Water-saturated Conditions Research Articles

Research on effective pit fencing solutions for the construction of a two-level parking lot of a multi-story building

A study on the effective placement of the piles in the retaining wall of the pit was carried out. A comparison of internal forces and horizontal displacements of the retaining wall piles was drawn among three variants of their placements in the wall. The influence on the calculation results of the detailing of the soil excavation process during modeling using the Plaxis 2D was examined. Based on the research on the stress-strain state (STS) of the retaining wall piles using the spatial setting of the problem, a comparison to the problem with the flat setting was drawn. Additionally, an analysis of the bending moments and horizontal displacements in the retaining wall piles with a spatial setting of the problem was made.
 Based on the obtained results, information on the effectiveness of different variants of the pile placement in the retaining wall of the pit, as well as the convergence of the calculation results with different detailing of the excavation process modeling is presented. Also, a comparison of the values of internal forces, horizontal displacements, and the elevation of the pit bottom between flat and spatial problem settings was made. The distribution of forces between piles of the retaining wall using a spatial problem setting is presented.
 The finite element model consists of the soil base and retaining wall structure. Modeling of the base was executed using the Hardening soil model, in which the following soil characteristics are used during the calculation: γ – the specific weight of the soil in its natural state; γsat – the specific weight of the soil in the water-saturated state; c – cohesion; φ – the effective stress friction angle; ψ – dilatancy angle; E50 – stiffness for primary loading; Eoed – oedometer loading stiffness; Eur – stiffness for un-/reloading. The calculation was made using the Plaxis program complex.
 Today, the effective and the most rational way of retaining wall design during the construction of buildings and structures with underground parts is significant. A successful choice of the construction of the excavation fencing not only ensures the reliability of the construction but also allows using building materials in the most efficient way. In addition, the choice of the method of the problem definition and its detailing are important factors when approaching the modeling process of similar problems, as they affect the accuracy of the obtained results, the degree of labor-intensiveness, and the time spent on the calculation.

Effect of Hydrothermal Curing on the Hydration and Strength Development of Belite Cement Mortar Containing Industrial Wastes

This paper describes the impact of hydrothermal conditions on the strength properties and hydration processes of belite cement mortar samples. The belite-rich binder was synthesized by sintering the initial mixture of raw materials (granite cutting waste, the silica-gel waste from AlF3 production, and natural materials) in a high-temperature furnace at a temperature of 1150 °C for 2 h. The prepared clinker consists of larnite, mayenite, srebrodolskite, ye’elimite, and gehlenite. To control hydration kinetics and optimize the hardening of belite cement mortar, the produced clinker was blended with 7.5% of gypsum. The mechanical properties were assessed by curing the standard prisms (following the EN 196-1 standard, cement/sand = 1:3, W/C= 0.67) under water-saturated conditions in a stainless steel autoclave. The curing process was performed in a temperature range of 90 °C to 200 °C at various hydrothermal curing durations (6–48 h). The results indicated that the curing conditions highly influence the compressive strength evolution of belite cement mortar and the formed mineralogy of hydrates. The highest compressive strength value (exceeded 20 MPa) was obtained at 200 °C, i.e., when the main belite cement mineral was entirely hydrated and recrystallized into 1.13 nm tobermorite. The microstructural evolution and the phase assemblage during the hydrothermal curing were determined by X-ray diffraction analysis and differential scanning calorimetry.

