Academic literature on the topic 'Soil-water distribution coefficient (Kd)'

The paper provides data from the comprehensive studies of the levels and distribution pattern of radionuclide contamination in the ‘bottom sediments/soil-to-water-to-plants’ of water bodies at the Telkem site of the Semipalatinsk Test Site (STS). Research objects were water-filled craters Telkem-1 and Telekm-2 that resulted from excavation explosions. As part of these studies, sediments, soil, water, plants were duplicately sampled, in which the content of manmade 90Sr, 239+240Pu and g-emitting radionuclides were determined. As a result, a high level of radioactive contamination is currently found to persist in the ecosystem of water bodies at the Telkem site both for sediments ( 137Cs, 241Am, 90Sr and 239+240Pu) and water ( 90Sr). Based upon findings, the distribution coefficient (Kd) for the ‘sediments-to-water’ system and the concentration ratio (CRs-b) were calculated for the ‘sediments/soil-to-plants’ system. The distribution coefficient Kd for 90Sr averages 10, for 239+240Pu – 3.7·105 . Plants’ capacity to accumulate from sediments and soil of aquatic ecosystems at the Telkem site, with respect to man-made radionuclides, decreases in the series CRs-b 90Sr > CRs-b 60Co > CRs-b 137Cs > CRs-b 152Eu > CRs-b 241Am > CRs-b 239+240Pu.

ABSTRACT There are scientific studies describing changes in properties of the water when subjected to the action of a magnetic field, which may favor the availability of some nutrients in the soil solution. Some nutrients, although they are essential to the process of crop development, can be sources of pollution for watercourses and soil. The aim of this study was to evaluate the effect of water magnetization on transport parameters of the phosphate ion in a Red Latosol (RL) and in a Quartzarenic Neosol (QN). Saturated leaching columns were connected to bottles containing KH2PO4 solutions. In RL, there were significant differences in phosphorus (P) transport parameters, related to the retardation factor (R) and distribution coefficient (Kd). For the others, Peclet number (Pe), dispersive-diffusion coefficient (D) and dispersivity (λ), there were no significant differences in the comparison between the treatments with magnetized and non-magnetized water. In QN, there were statistical differences in R and Kd. For the other parameters, Pe, D and λ, there were no statistical differences between treatments.

In the context of contaminated site remediation, the fate of chlorinated solvents in the subsurface and subsequent groundwater contamination is influenced by soil properties governing sorption. The solid–water distribution coefficient (Kd) is a key parameter for modeling contaminant distribution and transport, essential for risk assessment and remediation planning. This study evaluated tetrachloroethene sorption isotherms in 34 low-organic-carbon soils from the Czech Republic, assessing the influence of soil properties on Kd. Soil samples exhibited variability in organic carbon content (˂0.05–0.81%), with clay ranging from 0% to 64.9%, silt 5.1% to 71.2%, and sand 5.2% to 88.9%, specific surface area (0.41–64.39 m2 g−1), particle density (2.05–4.09 g cm−3), and porosity (43.5–67.3%). Batch experiments were conducted using standard procedures, with Kd values ranging from 0.379 to 2.272 L kg−1. Statistical analysis grouped the soils into three textural classes: sandy, clayey fine, and silty loam. The findings reveal that organic carbon content and specific surface area are the primary predictors of Kd, while clay and sand also play a significant role in shaping sorption behavior. Multivariate regression models explained 63.6% to 98.5% of Kd variability with high accuracy, as indicated by low root means square error (0.070–0.329) and mean absolute percentage error (3.8–28.8%) values. These models offer reliable predictions of sorption behavior, providing valuable tools for risk assessment and remediation strategies.

Static adsorption experiments were conducted to understand the impact of soil surface charge characteristics, such as pH, AEC and CECp values, on migration behavior of radioactive Uranium, Strontium and Cesium. The results demonstrate that distribution coefficient of Uranium (U-Kd value) increases with decreasing initial pH of solution, and increases with increasing AEC values for acidic clay and silty clay that were studied; distribution coefficients of Strontium and Cesium appear to be positively correlated with CECp values of and total contents of montomorillonite and illite in the soil.

The dimerization of a solute dissolved in binary immiscible solvents shows that the value of the partition coefficient, kD of the solutes are influenced by the dimerization constant, K of the solute in one of the solvents according to the description: (C_X^A)/(C_X^B ) = kD + 2kD2KCxB where CxA and CxB are the concentrations of the solute x in the solvents A and B respectively. Both kD and K are parameters that predict the extent of beneficiation for most minerals. Also, kD is a fundamental parameter that determines the extent of solute recovery during solvent extraction. In this study, it is found that the order K kD and K kD are the effects for acetic and succinic acids respectively in the binary solvents composed of carbon tetrachloride/water and diethylether/water systems respectively. These results suggest that the distributions of these solutes in the solvents are accompanied by the formation of succinic anhydride which is more favoured than the dimerization of the acetic acid. Also, the changes in the values of distribution enthalpies, HD are corroborated to explain these experimental observations.

The Lake of Texcoco is a closed basin with soils that confer salinity, conductivity, and alkalinity to it. It has undergone a reduction in size, incorporation of wastewater, and short-term desiccation, and includes temporary wetlands interconnected during the rainy season, some of which receive treated wastewater. Sediments contain metals, thus affecting water quality. Five artificial lakes were studied, and 12 metals (As, Ba, Cd, Cu, Cr, Fe, Mg, Mn, Hg, Ni, Pb, and Zn) were monitored bimonthly in water and sediments from June 2015 to March 2018. The Metal Pollution Index (MPI) and the Distribution Coefficient (Kd) were computed. Fe and Cd were the most and least stable metals in sediments, respectively (mean Log(Kd) = 4.24 and 2.079). Based on Log(Kd), metals were ranked as Fe > Mn > Zn > Cu > Mg > Cr > Ni > Ba > Pb > Hg > As > Cd. Log(Kd) values < 3 and > 5 indicate that metals occur mainly in water and sediments, respectively. The Mean Distribution Coefficient Log(Kd MPI) is a novel index proposed to assess ecological risk from metals in a water body. This index allows determining the phase (liquid or solid) where metals predominate, negatively affecting either free-swimming or benthic organisms. Log(Kd MPI) values indicated that metals occur primarily in the liquid phase in all lakes studied.

