Unit Weight Research Articles

Applying the Porosity-to-Cement Index for Estimating the Mechanical Strength, Durability, and Microstructure of Artificially Cemented Soil

Fine, expansive, and problematic soils cannot be used in fills or paving layers. Through additions to these soils, they can be converted into technically usable materials in civil construction. One methodology to make them viable for construction is through a stabilization process. Nevertheless, current methodologies regarding dosage based on compaction effort and the volumetric amount of binder used are unclear. Thus, this research describes cement-stabilized sedimentary silt's strength and durability properties from Curitiba (Brazil) for future application in paving. Splitting tensile strength, unconfined compressive strength, and loss of mass against wetting and drying cycles (W-D) were investigated in the laboratory utilizing greenish-gray silt (originating from one of the Guabirotuba Formation layers, Paraná) and high-early strength Portland cement- ARI (CPV). Utilized were cement concentrations (C) of 3, 5, 7, and 9%, molding dry unit weights (d) of 14, 15, and 16 kN/m3, curing periods (t) of 7, 14, and 28 days, and constant moisture content (w) of 23%. With an increase in cement concentration and curing time, the compacted mixes demonstrate an increase in strength, an improvement in microstructure, and a decrease in accumulated mass loss (ALM) and initial porosity (η). Using the porosity/volumetric cement content ratio (η/Civ), the lowest amount of cement required to stabilize the soil in terms of strength and durability was determined. The porosity/cement index provided an appropriate parameter for modeling the mechanical and durability properties, and a unique equation between the strength/accumulated loss of mass and the porosity/binder index was obtained for the curing times studied. Lastly, C = 5% by weight is the minimum acceptable amount for prospective subbase soil application. Doi: 10.28991/CEJ-2023-09-05-02 Full Text: PDF

The Effect of Type of Fiber in Density and Splitting Tensile Strength of SIFCON

SIFCON is characterized as a construction material of high ductility and very high strength. It is suitable for concrete structures used for special applications. However, the density of SIFCON is much higher than that of Fiber Reinforced Concrete (FRC) due to the need for a large amount of high-density steel fibers. This work examines the split tensile behavior of modified weight slurry infiltrated fiber concrete utilizing a mixture of two types of fibers, steel fiber, and polyolefin fiber. For the investigation, 30 cylinders and 15 cubes were poured. The used volume fraction (V.F) is (6 %) and the use of five series once as each type separately and once a hybrid in proportions of 2/3 polyolefin with 1/3 steel fiber and vice versa. The splitting tensile strength and the unit weight of SIFCON resulting from tests were studied. The results indicate that SIFCON produced from a mixture of 1/3 hook-end steel fibers with 2/3 polyolefin fibers achieved good results in reducing density while maintaining a high split tensile strength. It significantly decreased density by 140 kg per cubic meter and improved splitting tensile strength by 494%.

Clayshale stabilization using active natural lime to increase the shear strength of soil

Clayshale not used in construction because it is easily weathered when exposed to air and water to reduce the soil shear strength. As a result, this decline can cause geotechnical engineering problems, and clayshale needs stabilization. This study aims to determine the shear strength of clayshale by adding variations of 5%, 8%, and 11% lime. Tests carried out to obtain soil parameters include soil index and engineering properties. Based on laboratory tests, the original clayshale soil has a 33.2% liquid limit, a 6,1% plasticity limit, and a 27,1% plasticity index. Hence, clayshale soils belong to the CL(clay-low plasticity) category based on the USCS. Adding lime variations can increase the specific gravity and the optimum moisture content of the clayshale soils. Still, it can reduce the dry unit weight and the plasticity index value on clayshale soils. The triaxial test on the original clayshale soil sample obtained a cohesion(c) value of 0.20kg/cm2 and friction angle(f) of 6.38°. In contrast, the values of c and f occurred the highest increase from the original clayshale soil with the addition of 8% lime, so lime can be used as an alternative in soil stabilization because it can increase the shear strength of the soil.

