Effect Of Fines Content Research Articles

Effects of grading and particle characteristics on small strain properties of granular materials

A series of drained triaxial compression tests was conducted in order to evaluate the effects of grading and particle characteristics on the small strain stiffness of a wide variety of granular materials. To evaluate the quasi-elastic deformation property at small strain levels around 0.001% by static measurement, many small vertical cycles were applied at two isotropic stress states. The effects of maximum and mean particle diameters, fines content, coefficient of uniformity, and degree of particle angularity on the quasi-elastic vertical Young׳s moduli, Evs, by the static measurement were investigated. Within the limited range of grading and particle characteristics tested in the present study, the results showed that: (1) the Evs values were generally independent of maximum and mean particle diameters; (2) the Evs values seemed to decrease with increasing coefficient of uniformity; (3) the effects of fines content and particle angularity on the Evs values were not clear; and (4) the effects of the effective confining pressure on the above-mentioned three trends were insignificant.

Design, construction, operation and the effect of fines content and permeability on the seismic performance of tailings sand dams in Chile

The significant growth of the metallic mining industry over the last few decades has made the construction of tailings deposits of large dimensions necessary, tailings being the fine mining waste resulting from the milling and concentration processes. The most common types of tailings dam in mining are the tailings sand dam, a special kind of hydraulic fill dam, for two main reasons: because such dams need to be built over a longperiod of time, and due to the low cost of sand available from the tailings. In particular, this paper analyses the behaviour of tailings dams in Chile, one of the most seismically active countries in the world. The design and construction of tailings dams, as well as the effect of drain gravels and filter materials on the geotechnical behaviour of the tailings sands, are also discussed. The importance of the operational phase is addressed, because in tailings dams this phase can last many years and be the determinant in the final behaviour of the dams. Finally, recommendations to mitigate risks along the complete life cycle of the dams are given, and permeability and fines content effects as well as sand tailings drained and undrained strength are considered. El crecimiento significativo de la industria minera metalica en las recientes ultimas decadas, ha hecho necesaria la construccion de depositos de relave de grandes dimensiones. Los relaves son el desecho fino que resulta de los procesos de molienda y concentrado. Por dos razones principalmente, el tipo mas comun de presa de relaves en mineria es la presa de arena de relaves, un tipo especial de presa de relleno hidraulico. Esto porque este tipo de presas se deben construir durante un periodo largo de tiempo y debido al bajo costo de la arena disponible de los relaves. Este articulo analiza el comportamiento de presas de relave en Chile, uno de los paises mas activos sismicamente en el mundo. Se discute el diseno y construccion de presas de relaves, asi como tambien el efecto de drenes de gravas y materiales de filtro en el comportamiento geotecnico de arenas de relaves. Se enfatiza la importancia de la fase operacional porque esta fase puede durar muchos anos y ser determinante en el comportamiento final de las presas de relaves. Finalmente, se dan recomendaciones para mitigar los riesgos a lo largo del ciclo de vida completa de las presas y se considera tambien el efecto de la permeabilidad y contenido de finos ademas de la resistencia drenada y no drenada de las arenas de relaves.

Evaluation of static and dynamic properties of sand–fines mixtures through the state and equivalent state parameters

The results of an experimental investigation on sands with low plastic fines content are presented. Specimens with a low plastic fines content of 0%, 15%, 30%, 40%, 50% and 60% by weight were tested in drained and undrained triaxial compression tests. The soil specimens were tested under three different categories: (1) at a constant void ratio index; (2) at the same peak deviator stress in a triaxial test; and (3) at a constant relative density. By a combination with our published experimental data in recent years, the critical state line and various state parameters have been proposed and discussed for a further understanding the behavior of sand–fines mixtures. Results indicated that a unique critical line was obtained from drained and undrained triaxial compression tests for each fines content. The effects of fines content on critical state line (CSL) were recognized and discussed. In addition, the results revealed that normalized peak undrained shear stress, cyclic resistance ratio, and compression index were found to be a good correlation with state parameter Ψ as well as equivalent state parameter Ψ*. An increasing state parameter decreased the normalized peak undrained shear stress, and cyclic resistance ratio; however, the compression index increased with an increase in state parameter. Finally, there were no correlations such as the coefficient of consolidation–state parameter and maximum shear modulus–state parameter due to the different testing condition.