Increasing prevalence of cyanotoxins in surface water bodies worldwide threatens groundwater quality when contaminated water recharges an aquifer through natural or artificial means. The subsurface fate of anatoxin-a (ATX) is not well studied. Laboratory batch experiments were performed to expand the current knowledge of ATX sorption affinities to geologic media, with a focus on natural soil (Vertisol, Ultisol, Alfisol, and Inceptisol) and physical, chemical, and mineralogical characteristics. For a range of aqueous ATX concentrations (0.3–14 μg/L), linear, Freundlich, and Langmuir isotherms fit observed data well (r2 = 0.92–1.00, RMSE = 0.4–6.3 μg/kg). Distribution coefficient (Kd) and retardation factor (Rf) values were computed for the linear isotherm, giving Kd of 22.3–77.1 L/kg and Rf of 62–256. Average percent removals were 85.0–92.2%. The strongest predictors of Kd were kaolinite and smectite group mineral abundances and for Rf were smectite group and silt and clay abundances. Results indicate that loamy, silty, or clayey soils—particularly Vertisols—tend to substantially slow migration of ATX through natural soil systems. Where implemented as a functionalized amendment in an engineered pollution control media, such soils may enhance natural ATX attenuation processes, thereby supporting the protection of in situ and extracted groundwater during irrigation, natural and managed aquifer recharge, or riverbank filtration.

The dimerization of a solute dissolved in binary immiscible solvents shows that the value of the partition coefficient, kD of the solutes are influenced by the dimerization constant, K of the solute in one of the solvents according to the description: (C_X^A)/(C_X^B ) = kD + 2kD2KCxB where CxA and CxB are the concentrations of the solute x in the solvents A and B respectively. Both kD and K are parameters that predict the extent of beneficiation for most minerals. Also, kD is a fundamental parameter that determines the extent of solute recovery during solvent extraction. In this study, it is found that the order K kD and K kD are the effects for acetic and succinic acids respectively in the binary solvents composed of carbon tetrachloride/water and diethylether/water systems respectively. These results suggest that the distributions of these solutes in the solvents are accompanied by the formation of succinic anhydride which is more favoured than the dimerization of the acetic acid. Also, the changes in the values of distribution enthalpies, HD are corroborated to explain these experimental observations.

Engineered nanoparticles (ENPs) have been reported for their potential to enhance in situ soil remediation due to their size and stability in water. These properties allow them to pass through soils with minimal loss in soil flushing or pump-and-treat process. The success of nanoparticle-facilitated soil flushing depends on the mobility of nanoparticles in the soil matrix. However, organic carbon content and soil texture can affect the mobility of nanoparticles in soils. This study compared the mobility of polyethylene glycol-modified urethane acrylate (PMUA) nanoparticles in three types of soils with varying organic contents. The results of two consecutive injection experiments showed that the recovery of injected nanoparticles through a soil column were 91 and 97% for sandy soil with carbon content of 0.01%, 81 and 85% for clay loam soil with organic carbon content of 1.20% and 67 and 73% for clay soil with organic carbon content of 3.25%. Furthermore, the batch experiments showed that the distribution coefficient (Kd) of PMUA nanoparticles between water and sandy soil, clay loam soil, and clay soil were 1.86, 2.34 and 3.01 mL/g, respectively. This conforms to the column experiment results and confirms that the increase in organic carbon content in soils increases the adsorption of PMUA nanoparticles, and therefore decreases the mobility of the nanoparticles through soils. Moreover, the distribution coefficient from batch experiments could be used to predict the mobility of PMUA nanoparticles in soils, and the viability of in situ PMUA-facilitated soil flushing method for specific contaminated soils.

