Dry Unit Weight Values Research Articles

Triaxial testing response of compacted iron ore tailings considering a broad spectrum of confining pressures

The filtered tailings disposal (dry stacking) up to 300 m high is an alternative to overcome the drawbacks related to the slurry tailings storage in large impoundments as it is safer and demands smaller portions of the existing landform. Even so, the understanding of the denser and dewatered material response over a broad range of confining pressures is essential to safely design tall dry stacking tailings facilities. Accordingly, the present research assesses the mechanical behavior of compacted iron ore tailings through triaxial tests. A series of compression and extension drained and undrained triaxial tests were conducted over a wide spectrum of confinements (σ́3 ranging from 75 to 8,000 kPa) to check possible particle breakage occurrence and effects. The influence of the initial density due to compaction was, as well, evaluated since the tests were performed using specimens molded at distinct dry unit weight values. The results were analyzed in the light of the critical state soil mechanics and have indicated the existence of a curvilinear critical state line in the ν: log ṕ plane. Small particle breakage has occurred and can be associated with reduction in surface roughness, breakage of asperities, and reduction in particle angularity. Moreover, a tendency for static liquefaction was observed amongst the loosest specimens sheared under the lowest confining levels.

Rock - soil transition during weathering of rhyolite

Concentric layers of weathered materials around core-stones show the rhyolite to experience sequential, but gradational, changes in visible features, textures and mineralogy as it transforms from ‘rock’ into ‘soil’. The changes start with the opening-up of grain boundaries and micro-cracks (stage 1) followed by their dark brown staining (stage 2) and the subsequent alteration (to sericite and clay minerals) of plagioclase feldspar groundmass grains and phenocrysts (stage 3). Biotite flakes are then bleached and altered (to chlorite and clay minerals) (stage 4) before there starts alteration (to sericite and clay minerals) of groundmass alkali feldspar grains (stage 5) and finally alteration of alkali feldspar phenocrysts (stage 6). Quartz grains are not altered during these stages of weathering but disaggregate and reduce in size due to continual opening-up of grain boundaries and micro-cracks. Increasing stages of weathering are marked by decreasing dry unit weights, dry densities and uniaxial compressive strengths, but increasing apparent porosities. The transition between ‘rock’ and ‘soil’ occurs during weathering stage 6 when all plagioclase groundmass grains and phenocrysts have been altered as have been all alkali feldspar groundmass grains and most phenocrysts. Stage 6 is marked by large apparent porosities (>14%) but low values of dry unit weight (<21.90 kN/m3) and dry density (<2,232 kg/m3).

Effect of Emulsified Asphalt on Expansive Soil Strength and Swelling

Some clay soils classified as extended soils threaten the structures resting on them. Many additives are available to improve the properties of expanded soils. This study tries to investigate the consequences of wetting-drying cycles on the swelling behavior of modified expansive clayey soils under laboratory conditions by modifying expansive clayey soil samples using emulsified asphalt. Five different percentages of emulsified asphalt were used: (2, 4, 6, 8, and 10) %. The natural and treatment soils were tested for classification, specific gravity, compaction characteristics, free swell and swell pressure, consolidation, and compressive strength. The liquid limit and plasticity index have been lowered by adding Emulsified Asphalt. After that, the effects of Emulsified Asphalt on undrained shear strength characteristics (cohesion and friction angle) have been studied. The results revealed that when the emulsified asphalt content was increased to 10%, the swelling pressure and swelling potential decreased by 58 and 78 %, respectively. The swell and shrink improvement factor for the 10% emulsified asphalt addition is always larger than 75%. As the duration of wetting-drying cycles increased, the swelling pressure and swelling potential values were also reduced. The plastic limit, on the other hand, increased as the Emulsified Asphalt content increased. Increasing the amount of Emulsified Asphalt increased the maximum dry unit weight values, whereas the optimum water contents increased. It was concluded that emulsified asphalt stabilization may be useful for expansive clay as it improves compressive shear strength.

