Li-ming HU

Tsinghua University | TH · Department of Hydraulic Engineering

Two approaches of generating pore networks of porous media are presented to capture the pore fabric. The first methodology extracted pore structure from a computer simulated packing of spheres. The modified Delaunay tessellation was used to describe the porous media, and modified Nelder–Mead method in conjunction with three pore‐merging algorithms...

Air sparging (AS) is one of the most efficient techniques for remediating saturated soils and groundwater contaminated with volatile organic compounds. A series of physical modeling tests for different sizes of porous media under varied injection pressure were conducted to investigate the effect of particle size and air injection pressure on size a...

Electro-osmotic consolidation is a promising method to remove pore water from soft soils. Numerical models have been widely used to simulate the underlying flow-mechanical–electrical processes and predict the consolidation behavior of soft soils subjected to electro-osmotic treatment. In the present study, we proposed a method to convert a 3D elect...

The soil freezing characteristic curve (SFCC) represents the constitutive relationship between sub‐zero temperature and unfrozen water content in soil. It governs the hydrologic and mechanical behaviors associated with freezing soil. Numerous studies have investigated the mechanisms of soil water freezing and attempted to predict SFCC using soil wa...

Mathematical characterization of soil water isotherm (SWI) plays a significant role in modeling various processes in soils and estimating the soil properties, and the Brunauer-Emmet-Teller (BET) and Guggenheim-Anderson-de Boer (GAB) models are most widely used. Each model uses the amount of adsorbed gas in the monolayer on the surface for area esti...

Thermal desorption technology can effectively remediate fuels-contaminated clayey soil. However, the microscopic mechanism for the contaminant desorption on clay is still unclear, especially with the existence of water on clay surfaces. In this study, a combination method including TGA experiments, multi-phase and multi-component kinetic models, an...

Shale gas has become one of the important contributors to the global energy supply. The declining pattern of the gas production rate with time from an unconventional gas reservoir is due to the depletion of shale gas stored in the nanovoids of the shale formation. However, there are only limited ways to predict the variation of the gas production r...

The mobility of nano zero-valent iron (nZVI) will greatly affect its practical application as a remediation material for contaminated groundwater. One-dimensional (1D) column tests are commonly used in previous work to study its migration behavior, but the two-dimensional (2D) test is still very limited. This study reports a novel research system t...

Soil–water retention curve (SWRC) describes the relationship between soil matric potential and soil water content, which is recognized as the most important constitutive function for unsaturated soil that governs many hydrological and mechanical properties, such as fluid flow, hydraulic conductivity, chemical transport, and soil freezing and thawin...

Specific surface area is an important property of porous materials and mainly measured using nitrogen isotherm and Brunauer–Emmett-Teller (BET) equation. BET surface area is remarkably higher than geometric surface area, which is defined as the surface area of the crystal geometry structure. However, many studies directly use the BET surface area a...

Naphthalene, as one of the representative polycyclic aromatic hydrocarbons, widely exists in contaminated sites and is a potential threat to human health due to its high mobility in soil. The interaction between naphthalene and clay minerals is of great significance to the environmental behavior of naphthalene and the design of remediation technolo...

Electro-osmotic consolidation is an effective method to remove water from soft soils with high water content and low permeability. The previous analytical solutions and numerical simulations ignored the change of soil pH during the treatment. In the present study, a multi-field numerical model considering soil pH variation and non-linear soil param...

The sticking efficiency (α) is a vital parameter to predict the transport and deposition of colloids in porous media. The value of α depends on various factors such as the interaction energy between colloids and the solid-water interface (SWI), kinetic energy fluctuations of diffusing colloids, and the hydrodynamics of the flow field in the pore st...

During gas hydrate extraction multiphase flow occurs with transitioning gas hydrate phase followed by pore compression. Effective theoretical and numerical models with the ability to account gas hydrate are key to evaluate the feasibility of gas hydrate extraction and understand the physical mechanisms behind it. In this manuscript, a coupled multi...

Conventional colloid filtration theory (CFT) uses the single collector contact efficiency (η) to describe the mass transfer of colloids to a collector surface. However, this approach neglects the full complexity of the pore structure and flow field of real porous media. In this study, the porous medium geometry, flow field, and colloid mass transfe...

Hydraulic fracturing is widely applied for economical gas production from shale reservoirs. Still, the swelling of the clay micro/nano pores due to retained fluid from hydraulic fracturing causes a gradual reduction of gas production. Four different gas-bearing shale samples with different mineralogical characteristics were investigated to study th...