The aim of the paper was to determine the influence of root systems of chosen tree species found in the Polish Flysch Carpathians on the increase of soil shear strength (root cohesion) in terms of slope stability. The paper's goal was achieved through comprehensive tests on root systems of eight relatively common in the Polish Flysch Carpathians tree species. The tests that were carried out included field work, laboratory work and analytical calculations. As part of the field work, the root area ratio (A IA) of the roots was determined using the method of profiling the walls of the trench at a distance of about 1.0 m from the tree trunk. The width of the. trenches was about 1.0 m, and their depth depended on the ground conditions and ranged from 0.6 to 1.0 m below the ground level. After preparing the walls of the trench, the profile was divided into vertical layers with a height of 0.1 m, within which root diameters were measured. Roots with diameters from 1 to 10 mm were taken into consideration in root area ratio calculations in accordance with the generally accepted methodology for this type of tests. These measurements were made in Biegnik (silver fir), Ropica Polska (silver birch, black locust) and Szymbark (silver birch, European beech, European hornbeam, silver fir, sycamore maple, Scots pine, European spruce) located near Gorlice (The Low Beskids) in areas with unplanned forest management. In case of each tested tree species the samples of roots were taken, transported to the laboratory and then saturated with water for at least one day. Before testing the samples were obtained from the water and stretched in a. tensile testing machine in order to determine their tensile strength and flexibility. In general, over 2200 root samples were tested. The results of tests on root area ratio of root systems and their tensile strength were used to determine the value of increase in shear strength of the soils, called root cohesion. To this purpose a classic Wu-Waldron calculation model was used as well as two types of bundle models, the so called static model (Fiber Bundle Model — FIRM, FBM2, FBM3) and the deformation model (Root Bundle Model— RBM1, RBM2, mRBM1) that differ in terms of the assumptions concerning the way the tensile force is distributed to the roots as well as the range of parameters taken into account during calculations. The stability analysis of 8 landslides in forest areas of Cicikowicleie and Wignickie Foothills was a form of verification of relevance of the obtained calculation results. The results of tests on root area ratio in the profile showed that, as expected, the number of roots in the soil profile and their ApIA values are very variable. It was shown that the values of the root area ratio of the tested tree species with a diameter 1-10 ram are a maximum of 0.8% close to the surface of the ground and they decrease along with the depth reaching the values at least one order of magnitude lower than close to the surface at the depth 0.5-1.0 m below the ground level. Average values of the root area ratio within the soil profile were from 0.05 to 0.13% adequately for Scots pine and European beech. The measured values of the root area ratio are relatively low in relation to the values of this parameter given in literature, which is probably connected with great cohesiveness of the soils and the fact that there were a lot of rock fragments in the soil, where the tests were carried out. Calculation results of the Gale-Grigal function indicate that a distribution of roots in the soil profile is similar for the tested species, apart from the silver fir from Bie§nik and European hornbeam. Considering the number of roots, their distribution in the soil profile and the root area ratio it appears that — considering slope stability — the root systems of European beech and black locust are the most optimal, which coincides with tests results given in literature. The results of tensile strength tests showed that the roots of the tested tree species have different tensile strength. The roots of European beech and European hornbeam had high tensile strength, whereas the roots of conifers and silver birch in deciduous trees — low. The analysis of test results also showed that the roots of the studied tree species are characterized by high variability of mechanical properties. The values Of shear strength increase are mainly related to the number and size (diameter) of the roots in the soil profile as well as their tensile strength and pullout resistance, although they can also result from the used calculation method (calculation model). The tests showed that the distribution of roots in the soil and their tensile strength are characterized by large variability, which allows the conclusion that using typical geotechnical calculations, which take into consideration the role of root systems is exposed to a high risk of overestimating their influence on the soil reinforcement. hence, while determining or assuming the increase in shear strength of soil reinforced with roots (root cohesion) for design calculations, a conservative (careful) approach that includes the most unfavourable values of this parameter should be used. Tests showed that the values of shear strength increase of the soil reinforced with roots calculated using Wu-Waldron model in extreme cases are three times higher than the values calculated using bundle models. In general, the most conservative calculation results of the shear strength increase were obtained using deformation bundle models: RBM2 (RBMw) or mRBM1. RBM2 model considers the variability of strength characteristics of soils described by Weibull survival function and in most cases gives the lowest values of the shear strength increase, which usually constitute 50% of the values of shear strength increase determined using classic Wu-Waldron model. Whereas the second model (mRBM1.) considers averaged values of roots strength parameters as well as the possibility that two main mechanism of destruction of a root bundle - rupture and pulling out - can occur at the same. time. The values of shear strength increase calculated using this model were the lowest in case of beech and hornbeam roots, which had high tensile strength. It indicates that in the surface part of the profile (down to 0.2 m below the ground level), primarily in case of deciduous trees, the main mechanism of failure of the root bundle will be pulling out. However, this model requires the knowledge of a much greater number of geometrical parameters of roots and geotechnical parameters of soil, and additionally it is very sensitive to input data. Therefore, it seems practical to use the RBM2 model to assess the influence of roots on the soil shear strength increase, and in order to obtain safe results of calculations in the surface part of the profile, the Weibull shape coefficient equal to 1.0 can be assumed. On the other hand, the Wu-Waldron model can be used for the initial assessment of the shear strength increase of soil reinforced with roots in the situation, where the deformation properties of the root system and its interaction with the soil are not considered, although the values of the shear strength increase calculated using this model should be corrected and reduced by half. Test results indicate that in terms of slope stability the root systems of beech and hornbeam have the most favourable properties - their maximum effect of soil reinforcement in the profile to the depth of 0.5 m does not usually exceed 30 kPa, and to the depth of 1 m - 20 kPa. The root systems of conifers have the least impact on the slope reinforcement, usually increasing the soil shear strength by less than 5 kPa. These values coincide to a large extent with the range of shear strength increase obtained from the direct shear test as well as results of stability analysis given in literature and carried out as part of this work. The analysis of the literature indicates that the methods of measuring tree's root systems as well as their interpretation are very different, which often limits the possibilities of comparing test results. This indicates the need to systematize this type of tests and for this purpose a root distribution model (RDM) can be used, which can be integrated with any deformation bundle model (RBM). A combination of these two calculation models allows the range of soil reinforcement around trees to be determined and this information might be used in practice, while planning bioengineering procedures in areas exposed to surface mass movements. The functionality of this solution can be increased by considering the dynamics of plant develop¬ment in the calculations. This, however, requires conducting this type of research in order to obtain more data.

AbstractRadioactive cesium-bearing microparticles (CsMPs) are glassy particles containing large amounts of radioactive cesium (Cs, i.e., 134Cs and 137Cs). Because Cs in CsMPs is covered with insoluble glass, CsMPs may not release Cs into the liquid phase of river water. Previous studies have shown that CsMPs may drive overestimation of Cs transfer between the solid and liquid phases in rivers. In this study, we investigated the contribution of CsMPs to Cs concentrations in forest soil and river water in the Takase River watershed to explore the migration of CsMPs from a forest catchment and their effect on the distribution coefficient in the river water. The Cs concentration derived from CsMPs as a proportion of that in the bulk soil and particulate Cs in the river water was not large; therefore, CsMPs did not have a significant effect on the distribution coefficient. In forest soil, variation in the distribution of CsMPs in soil was greater than that in the distribution of Cs adsorbed onto soil particle. This variation might cause the Cs concentration derived from CsMPs flowing into rivers to vary more than the particulate Cs concentration. To elucidate CsMPs migration and its effects on the Cs concentration in the river, further research such as soil sampling to assess the spatial distribution of CsMPs in the watershed is needed.

Moisture has a great influence on not only the strength and deformation characteristics of soil, but also on the friction coefficient of interface between filler and reinforcement, thereby on the performance of the reinforced subgrade structure. In this paper, seep/W software is used to analyze the internal water distribution law of reinforced soil retaining wall under different groundwater levels, and then sigma/W software is used to analyze the deformation characteristics of reinforced subgrade structure under water field distribution. The results show that with the decline of groundwater level, the volume moisture content of each part in the vertical direction of reinforced subgrade structure changes greatly, and the moisture content at the bottom of the wall redistributes, and the closer it is to the bottom of the wall, the denser the moisture content distribution is; When the buried depth of groundwater is greater than 8m, the groundwater level has little influence on the performance of reinforced subgrade structure, and the influence of groundwater can increase the lateral deformation of reinforced retaining wall by more than 20%. Groundwater condition and rainstorm condition should be considered in the design of reinforced subgrade structure in order to reflect the influence of water on the performance of reinforced structure and to ensure the safety of reinforced structure.