Review of Ultrasonic Pulse Methods for Evaluation of Mechanical Properties of Concrete with Different Percentages of Non-sintered Hwangto at High Temperature

In this study, the effect of non-sintered hwangto on the high-temperature residual mechanical properties of concrete is analyzed. The specimens are classified as NC and HT, which are mixed with 15% and 30% non-sintered hwangto, respectively, and the W/B is set 0.33. The unit weight, compressive strength, and ultrasonic pulse velocity of the specimens heated at room temperature and at 100 °C, 200 °C, 300 °C, 500 °C, and 700 °C are analyzed, and the correlation between ultrasonic pulse velocity and residual compressive strength is analyzed. The analysis result shows that the higher the mixing ratio of non-sintered hwangto, the lower is the mass loss rate at high temperature and the higher is the residual compressive strength of HT compared with those of NC. Meanwhile, the ultrasonic pulse velocity of HT is similar to or slightly higher than those of NC in areas with high temperatures of 300 °C or beyond. Results of correlation analysis shows a difference of approximately 10.0% between the NC and the HT specimens.

Reliability Analysis on Stability of Armor Units for Foundation Mound of Composite Breakwaters

Probabilistic and deterministic analyses are implemented for the armor units of rubble foundation mound of composite breakwaters which is needed to protect the upright section against the scour of foundation mounds. By a little modification and incorporation of the previous empirical formulas that has commonly been applied to design the armor units of foundation mound, a new type formula of stability number has been suggested which is capable of taking into account slopes of foundation mounds, damage ratios of armor units, and incident wave numbers. The new proposed formula becomes mathematically identical with the previous empirical formula under the same conditions used in the developing process. Deterministic design have first been carried out to evaluate the minimum weights of armor units for several conditions associated with a typical section of composite breakwater. When the slopes of foundation mound become steepening and the incident wave numbers are increasing, the bigger armor units more than those from the previous empirical formula should be required. The opposite trends however are shown if the damage ratios is much more allowed. Meanwhile, the reliability analysis, which is one of probabilistic models, has been performed in order to quantitatively verify how the armor unit resulted from the deterministic design is stable. It has been confirmed that 1.2% of annual encounter probability of failure has been evaluated under the condition of 1% damage ratio of armor units for the design wave of 50 years return period. By additionally calculating the influence factors of the related random variables on the failure probability due to those uncertainties, it has been found that Hudson’s stability coefficient, significant wave height, and water depth above foundation mound have sequentially been given the impacts on failure regardless of the incident wave angles. Finally, sensitivity analysis has been interpreted with respect to the variations of random variables which are implicitly involved in the formula of stability number for armor units of foundation mound. Then, the probability of failure have been rapidly decreased as the water depth above foundation mound are deepening. However, it has been shown that the probability of failure have been increased according as the berm width of foundation mound are widening and wave periods become shortening.

Recycling of waste marble powder and waste colemanite in ternary-blended green geopolymer composites: Mechanical, durability and microstructural properties

The objective of this investigation was to identify the effects of curing temperature, cement clinker aggregate, waste colemanite (WCM) and waste marble powder (WMP), as well as their interaction, on the early physico-mechanical properties, microstructure, and high-temperature resistance of geopolymer composites (GC). Ground granulated blast furnace slag (GBFS), metakaolin (MK), and silica fume (SF) were employed as precursors for the production of GC. These materials were activated using a solution of sodium hydroxide (NaOH) and sodium silicate (Na2SiO3). In the fabrication of the GC, fillers such as WMP, WCM, and cement clinker aggregate (CCA) were employed. Four GC mixes were generated and cured for 8 h at curing temperatures of ambient (20 °C), 60 °C, and 90 °C. Investigations were conducted into how curing temperature, WMP, and CCA affected the GC's compressive, flexural strength, water absorption, dry unit weight, porosity, and sorptivity. The resulting mixes' performance at high temperatures was also assessed. Using SEM, microstructure investigations of GC mixes made for the study were also carried out. The obtained results indicated that the mixture M2 containing 100 kg/m3 of WMP and 750 kg/m3 of CCA exhibited the greatest compressive strength of 24.60, 55.60 and 68.80 MPa at ambient, 60 °C and 90 °C respectively compared the other GC mixtures. Moreover, the compressive strength of the M1 mixture enhanced by 190.65% and 239.56%, at 60 °C and 90 °C respectively compared to ambient-cured samples. Ambient cured mixture M4 that contains maximum WBM and minimum CCA content exhibited the strength enhancement of 54.01, 46.52 and 29.95% at 150, 350, and 550 °C respectively.

