Range Of Dry Densities Research Articles

Enhancing Density Prediction of Agricultural Land Soil through Void Area Curve Analysis

Thresholding is a digital image analysis method used to distinguish objects from the background in images and it is mainly used for void and density analysis in soil. It is important to select an appropriate thresholding method because the accuracy of void analysis can vary significantly depending on the threshold value; however, there is currently no standard for soil density analysis. Therefore, this study proposes an image analysis method for soil density prediction. The experimental process involved collecting soil samples from agricultural lands, encompassing various soil textures including sandy loam, loam, silt loam, and silty clay loam. These samples were then meticulously prepared under controlled conditions, ensuring a comprehensive range of dry densities and water content levels. Digital images of the soil samples were acquired using a Canon EOS100d camera, employing a high-resolution setup that provided precise imaging capabilities. The porosity of the soil image is calculated by various thresholding methods. Based on the analysis results, we propose a void area curve, a new approach that can be applied to the soil density prediction. The void area curve is the relationship curve between the threshold value and porosity of the soil image. The standard deviation of the void area curve showed a high correlation with the dry density of the soil. The standard deviation of the void area curve was used to predict the dry density under various soil texture and water content conditions, and the RMSE was 0.037 t/m3. The method of estimating soil density with the standard deviation of the void area curve can be used more generally than the existing analysis method because there is no need to select a specific threshold value.

Experimental study on mode I fracture characteristics of compacted bentonite clay

To explore the pure mode I fracture characteristics of compacted Gaomiaozi bentonite clay, notched semi-circular bend specimens of compacted Gaomiaozi bentonite with different dry densities and moisture contents were prepared by using the self-designed compaction and slitting molds, and then three-point bending tests were carried out, real-time monitoring was also conducted with the help of digital image correlation method. Based on the test results, the effects of dry density (1.5 g·cm−3, 1.6 g·cm−3, 1.7 g·cm−3, 1.8 g·cm−3) and moisture content (6.20%, 9.48%, 13.65%, 16.47%) on the mode I fracture toughness of compacted Gaomiaozi bentonite were analyzed, and the development of fracture process zone (FPZ) was also revealed. The results show that the pure mode I fracture toughness of compacted Gaomiaozi bentonite is in the magnitudes of 30 to 180 kPa·m1/2 within the testing range of dry density and moisture content. The mode I fracture toughness increases with increasing the dry density. At a moisture content of 9.48%, the mode I fracture toughness obtains a peak value, and with the decrease or increase of moisture content, the mode I fracture toughness presents a general decreasing trend. The length of the fully developed fracture process zone and the critical crack tip opening displacement decrease first and then increase with the increase in moisture content, while there is no obvious regularity in the variations of fully developed FPZ length and critical crack tip opening displacement with respect to dry density.

Sound-insulation and photocatalytic foamed concrete prepared with dredged sediment

Recycling of dredged sediment (DS), derived from the routine dredging operation of rivers, lakes and seas, into construction materials represents an eco-friendly way to alleviate the burden on the environment. At higher incorporation dosages, however, DS causes a dramatic reduction in the mechanical properties of the host materials, which greatly stymies a broader application. In this study, DS from Taihu Lake, combined with ground granulated blast-furnace slag (GGBS) and calcium carbide slag (CCS), was used to produce low-strength foamed concrete (FC). Moreover, visible-light active Bi4Ti3O12 photocatalyst was added to the developed FC to obtain photocatalytic-functional and sound-proof products, which can be used as highway barrier walls. The results showed that within a dry density range of 500–1000 kg/m3, the compressive strength of the FC decreased greatly with an increase in the porosity. However, above 1000 kg/m3, the porosity exerted a much dwindled impact on the compressive strength. The pore structure of the sediment-based FC played a decisive role in influencing the basic properties and functional performance, which might follow the fractal characteristics. At a fixed dosage of foaming agent (hydrogen peroxide (HP)), the specimens prepared with 60% cement and 40% DS (DS-40) had the best sound insulation effect (1767 m/s, 9% HP), the lowest thermal conductivity (0.2831 W/m·k, 6% HP) and an excellent photocatalytic NO removal (14.1%, Bi4Ti3O12), which was the optimal mixture for manufacturing sound barrier walls. A broader application of photocatalytic-functional sediment-based FC offers a sustainable way in recycling DS, reducing air pollution and creating pleasant living environments.