ASSESSMENT OF SUSTAINABLE GREEN CONCRETE PROPERTIES USING RECYCLED PLASTIC WASTE AS REPLACEMENT FOR FINE AGGREGATE USING MACHINE LEARNING TECHNIQUE

The use of waste plastic as a replacement for natural aggregates in cement composites can solve the problem of the disposal of waste plastics sustainably. This study aims to investigate and compare the impact of replacing fine natural aggregate with recycled aggregates made up of polyethylene (PE) in M30 grade of concrete by analyzing the physical and mechanical properties of both fresh and hardened concrete in terms of workability, dry and fresh unit weight, 28-day compressive strength, flexural strength, split tensile strength, and ultrasonic pulse velocity. Nine concrete mixtures containing PE was prepared as a partial volumetric replacement for fine aggregate with substitution levels of 0%, 5%, 10%, 15%, 20%, 25%, 30%, 35% and 40%. Due to the application of superplasticizers, the workability of concrete containing recycled plastic has improved. The fresh and dry unit weight values of the PE-based concrete decreased by 8.16% and 8.6%, respectively, with the increase in PE aggregate and can therefore be considered lightweight concrete. The compressive strength of concrete at various ages is reduced as the quantity of plastic in concrete increases. As the PE replacement ratio in concrete increased, the flexural strength and split tensile strength also declined. Up to 10% replacement gives acceptable physical and mechanical properties of concrete for structural purposes. In this study, artificial neural network (ANN) was used to predict the fresh and hardened properties of waste plastic aggregate-based concrete, and it was discovered that it can predict concrete qualities with good accuracy (R<sup>2</sup> = 0.99).

Stabilization of Dredged Materials Using Cement and a Pozzolanic Binder Mineral Additive

In this study, it was aimed to stabilize the dredged materials with low bearing capacity, brought from Edirne, by using cement and pozzolanic binder mineral additives. In the first stage of the study, the geotechnical properties of the dredging materials were determined. Then, the optimum water contents and maximum dry unit weight values of the soil samples without additives and with different additive ratios were found by compaction tests. Pure and additive unconfined compressive samples were prepared with the optimum water contents obtained in the compaction tests. Samples were prepared by adding 8%, 10% and 12% cement and 2% pozzolanic binder additive by weight to the dredged materials. Unconfined compressive tests were performed on the samples at the end of instant, 1-day, 7-day and 28-day curing periods. In addition, soaked CBR, permeability and flexural tests were performed on 12% cement+pozzolanic added samples. As a result of the experiments, with the addition of cement and pozzolanic binder additives in different ratio to the dredged materials, permeability decreased, unconfined compressive strength, soaked CBR values and flexural strength increased significantly.

Rock-Soil Transition In Weathering Of A Porphyritic Biotite Granite

Concentric layers of weathered materials around core-stones show the porphyritic biotite granite to experience sequential, but gradational, changes in visible features, textures and mineralogy as it transforms from ‘rock’ into ‘soil’. The changes start with the opening-up of grain boundaries and micro-cracks (stage 1) followed by their dark brown staining (stage 2) and the subsequent alteration (to sericite and clay minerals) of groundmass plagioclase feldspar grains (stage 3). Biotite flakes are then bleached and altered (to chlorite and clay minerals) (stage 4) before there starts alteration (to sericite and clay minerals) of groundmass alkali feldspar grains (stage 5) and finally alteration (to sericite and clay minerals) of the alkali feldspar phenocrysts (stage 6). Quartz grains are not altered during these stages of weathering, but disaggregate and reduce in size due to continual opening-up of grain boundaries and micro-cracks. Increasing stages of weathering are marked by decreasing dry unit weights, dry densities and uniaxial compressive strengths, but increasing apparent porosities. The transition between ‘rock’ and ‘soil’ occurs during stage 6 when all plagioclase, and most alkali feldspar, groundmass grains have been altered as are some alkali feldspar phenocrysts. Stage 6 is marked by large apparent porosities (>18%) but low values of dry unit weight (<20.81 kN/m3), dry density (<2,122 kg/m3) and uniaxial compressive strength (<1.8 MPa).

