Compaction Curve Research Articles

Static Compaction for Sustainable Geotechnical Solutions: A Comprehensive Study

The objective of this research is to develop an improved uniaxial static compaction method to address the limitations of the traditional Proctor's dynamic approach for soil compaction. This new approach offers reduced labor, enhanced soil density, and increased compactness. The study compares of static soil compaction characteristics with various soil parameters and explores the concept of Equivalent Static Compaction Energy (ESCE). A diverse range of fine-grained soils with varying range of plasticity was investigated, and a significant correlation of compaction parameters attained by static compaction was observed with the corresponding value of static compaction energy, degree of saturation, void ratio, and plastic limit of soil. The research resulted in the creation of constant-energy curves for static compaction, which were compared to dynamic compaction curves from four compaction attempts. From the study, the ESCE corresponding to standard Proctor, reduced standard Proctor, and reduced modified Proctor tests were found to be within the range of 180-340, 155-308, and 532-664 KJ/ m3, respectively. It was also observed for the static compaction method that after reaching the maximum level of compaction, the dry unit weight of the soil specimen remains constant with further increases in compaction energy.

Microstructural analysis of the pore size and volume distribution of bentonite at two different hydraulic states utilizing different drying techniques

Bentonite, which is known as adsorbent expansive clay, is widely used as a nanoparticle in a variety of applications due to its unique microstructure. Analyzing the pore size distribution is crucial for studying its microstructural behavior. Drying techniques and initial moisture content play a significant role in the microstructural changes of clays. This study aimed to investigate how different drying techniques and initial moisture content influence the pore size and volume distribution of bentonite. The results indicate a correlation between drying techniques and hydraulic states with the microstructural changes observed in bentonite. Pore size distribution analysis reveals distinct differences in micro, meso, and macro-pore volumes depending on the employed drying techniques. Conventional drying methods show significant alterations in pore volume distribution for specimens prepared with moisture content from dry and wet of the compaction curve's optimum water content. Conversely, a separate phenomenon is observed for specimens subjected to direct outgassing without prior drying. It is observed that specimens undergoing outgassing at elevated temperatures exhibit almost similar pore volume distributions between dry and wet specimens. Dry specimens exhibit a higher cumulative pore volume and a greater number of macro pores compared to wet specimens when subjected to a specific drying method. Moreover, specimens subjected to outgassed freeze-drying, oven-drying, and air-drying exhibit significant changes in cumulative pore volume distribution compared to those without outgassing treatment. These findings highlight the importance of employing a standardized drying technique to accurately predict the microstructural behavior of bentonite clay and understand its pore-size distribution.

Application of hybrid modeling to predict California bearing ratio of soil

California Bearing Ratio (CBR) is used to assess bearing capacity, deformation characteristics of roadbed soil, and base layer material in pavement structure. In general, CBR is often determined by laboratory or in-situ tests. However, it is time- and cost-consuming to conduct this experiment because this test requires cumbersome equipment such as a compressor. In this study, two Artificial Intelligence models are developed, including a simple model (Decision Tree Regression, DT) and a hybrid model (AdaBoost - Decision Tree, AB-DT). Using 214 data samples from Van Don - Mong Cai expressway, Vietnam, 10 input variables of the model were considered namely particle composition (content of gravel (X1), coarse sand (X2), fine sand (X3), silt clay (X4), organic (X5)), Atterberg limits (Liquid limit (X6), Plastic limit (X7), Plastic index (X8)), and compaction curve (optimum water content (X9) and maximum dry density (X10)). The developed models were evaluated by using a variety of statistical indicators, including coefficient of determination (R2­­), Root mean square error (RMSE), and Mean absolute error (MAE). The results show that AB-DT model has higher accuracy than the DT model. Moreover, the SHAP value analysis shows that the variable X10 influences the CBR value the most. Thus, it implies that applying the AB-DT model to effectively predict the CBR of the roadbed soil saves time and money for experiments.