Analysis of Mechanical Properties of Loess with Cement Incorporation Ratio

Taking loess as the research object, the influence of cement content on mechanical properties of loess was studied. Firstly, the basic physical parameters of loess were obtained through laboratory physical index test, and improved by using Portland cement. Secondly, under different incorporation ratios (3%, 5%, 7%, 9%), heavy compaction test and liquid-plastic limit test were carried out respectively to obtain mechanical parameters of cement-improved loess. Finally, the shear strength parameters and compressive strength of the improved soil samples are obtained by unconsolidation undrained triaxial shear test and unconfined compressive strength test. The results show that the liquid limit, plastic limit and plastic index of loess improved by adding cement increase compared with the original soil sample, indicating that the binding force between soil particles is improved and the plasticity is enhanced. The variation range of dry density and water content has no obvious relationship with the content of cement. At the same time, the compressibility of soil is reduced and the collapsibility of soil is eliminated. With the increase of age, the strength of cement-modified soil also increases. Through unconsolidated and undrained triaxial shear tests and unconfined compressive strength tests, the strength of loess improved significantly after adding cement, and the strength of soil-cement increased with the increase of cement content, and water stability was obviously improved.

Analysis of Mechanical Properties of Loess with Lime Incorporation Ratio

Taking loess as the research object, the effect of lime content on mechanical properties of loess was studied. Firstly, the basic physical parameters of loess were obtained by laboratory physical index test and improved by lime. Secondly, the mechanical parameters of lime-modified loess were obtained by heavy compaction test and liquid-plastic limit test under different incorporation ratios (3%, 5%, 7%, 9%). Finally, the shear strength parameters and compressive strength of improved soil samples were obtained by unconsolidated and undrained triaxial shear test and unconfined compressive strength test respectively. The results showed that the liquid limit, plastic limit and plastic index of the loess improved by adding lime increased compared with the original soil sample, indicating that the binding force between soil particles was improved and the plasticity was enhanced. The variation range of dry density and water content had no obvious relationship with the dosage of lime. At the same time, the compressibility of soil is reduced and the collapsibility of soil is eliminated. With the increase of age, the strength of lime-modified soil also increases. Through unconsolidated and undrained triaxial shear tests and unconfined compressive strength tests, the strength of the loess improved by adding lime is significantly improved, and the strength of soil-cement increases with the increase of the dosage, and the water stability is obviously improved.

Influencing Factors on the Accuracy of Soil Calibration Models by EDG

Compaction is an important standard in evaluating the quality of earth filling work. The EDG, an electrical density gauge, is a new type of fast and nondestructive compaction detection equipment. It is used to test the dry density and water content of the soil by establishing a soil calibration model while the accuracy of measurement is mainly based on the precision of equation of calibration model. In this paper, the factors affecting the accuracy of the soil calibration model were studied by an indoor calibration test, and soil samples were prepared to verify the accuracy of the soil calibration model. The test results showed that the dry density range, water content range, and sample quantity 13 samples of soil had a significant influence on the correlation coefficient (R2) of the equation of the soil calibration model. In addition, when using the calibration model with different sample numbers and sample combinations but similar correlation coefficients to test multiple groups of density and moisture content, there are also differences in the expected value and standard deviation of the error probability curve of the test results. In the engineering practice, the reasonable sample quantity was determined by the applicable range of dry density and water content obtained from the measurement error analysis of the soil calibration model.

