Comments on “Uranium solution-mineral equilibria at low temperatures with applications to sedimentary ore deposits”

The necessity of considering protonation and complexation of weak acid ligands, for proper interpretation of their effect on solution equilibria, has been demonstrated. The solubility of uraninite in presence of σF = 2 ppm has been recalculated to be 0.88 ppb at pH 2.     

Closed-Form Solution of Critical Inclination for Rock Slope with Weak Plane

Plane failure of rock slope is highly related to the inclination of the weak plane. The inclination of the weak plane is a general function of factors including: height of slope, factor of safety, horizontal coefficient of earthquake influence, inclination of slope, unit weight of rockmass, cohesion and friction angle on the plane. The closed-form solution of the critical inclination of the weak plane corresponding respectively is derived under two conditions (i.e., without earthquake and with earthquake), because the critical height of slope and the critical factor of safety are considered to and are easy to be adjusted in engineering practice. In the end, the relations between derived critical closed-form solution and each parameter are illustrated with an example.

     

Impact of FDI on energy efficiency: an analysis of the regional discrepancies in China

Under the assumption of “technology will not be forgotten,” this study estimates and decomposes the total-factor energy efficiency (TFEE) using the sequential data envelopment analysis-Malmquist productivity index and directional distance functions that consider undesirable output based on the provincial panel data of China from 2001 to 2013. On this basis, we make an empirical study of the relationship between foreign direct investment and energy efficiency with the dynamic panel model. The result shows that over the sample period, on the national level, the trend of the TFEE was upward, but the growth rate showed a downward trend. On the regional level, the TFEE in the eastern region was higher than that in the central and western regions. In addition, foreign direct investment enhanced the energy efficiency significantly, which demonstrated that the “pollution halo” effect was greater than the “pollution haven” effect. It is indicated that technical progress was the main cause of the increase in the TFEE, but technical efficiency played the opposite role. This conclusion remains valid even if the TFEE indicator is changed into the single-factor energy efficiency indicator.

     

Physical model tests to determine the mechanism of submarine landslides under the effect of sea waves

Submarine landslides are a common type of disaster which threaten property and the safety of human life. To effectively prevent and control such disasters, we conduct a series of large-scale physical model tests to determine the mechanism of submarine landslides. First, a large-scale physical model test system is designed and developed, including flume test frame, wave-making system, wave-absorbing system, and data monitoring system. In the tests, we investigate the effect of different sea waves by changing the parameters of the wave-making system and the influence of the slope inclination by constructing different models. Data regarding the wave pressure acting on the slope surface, seepage pressure, and displacement are monitored during the test procedure. The test results show that the seepage pressure in the faults varies cyclically with the sea waves and is lower at internal points than at outcrops. If the wave loading time is sufficiently long, the seepage pressure and displacement deformation in the fault zone will gradually increase. In other words, failures in fault zones precede submarine landslides. The weak fault zone provides the preferred sliding surface, and the sea waves supply the external dynamic energy for submarine landslides. The conclusions provide guidelines for similar engineering and research.

     

Thermal Model of Changes in the Thickness of the Continental Lithosphere over Time

The results of numerical modeling for the increase and decrease in the thickness of a highly viscous continental lithosphere under whole-mantle convection on a time interval of 3.5 Ga were considered. It was found that the initial period of lithosphere growth took about 1.1 Ga, followed by a period of its slow thinning because of gradual heating of the mantle by several hundred degrees from the thermal insulation effect of the lithosphere.

     

Experimental investigation of dry density effects on dielectric properties of soil–water mixtures with different specific surface areas

The dielectric constant of soil is used to estimate its water content in a range of applications. Unlike the widely known effect of water content on the soil dielectric constant (consistent direct proportionality), only a limited number of studies have reported the effects of soil dry density, however, with equivocal results. This paper, therefore, investigates the effects of dry density or degree of compaction on the dielectric constant of five different soil types. The results of the experimental work for the soils ranging from sand to Bentonite clay with distinct specific surface areas were evaluated based on the use of two simple mixture models (De Loor and Birchak). The effects of dry density on the soil dielectric constant were found to be soil type dependent. This is demonstrated by the experimental data and further proven by the modified De Loor model. The behavior is shown to be defined by the changes in the free water, bound water, and solid particle volume fractions, ultimately controlled by the soil specific surface area. The dielectric constant changes from being directly proportional to dry density to inversely proportional at a threshold specific surface area of between 122 and 147 m²/g. Supported by the experimental observations, parametric analysis has revealed that the range for the dielectric constant of bound water was found to be 9–37, while the geometrical parameter α in the Birchak model was found to be 0.4–0.8.

