, China. The dredge is transferred by pipeline to the reclamation place and then strengthened with the vacuum preloading technique. It has been found that with the thickness of the filled dredge layer becomes larger and larger, the quality of soil improvement is not as good as expected. Field investigation shows that after vacuum preloading the vane test strength can reach 50kPa at the ground surface, but decreases along with depth dramatically. The model test is carried out to detect the factors that may influence the efficiency of using vacuum preloading to improve dredge soil foundation. The water content, vacuum pressure and undrained strength are measured during the test.

Effects of Electro Osmotic Consolidation in South West of Johor: Small Laboratory Scale

2014 ◽  
Vol 803 ◽  
pp. 255-264
Author(s):  
Khairul Nizar Mohd Yusof ◽  
Fauziah Ahmad ◽  
Mohd Mustafa Al Bakri Abdullah ◽  
Muhammad Faheem Mohd Tahir
Keyword(s):  
Shear Strength ◽  
Water Content ◽  
Clay Soil ◽  
Soft Clay ◽  
Soil Improvement ◽  
Undrained Shear Strength ◽  
Engineering Structures ◽  
Vertical Loading ◽  
South West ◽  
Undrained Shear

Clay soil is one of the problematic soils due to its natural states which have low bearing capacity and high compressibility. The effect and problem of the clay soil characteristic creates a problem for construction especially excessive settlement and this can lead to unstable and potential cracks of engineering structures. At presents, there are few of soil improvement types can be carried out to overcome these problems, and electro osmotic consolidation is one of the options. This method has been applied many years ago especially in european countries. The study encompasses the determination of water content, atterberg’s limits and undrained shear strength after electro osmotic consolidation treatment of clay soils taken from 0.5 m and 1.5 m at southwest part of johor. All the samples were tested according to BS1377:1990. An experimental study was implemented in a pvc cylinder tube having dimensions of 300 mm height and 100 mm diameter. In the results of electro osmotic consolidation tests by installing copper spring electrodes, the measured undrained shear strength was increased considerably at the anodes especially compared to the initial undrained shear strength due to electro osmosis process and consolidation. As laboratory studies of its measurement have shown, the application of electro osmotic consolidation after the application of a direct current applied voltage of 10 volts, at the anodes especially: (i) a decrease by approximately 35% in water content; (ii) an increase around 29% in undrained shear strength; and (iii) a decrease about 21% in index plasticity. The results obtained in this study shows that the electro osmotic enhanced 15 kpa vertical loading consolidation is a feasible approach in strengthening of south west soft clay in johor. It can be clearly suggested that the higher the voltage applied in the system, the higher readings of undrained shear strength and the lower of water content especially at the anodes.

scholarly journals Dredged Soil Improvement by Electro Osmosis

2019 ◽  
Vol 8 (3) ◽  
pp. 6992-6995
Keyword(s):  
Shear Strength ◽  
Water Content ◽  
Electrode Material ◽  
Electrode Materials ◽  
Soil Improvement ◽  
Operational Conditions ◽  
Maximum Reduction ◽  
Dredged Soil ◽  
Electro Osmosis

Water content and Strength of Dredged Soil (DS) obtained from Aliyar reservoir were measured after dewatering using Electro Osmosis (EO). The operational conditions adopted include electrode material (Cu, Fe, Al), voltage (6V, 12V, 24V) and duration (24 hours, 48 hours and 72 hours). 27 combinations of experiments were piloted to explore the influence of operational conditions on water content and strength in shear. Maximum reduction in water content was obtained in Fe electrode with 24V and 72 hours of duration for which the water content falls to 27.22% from 87% and the corresponding shear strength is 27.30 kPa. Further, the loss of electrode materials during EO process was also measured.

scholarly journals Optimising the DPPH Assay for Cell-Free Marine Microorganism Supernatants

Marine Drugs ◽  
2021 ◽  
Vol 19 (5) ◽  
pp. 256
Author(s):  
Yehui Gang ◽  
Tae-Yang Eom ◽  
Svini Dileepa Marasinghe ◽  
Youngdeuk Lee ◽  
Eunyoung Jo ◽  
...  
Keyword(s):  
Water Content ◽  
Antioxidant Activities ◽  
Fermented Foods ◽  
Solution Stability ◽  
Marine Microorganism ◽  
Marine Microorganisms ◽  
Dpph Assay ◽  
Aqueous Methanol ◽  
Potential Applications ◽  
Pseudoalteromonas Rubra