Colloid transport and retention in porous media is a common phenomenon in nature. However, retention mechanisms are not fully revealed based on macroscale experimental observations. The pore-network model (PNM) is an effective method to account for the pore structure of a porous medium and provides a direct connection between pore-scale retention m...

The nitrogen sorption isotherm is conventionally used to deduce the specific surface area of porous materials. However, it often exhibits a sharp drop around 0.5 relative pressure. A theory explicitly accounting for intermolecular-scale pressure, instead of classical theories of constant disjoining pressure in condensed liquid, is constructed and u...

The mechanical properties of shales, a type of heterogeneous and multiphase composite, are of multiscale characteristics in nature. A large number of indentation measurements were performed under the continuous stiffness measurement (CSM) mode on the Longmaxi shale, followed by data segmentation, Gaussian mixture modeling (GMM) deconvolution of seg...

The nano zero-valent iron (nZVI) has been seen as a promising material in the field of groundwater remediation. Researchers have studied the application of nZVI in in-situ remediation of groundwater. However, most of the existing studies focus on the transport of nZVI before reaching the polluted area. The transport behavior of contaminant-sorbed n...

Hydraulic fracturing is widely applied to economical gas production from shale reservoirs. Still, the gradual swelling of the clay micro/nanopores due to retained fluid from hydraulic fracturing causes a gradual reduction of gas production. Four different gas-bearing shale samples were investigated to quantify the expected shale swelling due to hyd...

The permeability of shale is a significant and important design parameter for shale gas extraction. The shale gas permeability is usually obtained based on Darcy flow using standard laboratory permeability tests done on core samples, that do not account for different transport mechanisms at high pressures and anisotropic effects in shales due to na...

Electro-osmotic consolidation combined with vacuum preloading is a potential technology to dewater the soft soils and slurry. The anode condition has a significant effect on dewatering efficiency during operation, which is not adequately addressed. In this study, laboratory tests were conducted to study the effect of different boundary conditions o...

Nano zero‐valent iron (nZVI) has been used for in situ groundwater remediation due to its strong adsorption and reaction characteristics. However, oxyanion contaminants in groundwater can ready adsorbed onto the surface of nZVI. This can potentially alter the mobility of nZVI and create a secondary pollution source, but these issues have not yet be...

Colloid transport and retention in porous media is a common phenomenon in both nature and industry. However, many questions remain on how to obtain colloid transport and retention parameters. Previous work usually assumed constant transport parameters in a medium under a given physicochemical condition. In this study, pore-network modeling is emplo...

The stability of tailings dams is important for the safety of residents living in the reservoir and downstream area, and is closely related to the consolidation of the dam during construction. In the present study, the consolidation behavior of fine tailings from Daxigou tailings dam in Shanxi Province, China was numerically analyzed through Geo-st...

Mechanical properties, such as the hardness H, Young’s modulus E, creep modulus C, and fracture toughness Kc, are essential parameters in the design of hydraulic fracturing systems for prospective shale gas formations. In this study, a practical methodology is presented for obtaining these properties through microindentation experiments combined wi...

Nano zero-valent iron (nZVI) has been considered as a promising material for groundwater remediation in the past few decades. The size distribution of nZVI is one of the main factors that influences its transport capability and remediation capacity. However, studies on the size distribution of nZVI under different environmental conditions are still...

Solid particle erosion has been a long-standing concern in oil-and-gas production and transportation systems, particularly in elbows of pipelines. Since it is difficult to exactly reproduce field conditions in the laboratory to study erosion, it is necessary to develop similarity criteria which ensure that lab results are representative of field co...

In oil and gas production and transportation systems, the particles carried with the conveying media usually exert accumulative collision on fittings such as elbows and tees in pipelines and piping section of facilities. The serious erosion damage may cause failure of the facilities and even lead to environmental disasters. In this study, the cushi...

One attractive aspect of CO2 sequestration in shale formations is the preferential adsorption of CO2 compared to methane, which may provide enhanced methane production as well as sequestration of carbon dioxide. In this work, a comprehensive theoretical model of CO2 migration at the pore scale is developed to study CO2 migration properties in organ...

With the recent tremendous advances of computer graphics rendering and image editing technologies, computer generated fake images, which in general do not reflect what happens in the reality, can now easily deceive the inspection of human visual system. In this work, we propose a convolutional neural network (CNN)-based model to distinguish compute...

