scholarly journals Study on collapsibility of typical structural loess by multi-parameter comparative analysis

2021 ◽  
Vol 293 ◽  
pp. 01032
Author(s):  
Liu Hongcheng ◽  
Lu Changwei ◽  
Wang Yinxia ◽  
Song Yi ◽  
Guan Xiangfeng ◽  
...  
Keyword(s):  
Particle Size ◽  
Comparative Analysis ◽  
Moisture Content ◽  
Composite Structure ◽  
Structural Parameters ◽  
Initial Moisture Content ◽  
Clay Content ◽  
Dry Density ◽  
Particle Content ◽  
Multiple Groups

To study the collapsibility of typical loess and its influencing factors in different areas, the samples in Jingyang, Lanzhou and Yili were studied. The correlation between initial moisture content, dry density, composition of particle size, structural parameters and the coefficient of subsidence is analyzed. The results show that: the coefficient of collapsibility is negatively correlated with the initial moisture content and dry density. In the experiments of multiple groups, the collapsibility coefficient has a certain correlation with the clay content, but not a uniform correlation with the particle content. The collapse coefficient is approximately positively correlated with the composite structure potential.

scholarly journals Lovastatin Production byAspergillus terreusUsing Agro-Biomass as Substrate in Solid State Fermentation

2012 ◽  
Vol 2012 ◽  
pp. 1-11 ◽  
Author(s):  
Mohammad Faseleh Jahromi ◽  
Juan Boo Liang ◽  
Yin Wan Ho ◽  
Rosfarizan Mohamad ◽  
Yong Meng Goh ◽  
...  
Keyword(s):  
Particle Size ◽  
Solid State ◽  
Moisture Content ◽  
Nitrogen Source ◽  
Solid State Fermentation ◽  
Incubation Temperature ◽  
Initial Moisture Content ◽  
Fermentation Time ◽  
Maximum Production ◽  
Additional Nitrogen

Ability of two strains ofAspergillus terreus(ATCC 74135 and ATCC 20542) for production of lovastatin in solid state fermentation (SSF) using rice straw (RS) and oil palm frond (OPF) was investigated. Results showed that RS is a better substrate for production of lovastatin in SSF. Maximum production of lovastatin has been obtained usingA. terreusATCC 74135 and RS as substrate without additional nitrogen source (157.07 mg/kg dry matter (DM)). Although additional nitrogen source has no benefit effect on enhancing the lovastatin production using RS substrate, it improved the lovastatin production using OPF with maximum production of 70.17 and 63.76 mg/kg DM forA. terreusATCC 20542 andA. terreusATCC 74135, respectively (soybean meal as nitrogen source). Incubation temperature, moisture content, and particle size had shown significant effect on lovastatin production (P<0.01) and inoculums size and pH had no significant effect on lovastatin production (P>0.05). Results also have shown that pH 6, 25°C incubation temperature, 1.4 to 2 mm particle size, 50% initial moisture content, and 8 days fermentation time are the best conditions for lovastatin production in SSF. Maximum production of lovastatin using optimized condition was 175.85 and 260.85 mg/kg DM forA. terreusATCC 20542 and ATCC 74135, respectively, using RS as substrate.

scholarly journals Experimental Study on the Effect of Freezing and Thawing on the Shear Strength of the Frozen Soil in Qinghai-Tibet Railway Embankment

2022 ◽  
Vol 2022 ◽  
pp. 1-12
Author(s):  
B. Wang ◽  
J. H. Gao ◽  
Y. Q. Wang ◽  
X. J. Quan ◽  
Y. W. Gong ◽  
...  
Keyword(s):  
Growth Rate ◽  
Internal Friction ◽  
Moisture Content ◽  
Initial Moisture Content ◽  
Friction Angle ◽  
Frozen Soil ◽  
Internal Friction Angle ◽  
Freezing Process ◽  
Dry Density ◽  
Freezing And Thawing