EFFECT OF FINES ON LIQUEFACTION USING SHAKE TABLE TEST

Earthquake is one of the most disastrous natural calamities resulting into considerable damages. One of the most detrimental effects caused due to earthquake is liquefaction. This paper deals with experimental investigation of effects of fines content on liquefaction behavior using shake table test. A test program consisted of total 19 tests conducted on saturated cohesionless sand with varying amount of non-plastic silt. The behavior of such silty sand in the relative density range 30 to 60% has been studied by subjecting the specimens to a specific acceleration of 0.54g. Effect of silt content and the relative density on generation of pore pressure and thereby initiation of liquefaction has been studied. The results obtained from the present study showed that cyclic stress ratio (CSR) values decrease with the increase in fines content for lower relative densities. Delay in development of pore pressure is observed with the increasing fines content. This indicates that higher silt contents at higher densities offer better resistance to liquefaction. Further, for lower densities and lesser silt contents liquefaction occurred at pore pressure ratio even less than one. The trend observed for CSR and relative density is similar when compared with triaxial test reported in literature. The points where liquefaction has occurred in the field, when checked in the present study, they lie in ‘YES’ zone of liquefaction.

Effect of Fines Type and Content of Sand on Correlation Between Shear Wave Velocity and Liquefaction Resistance

The use of shear wave velocity (V s) measurements as an in situ test for evaluation of liquefaction potential has increased substantially due to its advantages. Relatively large numbers of studies have been performed to establish the correlation between V s and liquefaction resistance (CRR) of clean sands. Usually, natural sands contain silt and/or clay, and previous studies have shown that both the amount of fines and their nature influence the values of CRR as well as V s. Therefore, the CRR–V s correlations may also be affected by fines content and type of sandy soils. However, effect of fines content and especially fines type of sandy soils on the correlation between V s and CRR is inadequately addressed in the literature. In this study, cyclic triaxial and bender element tests were conducted on samples of sand containing various amounts of different types of fines, and the effects of fines on the values of CRR and V s are investigated. The results show that G 0 and CRR reduce even when small amounts of fines are added to sand. Therefore, use of plasticity index (PI) of the fines fraction is better than the PI of the overall soil when trying to assess the effects of fines. Using obtained experimental data as well as the established semiempirical CRR–V s relationship, the CRR–V s correlation was developed for all the tested soils, and the effect of fines type on the correlation is also examined. Based on the results obtained in this study, CRR–V s correlation is affected by both the amount and the plasticity of the fines present in the sand, and this correlation is soil specific.

Force transmission and soil fabric of binary granular mixtures

The effect of fines content on force transmission and fabric development of gap-graded mixtures under triaxial compression has been studied using the discrete-element method. Results were used to define load-bearing soil fabrics where the relative contributions of coarse and fine components are explicitly quantified in terms of force transmission. Comparison with previous findings suggests that lower particle size ratios result in higher interaction between components. A potential for instability was detected for underfilled fabrics in agreement with recent findings. It was also found that the threshold fines content provides an accurate macroscopic estimation of the transition between underfilled and overfilled fabrics.

Effect of Fines on Behavior of Braced Excavation in Sand: Experimental and Numerical Study

AbstractIn this paper, the effect of fine content in the retained sandy soil on the behavior of braced excavation has been studied using experimental and numerical models in terms of four design factors: strut force, bending moment developed in the wall, lateral deflection of the wall, and vertical displacement of the ground surface. In the experiments, the fine content of the soil has been estimated as 0, 5, and 10% (by weight). However, the numerical study has been conducted for different fine contents varying from 0 to 50% (by weight). The parametric study with 20 m depth of retaining wall; position of struts at 2, 7, 12, and 17 m below ground level; wall thickness and embedment depth as 6 and 80% of depth of excavation; and stiffness of support members as 5×105kN/m/m confirms that the values of the four design factors (strut force, wall moment, lateral wall defection, ground deflection, and net earth pressure acting on the wall) increase with the increase in fine content in the retained soil. It is al...