The shortage of water resources has seriously restricted the development of cities. Unconventional water resources is of great significance for sustainable development. As a city lack of water, Los Angeles plans to develop reclaimed water as an important component of urban water supply under the conditions of drought and over exploitation of ground...

Water resources are important natural resources and play a key role in economic development and social life. China is one of the countries with the most serious water shortage in the world. In the next few decades, the contradiction between supply and demand of water resources will always plague China. Increasing the use of unconventional water res...

Aluminosilicate gels form geopolymers and nanocrystalline zeolites which have comparable strength properties, making them a potential replacement for ordinary Portland cement. The study explores the use of two untreated industrial wastes, Class-F fly ash and red mud, for synthesizing geopolymeric material at ambient synthesis conditions. The high a...

A numerical procedure is carried out to forecast the penetration rates of metal elbows caused by silica sand particles under air-water annular flow conditions. The procedure aims at overcoming the disadvantage of the existing numerical methods, which oversimplified the thickness distribution of the liquid film flowing through the elbows. The numeri...

Micro-nano-bubbles (MNBs), in particular ozone and oxygen MNBs, represent an innovative method for wastewater treatment and groundwater remediation. Although several models have been developed to describe the fate of MNBs in water, a theoretical model describing the mass transfer processes of MNBs during treatment of contaminants has not been adequ...

Laboratory tests were conducted on kaolinite to investigate the effectiveness of electro-osmotic consolidation combined with vacuum preloading using electrokinetic geosynthetics (EKG). The results showed that the combined method could remove more water and induce larger surface ground settlements compared with the traditional vacuum preloading or e...

Electrical Resistivity Tomography (ERT) method has been recognised as a robust technique with unique features for achieving three-dimensional noninvasive measurements and enabling multi-scale characterisation of a range of soil or fluid properties linked to electrical resistivity. This paper introduces a research programme established to develop a...

For the adsorption between the solid and liquid phases, the solid liquid ratio s/l and initial adsorbate concentration \( C_{0} \) are usually considered as the significant influence factors. The solid solute ratio s/a, i.e., the adsorbent dosage to adsorbate concentration ratio or the ratio of s/l to \( C_{0} \), has been proposed to be a new infl...

Micro-nano-bubbles (MNBs) technique is a novel technology for remediation of organics-contaminated groundwater. MNBs are tiny bubbles with diameter less than 100 µm, and able to stay stable in water for extended periods of time. Ozone is a strong oxidant which is widely used in wastewater treatment, and ozone MNBs presented high mass transfer effic...

Nanoscale zero valent iron (nZVI) has shown great potential in the remediation of contaminated groundwater. For many different types of contaminant, adsorption was the main remediation mechanism, so it is necessary to figure out the adsorption models of remediation by nZVI. In this study, copper ion, phosphate anion and methyl orange were used resp...

The exploitation of mineral resources produces large amount of mine tailings. Usually these tailings are pumped into a sedimentation pond in a slurry state to be stored. However, the process of tailings slurry transformation from the muddy fluid state to the natural sedimentary soil has not been understood adequately. This paper studies the mechani...

Geopolymers are inorganic aluminosilicate polymers which have been synthesized from pure sources and more recently, from industrial byproducts. In this study, the industrial by-products, coal gangue, fly ash and red mud were used to synthesize geopolymers at low and elevated temperatures. NaOH, which is often used to raise the pH of the mixture, ha...

The efficiency of ozone for the treatment of organics contaminated wastewater is limited by its slow dissolution rate and rapid decomposition in the aqueous phase. Micro-nano-bubbles (MNBs) are a novel method to prolong the reactivity of the ozone in the aqueous phase, thereby accelerating the treatment of the contaminant. In this study, the effect...

Arsenic (As) released from As-loaded nano zero-valent iron (nZVI) after As(V) remediation could become an environmental hazard, thus deserving in-depth investigation. This study investigated the As release from As-loaded nZVI under different geochemical conditions (i.e. pH, Ca2+ and humic acid concentrations), as well as the effects of nZVI surface...

In this study, the effects of surface modification of nZVI and arsenic (As) loading on the mobility of the three types of As-loaded nZVI (As-loaded pristine, chitosan-modified and polyaniline-modified nZVI) in quartz sand-packed columns were investigated. Breakthrough curves and retention profiles for the three types of As-loaded nZVI were analyzed...

