The plastic limit of silty, surface soils in relation to their content of polysaccharide gel

Soil Research ◽  
1995 ◽  
Vol 33 (1) ◽  
pp. 1 ◽  
Author(s):  
WW Emerson
Keyword(s):  
Plastic Limit ◽  
Coarse Silt ◽  
Surface Soils ◽  
Fine Silt ◽  
The Matrix ◽  
Clay Matrix ◽  
Matrix Suction ◽  
Constant Percentage

By using values reported in the literature, the plastic limits of mainly silty surface soils have been found to increase by 6-7 g H2O per g of C present. To explain this, it is suggested that at the plastic limit, particles of coarse silt are being rolled over each other with compacted portions of fine silt/clay matrix in between. The plastic limit is increased because of water sorbed by bonding polysaccharide gels in additional 1-3 �m sized pores between the compacted portions. The presence of such pores should have little effect on the matrix suction since this is determined by the size of the largest water-filled pores present. Water sorbed will then be proportional to C content as found, provided the composition of the polysaccharides present is constant and polysaccharide C forms a constant percentage of total C. This allows changes in the plastic limit of a soil to be used to indicate relative amounts of gel present. For example, several years after cropping was changed from grass to arable, more gel was present than in the same soils under continuous arable. Mild peroxidation of one soil did not alter the proportion of the total C present in gel form.

The Research of Slope Stability Based on Unsaturated Soil Theory

2014 ◽  
Vol 937 ◽  
pp. 590-593
Author(s):  
Chang Qing Shao ◽  
Nan Zhang ◽  
Feng Lan Lv
Keyword(s):  
Unsaturated Soil ◽  
Evaluation Methods ◽  
Rainfall Infiltration ◽  
Stability Factor ◽  
Analysis Method ◽  
Infiltration Process ◽  
Strong Activity ◽  
The Matrix ◽  
Matrix Suction ◽  
The Stability

With the deep landslide induced by rainfall or more in practice, the existing evaluation methods are not suitable for to explain this kind of landslide during rainfall, which is the phenomenon of strong activity. This paper tries to improve existing methods for analyzing the stability of the landslide, the article set up to consider soil stability analysis method of the matrix suction side article discusses rainfall infiltration process middle side matrix suction changes impacting on the stability of the landslide, the preliminary discussion on the effect of rainfall on deep landslide are studied. Considering soil of the side of the evaluation methods of matrix suction jettisoned traditional saturated unsaturated soil mechanics analysis method, it can well reflect the process of rainfall infiltration, the matrix suction decreases, and the inter-atomic forces, stability factor to reduce the process, providing a train of thought for landslides evaluation.

Second Canadian Geotechnical Colloquium: Appropriate concepts and technology for unsaturated soils

1979 ◽  
Vol 16 (1) ◽  
pp. 121-139 ◽  
Author(s):  
D. G. Fredlund
Keyword(s):  
Unsaturated Soil ◽  
Unsaturated Soils ◽  
Pore Water Pressure ◽  
Water Pressure ◽  
Three Dimensional ◽  
Earth Pressure ◽  
Saturated Soil ◽  
Engineering Practice ◽  
The Matrix ◽  
Matrix Suction

