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Carbon foam was utilized to develop corrugated structured packing in distillation for the first time. The hydrodynamics and mass transfer performance of CFP-400X and CFP-500W with 60 and 75° corrugation angle were determined by total reflux experiments. The results indicate that increasing the corrugation angle will improve the capacity but decrease the mass transfer efficiency. Comparisons among CFP-400X, SCFP-500X, BX-500, and B1-500X were made with respect to the performance of hydrodynamics and mass transfer. CFP-400X shows advantages in terms of capacity and efficiency compared with the other two metal packings. SCFP-500X exhibits a higher mass transfer efficiency than CFP-400X because of its superior wettability of test liquid which is supported by the liquid flow behavior experiment. [ABSTRACT FROM AUTHOR]

Underestimation of raw material reserves contained in gold mining waste dumps results in tense socio-economic situation in gold mining regions. Efficient management of gold mine waste is only possible with the new and sound technologies of waste preparation and deep conversion with a view to recovering valuable components. Aimed at creation of such technology, the large-scale theoretical and experimental research has been undertaken in order to study the nature and rate of influence exerted by basic process factors on migration and concentration of gold particles in gold mine waste. [ABSTRACT FROM AUTHOR]

Fractured seepage is an important factor affecting the interface stability of rock mass. It is closely related to fracture properties and hydraulic conditions. In this study, the law of seepage in a single fracture surface based on modified cubic law is described, and the three-dimensional discrete element method is used to simulate the dam foundation structure of the Capulin San Pablo (Costa Rica) hydropower station. The effect of construction joints and developed structure on dam stability is studied, and its permeability law and sliding stability are also evaluated. It is found that the hydraulic-mechanical coupling with strength reduction method in DEM is more appropriate to use to study the seepage-related problems of fractured rock mass, which considers practical conditions, such as the roughness of and the width of fracture. The strength reduction method provides a more accurate safety factor of dam when considering the deformation coordination with bedrocks. It is an important method with which to study the stability of seepage conditions in complex structures. The discrete method also provided an effective and reasonable way of determining seepage control measures. [ABSTRACT FROM AUTHOR]

This paper aims at revealing mechanical behavior of volcanic coarse grained soils subjected to seepage flow. In order to accomplish the purposes, a series of upward seepage tests was conducted to grasp piping phenomenon in compacted volcanic soils and to investigate the effects of differences in compaction conditions on its behavior. In the experiments, the movement of soil particles in seepage flow tests was observed using an X-ray CT scanner in detail. The test results showed that destabilization of soil structures due to seepage flow is changed depending on an increase of amount of finer soil particles, and that internal erosion is induced by loss of fine particles with the changes in void ratio. As a result, a significant variation in hydraulic conductivity was generated. Additionally, internal stability of volcanic soils under several geotechnical conditions was elucidated by empirical criterion. In the consideration of the results, it was shown that volcanic coarse grained soil including pumice particles with a low specific gravity was internally unstable. Based on the results, a geotechnical evaluation was discussed for the stability of soil structures such as embankments constructed by volcanic coarse grained soils. [ABSTRACT FROM AUTHOR]

During the installation process of suction caisson in sandy seabed, the applied suction not only produces a downward driving force, but also decreases the penetration resistance to the caisson. In this paper, numerical studies were performed to investigate the characteristics of seepage flow around the caisson as well as its effects on the wall friction and the caisson tip resistance. A simplified approximation method was proposed to predict the reduction of penetration resistance. In particular, for the case of sandy seabed interbedded by a layer of low-permeability soil, the seepage flow will be suppressed with the caisson tip getting closer to the low-permeability layer. The seepage flow around the caisson was first studied, and then a new approximation for the seepage-induced resistance reduction, considering the effect of low-permeability layer, was proposed for the engineering practice. [ABSTRACT FROM PUBLISHER]

The authors introduce an experimental method that focuses on the flowthermal relation and the visual observation of heat distribution around a cooling pipe in sand under the flow condition. This experiment aims to understand the effect of seepage flow on the heat transfer behavior of sand under cooling and freezing conditions due to a vertically buried heat exchanger pipe. This method combines a flow test, cooling or freezing processes, and the visual observations of temperature profiles with saturated Toyoura sand as the heat transfer medium. Avertical copper pipe inserted into the sand medium is used as the thermal exchanger, while an infrared thermograph is used to measure and visualize the surface-temperature profile of the specimen. The heat transfer distribution behavior is investigated by conducting a series of cooling and freezing experiments on the specimens with variation of the flow rate condition, initial condition, and pipe depth. The thermograph observation results show how water flow obviously affects the shape and intensity of the heat distribution. [ABSTRACT FROM AUTHOR]