Shear strength of municipal solid waste rejected from material recovery facilities in the city of São Paulo, Brazil

The mechanical behavior of municipal solid waste (MSW) is a critical issue in environmental geotechnics, given the pollution and public health risks associated with slope failures. In Brazil, waste composition is expected to change due to the hierarchy of sustainable practices established by the National Solid Waste Policy, which aims to improve the recovery of organic and recyclable materials. Not much progress has been made since the implementation of this law; thus, its effects on the design and operation of landfills are not fully clear. This study presents and discusses compaction and shear strength parameters of dry MSW after mechanical sorting of medium and large recyclable items and shredding. The maximum dry unit weight for the standard Proctor compaction test ranged from 6.6 to 10.0 kN/m3 and the optimum moisture content ranged from 20% to 42%. Stress-displacement curves of direct shear tests showed strain hardening and shear strength parameters of Mohr-Coulomb envelopes were displacement-dependent. The friction angle ranged from 3.2° to 42.9° and the cohesion intercept ranged from 1.3 to 31.3 kPa, at a displacement of 9 mm (15% of the specimen length). These results are in line with the literature, since a high content of waste materials that proved to affect geotechnical properties, such as plastic, paper, cardboard, textile, and glass, remained after pre-treatment.

Characterization study of geopolymer concretes fabricated with clinker aggregates

Geopolymers are a new generation of building material that has recently been popular in reducing carbon emissions. As a result of its amorphous alumina-silicate-based reaction product, it has many superior properties. This study investigated the mechanical and physical properties and high-temperature resistance of ground-granulated blast furnace slag and metakaolin-based geopolymer concrete fabricated with clinker aggregates produced in a short curing time (8 h). In alkali activators, the sodium silicate to sodium hydroxide (SS/SH) mass ratios were 2, 2.25, 2.5 and 2.75. Two curing methods were used, namely ambient (25 °C) and oven curing (80 °C). The observed unit weights vary between 2275–2392 kg/m3 for the samples of the geopolymeric composites. Porosity and water absorption vary between 4.92 and 8.84% and 3.58–7.26%, respectively. The heat curing application decreased the mixtures' water absorption, unit weight, and porosity values. The compressive strength of the samples subject to ambient curing varied between 39.2 and 59.8 MPa. Withal, the samples cured at 80 °C for 8 h were between 66.9 and 112.4 MPa. The increased SS/SH ratio also increased the observed strength values. Capillary water absorption of all samples is below 0.6 kg/m2. Heat-cured geopolymers decreased capillary water absorption to 0.1 kg/m2. The weight loss after high temperature decreased as the SS/SH ratio increased. The N-A-S-H gel in the zeolitic structure was observed in SEM analysis. The FT-IR analysis visualized the carbonation in the heat-cured mixtures. As a result, over 100 MPa compressive strength values were observed with the clinker aggregates at 80 °C after 8 h of curing time. Withal, a high-temperature refractory composite was developed with the clinker aggregates. Moreover, the nuclear radiation shielding abilities of geopolymer concretes were investigated experimentally. The gamma shielding parameters of the samples were evaluated by transmission measurements in the range of 0.081–0.661 keV. Also, neutron dose measurements were performed, and the samples produced as neutron attenuator capacity was evaluated. The radiation shielding capabilities were improved slightly with increasing sodium silicate solution content.

Effect of Plasma Unit Weight and Donor Sex on Post-Donation Citrate Level: An Experimental Study on Plasmapheresis Donors

Introduction: Plasmapheresis donation is considered safe and well tolerated, although long-term effects need to be clarified. The volumes of anticoagulant (ACD-A) used are variable and depend primarily on hematocrit (HCT), total blood processed, amount of plasma collected, and donor characteristics. To elucidate the effect of the plasma unit weight setting on plasmapheresis efficiency and ACD-A distribution, we enrolled male donors undergoing a controlled apheresis process donating 700 g and 720 g in two different sessions. In parallel, we investigated a possible effect of sex, recruiting women donating 700 g of plasma. Methods: The study was conducted on men donating 720 g and (12 months later) 700 g of plasma, and on women donating 700 g of plasma. The main outcomes were pre-/post-donation delta (Δ) citrate concentration in donor plasma and ACD-A reinfused to the donor. Information concerning the annual check-up and the procedure was also collected. Intergroup comparisons (men donating 720 g vs. men donating 700 g and men vs. women both donating 700 g) and intragroup associations with donor and procedural characteristics were reported. Results: With the procedure set at 720 g, the machine processed around 44 mL more whole blood to collect 20 g more plasma, and 720 g donors received around 12 mL more anticoagulant than 700 g donors. Accordingly, Δ citrate concentration was 1.5 times higher (12 μm), with a greater variability observed for 720 g donations. Citrate concentration in the plasma unit was lower in the 720 g group, although not significantly. Comparing outcomes between women and men donating 700 g, we observed higher (and highly variable) Δ citrate and reinfused ACD-A in women, accompanied by lower anticoagulant levels in the unit. Increased Δ citrate is inversely associated with HCT and age in men and with HCT and triglycerides in women. Reinfused ACD-A correlates with HCT in women but not in men. Conclusion: Unit weight setting and sex influence an ACD-A shift from the estimated values toward an increased reinfusion to donor. In parallel, we observed an impact of age and sex on post-donation citrate metabolism. Altogether, these elements should be taken into account for the development of tailored approaches aimed at maintaining similar safety profiles for all donors using different plasmapheresis settings.