Accelerated mineral bio-carbonation of coarse residue kimberlite material by inoculation with photosynthetic microbial mats

Microbiological weathering of coarse residue deposit (CRD) kimberlite produced by the Venetia Diamond Mine, Limpopo, South Africa enhanced mineral carbonation relative to untreated material. Cultures of photosynthetically enriched biofilm produced maximal carbonation conditions when mixed with kimberlite and incubated under near surface conditions. Interestingly, mineral carbonation also occurred in the dark, under water-saturated conditions. The examination of mineralized biofilms in ca. 150 µm-thick-sections using light microscopy, X-ray fluorescence microscopy (XFM) and backscatter electron—scanning electron microscopy-energy dispersive x-ray spectrometry demonstrated that microbiological weathering aided in producing secondary calcium/magnesium carbonates on silicate grain boundaries. Calcium/magnesium sulphate(s) precipitated under vadose conditions demonstrating that evaporites formed upon drying. In this system, mineral carbonation was only observed in regions possessing bacteria, preserved within carbonate as cemented microcolonies. 16S rDNA molecular diversity of bacteria in kimberlite and in natural biofilms growing on kimberlite were dominated by Proteobacteria that are active in nitrogen, phosphorus and sulphur cycling. Cyanobacteria based enrichment cultures provided with nitrogen & phosphorus (nutrients) to enhance growth, possessed increased diversity of bacteria, with Proteobacteria re-establishing themselves as the dominant bacterial lineage when incubated under dark, vadose conditions consistent with natural kimberlite. Overall, 16S rDNA analyses revealed that weathered kimberlite hosts a diverse microbiome consistent with soils, metal cycling and hydrocarbon degradation. Enhanced weathering and carbonate-cemented microcolonies demonstrate that microorganisms are key to mineral carbonation of kimberlite.

Efficiency of Solar Power Generation System Application on Agricultural Automatic Drip Irrigation in Indonesia

Irrigation is one of the important components of farming producers in cultivation. Lack of irrigation water causes crop failure risk, while excess water also causes agricultural crop failure. It is necessary to regulate irrigation water to achieve technical and economic farming efficiency. This study aims to determine the efficiency of solar power generation in agricultural automatic drip irrigation. This study uses experimental research with the design of materials and research tools. Efficiency estimation uses a simple ratio by looking at the cost components of each treatment so that the value that appears becomes the final efficiency value. This study showed that automatic drip irrigation for solar power generation was more economically efficient than ordinary electricity. The use of automatic drip irrigation can save costs of Rp. 4,346,200. In addition, unlimited renewable energy support is a major advantage besides being environmentally friendly and an agricultural climate change adaptation strategy. The system’s performance on the automatic pump is running well, as seen from P1, P2, P3, P4, and P5; the pump turns on at a percentage of water ranging from 10-90% and turns off after reaching 100% water or water-saturated soil conditions. The main obstacle faced during the research was the climate problem because this research model used the solar system. This means that as long as sunlight shows its existence, the energy obtained is also perfect, but vice versa. In addition, it is still difficult for traditional farmers to carry out the operational control system, so further research is needed.

Effect of Moisture Condition of Structural Lightweight Concretes on Specified Values of Static and Dynamic Modulus of Elasticity.

The dynamic modulus of elasticity (Ed), specified by ultrasonic pulse velocity measurements, is often used, especially for concrete built into construction, to estimate the static modulus of elasticity (Ec,s). However, the most commonly used Equations for such estimations do not take into account the influence of concrete moisture. The aim of this paper was to establish this influence for two series of structural lightweight aggregate concrete (LWAC) varying in their strength (40.2 and 54.3 MPa) and density (1690 and 1780 kg/m3). The effect of LWAC moisture content turned out to be much more pronounced in the case of dynamic modulus measurements than for static ones. The achieved results indicate that the moisture content of the concrete should be taken into consideration in modulus measurements as well as in Equations estimating Ec,s on the basis of Ed specified by the ultrasonic pulse velocity method. The static modulus of LWACs was lower on average by 11 and 24% in relation to dynamic modulus, respectively when measured in air-dried and water-saturated conditions. The influence of LWAC moisture content on the relationship between specified static and dynamic moduli was not affected by the type of tested lightweight concrete.