Numerical Analysis of Soil Deformation in Earth Dams Using a Stiffness Variation Technique

Small earth dams have been used since ancient times and are often the main source of water in semi-arid regions. In this particular type of engineering work, soils saturated by water present changes in their mechanical properties (especially in the first filling), which usually cause a simultaneous loss of stiffness and shear strength. In this context, the software UNSTRUCT presents itself as a very useful tool, as it allows calculating the final state of stress x strain for a plane strain state, using the Finite Element Method, both for saturated and unsaturated embankments, considering an elastic model and the effect of suction (and its variation), through a stiffness variation technique. The present research used UNSTRUCT to assess the behavior of the embankment of a hypothetical earth dam, varying the features of its typical cross-section: homogeneity; internal drainage structures; geometry along a longitudinal profile; and the influence of the compaction level. The results showed that the soil responded better to strains for the scenario of better compaction along the dry branch of the compaction curve, as well as with the use of a vertical drainage element. It was also observed that the strains were higher when greater sections considered, which, in a real situation, would cause distortions along the longitudinal profile of the dam. The software UNSTRUCT proved to be efficient in obtaining and visualizing the modeling results, also making it possible to analyze the development of failure over time after the dam was filled. With UNSTRUCT, a more realistic analysis of the behavior of the hypothetical dam – considering factors that are specific to unsaturated soils – was possible. Worth mentioning also that the software allowed the appraisal of multiple changes in the dam’s geometry and parameters.

The Friction-Lubrication Effect and Compaction Characteristics of an SMA Asphalt Mixture under Variable Temperature Conditions.

The aim of this article is to explore the dynamic compaction characteristics of stone mastic asphalt (SMA) and the friction-lubrication effect of internal particles during the superpave gyratory compaction (SGC) process. Firstly, a calculated method for the compaction degree of an asphalt mixture in the gyratory compaction process was defined based on the multiphase granular volume method. Secondly, the gyratory compaction curves of asphalt mixtures were taken based on this calculation method of compaction degree. The dynamic change law of each compaction index (compaction, percentage of air voids, compaction energy index, etc.) during the compaction process was analysed. Finally, the effects of different initial compaction temperatures and different asphalt content on the friction-lubrication effect and compaction characteristics of asphalt mixtures were studied. Research shows that it is reasonable to define the compaction degree by the ratio of the apparent density of the asphalt mixture to the maximum theoretical density of the asphalt mixture during gyratory compaction. The dynamic prediction equations of the compaction degree K and the compaction energy index CEI with the amount of compaction were established, and could effectively predict the compaction degree, percentage of air voids and compaction energy index CEI. The compaction process of the asphalt mixture needed to go through three phases, including periods of rapid growth, slow growth, and stabilisation, and the compaction degree increased by about 10%, 5%, and 1%, in that order, finally tending towards a stable value. The effect of the initial compaction temperature on the forming compaction degree of the asphalt mixture is significant; therefore, it should be controlled strictly in the compaction construction of asphalt mixtures. When the initial compaction temperature of SMA-13 is about 170 °C, the compaction effect is optimal, and the effect of the increase in the amount of compaction at a later stage on the increase in the compaction degree of the asphalt mixture is very low. With the optimal asphalt content, the friction-lubrication effect between the asphalt and aggregate particles is optimal, because it can effectively form an asphalt film, reducing the frictional resistance of the particles moving each other during the compaction process, and the voids will be embedded and filled with each other, finally producing the best compaction result.

Micro-destructive assessment of subgrade compaction quality using ultrasonic pulse velocity

The ultrasonic pulse velocity (UPV) correlates significantly with the density and pore size of subgrade filling materials. This research conducts numerous Proctor and UPV tests to examine how moisture and rock content affect compaction quality. The study measures the changes in UPV across dry density and compaction characteristics. The compacted specimens exhibit distinct microstructures and mechanical properties along the dry and wet sides of the compaction curve, primarily influenced by internal water molecules. The maximum dry density exhibits a positive correlation with the rock content, while the optimal moisture content demonstrates an inverse relationship. As the rock content increases, the relative error of UPV measurement rises. The UPV follows a hump-shaped pattern with the initial moisture content. Three intelligent models are established to forecast dry density. The measure of UPV and PSO-BP-NN model quickly assesses compaction quality.