Characteristics of Engineered Waste Materials Used for Road Subbase Layers

Coal fly ash (FA) and basic oxygen furnace (BOF) slag are the by-products of coal combustion in power stations and steel plants, respectively. The disposal of these wastes would require landfill space and can cause environmental pollution. In order to avoid disposal, the use of FA and BOF slag as sub-base material in highway pavement was investigated. The first part of this research was the characterization of FA and BOF in terms of their chemical and mineralogical compositions as well as the microstructural analysis. This is followed by the preparation of soil mixtures containing different proportions of kaolin, FA, BOF slag (0%, 15%, 20% and 25% by weight) and lime at a constant ratio (5%). Kaolin was used to represent the natural soil. The soil mixtures were cured for 1, 7 and 28 days and some were cured 56 days. At each curing age, the dry unit weight (γdmax), the unconfined compressive strength (UCS) and California bearing ratio (CBR) were determined. X-ray diffraction (XRD) and scanning electron microscopy (SEM) techniques were also used to examine the changes in the phase-mineral composition and microstructure properties, respectively. The results show that the maximum dry unit weight values were observed in the mixture consisting of 25% FA, 15% BOF slag and 5% lime. The XRD analyses of kaolin soils containing, FA, BOF slag and lime exhibited the formation of hydrated products such as portlandite (C-H), calcium silicate hydrates (C-S-H) and calcium aluminium silicate hydrate (C-A-S-H), which increase with the age curing. According to results obtained, FA and BOF slag can be used in road base and sub-base materials.

COMPACTION CHARACTERISTICS OF A FINE-GRAINED SOIL POTENTIAL FOR LANDFILL LINER APPLICATION

Increasing population growth and urbanization results in increased demand for waste disposal processes and facilities that can protect public health and the environment. In the Philippines, there is a great demand to construct sanitary landfills (SLF) with only 387 local government units (LGUs) or equivalent to 23.86% compliant to date with Republic Act 9003 which mandates all LGUs to use the sanitary landfill. The compaction characteristics of a locally abundant fine-grained soil at different compaction energy levels were investigated as part of a broader study in the suitability of the soil as a landfill liner material. Compaction is essential in the preparation of a well-compacted soil liner in a sanitary landfill to avoid or minimize the migration of leachate and thereby reduce the risk of groundwater pollution. The physical properties are determined through a series of laboratory tests which covers the grain-size distribution, specific gravity, Atterberg limits, soil classification, XRD and SEM-EDX. Correlations to estimate the compaction characteristics at any rational compaction energy (E) are developed. The maximum dry unit weight values at different compactive efforts were used to determine void ratios which were then utilized to compute for the saturated hydraulic conductivity using numerical model for hydraulic conductivity for the same soil type. The resulting hydraulic conductivity ranges from 2.30 x 10-7 to 1.20 x 10-7 cm/sec well above the required value in the Philippines as per RA 9003 and its IRR for the intended Category I and II SLFs application

Comparison of Reduced Modified Proctor vs Modified Proctor

The compaction characteristics between reduced modified Proctor and modified Proctor tests have been compared. The results show that maximum dry unit weight values are comparable for both the tests but optimum moisture content values differ slightly more. For both the tests: optimum moisture content was found to correlate best with liquid limit, and the relationship for maximum dry unit weight with optimum moisture content was found to be almost the same. Since reduced modified Proctor requires less time and 40% less compaction energy as compared to modified Proctor test, it can be considered as a suitable alternative to the modified Proctor test.

Chemical, Mineralogical and Geotechnical Index Properties Characterization of Volcanic Ash Soils