Study on the Mechanisms of Rock Mass Watering for Rockburst Prevention in Phosphorite Mines from Laboratory Results

Owing to the continuous increase in mining depth, Yichang phosphorite mines in China have entered the field of deep mining. The frequency of rockburst disasters is increasing. In situ experience indicates that the practice of spraying water onto a working face after blasting is an effective method of rockburst prevention. In order to investigate the underlying mechanisms of rockburst prevention by watering in phosphorite mines, a series of uniaxial compression laboratory experiments was carried on phosphorite samples under dry and water-saturated conditions with an acoustic emission (AE) monitoring system. A high-speed camera was used to record the failure process and pattern of a given rock sample prior to rockburst. The effects of water on the mechanical properties and fracturing characteristics of phosphorite failure were determined. Experimental results indicate that water reduces the uniaxial compressive strength and Young’s modulus. Saturated phosphorite causes more small fragments after it fractures. A Gaussian mixture model (GMM) clustering algorithm was utilized to analyze the crack propagation patterns of rock samples during the entire process. It was determined that during the unstable crack propagation phase, the presence of water makes the shear characteristics become more obvious. Water reduces releasable strain energy which is consumed by internal damage and plastic deformation of the rock sample. Moreover, the mechanism of watering for rockburst prevention is discussed from both macro and micro perspectives. The primary reasons for this are the transfer of stress concentration zones and stress-releasing effects via microcrack propagation on the working face.

Determination of adsorption parameters in shale gas resource/reserve calculation: Case study of Wufeng Formation–Longmaxi Formation in the Sichuan Basin

In the calculation of shale gas resources/reserves, isothermal adsorption parameters are mainly determined by dry sample data at the laboratory temperature, and the regression effect of total organic carbon content (TOC) isothermal adsorption parameters is poor. Based on the physical significance of key parameters in Langmuir and Henry adsorption models, the problems in determining the isothermal adsorption parameters in the calculation of shale gas reserves/reserves are analyzed by taking the marine shale in the Upper Ordovician Wufeng Forming–Lower Silurian Longmaxi Formation in the Sichuan Basin as an example. Based on a large number of measured isothermal adsorption data, the effects of TOC, temperature and water saturation on the shale gas adsorption parameters are analyzed. The influence model of TOC, temperature and water saturation on isothermal adsorption parameters of shale gas is established, and a novel method for calculating the adsorption parameters of shale gas from under experimental conditions to original reservoir conditions is proposed. The results are obtained as follows. First, there are problems in the calculation of shale gas resources/reserves, such as poor and contradictory fitting relation between isothermal adsorption parameters and TOC, difficulty in the conversion of Van't Hoff equation, and difficulty in direct application of water saturation (Sw) in resource/reserves calculation. Second, the problem of poor direct fitting relation between Langmuir pressure (pL) and TOC is solved by integrating the Langmuir adsorption model with the Henry adsorption model and by establishing a new parameter – Henry constant a for methane adsorption capacity of shale. Third, when Sw<40%, the Langmuir volume (VL) is linearly negatively correlated with Sw; when Sw<20%, a is constant relatively; by establishing the relationship between the normalized absolute adsorption capacity and Sw (<50%) under the pressure exceeding 30 MPa, the effect of Sw on the isothermal adsorption capacity can be calculated. Fourth, the in-situ stress in the Wufeng Formation–Longmaxi Formation shale reservoir affects the adsorption capacity of shale. For shale reservoirs with the same TOC, the higher the in-situ stress, the smaller the VL and a values. Under high pressure (>30 MPa), the effect of Sw on the methane adsorption capacity of shale shows a similar trend, and the effect of water molecules on the adsorption capacity on shale pore surface is constant. It is concluded that the proposed novel method for determining the isothermal adsorption parameters of shale with different TOC, temperature and water saturation conditions provides a technical support for the accurate calculation of shale gas resources/reserves and contributes to the scientific development of shale gas industry.

