Influence Of Fines Content Research Articles

The influence of fines content on ground collapse due to internal erosion of sand-fines mixtures around defective pipes

Ground collapse caused by defective pipelines has become a global issue with the continuous advancement of urbanization. This study reproduced the internal erosion process of sand-fines mixtures around defective pipes through a series of model tests considering a relatively wide range of fines content and three hydraulic conditions. The erosion characteristics and the evolution of the cavity were analyzed to determine the triggering mechanisms of ground collapse. The results indicate that the formation and evolution of the cavity predominantly depend on fines content under hydraulic loading, which is replaced by ground settlement at lower fines content. Moreover, the scouring of groundwater amplifies the impact of internal erosion, which means the marked ground settlement at lower fines content or the expansion of the cavity even to ground collapse at higher fines content. To prevent sudden ground collapse, it is not recommended to use sand-fines mixtures with a fines content of more than 10% as embedment materials.

Influence of Fines Content and Pile Surface Characteristics on the Pullout Resistance Performance of Piles.

In this study, the direct shear test and model pullout test results are presented to assess the impact of soil fines content and shear resistance characteristics of the pile-soil interface on the pullout resistance of drilled shafts. The direct shear test on the soil-pile interface was conducted based on the pile surface simulated using sandpaper with three roughness types (#24, #40, and #400) and varying fines content. The direct shear test results of soil showed that the internal friction angle decreased by about 29% and the cohesion increased by about 110% when the fine powder content increased from 5% to 30%. Specifically, in the case of soil-sandpaper (#24), the interface friction angle decreased by about 31%, and the adhesion increased by about 16%. The sandpaper with a roughness of #40 and #400 also showed a similar trend. Normalizing the shear strength parameters from the direct shear test demonstrated an intersection between the normalized curves of the friction angle and cohesion (or adhesion) within a specific fines content range. This suggests that shear strength parameters play a significant role based on fines content. Analyzing the normalized index using model pullout test results indicated the necessity to evaluate the contribution of friction angle and cohesion (or adhesion) of the shear surface, taking into account the fines content of the soil for predicting pile pullout resistance.

Discussion of “influence of fine content on undrained monotonic behavior of carbonate sand”, by E. Ghanbari Alamouti, R. Ziaie Moayed and S. A. Naeini (2023); Marine Georesources & Geotechnology, DOI: 10.1080/1064119X.2023.2204484.

This discussion has been written to provide an in-depth overview of the central subject of the previously published in in the Marine Georesources and Geotechnology journal. The paper titled "Influence of fine content on undrained monotonic behavior of carbonate sand ". It is intended to augment the content’s coherence and serve as a supplementary discussion paper authored by Ghanbari Alamouti, Ziaie Moayed, and Naeini (2023).

Influence of fine content on undrained monotonic behavior of carbonate sand

The behavior of carbonate sand is different from that of siliceous sand in terms of high compressibility and crushability, specific particle shape, and physical properties. Thus, investigating the behavior of these soils is of great importance because of their prevalence in coastal areas. Nevertheless, a few studies have considered the presence of fines in the mixture with carbonate sand. The present study explores the influence of non-plastic fines on the undrained monotonic behavior of Bushehr carbonate sand. For this purpose, 30 undrained monotonic triaxial tests were performed on carbonate sand with silt ranges of 0% to 40% with two different void ratios. According to the results, the undrained shear strength of carbonate sand diminished with the addition of silt percentage up to 20%, and increased dramatically at 30% silt content. Also, the results of 40% silty sand revealed that this sample is stronger than samples with 10% and 20% silt content. By surveying the location of the phase transformation point in samples, it was observed that silt particles reduce the dilative phase. Also, confining pressure intensified the contractive phase while relative density had the opposite effect. The results showed that the effect of particle breakage is negligible in this study.

Experimental Study on the Gmax Characteristics of the Sand-Silt Mixed Soil Materials Using Bender Element Testing.

