Influence Of Water Saturation Research Articles

Influence of Water Saturation on Dynamic Tensile and Compressive Behaviors of Concrete

Influence of Water Saturation on Dynamic Tensile and Compressive Behaviors of Concrete

Acoustic emission and splitting surface roughness of sandstone in a Brazilian splitting test under the influence of water saturation

Water weakens rock masses, which induces a series of engineering geological hazards. In this study, Brazilian splitting and acoustic emission (AE) experiments were conducted on sandstone with different saturation levels (0%, 25%, 50%, 75%, and 100%), and the effect of saturation on the AE and fracture characteristics was investigated. Meanwhile, nuclear magnetic resonance (NMR) test was used to analyze the water absorption and distribution characteristics of the samples with different saturation. Three-dimensional (3D) morphological scanning and scanning electron microscopy (SEM) were performed to analyze the roughness of the splitting surface. The tensile strength of rocks decreased from 3.05 MPa to 0.98 MPa with a moisture content from dry to saturated conditions, which obeyed an exponential function. The hardness of the sandstone decreased from dry to saturated by 56.6%, whereas the plasticity of the high-saturation sandstone increased. The AE counts and cumulative energy distribution decreased from 3880 and 39,550 to 1248 and 476, respectively, from dry to saturated conditions. Based on the Ib value, the rock damage process can be divided into three stages: fluctuation, stabilization, and decline. As the saturation increased, the initial Ib value decreased from 0.1047 to 0.0755. The development of large fractures increased during the splitting of the highly saturated rocks. With increasing saturation, the fracture surface joint roughness coefficient (JRC) and fractal dimension increased. The mean JRC increased from 5.98 to 13.6025. The unsaturated JRC showed an obvious dispersion compared with the dry and saturated sandstones. Combined with micro-macro characterization, it was found that an increase in saturation caused the rock to generate a weak structure. The damage gradually evolved from transgranular to intergranular fractures, leading to the macroscopic performance of rougher splitting surfaces and lower AE.

Influence of Water Saturation on Adsorption Behavior at Liquid-Liquid Interfaces in Unsaturated Porous Media

Adsorption reaction in unsaturated porous media is of great importance for soil and groundwater remediation. In this study, the influence of the Peclet number (Pe) and water saturation on adsorption behavior at liquid-liquid interfaces was quantitatively investigated. The pore-scale reactive transport in unsaturated porous media was directly simulated. The Navier-Stokes equations, the surface transfer and adsorption reaction equations, and the advection-diffusion equation (ADE) were coupled to obtain the flow and concentration fields. The results showed that water saturation had a significant influence on the complexity of the flow field. A nonmonotonic relationship was found between water saturation and the uniformity of the flow field. Peclet number had little influence on the maximum adsorption. On the other hand, the adsorption time showed a nearly linear relationship with the Peclet number and increased with increasing Peclet number. Additionally, a nonlinear relationship was found between water saturation and the maximum adsorption. As water saturation increased, the maximum adsorption tended to increase to a peak and then decrease. The peak of the maximum adsorption occurred at Pe = 5 , S w = 0.458 , and the shortest adsorption time was observed at S w = 0.902 . However, the difference in adsorption times for saturations of 0.458 and 0.698 was not significant and was only about 20 PV difference.

Productivity Equation of Fractured Vertical Well with Gas–Water Co-Production in High-Water-Cut Tight Sandstone Gas Reservoir

Due to the high water saturation in high-water-cut tight sandstone gas reservoirs, factors such as threshold pressure gradient (TPG) and stress sensitivity (SS) cannot be overlooked in terms of their impact on seepage parameters. Therefore, this paper primarily investigates the seepage mechanisms in tight, high-water-cut sandstone gas reservoirs. While considering the influence of water saturation on various seepage mechanisms, it establishes a gas well productivity equation under stable seepage conditions and presents an analysis of the influencing factors. In a comparison of the unobstructed flow rates calculated using the productivity equation developed in this paper with those obtained from conventional gas well productivity equations and actual gas well productivity tests, the new equation demonstrates smaller errors. This provides a theoretical basis for evaluating productivity and making rational production allocation decisions in high-water-cut tight sandstone gas reservoirs.