THz Imaging to Map the Lateral Microporosity Distribution in Carbonate Rocks

Terahertz (THz) spectroscopy is a nondestructive tool used in many industries to analyze materials, including measuring the water content and the distribution of water in biological samples. THz time-domain spectroscopy (THz-TDS) measures the dielectric and structural properties of a sample by probing it with an ultrafast THz pulse and measuring the change in amplitude and phase. In this study, we demonstrate the use of THz-TDS imaging to quickly map lateral (i.e., two-dimensional) variations in microporosity (ϕμ) using the THz attenuation due to water in the pores after clearing the large pores via centrifugation. Three carbonate rock plugs with differing ϕ and pore-size distributions were subsampled for this study. Three water saturation states were produced for each sample: saturated, centrifuged, and dry. At each saturation state, the sample is weighed and imaged using THz-TDS to spatially map and measure ϕμ. The results show that for each sample the ϕμ obtained using THz-TDS imaging is in excellent agreement with that obtained from both mass balance and MICP. In addition, the THz-TDS maps show significant differences in the spatial distribution of the microporosity for samples having similar composition. This method provides a means to measure ϕ and ϕμ while mapping the spatial distribution of ϕμ toward improved petrophysical characterization of carbonate reservoir rocks.

A thermodynamic-based model for modeling thermo-elastoplastic behaviors of saturated clayey soils considering bound water dehydration

The non-isothermal deformation of soft mudrocks or clay soils is one of the most critical issues in energy and environmental related geotechnics. Clay-related geomaterials hold complex microstructure and mineral composition, which brings difficulty in investigating their thermo-mechanical behaviors. Previous studies pay little attention to the difference between a thermal plastic strain and the strain from clay dehydration. In this study, a new constitutive model is proposed for describing the thermo-elastoplastic behaviors of clayey soils under water-saturated condition. The effect of temperature variation and mechanical loading on elastoplastic strains and dehydration are investigated. The thermodynamics laws and the unconventional plasticity are applied to quantify the thermo-mechanical behavior. The irreversible strain is captured by using Cam-Clay plasticity and subloading yield surface concept. The dehydration strain is described by utilizing a novel method based on generalized thermodynamics approach and Helmholtz free energy function. The internal variables, and the first and second laws of thermodynamics are applied in the model. The hardening rule is established by implementing the laws of physical conservation, energy dissipation, and plastic flow. The proposed model is validated using specially designed thermal consolidation tests on laboratory prepared heavily consolidated clayey soils and some published data of clayey soils with different geological origins.

Experimental study on soil-water characteristics and strength characteristics of complete-intense weathering mudstone in seasonal frozen area.

To study the soil-water characteristics and shear strength of unsaturated complete-intense weathering mudstone, the soil-water characteristic curve of complete-intense weathering mudstone and the matric suction of mudstone samples under natural state were measured. This measurement was through a soil-water characteristic test using a pressure plate instrument. Based on the results of soil-water characteristic test, an unsaturated (saturated) triaxial shear test was carried out. Under different temperatures and confining pressure conditions, the shear strength and deformation characteristics of complete-intense weathering mudstone under natural water content and saturation conditions were investigated. The results show that the percentage of silt and clay in unsaturated complete-intense weathering mudstone in natural state is relatively high, with the mudstone having less sand, and a weak permeability and exhibiting a significant capillary phenomenon. The complete-intense weathering mudstone with a natural moisture content of 19.15% has a matric suction of 210 kPa. When the temperature is constant, the shear stress of the sample increases with the increase of confining pressure. When the temperature decreases from 0 to -20°C, the influence of confining pressure on the rock samples gradually decreases. The rock sample has the property of strain hardening during shearing. Under the same matric suction, the total cohesion increases with the decrease of temperature. At a positive temperature, the effective internal friction angle increases with the decrease of temperature. At a negative temperature, the lower the temperature, the smaller the effective internal friction angle. The test of shear strength parameters of saturated complete-intense weathering mudstone is simple and conservative. In practical engineering, the basic properties of unsaturated complete-intense weathering mudstone can be predicted by testing the shear strength parameters of saturated complete-intense weathering mudstone. The results of the study are important for better understanding the nature of unsaturated complete-intense weathering mudstone and improving the safety of engineering construction in complete-intense weathering mudstone areas.