To study the small strain shear modulus (Gmax) of saturated sand-silt mixed soil materials, a series of tests were conducted using the bender element apparatus, and the influences of fines content (FC), relative density (Dr), and effective confining pressure () were taken into consideration. The test results indicate that the Gmax of the mixed soil materials decreases first and then increases with the FC up to 100% with Dr = 35% and 50%, while the Gmax decreases with the increasing FC when Dr = 60%. Moreover, for a given Dr, the Gmax increases with the increasing , and the increase rate keeps constant under various FCs. The Gmax of specimens under various FCs decreases with the increase of the void ratio (e). The decrease rate between the Gmax and e differs when the is given, which is influenced by the FC. The Gmax of the mixed soil materials can be evaluated by the Hardin model when the FC is determined. The best-fitting parameter A of the Hardin model first decreases and then increases as FC increases. The revised Hardin model, considering the influence of FC, , and e, can be used to evaluate the Gmax for different types of sand-silt mixed soil materials. The error between the evaluated and tested Gmax is less than 10%.

Influence of Fines Content on the Stability of Volcanic Embankments under Rainfall and Earthquake

This study aims to investigate the effects of fine content on the mechanical behavior of embankments constructed from volcanic soil subjected to rainfall and earthquake. To accomplish this purpose, a series of 1 g model experiments on slopes using Komaoka volcanic coarse-grained soils as materials was conducted with a spray nozzle and shaking table. In the experiments, shear strain, acceleration, pore water pressure, and saturation degree were monitored and measured to provide an understanding of the failure mechanism of the model embankment with different fine particle contents during post-rainfall earthquakes. The results show that the increase in the fines content of the volcanic soil reduces the permeability of the volcanic embankment but has no significant effect on rainfall-induced slope failure until the shear strain is less than 6%. Moreover, the seismic resistance of volcanic slopes subjected to previous rainfall increases when the fine particle content increases to a certain threshold of about 27%.

Compressibility and permeability of sand–silt tailings mixtures

Microstructure showing the involvement of the fine and coarse grains in the soil skeleton is evaluated. Incremental loading tests using a stress-dependent permeameter are conducted on the mixtures of poorly graded sand and nonplastic fines originating from tailings. The results are compared with the published data of various tailings. It is shown that increasing the fines content from 0% to 100%, the involvement of the fine and coarse components of soil skeleton can be classified into four categories: no fines involvement (<10% fines), fines partially involved (10%−35% fines), increasing cushioning effect surrounding the coarse (35%−40% fines), and constant cushioning effect (>40% fines). At the same consolidation stress, the void ratio, e, rapidly decreases for fines less than 30%, then almost remains constant between 30% and 50% fines, and gradually increases for fines exceeding 50%. The hydraulic conductivity, k, decreases more than 20-fold as the fines content increases from 12% to 50%, then remains constant. k is proportional to [e3/(1 + e)]A and inversely proportional to S2, where A is a factor describing the effect of particle angularity and S is the specific surface. Finally, the influence of fines content on the seepage-induced internal stability is discussed.

Influence of fines content on liquefaction from a critical state framework: the Christchurch earthquake case study

In earthquake engineering practice, the liquefaction potential of soils is commonly evaluated through simplified procedures. These approaches are suitable for sands with very low to no fines content, which have been traditionally thought to be the only liquefiable materials. However, field observations and experimental research have extensively demonstrated that low plasticity silty sands can also be highly liquefiable. Thus, this paper investigates the effect of nonplastic fines contents on the liquefaction potential of soils, taking the 2010–2011 Canterbury Earthquake Sequence as a case study. The validity of standard simplified procedures for high fines content soils is critically evaluated and compared with a finite element model based on a full solid–fluid coupled formulation. The model includes a state parameter-based constitutive law within the generalised plasticity theory, which allows the fines content to be taken into account explicitly. The standard simplified procedures are shown to be less effective in the evaluation of liquefaction potential in soils with high fines content but are still indispensable tools for evaluating the performance of soils over large urban areas. As the main conclusion, it is recommended that empirical models are complemented with an advanced numerical analysis in those cases where silty sands with high fines content are identified, as its outcomes can more realistically represent the soil behaviour during a seismic event.