Soils derived from volcanic ash are deposits formed from the weathering of the ejected material during volcanic activity. Volcanic ash is commonly known in geotechnical engineering as a difficult and unwanted material. The difficulties are related to the high-water content, high liquid limits, low unit weights, and high void ratios, which translates into possible engineering problems (e.g. compressibility and collapsibility). The characterization of these materials is important because volcanic soils represent 0.84% of the terrestrial soil surface, 60% of which are located in tropical zones. These percentages represent areas with a high human population and constant demographic and economic growth. This paper presents the chemical, mineralogical and geotechnical index properties characterization of soils derived from volcanic ashes through laboratory testing and compares them with the results found in the literature. The SEM results shows the high void reported in the literature. The index properties obtained coincide with the ranges reported. However, lower values of dry unit weight were observed, which are related to the transportation processes of the particles and with higher index properties values due to mineralogical components such as allophane. Therefore, the study of volcanic ash soils requires a rigorous knowledge and understanding of the soil formation, depositional environment, and mineralogy. The chemical characterization of the volcanic ash plays an important role to understand water retention characteristics and their influence on the different geotechnical properties.

Methods used to determine maximum and minimum dry unit weights of sand: Is there a need for a new standard?

Known challenges exist with maximum (γdmax) and minimum (γdmin) dry unit weight measurements; the respective dry unit weight results depend very much on the method or standard used. A laboratory testing programme was completed to systematically determine and compare γdmax and γdmin values derived for six different sand types by using different methods. The tested sands contained a wide variety of mineralogical and fines contents. The γdmax and γdmin determinations were performed according to the following methods: British Standards Institution (BS) standards; American Society for Testing and Materials (ASTM) standards; Deutsches Institut für Normung (DIN) standards; Dansk Geoteknisk Forening (DGF) guidelines; Norwegian Geotechnical Institute (NGI), Geolabs, and Fugro proprietary methods. Differences in testing procedures, material requirements for testing, and the effects of soil degradation during testing introduce challenges and large differences in γdmax and γdmin values for each of the six sand types were observed. Therefore, it is concluded that there is a need for the development of new standards for a robust determination of γdmax and γdmin values. Specifically, a standard for determining γdmax is required to consistently obtain results at the upper bound of dry unit weight values for the likely range of sands — without crushing the sand grains.

Linking Soil Design and Quality Control of Compacted Soils Through an Improvement of the Acceptance Zone of the RAMCODES Methodology

We propose an enhancement in the generation of the acceptance zone of the RAMCODES methodology; in this research, the new zone is called “optimum performance zone”. The “optimum performance zone” for a compacted soil was obtained by applying concepts of linear programming to soil mechanics. This novel approach links the mean variables of soil design (resistance and hydration conditions) with the traditional quality control (minimum compaction percentage). The optimum performance zone is a geometric site in the water content–dry unit weight plane, within which any compaction state (defined by specific values of dry unit weight and water content) has a high probability of fulfilling a pre-established value of mechanical response and a minimum compaction percentage, while also satisfying pre-established hydration conditions (minimum and maximum saturation degrees). In order to ascertain the concordance of the mechanical performance of compacted soils in situ with the mechanical performance of compacted soils in the laboratory, a soil that later would be compacted in situ was submitted to mechanical characterization, and a factorial experimental design was developed and performed. A surface response was plotted from experimental data; the resistance map of the soil was obtained using the RAMCODES approach, and the optimum performance zone proposed in this research was also plotted. The response of a compacted soil, predicted by the optimum performance zone, was verified using soil samples from earthwork built with the soil that was previously analyzed, indicating that the optimum performance zone links the mean variables considered in design with the minimum compaction percentage established by past experiences or by soil specifications. These results imply that the optimum performance zone has field applications for quality control and for reception of compacted soils, guaranteeing an optimum mechanical performance that fulfills the minimum compaction percentage and thus improves quality, security, reliability, and efficiency of compacted soils.

A Proposed Approach for Evaluating Soils Optimum Moisture Content Arithmetically and Use Statistical Functions for Checking Method

The processing of optimum moisture content for specific soils as indicated by ASTM D698 specifications detail relies upon developing the fitting third or second degree bend connection between dampness content versus soil dry unit weight on a fitting bend, the registered optimum moisture substance may contrast for a similar soil as for fitting bend figure and its position. The main objective of this study is to evaluate the optimum moisture content value based on computing average moisture content adapted from standard or modified Proctor compaction test trials and compared it with respect to the computing optimum moisture content using standard method. The research deals with a (52) compaction tests results with a wide range of optimum moisture content and dry unit weight to explore the relationships between them. The study also explores the maximum dry density values which versus standard optimum moisture content and average adopted moisture content. Statistical part depends on evaluating many statistical function values for standard and research method starts by evaluating significance of normality using Kolmogorov-Smirnov test. The average differences between standard optimum moisture content and an average value (this study depends) for moisture content was about (-0.20) and an average of differences for dry unit weight values was (0.261).