Study on distress of airport pavement foundation and solution applied to Noi Bai international airport

The service quality and life of the runway, taxiway and apron pavement system heavily depends on the condition of its foundation, including base and/or subbase layers and subgrade. In the state of water-saturated condition, the strength of foundation would decline significantly, then inducing the downgrade of overall strength of the pavement. In the long term, the impacts from adverse environmental conditions and aircraft wheel loading will mix-up the materials of foundation layers, leading to the degradation of the original physical and mechanical properties of the original designed material. Furthermore, the accumulation of residual deformation and appearance of voids in the granular material can formulate the large holes beneath cement concrete slab. That, in turn, changes the load bearing model of the slab compared to the original design and causes the structural damage of the slab and threatens flight safety. Due to the complication of pavement foundation, the traditional treatment countermeasures usually need a long time for completion, while the airfield system often requires short and high-quality repair time. Therefore, there should be special solutions to satisfy the practical application. The article analyzes the cause, proposes the solutions for pavement foundation treatment and presents an initial application to Noi Bai International Airport. The findings of this study could be critical and significance basis for both academic and practical applications to maintain the service quality of airport construction infrastructure in Vietnam.

EFFECT OF POPULATION DENSITY AND WATER SUBSTRATE INTERFACE OF GROWTH AND YIELD RED LETTUCE

One of the green leafy vegetable plants that have good value and content for consumers is lettuce. Red lettuce (Lactuca sativa Var. Red rapids) is a type of leaf lettuce, this type of lettuce has leaves that are red, wide, thin, and clustered and look curly. Efforts to get maximum crop yields are by regulating plant populations so that they are efficient. This study aims to determine the effect of population and water level on the growth and yield of red lettuce. The method used in this study was a factorial randomized block design. The main factor was the population (P), which consisted of 3 treatments, namely 1 plant/pot (P1), 2 plants/pot (P2,) and 3 plants/pot (P3). The second factor was the water substrate interface (WSI), which consisted of 3 treatments, namely 1 cm (WSI1), 2 cm (WSI2), and 6 cm (WSI3). The results showed that red lettuce gave a different response to each population. (P2) produces the highest average number of plant leaves, this shows that plants with a population of 2 plants/pot are quite efficient in utilizing space so that plants grow well, characterized by a higher number and leaf area. The water interface contact area with a depth of 6 cm produces a root length value that is smaller than 1 cm and 3 cm. In a state of water saturation, roots cannot develop properly so that root growth becomes stunted.

Surface water in C-S-H: Effect of the temperature on (de)sorption

Thermal desorption is a critical process in cement-based materials subjected to temperature increase. C-S-H surface is the most likely surface available for thermal desorption in these materials. Here, we investigate surface thermal desorption in C-S-H. Molecular simulations are used to get systems equilibrated under two drained poromechanical conditions: liquid water-saturated and constant partial fluid pressure conditions. Suited fluctuation formulas are deployed to acquire properties at the adsorbed layer level. We show that thermal desorption is driven by thermal expansion of water and liquid-to-vapor phase transition (leading to cavitation). The potential energy, isochoric specific heat capacity, molar incremental enthalpy, bulk modulus, coefficient of thermal expansion, surface tension, and pressure tensor components exhibit a marked dependence on the distance from the C-S-H adsorbing surface. Parameters usually adopted in sorption models (e.g., BET family) such as monolayer thickness and adsorption energy need to be revisited using molecular scale evidence.