Effect of fine content on the pullout resistance mechanism of bearing reinforcement embedded in cohesive–frictional soils

Bearing reinforcement, which is composed of a longitudinal member (steel deformed bar) and transverse (bearing) members (a set of equal angle steel), has been established as an effective earth reinforcement material. The equation for estimating the pullout resistance of this reinforcement in coarse-grained soils has been previously developed. The usage of locally available soils as a backfill is particularly cost effective for construction sites where there is a lack of available quality materials. The pullout resistance mechanism of the bearing reinforcement embedded in cohesive–frictional soils with various fine contents is presented in this paper. The total pullout resistance is the sum of the pullout friction and bearing resistances. The pullout friction resistance is approximated from soil shear strength and interaction factor α, which is linearly related to fine content. The bearing pullout resistance of a single isolated transverse member can be approximated from the modified punching shear mechanism where the failure plane angle, β is primarily dependent upon fine content. The relationship between β and fine content is expressed by a polynomial function. The β value of π/2 is suggested for fine contents less than 45%. The transverse member interference is classified into three zones, depending upon spacing and dimension of transverse member, S/B ratio. The larger softened region caused by transverse member interference develops with smaller fine content. Based on a critical analysis of the test results, the pullout resistance equations for bearing reinforcement with different normal stresses, dimensions and spacing of transverse members embedded in different cohesive–frictional soils compacted at optimum point (optimum water content and maximum dry unit weight) are developed in term of total strength parameters. The application of the proposed equations are finally illustrated and verified. The developed equations is useful for the internal stability analysis of bearing reinforcement earth walls during construction and at the end of construction.

A constitutive model for coal-fouled ballast capturing the effects of particle degradation

Rail tracks undergo degradation owing to particle breakage and fouling of ballast by various fines including coal and subgrade soil. As the ballast becomes fouled, its strength and drainage capacity are compromised, sometimes resulting in differential settlement and reduced track stability. This paper demonstrates a continuum mechanics based framework to evaluate the detrimental effect of fines on the strength, deformation and degradation of coal-fouled ballast under monotonic loading. An elastoplastic constitutive model that considers the effect of fines content and energy consumption associated with particle breakage during shearing is presented. This multiphase constitutive model is developed within a critical state framework based on a kinematic-type yield locus and a modified stress-dilatancy approach. A general formulation for the rate of ballast breakage and coal particle breakage during triaxial shearing is presented and incorporated into the plastic flow rule to accurately predict the stress–strain response of coal-fouled ballast at various confining pressures. The behaviour of ballast at various levels of fouling is analysed and validated by experimental data.

Geotechnical Evaluation of Fines Content Effect in Gravelly Sand Replacement Soil

Abstract The compacted soil replacement procedure has been widely used in Egypt for Overcoming the unfavorable actions of some problematic soils, such as expansive, Collapsing soils and ground fill. Compaction of the replacement soil is necessary for stabilizing it and improving its performance. The supporting capacity of a replacement soil increases with the increase of its dry density. Therefore, the density of the replacement layer is the major factor controlling its behavior under the effect if external stresses. Compacted sand and gravelly sand are preferred materials when used for soil replacement. They tend to have better engineering properties, if they are placed according to the standard specifications. Gravelly-sand soil, which consists of gravel, sand and fines, is widely used as replacement soil in the field. The effect of fines content on possibly achieved density of such soil is experimentally investigated. Another experimental stage of the effect of fines on the bearing capacity of circular footings on gravelly-sand with different percentages of fines was performed. It was found that a fines content of 10 % gives highest dry density, if the soil is compacted according to modified proctor specifications and with the addition of fines, settlement increases and the ultimate bearing carrying capacity decreases.