Influence of water saturation on the compressive strength of concrete under high strain rates

AbstractIn this study, the influence of different water saturation achieved by different storage conditions on the static and dynamic compressive strength of three different concretes were investigated. The specimens were first dried then water‐saturated and tested both under static and impact loading. The impact tests were carried out in a split Hopkinson bar. Depending on the concrete strength class, increases in the compressive strength of 200%–300% at strain rates in the range of 90–160 1/s were observed. Compared to storage under ambient conditions, the compressive strength decreases as a result of drying due to microcrack formation. Furthermore, the concretes compressive strengths of water‐saturated specimens decrease compared to dry specimens. This decrease was observed under both static and impact loading and is independent of the strain rate. The failure of the dry specimens was more explosive with an increased number of cracks compared to water‐saturated specimens.

Internal structure changes within porous asphalt mixture with different saturation under vertical repeated load

Porous asphalt (PA) pavement is subjected to the coupling effects of vehicle load, high temperature and moisture saturation during rainy summer days. The harsh traffic and environmental conditions pose a great challenge to the longevity of PA pavement, which still lacks quantitative evidence. This study aims to characterize the internal structure change of PA mixtures under the actual coupling conditions through a modified dynamic creep test, in which the temperature of rainfall is realized through constant temperature water tank during repeated loading process. The microstructure changes of PA mixtures were characterized using image processing and analysis methods. The test results show that the influence of water saturation on permanent deformation is obvious in the compaction stage. At this stage, the creep rate of the saturated specimen is the highest, followed by the scoured specimen and dry specimen. The greater the degree of water saturation, the earlier the void area stops decreasing. The presence of moisture aggravates the occurrence of failure, and leads to an increase in the number of small voids. In addition, it is also found that the increase of water saturation will expand the influence range of load compaction, resulting in the difference in void area between upper and lower parts of PA-13 decrease. The difference in the number of small voids between upper and lower parts of PA-13 is also reduced. The greater the degree of water saturation, the more obvious the decrease of contact length at the initial stage of loading, which could be attributed to the increase of water saturation that promotes the filling failure at the initial stage of loading and leads to rheological failure and overpressure failure in advance. Moreover, the division of the change process of void area, quantity, and contact length are consistent with the permanent deformation. The findings of this study reveal important information about the damage evolution of PA pavement rutting resistance under different saturation states.

Influence of Water Saturation on Curtain Formation of Frozen Wall

In the process of in situ mining of underground oil shale, it is necessary to build an underground frozen wall around the mining area to prevent the inflow of groundwater and prevent oil and gas leakage. However, the water saturation of the frozen soil affects the formation of the freezing circle. In practical engineering, when building a frozen wall in soil under different water saturation conditions, the curtain is often not closed. It also affects the construction and operating costs of the entire project. In this paper, the methods of laboratory experiments and numerical simulation analysis are supplemented by the analysis of ordinary differential equations and partial differential equations. Aiming at the lowest cost, the temperature drop process and freezing time around the frozen well under different water saturation conditions are calculated and analyzed in detail. The formation law of the frozen wall curtain under different water saturation conditions is obtained. It provides a reference for the setting of the low-temperature loading time and the oil shale extraction range of frozen wells for different soils in practical engineering.

Influence of water saturation and soil properties on the removal of organic pollutants using microwave heating

Properties of fluids and media, such as soil moisture, may play a significant role in the absorption of microwave and heat distribution during the remediation of soil contaminated with volatile and semi-volatile compounds. Previous studies have been performed on soil samples placed inside a microwave oven cavity in a reactor far from the waveguide outlet or directly inside the metal waveguides. These conditions are far from in situ applications where the unsaturated soil is directly exposed to microwaves through the antenna slots. The objective of this study was therefore to understand better how soil temperature and pollutant recovery change during microwave and conduction heating and how soil properties, liquid type, and saturation influence that. We developed a unique experimental setup that consists of a splittable soil column inserted inside the cavity of a modified domestic microwave oven (power 1000 W and frequency 2.45 GHz) so that the soil surface is in direct contact with the radiated microwaves. Experiments with electrical resistance heating using the same column but with a modified design were conducted for comparison. We used three types of soils spanning fine, medium, and coarse sands, and two semi-volatile pollutants (xylene and diesel fuel). The pollutants and water of different volumes (12% and 25%) were mixed with soils to make the artificially contaminated soils. Temperature values were measured at different points along the sand-packed column using fiber-based optical thermocouples. We evaluated treatment efficiency in space (soil analysis) and time (outlet phase decantation).The experimental results show that microwave heating technology is optimal for water saturation of around 12%, which gives the best compromise between the overall dielectric properties and allows rapid and efficient heating. The temperature increases fast at the beginning of the microwave heating and stabilizes because of the latent heat of the water and pollutant vaporization and then increases again but slowly for dry soil conditions. A maximum temperature of 170 °C was achieved after 140 min of microwave heating. The type of soil and pollution can drastically affect remediation efficiency through mechanical mechanisms (because of a pressure increase) in addition to physical mechanisms (evaporation) for pollutant removal. The removal efficiencies, using the outlet fluids decantation, were 67%, 73%, and 75% for fine, medium, and coarse sand, respectively, for the applied heating time. We found that microwave heating works better in coarser sand where classical conduction heating usually failed. Comparing the two types of heating (microwave and conductive heating) under the same conditions highlights that the use of microwaves makes it possible to reach very high temperatures in a shorter time than with thermal conduction heating.