Evaluating Pore Structure of Shale Reservoirs through Pore Space Multifractal Characterization

Characteristics of pore structure are crucial to oil exploration and development in shale reservoirs, but practical evaluation of shale pore structure remains a longstanding challenge. In this study, based on nuclear magnetic resonance transverse relaxation time (T2) spectra under water-saturated and irreducible conditions, total pore space and moveable fluid space were skillfully determined. Meanwhile, multifractal spectra were used to characterize T2 distributions of total pore space and movable fluid space. The results show characteristic parameters of high probability measure areas of multifractal spectra (multifractal parameters) have strong negative correlations with T2 geometric mean value, and average radii of pore and throat increase with a decrease in the multifractal parameters, indicating the shale reservoirs with low values of the multifractal parameters may have good pore structure. Moreover, clay mineral content has strong positive effects on the multifractal parameters. In contrast, (quartz+feldspar) mineral content negatively influences on the multifractal parameters. Finally, new accurate models for permeability estimation in core scale and well-logging scale of shales are both proposed based on the multifractal parameters, which are also applicable for the other reservoirs. Overall, this study is important and timely for evaluating pore structure and predicting permeability in shale reservoirs.

Effect of initial water saturation on the performance of fracturing fluids with and without polyallylamine under simulated EGS conditions

Objectives/scopeStimuFrac (US Patents 9,873,828 B2 and 9,447,315 B2), a CO2-reactive polymer aqueous solution [polyallylamine (PAA) 1wt% in water] combined with CO2, can potentially be used as a less water-intensive fracturing fluid for enhanced geothermal systems (EGS). Our previous results show that in hot dry rock (HDR), PAA/CO2 fracturing fluids outperformed other fluids such as water, CO2, and CO2/water in generating large fractures with less fluid consumed. The objective of this work is to investigate the effect of initial water saturation on the performance of StimuFrac by conducting hydraulic fracturing tests with ½ foot cubic rock samples held under representative EGS stress/temperature conditions and by using cyclic injection strategies (under constant injection rate). The resulting fracture hydraulic conductivities, breakdown pressures, and volumes of fluids required are compared. Methods/procedures/processTo simulate geothermal reservoir conditions, in all tests, the rock sample was held under triaxial confinement and at 200 °C, and different volumes of water were initially injected into the rock sample before any fracturing processes were initiated. For the single-cycle PAA (or water) alternating CO2 (PAG or WAG) injection fracturing experiments, one complete cycle consisted of two steps: (1) injecting a PAA slug (or water slug) followed by (2) injecting CO2 to initiate and propagate the fracture. For experiments involving multiple injection cycles, the CO2 injection pressure is increased until it peaks and begins to decline (indicating fracture initiation at this moment), and then continued being injected for another 30 s to propagate the fracture. Then, these two-step cycles [injection of PAA (or water) followed by CO2 injection (up to 2–4 mL/min)] are repeated. Applications/significance/noveltyThe results of this study suggest that water saturation significantly affects the fracturing fluid transmission into the rock pore space, thus affecting fracture initiation and propagation. In this study, fracturing tests via a single injection cycle or multiple injection cycles were performed. When the rock samples are split in half following testing, it is evident that fracture propagation is considerably restricted under high water saturation conditions (where a three-day initial water injection was conducted) in comparison to stimulation experiments carried out in hot and dry rock. The fractures propagate less than 1/3 of the distance from the wellbore to the outer rock surface, and in some cases, no fracture is generated. This may be caused by leak-off dominating the fracturing process and the fluid injection rate is insufficient to overcome leak-off, even under high injection rate conditions. Additionally, CO2 could be leaking off into the wellbore annulus and this may be making it more difficult to generate sufficiently high-pressure gradients away from the near-wellbore region. Under low water saturation conditions (dry rock or after 1-day initial water injection), PAA/CO2 consistently generated significantly larger fractures compared with the other fluids. CO2 generated large fractures only in the hot dry rock and only when using high injection rates, though data variability is high.