The artificial freezing in the clay-sand stratum under seepage flow conditions involves the hydro-ice-salt-crystalline-thermal-mechanical coupling process. A theoretical model is derived to investigate the influences of water seepage on the freezing process in the clay-sand stratum. The good agreements between the results from the theoretical model and laboratory tests in the literature verified the accuracy of the proposed model. Parametric studies are conducted to investigate the influences of the seepage velocities and temperature gradients on the spatial distributions. It is found that the ice contents, crystalline salt contents and adsorbed salt contents distribution profiles in the clay-sand stratum are nonlinearly distributed with a cliff distribution curve existing on their interface. The crystalline salt contents in the clay layer are higher than those in the sand layer due to the influence of water seepage and heat transfer. The adsorbed salt contents in the frozen area account for 2% of the total salt contents, but those in the unfrozen area account for 8% of the total salt contents. Due to the volume expansion caused by the soil skeleton deformation, thickness of fractional ice, ice frost heave deformation and salt swelling deformation, the soil deformation distribution curves in the clay-sand stratum are in a bilinear shape. • Theoretical model is derived to investigate the influences of water seepage on artificial freezing along clay-sand interface. • The components spatial distributions under different seepage velocities and temperature gradients in the clay-sand stratum are analyzed. • The proposed model is capable to calculate the artificial and seasonal frozen in the non-uniform soil stratum. [ABSTRACT FROM AUTHOR]

Interfacial seepage on soil-structure interface is common in water-related engineering, such as dam, culvert, water tunnel, foundation pit, etc. As a weak part in the project, seepage failure on soil-structure interface has caused many project accidents. However, there are few studies on the seepage mechanism analysis of soil-structure interface. In this paper, a series of numerical tests of interfacial seepage are carried out using CFD-DEM coupling method. The seepage mechanism and characteristics of different soil layers in the seepage device are analyzed and a formula for calculating the critical hydraulic gradient of the interface is discussed. The main conclusions are as follows: (1) The seepage flow on soil-structure interface will go through three stages: stability stage, transition stage and particle erosion stage; (2) The porosity and flow velocity of soil on the interface are greater than those in the far-field soil at the beginning of seepage flow; (3) The particle erosion on the soil-structure interface occurs earlier and the erosion degree is more serious than that of the far-field soil; (4) The critical hydraulic gradient of the interface rises nonlinearly with the increase of the degree of soil compaction; (5) The formula for calculating the critical hydraulic gradient of the interface could predict the numerical test results well. [ABSTRACT FROM AUTHOR]

Most of the current studies on the bearing capacity of rock foundations follow the Hoek-Brown (HB) criterion, but all adopt the generalized tangent technique or the multi-tangent approach, which does not reflect the essence of the nonlinear dependence of the Hoek-Brown criterion. Therefore, a modified unilateral failure mechanism is proposed in the paper, using which the bearing capacity of shallow strip footings considering seepage and seismic forces is evaluated. Use of a statics-like approach for seepage condition and a modified pseudo-dynamic method for seismic condition. The comparison with the results of other literature confirms the feasibility and effectiveness of the study in the paper, while the parametric analysis shows that a smaller upper bound solution is yielded based on the failure mechanism proposed in this paper, and the horizontal gradient ratio, the horizontal factor of seismic acceleration, the normalized frequency, the geological strength index, the disturbance coefficient, and the rock type-dependent parameter all have significant effects on the bearing capacity of rock foundations. In addition, the analysis of the working conditions considering both seepage and seismic forces confirmed the dominance of seismic forces. The results of the superposition treatment between different working conditions are inaccurate, which will underestimate the foundation bearing capacity and cause a waste of cost. This paper develops a more accurate method of assessing the bearing capacity of rock foundations and gives a table of coefficients that can be adopted in engineering practice. [ABSTRACT FROM AUTHOR]

• A widely used mapping in water waves problems is newly applied to seepage flows. • The proposed σ -mapping transforms the time-dependent water table into a fixed boundary. • Steady and unsteady seepage problems are analyzed, with and without recharge. • The method is in excellent agreement with the exact Polubarinova-Kochina solution for the dam problem, and with other solutions in the literature. Regional groundwater flow forecasting is frequently accomplished using model equations based on Darcy's law, the continuity equation, and kinematic and dynamic boundary conditions for a time-dependent water table, to predict hydraulic heads and fluxes. For homogeneous and isotropic aquifers, the model reduces to Laplace's equation for the hydraulic head and a transient non-linear free surface boundary condition. These equations are solved in the literature and in computer packages by a variety of numerical methods, including finite difference, finite element, and boundary element methods. The solution of this model is not simple and subject to instability problems. Computations in a vertical plane using finite-difference methods are not easy due to the irregular mesh needed near a highly curved water table, frequently involving smoothing of the numerical results to ensure stability. A technique to avoid the complications related to mesh generation near a curved boundary and its tracking entails using mappings to produce transformed domains. However, this is not so frequent to compute unsteady seepages. In particular, the so-called sigma mapping is widely used to model irrotational water waves; it applies to any flow involving a time-dependent free surface boundary. This mapping transforms the domain into a rectangle, so that the free surface becomes static in the transformed plane. There is close similarity between the mathematical model describing irrotational water waves and that of unsteady seepage flow, e.g., both are governed by Laplace's equation involving relevant boundary conditions at the moving boundary. Both moving free surfaces are different in character, e.g., the seepage is dissipative whereas the water wave is dispersive. However, it is possible to transfer mathematical approximations between both fields of research. This transfer is exploited in this work and the sigma mapping is newly and successfully applied to seepage flows involving both a steady and unsteady water table either receiving, or not, a recharge from rainfall or an artificial source. [ABSTRACT FROM AUTHOR]