New Die-Compaction Equations for Powders as a Result of Known Equations Correction: Part 2—Modernization of M Yu Balshin’s Equations

Based on the generalization of M. Yu. Balshin’s well-known equations in the framework of a discrete model of powder compaction process (PCP), two new die-compaction equations for powders have been derived that show the dependence of the compaction pressure p on the relative density ρ of the powder sample. The first equation, p=w(1−ρ0)(n−m)·(ρ−ρ0)n(1−ρ)m, contains, in addition to the initial density ρ0 of the powder in die, three constant parameters—w, n and m. The second equation in the form p=H1−ρ0b−c·ρ−ρ0b1−ρ0c−aρ−ρ0c also takes into account the initial density of the powder and contains four constant parameters H, a, b, and c. The values of the constant parameters in both equations are determined by fitting the theoretical curve according to these equations to the experimental powder compaction curve. The adequacy of the PCP description with these equations has been verified by approximating experimental data on the compaction of various powders, including usual metal powders such as iron, copper, and nickel, highly plastic powders such as tin and lead, a mixture of plastic powder (Ni) with non-plastic powder (Al2O3), nickel-plated alumina powder, as well as powder of a brittle compound, in particular titanium carbide TiC. The proposed equations make it possible to describe PCP with high accuracy, at which the coefficient of determination R2 reaches values from 0.9900 to 0.9999. The four-constant equation provides a very accurate description of PCP from start to finish when the density of the samples stops increasing once the pressure increases to an extremely high level, despite the presence of porosity.

Formulation in a drop - Templated granulation and compaction analysis

Binder-powder interactions were investigated using single drop penetration on pharmaceutically relevant static powder beds. Experimental effects included polymer binder type, binder concentration, drug load, and pre-wetting of the powder bed. These screening effects are relevant to formulations requiring binder granulation, especially challenging formulations having high levels of micronized active ingredients. Interactions were explored using dynamic droplet imaging to measure drop penetration, contact angle, and drop diameter. The structure of the templated granules was analyzed via uniaxial compaction, focusing on the intermediate range of the compaction curve (granule deformation and closure of interstitial porosity in the compact). The results provide guidance in pharmaceutical formulation including the dynamics of granule formation and resulting compaction behavior. The approach is especially useful for early-stage development when only small quantities of drug substance are available.

Physical and Mechanical Properties of All-Solid-Waste-Based Binder-Modified Abandoned Marine Soft Soil

