Final Void Ratio Research Articles

Predicting Swell in Clay-Sand Mixtures Used in Liners

A method to predict the swellability of clay-sand mixtures is proposed. This model is a modified form of the Studds (1997) prediction model for clay-sand mixtures. The new proposed model uses the laboratory fall cone penetration technique to produce a characterization chart. This chart presents slope levels that can be used to obtain an equation for the final clay void ratio versus the vertical effective stress for clays. The porosity of the clay-sand mixtures was worked out based on a correction factor obtained from compression and porosity measurements in the laboratory. The porosity of the mixture was merged into the clay profile equation to compute the final clay void ratio at a specified stress level, which made it possible to predict the swelling behavior for different and variable stress levels. The swellability slope was obtained using fall cone tests conducted on the fine portion. Mixtures of kaolinite and bentonite were introduced to represent soils with different swell potentials. The fall cone measurements of a few points can be used to establish the swellability relationships for natural clay. Merging fall cone points with the swellability slope chart can define the profile of the vertical effective stress versus the clay void ratio.

Effect of temperature on the compressibility behavior of glass fiber-bentonite mixture

Effect of temperature on the compressibility behavior of glass fiber-bentonite mixture

Effect of ceramic waste powder content and sodium hydroxide molarity on the residual mechanical strength of alkali-activated mortars

In the study, the effects of various ceramic waste powder (CWP) additions (5, 10, and 15%) and sodium hydroxide (SH) molarity (8 M and 16 M) on the residual mechanical properties of different ambient-cured alkali-activated mortar (AAM) samples were investigated under the elevated temperatures (300, 600, and 900 °C) and freeze-thaw (100 cycles) attacks. The fresh (flowability, initial and final setting time, water absorption, and void ratio) and hardened (compressive and flexural strength, ultrasonic pulse velocity, and weight loss) state performances were evaluated. Also, XRD and SEM analyses were carried out. The findings pointed out that flowability enhanced up to 15% of CWP replacements. The initial and final setting time was reduced with higher molarity, while improved with further CWP incorporations. The water absorption and void ratio decreased with higher CWP incorporations and SH molarity. Moreover, mechanical strengths increased with time, which were found to be more with a higher CWP replacement ratio and SH molarity. After elevated temperature, the average compressive strength losses were about 50% at 600 °C and 85% at 900 °C, while average flexural strength losses were about 70% at 600 °C and 85% at 900 °C. Meanwhile, similar residual compressive strengths were obtained at elevated temperatures, irrespective of the SH molarity and CWP incorporations. However, both CWP incorporation and high SH molarity slightly enhanced the residual flexural strengths. After freeze-thaw attacks, an average of 23% compressive strength loss and 29% flexural strength loss was obtained, and almost similar mechanical strength losses were observed with varying SH molarity and CWP replacement ratio.

Field Test Verification and Consolidation Model of a Sand-Doped Soft Soil Foundation with Vacuum Pressure

In this study, a field test on the consolidation of sand-doped improved soft soil under surcharge-vacuum preloading is carried out. By analyzing the vacuum pressure transmission efficiency, the settlement rate, and the dissipation rule of excess pore-water pressure of sand-doped and original soft soil foundation in the consolidation process and comparing the indices of vane shear strength, water content, and void ratio before and after consolidation, the technical superiority and reinforcement effect of the sand mixing method for improving soft soil are comprehensively evaluated. Considering the fact that the vacuum pressure decreases linearly along the depth and the surcharge preloading is applied linearly, an assumption of equal volumetric strain is introduced to reflect the lateral deformation, and an axisymmetric nonlinear radial consolidation model of sand-doped soft soil is established. The model accuracy is verified by model degradation research and a field test. The results show that the sand-doped method (20% sand content) can improve the transmission efficiency of vacuum pressure, reduce the loss of vacuum pressure along the prefabricated vertical drains, accelerate the dissipation rate of excess pore-water pressure, increase the final settlement and shear strength, reduce the final void ratio and water content, and improve the reinforcement effect of deep soil. A nonlinear consolidation solution of the sand-doped soil with linear surcharge preloading considering the actual negative boundary conditions can reflect the consolidation behavior more accurately. If lateral deformation and linear surcharge preloading are not considered, the consolidation rate of soil will be overestimated.