Laboratory investigation of unconfined compression behavior of ice and frozen soil mixtures

Unconfined compression test (UCT) is widely conducted in laboratories to evaluate the mechanical behavior of frozen soils. However, its results are sensitive to the initial conditions of sample creation by freezing as well as the end-surface conditions during loading of the specimen into the apparatus for testing. This work compared ice samples prepared by three-dimensional and one-dimensional freezing. The latter created more-homogenous ice samples containing fewer entrapped air bubbles or air nuclei, leading to relatively stable UCT results. Three end-surface conditions were compared for UCT on ice specimens made by one-dimensional freezing. Steel disc cap with embedded rubber was found most appropriate for UCT. Three frozen materials (ice, frozen sand, and frozen silt) showed different failure patterns, which were classified as brittle failure and ductile failure. Ice and frozen sand showed strain-softening, while frozen silt showed strain-hardening. Subsequent investigation considered the influence of fines content on the unconfined compression behavior of frozen soil mixtures with fines contents of 0-100%. The mixtures showed a brittle-to-ductile transition of failure patterns at 10%-20% fines content.

Influence of Fine Content on the Soil–Water Characteristic Curve of Unsaturated Soils

Unsaturated soils often exist as a mixture of coarse and fine particles in nature. However, the relationship between fine content and the soil–water characteristic curve (SWCC) is not sufficiently understood. In this paper, ten kinds of mixed soils with different percentages of fine contents were tested with the pressure-membrane apparatus, and the SWCC for each fine content was obtained. The results showed that when keeping the fine content between 10 and 60%, the water-holding capacity of the soil gradually decreased as the fine content increased. Otherwise, the water-holding capacity of the soil increased. With the same effect of matrix suction, the volumetric water content increased initially and then decreased with the increase of fine content. With the fine content within the range of 10–60%, a higher fine content resulted in a larger dehydration rate; otherwise, the dehydration rate of the soil decreased. In addition, a new fitting model was established for SWCC. The applicability of the new model was verified by combining new data with the existing experimental data and then discussing the physical meaning of each parameter in the model. Through the research in this paper, the quantitative relationship between fine content and SWCC was clarified, and a new SWCC model was established. The conclusions in this paper are helpful to understand the effect of the proportion of fine particles on the SWCC. The physical parameters of unsaturated soils which mixes fine and coarse particles, such as adsorption coefficient, permeability coefficient, and shear strength, could be obtained.

Influence of fines content on the anti-frost properties of coarse-grained soil

This paper aims to determine the optimal fines content of coarse-grained soil required to simultaneously achieve weaker frost susceptibility and better bearing capacity. We studied the frost susceptibility and strength properties of coarse-grained soil by means of frost heaving tests and static triaxial tests, and the results are as follows:(1) the freezing temperature of coarse-grained soil decreased gradually and then leveled off with incremental increases in the percent content of fines;(2) the fines content proved to be an important factor influencing the frost heave susceptibility and strength properties of coarse-grained soil. With incremental increases in the percent content of fines, the frost heave ratio increased gradually and the cohesion function of fines effectively enhanced the shear strength of coarse-grained soil before freeze-thaw, but the frost susceptibility of fines weakened the shear strength of coarse-grained soil after freeze-thaw;(3) with increasing numbers of freeze-thaw cycles, the shear strength of coarse-grained soil decreased and then stabilized after the ninth freeze-thaw cycle, and therefore the mechanical indexes of the ninth freeze-thaw cycle are recommended for the engineering design values; and(4) considering frost susceptibility and strength properties as a whole, the optimal fines content of 5% is recommended for railway subgrade coarse-grained soil fillings in frozen regions.

Influence of Fines Content on Consolidation and Compressibility Characteristics of Granular Materials

Various behaviour of soil under loading results to large extent from kind of soil considered. There is a lot of literature concerning pure sand or plastic clays, while little is known about materials, which are from classification point of view, between those soils. These materials can be considered as cohesionless soils with various fines content. The paper present results of tests carried out in large consolidometer on three kinds of soil, containing 10, 36 and 97% of fines content. Consolidation, permeability and compressibility characteristics were determined. Analysis of the test results allowed to formulate conclusion concerning change in soil behaviour resulting from fines content.