Large quantities of abandoned marine soft soil are generated from coastal engineering which cannot be directly utilized for construction without modification. The utilization of traditional binders to modify abandoned marine soft soil yields materials with favorable mechanical properties and cost efficiency. However, the production of traditional binders like cement leads to environmental pollution. This study uses a CGF all-solid-waste binder (abbreviated as CGF) composed of industrial solid waste materials such as calcium carbide residue (CCR), ground granulated blast furnace slag (GGBS), and fly ash (FA), developed by our research team, for the modification of abandoned marine soft soil (referred to as modified soil). It is noteworthy that the marine soft soil utilized in this study was obtained from the coastal area of Jiaozhou Bay, Qingdao, China. Physical property tests, compaction tests, and unconfined compressive strength (UCS) tests were conducted on the modified soil. The investigation analyzed the effects of binder content, compaction delay time, and curing time on the physical, compaction, and mechanical properties of CGF-modified soil and cement-modified soil. Additionally, microscopic experimental results were integrated to elucidate the mechanical improvement mechanisms of CGF on abandoned marine soft soil. The results show that after modification with binders, the water content of abandoned marine soft soil significantly decreases due to both physical mixing and chemical reactions. With an increase in compaction delay time, the impact of chemical reactions on reducing water content gradually surpasses that of physical mixing, and the plasticity of the modified soil notably modifies. The addition of binders results in an increase in the optimum moisture content and a decrease in the maximum dry density of CGF-modified soil, while the optimum moisture content decreases and the maximum dry density increases for cement-modified soil. Moreover, with an increase in binder content, the compaction curve of CGF-modified soil gradually shifts downward and to the right, while for cement-modified soil, it shifts upward and to the left. Additionally, the maximum dry density of both CGF-modified and cement-modified soils shows a declining trend with the increase in compaction delay time, while the optimum moisture content of CGF-modified soil increases and that of cement-modified soil exhibits a slight decrease. The strength of compacted modified soil is determined by the initial moisture ratio, binder content, compaction delay time, and curing time. The process of CGF modification of marine soft soil in Jiaozhou Bay can be delineated into stages of modified soil formation, formation of compacted modified soil, and curing of compacted modified soil. The modification mechanisms primarily involve the alkali excitation reaction of CGF itself, pozzolanic reaction, ion-exchange reaction, and carbonization reaction. Through quantitative calculations, the carbon footprint and unit strength cost of CGF are both significantly lower than those of cement.

Mechanical Strength and Microstructure of Soft Soil Stabilized with Cement, Lime, and Metakaolin-Based Geopolymer Stabilizers

Soft soils require particular consideration when designing civil engineering structures due to their high compressibility, low shear strength, and permeability. Using chemical additives and geopolymers to stabilize soft soils is a practical approach to improve their engineering properties. The objective of the study was to explore the use of conventional stabilizers alongside metakaolin-based geopolymers. This study also aimed to investigate the compaction characteristics, mechanical strength, shear behavior, and microstructure of stabilized soft soil. The compaction test was carried out using various amounts of cement (6%, 8%, and 10%) and metakaolin (3%, 5%, and 7%) based on the dry weight of the soil. Cement, lime, and geopolymer were added to the soft soil at 15% of the dry weight of the soil for triaxial shear tests. The compaction test results indicated that the stabilized soil exhibited the highest maximum dry density at 8% cement content. Adding metakaolin (MK) to the cement-modified soil decreased the maximum dry density, smoothed the compaction curve, and increased the optimum moisture content. The unconfined compressive strength (UCS) test revealed that cement-stabilized soil had the highest yield stress, while adding MK to the cement-modified soil reduced the yield stress after 7 days of curing. Compared to untreated soft soil, there was a significant increase in shear strength parameters for cement-, metakaolin-, and lime-stabilized soil. This study demonstrates that adding chemical additives and geopolymers can improve the soft soil’s compaction characteristics, mechanical strength, and shear strength parameters.

Overpressure Estimation Based on Velocity Data Analysis in The Subduction Zone of Hyuga-nada at Western Nankai Trough, Japan

Subduction zone is one of the areas which has great potential of earthquake. Nankai trough in Japan is such an area with subduction zone where earthquake records are well archived, despite its complexity. Also, slow earthquakes have been detected in this zone over the past 20 years, so that there are many opportunities to understand the dynamics and deformation in such an active setting. To expand the knowledge about slow earthquake which might occur and trigger a bigger earthquake, this study wants to infer the relationship between overpressure, one of the states and properties of seismogenic zone, and tremors. To carry out this research, 4 velocity models of seismicity line taken in Hyuga-nada are used. And the recorded tremor data placed around the lines came from Yamashita. In correlating the overpressure and tremors, this research is started by converting the Vp model to porosity model using Wyllie equation to predict the pore pressure conditions in the area. Then, the model will be used for fitting the actual data. Assuming there is an exact location following the normal compaction curve as a function of effective stress, it can be used for estimating the overpressure. Overpressure is economized by comparing the observed porosity and the reference curve at the same depth below seafloor. Potential overpressure occurred may be associated with areas of low Vp. The estimated overpressure is in the range of 1.2 to 12 MPa in the depth range of 700 to 4000mbsf. This study also concludes that the overpressure zone overlaps with the tremor location, although the overpressure value estimated is also still uncertain due to the uncertainty of the density value used.