Particle Size Effects on the Volumetric Shrinkage of Bentonite–Sand Mixtures

Tests were conducted on bentonite–silica fume mixtures (BSFMs) to determine how particle size affects the volumetric shrinkage of bentonite–sand mixtures (BSMs) used as hydraulic barriers in waste disposal facilities. Free desiccation tests, liquid limit tests, plastic limit tests, and direct shear tests were conducted to compare the soil shrinkage characteristic curves, shrinkage limits, plasticity, and shear strength of BSFMs to that of the commonly used bentonite–standard sand mixtures (BSSMs) at 30% sand percentage. BSFMs exhibited higher air entry values (up to 55.9% higher), shrinkage limits (up to 14.6% higher), final void ratio (up to 43.6% higher), peak shear strength (up to 115% higher), and a smaller percentage of volumetric shrinkage (10.8%) than BSSMs due to the particle contact and constrained particle movement. The liquid and plastic limits of BSFMs, in contrast, were also higher (up to 99.2% and 27.1%) than that of BSSMs. Particle size plays a critical role in controlling the shrinkage limits of BSMs compared to clay fractions.

Variability in the Solid Particle Density and Its Influence on the Corresponding Void Ratio and Dry Density: A Case Study Conducted on the MBT Reject Waste Stream from the MBT Plant in Marišćina, Croatia

In this study, a functional relationship between the solid particle density (ρs), void ratio e, and dry density (ρd) of mechanically and biologically treated (MBT) municipal solid waste (MSW) was examined. In total, 60 waste specimens were tested with an air pycnometer device and corresponding triplets (e, ρd,and ρs) of values were obtained. In addition, a long-term oedometer test with an allowed decomposition process was also conducted. Based on the obtained results, the variability in the solid particle density caused by heterogeneity and decomposition, as well as its influence on the corresponding void ratio and dry density values, were critically evaluated. The obtained results showed that the variability in the solid particle density caused by waste heterogeneity had a significant influence on the initial void ratio value. Furthermore, the obtained results also showed that the change in the solid particle density, caused by the degradation process, had a significant impact on the final void ratio and dry density values. In addition, an empirical relationship, ρd=fe, was proposed. The proposed function allows a landfill operator to establish the corresponding dry density at an arbitrary chosen void ratio, and vice versa, without having the exact knowledge of the corresponding solid particle density value.

Experimental study of the shrinkage behavior of cemented paste backfill

Abstract Cemented paste backfill (CPB) is largely used in underground mine stopes worldwide. When a CPB is placed in a stope, an important task is to estimate the settlement associated with the shrinkage and self-weight consolidation of the CPB. This is closely related to the volume management to ensure the stability of barricades and tight contacts between the backfill and stope roof. Over the years, shrinkage studies were mostly performed on fine-grained soils (silts and clays), with only a few publications on the shrinkage behavior of uncemented tailings. No study has been published on the shrinkage behavior of CPB. To fill this gap, a series of shrinkage tests has been conducted on CPB with different cement contents, including zero cement content (uncemented paste backfill, uCPB). The results show that the shrinkage response of CPB is very different from that of uCPB. At a given initial water content, CPB exhibits a shorter normal shrinkage stage than uCPB. The unsaturation onset water content and void ratio, shrinkage limit and final void ratio of CPB are generally higher than those of uCPB. At a given cement content, the shrinkage behaviors of CPB and uCPB are significantly influenced by the initial water content.

One-dimensional (1D) immediate compression and creep in large particle sized Tire Derived Aggregate (TDA) for leachate collection and removal systems (LCRS)

Potential cost savings and environmental benefits are two reasons for using Tire Derived Aggregate (TDA) in place of gravel, or drainage geosynthetics, as drainage material in leachate collection and removal systems (LCRS) of waste disposal sites. As a polymeric material, TDA is expected to undergo both immediate and time dependent compression (creep) under sustained compressive loading, and these may influence performance. The response of large particle sized TDA – TDA with individual particle sizes generally greater than 50 mm – to large compressive loads up to 300 kPa was studied to assess void volume reduction from the individual and combined effects of immediate compression and creep. The results showed void volume reduction from creep, but this was considerably less than that from the immediate compression. Isotropic solid volume compression in individual TDA particles was found to be negligible. The final void ratio appeared to be dependent on the initial void ratio, as well as on the applied load, but did not appear to be dependent on the loading rate or to be influenced by elevated temperatures (up to 58 C). Presented here are the details of the study, findings and implications for practice.