Influence of Water Saturation and Real-Time Testing Temperature on Mechanical Behavior of Sandstone Under Conventional Triaxial Compression

Influence of Water Saturation and Real-Time Testing Temperature on Mechanical Behavior of Sandstone Under Conventional Triaxial Compression

Influence of Water Saturation on Propagation of Weak-Intensity Shock Waves in Bulk Media

Influence of Water Saturation on Propagation of Weak-Intensity Shock Waves in Bulk Media

Influence of Water Saturation, Grain Size of Quartz Sand and Hydrate-Former on the Gas Hydrate Formation

The development of technologies for the accelerated formation or decomposition of gas hydrates is an urgent topic. This will make it possible to utilize a gas, including associated petroleum one, into a hydrate state for its further use or to produce natural gas from hydrate-saturated sediments. In this work, the effect of water content in wide range (0.7–50 mass%) and the size of quartz sand particles (porous medium; <50 μm, 125–160 μm and unsifted sand) on the formation of methane and methane-propane hydrates at close conditions (subcooling value) has been studied. High-pressure differential scanning calorimetry and X-ray computed tomography techniques were employed to analyze the hydrate formation process and pore sizes, respectively. The exponential growth of water to hydrate conversion with a decrease in the water content due to the rise of water–gas surface available for hydrate formation was revealed. Sieving the quartz sand resulted in a significant increase in water to hydrate conversion (59% for original sand compared to more than 90% for sieved sand). It was supposed that water suction due to the capillary forces influences both methane and methane-propane hydrates formation as well with latent hydrate forming up to 60% either without a detectable heat flow or during the ice melting. This emphasizes the importance of being developed for water–gas (ice–gas) interface to effectively transform water into the hydrate state. In any case, the ice melting (presence of thawing water) may allow a higher conversion degree. Varying the water content and the sand grain size allows to control the degree of water to hydrate conversion and subcooling achieved before the hydrate formation. Taking into account experimental error, the equilibrium conditions of hydrates formation do not change in all studied cases. The data obtained can be useful in developing a method for obtaining hydrates under static conditions.

Discrepancy between measured dynamic poroelastic parameters and predicted values from Wyllie\u2019s equation for water-saturated Istebna sandstone

The drilling-related geomechanics requires a better understanding of the encountered formation properties such as poroelastic parameters. This paper shows set of laboratory results of the dynamic Young’s modulus, Poisson’s ratio, and Biot’s coefficient for dry and water-saturated Istebna sandstone samples under a series of confining pressure conditions at two different temperatures. The predicted results from Wyllie’s equation were compared to the measured ones in order to show the effect of saturation on the rock weakening. A negative correlation has been identified between Poisson’s ratio, Biot’s coefficient and confining pressure, while a positive correlation between confining pressure and Young’s modulus. The predicted dynamic poroelastic rock properties using the P-wave value from Wyllie’s equation are different from measured ones. It shows the important influence of water saturation on rock strength, which is confirmed by unconfined compressive strength measurement. Linear equations have been fitted for the laboratory data and are useful for the analysis of coupled stress and pore pressure effects in geomechanical problems. Such results are useful for many drilling applications especially in evaluation of such cases as wellbore instability and many other drilling problems.