     

The Stability of Upper Bound Analysis of Soft Rock Tunnel Faces Under Different Underground Water Levels

The effect of underground water levels on the stability of soft rock tunnel faces was analyzed in this paper. The underground water levels was divided into three cases, and the Hoek–Brown failure criterion was introduced into the kinematic approach by "tangent method", then three kinds of stability analysis model of tunnel faces under different underground water levels was constructed. Based on the principle of virtual power, the expressions of supporting force on the tunnel faces of soft rock under different underground water levels were derived. Moreover, the optimal upper limit solution of the supporting force on tunnel faces was obtained by using the sequential quadratic programming algorithm with Matlab software. After that, the effect of underground water levels on the supporting force of tunnel faces was analyzed, and the damage range of tunnel faces under different underground water levels was given. This paper provides some reference value for setting parameters of shield tunneling in water-rich section.

     

Evolution of Maser Emission in the Region of Active Star Formation G43.8–0.1. I. OH Maser Emission at 18 cm

The results of observations of OH maser emission in the star-forming region G43.8–0.1 are presented. In spite of strong flux-density variations in the main lines at 1665 and 1667 MHz, the radial velocities of the spectral features varied only slightly. The main spectral features are identified with maser spots in previously published maps for epochs 1993 and 2001. It is suggested that the regions of OH maser emission may be elongated, nonuniform structures with weak radial velocity gradients (larger-scale analogs of water-maser filaments). The line-of-sight magnetic fields are determined for two Zeeman pairs, which remained essentially constant over at least 17 years.

     

Performance studies of the fixed stress split algorithm for immiscible two-phase flow coupled with linear poromechanics

In this work, we measure the performance of the fixed stress split algorithm for the immiscible water-oil flow coupled with linear poromechanics. The two-phase flow equations are solved on general hexahedral elements using the multipoint flux mixed finite element method whereas the poromechanics equations are discretized using the conforming Galerkin method. We introduce a rigorous calculation of the update in poroelastic properties during the iterative solution of the coupled system equations. The effects of the coupling parameter on the performance of the fixed stress algorithm is demonstrated in two field studies: the Frio oil reservoir and the Cranfield injection site.

     

Stability of a numerical scheme for methane transport in hydrate zone under equilibrium and non-equilibrium conditions

In this paper we carry out numerical analysis for a family of simplified gas transport models with hydrate formation and dissociation in subsurface, in equilibrium and non-equilibrium conditions. These models are adequate for simulation of hydrate phase change at basin and at shorter time scales, but the analysis does not account directly for the related effects of evolving hydraulic properties. To our knowledge this is the first analysis of such a model. It is carried out for the transport steps while keeping the pressure solution fixed. We frame the transport model as conservation law with a non-smooth space-dependent flux function; the kinetic model approximates this equilibrium. We prove weak stability of the upwind scheme applied to the regularized conservation law. We illustrate the model, confirm convergence with numerical simulations, and illustrate its use for some relevant equilibrium and non-equilibrium scenarios.

     

The effect of directed technical change on carbon dioxide emissions: evidence from China’s industrial sector at the provincial level

Technical change has a pivotal role to play in low-carbon development. Recent research has offered different insights regarding the effect of technical change on CO₂ emissions but ignored the bias of technical changes which lead to changes in CO₂ emissions. To fill the gap, this paper uses the 2008 to 2015 provincial-level data on China’s 22 industrial sub-sectors to investigate both the effect of directed technical change on CO₂ emissions and its heterogeneity. We find that the technical change in most industrial sectors in China was capital-biased, although a labor-biased trend was evident. Labor-biased technical change is conducive to CO₂ reduction, while capital-biased technical change has the opposite effect. Moreover, this effect is different by developmental periods, industries, and regions. Therefore, we propose that the government promotes labor-biased technical change based on the differentiated characteristics.