Experimental Study on Utilizing Polyethylene Terephthalate Waste as a Substitute for Coarse Aggregate in the Production of Lightweight Concrete

Concrete is a building material that consists of a mixture of aggregate and paste. Normal concrete has a unit weight of 2200 kg/m3 to 2500 kg/m3. In addition to normal concrete, lightweight concrete is also known which has a unit weight of less than 1900 kg/m3. The research was conducted to produce lightweight concrete by using aggregate from polyethylene terephthalate (PET) plastic waste as a substitute for coarse aggregate. This study used 40 cylindrical samples of 150 mm x 300 mm with variations in the use of PET aggregates of 25%, 50%, and 100% of the volume of coarse aggregate. The results show that the use of PET aggregates produces concrete with a decrease in compressive strength of 26%–39% and a decrease in water absorption of 2%–32% from normal concrete. Ultrasonic Pulse Velocity (UPV) testing showed that the concrete with PET aggregates had a lower wave propagation velocity compared to normal concrete. Moreover, Schmidt hammer and splitting tensile test showed that concrete with PET aggregates had lower rebound number and split tensile strength compared to normal concrete. PET substitution percentages of 25% and 50% resulted in unit weights of 2218 kg/m3 and 2102 kg/m3, respectively, which rule out the use of lightweight concrete. However, 100% PET substitution has a unit weight of 1855 kg/m3 with a compressive strength of 14.16 MPa, which can be categorized as moderate structural lightweight aggregate concrete.

The surface bearing capacity of a strong granular layer on weaker sand

Stronger granular layers are often placed as working platforms over weaker sand subgrade. The design of a working platform involves the calculation of a two-layer bearing capacity under rectangular loading. Existing design methods are either overly simplified, based on infinitely long strip loads and validated by a small number of small-scale 1g model tests, or rely on numerous or empirically derived charts that are difficult to use or implement into design software. In this paper a new and highly practical design method is proposed in which the bearing capacity is determined simply from the shear strengths and unit weights of the two soil layers. The method was derived from extensive finite-element analysis and finite-element limit analysis (FELA) parametric studies in both plane strain and axisymmetric geometries. It was validated against published physical model tests, other FELA analyses and existing design methods. It can be applied to all rectangular shape ratios with dry and saturated layers.

Predicting the behaviour of self-compacting concrete incorporating agro-industrial waste using experimental investigations and comparative machine learning modelling

This study examines the effects of the silica fume (SF) and fly ash (FA) together as a binary replacement of cement on the behaviour of self-compacting concrete (SCC) using experimental investigation and application of various machine learning (ML) models developed for this study. The SF and FA were used in combination of 25/75, 50/50, 75/25 proportions with 5%, 10% and 15% cement replacement, respectively, at 3,7, 14- and 28-days curing. In first phase, unit weight, workability, compressive strength (CS) and dimensional stability of the sustainable SCC were investigated through experimental testing. The experimental results revealed that the fresh properties of SCC, at all replacement levels and combination of SF and FA, were remained within the range of the standard values. At the same replacement percentages, the combination of SF/FA of 50/50 was more effective than the other two combinations of SF/FA at the same dosage levels and at all the ages of SCC. The CS was improved by 17% at 15% replacement level when SF and FA were blended at the combination of 50/50. The second phase of this study differentiate this research from the past literature. The collection of modelling algorithms used in this study have never been applied to this kind of data to provide a comparative analysis over two different datasets. The ML modelling was performed using Neural Network Regression (NNR), Decision Forest Regression (DFR), Linear Regression (LR) and Bayesian regression (BR). Initially, the dataset achieved through the experimental investigations performed in this study was modelled. The models efficiently predicted the CS of sustainable SCC when compared with experimental results. Later, the dataset available in the literature was also used to verify the accuracy of the proposed ML models. Based on the findings, the best performing algorithms were LR and NNR, both with R2 = 0.9, that highlights the optimum and enhanced performance of the ML modelling over other numerical methods.

