Laboratory permeability tests on sand: influence of the compaction method on anisotropy

1989 ◽  
Vol 26 (4) ◽  
pp. 614-622 ◽  
Author(s):  
Robert P. Chapuis ◽  
Denis E. Gill ◽  
Karsten Baass
Keyword(s):  
Void Ratio ◽  
Soil Mass ◽  
Granular Soils ◽  
Anisotropy Ratio ◽  
Soil Permeability ◽  
Compacted Soils ◽  
Anisotropy Index ◽  
Preparation Mode ◽  
Hydraulic Anisotropy ◽  
Compaction Method

New laboratory results are presented on how densification influences the hydraulic anisotropy of a sand. Results are given for two compaction modes. Tests were performed at different densities in order to derive the curves kv(e) and kh(e). The samples were statically compacted in the first series and dynamically compacted in the second series. The ratio rk = kh/kv is different for the two series. It is higher than 1 for static compaction and lower than 1 for dynamic compaction. Thus, the anisotropy ratio of granular soils can take several values for the same void ratio, depending on the preparation mode. Even if the anisotropy ratios differ, the first invariant of the hydraulic conductivity tensor, 11k, is found to be a function of e only for this sand, regardless of the densification mode. The evolution of an adimensional anisotropy index, I1k/kv, versus a density index, Ie, is compared for the sand and a dispersed clay. The evolutions are nearly identical, which means that the hydraulic anisotropy of natural homogeneous soils may be similar for sediments having settled in still water and influenced subsequently by gravity only. From an engineering viewpoint, a reasonably good fit is obtained between experimental results and predictive charts. The results also demonstrate that the high apparent anisotropy often found either in natural or in compacted soils is not induced mainly by deposition or compaction but rather is due to nonuniformity or segregation in the soil mass. Key words: soil, permeability, anisotropy, laboratory, compaction.

scholarly journals Modeling of Minimum and Maximum Void Ratios of Granular Soils

2021 ◽  
Vol 2021 ◽  
pp. 1-10
Author(s):  
Xiaoxu Qian ◽  
Xin Liu ◽  
Zhiwei Shao ◽  
Yunqiang Shi ◽  
Siqing Zhang ◽  
...  
Keyword(s):  
Size Distribution ◽  
Analytical Methods ◽  
Void Ratio ◽  
Experimental Tests ◽  
Experimental Results ◽  
Granular Soils ◽  
Soil Permeability ◽  
Empirical Relationships

Determining the maximum and minimum void ratios of granular soils is very important because it can be correlated with engineering behaviors such as soil permeability. Empirical relationships can be used for determining the void ratio, but they have many limitations related to the shape and the size distribution of the grains. Analytical methods improve the empirical relationships. In this paper, we present enhancements to the model of Chang et al. by combining the model of Youd et al., as Chang–Youd models, to make it more convenient and also to extend its usage to be suitable for determining the maximum void ratio. The Chang–Youd models are verified with experimental tests performed by the authors. Compared with the experimental results in the literature, the Chang–Youd models are also effective but more convenient and practical.

scholarly journals Toward a better understanding of the effects of cement treatment on microstructural and hydraulic properties of compacted soils

2018 ◽  
Vol 163 ◽  
pp. 06007
Author(s):  
Harifidy Ranaivomanana ◽  
Andry Razakamanantsoa
Keyword(s):  
Hydraulic Properties ◽  
Silty Sand ◽  
Dry Density ◽  
Granular Soils ◽  
Maximum Dry Density ◽  
Compacted Soils ◽  
Compaction Method ◽  
Different Levels ◽  
Standard Compaction

This study deals with the problem of the experimental characterization of cement-treated compacted soils in terms of microstructural and hydraulic properties. Some tests are conducted on two different types of soil: silty sand and clay as fine soils and gravelous sand and alterite as granular soil. Some samples are mixed with 5% of cement and compacted at different levels (i.e., 85%, 95%, 100% and 105% of the maximum dry density, respectively, as achieved using the standard compaction method). The results of the mercury intrusion porosimetry (MIP) tests performed on these cement-treated soils reveal significant changes as regards macropores due to the combined effects of treatment and compaction. Consequently, a decrease in the permeability is clearly observed for all the tested soils when the degree of compaction increases. This decrease is significantly greater in fine soils, which are more sensitive to compaction effects than granular soils.