An important consideration in constructing certain types of geochemical models, especially those applied to environmental problems, is to account for the sorption of ions from solution onto mineral surfaces. Metal oxides and aluminosilicate minerals, as well as other phases, can sorb electrolytes strongly because of their high reactivities and large surface areas (e.g., Davis and Kent, 1990). When a fluid comes in contact with minerals such as iron or aluminum oxides and zeolites, sorption may significantly diminish the mobility of dissolved components in solution, especially those present in minor amounts. Sorption, for example, may retard the spread of radionuclides near a radioactive waste repository or the migration of contaminants away from a polluting landfill. In acid mine drainages, ferric oxide sorbs heavy metals from surface water, helping limit their downstream movement (see Chapter 23). A geochemical model useful in investigating such cases must provide an accurate assessment of the effects of surface reactions. Many of the sorption theories now in use are too simplistic to be incorporated into a geochemical model intended for general use. To be useful in modeling electrolyte sorption, a theory must account for the electrical charge on the mineral surface and provide for mass balance on the sorbing sites. In addition, an internally consistent and sufficiently broad database of sorption reactions must accompany the theory. The Freundlich and Langmuir theories, which use distribution coefficients Kd to set the ratios of sorbed to dissolved ions, are applied widely in groundwater studies (Domenico and Schwartz, 1990) and used with considerable success to describe sorption of uncharged organic molecules (Adamson, 1976). The models, however, do not account for the electrical state of the surface, which varies sharply with pH, ionic strength, and solution composition. Freundlich theory prescribes no concept of mass balance, so that a surface might be predicted to sorb from solution without limit. Both theories require that distribution coefficients be determined experimentally for individual fluid and rock compositions, and hence both theories lack generality. Ion exchange theory (Stumm and Morgan, 1981; Sposito, 1989) suffers from similar limitations. Surface complexation models, on the other hand, account explicitly for the electrical state of the sorbing surface (e.g., Adamson, 1976; Stumm, 1992).

In normally clays and silts, excess pore pressures due to piezocone penetration show a monotonically decreasing response with time, but dissipation tests performed in heavily overconsolidated soils show dilatory behavior. Therefore, available solutions proposed for normally consolidated soils do not adequately evaluate the response of pore water pressure in overconsolidated soils. In order to predict the coefficient of consolidation in non-standard dissipation curve, the distribution characteristics of individual excess pore pressure components (Δuoct&Δushear) are studied. The influence zones of the octahedral and shear components due to penetration are estimated by theoretical framework and experimental method. In this study, the predicted distribution results at OCR=10 and OCR=20 are compared by the piezocone penetration results in Korea University Calibration Chamber.

Piping has been attributed as a major cause of dam and embankment failures. Current national prediction models to predict piping use the hydraulic gradient between the upstream and downstream water levels as an indicator. They are deterministic and take no account of preferential pathways. However, piping usually initiates from a discrete downstream location and recent research indicates that piping happens when the water velocity reaches a critical value. The local velocity close to the downstream ground surface is strongly related to the inherent heterogeneity of the soil. This paper takes account of the spatial variability of hydraulic conductivity. Based on stochastic seepage analysis, local velocities in and under an embankment are computed. The results show that, when the coefficient of variation of hydraulic conductivity is small, the locations of the maximum local velocity from 500 realizations aggregate into a small area which is near the downstream toe of the embankment. In contrast, increasing the coefficient of variation scatters the possible locations of the maximum local velocity. Two typical situations are identified: one situation where the maximum local velocity is close to the downstream ground surface, and the other where the maximum local velocity is far from the downstream ground surface and located near the center of the foundation. In the first situation it is easier to reach the critical value to initiate piping because the maximum local velocity is near the ground surface, but it is also relatively easy to protect against. In contrast, in the second situation it is easier to form a passage for piping development once piping is initiated. This is due to the velocity towards the center of the foundation increasing.

The laws of unsaturated and capillary movement of water in soils are analyzed, which are complex and insufficiently studied, but significantly affect the condition of the ground. Experience in the design and construction of the subsoil has shown that during the excavation works can significantly change the conditions of soils and their water-thermal regime. Therefore, the characteristics of soils used in stability calculations should be determined taking into account the subsequent condition of the soil in the conditions of occurrence, as well as the possible change of these conditions during construction and maintenance. One of the urgent tasks is to improve the methods of regulating the water-thermal regime of roads. By changing the conditions of its course or the type of water-thermal regime itself, significant successes can be achieved in improving the maintenance of roads, engineering and transport facilities. Dangerous effect of these factors on the embankment of the ground is manifested in the formation of wetting, wetting of the soil and layers of pavement, resulting in reduced density, strength of soils, subsidence, swelling and loss of continuity due to cracking. As a result, the strength of the road structure, the flatness of the carriageway, the durability of the pavement and the adhesion of the wheels to the roadway are reduced. The most dangerous for roads are moisture accumulation, freezing, thawing of the ground, intensive heating and intensive cooling of the layers of pavement. The analysis of regularities of formation of a water-thermal regime of a ground and its regulation at the expense of the device of optimum capillary-interrupting layers is carried out. The laws of soil moisture when raising capillary water showed that when the layer of the embankment with a high coefficient of impregnation is dehydrated over the layer with a lower coefficient, the speed of moving capillary water into the upper soil layers drops sharply. This fall occurs as a result of changes in the relationship between the driving forces of the menisci and the forces of resistance of capillary water in the soil. The process of unsaturated movement of water in the soil is determined by the combination of many factors that characterize the capillary system of the soil. The calculation uses complex indicators of soil water movement conditions, which are established experimentally for each variety and soil density at optimal humidity, as well as water filtration coefficients in the soil. To establish the relationship between these experimental data and the required values that determine the capillary system of the soil, the filtration of water in the soil was considered. Determining the optimal capillary system of the soil and establishing the unstable distribution of own capillary water in the structures of high embankments will ensure the strength of approaches to road bridges. The method of calculating the determination of the optimal composition of the road layers taking into account the processes of water-thermal regime and capillary movement of water has been improved. The algorithm of calculation in the program Microsoft Excel for selection of optimum structure of a ground cloth of a high embankment on approaches to automobile bridges is offered.