Methane Hydrate Formation and Dissociation in Sand Media: Effect of Water Saturation, Gas Flowrate and Particle Size

Assessing the influence of key parameters governing the formation of hydrates and determining the capacity of the latter to store gaseous molecules is needed to improve our understanding of the role of natural gas hydrates in the oceanic methane cycle. Such knowledge will also support the development of new industrial processes and technologies such as those related to thermal energy storage. In this study, high-pressure laboratory methane hydrate formation and dissociation experiments were carried out in a sandy matrix at a temperature around 276.65 K. Methane was continuously injected at constant flowrate to allow hydrate formation over the course of the injection step. The influence of water saturation, methane injection flowrate and particle size on hydrate formation kinetics and methane storage capacity were investigated. Six water saturations (10.8%, 21.6%, 33%, 43.9%, 55% and 66.3%), three gas flowrates (29, 58 and 78 mLn·min−1) and three classes of particle size (80–140, 315–450 and 80–450 µm) were tested, and the resulting data were tabulated. Overall, the measured induction time obtained at 53–57% water saturation has an average value of 58 ± 14 min minutes with clear discrepancies that express the stochastic nature of hydrate nucleation, and/or results from the heterogeneity in the porosity and permeability fields of the sandy core due to heterogeneous particles. Besides, the results emphasize a clear link between the gas injection flowrate and the induction time whatever the particle size and water saturation. An increase in the gas flowrate from 29 to 78 mLn·min−1 is accompanied by a decrease in the induction time up to ~100 min (i.e., ~77% decrease). However, such clear behaviour is less conspicuous when varying either the particle size or the water saturation. Likewise, the volume of hydrate-bound methane increases with increasing water saturation. This study showed that water is not totally converted into hydrates and most of the calculated conversion ratios are around 74–84%, with the lowest value of 49.5% conversion at 54% of water saturation and the highest values of 97.8% for the lowest water saturation (10.8%). Comparison with similar experiments in the literature is also carried out herein.

The determining factor of hydrate dissociation rate in the sediments with different water saturations

In nature, gas hydrate is mainly distributed in permafrost region and deep ocean sediments. For these two types of hydrate reservoirs, water contents in the sediments were different. The water content has a large influence on the characteristics of heat transfer and fluid flow in the sediments, thereby affecting the hydrate dissociation behavior. In this paper, the experiments of hydrate dissociation by depressurization in sediments with different water saturations were conducted. The influences of water saturation on the pressure, the temperature, the gas production, the water production, and the hydrate dissociation rate were analyzed. The experimental results showed that, in the depressurization stage (DS), the rate of pressure dropping and the amount of hydrate reformation increased with the raise of the water saturation in the sediments. In the constant pressure stage (CPS), although the heat conduction rate of the sediments increased with the increase of the water saturation, the mass transport rate of the gas released from hydrate dissociation was limited due to the increase of water saturation. As a result, the hydrate dissociation rate decreased with the increase of the water saturation in the sediments. According to these experimental results, during the hydrate dissociation in the sediments with different water saturations, the hydrate dissociation rate is determined by the mass transport rate of the gas released from the hydrate dissociation. For the hydrate reservoirs with the high-water saturation, the hydrate dissociation rate is largely limited by the diffusion rate of gas released from hydrate dissociation. Hence, the key factor to improve the hydrate dissociation rate in the sediments with high water saturation is to increase the diffusion rate of gas in the sediments.

Effect of pore water pressure on soil crack against safety factor of slope stability

The method used in this study is to simulate slopes that occur crack and get the influence of water saturation. The simulation is made with a computer application program, which is a program for calculating slope stability. The results of the analysis in this study found that the occurrence of cracks on the slope surface, the slope safety number will decrease when the crack is entered by water. Water entering the soil crack will cause pore water pressure which will then provide additional impetus to the slope landslide field. The greater the pore water pressure, the greater the decrease in security numbers. Besides that, the crack position from the edge of the slope has an effect on decreasing slope safety factor. A far the position of the crack from the edge of the slope increases the safety factor. The biggest decrease occurred in the position of 3 m crack from the edge of the slope. Crack positions greater than 3 m are the same. This happens because the slope failure field occurs at about 3 m from the edge of the slope.

The influence of water saturation and confining pressure to gas porosity and permeability of sandstone

Understanding of gas porosity and permeability is important in gas storage, recovery and nuclear waste disposal. In this paper, we focus on the gas porosity and permeability variation of sandstone at different water saturation in loading–unloading cycle. Through an improved method, we prepared the samples with water saturation level from 0 to 81%. The test results suggest that gas effective permeability and porosity are sensitive to confining pressure. This is particularly true in low pressure from 1 to 10 MPa. There is a significant difference between loading and unloading process. This is caused by irreversible deformation of pores and microcracks. The existence of water inside samples leads to a change of permeability on the order of magnitudes from 10−13 to 10−15 m2. Water saturation also influences the sandstone porosity significantly. We observed that the gas relative porosity almost decreases linearly with the increase of water saturation. A simple power law is modified to describe the relationship between gas effective permeability and porosity.