Spurred by the advanced technologies, mainly including horizontal drilling and hydraulic fracturing, shale gas exploration has grown significantly over the past few decades. Upon exposure to the aqueous fracturing fluids in the high temperature and high pressure subsurface, the mechanical properties of shales such as elasticity, hardness, and stren...

The application of an electric field on soil mass induces both electro-osmotic flow and electro-migration, which has been used for the dewatering of soft soils and remediation of contaminated soils. The physical and chemical properties of soft soils are influenced by the soil pH as well as ionic species and their concentrations, which subsequently...

Pore-network model is a convenient tool to investigate the micromechanics of seepage in porous media. Geo-materials are typical porous media, including the different types of soils and rocks from rock-fill with mm-scale pores with high connectivity to gas shale with nm-scale pores and little connectivity. Based on the 2D image from CT or micro-CT t...

The use of nano zerovalent iron (nZVI) for arsenate (As(V)) remediation has proven effective, but full-scale injection of nZVI into the subsurface has aroused serious concerns for associated environmental risks. This study evaluated the efficacy of nZVI treatment for arsenate remediation and its potential hazards to plants using Arabidopsis thalian...

Electrokinetic geosynthetics (EKG) has been used as an electrode to perform electroosmotic consolidation for the improvement of soft soil. To use previous analytical theories to analyze the drainage and consolidation behavior of soil mass, the band-shaped EKG electrodes need to be converted to cylindrical electrodes; however, no definitive principl...

For shale gas exploitation, it is scientifically essential to clarify the mechanism of gas flow in nanopore media. Shale is a kind of tight rock, whose pore size mainly ranges from several nanometers to dozens of nanometers. Since it is of the same magnitude as the gas molecular mean free path, the collision between the gas molecular and pore surfa...

Adsorbent dosage and initial adsorbate concentration are usually used as two factors for a batch sorption experiment to investigate the sorption characteristics of heavy metals on soils. In the present study, another factor was defined as the ratio between initial adsorbate concentration and adsorbent dosage, and its relation with the sorption char...

Ozone is widely used for water treatment because of its strong oxidation ability. However, the efficiency of ozone in groundwater remediation is limited because of its relatively low solubility and rapid decomposition in the aqueous phase. Methods for increasing the stability of ozone within the subsurface are drawing increasing attention. Micro-na...

Rheological characteristics are fundamental to pipeline system design. Rheological tests were conducted to obtain the yield stress and viscosity index at different mass fractions. Slump tests were conducted to investigate the mobility of tailings slurry. Results show that the yield stress increases with the increase of mass fraction, especially whe...

Electro-osmotic consolidation is an effective method for soft ground improvement. A main limitation of previous numerical models on this technique is the ignorance of the non-linear variation of soil parameters. In the present study, a multi-field numerical model is developed with the consideration of the non-linear variation of soil parameters dur...

Extremely low permeability due to nano-scale pores is a distinctive feature of gas transport in a shale matrix. The permeability of shale depends on pore pressure, porosity, pore throat size and gas type. The pore network model is a practical way to explain the macro flow behavior of porous media from a microscopic point of view. In this research,...

Coal gangue is one of the largest industrial solid waste all over the world, and many methods have been proposed for the recycling of coal gangue. In the present study, the feasibility of using coal gangue as landfill liner material is studied through a series of laboratory tests in terms of hydraulic conductivity, sorption characteristics and leac...

In present study, the non-linear variations of soil compressibility, hydraulic and electro-osmosis conductivities were analyzed through laboratory experiments, and incorporated in a one-dimensional model. The analytical solutions for excess pore water pressure and degree of consolidation were derived, and numerical simulations were performed to ver...

Electroosmotic consolidation can be used as an efficient technique for soft soil improvement. Considering the limitation in previous theories that soil parameters keep constant during electroosmotic consolidation, the nonlinear relationships between soil compressibility, hydraulic and electroosmosis conductivities, and void ratio are incorporated i...

The engineering properties of tailings are important for the safety evaluation and engineering design of tailing dams. In the present study, laboratory experiments were performed to investigate the geotechnical properties of four different tailings, including two iron tailings (coarse and fine) and two copper tailings (coarse and fine). Compared to...

Electro-osmotic consolidation is an effective technique for soft soil improvement. In this study, a multi-field coupling numerical model for electro-osmotic consolidation was proposed to simulate the dewatering and consolidation process of soft soils. Seepage, electrical, and stress and strain fields were considered and the boundary conditions coul...