Effect of dehydrogenation depth on cyclic hydrogen desorption properties of V40Ti25.5Cr26.5Fe8 alloy

The cyclic stability of hydrogen absorption and desorption is an important indicator of hydrogen storage alloy. The decay mechanism was roundly investigated by controlling the depth of dehydrogenation (DOD) of the V40Ti25.5Cr26.5Fe8 alloy during the process of hydrogen ab/desorption cycles. The V40Ti25.5Cr26.5Fe8 alloy exhibits the hydrogen desorption capacity of 2.36 wt% at 323 K in the first cycle. After 30 cycles, the decay rate of the hydrogen desorption capacity is only 4.37 % at 40 % DOD, but rises to 8.74 % at 100 % DOD. The hydrogen desorption capacity (C), plateau pressure (P) and micro-strains (S) all show an “acceleration followed by slowing” exponential variation trend with the increase of cycle number (x). Additionally, any two of C, P and S show linear correlation. It is considered that the micro-strains in the crystal lattice is the main factor for the decay of the hydrogen desorption capacity and the plateau pressure. On the premise of ensuring the valid hydrogen storage capacity to meet the requirements of the application, properly reducing DOD per cycle can effectively reduce the micro-strains accumulation and cell volume expansion, thus improving the cyclic stability of the alloy. Moreover, the application of this alloy in a fuel cell bicycle was investigated, and the total range and mileage per unit weight of the alloy are up to 100.8 km and 15.7 km/kg, respectively. Compared with the lead-acid battery, lithium-ion battery and LaNi5-based hydrogen fuel cell, the V-Ti-Cr-Fe-based fuel cell shows significant advantages.

Mechanism determination on the interactive effects between host immunity and gut microbiome to resist consecutive hydrogen sulfide inhalation of laying hens

The study aims to investigate the underlying mechanism of the interactions between intestinal microbiota and host immunity-related parameters in response to H2S inhalation of layer hens. A total of 180 healthy 300-day-old Lohmann pink hens with similar body weight were randomly allotted into the control (CON) and the hydrogen sulfide (H2S) treatments for an 8-wk-long feeding procedure. Productive performances, antioxidant capacities, immunity-related parameters, blood metabolites, and cecal microbiota were measured to determine the physiological and gastrointestinal responses to H2S treatment. Results showed that feed intake, egg production, eggshell strength, Haugh unit, and relative yolk weight significantly declined under H2S treatment compared with CON (P < 0.05). Antioxidant and immunity-related parameters showed that glutathione peroxidase, IL-4, and TNF-α contents significantly decreased, whereas contents of IL-1β, IL-2, and IL-6 significantly increased after H2S treatment (P < 0.05). Further metabolic results showed H2S treatment upregulated 2-mercaptobenzothiazole, D-glucopyranuronic acid, deoxyuridine, cholic acid, and mimosine, etc., which mainly enriched into the pyrimidine metabolism, beta-alanine metabolism, valine, leucine, and isoleucine biosynthesis, and pantothenate and CoA biosynthesis pathways. Meanwhile, aceturic acid, 9-oxodecenoic acid, palmitoleic acid, lauric acid, linoleic acid, oleic acid, and valeric acid mainly contributed to the downregulated metabolites, and enriched into the biosynthesis of unsaturated fatty acids, amino sugar and nucleotide sugar metabolism, tryptophan metabolism and linoleic metabolism. Moreover, H2S treatment significantly proliferated the relative abundances of Faecalibacterium, Ruminococcaceae, and Streptococcus, while decreased Prevotella, Lactobacillus, Bifidobacterium, Clostridium, and Campylobacter (P < 0.05). The altered bacteria were functionally enriched in the carbohydrate metabolism, amino acid metabolism, and metabolism of cofactors and vitamins pathways. H2S treatment also significantly downregulated the expression of ZO-1, Claudin 4, and Claudin 7 (P < 0.05). In summary, intestinal microbial communities altered significantly to make proper adaptations in interacting with the host immune systems through the immunity-related metabolites secretion, and epithelial tight-junction-related genes expressions, purposely to regulate the productive performance under hydrogen sulfide inhalation.