Studying the Geotechnical Properties of Clayey Soil Contaminated by Kerosene

This study focuses on investigating the impacts of kerosene on the physical, mechanical, and chemical characteristics of clay soil. The soils specimens are contaminated artificially with six ratios of kerosene (5, 10, 20, 30, 40, and 50) % calculated according to the dry weight of soil. The artificial contamination includes air drying of the disturbed soil, then placed in plastic containers and mixed with the field water content and the specified concentration of kerosene to ensure getting homogenous contaminated soil specimens. The contaminated soil specimens left for 30 days in plastic containers covered by nylon sheets to control the water content and prevent volatility of contaminant. The results of tests proved that different ratios of kerosene have different impacts on the engineering and chemical characteristics of soil specimens. The specific gravity, percentages of fine particles, optimum water content, the initial and final void ratio, coefficient of consolidation, swelling index, permeability, the undrained shear strength, effective shear strength parameters, and the rate of reduction of initial pore water pressure are reduced significantly with increasing the content of kerosene in soil. Generally, the concentration of kerosene less than 10% has slight impacts on the studied characteristics of soil specimens.

Evaporation and shrinkage processes of compacted bentonite-sand mixtures

The deterioration of compacted bentonite-sand mixtures (CBSMs) after suffering desiccation increases the hydraulic conductivity of clay barriers, posing risks to the environment. This work compressed bentonite-sand mixtures (BSMs) to various dry densities in order to conduct the free-drying tests, focusing on the evaporation and shrinkage processes. The compaction constrained the permeability of the mixtures and resulted in the delay in evaporation and shrinkage of the CBSMs’ internal parts (compared to their external parts). Subsequently, the secondary shrinkage occurred (i.e., the smaller volumetric shrinkage after the shrinkage limit reached). Compaction constrained the plate-like smectite particles in being propped up and led them to orientate. This structure reinforced the CBSMs’ shrinkage property and contributed to their lower air entry value, shrinkage limit, and final void ratio. During the design and maintenance of compacted clay barriers, secondary shrinkage and the reinforced shrinkage property are proposed to be taken into consideration.

Experimental Investigation of Consolidation Properties of Nano-Bentonite Mixed Clayey Soil

As a new soil improvement method, adding nano-bentonite can enhance the engineering properties of soil. To study the stabilization effect of nano-bentonite on soil consolidation properties, a series of one-dimensional odometer tests were conducted on a clayey soil with different nano-bentonite mixing contents (i.e., 0.5%, 1%, 1.5%, and 2%). The effects of nano-bentonite on the coefficient of consolidation and permeability of the test soil were analyzed. The results show that adding a certain amount of nano-bentonite does not significantly affect the original consolidation characteristics of soil samples, but displays a notable effect on accelerating water drainage. Among all the soil samples, when the nano-bentonite mixing content is 0.5%, the final compression amount is the largest and the final void ratio is the smallest. The coefficients of consolidation and permeability increase with increasing nano-bentonite mixing content under high stress state. The test results indicate that nano-bentonite can facilitate internal cementation of soil particles, which effectively reduces the compressibility of clayey soil.

Prediction Of Compression Index For Lateritic Soil Using Transformed Variable

The information on the compression index of a soil is vital in geotechnical design, but its determination is expensive and time consuming. Most models relating compression index and basic soil properties are usually based on soil types. This work seeks to develop a model relationship between compression index and basic soil properties for lateritic soils. Selective transformation method which involves testing some general functional forms, to choose the model that best characterizes the data relationship was adopted. Secondary soil data were obtained from existing literature on soil properties of lateritic soils. Liquid limit was adopted as the independent variable in the modeling exercise as it is easily obtained in comparison to clay content and final void ratio. The square root transformation model has both constant and coefficient terms significant at 5% level of confidence. The model performed better than other empirical models using statistical criteria. It is believed that the model will assist greatly in construction activities in areas where consolidation test equipment and trained manpower are unavailable.