A practical science has not been fully developed for unsaturated soils for two main reasons. First, there has been the lack of an appropriate science with a theoretical base. Second, there has been the lack of an appropriate technology to render engineering practice financially viable.This paper presents concepts that can be used to develop an appropriate engineering practice for unsaturated soils. The nature of an unsaturated soil is first described along with the accompanying stress conditions. The basic equations related to mechanical properties are then proposed. These are applied to practical problems such as earth pressure, limiting equilibrium, and volume change.An attempt is made to demonstrate the manner in which saturated soil mechanics must be extended when a soil is unsaturated. Two variables are required to describe the stress state of an unsaturated soil (e.g., (σ – ua) and (ua – uW). There is a smooth transition from the unsaturated case to the saturated case since the pore-air pressure becomes equal to the pore-water pressure as the degree of saturation approaches 100%. Therefore, the matrix suction (i.e., (ua – uW) goes to 0 and the pore-water pressure can be substituted for the pore-air pressure (i.e., (σ – uW)).The complete volumetric deformation of an unsaturated soil requires two three-dimensional constitutive surfaces. These converge to one two-dimensional relationship for a saturated soil. The shear strength for an unsaturated soil is a three-dimensional surface that reduces to the conventional Mohr–Coulomb envelope for a saturated soil.The manner of applying the volumetric deformation equations and the shear strength equation to practical problems is demonstrated. For earth pressure and limiting equilibrium problems, the unsaturated soil can be viewed as a saturated soil with an increased cohesion. The increase in cohesion is proportional to the matrix suction of the soil. For volume change problems it is necessary to have an indication of the relationship between the various soil moduli.There is a need for further experimental studies and case histories to substantiate the proposed concepts and theories.

scholarly journals Dust Particle Size and Statistical Parameters

2021 ◽  
pp. 57-93
Author(s):  
Noor Al-Dousari ◽  
Modi Ahmed ◽  
Ali Al-Dousari ◽  
Musaad Al-Daihani ◽  
Murahib Al-Elaj
Keyword(s):  
Particle Size ◽  
Grain Size ◽  
Size Distribution ◽  
Fine Sand ◽  
Coarse Sand ◽  
Optical Methods ◽  
Size Analysis ◽  
Coarse Silt ◽  
Statistical Parameters ◽  
Fine Silt

AbstractGrain ‘size’ can be specified and measured in several different ways. All methods of grain size determination have blemishes, and the choice of the most appropriate method is governed by the nature of the sample and the use to which the data are placed. Four main methods are currently used for size analysis of sands: (a) sieving; (b) settling tube analysis; (c) electro-optical methods, including Coulter Counter analysis and laser granulometry; and (d) computerized image analysis. The classification of the particle size distribution of Kuwait dust was mapped according to the parameters proposed by Folk And Ward (1957) which were widely used for quantitative comparisons between natural grain size distribution and the lognormal distribution that shows better sorted sediments have lower values of σ1. Maps of the distribution of dust in Kuwait were obtained that included: fine sand (F.S.), Coarse sand (C.S), Medium Sand (M.S), Very Fine Sane (V.F.S), Very Coarse Silt (V.C.Silt), Coarse Silt (C.Silt), Medium Silt (M.Silt), Fine Silt (F.Silt), Very Fine Silt (V.F.Silt), in addition to that, the deposition percentage of Clay, Sand, mud (silt plus clay) and silt were provided.

Influence of Matric Suction on Shear Strength Behavior of Unsaturated Silty Sand

2012 ◽  
Vol 446-449 ◽  
pp. 1627-1632
Author(s):  
Qian Dong ◽  
Liu Liu ◽  
Long Hou
Keyword(s):  
Shear Strength ◽  
Water Content ◽  
Peak Effect ◽  
Silty Sand ◽  
Direct Shear Tests ◽  
Suction Control ◽  
Two Factors ◽  
The Matrix ◽  
Matrix Suction ◽  
The Relationship

In order to research matrix suction how to influence the shear strengt of unsaturated silty sand. Based on the analysis of the Soil-water characteristic of unsaturated silty sand through pressure plate instrument test,the suction control direct shear tests under the different suction condition of unsaturated silty sand are studied. And then, the microscopic structure of two kinds soil sample with different water content are scanned to analyze the relationship between the matrix suction and the shear strengt of unsaturated silty sand. The results of the research show that unsaturated silty sand different from unsaturated clayey soil.When water content gradually reduce, the soil shear strength of unsaturated silty sand is not always increased with the increase of matrix suction, but there is a "peak effect".The appearance of "peak effect" is due to unsaturated silty sand has own microstructure characteristics.On the other hand, when the moisture content reduction constantly,the existence form of moisture change gradually.The two factors lead to the effect area of matrix suction change constantly,and then influence shear strengt of unsaturated silty sand to appear "peak effect". In addition,the stress environment also can influence contribution degree of matrix suction to the shear strengt of unsaturated silty sand.