The influence of fines content and size-ratio on the micro-scale properties of dense bimodal materials

This paper considers factors influencing the fabric of bimodal or gap-graded soils. Discrete element method simulations were carried out in which the volumetric fines content and the size ratio between coarse and fine particles were systematically varied. Frictionless particles were used during isotropic compression to create dense samples; the coefficient of friction was then set to match that of spherical glass beads. The particle-scale data generated in the simulations revealed key size ratios and fines contents at which transitions in soil fabric occur. These transitions are identified from changes in the contact distributions and stress-transfer characteristics of the soils and by changes in the size of the void space between the coarse particles. The results are broadly in agreement with available experimental data on minimum void ratio and contact distributions. The results have implications for engineering applications including assessment of the internal stability of gap-graded soils in embankment dams and flood embankments.

Influence of fines content on durability of slag cement concrete produced with limestone sand

The effectiveness of limestone sand fines (material finer than 0.063mm) in controlling durability performance of slag cement concrete was investigated in an experimental program. Slag cement concrete specimens incorporating limestone aggregate were produced in two water-cement ratios leading to moderate and high-level durability. Linear regression analysis was applied to evaluate the rates and significance of change in durability performance parameters of concrete at varied levels of fines content ranging between 0 and 15%. Significant relationships between performance parameters (compressive strength, water penetration resistance, chloride migration coefficient, resistivity and abrasion resistance) and fines content were found in statistical analysis depending on the water-cement ratio. Compared to low water-cement ratio concrete specimens, the contribution of the fines on durability was more prominent for the concrete mixes with high water-cement ratio. The paper also presents a case-study on durability assessment in an on-going marine infrastructure project involving Izmit Bay Crossing Suspension Bridge. The findings obtained from the field conform with the output of this research.

Influence of fines content on the undrained cyclic shear strength of sand–clay mixtures

A series of undrained cyclic triaxial tests were performed on sand–clay mixtures with various sand–clay mixing ratios. Prior to the primary tests, the threshold fines content was examined by consistency tests, which was found to be approximately 20%. For sand–clay mixtures with a sand-matrix (fines content less than the threshold fines content), the cyclic shear strength of low-density mixtures increases and that of high-density mixtures decreases with increasing fines content. However, for sand–clay mixtures with a fines-matrix (fines content greater than the threshold fines content), there exists a unique correlation between the cyclic shear strength and global void ratio for different fines content. The equivalent granular void ratio is introduced in this paper to account for the contribution ratio of the fines to soil skeleton. As a result, a unique relationship between cyclic shear strength and equivalent granular void ratio was observed for pure sand and sand–clay mixtures with a sand-matrix.

Influence of Particle Size Distribution and Wettability on the Displacement of LNAPL in Saturated Sandy Soils

AbstractImmiscible displacement processes are of key importance in remediation actions of light nonaqueous phase liquid (LNAPL) contaminated soil and groundwater. LNAPLs remain trapped in soil pores after a spill or flushing process due to the interplay of viscous, gravity, and capillary forces. In this research immiscible displacement tests were conducted in homogenous and heterogeneous sand samples. Also, the influence of fine content, mineralogy, and wettability was evaluated by testing mixtures of coarse sand with silt, zeolite, bentonite, and hydrophobic sand. Obtained results highlight the importance of pore-scale heterogeneities on the resulting displacement pattern in macroscopically homogeneous samples, and show the preferential accumulation of LNAPLs at the interfaces between different materials in heterogeneous samples. Fine particle content shows no important consequences on residual saturation but significantly changes relative permeability. In addition, the presence of hydrophobic particles ...