Preparation and characterization of lightweight aggregate foamed geopolymer concretes aerated using hydrogen peroxide

In this study, novel green lightweight foamed geopolymer concretes (LFGC) aerated using hydrogen peroxide based on fly ash, metakaolin and expanded polystyrene (EPS) particles was developed for thermal insulation materials. Physical properties, mechanical strength, thermal characteristics and permeability of LFGC were evaluated by designing and optimizing the components of EPS particles, hydrogen peroxide, metakaolin and fly ash. Meanwhile, the internal microstructure was also investigated by pore structure and scanning electron microscope. The results show that as the content of EPS particles and hydrogen peroxide increased, the compressive strength of LFGC decreased by 57.6% and 9.7%, respectively. The lightweight and thermal insulation properties are enhanced as the EPS particles and hydrogen peroxide content increase due to the contribution of low-density EPS particles and closed foamed air voids. The LFGC presented its dry density range of 300–650 kg/m3, the compressive strength between 2.0 and 5.5 MPa and the thermal conductivity between 0.122 and 0.195 W/m∙K, showing better mechanical strength than the traditional ordinary cement foamed concrete with the same density. Meanwhile, the microstructure also shows that the EPS particles have good compatibility with the foamed geopolymer pastes.

Effect of initial compaction pressure and elevated temperature on swelling pressure of two Indian bentonites

The present article brought out the effect of compaction pressure and temperature on the swelling pressure of two Indian bentonites. The isochoric swelling pressure tests were carried out using a modified oedometer at ambient and elevated temperatures. The effect of compaction pressure on swelling pressure of compacted bentonite was studied by conducting constant volume swelling pressure tests on two bentonites for a range of dry densities between 1.3 and 1.8 Mg/m3. The effect of temperature on the swelling pressure of bentonites was evaluated by conducting tests on three different conditions, such as isothermal, incremental and decremental temperature conditions. The isothermal swelling pressure tests were performed at three different temperatures such as 25 °C, 55 °C and 95 °C at a dry density of 1.6 Mg/m3. In incremental and decremental temperature conditions swelling pressure tests were performed at various temperatures in a stepwise manner. The effect of temperature on swelling pressure of compacted bentonites was investigated theoretically using Diffused double layer theory. A correlation between the compaction pressure, dry density and swelling pressure of bentonites is presented based on the experimental results. Further the correlation equation was validated with literature-reported results of three bentonites. In isothermal condition, an increase in temperature resulted in increase and decrease in swelling pressure for divalent bentonite-A and monovalent bentonite-B, respectively. In the incremental temperature condition, swelling pressure was found to increase slightly for both the bentonites. During the decremental temperature condition, the swelling pressure was noted to decrease significantly for both the bentonites. The theoretically calculated swelling pressure was found to increase with an increase in temperature for both the bentonites.

Experimental study on tensile strength of unsaturated fine sands

This paper describes the development of a direct tension apparatus and its application to test the tensile strength of unsaturated fine sands. The apparatus consists of two halves of wedge-shaped specimen molds. A criterion is developed for designing the inclination angle of the inner sidewall of the specimen molds as a function of soil–wall interface frictional angle and soil dilatancy angle. Tensile strength of unsaturated fine sands is measured over a range of dry density and water content. Results show that tensile strength generally increases with the increase in dry density. For relatively dense sand, tensile strength follows a non-monotonic double-peak pattern with increasing water content. The first peak occurs in the pendular regime and is attributed to peak occurrence of interparticle stress contributed by pendular water bridges. The second peak occurs in the capillary regime and is attributed to the capillary component of interparticle stress arising from negative pore pressure.

Preparation and Characterization of Ultra-Lightweight Foamed Concrete Incorporating Lightweight Aggregates

Increasing interest is nowadays being paid to improving the thermal insulation of buildings in order to save energy and reduce ecological problems. Foamed concrete has unique characteristics and considerable potential as a promising material in construction applications. It is produced with a wide range of dry densities, between 600 and 1600 kg/m3. However, at a low density below 500 kg/m3, it tends to be unstable in its fresh state while exhibiting high drying shrinkage in its hardened state. In this study, lightweight aggregate-foamed concrete mixtures were prepared by the addition of preformed foam to a cement paste and aggregate. The focus of the research is the influence of fly ash, as well as fine lightweight aggregate addition, on the properties of foamed concrete with a density lower than 500 kg/m3. Concrete properties, including stability and consistency in the fresh state as well as thermal conductivity and mechanical properties in the hardened state, were evaluated in this study. Scanning electron microscopy (SEM) was used to study the microstructure of the foamed concrete. Several mixes with the same density were prepared and tested. The experimental results showed that under the same bulk density, incorporation of fine lightweight aggregate has a significant role on compressive strength development, depending on the characteristics of the lightweight aggregate. However, thermal conductivity is primarily related to the dry density of foamed concrete and only secondarily related to the aggregate content. In addition, the use of fine lightweight aggregate significantly reduces the drying shrinkage of foamed concrete. The results achieved in this work indicate the important role of lightweight aggregate on the stability of low-density foamed concrete, in both fresh and hardened states.