Antioxidants prevent ageing and are usually quantified and screened using the 1,1-diphenyl-2-picrylhydrazyl (DPPH) assay. However, this assay cannot be used for salt-containing samples, such as the cell-free supernatants of marine microorganisms that are aggregated under these conditions. Herein, the DPPH solvent (methanol or ethanol) and its water content were optimized to enable the analysis of salt-containing samples, aggregation was observed for alcohol contents of >70%. The water content of methanol influenced the activities of standard antioxidants but did not significantly affect that of the samples. Based on solution stability considerations, 70% aqueous methanol was chosen as the optimal DPPH solvent. The developed method was successfully applied to the cell-free supernatants of marine bacteria (Pseudoalteromonas rubra and Pseudoalteromonas xiamenensis), revealing their high antioxidant activities. Furthermore, it was concluded that this method would be useful for the screening of marine microorganism–derived antioxidants, which also has numerous potential applications, such as salt-fermented foods.

scholarly journals Impact of Reinforcement Ratio on Shear Behavior of I-Shaped UHPC Beams with and without Fiber Shear Reinforcement

Materials ◽  
2020 ◽  
Vol 13 (7) ◽  
pp. 1525 ◽  
Author(s):  
Altug Yavas ◽  
Cumali Ogun Goker
Keyword(s):  
Shear Strength ◽  
Failure Mode ◽  
High Performance Concrete ◽  
Shear Behavior ◽  
Reinforcement Ratio ◽  
Steel Fibers ◽  
Experimental Program ◽  
Shear Reinforcement ◽  
Ultimate Shear Strength ◽  
Loading Test

In the presented paper, the impacts of steel fiber use and tensile reinforcement ratio on shear behavior of Ultra-High Performance Concrete (UHPC) beams were investigated from the point of different tensile reinforcement ratios. In the scope of the experimental program, a total of eight beams consisting of four reinforcement ratios representing low to high ratios ranged from 0.8% to 2.2% were casted without shear reinforcement and subjected to the four-point loading test. While half of the test beams included 30 mm end-hooked steel fibers (SF-UHPC) with 2.0 vol%, the remaining beams were produced without the fiber to show possible effectiveness of the fiber use. The shear performances were discussed in terms of the load—deflection response, cracking pattern and failure mode, first cracking load and ultimate shear strength. In this sense, all the non-fiber beams were failed by shear with a dramatic load drop, regardless of the tensile reinforcement amount, before the yielding of reinforcement and they produced no deflection capability. The test results showed that while the inclusion of steel fibers to the UHPC mixture with low reinforcement ratios changed the failure mode from the shear to flexure, it significantly enhanced the ultimate shear strength in the case of higher reinforcement ratio through the SF-UHPC’ superior mechanical properties and fibers’ crack-bridging ability.

Characterization of Shear Strength and Interface Friction of Organic Soil

2020 ◽  
Vol 857 ◽  
pp. 203-211
Author(s):  
Majid Hamed ◽  
Waleed S. Sidik ◽  
Hanifi Canakci ◽  
Fatih Celik ◽  
Romel N. Georgees
Keyword(s):  
Shear Stress ◽  
Shear Strength ◽  
Internal Friction ◽  
Moisture Content ◽  
Water Content ◽  
Friction Angle ◽  
Structural Materials ◽  
Organic Soil ◽  
Internal Friction Angle ◽  
Interface Friction

This study was undertaken to investigate some specific problems that limit a safe design and construction of structures on problematic soils. An experimental study was carried out to examine the influence of loading rate and moisture content on shear strength of organic soil. Influece of moisture content on interface friction between organic soil and structural materials was also attempted. A commonly used soil in Iraq was prepared at varying moisture contents of 39%, 57% and 75%. The experimental results showed that the increase in water content will decrease the shear stress and the internal friction angle. An increase of the shearing rate was found to decrease the shear stress and internal friction angle for all percetanges of water contents. Further, direct shear tests were carried out to detect the interface shear stress behavior between organic soil and structural materials. The results revealed that the increase in water content was shown to have significant negetavie effects on the interface internal friction and angle shear strength.

Sign in / Sign up

Export Citation Format

Share Document