On the influence of a non-cohesive fines content on small strain stiffness, modulus degradation and damping of quartz sand

The influence of a non-cohesive fines content on small-strain shear modulus Gmax, small-strain constrained elastic modulus Mmax, shear modulus degradation G(γ)/Gmax, damping ratio D(γ) and threshold shear strain amplitudes γtl and γtv has been studied in approx. 130 resonant column (RC) tests with additional P-wave measurements by means of piezoelectric elements. Specially mixed continuous grain size distribution curves of a quartz sand with varying fines contents (0≤FC≤20%, defined as the mass percentage of grains with size d<0.063mm according to DIN standard code) and uniformity coefficients (1.5≤Cu≤50) have been tested at different relative densities and pressures. A significant decrease of Gmax and Mmax with increasing fines content was observed, while the modulus degradation curves G(γ)/Gmax were found rather independent of FC. A pressure-dependent decrease of the damping ratio and a slight increase of the threshold shear strain amplitudes γtl and γtv with fines content were measured. Extensions of several empirical equations for Gmax, Mmax, G(γ)/Gmax and D(γ) considering the influence of the fines content are proposed in the paper.

Influence of fine content and water content on the resilient behaviour of a natural compacted sand

Granular materials are often used in pavement structures. The influence of fine content and water content on the mechanical behaviour is very important. In this work, first, we present the resilient behaviour of compacted clayey natural sands with two different fine contents using the repeated load triaxial tests. The samples were compacted at different water contents with the same dry density. It can be stated that an increase in the fine content (from 4% to 7.5%) causes an increase in the volumetric strains and shear strains for all the water contents. The influence of water content can be considered negligible comparing to the influence of fine content. Then, the experimental results were simulated using the nonlinear elastic model (modified Boyce model) generally used for the resilient behaviour of the unsaturated granular soils. The results show that the model can correctly predict the variation of the volumetric strains and the shear strains with the mean stress for all the stress paths. Finally, finite element calculations carried out with CAST3M were performed to compare the deflection of a low traffic pavement with sub-base layers containing two different fine contents. The surface asphalt concrete layer and the base layer were taken the same for both structures. The modelling results show that the sub-base soil with higher fine content produces 37% higher deflection in the whole structure and that the effect of the water content is lower than that of the fine content.

Prediction of Undrained Monotonic and Cyclic Liquefaction Behavior of Sand with Fines Based on the Equivalent Granular State Parameter

AbstractThe undrained behavior of sand with fines under both monotonic and cyclic loading was investigated experimentally by triaxial testing. The testing program covers fines content ranging from 0 to 30%, and a wide range of initial void ratios and confining stresses. The spectrum of cyclic loading includes one- and two-way cyclic loading, and in the latter case, the cyclic loading may be symmetrical or nonsymmetrical. The influence of fines content can be captured by using the equivalent granular void ratio, e∗, in lieu of the void ratio, e. All steady-state data points can be described by a single relationship referred to as the equivalent granular steady-state line. This study proposes the concept of the equivalent granular state parameter, ψ∗, for capturing the combined effects of the stress state, density state, and fines content. The observed behavior can then be related to e∗ and/or ψ∗. Irrespective of fines contents, the behavior under monotonic loading can be classified into three types, and ψ∗...

Predicting onset of cyclic instability of loose sand with fines using instability curves

This study utilises the equivalent granular state parameter, ψ⁎, as a key parameter for studying static and cyclic instability and their linkage. ψ⁎ can be considered as a generalisation of the state parameter as first proposed by Been and Jefferies so that the influence of fines content in addition to stress and density state can be captured. Test results presented in this study conclusively showed that ψ⁎ at the start of undrained shearing and ηIS, the stress ratio at onset of static instability, can be described by a single relationship irrespective of fines content for both compression and extension shearing. This single relationship is referred as instability curve. However, the instability curve in extension shearing is different from that of compression. In this paper, the capacity of the instability curve in predicting triggering of cyclic instability was evaluated experimentally. An extensive series of undrained one-way (compression) and non-symmetric two-way cyclic triaxial tests, in addition to monotonic triaxial tests in both compression and extension were conducted for this evaluation. Furthermore, a published database for Hokksund sand with fines was also used. Test results show that cyclic instability was triggered shortly after the cyclic effective stress path crossed the estimated ηIS-zone(s) as obtained from instability curve(s) irrespective of whether instability occurs in the compression or extension side.