Piping has been attributed as a major cause of dam and embankment failures. Current national prediction models to predict piping use the hydraulic difference between the upstream and downstream water levels as an indicator. They are deterministic and take no account of preferential pathways. However, piping usually initiates from a discrete downstream location and recent research indicates that piping happens when the velocity reaches a critical value. The local velocity close to the downstream ground surface is strongly related to the inherent heterogeneity of the soil. This paper takes account of the spatial variability of hydraulic conductivity. Based on stochastic seepage analysis, local velocity in and under an embankment are computed. The results show that, when the coefficient of variation of hydraulic conductivity is small, the locations of the maximum local velocity from 500 realizations aggregate into a small area which is near the downstream toe of the embankment. In contrast, increasing the coefficient of variation scatters the possible locations of the maximum local velocity. Two typical situations are identified: one situation where the maximum local velocity is close to the downstream ground surface, and the other where the maximum local velocity is far from the downstream ground surface and located near the center of the foundation. In the first situation it is easier to reach the critical value to initiate piping because the maximum local velocity is near the ground surface but relatively easy to protect against. In contrast, in the second situation it is easier to form a passage for piping development once piping is initiated. This is due to the velocity towards the center of the foundation increasing. Once piping is initiated near the toe in the second situation, the higher velocity near the center of the foundation may promote piping progression.

Single lane tunnel is a common engineering type in water conservancy and highway, and shallow buried biased pressure tunnel is the most obvious problem in tunnel tunneling stage, which is a major problem in tunnel excavation construction. Due to shallow soil cover and partial pressure, slope instability is easy to occur, which is unfavorable to tunnel structure and surrounding rock. The lateral pressure coefficient of the surrounding rock outside the tunnel is affected by the calculated friction Angle of the surrounding rock, the friction Angle on both sides of the middle rock pillar and the bias slope Angle, and the lateral pressure coefficient of the inner surrounding rock of the double tunnel is also affected by the buried depth and the net distance of the tunnel. The vertical pressure distribution of tunnel vault is affected by tunnel depth, bias Angle and lateral pressure coefficient, but it is most affected by tunnel depth. The horizontal pressure of the surrounding rock of the tunnel is affected by the lateral pressure coefficient of the tunnel and the buried depth of the tunnel, but the buried depth of the tunnel plays a major role. The greater the buried depth, the greater the horizontal pressure of the tunnel. How to ensure tunnel quality and avoid safety accidents has become an important research topic. With the development of engineering technology, more and more computer-aided tools are applied to the solution analysis of complex engineering. Based on CAE simulation analysis method, this paper carries out slope stability checking calculation, structure and surrounding rock pressure analysis of BIM model of shallow buried biased single-lane tunnel, and summarizes a structural design method suitable for this type of tunnel.

Mineral weathering begins with mineral dissolution, typically as induced by protons or by ligands that form strong complexes with metals (Section 1.4). Proton-induced dissolution begins with H+ adsorption, exemplified in Eq. 3.2 for a metal oxyhydroxide mineral. In the absence of ligands that could replace the positively charged water molecule resulting from this rapid reaction, proton adsorption is followed by slow detachment of the metal, which then equilibrates as a soluble species in the soil solution, as illustrated in Fig. 5.1 (pathway 1) for gibbsite [Al(OH)3; see Fig. 2.7] at a pH value low enough that the detached Al3+ does not hydrolyze. Ligand-induced dissolution is also illustrated in Fig. 5.1 (pathway 2). The ligand is a fluoride anion, which forms a strong complex with Al3+ (see problem 3 in Chapter 4). Adsorption in this case occurs by ligand exchange, which is illustrated for carboxylate in Eq. 3.3. A similar reaction occurs for F-:...Slow detachment of the AlF2+ complex then follows. Whenever a mineral dissolution reaction induced by either of these two-step mechanisms is far from equilibrium, it is not influenced by the very low concentration of the constituent released from the dissolving mineral and its rate can be described by zero-order kinetics (Table 4.2). Accordingly, if [A] is the concentration of a constituent released, then the rate law can be expressed as...where kd is a rate coefficient independent of [A] , but a function of temperature, pressure, pH, the chemical properties of the mineral, and, if appropriate, the concentration of the ligand inducing dissolution via the second mechanism in Fig. 5.1. The mineral dissolution rate on the left side of Eq. 5.2 can be mass-normalized to express it in moles per mole of mineral per second by dividing the molar concentration [A] with the solids concentration of the mineral expressed in units of moles per liter. This mass-normalized rate does not depend on the amount of mineral dissolving. For proton-induced dissolution, the rate is then a function of temperature, pressure, pH, and the chemical nature of the mineral.

A computer code named Fitting for Diffusion Parameters (FDP) based on Mathematica 6.0 has been developed for modeling through- and out-diffusion experiments. FDP was used to determine the diffusion coefficients (De) and the rock capacity factors (α) for tritiated water (HTO) and 22Na+ and the distribution coefficient (Kd) of 22Na+ in Opalinus Clay (OPA). The values for De and α were obtained by fitting the results of experimental data of both transient and steady-state phases to the analytical solution of accumulated activity. The quality of the parameters De and α was tested by using them as input parameters in the equation of flux. Moreover, the diffusion parameters of HTO and 22Na+ were determined also by out-diffusion experiments. Under ambient condition at pH 7.6, the De value of (1.5 ± 0.1) × 10−11 m2/s for HTO is lower than that of (1.9 ± 1.1) × 10−11 m2/s for 22Na+, which could be explained by the electrostatic attraction between the negative surface charge of OPA and the sodium cations. For the non-sorbing species HTO, α was 0.15 ± 0.01. For the weakly sorbing species 22Na+, α was 0.50 ± 0.02 and Kd equaled (1.5 ± 0.3) × 10−4 m3/kg. The obtained diffusion parameters for HTO and 22Na+ in OPA are in good agreement with previous results by Van Loon et al. [1, 2]. FDP developed in this study has been used successfully to determine the parameters De and α for the diffusion of 237Np(V) in OPA [3].