Centrifugal model testing has been widely used to study the stability of levees. However, there have been a limited number of physical studies on levees where the velocity of increasing water levels was considered. To investigate the behavior characteristics of reservoir levees with different velocities of increasing water levels, centrifugal model tests and seepage-deformation coupled analyses were conducted. Through this study, it was confirmed that increasing water levels at higher velocities induces dramatic increases in the displacement, plastic volumetric strain and risk of hydraulic fracturing occurring in the core of the levee. Hence, real-time monitoring of the displacement and the pore water pres­sure of a levee is important to ensure levee stability.

• A physical model test based on cross passage freezing was conducted. • A hydro-thermal coupling model of AGF was proposed. • The effect of four indicators on formation of frozen wall was investigated. Artificial ground freezing is an environmentally friendly and reliable method for ground improvement during subway cross passage construction under variable hydrological conditions. However, natural or induced seepage flow influences significantly the closure of frozen wall, as it supplies a substantial source of heat. In this study, a physical model test was conducted based on the freezing project of a subway cross passage in Beijing Subway Line 19. A series of thermistors were installed in some representative locations to measure the temperature distribution and further calculate power demand. Besides, a hydro-thermal coupling model of freezing process under seepage conditions was derived to consider the variations of physical and thermodynamic parameters of the porous media and the latent heat of ice/water phase transition. The numerical approach was validated by the experimental results. Furthermore, four crucial indicators affecting the closure time during AGF process were quantitatively evaluated. The results showed that the closure time at seepage velocities of 0, 25.6 and 51.2 m/d were respectively 60, 110 and 441 min. Nevertheless, it was impossible to form continuous frozen bodies at 76.8 m/d. Among these indicators, the seepage velocity had the greatest effect on the thickness and shape of frozen body, while seepage temperature had the least impact. [ABSTRACT FROM AUTHOR]

Centrifugal model testing has been widely used to study the stability of levees. However, there have been a limited number of physical studies on levees where the velocity of increasing water levels was considered. To investigate the behavior characteristics of reservoir levees with different velocities of increasing water levels, centrifugal model tests and seepage-deformation coupled analyses were conducted. Through this study, it was confirmed that increasing water levels at higher velocities induces dramatic increases in the displacement, plastic volumetric strain and risk of hydraulic fracturing occurring in the core of the levee. Hence, real-time monitoring of the displacement and the pore water pressure of a levee is important to ensure levee stability. [ABSTRACT FROM AUTHOR]

On a gabion stepped chute, the steps contribute to the dissipation of turbulent kinetic energy, free-surface aeration may be intense, and there are complex interactions between the free-surface flow and seepage motion. Detailed measurements were conducted in a relatively large gabion stepped spillway model. Using a combination of high-speed movies and phase-detection probe measurements, the air--water flow properties in the step cavities and in the gabions were documented. Strong air--water exchanges between seepage and stepped cavity flows were observed. The data showed a complex bubbly seepage motion in the gabions associated with a high level of interactions between seepage and free-surface flows, leading to a modification of the step cavity recirculation and lesser flow resistance. [ABSTRACT FROM AUTHOR]

Artificial ground freezing is an environmentally friendly technique to provide temporary excavation support and groundwater control during tunnel construction under difficult geological and hydrological ground conditions. Evidently, groundwater flow has a considerable influence on the freezing process. Large seepage flow may lead to large freezing times or even may prevent the formation of a closed frozen soil body. For safe and economic design of freezing operations, this paper presents a coupled thermo-hydraulic finite element model for freezing soils integrated within an optimization algorithm using the Ant Colony Optimization (ACO) technique to optimize ground freezing in tunneling by finding the optimal positions of the freeze pipe, considering seepage flow. The simulation model considers solid particles, liquid water and crystal ice as separate phases, and the mixture temperature and liquid pressure as primary field variables. Through two fundamental physical laws and corresponding state equations, the model captures the most relevant couplings between the phase transition associated with latent heat effect, and the liquid transport within the pores. The numerical model is validated by means of laboratory results considering different scenarios for seepage flow. As demonstrated in numerical simulations of ground freezing in tunneling in the presence of seepage flow connected with the ACO optimization algorithm, the optimized arrangement of the freeze pipes may lead to a substantial reduction of the freezing time and of energy costs. [ABSTRACT FROM AUTHOR]