The role of porosity in the dynamic disturbance resistance of water-saturated coal

Porosity significantly affects the dynamic response of water-saturated coal and the safety of coal mine engineering in water-rich areas. For mastering the dynamic response of water-saturated coal to the porosity, this study used the coal with four levels of the porosity for dynamic tests. In this process, the dynamic compressive tests were operated on these coal specimen in both of water saturation and dry states, and the reduction factor of dynamic mechanical parameters of the coal in water-saturated state to these in dry state were focused to eliminate the effect of self dynamic properties of the coal. The results indicate that the dynamic mechanical properties non-linear positively correlate with the porosity, and its sensitivity to porosity gradually weakens as with the increase of the porosity. This effect is intuitively expressed in the dominant fracture propagation features recorded by a high-speed camera, and microscopically attributed by the size and number of microfractures around the dominant fracture. The dynamic stress intensity factor model of the dominant fracture was further established with consideration of total cohesive force for the equivalent particle on the fracture surface. It well reveals the effect mechanism of porosity on the meso-deterioration and macroscopic mechanical properties of the coal around the roadway. On this basis, the applicable conditions and suggested methods were put forward to improve the dynamic stability of water-saturated coal with various porosity.

Petrophysical Acoustic Characterization of Weathered Granite: A Case Study of Mesozoic Granites in the Coastal Area of Fujian Province, China

In recent years, with the exploration and development of granite buried-hill oil and gas reservoirs, petrophysics research has played an important role in the study of reservoir characteristics and fluid identification. Through analysis of the relationship between the fluid-bearing petrophysical parameters and the reservoir, the seismic response changes caused by reservoir fluid changes can be determined. Mesozoic granites in the coastal area of Fujian Province in eastern China were investigated as the research object of this project. The mineral composition, density, porosity, P-wave velocity, and S-wave velocity of the granite were measured and analyzed by X-ray diffraction, rock density, rock porosity, and rock acoustics methods. Therefore, the granite’s petrophysical properties, fluid response characteristics, and gas sensitivity parameters were analyzed. The result of the study shows that the granite is predominantly monzogranite. According to the type of reservoir space assemblage, the samples can be divided into two types: those containing fracture-dissolution pores and those containing only dissolution pores. All the samples were characterized by medium to high densities and low to extra-low porosity. There was a linear correlation between the P-wave velocity and S-wave velocity under gas and water-saturated conditions. Factors such as P-wave to S-wave velocity ratio, Poisson’s ratio, Lame coefficient, and other parameters of the samples were analyzed, and the threshold values that distinguished the water and gas-saturated states of the samples were measured and determined. In addition, there were negative correlations between the P- and S-wave velocities and porosity. The sensitivities of the petrophysical parameters to the gas capacity from high to low are Ip2 − 2.03 Is2, λ − 0.03 μ, λ, λ/μ, E − 2.03 μ, σ, K/μ, K, Ip, Vp/Vs, Vp, E, μ, Vs, and Is. For granite-buried hill reservoirs, the variation ranges of the parameters, such as the density, porosity, and P-wave velocity, of the fracture-dissolution pore granite samples were larger than those of the dissolution pore samples. The bulk parameters (Ip, Vp, K, λ) and combination parameters (Ip2 − 2.03 Is2, K/μ, λ− 0.03 μ, E − 2.03 μ, λ/μ) of the dissolution pore samples were more sensitive to the gas capacity. The results of this study provide a basis for the geophysical identification of granite-buried hill reservoirs.

Environmental factors affecting rapid shear in fibers from the passage of a bullet

In forensic casework, examination of garment damage can provide insight into the mechanism of the specific cause of fiber failure. Different methods of damage impart differing physical characteristics on individual fibers. These alterations are determined by a multitude of factors, among them increased temperature of affected fibers. The process of rapid shear occurs in thermoplastic materials following high-speed impact. It results in distinct features caused by excessive heat generated through the interaction, which is unable to dissipate at a rate that would leave the fibers unchanged. Rapid shear characteristics can be differentiated from other fracture patterns through non-destructive microscopical methods and with a minimal sample size. Fabric samples were shot under heated, chilled, and water-saturated conditions, using ammunition of varying velocities. Analyses performed on the defects were conducted using stereomicroscopy, polarized light microscopy and scanning electron microscopy. Globular-shaped fiber ends, characteristics attributed specifically to rapid shear, were observed in all nylon samples. Through this study, it was determined that the environmental conditions employed did not affect fiber end changes associated with rapid shear.