Geotechnical properties of polymer-amended tailings solvent recovery unit (TSRU) oil sands tailings

Fine tailings from the tailings solvent recovery unit (TSRU) in the Athabasca oil sands are known to contain a relatively high pyrite content and a high residual hydrocarbon content, which may alter their geotechnical properties. Little is known about TSRU tailings properties and therefore the potential for subaerial deposition. The goal of this study was to investigate the geotechnical properties of untreated, polymer-amended, and sand-mixed TSRU tailings to provide information for the consideration of subaerial deposition and increase the general knowledge about these unique tailings. The polymer-amended tailings had more desirable properties for subaerial deposition, including a lower final void ratio, less energy required to desaturate, and higher compressibility, when compared with the untreated tailings. The sand-mixed samples enhanced these properties, but may pose issues for transportation. The mineralogy indicated that the polymer-amended TSRU tailings have a high-enough pyrite content for acid generation, which may pose environmental issues for subaerial deposition. Overall, TSRU tailings exhibited different geotechnical properties when compared with the well-studied mature fine tailings, highlighting the need for further studies to provide information for the management of TSRU tailings.

Effects of wetting-drying cycles on the air permeability of compacted Téguline clay

Due to their low permeability and self-sealing ability, compacted clays are often considered as barrier materials in waste disposal. In most disposal cases these materials are exposed to atmosphere and thus subjected to wetting-drying cycles. As a result, their microstructures might significantly change and sometimes cracks can occur, giving rise to changes in hydro-mechanical properties. It is expected that this microstructure change can be evidenced through changes in air permeability since any growth of micro-cracks can greatly affect the air permeability. In this study, the air permeability evolution of Téguline clay compacted at 12.7% and 16.0% water content during wetting-drying was investigated. The results show that the final water content, void ratio and degree of saturation decreased with the increase of wetting-drying cycles. Cracks occurred in the radial direction on the sample surface rather than in the axial direction after 4–5 wetting-drying cycles. The coefficient of air permeability of the compacted samples is larger than those of the samples subjected to wetting-drying cycles. It also appears that the coefficient of air permeability increases with wetting-drying cycles and the initial water content has insignificant effects on the wetting-drying behaviour and air permeability characteristics. Furthermore, the coefficient of air permeability in the axial direction is larger than the one in the radial direction after the initial 2 wetting-drying cycles, suggesting an anisotropic behaviour with larger shrinkage in the axial direction. These findings show clearly that the effects of wetting-drying cycles on soil microstructure can be effectively investigated through air permeability measurements.

Shear wave velocity of sands subject to large strain triaxial loading

Shear wave velocities of three selected sandy soils subject to drained triaxial compression test were continuously measured using the bender elements. The shear wave velocity during isotropic compression, as widely recognized, increased as confining pressure increased and they were correlated well. However, during drained shearing, the mean effective stress could no further provide a suitable correlation. The shear wave velocity during this stage was almost constant with respect to the mean effective stress. The vertical stress was found to be more favorable at this stage (since confining stress was kept constant). When sample was attained its peak stress, the shear wave velocity reduced and deviated from the previously existed trend line. This was probably caused by the non-uniformity induced by the formation of shear band. Subsequently, void ratios computed based on external measurements could not provide reasonable fitting to the initial stage of post-peak shear wave velocity. At very large strain levels after shear band formation, the digital images revealed that sample may internally re-arrange itself to be in a more uniform loose stage. This final stage void ratio estimated based on the proposed correlation derived during pre-peak state was close to the value of the maximum void ratio.

PREDICTION OF SOIL SETTLEMENT BASED ON CONSTANT PLASTIC INDEX METHOD

The development of Constant Plastic Index (CPI) method is an approach model based on the theory of consolidation. The objective behind the development CPI method is to predicts critical state settlement whereby CPI is to achieved secondary settlement and reduced time of consolidation. The development CPI has been derived base on the ultimate soil settlement where soils are classified accordingly using initial void ratio, final void ratio and thickness of soil layers. The linear and non linear soil was developed by the relationship between an exponential stress - void ratio and the parabolic permeability - void ratio. The external forces is normally consolidated soil layers and develop Stratum index factor (SIF) and Void ratio function(VRF) which is composed of such a soil varies non- linearly in deposition. Development of CPI will used to predicts critical state settlement, using Eurelian method By combination of these elements, the Potential Instability of settlement was develop and integrate CS- Rating makes concerted effort to produce CS- statement guidelines and better design strategy for geo -mechanics engineer to involve in soil development settlement analysis. Finally, modification of CPI method can be determine soil settlement by using CS- Rating. © 2016, Int. J. of GEOMATE.