Over 300 million tons of municipal solid waste (MSW) has been produced in China every year. So far landfilling has been the major form of disposal for the MSW and hazardous industrial solid wastes. Horizontal liner becomes the key barrier structure preventing contamination, which consumes large amount of clays and cause land and environmental probl...

A discrete element method (DEM) numerical simulation is used as a tool to study the mechanical behavior of soil-rock mixtures (S-RM) in a landslide dam. A 2D random generation program (R-SRM2D) of the meso-structure of (S-RM) based on random polygonal rock blocks has been developed, and is used to generate the (S-RM) numerical model of the study ar...

A discrete element method (DEM) numerical simulation is used as a tool to study the mechanical behavior of soil-rock mixtures (S-RM) in a landslide dam. A 2D random generation program (R-SRM2D) of the meso-structure of (S-RM) based on random polygonal rock blocks has been developed, and is used to generate the (S-RM) numerical model of the study ar...

At present, high-density electrical resistivity tomography(HERT) has been widely used in environmental geotechnical engineering, especially seepage and solute transport. High-density electrical resistivity tomography provides a new method to satisfy the necessities of three-dimensional, non-destructive, and real-time measurement. In order to carry...

In geotechnical model tests, the methods conventionally employed in measuring water content and solute transport include sensor techniques, image processing techniques and direct soil sampling methods. However, these techniques cannot fully satisfy the necessities of three-dimensional, non-destructive and real-time measurement, especially in geotec...

Electro-osmosis is a process coupling electrolyte flow and associated hydraulic flow under an external electrical field, resulting in the permeation of both electrolyte and pore fluid in porous media. One-dimensional column experiments were conducted to comprehend the effects of electro-osmosis treatment on the physical and chemical properties of a...

Electrode material has significant influence on the behavior of soil during electro-osmotic consolidation. Four electro-osmotic consolidation experiments on a sodium bentonite were conducted with copper, iron, graphite and stainless steel electrodes. The result indicated that the copper electrodes achieved the best drainage performance. The change...

Nowadays groundwater contamination widely spreads in China. Organic pollutants are of the public concern since they are toxic and with long cycle, causing considerable remediation cost. The innovative remediation technologies are urgently needed. In this paper, the micro-nano bubbles (MNBs) technology with the ozone oxidation method was proposed, a...

Tailings are one of the primary solid wastes of mining industry. They are made of fine-grained particles of the parent rock from which the ore is extracted by crushing, grinding, and other milling processes. Furthermore, volumetrically, tailings impoundments are among the largest structures created by human kind. The safety of the tailing reservoir...

Electro-osmotic consolidation is considered to be an efficient technique for dewatering and consolidation of soft soil. In the present study, four experiments were conducted on a Na-rich bentonite using two reactive electrodes (copper and iron) and two inert electrodes (graphite and stainless steel) to study the transport and exchange behavior of i...

Electro-osmosis has been used as an effective technique for soft ground improvement. An axisymmetric testing apparatus was developed to study the dewatering and consolidation behaviour of kaolinite samples with different initial water content during electroosmosis under intermittent current. An axisymmetric numerical model with non-linear variation...

The gas transport in shale matrix is of great research interest for optimised shale gas recovery. Pores and pore-throats in the gas-bearing shale are nano-scale, and hence transport of gas is governed by the slippage effect and Knudsen diffusion rather than viscous flow. Hence a proper mathematical model is needed for full understanding of shale ga...

The gas flow in shale matrix is of great research interests for optimized shale gas extraction. The gas flow in the nano-scale pore may fall in flow regimes such as viscous flow, slip flow and Knudsen diffusion. A 3-dimensional nano-scale pore network model was developed to simulate dynamic gas flow, and to describe the transient properties of flow...

The gas flow in shale matrix is of great research interests for optimized shale gas extraction. The gas flow in the nano-scale pore may fall in flow regimes such as viscous flow, slip flow and Knudsen diffusion. A 3-dimensional nano-scale pore network model was developed to simulate dynamic gas flow, and to describe the transient properties of flow...

In order to investigate the shear yield characteristics of structured granite residual soil, a series of conventional triaxial drained tests are conducted on the undisturbed granite residual soil, remolded soil and cemented residual soil. From the test results, some insights can be obtained as follows. For undisturbed granite residual soil and ceme...