The direct shear tests of different dry density and moisture content samples at different temperatures of the frozen soil in the Qinghai-Tibet Railway embankment between Tanggula South and Anduo section were carried out to analyze the influence rules of each experimental factor on the mechanical properties of frozen soil during the freeze-thaw process. The results show the following. (1) When the frozen soil temperature is below 0°C and continues to drop during the freezing and thawing process, each sample shows the law of a significant increase in cohesion and a slight decrease in the internal friction angle. In the meantime, the cohesion obtained during the thawing process of the sample at the same temperature point is higher than that obtained during the freezing process. In contrast, the internal friction angles exhibit an opposite law, where the internal friction angle during the melting process is lower than the internal friction angle during the freezing process. After freezing-thawing action, it deserves to be mentioned that the cohesion increases slightly while the internal friction angles present a slight decrease trend compared to the initial state. (2) With the decrease in temperature and the gradual increase in cohesion, the temperature curve can be divided into a fast-growing section from 0 to −2°C, a slow-growing section from −2 to −8°C, and a second fast-growing section from −8 to −10°C owing to the combined effect of the pressure-thawing action and ice-water phase change. In addition, the rate of decrease in the internal friction angle also shows a similar pattern. (3) The cohesion and the internal friction angle of samples both tend to increase first and then decrease with the rise of the initial moisture content, and the critical initial moisture content is near the optimal moisture content of 15%. (4) Both the cohesion and the internal friction angle of the samples increase with dry density growth. The growth rate of cohesion will gradually increase as the temperature decreases. Moreover, the growth rate of cohesion of low dry density samples is more susceptible to temperature, while the internal friction angle growth rate is not affected by temperature.

scholarly journals Influence of Freeze-Thaw Cycles on Mechanical Response of Levee Pavement

2021 ◽  
Vol 2021 ◽  
pp. 1-10
Author(s):  
Shuan Guo ◽  
Zheng Lu ◽  
Guokun Liu ◽  
Baoli Zhuang ◽  
Yongfeng Fan ◽  
...  
Keyword(s):  
Moisture Content ◽  
Mechanical Response ◽  
Triaxial Compression ◽  
Initial Moisture Content ◽  
Dry Density ◽  
Test Results ◽  
Freeze Thaw ◽  
Temperature Range ◽  
Pavement Structure ◽  
The Stability

The freeze-thaw cycles cause deterioration in mechanical properties of levee soil and further endanger the pavement structure on the embankment. This study attempts to comprehensively understand the mechanical response of pavement after freeze-thaw cycles. In this paper, the freeze-thaw cycles test under an open system was carried out, and then the triaxial compression test was conducted. Based on the test results, the effects of freeze-thaw cycles, temperature range, initial dry density, and initial moisture content of embankment soil on the mechanical response of road structure after freeze-thaw were calculated and analyzed. Finally, the stability of the slope of the levee was evaluated. The results show that the number of freeze-thaw cycles has the most significant impact on the mechanical response of pavement, the stress and strain of the structural layers vary in different ranges, and the pavement deflection increases by 5 times after 7 freeze-thaw cycles. However, the initial dry density and initial moisture content of the soil have little influence on the pavement structure, and the temperature range will exert an influence when it exceeds a certain threshold.

Test Research on Engineering Property of Expansive Rocks of Anyang Test Zone in Middle Route of South-North Water Transfer Project

2013 ◽  
Vol 321-324 ◽  
pp. 239-244
Author(s):  
Zhuang Cheng ◽  
Le Hua Wang ◽  
Yan Hua Dong ◽  
Xiao Ling Liu
Keyword(s):  
Moisture Content ◽  
Linear Correlation ◽  
Initial Moisture Content ◽  
Water Transfer ◽  
Dry Density ◽  
Rock Samples ◽  
Test Zone ◽  
Mineral Components ◽  
North Water ◽  
Different Depths

Test samples are selected in different depths of Pile No.1370 at Anyang test zone in Middle Route of South-North water transfer project. Through a series of experiment, the physical properties, mineral components and properties of mechanics, permeability and swelling-shrinking of expansive rock are well studied. The results show that hydrophilic mineral component of the expansive rock in different depths differ remarkably. To the same kind of expansive rock samples with the same dry density, cohesion and friction angles are negative linear correlation with moisture content respectively and cohesion is more sensitive to moisture content. With the same initial moisture content, the logarithm of saturated permeability coefficients of expansive rock samples are linear correlation with their dry densities. The initial moisture content has a much larger effect on maximum swelling ratio than shrinkage, thus the process of swelling-shrinking is not reversible. The results can supply scientific references for the South-North water transfer project.

scholarly journals Swelling behaviours of compacted lime-softening sludge for application in landfill liners