Influence of water saturation and particle size on methane hydrate formation and dissociation in a fixed bed of silica sand

In this work, the effects of water saturation and particle size on methane hydrate formation and dissociation in a fixed bed of silica sand were investigated. The experiments were carried out at 277.15 K with the initial pressure fixed at 8 MPa. Three water saturations (50%, 70%, and 90%) and two particle sizes (0.18-0.25 mm and 0.3-0.9 mm) of silica sand were used. The results indicated that water conversion to methane hydrates increased with the decrease of water saturation. 70% was found to be an optimum water saturation due to the largest hydrate amount and the highest gas uptake obtained using the small particle size of silica sand (0.18-0.25 mm). In addition, hydrate formation rate and gas uptake obtained using small particle size of silica sand were larger, and gas recovery and hydrate dissociation rate were higher in the dissociation experiments using the small particle size of silica sand. Therefore, the medium water saturation (70%) and small particle size (0.18-0.25 mm) are favorable for methane hydrate formation and dissociation in the fixed bed of silica sand.

Influence of water saturation on strength of modified gypsum-alumina expanding cement at stage of delayed hardening

The article analyzes the influence of material composition of modified gypsum-alumina expanding cement with regard to mineral components ratio on its mechanical-and-physical properties change due to water saturation at the stage of delayed hardening. The expandable cementing medium applied in the survey, except for traditional components such as crushed gypsum rock and alumina cement, contained additionally portland cement and superplasticizer, based on polycarboxylic ethers. It has been established that depending on mineral components ratio water saturation of one-year-old cement rock can either improve or worsen its strength properties, provided that bending and compression resistance can change asynchronously and divergently. A regularity has been revealed regarding composite water resistance change depending on mass ratio of portland cement and gypsum rock (AC/GR). Within the variability of experimental factors a judicious ratio - AC/GR=0,2-0,95 has been established, where bending and compression resistance does not decrease as a result of cement rock water saturation during 48 hours.

Sensitivity of kersantite toughness to moisture: influence of the phyllosilicates

Evolution of the fracture behavior of a magmatic rock, the Loperhet kersantite, is under study to have a better understanding of the scaling effect occurring at the surface of monumental stone. A fracture mechanics approach is proposed to measure the ability to withstand a crack initiation and to observe the fracture surfaces after propagation. The influence of water saturation and moisture is considered and dependency of toughness with water vapor pressure is determined during humidification and drying. Results indicate that kersantite toughness decreases when moisture content increases. This is related to clay phases and phyllosilicates, involved in the swelling and identified as the weakness phases of the stone. Indeed, it appears that evolution of toughness and crack paths are related to the mineralogical weathering of these water-sensitive phases. Mineralogical microdamage due to moisture variations is involved in the evolution of the macroscopic mechanical behavior of kersantite.

The Influence of Water Saturation on the Short- and Long-Term Mechanical Behavior of Red Sandstone

The presence of water greatly influences time-dependent rock deformation. An understanding of how water can affect the time-dependent mechanical behavior of rock is important when assessing the long-term stability of geotechnical projects. While the previous studies have performed brittle creep experiments on oven-dry or fully-saturated rocks, we report here on a study designed to better understand brittle creep at different levels of saturation. We performed brittle creep experiments on oven-dry samples of red sandstone (Hunan province, China) and samples of the sandstone pre-immersed in water for different durations (from 2 to 8 days). These samples were deformed at a constant stress in one of either two conditions: dry or submerged in water. Before performing creep experiments, we first performed a series of water absorption and constant stress rate experiments to guide the stresses required for our creep tests and to assist with their interpretation. Our creep experiments show that immersion in water greatly increased the minimum creep strain rate and greatly shortened the time-to-failure when compared to the dry state. In detail, the minimum creep strain rate and time-to-failure increased and decreased, respectively, as pre-immersion duration increased from 4 to 6 days, but did not change as the duration was further increased to 8 days. We attribute this to the saturation of microcracks between 4 and 6 days (i.e., water imbibition was complete, or close to completion, following 6 days). We also show that oven-dry samples deformed at a constant stress underwater fail at stresses much lower than oven-dry samples deformed under dry conditions, due to the imbibition of water during deformation. Samples pre-immersed in water, but deformed in the dry condition were characterized by lower strain rates and longer time-to-failure than those pre-immersed in water and deformed underwater. Our explanation for this is that, due to the availability of water, crack tips can remain hydrated when the sample is deformed underwater, thus increasing the efficacy of stress corrosion cracking. The relationships and data provided herein inform on the long-term stability of engineering structures.