Compaction and consolidation behaviour of untreated and treated waste of Indian red mud

This study deals with the evaluation of the compaction and consolidation characteristics of untreated as well as hydrochloric acid (HCl)- and sodium chloride (NaCl)-treated red mud wastes. A series of standard and modified Proctor compaction and one-dimensional consolidation tests were conducted for the study purpose. Sodium chloride solutions of 1·71 and 3·42 M and hydrochloric acid solutions with pH of 1, 1·5, 2, 3 and 4 are selected to treat the waste. Results show that standard Proctor compaction tests yield inconsistent and low dry unit weight values with relatively high optimum water content. On the other hand, modified Proctor compaction test produced consistent dry unit weight values with low optimum water content. There is only a marginal improvement in dry unit weight and compression properties of hydrochloric acid- and sodium chloride-treated samples; however, the treatment proved effective in reducing pH of the waste. It has been noticed that the compressibility of both untreated and treated samples is appreciably low. Results elucidate that parameters such as the size of the particles and their shape, chemical and mineralogical compositions and surface charge properties can influence the compaction and compressibility characteristics of the waste. Overall, the study demonstrates that the red mud waste could be a potential resource material for geotechnical engineering applications.

Assessing the effects of mineral content and porosity on ultrasonic wave velocity

The influences of mineral content and porosity on ultrasonic wave velocity were assessed for ten hornfelsic rocks collected from southern and western parts of the city of Hamedan, western Iran. Selected rock samples were subjected to mineralogical, physical, and index laboratory tests. The tested rocks contain quartz, feldspar, biotite, muscovite, garnet, sillimanite, kyanite, staurolite, graphite and other fine grained cryptocrystalline matrix materials. The values of dry unit weight of the rocks were high, but the values of porosity and water absorption were low. In the rocks, the values of dry unit weight are related to the presence of dense minerals such as garnet so not affected by porosity. The statistical relationships between mineral content, porosity and ultrasonic wave velocity indicated that the porosity is the most important factor influencing ultrasonic wave velocity of the studied rocks. The values of P-wave velocity of the rocks range from moderate to very high. Empirical equations, relevant to different parameters of the rocks, were proposed to determine the rocks

Remediation of Clayey Soil Using Silica Fume

This paper evaluates the use of silica fumes as modification of fine-grained soil in order to alter undesirable properties of the native soil and create new useful soils. Silica fume as well as clay material, are used in changing the engineering properties to be compatible and satisfying this is due to their pozzolanic reactivity. The study aims to investigate the uses of these materials in geotechnical engineering and to improve the properties of soils. Four percentages of silica fumes were used in the present study, which is 0, 3, 5 and 7%. Classification, specific gravity, compaction characteristics, swell and swell pressure, CBR and compressive strength tests had been conducted on the prepared and modified soils. Results clarified that the silica fume increasing leads to decrease the plasticity index and liquid limit. Increasing in silica fume causes an increasing in plastic limit and optimum water contents while the maximum dry unit weight values decrease. The compressive shear strength, California Bearing Ratio (CBR), swell and swell pressure is improved by using silica fume so that silica fume can be considered as a successful material in improving the soil properties.