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Agnieszka Dąbska ◽  
Agata Léthel
Keyword(s):  
Moisture Content ◽  
Tap Water ◽  
Initial Moisture Content ◽  
Dry Density ◽  
Content Increase ◽  
Swelling Potential ◽  
Landfill Liners ◽  
Lime Softening ◽  
Practical Engineering ◽  
The Impact

AbstractThe objective of this study was to investigate the swelling potential of compacted lime-softening sludge for application in landfill liners. The study involved the assessment of the effect of compaction and moulding moisture content (30–40%), corresponding to the Proctor standard compaction test. One-dimensional oedometer swell tests were conducted using distilled water, tap water, and municipal landfill leachate, resulting in the determination of the expansion indices. Moreover, changes in the moisture content and dry density during the swelling process were investigated. The expansion index was significantly influenced by the initial moisture content and liquid chemistry. Subsequently, these factors also affected the sludge dry density decrease, and its moisture content increase, whereas the impact of the initial dry density on expansion was of low importance. An increase in the sludge moulding moisture content, limited swelling in all liquids used. The highest expansion, dry density, and moisture content changes due to swelling were identified for leachate at w < wopt. It should be underlined that the effect of liquid on the swelling potential faded away along with a further increase in the moisture content w > wopt. The novelty of the work lies in identifying a significant plunge of the expansion index at w ≈ wopt for the leachate swelling test. The lime-softening sludge non-swelling moisture content was defined as wnon ≈ (wopt + 4.0%) − (wopt + 4.5%). For practical engineering implications, the moisture content between (wopt + 2.0%) and (wopt + 4.0%) was provided for the most suitable sludge application in landfill liners.

scholarly journals Characterization of the High Swelling Green Clay in the Vicinity of Amman Area

2021 ◽  
Vol 15 (1) ◽  
pp. 360-369
Author(s):  
Monther Abdel Hadi ◽  
Ibrahim Khliefat ◽  
Nafeth Abdelhadi ◽  
Nidhal Saada
Keyword(s):  
Moisture Content ◽  
Clay Mineral ◽  
Initial Moisture Content ◽  
Swelling Pressure ◽  
Liquid Limit ◽  
Engineering Properties ◽  
Dry Density ◽  
Initial Water Content ◽  
Foundation Design ◽  
Green Clay

Introduction: Jordan is awarded huge areas in the north and western part of the country in which brown and green clay is dominant. This research focuses on the problems and behaviour of the green clay only. The main problem of the green clay is its high swelling pressure which is the main cause of excessive settlement and wall cracks in buildings, especially during the wet season. Methods: This study aims to investigate the engineering properties and behaviour of the green clay deposits in the Amman area, which will serve as a guide for both geotechnical and structural engineers when preparing the foundation design. Results: Based on the consolidation test, the investigated green clay showed high swelling pressure of 3.11 kg/cm2, liquid limit (LL) of 73%, plasticity index (PI) of 40%, the shrinkage limit (SL) of 12%, and liquidity index (LI) of 0.125. The moisture content at saturation is 35.14%, while the natural moisture content is 28%, dry density is 1407 kg/m3, cohesion (C) is 0.20 kg/cm2 and unconfined compressive strength is 1.05 kg/cm2. The XRD results of the clay size fraction have confirmed the presence of the expansive clay mineral smectite as the essential clay mineral together with kaolinite. Results provide a general understanding of the behaviour and properties of the green clay, and the regression analysis showed good correlations between the liquid limit and initial moisture content with the compression index and also between the initial void ratios with the swelling index. Conclusion: Changes in the volume are due to the unsaturation level of clay when provided with initial water content.

scholarly journals Experimental Research on Frost Heave Characteristics of Gravel Soil and Multifactor Regression Prediction

2018 ◽  
Vol 2018 ◽  
pp. 1-13 ◽  
Author(s):  
Xiaoyong Long ◽  
Guoping Cen ◽  
Liangcai Cai ◽  
Yue Chen
Keyword(s):  
Moisture Content ◽  
Initial Moisture Content ◽  
Clay Content ◽  
Open Water ◽  
Frost Heave ◽  
Frost Heaving ◽  
Gravel Soil ◽  
Closed Water ◽  
Multifactor Regression ◽  
Insight Into