     

Characteristics and failure mechanism of landslides along highways triggered by 2021 Ms6.4 Yangbi earthquake

On May 21, 2021, at 21:48, the Ms6.4 Yangbi earthquake struck Dali prefecture, Yunnan province, China; the maximum PGA reached 714.78 gal, causing 37 casualties and infrastructures damage. A field investigation demonstrated that seismic landslides were concentrated along the G56 Hangrui and Dayangyun highways, classified as local rock falls and shear slides. The shear slides were more severe than the local rock falls and were located along the Dayangyun highway, which was still under construction when the earthquake occurred, severely impacting following engineering activities. Typical shear slides caused by the earthquake were selected for detailed investigations; electrical resistivity topography (ERT) was conducted to study the failure mechanism. The ERT results indicated that the sliding surface was located at the interface between the overburden layer and the underlying rock stratum. The slope failures along the Dayangyun highway were characterized by several tensile cracks on the rear edge, a relatively short displacement, and an accumulation at the toe of the excavated slope where reinforcement measures had not yet been completed. The combined effect of engineering activities and a geological structure provided favorable conditions for slope failure. In addition, seismic motion triggered the landslides; however, engineering activity was a specific and significant factor contributing to the shear slides during the Yangbi earthquake. Excavation and incomplete construction reduced the stability of the overburden soil layer. Although the scale of the seismic landslides in the Yangbi earthquake was generally small, the coming rainy season after the earthquake may contribute for sliding again.

     

Isotope compositions of C and O of magmatic calcites from the Udachnaya–East pipe kimberlite,Yakutia

It has been demonstrated for the first time that the isotopic compositions of carbon (δ¹³C) in magmatic calcites from the Udachnaya–East pipe kimberlite groundmass varies from–2.5 to–1.0‰ (V-PDB), while those of oxygen (δ¹⁸O) range from 15.0 to 18.2‰ (V-SMOW). The obtained results imply that during the terminal late magmatic and postmagmatic stages of the kimberlite pipe formation, the carbonates in the kimberlite groundmass became successively heavier isotopically, which indicates the hybrid nature of the carbonate component of the kimberlite: it was formed with contributions from mantle and sedimentary marine sources.

     

Finite element analyses of rate-dependent thermo-hydro-mechanical behaviors of clayey soils based on thermodynamics

Clayey soils in the vicinity of energy geostructures may be exposed to long-term periodic thermal cycles. The creep and consolidation behaviors of the clayey soils can be both rate-dependent and temperature-dependent, and the underlying physical mechanisms are merely investigated theoretically. In this study, based on the theory of thermodynamics, a fully coupled thermo-hydro-mechanical (THM) finite element (FE) program for saturated soils is developed for this purpose. The FE formulation accounts for the combined effect of rate and temperature through the novel concept of granular temperature. Simulations of THM coupled validation cases and a series of experimental observations on the soft Bangkok clay are carried out. The obtained numerical results exhibit good agreement with analytical solutions and laboratory measurements. It is found that three fundamental physical mechanisms contribute to the irreversible thermal contraction observed for normally consolidated and lightly overconsolidated clays under drained thermal cycles: (1) the thermal creep excited by mass exchange from adsorbed water to free water; (2) the mechanical creep induced by confining stresses; and (3) the increase in granular packing caused by the thermal expansion of soil particles. The thermal contraction generally stabilizes within a few thermal cycles, as a result of the noticeable reduction in the thermal creep rate. It is further demonstrated that the transient heat transfer and the heating rate can greatly influence the deformation of clays subjected to thermal cycles.

     

An Uncertainty Quantification Framework for Studying the Effect of Spatial Heterogeneity in Reservoir Permeability on CO2 Sequestration

A new uncertainty quantification framework is adopted for carbon sequestration to evaluate the effect of spatial heterogeneity of reservoir permeability on CO₂ migration. Sequential Gaussian simulation is used to generate multiple realizations of permeability fields with various spatial statistical attributes. In order to deal with the computational difficulties, the following ideas/approaches are integrated. First, different efficient sampling approaches (probabilistic collocation, quasi-Monte Carlo, and adaptive sampling) are used to reduce the number of forward calculations, explore effectively the parameter space, and quantify the input uncertainty. Second, a scalable numerical simulator, extreme-scale Subsurface Transport Over Multiple Phases, is adopted as the forward modeling simulator for CO₂ migration. The framework has the capability to quantify input uncertainty, generate exploratory samples effectively, perform scalable numerical simulations, visualize output uncertainty, and evaluate input-output relationships. The framework is demonstrated with a given CO₂ injection scenario in heterogeneous sandstone reservoirs. Results show that geostatistical parameters for permeability have different impacts on CO₂ plume radius: the mean parameter has positive effects at the top layers, but affects the bottom layers negatively. The variance generally has a positive effect on the plume radius at all layers, particularly at middle layers, where the transport of CO₂ is highly influenced by the subsurface heterogeneity structure. The anisotropy ratio has weak impacts on the plume radius, but affects the shape of the CO₂ plume.     