Strength and Dilatancy of Silty Sand

AbstractFines content can have a great influence on the mechanical behavior of sand. The effect of fines content has not been taken into account in most of the strength-dilatancy relationships for sand. An attempt was made in this paper to account for the influence of fines content on the strength-dilatancy relationship of silty sands. The test data on Ottawa sands with nonplastic fines were reanalyzed to examine the strength and dilatancy relationship for silty sand with different fines contents. The ratio of excess angle (which is the difference between the peak friction angle and the critical state friction angle) to the relative dilatancy index was found to be a function of fines content. Furthermore, a strength-dilatancy relationship was also modified to account for the influence of confining pressure on the strength-dilatancy relationship of silt sands.

Effects of fines content on packing density of fine aggregate in concrete

The fines content (particles finer than 75μm) in aggregate has substantial effects on the performance of concrete. Since the fines content has large surface area that would increase the water demand, maximum limits are often imposed. However, the fines content would also fill into the voids between larger particles to increase the packing density and thus reduce the volume of voids to be filled with cement paste. Hence, the fines content is not entirely undesirable and it has been suggested to raise the limits on the fines content. Somehow, due to measurement difficulties, the effects of fines content on the packing density are still not well understood. Herein, the packing density of fine aggregate with varying fines content was measured using both the dry and wet packing methods. It was found that under wet condition, the highest packing density generally occurs at a fines content of about 15%.

Effects of Fines Content on Hydraulic Conductivity and Shear Strength of Granular Structural Backfill

For cast-in-place abutments and retaining walls, structural backfill is preferred to be free-draining, which generally implies less than 5% fines content. This fines content is expected to eliminate the need to design for hydrostatic pressures. The availability of high-quality structural backfill with naturally low fines content is declining. This situation warrants an evaluation of whether granular backfill materials with greater than 5% fines content could be successfully used in practice. Flexible wall, hydraulic conductivity tests on a granular structural backfill with 0%, 5%, 10%, 15%, 20%, and 25% nonplastic fines content were conducted at 41, 83, and 124 kPa (6, 12, and 18 psi) confining pressures followed by consolidated drained triaxial compression tests for obtaining associated drained shear strength parameters of these gradations. The 15.2-cm (6-in.) diameter specimens were prepared at optimum moisture content and 95% of maximum standard Proctor density. To enable a comparison with respect to modified Proctor maximum densities, modified Proctor tests were also performed for all base soil–fines content mixtures. The experimental results were compared with relevant studies found in the literature. This research indicates that a nonplastic fines content up to 10% may be justified in structural backfill specifications for retaining walls and abutments.

Investigation of the hydro-mechanical behaviour of fouled ballast

In this study, a fouled ballast taken from the site of Senissiat, France, was investigated. For the hydraulic behaviour, a large-scale cell was developed allowing drainage and evaporation tests to be carried out with monitoring of both suction and volumetric water content at various positions of the sample. It was observed that the hydraulic conductivity of fouled ballast is decreasing with suction increase, as for common unsaturated soils. The effect of fines content was found to be negligible. For the mechanical behaviour, both monotonic and cyclic triaxial tests were carried out using a large-scale triaxial cell. Various water contents were considered. The results were interpreted in terms of shear strength and permanent axial strain. It appeared that the water content is an important factor to be accounted for since any increase of water content or degree of saturation significantly decreases the shear strength and increases the permanent strain. Constitutive modelling has been attempted based on the experimental results. The model in its current state is capable of describing the effects of stress level, cycle number and water content.