Large amounts of highly contaminated water over 800,000 m3 accumulated in the reactor, turbine building and the trench in the facility were generated from the nuclear accident of Fukushima NPS (BWR) caused by the Great East Japan Earthquake. At present, the cold shutdown is completed stably by the circulating injection cooling system (SARRY, KURION) for the decontamination of radioactive nuclides such as 134Cs and 137Cs using zeolites and crystalline silicotitanate (CST). Further, the Advanced Liquid Processing System (ALPS) is under operation for the decontamination of 62 nuclides such as 90Sr, 129I and 60Co, etc. However, the adsorption behaviors of actinoids through the decontamination systems are complicated, and especially their adsorption properties for zeolites and CST, major inorganic adsorbents, are not yet clarified. In near future, the decontamination of actinoids leached from the crushed fuel debris will be an important subject. In this study, the practical adsorption properties of U(VI) for various inorganic adsorbents were evaluated under different solution conditions. The adsorption properties (distribution behaviors and adsorption kinetics) were evaluated by batch adsorption method; 19 kinds of inorganic adsorbents including zeolites and CST (crystalline silicotitanate) were contacted with U(VI)) solutions. The conditions of 5 kinds of U(VI) solutions were as follows; Solution 1: [U(VI)] = 50 ppm, initial pH = 0.5 ∼ 5.5 Solution 2: [U(VI)] = 50 ppm, [NaCl] = 0.1 M, initial pH = 4.0 Solution 3: [U(VI)] = 50 ppm, [CaCl2] = 0.1 M, initial pH = 4.0 Solution 4: [U(VI)] = 4.84 mM, [NaCl] = 0.1 M, initial pH = 3.18 Solution 5: [U(VI)] = 4.86 mM, 2,994 ppm boric acid/30% seawater, initial pH = 4.25 The uptake (%) and distribution coefficient (Kd. cm3/g) were estimated by counting the radioactivity using NaI(Tl) scintillation counter and liquid scintillation counter. In the simple Solution 1, the Kd values for zeolites increased linearly with equilibrium pH up to pH 7. The Kd value for tin hydroxide had a maximum profile around pH 7 and a relatively large Kd value above 104 cm3/g was obtained. In the presence of NaCl and CaCl2 (Solution 2 and 3), relatively large Kd values above 102 cm3/g were obtained, other than mordenite and clinoptilolite, and the effect of [Ca2+] on U(VI) uptake was larger than that of [Na+]. In Solution 4 containing high concentration of U(VI), the uptake(%) was considerably lowered, while that for zeolite A, X and Y was estimated over 20%. Similar tendency was observed in Solution 5, and, in the case of granulated potassium titanate, yellow precipitate was observed on the surface due to the increase of equilibrium pH up to 5.25. The adsorption behavior of U(VI) on inorganic adsorbents is mainly governed by three steps; ion exchange, surface precipitation of hydrolysis species and sedimentation depending on equilibrium pH, and hence it should be noted the change of U(VI) chemical species. These basic adsorption data are useful for the selection of inorganic adsorbents in the Fukushima NPS decontamination process.

In Japanese transuranic (TRU) waste disposal facilities, 129I is the most important key nuclide for the long-term safety assessment. Thus, the Kd values of I to natural minerals are important factor in the safety assessment. However, the degradation of cement materials in the repositories can produce high pH pore fluid which can affect the anion transport behavior. Therefore, it is necessary to understand the behavior of anions such as I− under the hyperalkaline conditions. The natural hyperalkaline spring water (pH>11) in the Oman ophiolite is known to be generated from the partly serpentinized peridotites. The spring water is characteristically hyperalkaline, reducing, low-Mg, Si and HCO3−, and high-Ca, while the river water is moderately alkaline, oxidizing, high-Mg and HCO3−. The mixing of these spring and river water resulted in the formation of secondary minerals. In the present study, the naturally occurring hyperalkaline conditions near the springs in Oman were used as natural analogue for the interaction between cement pore fluid and natural Mg-HCO3− groundwater. The present aim of this paper is to examine the conditions of secondary mineral formation and the anion uptake capacity of these mineral in this system. Water and precipitate samples were collected from the different locations around the spring vent to identify the effect of mixing ratios between spring and river water on mineral composition and water-mineral distribution coefficient of various anions. On-site synthesis was also carried out to support these data quantitatively. Aragonite was observed in all precipitates, while calcite, brucite and Mg-Al hydrotalcite-like compounds (HTlc) were also determined in some samples. Calcite was observed only closed to the springs. At locations far from the springs, calcite formation was inhibited due to high-Mg fluid from river water. Brucite was observed from the springs with relatively low-Al concentration and HTlc was the opposite. During the formation of the minerals at the mixing points, HCO3- in the river water was fixed as carbonate minerals such as in aragonite and calcite while H3SiO4− in the river water was dominantly fixed into interlayers and surfaces of HTlc. Iodine in spring and river water was mainly fixed in aragonite. Therefore, the uptake I− by secondary minerals can be expected at hyperalkaline conditions as observed at Oman hyperalkaline springs.