Effects of a simulated gap on anisotropic swelling pressure of compacted GMZ bentonite

Gaomiaozi (GMZ) bentonite is a promising buffer material for Chinese high-level radioactive waste (HLW) disposal, and will be either compacted in situ or used as dense prefabricated material when constructing engineered barriers. Uniaxial compaction can induce anisotropy of the bentonite structure, resulting in anisotropic swelling. In this work, a series of swelling pressure tests were performed on compacted GMZ bentonite to investigate the anisotropy of its property and highlight the dry density effect. Two kinds of technological gaps were simulated to analyze the change in anisotropy of properties with limited swelling deformation. The relationship between swelling pressure and dry density was found to be logarithmic, and axial pressure increased more rapidly than radial pressure with dry density. The ratio of radial to axial pressure decreased significantly in the dry density range 1.395 Mg/m3–1.706 Mg/m3; beyond this, it remained at about 0.76. For the swelling volume ratio of less than 16.7%, the stable swelling pressure was controlled by the final dry density. For a larger swelling volume ratio, the axial gap induced a smaller swelling pressure compared with the case of no gap at the same final dry density.

Long-term Performance Studies on Strength Characteristics of Black Cotton Soil Reinforced with Untreated and Treated Coir Fibre

Strength retention on the long run can be improved by making coir fibres less water absorbent. In the present study, coir fibres have been alkali treated and admixed in black cotton soil. Use of untreated and treated coir fibres (UCF and TCF) to black cotton soil is comparatively investigated in terms of UCS using remoulded specimens compacted with wide range of dry densities and water contents on the basis of compaction test. Long-term performance is evaluated by curing the remoulded specimens for periods ranging from 0 to 360 days. The test results indicated that the strength of black cotton soil reinforced with UCF and TCF is significantly affected by fibre content, dry density and water content and changes the failure behaviour from brittle to ductile. Long-term performance can be significantly improved by using treated coir fibres, in which the reduction in strength of black cotton soil admixed with treated coir fibres indicated marginal loss of strength, at around 21.16%.

PREDICTION OF SOAKED CBR USING INDEX PROPERTIES, DRY DENSITY AND UNSOAKED CBR OF LEAN CLAY

Load bearing capacity of subgrade soil is of great importance to the integrity of pavement. Soaked CBR of subgrade soil is used as a design parameter for determining the total thickness of a pavement for an estimated ESAL. However, determination of soaked CBR values for pavement design involves soaking a large number of representative soil samples for four days. This is both time consuming and economically discouraging. Establishment of mathematical models for determining soaked CBR values for different types of soils using their index properties, dry densities and unsoaked CBR values is likely to aid design more quickly. With this background in mind, in this study soil samples were collected from sub-grade of an existing flexible pavement in Savar Cantonment Area, Dhaka, Bangladesh. The soil samples were then tested and the index properties were determined. The tested soil samples were identified as Lean Clay and CBR test was performed both in soaked and unsoaked conditions at different densities. The test results of the sample soil have led to the formulation of three empirical equations for predicting soaked CBR values. Index properties of soil from grain size analysis, Atterberg limits test and compaction characteristics from CBR test are used in the first equation to predict soaked CBR value of this lean clay soil. The second equation relates dry density with soaked CBR whereas the third equation relates unsoaked CBR with soaked CBR values for a varying range of dry densities. These equations may be used to predict soaked CBR value where the sub-grade consists of Lean Clay.