The Recognition of Amorphous Silica in Indurated Soil Profiles

Clay Minerals ◽  
1993 ◽  
Vol 28 (3) ◽  
pp. 461-474 ◽  
Author(s):  
Balbir Singh ◽  
R. J. Gilkes
Keyword(s):  
Amorphous Silica ◽  
Silica Content ◽  
X Ray Diffraction ◽  
X Ray ◽  
Transmission Electron ◽  
The Matrix ◽  
Clay Matrix ◽  
Secondary Silica ◽  
Xrd Techniques

AbstractSilica-indurated subsurface horizons of an in situ lateritic profile in semi-arid western Australia were investigated using a range of electron-optical and X-ray diffraction (XRD) techniques. These indurated materials were compared with underlying non-indurated pallid zone material. The secondary silica content of the indurated horizons, as determined by electron microprobe analysis, varied from 8 to 33%. Quantitative digital images for secondary silica, generated by mathematical manipulation of digital Si and AI-Kα: images, showed that kaolinite pseudomorphs after mica contained the lowest amounts of secondary silica, with the highest amounts being present in the inter-pseudomorph clay matrix. Variations in the amount of silica in the matrix are considered to reflect variations in the initial porosity of the clay matrix. Such variations may arise from differences in the Al/Si ratio of parent minerals. Transmission electron microscopy (TEM) showed that amorphous silica adhered to the (001) face of kaolinite crystals. The secondary silica could not be detected by either standard or differential XRD procedures.

scholarly journals Experimental Study on Response Law and Failure Process of Slopes in Fully Weathered Granites Under Precipitation Infiltration

2021 ◽  
Author(s):  
Fei Tan
Keyword(s):  
Experimental Study ◽  
Physical Simulation ◽  
Pore Water Pressure ◽  
Water Pressure ◽  
Failure Process ◽  
Similarity Criterion ◽  
Weathered Granite ◽  
The Matrix ◽  
Soil Flow ◽  
Matrix Suction

Abstract To investigate the response law and failure process of slopes in fully weathered granites under precipitation infiltration, a typical fully weathered granite slope is selected for sampling in Fengkai, Guangdong. The physical simulation experimental study of rainfall-induced landslide is conducted, in which Weber criterion is used as the similarity criterion for precipitation. The research results reveal that under precipitation infiltration, the fully weathered granite slope responds quickly. Further, the water content increases sharply, and the matrix suction quickly dissipates. After dissipation, the matrix suction transforms into pore water pressure, which accelerates the deformation of the slope. The wet peak has a large infiltration depth in the slope, and the acceleration of deep part is lower than that of the shallow part. Under the action of precipitation, the fully weathered granite model undergoes four stages of failure. Firstly, gullies and cracks appear. Secondly, cracks propagate and link up. Then, the soil on the slope surface swells and ruptures. Finally, the slope slides locally until the entire slope creeps, collapses, and transforms into a "soil flow." Based on the analysis of precipitation similarity, the landslide will be triggered in fully weathered granite slope by precipitation when the precipitation intensity comes up to 155 mm/d, and the landslide occurs at an accumulated precipitation of 304 mm. Overall, the results can provide a reliable theoretical basis and abundant experimental data for the prevention, monitoring, and forecasting of geological disasters in granitic areas.

scholarly journals Effect of Salt Content on the Evaporation and Cracking of Soil from Heritage Structures

2021 ◽  
Vol 2021 ◽  
pp. 1-9
Author(s):  
Kai Cui ◽  
Xiaozheng Zhao ◽  
Mingming Hu ◽  
Chen Yang ◽  
Guanchang Xie
Keyword(s):  
Fractal Dimension ◽  
Water Content ◽  
Salt Content ◽  
Residual Water ◽  
Fracture Development ◽  
Nacl Concentration ◽  
The Matrix ◽  
Matrix Suction ◽  
Rate Of Evaporation ◽  
Cracking Process