Fractal Analysis on the Crushing Characteristics of Soil-Soft Rock Mixtures under Compaction

Soil-rock mixtures (SRM) are extensively utilized as filling materials in engineering slopes and roadbeds. A comprehensive understanding of the crushing characteristics of SRM during compaction is essential for precisely controlling its mechanical properties, particularly when dealing with SRM comprising soft rock blocks. This study conducted heavy compaction and screening tests to investigate the crushing and compaction behaviors of soil-soft rock mixture (SSRM) with varying coarse particle content (P5 content), the primary focus was primarily on analyzing the double fractal characteristics of coarse and fine particles. The research findings are as follows: with the increase of P5 content, the maximum dry density of SSRM initially rises and then declines, reaching its peak when P5 content is 70%. Soft rock blocks in SSRM exhibit extreme fragility during compaction, the crushing index of coarse particles exhibits a linear increase with the rise in P5 content, whereas the crushing index of fine particles displays a “double peak” characteristic. After compaction, a linear positive correlation is observed between the fractal dimension and the crushing index of coarse and fine particles. With the increase in P5 content, the slope of the relationship curve between the fractal dimension and the crushing index of coarse particles remains relatively constant, while the intercept gradually decreases. Moreover, the fractal dimension of fine particles effectively reflects the compaction characteristics of SSRM, and the relationship between the fractal dimension of fine particles and dry density aligns with the compaction curve of SSRM.

Mechanical Behaviour of Fibre-Reinforced Cemented Iron Ore Tailings Across the Compaction Curve

Mechanical Behaviour of Fibre-Reinforced Cemented Iron Ore Tailings Across the Compaction Curve

Physical and mechanical characteristics of pyroclastic soil for the construction of embankments

In the framework of wider research activity on the physical and mechanical behaviour of volcanic soils, this paper reports the results of some laboratory tests on this type of geomaterial. The background of this research is the need for a construction company to possibly use pyroclastic material excavated along a tunnel profile to build railway embankments included in the design of a new High-Speed Train Line near the city of Naples, Italy. However, according to the standards of the National Italian Railways Company, pyroclastic soils cannot be employed as construction materials unless they are supported by a specific testing program demonstrating their good performance. The pyroclastic soil, which is widespread in the project area, is the product of Mt. Vesuvius volcanic activity. It is a coarse-graded soil that includes a significant percentage of non-plastic fines. They should be placed under compact conditions. The experimental campaign was aimed at identifying some physical characteristics that can synthesize the homogeneity of the pyroclastic deposit in terms of shearing resistance. The preliminary results obtained in terms of grading curves, modified Proctor compaction curves, and stress-strain curves from conventional drained triaxial tests are presented and discussed in this paper. The latter were executed on fully saturated specimens after compacting the soil at the optimum water content and on the dry and wet sides of the Proctor curve. The overall initial outcomes of the experimental campaign indicated that this material has acceptable characteristics and is suitable for the construction of railway embankments.