Production of lightweight aerated alkali-activated slag pastes using hydrogen peroxide

This study investigated the production of lightweight aerated alkali-activated slag pastes (LAAASP) using hydrogen peroxide (H2O2). A mixture of sodium hydroxide and sodium silicate solution was used for the activation of slag. Physical, mechanical, and thermal properties of samples cured under different curing conditions were investigated. Various water-to-slag ratios (W/S) and H2O2 contents were used to explore the expansion mechanism of fresh mixtures and to investigate their effect on apparent density. The LAAASP produced were in the apparent density range of 516–1199 kg/m3 and had 0.5–30.0 MPa compressive strength. Thermal conductivities of aerated samples varied from 0.117 to 0.206W/m·K in the dry density range of 480–1098 kg/m3 and were lower than thermal conductivities reported for autoclaved aerated concrete. The use of more than 0.75% H2O2 by mass of slag was found to be non-essential to achieve low-density pastes.

Geotechnical properties of lateritic soil as subgrade and base material for road construction in Abeokuta, Southwest Nigeria

Lateritic soils that overburden Mohammad Buhari Estate in Abeokuta area of Ogun State, Nigeria is in great use for road construction. However, little is known of their geotechnical properties and suitability as base, sub-based and sub-grade materials for road construction. This study is aimed at utilizing in accordance with regulatory standards of Nigeria, the geotechnical techniques to investigate the properties of this lateritic soil. The samples were collected at 0. 25m deep at different locations and were subjected to the following laboratory test; Particle size analysis, Atterberg limits test, Compaction test, Californian Bearing Ratio test, Moisture content and Specific gravity test. The result shows un-soaked CBR test from 12.52-55.84 %. The specific gravity results range from 2.57-2.89 while the optimum moisture content and maximum dry density range from 18.20-28.30% and 1.48-1.81mg/m3 respectively. The liquid limit, plastic limit and plastic index ranges from 12.0 to 40.1%, 10.0 to 22.0% and 2.8 to 20.4% respectively. This implies that lateritic soil present throughout the study area is suitable for use as sub-base and base materials since the geotechnical properties are fairly within the regulatory standards of Nigeria.

Water transport in electrokinetic remediation of unsaturated kaolinite. Experimental and numerical study

Abstract This work evaluated water transport that occurs in a partially saturated soil of low hydraulic permeability when undergoing an electrokinetic remediation process. The soil used was a compacted kaolinite. To evaluate a wide range of possible conditions, soil with three different initial water contents (10, 15 and 20%) was used, obtaining a range of dry densities of 1300–1600 kg m−3. The tests were performed using a lab-scale setup with a soil capacity of 675 cm3 and applying different electrical potential gradients (0.5, 1, 1.5 and 2 V cm−1). The experimental results obtained were used to validate a conceptual model implemented in COMSOL. The validated model was used to conduct a detailed interpretation of the observed water transport processes and to perform a study of the hydraulic behaviour of the soil as a function of the initial conditions of compaction, water saturation and applied electrical potential gradient.

The anaerobic corrosion of carbon steel in compacted bentonite exposed to natural Opalinus Clay porewater containing native microbial populations

ABSTRACTA long-term in situ corrosion experiment is ongoing in the Mont Terri Underground Research Laboratory in Switzerland to (i) measure the in situ corrosion behaviour of carbon steel in compacted bentonite under simulated repository conditions, (ii) study the effect of the bentonite buffer density on microbial activity and microbially influenced corrosion and (iii) study the effect of welding on the corrosion rate. Carbon steel corrosion coupons, with and without welds, were surrounded by compacted bentonite with a range of dry densities and mounted in modules allowing free exchange with the local anoxic groundwater. After about 20 months of exposure, corrosion coupons and bentonite were sampled. A complex corrosion product was identified, consisting predominantly of magnetite. The bentonite adjacent to the metal was finer grained, more dispersed and enriched in iron. Aerobic, anaerobic and sulphate-reducing bacteria were identified both in the porewater surrounding the modules and in the bentonite.This paper is part of a supplement on the 6th International Workshop on Long-Term Prediction of Corrosion Damage in Nuclear Waste Systems.