Development of selective adsorbents is very important subject for the effective multi-nuclide decontamination related to the severe accident of Fukushima Daiichi Nuclear power Station (Fukushima NPS). In this study, the adsorption properties for nine kinds of zeolites (Zeolite A, Zeolite X, Zeolite Y, Zeolite L, Modified Chabazite, Phillipsite, Erionite, Synthetic Mordenite, Natural Mordenite and Clinoptilolite) are evaluated in the presence of sodium salts, boric acid and seawater. The present study deals with (1) selective adsorption properties for single nuclide ions (Cs+, Sr2+, Eu3+, I−, UO22+, Am3+ and NpO2+), and (2) multi-nuclide adsorption properties of 26 elements (typical elements in Advanced Liquid Processing System (ALPS) in Fukushima NPP-1) for the above zeolites. The distribution coefficient (Kd, ml/g) and uptake (R, %) were estimated by batch method using NaI (Tl) scintillation counter, ICP-AES and AAS. Zeolites with different crystal structures have the diversity of the adsorption selectivity for various radioactive nuclides. Chabazite, mordenite and clinoptilolite with lantern or tunnel structure were very effective for the adsorption of monovalent Cs+ ions even in real seawater. Zeolite A and X with three-dimensional cage structures were effective for the adsorption of divalent Sr2+ and Co2+ ions under the practical condition (30% diluted seawater). Zeolite L was effective for the adsorption of Eu3+ ions under the practical condition. As for I− adsorption, Ag-zeolites are found to be effective, and the uptake (%) of I− (NaI in pure water) for Ag-zeolites was estimated to be above 98% in pure water. As for actinoid adsorption, the distribution profile, Kdvs pH, had a maximum depending on the hydrolysis pH. Zeolite A, Zeolite L and Zeolite X showed an excellent adsorption property for UO22+, Am3+ and NpO2+, respectively. Selective adsorption tendencies of different zeolites were evaluated for 26 elements referred to ALPS. Comparing the uptake results for different zeolites, the following tendency of adsorbability was observed. Mordenite had adsorption selectivity for monovalent alkali metal ions of Rb+ and Cs+. Zeolite A and X exhibited relatively high adsorption selectivity for divalent ions of Sr2+ and Co2+. Zeolite L had adsorption selectivity for trivalent lanthanide ions such as Ce3+ and Eu3+. These tendencies were the same as those without boric acid. Thus, the zeolites with diverse adsorption selectivity are effective for the multi-nuclide decontamination of radioactive contaminated water.

This study examined the sorption behaviors of iodine into CSH gel without dried processes, considering the repository system saturated with groundwater after the backfilling. In glove box saturated with N2 gas, each sample of CSH gel was synthesized with CaO, SiO2, and distilled water with liquid/solid ratio 20. Then, 1 mM iodine solution is added into the aqueous solution including the CSH gel with various Ca/Si molar ratios under the isothermal condition (298 K). In the results, even if the Ca/Si ratio is relatively small (<1.0), the distribution coefficients (Kd) of iodine on CSH gel without dried processes were two-order of magnitude larger than those with dried processes. For example, the value of Kd (ml/g) was about 380 in the case of 0.5 in Ca/Si molar ratio. Furthermore, it was confirmed the sorption behavior attain equilibrium in 24 hours. These suggest secondary mineral of CSH gel would retard the migration of anionic nuclides under the condition saturated with groundwater. In comparison, this study prepared also the co-precipitated samples of CSH gel and iodine, where the 1 mM iodine solution is added before curing the CSH gel. These distribution coefficients and the kinetics almost agreed with those mentioned above.

On the example of arable chernozems typical of different degrees of erosion, the change in their aggregate composition as a result of both the transport of soil material by small water flows and the degree of soil erosion is shown. It was established that when assessing the structural state of eroded soils, it is necessary to take into account the distribution of their size fractions and the structural coefficient.

The ground source heat pump system (GSHP) continuous operation will result in heat accumulation of the soil around the underground heat exchangers leading the descend operation performance of heat pump system. Based on experiment of GSHP system in summer season, the temperature distribution of humid soil around the vertical boreholes, the power consumption of the heat pump unit, the water temperature in the inlet and outlet of the underground heat exchangers, the heat release rate of per unit length of the buried pipes in humid soil and the cooling coefficient of performance (COP) for the heat pump unit were acquired during the different intermittent heat storage modes. This study investigated the impact of soil temperature change around the borehole wall on the performance of heat pump operation, the influence of intermittent heat storage on the soil temperature near the borehole wall and the performance of heat pump unit, and the effect of intermittent heat storage process on the recovery rate of soil temperature. The results showed that proper control of the operation and interval time of GSHP can effectively improve the soil temperature field around the underground heat exchangers and enhance the performance of GSHP system, thus achieving high efficiency operation of heat pump units.

In Fukushima NPP-1, large amounts of high-activity-level water (HALW) accumulated in the reactor, turbine building and the trench in the facility is treated by circulating injection cooling system. The development of highly functional adsorbents and stable solidification method contributes to the advancement of the decontamination system and environmental remediation. The present study deals with (1) preparation of insoluble ferrocyanide loaded zeolites, (2) selective uptake of Cs+ in seawater, (3) estimation of Cs immobilization ratio and stable solidification. Various kinds of Cs-selective composites loaded with insoluble ferrocyanides (CoFC, NiFC) into the zeolites (zeolite A (A51, A-51J), zeolite X (LSX), chabazite (modified chabazite) and natural mordenite (SA-5)) matrices have been prepared using successive impregnation/precipitation methods by Tohoku University. As for Cs+ adsorption, these composites had relatively large uptake (%) above 95%, distribution coefficients (Kd) above 103 cm3/g and excellent adsorption kinetics even in seawater. The immobilization ratio (%) of Cs for the CoFC saturated with Cs+ was estimated at different calcination temperatures up to 1,200°C in advance. The immobilization ratio was less than 0.1% above 1,000°C, indicating that the adsorbed Cs+ ions are completely volatilized and insoluble ferrocyanides had no immobilization ability for Cs. In contrast, the insoluble ferrocyanide-loaded zeolites had excellent Cs immobilization ability; in the case of insoluble ferrocyanide-loaded natural zeolites (NiFC-SA-5, CoFC-modified chabazite), the immobilization ratio was above 99% and 96% even after calcination at 1,000°C and 1,100°C, respectively, indicating that nearly all Cs ions are immobilized in the sintered solid form. On the other hand, the immobilization ratio for the insoluble ferrocyanide-loaded A and X zeolites (NiFC-A (A51, A51J), NiFC-X) tended to decrease with calcining temperature; for example, the immobilization ratio for NiFC-X at 1,000°C and 1,100°C was estimated to be 74.9% and 55.4%, respectively, and many spots concentrating Cs were observed on the surface. The difference in immobilization behavior between natural zeolites and synthetic ones is probably due to the phase transformation and surface morphology at higher temperature above 1,000°C. The stable solidification of insoluble ferrocyanides was thus accomplished by using the excellent Cs immobilization abilities of zeolite matrices (Cs trapping and self-sintering abilities).