Joint inversion of groundwater flow,heat, and solute state variables: a multipurpose approach for characterization and forecast of karst systems

Characterization of karst systems and forecast of their state variables are essential for groundwater management and engineering in karst regions. These objectives can be met by the use of process-based discrete-continuum models (DCMs). However, results of DCMs may suffer from inversion nonuniqueness. It has been demonstrated that the joint inversion of observations regulated by different natural processes can tackle the nonuniqueness issue in groundwater modeling. However, this has not been tested for DCMs thus far. This research proposes a methodology for the joint inversion of hydro-thermo-chemo-graphs, applying to two small-scale sink-to-spring experiments at Freiheit Spring, Minnesota, USA. In order to address conceptual uncertainty, a multimodel approach was implemented, featuring seven mutually exclusive variants. Spring hydro-thermo-chemo-graphs, for all the variants simulated by MODFLOW-CFPv2, were jointly inverted using a weighted least squares algorithm. Subsequently, models were compared in terms of inversion and forecast performances, as well as parameter uncertainties. Results reveal the suitability of the DCM approach for simultaneous inversion and forecast of hydro-physico-chemical behavior of karst systems, even at a scale of meters and seconds. The estimated volume of the tracer conduit passage ranges from approximately 46–51 m³, which is comparable to the estimate from the flood-pulse method. Moreover, it was demonstrated that the thermograph and hydrograph contain more information about aquifer characteristics than the chemograph. However, this finding can be site-specific and should depend on the analysis scale, the considered conceptual models, and the hydrological state, which are potentially affected by minor unaccountable processes and features.

     

A note on the Raman spectra of water-bearing albite glasses

The Raman spectra of albite glasses with 4.5 and 6.6 weight percent water have been obtained, and are compared with that of a dry sample. The hydrous glasses show bands near 3600 cm^?1 due to O-H stretching, and a previously unreported weak band near 1600 cm^?1 due to bending of molecular H₂O. Other weak spectral features are discussed, and the effect of dissolved water on the aluminosilicate framework vibrations is considered.     

Effect of tamping interval on consolidation of dredged slurry using vacuum preloading combined with dynamic consolidation

The effect of combining vacuum preloading and low-energy dynamic consolidation is predominantly controlled by the tamping interval time. It is, therefore, imperative to identify a suitable parameter and optimise the tamping interval time. In this study, the effect of the tamping interval time on the consolidation of slurries was investigated by conducting laboratory model tests. Consequently, various tamping interval times were obtained by controlling the dissipation of pore water pressure at different levels of 20%, 40%, 60%, 80%, and 100% to determine the optimal interval time. In terms of surface settlement variation, dissipation of pore water pressure, and distributions of the water content and shear strength variation profile, it was shown that a rubber soil state was reached at a dissipation rate of 20% pore water pressure. When the tamping interval time was set to a dissipation rate of 80% pore water pressure, the consolidation effect was optimal.

     

A Review on the Design,Applications and Numerical Modeling of Geocell Reinforced Soil

For improving the stability and load carrying capacity of weak subgrade, strengthening methods are to be followed in the field. Among the various approaches, geocells have been identified as an effective soil reinforcement technique for improving soft subgrade behaviour. The three-dimensional honeycomb structure of geocell offers more lateral confinement to the infill soil resulting in improved load carrying capacity. This led to the widespread use of geocells for different geotechnical applications like pavements, foundations, embankments, slope protection, erosion control etc. Many researchers in the past have confirmed the suitability of geocell reinforcement through their experimental, numerical and field studies. In this paper, a comprehensive review of the reinforcement mechanisms, design aspect and numerical modelling techniques of geocell reinforced soil is provided. In addition, this paper highlights the various field application scenarios where different types of geocells have been used and explores the research challenges and scope for further research in this field.