Experimental Characterization of the Shrinkage and Water Retention Behaviour of Tailings from Hard Rock Mines

Mining of hard rock ore deposits produces large amounts of tailings. The safe disposal and management of these tailings require an extensive characterization that should include their drying and desaturation behaviour. Desiccation tests have been performed to characterize the shrinkage response of low plasticity tailings having an initially loose state. The testing procedure developed for this purpose is briefly described here. The main shrinkage tests results are then presented. The experimental data are compared with those obtained from water retention tests performed in a pressure plate with volume change measurements. These two types of results are combined to define unsaturated (drying and shrinkage) relationships in six complementary planes that include the volumetric shrinkage curve and the water retention curve. Specific material characteristics are then determined, including the shrinkage limit wS, final void ratio ef, and air entry value ψa. Additional tests were also performed to define critical parameters at the initiation of cracking in terms of suction ψ, water content w, and degree of saturation Sr. The original results presented here indicate that the onset of desaturation is closely linked with the end of volumetric straining and with crack initiation. Results also show that the shrinkage limit wS is a function of the specimen initial water content w0. Other related characteristics are also presented and discussed.

Experimental framework for evaluating the mechanical behavior of dry and wet crushable granular materials based on the particle breakage ratio

It has been widely shown that particle crushing increases the compressibility of granular materials. For a particular crushable material and given test conditions, an empirical relation can be established between the breakage ratio and the plastic work. Along these lines, constitutive models have been developed based on the effect of grading evolution during crushing. In parallel, due to corrosive attacks of the humid environment at the tip of microcracks within solid grains, the mechanical behavior of crushable granular materials depends also on the water content: the higher the material humidity, the higher the particle crushing. However, the experimental data on the relation between loading–wetting conditions and the breakage ratio are still quite scarce. In this paper, we present experimental results on crushable sand to study the effect of flooding under isotropic, oedometric, and triaxial stress paths. The main objective of this study is to obtain a consistent framework for the effect of water based on the breakage ratio. Our results have shown that, for a given initial density and stress path, the dry material after flooding reaches the equivalent behavior of the initially wetted material in terms of compression curve, particle crushing, and creep compressibility index, regardless of the point of flooding. Moreover, the relation between the breakage ratio and the final void ratio is unique and depends neither on the stress path, the water content, the point of flooding, nor the loading condition (time of creep or relaxation), but exclusively on the initial density and on intrinsic parameters. These findings could improve the prediction of the effect of water and time on the mechanical response of crushable granular materials through constitutive models based on grading evolution.

Compressibility and Durability Characteristics of Lime Treated Expansive Semiarid Soils

Abstract The current study evaluates the role of lime and the curing period on the compressibility and durability characteristics of two expansive semiarid soils samples originating from Saudi Arabia. The compressibility behavior of these soil samples was evaluated using a range of loading periods of time. Starting with a minimum practicable loading period of 0.5 h, the loading periods were progressively increased to 1, 2, 4, 8, and 24 h. It has been observed that the addition of lime significantly reduces the compressibility behavior of both the selected soils. The study shows that, for a given consolidation pressure increment, an increase in the duration of loading time produces a moderate increase in the final equilibrium void ratio values. In order to evaluate the durability characteristics, lime leachability tests (amount of lime that is converted into soluble form by dissociation into calcium and hydroxyl ions) were conducted on compacted specimens at varying lime contents on samples cured for 1, 7, 14, and 28 days. Analysis of the soil samples subject to increasing periods of curing time show a considerable decrease in the concentration of calcium. This is due to the transformation of amorphous lime into a stable crystalline form, which leads to the formation of pozzolanic compounds.

Effect of Accelerated Loading on the Compressibility Characteristics of Lime-Treated Semiarid Soils

AbstractDetermination of consolidation properties of compacted lime-treated cohesive clays by the one-dimensional fixed-ring oedometer consolidation method with conventional load increment duration may not be appropriate due to immediate pozzolanic reactions, which occur in the presence of lime. An attempt has thus been made to study the effect of accelerated loading on the compressibility characteristics of two different cohesive clays originating from diversified terrains of Saudi Arabia, before and after treating them with lime. In order to study the extent of improvement on the strength characteristics upon lime treatment, a series of unconfined compression strength tests are also carried out. The effect of lime treatment on the elastic moduli has also been studied. It is observed that, prior to any treatment, the final equilibrium void ratio values increase with the increase in duration of loading for the soils. The addition of lime significantly affects the compressibility behavior of both the soils...