The degree of damage to heritage structures in arid areas can be particularly serious due to long-term exposure to a harsh arid climate. In this paper, the characteristics of evaporation and cracking of soil taken from heritage structures with different NaCl concentrations are experimentally investigated by subjecting saturated soil samples taken from the Wang-Jing tower in Weihui City, Henan Province. Making soil sample of water content of 110% is used to test the rate of evaporation at a constant temperature and humidity, through which the changes in the evaporation rate, water content, fracture development, and fracture fractal dimension are obtained. The results show that, (1) with higher water content, NaCl can affect the evaporation process by increasing the matrix suction of the soil of the Wang-Jing tower and then affect the cracking process of soil. When 0%, 1%, 2%, and 4% NaCl are added, the residual water content of the samples is 3.15%, 4.23%, 4.82%, and 5.89%, respectively, which show an obvious trend of increasing water content; (2) the period with a stable fracture fractal dimension of the samples is shortened with an increase in NaCl concentration, and its maximum fractal dimension is reduced in turn; and (3) at a lower water content, NaCl crystallizes and precipitates in the pores of the soil, which provide a cementitious effect among the soil particles, thus inhibiting crack development.

scholarly journals Experimental Study on the Effect of Key Factors on the Soil–Water Characteristic Curves of Fine-Grained Tailings

2021 ◽  
Vol 9 ◽  
Author(s):  
Baofeng Cao ◽  
Yakun Tian ◽  
Rong Gui ◽  
Yong Liu
Keyword(s):  
Moisture Content ◽  
Soil Water ◽  
Dry Density ◽  
Key Factors ◽  
Fine Grained ◽  
Volumetric Moisture Content ◽  
The Matrix ◽  
Van Genuchten Model ◽  
Matrix Suction ◽  
Water Holding

The soil–water characteristic curve (SWCC) is an essential parameter for studying the mechanical properties of unsaturated tailings, and it plays an important role in stability assessment and prediction of unsaturated tailings dams. In this paper, the matrix suction was measured indirectly by a filter paper-based method to investigate the effects of key factors (gradation, temperature, and initial dry density) on the soil–water characteristic curves of fine-grained tailings, and the Van Genuchten model was adopted to obtain the empirical equation of SWCC and to verify the accuracy of experimental results. The results showed the following: 1) the Van Genuchten model fits well the relationship between matric suction and volumetric moisture content of fine-grained tailings, indicating that experimental data determined by filter paper-based method is accurate and appropriate; 2) at the same volumetric moisture content, the matrix suction increased with decreasing average particle size, and the decrease in temperature will increase the matrix suction and water-holding capacity of fine-grained tailings, and the matrix suction of the tailings in summer is 38.3% lower than that in winter under the natural volumetric moisture content (14.0%); 3) when the saturation degree of fine-grained tailings is less than 60%, the greater the initial dry density, the better the water-holding capacity and matrix suction.

scholarly journals Total mercury distribution among soil aggregate size fractions in a temperate forest podzol

2018 ◽  
Vol 8 ◽  
Author(s):  
Antía Gómez Armesto ◽  
Lucía Bibián-Núñez ◽  
Claudia Campillo-Cora ◽  
Xabier Pontevedra-Pombal ◽  
Manuel Arias-Estévez ◽  
...  
Keyword(s):  
Temperate Forest ◽  
Aggregate Size ◽  
Fine Sand ◽  
Soil Aggregate ◽  
Coarse Sand ◽  
Coarse Silt ◽  
Fine Silt ◽  
Size Fractions ◽  
Total Hg ◽  
Sand Size