Role of smectite-rich shales in frequent foundation failures in southeast Nigeria

This paper investigated the geotechnical properties of smectite-rich shale, and its implications as foundation material. Ten expansive shale samples were collected from foundation materials at Akpugo in Nkanu West L.G.A. of Enugu State, southeast Nigeria. Samples were subjected to grading, Atterberg limits-cum-compaction tests, slake durability, specific gravity, permeability, undrained triaxial tests and x-ray diffraction scan. Fines and sand contents of the soil samples range from 51–97% and 3–49% respectively. Liquid limit, plastic limit and plasticity index have average values of 60.7, 19.1 and 43.3% respectively. Linear shrinkage and free swell showed average of 16.3% and 76%. These results are indicative of predominant clay soil with high plasticity, compressibility and water holding capacity. XRD scan established presence of smectite and illite clay minerals, confirming soil high plasticity, capable of causing instability in foundation soil. The shale achieved maximum dry density range between 1.79 and 1.94 kg/m3 at optimum moisture content range of 6.9–12.8%, indicating poor to fair foundation materials. The shale cohesion ranges from 15 to 30 kPa while the angle of friction ranges between 10° and 18°, signifying an average strength soil material. Samples slake durability index and specific gravity fall within 24–55% and 2.50–2.58 respectively, suggesting non-durable and weak soil. Permeability of the samples ranges between 7.36 ×10−6 and 4.77 ×10−8 cm/s which suggested low drainage capable of causing water-log at sites. Therefore, the shale could be generally classified as poor to fair foundation material, which on moisture influx experience reduction in strength due to deterioration of its constituent minerals, especially clay and cement materials during the lifespan of engineering structures. Authors therefore recommend modification of foundation soil, appropriate foundation design and good drainage control as ways of improving stability of engineering structures underlain by expansive shale.

Influence of initial degree of saturation on swell pressures of compacted Barmer bentonite specimens

Densely compacted bentonite or bentonite–sand mixture has been identified as suitable buffer in deep geological repositories as its exceptionally high swelling capacity enables tight contact between the waste canister and surrounding rock. The degree of saturation of the compacted bentonite buffer can increase upon ingress of groundwater from the surrounding rock mass or decrease from evaporation due to high temperature (50–210°C) derived from the waste canister. Available studies indicate that the influence of initial moisture content or degree of saturation on the swell pressure or swell potential of compacted bentonites is unclear. Some studies suggest that initial degree of saturation has an influence, while others suggest that it does not have bearing on the swell pressure of compacted bentonites. This paper examines the influence of initial degree of saturation in montmorillonite voids (termed, Sr,MF) on swell pressure of compacted Barmer bentonite–sand mixtures (dry density range: 1.4–2Mg/m3) from micro-structural considerations. The experimental results bring out that, constant dry density specimens that developed similar number of hydration layers upon wetting developed comparable swell pressures and were unaffected by variations in initial Sr,MF values. Comparatively, constant dry density specimens that developed dis-similar number of hydration layers upon wetting established different swell pressures and were responsive to variations in initial Sr,MF.

About differences of swelling pressure — dry density relations of compacted bentonites

The swelling capacity is one of the most characteristic properties of bentonites. This property, along with others, made bentonite a candidate material for the safe disposal of high-level radioactive waste (HLRW). For HLRW-barrier systems the swelling pressure is of particular interest because it basically controls sealing properties (a large swelling pressure generally results in low permeability). Commonly, the swelling pressure is investigated as a function of compaction and hence plotted against the density, usually the dry density. Different dry density/swelling pressure relations of bentonites were published. Therefore, the aim of the present study was to identify reasons for these differences. To be able to compare a significant set of different bentonites, a small scale swelling pressure device was developed which is based on measuring a swelling pressure related value of 500mg bentonite powder. This device allowed recording about 200 single values (in duplicate) and hence dry density/swelling pressure relations of thirty six different bentonites. The differences of the dry density/swelling pressure plots of different bentonites could be explained by i) different ways to obtain a range of dry densities (either constant load or constant water content), ii) different portions of uncompactable porosity of the different bentonites, and iii) different smectite contents.