Investigation of mechanical and insulation properties of Sorel cement binding light concrete

In this study, some mechanical and insulation properties of light concrete with Sorel cement were investigated by using Sorel cement, which is an alternative to cements used in the market. In addition, samples were produced by substituting some additives separately into the Sorel cement mixtures in order to evaluate the waste materials in the inactive state and to improve some of the mechanical and insulation properties of the Sorel cemented samples. In this study the flexural and compressive strengths, thermal conductivity, thermal resistance, ultrasound transition velocity, unit weight, water absorption and apparent porosity, bulk expansion, alkali silica reaction (ASR), surface area analysis (BET) and microstructures of samples were investigated. The reference samples were Sorel cement (SC), the other samples were made of mixtures of SC, pumice (P), air-entraining additive (AEA), Afşin Elbistan fly ash (AEFA), wood and corncob shavings (WS, CS). According to the findings, it can be said that while the flexural and compressive strength of the lightweight aggregate samples decreased compared to the reference sample, there were improvements in heat and sound insulation properties. The determined values differed according to the type and ratio of lightweight aggregates. It was observed that the increase in the ambient temperature of the SC samples had a positive effect on the flexural and compressive strength values up to 100 °C, while it caused a decrease in the strength values after a certain temperature. It was seen that the strength values of SC samples kept in water decreased due to the cracks formed. The results showed that the samples produced with Sorel cement had high strength. Sample strengths produced with pumice used as aggregate are higher than those with wood chips and corncob sawdust. It was determined that Sorel cement could not be used together with AEFA because the samples were shattered. No incompatibility was observed with AEA and WS additives either; however, the strength value was low in those with CS added.

Proposed Method for the Design of Geosynthetic-Reinforced Pile-Supported (GRPS) Embankments

Soft soils with unfavorable properties can be improved using various ground-improvement methods. Among these methods, geosynthetic-reinforced pile-supported (GRPS) embankments are considered a reliable option for challenging ground conditions and time-bound projects. Nevertheless, the intricate load transfer mechanism of the GRPS embankment presents challenges due to the multiple interactions among its components. To overcome the limitations of current design methods that do not fully account for all interactions, a simplified design method has been developed for GRPS embankments. This method uses numerical analysis to predict pile load efficiency and geosynthetic tension. In this study, a validated model of the GRPS embankment, which incorporates certain simplifications for design purposes, was adopted. Based on this simplified model, a database of load efficiency and geosynthetic tension was collected to derive the design equations. The design method employed six parameters, namely, pile cap width, pile spacing, embankment height, oedometric modulus of the subsoil, geosynthetic stiffness, and embankment fill unit weight. The design process utilized Plaxis 3D and Curve Expert software. The results showed reasonable agreement between the findings of the proposed design method and the field measurements of eight case studies.

Behavior of electrical resistivity against different soil properties

Any construction must be designed and built after the subsurface soil has been determined. The subsurface qualities of the soil are rendered by expensive, time-consuming, and risky operations, which on the other hand, raise the project's capital expenditure while also getting the engineering properties of distinct soil materials. Standard sampling techniques for boreholes are used for the assessment of the engineering properties of soil. But it is pretty costly, intrusive, and takes too much time. Therefore, a different method of determining the subsurface soil parameters is required. An alternate strategy for borehole sampling is to use geo-electrical techniques, such as electrical resistivity (ER). This research aims to ascertain the relationship between the electrical resistivity of various soils and their engineering characteristics. Without using the borehole sample method, appropriate correlations will aid in determining the subsurface soil parameters. Good correlations are obtained for the relationship of electrical resistivity against friction angle, cohesion and moisture content with an R2 value of 0.79, 0.41 and 0.66, respectively. The correlation of resistivity with unit weight showed a weak relationship due to typical soil behavior.