ABSTRACT An in-depth understanding of the mechanical behaviors of sediments is important to maintain reservoir stability and sustainable mining during natural gas hydrate (NGH) dissociation. In this work, a fully coupled thermal-hydro-mechanical–chemical (THMC) simulator, i.e. DEHydrate, is developed for studying the multiphysics processes and predicting the mechanical behavior during NGH dissociation involving solid-liquid-gas flow, heat transfer, NGH phase change and solid deformation. The numerical solution is obtained by using the fully implicit finite element method, where the higher order elements are used for solid deformation while lower order elements are used for gas-liquid flow and thermal diffusion. The results obtained from the present model are compared with those from other numerical simulators proposed in the Second International Gas Hydrate Code Comparison Study by conducting a benchmark problem. The evolution trends of the mechanical responses, such as NGH saturation, pressure, temperature, radial displacement and gas and water production rates, are roughly the same. The permeability coefficient is also directly related to the hydrate saturation, resulting in a "hump" in the distribution of pressure and temperature near the dissociation front. INTRODUCTION Natural gas hydrate (NGH), widely distributed in shallow seabed or permanent frozen region with a global reserve of around 7.5×1018 m3 (Kvenvolden and Lorenson), has a high energy density and high combustion efficiency (Yan et al. 2020). Safely and sustainably extracting NGH commercially can effectively relieve the global energy pressure and contribute to achieving carbon reduction goals. However, the current production technology can only achieve 1/17 of the commercial production requirement (Wu et al. 2021) due to some chanllenges such as marine slope collapse, seabed subsidence and sand production, and thus needs more research on hydrate dissociation behavior. As a relatively common and straightforward way, numerical simulation provides a useful tool for predicting short- and long-term behavior of hydrate exploitation. Hydrate dissociation involves solid-liquid-gas flow, heat transfer, NGH phase transition and mechanical deformation. Many mathematical models have been developed to simulate the mechanical behavior of reservoir during hydrate dissociation. Based on the thermodynamic constitutive law, Sun et al. (2018, 2015) developed a thermal-hydro-mechanical–chemical (THMC) model to describe dissociation process by using the commercial finite element software COMSOL and show that decoupling of deformation-seepage process would overestimate the NGH dissociation rate. Kimoto et al. (2007, 2010) established a two-dimensional THMC dissociation model, and pointed out that the reservoir deformation is affected mainly by water-gas production and dissipation and decrease in soil strength. However, application of this model is limited by the number of elements and simulation time, even if the influence of heat convective is neglected. Therefore, most of the existing models have been simplified to some extent, not fully coupling the multiphysics process of hydrate dissociation. Therefore, it is very necessary to develop a fully coupled THMC model for simulating the hydrate dissociation and studying its mechanical behavior.

ABSTRACT: This study develops a computer program to assist in rating the Q-system of jointed rock masses. The analysis is based on photogrammetric analysis of point clouds. Three key rating terms, rock quality designation (RQD), joint set number (Jn), and joint roughness number (Jr), can be calculated by the program without an expert's manual rating. To identify major outcrop joint surfaces, the random sample consensus algorithm was employed. Subsequently, we calculate the weighted joint density (wJd) and its corresponding RQD based on the major joint surface. The spherical K-means clustering was involved to determine the number of dominant joint sets, which assist the acquiring of the Jn value. In addition, the a/L method was adopted to calculate the joint roughness coefficient (JRC) and further convert it into Jr. The results of our analysis align with manual Q-system ratings, demonstrating the feasibility of the proposed computer program. 1. INTRODUCTION The Q-system (Norwegian Geotechnical Institute, 2022), a semi-quantitative rock mass classification method proposed by Barton in 1974 (Barton et al., 1974) has been widely used by geotechnical engineers (Akram et al., 2019; Barton, 2002). It is used for evaluating the rock mass characteristics of underground openings, providing engineers with the corresponding excavation methods and suggesting appropriate supports (Akram et al., 2019). Moreover, it can be applied in field mapping to estimate the quality of rock masses, which has been validated worldwide. However, its applicability to the quality evaluation of jointed rock may be limited. First, because of the rock mass heterogeneity, engineers must perform several Q ratings around the outcrop to obtain the Q value distribution. However, outcrops may sometimes be covered by plants or soil or exposed at hard-to-reach locations. Therefore, the lack of a survey method limits the quality of the rating. On the other hand, multiple landslides occurring simultaneously in a region during typhoon season are common, necessitating a rapid survey for emergency situations. Geologists are required to conduct all investigation steps rapidly, including photogrammetry, survey, sampling, and especially, Q-system rating. Therefore, reducing the survey time is critical. The Q-system is calculated using the following equation: (equation) where RQD is the sum of the length of all core pieces that are more than 10 cm long as a percentage of the total core length; Jn is the rating for the number of joint sets; Jr is the rating for the roughness of the least favorable of these joint sets in the same domain; Ja is the rating for the degree of alteration or clay filling of the least favorable of these joint sets or filled discontinuities in the same domain; and Jw is the rating for the water inflow and pressure effects, which may outwash discontinuity infillings in the same domain; SRF is the rating for faulting, for strength/stress ratios in hard massive rocks, for squeezing, or for swelling in soft rock in the same domain. A detailed rating of each parameter can be obtained from the handbook(Norwegian Geotechnical Institute, 2022). For the Q-system, three of these six parameters, RQD, Jn, and Jr, are highly related to the distribution and the roughness of the joints. Therefore, these three parameters can be calculated by evaluating the spatial information from the outcrop surface.