scholarly journals Mechanical Properties and Micro Mechanism of Nano-Clay-Modified Soil Cement Reinforced by Recycled Sand

2021 ◽  
Vol 13 (14) ◽  
pp. 7758
Author(s):  
Biao Qian ◽  
Wenjie Yu ◽  
Beifeng Lv ◽  
Haibo Kang ◽  
Longxin Shu ◽  
...  
Keyword(s):  
Shear Strength ◽  
Void Ratio ◽  
Soil Mass ◽  
Direct Shear ◽  
Test Results ◽  
The Sustainable Development ◽  
Direct Shear Tests ◽  
Soil Cement ◽  
Nano Clay ◽  
New Material

To observe the effect of recycled sand and nano-clay on the improvement of the early strength of soil-cement (7d), 0%, 10%, 15% and 20% recycled sand were added. While maintaining a fixed moisture content of 30%, the ratios of each material are specified in terms of soil mass percentage. The shear strength of CSR (recycled sand blended soil-cement) was investigated by direct shear test and four groups of specimens (CSR-1, CSR-2, CSR-3 and CSR-4) were obtained. In addition, 8% nano-clay was added to four CSR groups to obtain the four groups of CSRN-1, CSRN-2, CSRN-3 and CSRN-4 (soil-cement mixed with recycled sand and nano-clay), which were also subjected to direct shear tests. A detailed analysis of the modification mechanism of soil-cement by recycled sand and nano-clay was carried out in combination with scanning electron microscopy (SEM) and IPP (ImagePro-Plus) software. The test results showed that: (1) CSR-3 has the highest shear strength due to the “concrete-like” effect of the incorporation of recycled sand. With the addition of 8% nano-clay, the overall shear strength of the cement was improved, with CSRN-2 having the best shear strength, thanks to the filling effect of the nano-clay and its high volcanic ash content. (2) When recycled sand and nano-clay were added to soil-cement, the improvement in shear strength was manifested in a more reasonable macroscopic internal structure distribution of soil-cement. (3) SEM test results showed that the shear strength was negatively correlated with the void ratio of its microstructure. The smaller the void ratio, the greater the shear strength. This shows that the use of reclaimed sand can improve the sustainable development of the environment, and at the same time, the new material of nano-clay has potential application value.

scholarly journals Interpretation of the loading–wetting behaviour of compacted soils within the “MPK” framework. Part I: Static compaction

2016 ◽  
Vol 53 (5) ◽  
pp. 783-805 ◽  
Author(s):  
Tanvirul Islam ◽  
Jayantha Kodikara
Keyword(s):  
Moisture Content ◽  
Unsaturated Soils ◽  
Void Ratio ◽  
Swelling Pressure ◽  
The State ◽  
Moisture Ratio ◽  
Parameter Determination ◽  
Compacted Soils ◽  
Pressure Development ◽  
State Path

Depending on the state paths, loading–wetting of compacted unsaturated soils can exhibit complex volumetric behaviour, such as swelling, collapse, collapse followed by swelling, swelling followed by collapse, and swelling pressure development. Microscopically, these behaviours arise from complex interactions among applied stresses, air–water pressure deficit or suction at the water menisci, moisture content or degree of saturation in the voids, and the nature of the micro- and macrosoil aggregates of compacted soils that depend on the level of suction. While significant advances have been made in modelling hydromechanical behaviour of compacted unsaturated soils taking these interactions into account, input parameter determination requires advanced testing equipment and the testing processes can be very time-consuming. In 2012, a relatively simple and practical framework within the void ratio – moisture ratio (water volume / solid volume) – net stress space (referred to as the MPK framework) has been proposed by Kodikara to explain–predict these state paths. A desirable feature of this framework is that it identifies a direct link between the well-known compaction curve and the compacted soil constitutive behaviour. This paper presents a comprehensive series of tests on statically compacted soils, the results of which are in close agreement with this framework. Two soil types, namely lightly reactive kaolin and more reactive clay (referred to as Merri Creek soil), were used in the testing. The soils were prepared with different moisture contents from the dry state and statically compacted at constant water content to obtain void ratio – moisture ratio – net stress constitutive surfaces, as well as soil specimens for state path tests. The state path test results of yielding under loading, collapse under wetting, swelling pressure development, and change in yield pressure due to wetting are explained within this framework. In addition, some published data on a silty soil mixture were also analysed, highlighting that the framework is valid, regardless of the degree of reactivity of the soil. Suction was not measured in the authors’ experiments, as it was not required to explain the above state paths according to this framework. However, it is recognised that suction is the conjugate state variable to the moisture content. Therefore, in future experiments, suction will be measured and its role will be fully explained within the framework, adding more generality.