Behavior of lightweight-foamed soil reinforced by waste fishing net and its design guideline

Lightweight-foamed soils are promising new geomaterials that can be used when the lateral earth pressure and settlement need to be reduced. Lightweight-foamed soil typically consists of dredged soils, cement, and air foam. Extra additives could be used to enhance the performance of lightweight-foamed soils, and waste fishing nets are materials that can be used for tensile reinforcement of geomaterials. In this study, a waste fishing net was used in lightweight-foamed soil, and several laboratory tests were conducted to optimize the composition of lightweight-foamed soils in terms of water content, cement ratio, air foam ratio, and net type. A dredged soil in-situ was sampled to use and a waste fishing net was retreated for laboratory experiments. The waste fishing net cut into pieces and some were unthreaded. A form generator was used to produce air foam. The comprehensive evaluation of lightweight-foamed soil reinforced with waste fishing net was performed in terms of the sample preparation time, rheology, unit weight, and strength associated with lightweight-foamed soils. The results showed that lightweight-foamed soils reinforced with waste fishing net provided a peak strength similar with unreinforced one, but having higher critical strength. Finally, the normalized factor (NF) was used to develop a design guideline for lightweight-foamed soils.

Probability of unsatisfactory performance of monopile foundations for offshore wind turbines considering variations in seabed properties

Safe design of monopiles for Offshore Wind Turbines (OWT) requires an accurate estimation of the foundation soil material properties. Uncertainty in soils is mainly due to their inherent variability which involves various spatial and temporal processes they have been exposed to over their natural geological process. The limited amount of information from geotechnical investigations in the seabed, considering the size of OWT farms, adds to the uncertainty. Commonly used deterministic design approaches idealize soil layers by assigning average values to the mechanical soil properties and make use of empirical correlations that can significantly differ from offshore conditions. Probabilistic design approaches have been suggested in the literature to account for the effect of uncertainties on the foundation’s performance by applying a coefficient of variation (COV) to soil properties. Such methods include theoretical investigations by applying selected COV values to predetermined mean CPT profiles for sands and undrained shear strength for clays. This study calculates the probability of unsatisfactory performance, Pfsys, of monopiles in sands by implementing variation in friction angle and unit weight using current API and DNV-GL design guidelines. Monte Carlo Simulation is employed to generate random fields using lognormal, normal, and uniform distributions. Pfsys is presented for a case study found in the literature and a design exercise for which local COV for the Belgian coast is also proposed.

ОЦЕНКА ВЛИЯНИЯ ПРИМЕНЕНИЯ БИОПРЕПАРАТОВ В ПЕРИОД ВЕГЕТАЦИИ НА МИКРОБИОМ СЕМЯН ЯРОВОЙ ПШЕНИЦЫ

An assessment is made of the effect of spraying plants with biological products on the total microbiome of seeds of a new crop. The studies were carried out on three varieties of spring wheat of domestic breeding - Yoldyz, Burlak and Ulyanovsk-105. Preparations based on strains of endophytic bacteria isolated from seeds of spring wheat (Bacillus mojavensis PS17, Bacillus velezensis KS25) and spring barley (Bacillus velezensis KS31, Bacillus subtilis KS38) were used as biological preparations. The treatment of spring wheat crops was carried out in the phase of entry into the tube using the biological product consumption rate of 1.0 l/ha. The impact of treatments on the fungal and bacterial microbiome was assessed using quantitative PCR methods with the determination of the total (total) DNA of microorganisms per unit weight of seeds. In most cases, the use of treatment with endophytic bacteria reduces the amount of total micromycete DNA on seeds. Among the studied isolates, the Bacillus subtilis KS-38 strain was especially distinguished, which provided a significant (7.7-11.1 times) decrease in this indicator in all varieties. Bacillus mojavensis PS-17 had a significant effect (a decrease of almost 47 times) on the Ulyanovska 105 variety, and Bacillus velezensis KS-31 on the Burlak variety. On varieties Yoldyz and Ulyanovska 105, the most significant decrease in the total DNA of micromycetes was noted for endophytes obtained from spring wheat seeds (Bacillus mojavensis PS-17, Bacillus velezensis KS-25), and on variety Burlak, endophytes from spring barley seeds (Bacillus velezensis KS-31 and Bacillus subtilis KS-38). The decrease in the total DNA of micromycetes in the experiments was due to the use of the studied biological products and, to a lesser extent, varietal characteristics. For the bacterial microbiome, there were strong differences between varieties. A significant increase in the total DNA of bacteria in all studied varieties was in Bacillus mojavensis PS-17 and Bacillus velezensis KS-31. The variety (29.9%) made the greatest contribution to the variability in the content of total bacterial DNA in seeds, and the contribution of biological preparations was lower (25.5%). In the experiments, no correlation was found between the indicators of the total DNA of micromycetes and bacteria in spring wheat seeds.