Effect of fines content and void ratio on the saturated hydraulic conductivity and undrained shear strength of sand–silt mixtures

The hydraulic conductivity represents an important indicator parameter in the generation and redistribution of excess pore pressure of sand–silt mixture soil deposits during earthquakes. This paper aims to determine the relationship between the undrained shear strength (liquefaction resistance) and the saturated hydraulic conductivity of the sand–silt mixtures and how much they are affected by the percentage of low plastic fines (finer than 0.074 mm) and void ratio of the soil. The results of flexible wall permeameter and undrained monotonic triaxial tests carried out on samples reconstituted from Chlef river sand with 0, 10, 20, 30, 40, and 50 % non-plastic silt at an effective confining pressure of 100 kPa and two initial relative densities (D r = 20, 91 %) are presented and discussed. It was found that the undrained shear strength (liquefaction resistance) can be correlated to the fines content, intergranular void ratio and saturated hydraulic conductivity. The results obtained from this study reveal that the saturated hydraulic conductivity (k sat) of the sand mixed with 50 % low plastic fines can be, in average, four orders of magnitude smaller than that of the clean sand. The results show also that the global void ratio could not be used as a pertinent parameter to explain the undrained shear strength and saturated hydraulic conductivity response of the sand–silt mixtures.

The Effects of Fines on Post Liquefaction Strength and Deformation Characteristics of Sand

This study has been carried out to determine how the fines content affects the post liquefaction strength and deformation characteristics of sand. With the GDS dynamic triaxial system, a series of monotonic undrained compression tests of the sand after liquefaction with variation in fines content from 0 to 40% were conducted, and effects of fines content on the post liquefaction strength and deformation characteristics of sand were analyzed. Results show that with the addition of fines up to a fines content of 30%, the stress-strain curve moves downward and axial strain at low intensive stage is increased, beyond this critical value of fines content the trend is reversed. However, shear strength of post-liquefied sand first decreases with increasing fines content, and beyond the critical value of fines content it increases with increasing fines content at the strength recovery stage when are subjected to monotonic loading. At the same time, the strength recovery rate decreases firstly and then increases with the increasing fines content.

Response to Discussion by Wong Hong Yau on ‘Effect of Fines Content of Completely Decomposed Granite on Slope Stability under Rainfall Infiltration’

Response to Discussion by Wong Hong Yau on ‘<i>Effect of Fines Content of Completely Decomposed Granite on Slope Stability under Rainfall Infiltration</i>’

Discussion on ‘Effect of Fines Content of Completely Decomposed Granite on Slope Stability under Rainfall Infiltration’

Discussion on <i>‘Effect of Fines Content of Completely Decomposed Granite on Slope Stability under Rainfall Infiltration’</i>

Effect of Soil Parameters on Elastic Characteristics of Subgrade Materials

AbstractIn this paper, state-dependent elastic characteristics of granular subgrade materials were investigated, assuming various field conditions. For this purpose, a series of resonant column tests were conducted. The test materials were cohesionless soils consisting of clean and silty sands with different fines contents. The effects of moisture content, overconsolidation ratio, relative density, and confining stress on the elastic modulus were analyzed. From the test results, it was observed that the initial shear modulus, G0, decreases with increasing moisture content because of reduced particle contact friction. Higher fines content produced a more pronounced modulus reduction at the same moisture content. It was also found that the effect of fines content on G0 becomes smaller as the relative density and confining stress increase. These results indicate that the moisture effect on G0 is important at shallow depths such as subgrade layers. A modulus reduction factor was proposed, which can reflect th...

Assessment of silty sand liquefaction potential using hollow torsional tests—An energy approach

This research presents an investigation into the effect of fines content on the cyclic resistance ratio (CRR), dissipated energy up to liquefaction occurrence and excess pore water pressure generation of Firouzkooh silty sands from the shear stress and strain energy viewpoint. Sixty stress-controlled cyclic hollow torsional tests were conducted to directly measure excess pore water pressure generation at different levels of cyclic stress ratio (CSR). The specimens were tested under three different confining pressures ( σ 3 ′ = 60 , 120 , and 240 kPa ), and different fines content at a constant relative density ( D r=60%). The observed relations between dissipated strain energy per volume and different parameters such as pore water pressure are demonstrated. Based on the experimental evidence presented in this study, it can be concluded that the amount of cumulative dissipated energy, required for liquefaction occurrence, is independent of CSR for the specimens with constant relative density and confining pressure. On the other hand, effective confining pressure and fines content have strong effects on the accumulated strain energy.