scholarly journals Characteristics of Compacted Fly Ash as a Transitional Soil

Materials ◽  
2020 ◽  
Vol 13 (6) ◽  
pp. 1387 ◽  
Author(s):  
Katarzyna Zabielska-Adamska
Keyword(s):  
Fly Ash ◽  
Void Ratio ◽  
Fine Particles ◽  
Penetration Resistance ◽  
Cohesive Soils ◽  
Fine Content ◽  
Compacted Soils ◽  
Intergranular Void Ratio ◽  
Transitional Soils ◽  
Intergranular Void

Cohesive and non-cohesive soils show a number of properties typical of a given category. Cohesive soils are characterized by cohesion, and the properties of compacted soils closely depend on moisture at compaction. However, many researchers have found the existence of so-called mixed or transitional soils. Compacted transitional soils, macroscopically recognized as non-cohesive, are characterized by mechanical properties and hydraulic conductivity which are strictly dependent on the moisture content at compaction. The aim of this work is to show the influence of the content of fine particles in fly ash on the variation of California Bearing Ratio (CBR) values as a parameter strictly dependent on initial compaction. The CBR values were interpreted in terms of moisture at compaction, void ratio and intergranular void ratio. Three different research samples were selected with fine contents of 45%, 55% and 70%; all samples corresponded in terms of grading with sandy silt. Fly ash containing only non-plastic fines behaved as cohesive soils despite the lack of plasticity. The CBR values decreased with increasing moisture at compaction or void ratio. The CBR values, plotted as a function of the intergranular void ratio, have lower penetration resistance together with fine content.

Instability and liquefaction of granular soils under undrained and partially drained states

1998 ◽  
Vol 35 (6) ◽  
pp. 1053-1062 ◽  
Author(s):  
Y P Vaid ◽  
A Eliadorani
Keyword(s):  
Experimental Investigation ◽  
Triaxial Test ◽  
Void Ratio ◽  
Granular Soils ◽  
Saturated Sand ◽  
Stress Space ◽  
Sand Liquefaction ◽  
Undrained Shear

An experimental investigation of the initiation of instability (liquefaction) in saturated sand under partially drained conditions is presented. The domain of stress space in which this instability develops is identified under various degrees of drainage, and its relationship to the zone of instability observed under undrained shear is explored. It is shown that partially drained conditions may render sand unstable that would otherwise be stable in a completely undrained state. Extremely small void ratio increases that cannot be regarded as physical loosening of sand, if sand is partially drained, contribute to instability. Implications of the findings are discussed in practical problems of liquefaction.Key words: sand, liquefaction, undrained, partially drained, instability, triaxial test.

scholarly journals COMPRESSIBILITY BEHAVIOUR OF COMPACTED SOILS – HYPERBOLIC MODELLING

2020 ◽  
Author(s):  
U. Venkata Ratnam ◽  
K. Nagendra Prasad
Keyword(s):  
Void Ratio ◽  
Model Parameters ◽  
Initial State ◽  
Compacted Soils ◽  
One Dimensional ◽  
Initial Void Ratio ◽  
Two Samples ◽  
Earth Structures ◽  
Hyperbolic Behavior ◽  
Engineering Projects