Use of recycled concrete aggregates in stabilization of black cotton soil

The long-term performance of a pavement structure depends on its structural integrity and the stability of its underlying soils. The properties of black cotton (BC) soils are known to adversely affect the performance of pavement. BC soil is creating a lot of problems in constructing the pavements on it because of its low California bearing ratio (CBR) and high swelling potential behavior. Black cotton soil possesses poor strength, high swelling and shrinkage behavior on exposure to moisture. Pavements on BC soil require stabilization. Soil stabilization is a process utilized for improving the properties of undesirable weak soil. Stabilization of subgrade soil by chemical, thermal or mechanical techniques is very common practice and too expensive. Therefore, in this study, an attempt has been made to stabilize the BC soil subgrade by recycled concrete aggregate (RCA). The RCA are the waste aggregates obtained from demolition of concrete structure buildings, road, and bridges. The main aim of this study is to know the suitability of RCA waste as a stabilizer for BC soil in the construction of flexible pavements. In this investigation, properties of RCA and BC soil are evaluated, RCA is mixed in different proportions with the BC soil, and their influence on the CBR value and compaction curve are studied. Seven mixes (100% BC soil, 90% BC soil + 10% RCA, 80% BC soil + 20% RCA, 70% BC soil + 30% RCA, 60% BC soil + 40% RCA, 50% BC soil + 50% RCA, 40% BC soil + 60% RCA) are tested for CBR value in order to find the proportion which gives maximum CBR value. Based on the results, it is observed that for the BC soil used in this study, mix containing 60% BC soil and 40% RCA is the suitable mix proportion for the stabilization. For this proportion of mix, the CBR value increased from 3.53% to 11.2%. This accounts to 3.2 times increase in the CBR value, whereas the optimum moisture content (OMC) decreased from 27% to 22% and maximum dry density (MDD) increased from 1.22 gm/cm3 to 1.45 gm/cm3. Hence 60% BC soil and 40% RCA can be used to stabilize the given soil.

Differentiating the roles of proteins and polysomes in nucleoid size homeostasis in Escherichia coli

A defining feature of the bacterial cytosolic interior is a distinct membrane-less organelle, the nucleoid, that contains the chromosomal DNA. Although increasing experimental evidence indicates that macromolecular crowding is the dominant mechanism for nucleoid formation, it has remained unclear which crowders control nucleoid volume. It is commonly assumed that polyribosomes play a dominant role, yet the volume fraction of soluble proteins in the cytosol is comparable with that of polyribosomes. Here, we develop a free energy-based model for the cytosolic interior of a bacterial cell to distinguish contributions arising from polyribosomes and cytosolic proteins in nucleoid volume control. The parameters of the model are determined from the existing experimental data. We show that, while the polysomes establish the existence of the nucleoid as a distinct phase, the proteins control the nucleoid volume in physiologically relevant conditions. Our model explains experimental findings in Escherichia coli that the nucleoid compaction curves in osmotic shock measurements do not depend on cell growth rate and that dissociation of polysomes in slow growth rates does not lead to significant nucleoid expansion, while the nucleoid phase disappears in fastest growth rates. Furthermore, the model predicts a cross-over in the exclusion of crowders by their linear dimensions from the nucleoid phase: below the cross-over of 30–50 nm, the concentration of crowders in the nucleoid phase decreases linearly as a function of the crowder diameter, while decreasing exponentially above the cross-over size. Our work points to the possibility that bacterial cells maintain nucleoid size and protein concentration homeostasis via feedback in which protein concentration controls nucleoid dimensions and the nucleoid dimensions control protein synthesis rate.

Influence of PPD and Mass Scaling Parameter on the Goodness of Fit of Dry Ice Compaction Curve Obtained in Numerical Simulations Utilizing Smoothed Particle Method (SPH) for Improving the Energy Efficiency of Dry Ice Compaction Process