CORROSION BEHAVIOR OF SS304 IN HYDROGEN CHLORIDECONTAINING ENVIRONMENTS

The corrosion behaviour of stainless steel SS304 was investigated in three major aqueous environments, namely dry, water-saturated and free-water conditions and in two different methanol environments, namely dry and watersaturated environments with 99% methanol +1% water. The sulfuric acid and sodium chloride reaction generated hydrogen chloride gas in all the experiments. An inert carrier gas such as argon pushed the hydrogen chloride gas to flow over desiccants to make the latter dry. The dry hydrogen chloride gas would then flow into the second flask to which a pre-weighted stainless-steel specimen was exposed at ambient conditions for 48 hours. The specimen was retrieved and subjected to the surface and chemical analysis using Scanning Electron Microscopy (SEM)/EDAX. The presence of chloride would affirm the adsorption of chloride ions on the metal surface and vice versa. The specimen was then weighted to determine the corrosion rate. The results suggested that stainless steel would not corrode in dry hydrogen chloride gas. However, when saturated with moisture, its corrosion rate would increase by about one order of magnitude. In a free-water environment, the corrosion rate would triple. Hydrogen chloride gas would react with moisture or water, turning it into hydrochloric acid. Hydrochloric acid is a reducing acid that attacks the Cr2O3 layer, leading to general and/or localised corrosion. The presence of methanol increased the corrosion rate of stainless steel by a factor of three to four.Keywords: methanol, stainless steel, localised corrosion, methyl chloride

Strontium isotopes trace the dissolution and precipitation of mineral organic carbon interactions in thawing permafrost

Interactions between minerals and organic carbon (OC) in soils are key to stabilize OC and mitigate greenhouse gas emissions upon permafrost thaw. However, changes in soil water pathways upon permafrost thaw are likely to affect the stability of mineral OC interactions by inducing their dissolution and precipitation. This study aims to assess and quantify how mineral OC interactions are affected by dissolution and precipitation in thawed relative to unthawed layers. We hypothesize that a change in the radiogenic strontium (Sr) isotopic ratio (87Sr/86Sr) involved in mineral OC interactions upon changing water saturation conditions implies a destabilization of the mineral OC interaction. We quantified mineral OC interactions using selective extractions in soils facing gradual thaw (Eight Mile Lake, AK, USA) and in sediments with a thawing history of abrupt thaw (Duvanny Yar, Russia), and we measured the 87Sr/86Sr ratio of the selective extracts targeting the Sr associated to mineral OC interactions. Firstly, for water saturated layers with a higher proportion of mineral OC interactions, we found a difference in the 87Sr/86Sr ratio relative to the surrounding layers, and this supports the preservation of a Sr “stable” pool in these mineral OC interactions. We estimated that a portion of these mineral OC interactions have remained undissociated since their formation (between 4% and 64% by Sr isotope mass balance). Secondly, we found no difference in 87Sr/86Sr ratio between layers accumulating Fe oxides at redox interfaces regularly affected by water table changes (or upon thermokarst processes) relative to surrounding layers. This supports the dominance of a Sr “labile” pool inherited from processes of dissolution and precipitation of the mineral OC interactions. Thirdly, our estimations based on a Sr isotope mass balance support that, as a consequence of permafrost thaw, a larger proportion of Sr from primary mineral weathering (>80%) controls the Sr in mineral OC interactions in the saturated zone of deeply thawed soils relative to poorly thawed soils (∼50%). In conclusion, we found that the radiogenic Sr isotope method, applied for the first time in this context, is promising to trace dissolution-precipitation processes of mineral OC interaction in thawing permafrost.