This study determined the distribution of total Hg (Hg<sub>T</sub>) among aggregate size fractions in the A, E, Bh and Bs horizons of a representative temperate forest podzol. The aggregate distribution was dominated by the coarse sand size fraction (average of 55%) followed by fine sand (29%), fine silt (10%), coarse silt (4%) and clay (2%). In general, Hg<sub>T</sub> mean values increased as the aggregate size become smaller: clay (170 ng g<sup>-1</sup>) &gt; fine silt (130 ng g<sup>-1</sup>) &gt; coarse silt (80 ng g<sup>-1</sup>) &gt; fine sand (32 ng g<sup>-1</sup>) &gt; coarse sand (14 ng g<sup>-1</sup>). Total Hg enrichment in clay-sized aggregates ranged from 2 to 11 times higher than the values shown by the bulk soil (&lt; 2 mm). The accumulation of Hg<sub>T</sub> in the finer size aggregates was closely related to total organic C, Na-pyrophosphate extracted C, metal (Al, Fe)-humus complexes and Al and Fe oxyhydroxides. Indeed, these parameters varied significantly (<em>p </em>&lt; 0.05) with the aggregate size and their highest values were found in the finer fractions. This suggested the role of these soil compounds in the increase of the specific surface area per mass unit and negative charges in the smallest aggregates, favouring Hg retention. Mercury accumulation factor (Hg<sub>AF</sub>) values reached up to 10.8 in the clay size aggregates, being close to 1 in sand size fractions. Regarding Hg enrichment factors (Hg<sub>EF</sub>), they were &lt; 4 (“moderate pollution” category) in most of the horizons and aggregate sizes. Grain size mass loading (GSF<sub>Hg</sub>) revealed that finer fractions had a higher Hg loading than their mass fractions, with a notable contribution of fine silt which made up &gt; 50% of Hg<sub>T</sub> in Bh and Bs horizons. The potential ecological risk index (PERI<sub>Hg</sub>) increased as the aggregate size decreased, with the highest values in the illuvial horizons (45-903) and lowest in the E horizon (3-363). Heterogeneous distribution of Hg in the soil aggregate size fractions must be considered for Hg determination for purposes such as critical loads, background values or environmental risk indices. In addition, Hg accumulation in finer aggregates could be of concern due to its potential mobility in forest soils, either transferred by leaching to groundwater and freshwaters or mobilized by runoff in surface horizons.

RELEASE AND FIXATION OF POTASSIUM IN DIFFERENT SIZE FRACTIONS OF SOME CANADIAN SOILS AS RELATED TO THEIR MINERALOGY

1963 ◽  
Vol 43 (1) ◽  
pp. 123-134 ◽  
Author(s):  
A. J. MacLean ◽  
J. E. Brydon
Keyword(s):  
Particle Size ◽  
Ammonium Acetate ◽  
Exchangeable Potassium ◽  
Coarse Silt ◽  
Brown Forest Soil ◽  
Average Amount ◽  
Fine Silt ◽  
Canadian Soils ◽  
Total Potassium ◽  
Medium Silt

The average amount of non-exchangeable potassium removed by H-resin and boiling 1 N HNO3 from the clay in eleven Canadian soils was about twice that in the fine silt, about four times that in the medium silt, and about eleven times that in the coarse silt and sand. Continuous leaching with 0.01 N HCl also removed four times as much potassium from the clay as from the medium silt. The amounts released were usually less from the clay of four Podzols than from the clays of a Brown Chernozemic, a Brown Podzolic, a Brown Forest, and three Dark Grey Gleysolic soils.The percentage of total potassium released from K-bearing minerals by the above procedures was usually in the following order: feldspar < illite < muscovite < biotite.Although fixation of added potassium against extraction with ammonium acetate usually decreased with increasing particle-size, there was considerable fixation in the fine and medium silts. The clays of two Dark Grey Gleysolic and a Brown Forest soil fixed the highest amounts of potassium.Differences in the release and fixation of potassium were not related to the contents of feldspar, illite, vermiculite and mixed-layer minerals in the clays, nor to the amounts of feldspar and mica in the non-clay fractions.

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