Gravel soil is usually considered to be insensitive to frost heave. However, many frost heave deformations of foundation in seasonal frozen region indicate that gravel soil may also produce frost heave under certain special conditions. In order to gain a deep insight into the frost heave characteristics of gravel soil, a series of laboratory experiments on one-dimensional frost heave were conducted under the open- and closed-water replenishing condition using an improved experiment apparatus. The influence of various factors including initial moisture content, clay content, compactness, overlying load, and water replenishing on frost-heaving ratio of gravel soil were analyzed. And the basic frost heave characteristics including frost heave amount, frost heave speed, frozen depth, freezing speed, and moisture content distribution after freezing in a gravel soil sample were analyzed. The corresponding mechanisms were also discussed. Results showed that in the open water replenishing condition, there exists a linear relationship between initial moisture content, overlying load, and frost-heaving ratio and a quadratic polynomial relationship between clay content, compactness, and frost-heaving ratio. Frost-heaving ratio in the open water replenishing condition can be found to increase over three times than that under the closed water replenishing condition. Multifactor regression empirical formula was obtained by multiple regression analysis to predict the frost-heaving ratio of gravel soil under certain collocation of factors and levels under the closed water replenishing condition. The significant effects on frost-heaving ratio were, in order, water replenishing > initial moisture content > clay content > compactness > overlying load.

scholarly journals Experimental Study on Moisture Migration of Unsaturated Loess during the Freezing Process

2020 ◽  
Vol 2020 ◽  
pp. 1-11
Author(s):  
Hui Zhang ◽  
Tiehang Wang ◽  
Enlong Liu ◽  
Mengling Hu
Keyword(s):  
Moisture Content ◽  
Initial Moisture Content ◽  
Freezing Process ◽  
Dry Density ◽  
Freezing Front ◽  
Slow Cooling ◽  
Moisture Migration ◽  
Cooling Stage ◽  
Large Size ◽  
Unsaturated Loess

To reveal the water-heat transfer mechanism of unsaturated loess, the effects of soil dry density (1.30 g/cm3, 1.50 g/cm3, and 1.65 g/cm3), moisture content (13.3%, 16.2%, and 19.4%), cold end temperature (−7°C, −10°C, and −13°C), and freezing mode on moisture migration in unsaturated loess in this paper are studied through indoor tests of moisture migration under the freezing action of large-size unsaturated loess. The results show that the temperature change in soil samples in the freezing process can be divided into three stages: rapid cooling stage, slow cooling stage, and stable stage. The higher the dry density, the closer the freezing front is to the cold end, with the initial moisture content having little effect on the freezing front, while the temperature at the cold end has a significant effect on the location of the freezing front. The total amount of moisture migration decreases with the increase of dry density, increases with the increase of moisture content, and increases with the decrease of cold end temperature. The freezing mode directly affects the distribution of moisture content and total amount of moisture migration in the frozen area.

scholarly journals Factors Affecting the Swelling-Compression Characteristics of Clays in Yichang, China

2019 ◽  
Vol 2019 ◽  
pp. 1-13
Author(s):  
Changxi Huang ◽  
Xinghua Wang ◽  
Hao Zhou ◽  
Yan Liang
Keyword(s):  
Moisture Content ◽  
Initial Moisture Content ◽  
Expansive Soil ◽  
Swelling Pressure ◽  
Stress Path ◽  
Dry Density ◽  
Initial Water Content ◽  
Initial Water ◽  
Swelling Properties ◽  
Vertical Loading

Expansive soil has been studied for eighty decades because it is prone to cause geotechnical engineering accidents. The results of the moisture content effects on the expansive pressure were not consistent in the literatures. In this paper, swelling deformation and pressure tests were conducted to clarify the effects of the initial water content on the swelling properties. The relation of expansive stress and initial moisture content was accurately described with a Gaussian distribution, unlike in the previously published studies. These results could be explained by the change in the microstructure with diverse moisture contents. In addition, dry density and vertical stress influences on expansive properties were analysed. With an increase in the vertical loading, the soil samples first expanded, and then the samples with a lower dry density collapsed; however, the samples with a higher dry density did not collapse, even under a considerable vertical loading. Furthermore, the relation between stress path and expansive pressure was examined. It was observed that the swelling pressures obtained from the constant volume tests were greater than the results from the swell under load tests. The relationship between the swelling pressure and swelling strain was also analysed.

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