Compacted soils constitute most engineering projects such as earth dams,embankments, pavements, and engineered slopes because of their high shear strengthand low compressibility. The compressibility behavior of compacted soils is a key soilparameter in the design of earth structures but it is not determined correctly owing topartly saturated state. The compressibility of compacted soils can be better evaluatedunder the framework of hyperbolic behavior. One dimensional Consolidation tests oncompacted specimens were conducted using conventional oedometer apparatus underconstant water content condition. Tests were conducted by compact the soil specimensat respective optimum moisture contents for eight different soil samples, of varyinggrain size characteristics and consistency limits, collected from Tirupati Region. Themain objective of this study is to examine the compressibility behavior of compactedsoils to propose a phenomenological model. It is observed that the compressibilitybehavior can be captured by hyperbolic modeling with model parameters involved inthe behavior being initial void ratio, e0, representing the initial state of soil and otherhyperbolic constants linked to this state. The data of 6 samples were used fordeveloping the model and the data of remaining two samples were used for predictingthe observed response from the model proposed. The data of published literature hasalso been used to predict the experimental behavior to bring out the merits of themodel proposed.

Nature of Soil Erodibility

1999 ◽  
Author(s):  
Robert F. Keefer
Keyword(s):  
Soil Texture ◽  
Water Movement ◽  
Soil Aggregates ◽  
Soil Mass ◽  
Soil Aggregate ◽  
Soil Permeability ◽  
Soil Infiltration ◽  
Clay Particles ◽  
Coarse Texture ◽  
Stable Aggregate

Inherent properties of a soil determine the extent to which that soil will erode. These properties are soil texture, soil structure, soil permeability, and the amount of soil organic matter. Soil texture consists of a mixture of soil particle sizes of sand, silt, and clay. Soil texture is also related to water movement into the soil [infiltration] and water movement through a soil (permeability). Sand grains are large and difficult to move; however, they are easily detached. Clay particles often stick together and therefore are difficult to detach; however, once detached the clays remain suspended and are easily carried and separated from the original soil mass by water. Silt is intermediate in size between sand and clay, but silt is both easily detached and easily transported. Thus, any soil that has large amounts of silt will erode easily. Infiltration. Water moves into and within a soil through the large macropores and only a very limited amount in the small micropores. Sandy soils have many large pores allowing water to move into the soils by infiltration. Conversely, clay soils have many microspores through which water passes only very slowly. Therefore, during a moderate storm, runoff and erosion would be greater from a soil with more fine textured clays than from a soil where coarse texture dominates. Permeability. Once water enters a soil, it flows within the soil. The extent of internal movement of water in a soil is the permeability of that soil. A soil aggregate is a soil granule or soil crumb consisting of a number of soil grains, that is, silt or clay, held together by a cementing substance. Aggregation is the condition of a soil having many individual aggregates. Soils that have many large stable aggregate are more permeable and are difficult to detach and erode. An aggregate has stability when it is not broken easily by water. Soil aggregates help keep the soil receptive to rapid infiltration of water and keep water from moving over the soil and eroding it.

scholarly journals A volume–stress model for sands under isotropic and critical stress states

2008 ◽  
Vol 45 (11) ◽  
pp. 1639-1645 ◽  
Author(s):  
Daichao Sheng ◽  
Yangping Yao ◽  
John P. Carter
Keyword(s):  
Critical Stress ◽  
Void Ratio ◽  
Triaxial Compression ◽  
Granular Soils ◽  
Additional Parameter ◽  
Stress Model ◽  
Stress States ◽  
Volume Stress ◽  
State Curve ◽  
Cam Clay

A simple volume–stress model for granular soils under isotropic and critical stress states is presented. The model is formulated in the double logarithmic space of void ratio versus mean stress. It has the same number of parameters as used in the Cam Clay models to describe isotropic compression, with one additional parameter to define the critical state curve. The model can qualitatively describe a number of unique features of sand behaviour. Comparison with experimental data indicates that the model is able to predict well the volume change of a range of different sands subjected to isotropic and triaxial compression.

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