The urgent need to reduce industrial electricity consumption due to diminishing fossil fuels and environmental concerns drives the pursuit of energy-efficient production processes. This study addresses this challenge by investigating the Smoothed Particle Method (SPH) for simulating dry ice compaction, an intricate process poorly addressed by conventional methods. The Finite Element Method (FEM) and SPH have been dealt with by researchers, yet a gap persists regarding SPH mesh parameters’ influence on the empirical curve fit. This research systematically explores Particle Packing Density (PPD) and Mass Scaling (MS) effects on the agreement between simulation and experimental outputs. The Sum of Squared Errors (SSE) method was used for this assessment. By comparing the obtained FEM and SPH results under diverse PPD and MS settings, this study sheds light on the SPH method’s potential in optimizing the dry ice compaction process’s efficiency. The SSE based analyses showed that the goodness of fit did not vary considerably for PDD values of 4 and up. In the case of MS, a better fit was obtained for its lower values. In turn, for the ultimate compression force FC, an empirical curve fit was obtained for PDD values of 4 and up. That said, the value of MS had no significant bearing on the ultimate compression force FC. The insights gleaned from this research can largely improve the existing sustainability practices and process design in various energy-conscious industries.

Effects of Dry Density and Moisture Content on the Kaolin–Brass Interfacial Shear Adhesion

Kaolin clay, with its consistent properties, fine particle size, high surface area, and extensive historical use, stands out as a reliable choice for laboratory research. This study aims to assess the interface shear adhesion behaviour between compacted clay and a metallic surface. For this purpose, a new testing approach was developed. The proposed method is simple, requires neither advanced equipment nor specialised test procedures, and, thus, represents an improvement over existing practices in this field. The experimental program focuses on determining the interface shear adhesion strength between reconstituted kaolin clay and a metallic surface. The kaolin clay testing specimens were dynamically compacted at various energy levels and moisture contents. The results indicate that the optimum moisture content is 30%, which provides the highest density to the sample and divides the compaction curve into dry and wet sides. Furthermore, the results demonstrate that the interface shear adhesion strength increases with the clay’s dry density. Conversely, there is a significant decrease in strength as the moisture content specifically rises on the wet side of the compaction curve. The adhesion behaviour was also attributed to matric suction, where high suction enhanced interfacial adhesion, while low suction weakened bonding and diminished adhesion. Additionally, this study presents a unique three-dimensional contour graph illustrating the combined effects of dry density and moisture content on the interfacial adhesion.

Micro-structural characterization of the lubrication behavior of asphalt binder during the compaction of asphalt mixture

This study aims to investigate the lubrication behavior of asphalt binder on the basis of Stribeck tribology theory, employing viscosity test, gyratory compaction test, and image processing techniques. The quantification of the lubrication regimes and their transformation was performed by an image processing algorithm that measures the thickness of the mortar film based on the minimum distance. The hydrodynamic regime transforms into the elasto-hydrodynamic regime by 23.2% below 60 gyrations. 11.6% of the elasto-hydrodynamic regime transforms into the mixed regime above 60 gyrations, causing an increase in friction. The slope of the compaction curve follows the variation rule of the Stribeck friction coefficient. Asphalt viscosity in the range of 380–460 mPa·s is recommended for optimum compaction.

Empirical Equations Expressing the Effects of Measured Suction on the Compaction Curve for Sandy Soils Varying Fines Content

To effectively apply various soil types for embankments, understanding their compaction characteristics is crucial. One crucial factor affecting compaction is suction, which plays a significant role as it is typically performed under unsaturated conditions. Suction varies with soil density, water content, and fines content. This study directly measures suction after soil compaction using the triaxial apparatus, unlike the Soil water characteristic curve (SWCC), assessing its impact on compaction characteristics. Immediate suction measurement after compaction provides apparent suction, resembling on-site conditions with open pore air pressure. Comparing SWCC with apparent suction at each compacted state reveals that suction and air entry value increase with initial density, positively impacting compaction. Notably, apparent suction aligns better with wetting process suction from the SWCC due to added water during specimen preparation. Empirical equations are derived to obtain suction contours across various density and saturation ranges, aiding in understanding suction variations on the compaction curve. Even slight variations in saturation causes noticeable changes in apparent suction during higher compaction efforts, affecting soil compaction characteristics. Therefore, the precise control of saturation control is needed to achieve desired properties of compacted soil, especially at higher compaction efforts and with various soil types. This understanding significantly impacts the mechanical behavior of unsaturated soils.