Preliminary Study on the Durability Properties of High-Volume Fly Ash Mortar Composites

Abstract The use of fly ash, a common industrial byproduct waste, is gaining popularity, especially in developing countries, in addressing environmental concerns surrounding the construction industry, such as reducing waste and CO2 emissions. However, the full potential of fly ash usage is yet to be exploited. The physical, mechanical, and durability properties of fly ash in concrete are well documented; in contrast, its durability properties in mortar require further investigations. The present study investigated the durability properties of high-volume fly ash (HVFA) mortar composites. Specifically, varying proportions of sand were replaced with cement and fly ash to examine the effects on the durability properties of the resulting mortar composites by studying the porosity, weight loss upon sodium sulfate attack, and ultrasonic pulse velocity (UPV). Specimens with a diameter of 50 mm and height of 100 mm were examined. The results showed that UPVmortar > UPVpastes. Increasing the amount of cement led to a decrease in weight loss for the 50-, 150-, and 250-mm slumps. The maximum weight loss (15 %) was recorded for the HVFA mortar composites comprising 80 % sand. Furthermore, all prepared samples displayed adequate resistance to sulfate (weight loss was below 16 %). Based on the dry unit weight values, all the final products, aside from that comprising 20 wt. % fly ash and 80 wt. % cement, can be considered as a lightweight material, at ∼12.58 kN/m3, and can satisfactorily be used in the manufacture of lightweight aggregates and semi-isolating materials.

Prediction of Swelling Potential and Pressure in Compacted Clay

In this study to predict free swelling potential and pressure in compacted clay, simple relationships are proposed. Three different clay samples were prepared with initially at constant dry unit weight and varying water contents and at constant water content and varying dry unit weights by standard compaction. In the experiment part, the free swelling technique was used. Values of free swelling potential and pressure were measured using the oedometer analysis. Analyses were repeated at least two times. To predict free swelling potential and pressure, the multiple regression analyses were performed for the different values of dry unit weight, initial water content and plasticity index of three samples. The proposed relationships and the equations in the literature were compared with the test results of these samples in optimum water content and maximum dry unit weight and of another compacted sample for the known values of the dry unit weight, initial water content, and plasticity index. The comparison was also done with a relation given in the literature. The results found that the estimated values of swelling potential and pressure obtained from the proposed relationships were in consistent with the measured ones.

English

  In this study, Schmidt hammer rebound (HR) values of fine to medium-grained sandstone were measured to investigate the anisotropy effect on strengthaccording to thickness. The highest HR was measured from the thickest (132 cm) bed, with an average value of 43, while the lowest was measured from the thinnest (8 cm) bed, with an average value of 35. The variation of HR is determined as 23%. Similarly, the average of highest uniaxial compressive strength is 77.73 MPa, while the lowest uniaxial compressive strength (UCS) is 66.13 MPa. The variation of UCS is fixed as 17.5%. The porosity and dry unit weight of sandstone are relyingon the internal characteristics (such as orientation-size-ratio of grain). Because of similar internal characteristics, these properties show small and irregular changes. The dry unit weight values show 1.77% variation, while porosity 0.61%. So they have small importance on bed strength. Semi-continuous bedding cause additional discontinuities. Moreover, application distance of the Schmidt hammer from the discontinuity surfaces highly affects rebound values. Closeness of single discontinuity surfaces (30 cm) cause more than 10% increase in HR, while two discontinuity surfaces cause more than 20% variation when distance from the junction of surfaces is roughly 42 cm. This study clearly indicates that bedding and other anisotropic features can cause significant changes in strength.   Key words: Schmidt hammer, sandstone, bed thickness, discontinuity surface.

Preparation of Residual Soil Samples by Using Modified Method

The purpose of this study was to establish an alternative method in preparing the residual soil samples for laboratory tests. The soil was compacted by using the modified method in order to get the desired values of dry unit weight that was equivalent to the values obtained from standard compaction method. The advantage of using this method was that, due to its larger size, more samples could be taken and tested under the same compaction condition and the mould could be directly mounted on the shaking table with the addition of the air bags to avoid the occurrence of boundary effects. The soil was compacted in a 300mm x 300mm x 300mm mould by using the vibrating hammer. The results of this study showed that the average dry unit weight value of 13.4 kN/m3, 13.6 kN/m3 and 13.7 kN/m3 obtained from 5 rounds/layer, 6 rounds/layer and 7 rounds/layer of compaction of modified method, was equivalent to about 92%, 93 % and 94% of maximum dry unit weight obtained from standard compaction method, respectively.