Shijin Feng

Tongji University · Department of Geotechnical Engineering

Vertical cutoff walls have been widely employed for groundwater control and in situ containment of subsurface pollutants. The traditional cutoff wall materials are usually highly susceptible to dry–wet cycles due to precipitation, drought, and groundwater fluctuation, leading to cracking or even disintegration. This study adopted sodium bentonite (...

Aiming to automatically, precisely, and rapidly detect tunnel lining cracks from images and extract geometric information for structural condition assessment, this study proposes a novel tunnel lining crack segmentation network (TCSegNet) and establishes a framework for calculating key geometric parameters of cracks. A tunnel lining crack segmentat...

Contaminant back diffusion from low-permeability aquitards can result in long-term plumes in adjacent aquifer systems, severely impeding groundwater clean-up. Hydraulic fracturing extraction is a promising aquitard remediation technology to mitigate back diffusion. However, the synergistic decontamination mechanisms of hydraulic fracturing and mult...

In-situ chemical oxidation (ISCO) has been widely utilized for the remediation of organic contaminated soil, while the long-term remediation efficiency and mechanism have been rarely explored, which is of great importance to the field implementation due to the potential for secondary pollution in later stages after remediation. The geotechnical cen...

In situ chemical oxidation (ISCO) technology has limitations in the remediation of low-permeability polycyclic aromatic hydrocarbon (PAHs)-contaminated sites because of the difficulty in oxidant delivery. Horizontal fractures created by hydraulic fracturing provide convenient channels for rapid oxidant delivery. However, limited studies have focuse...

Thermal-enhanced soil vapor extraction (T-SVE) is an in-situ remedial technique that can address the limitations of contaminant mass transfer and soil permeability. The relative humidity of the injected air, heating temperature of the thermal well, extraction pressure, and extraction mode are important design parameters of a T-SVE system that deter...

Vertical cutoff wall has been employed for decades to control groundwater flow and subsurface contaminant transport. Environmental stress fluctuations induced by alternating dry and wet conditions impair the permeability and durability of the cutoff wall, leading to the dispersion of contaminants. The objective of this study is to incorporate self-...

Energy piles are inevitably subjected to thermomechanical loads due to their dual role of utilizing geothermal energy and supporting structural loads. The load-transfer approach is a suitable predictive method for addressing the analysis and design of energy piles, but it generally does not properly consider the continuity and deformation behavior...

In some countries lacking sodium bentonite (NaB), polymer-modified calcium bentonite (CaB) has attracted attention for its application in sand-bentonite slurry trench cutoff walls to control groundwater contamination. Thus, this study used polyanionic cellulose (PAC), an environmentally friendly hydrophilic polymer, to modify CaB. The hydraulic and...

The PHC (pre-stressed high-strength concrete) pile foundation, serving as an innovative supporting structure for solar power stations, is subjected to complex loading conditions in engineering scenarios. In this study, field tests of the full-scale PHC Pile foundation were conducted in sand layer, loess layer, and double-layer sites to investigate...

Comprehending the transport mechanism of bimolecular reactive solutes in fracture-matrix systems is crucial for improving the efficiency of collaborative remediation using hydraulic fracturing and in-situ chemical oxidation in low-permeability contaminated sites. Previous studies have neglected the effects of physical nonequilibrium (PNE) caused by...

The performance of a geogrid-stabilized structure affected by dynamic loadings is significant. This study investigates the microscale deformation mechanism of the geogrid–aggregate interface cyclic shear behavior using the discrete element method (DEM). Spheres and nonspherical clumps are generated to form aggregate samples. The DEM models are able...

Energy piles are increasingly being exploited worldwide for their dual functions of bearing structural loads and utilizing geothermal energy. However, scarce knowledge is available on the time-dependent thermomechanical behavior of energy pile groups constructed in soft soils. In this paper, an analytical approach was proposed for the thermomechani...

The coupling processes in unsaturated regions of anaerobic and aerobic landfills have been widely studied and modelled. However, the previous studies cannot address two new problems in practice: a large quantity of landfill gas (LFG) generated and accumulated below leachate level, and the quantitative prediction of the stabilization of three-phase...

The bimodal characteristic of water retention curves of dual-porosity soils has been fully recognized, however, the excessive number of fitted parameters in the existing models limits their application. This study develops a simple water retention model for dual-porosity soils that considers the self-similar characteristics of the pore size distrib...

Sand-bentonite slurry trench cutoff wall is one of the most common vertical barriers to retard the migration of contaminants. This study aimed to explore the hydraulic and consolidation performance of cutoff-wall materials containing polyanionic cellulose (PAC)-modified calcium bentonite (CaB) through a comprehensive laboratory investigation. First...

Aeration is an effective approach to sustainable landfilling but may lead to elevated temperatures within landfills, resulting in landfill fires or explosions. Therefore, aeration is usually combined with leachate recirculation to control the elevated temperatures within landfills. To predict landfill temperatures during aeration and recirculation,...

Traditional remediation technologies cannot well remediate the low permeability contaminated stratums due to the limitation in the transport capacity of solute. The technology that integrates the fracturing and/or slow-released oxidants can be a new alternative, and its remediation efficiency remains unknown. In this study, an explicit dissolution-...

Thermal enhanced soil vapour extraction (T-SVE) is a remedial technique involving gas, aqueous, solid and nonaqueous phases along with mass and heat transfer. Interphase mass transfer of contaminants and water evaporation/condensation will cause the redistribution of phase saturation, eventually affecting the performance of T-SVE. In this study, a...

Low-permeability aquitards may serve as secondary sources of slow-releasing contaminants into the adjacent aquifer system, creating considerable obstacles to groundwater cleanup. Accurately capturing the exchange of contaminant mass between aquitards and aquifers can facilitate site management and remediation. Previous simulation studies were mainl...

The physical-based hydraulic constitutive model developed by fractal theory has received much attention, however, its performance in two-phase flows has not been fully evaluated. This study evaluates the ability of fractal-based hydraulic constitutive models to describe the two-phase flow combining mass and momentum conservation equations. After th...

The reinforcement mechanism of geogrids has not been fully revealed. Using the discrete element method (DEM), this study conducts a series of numerical direct shear tests on the interface between the geogrid and the non-spherical aggregate for optimization strategies of the aperture ratios considering the initial interlocking states. The micromecha...

This paper presents a new analytical model for forecasting one-dimensional transient transport of organic pollutant in a typical landfill composite liner including a geomembrane (GMB), a geosynthetic clay liner (GCL) and a soil liner (SL). The model can consider the coupling effect of molecular diffusion, thermodiffusion, advection and linear adsor...

This study develops a generalized constitutive model to describe hydraulic properties of soils that consider the soil heterogeneity and water distribution. In this model, pore size distribution in a cross-section of representative element volume is assumed as a fractal characteristic. The heterogeneity of soils is described by two heterogeneous fac...

Rational utilization of soil resources and remediation of contaminated soils are imperative due to the rapidly growing demand for clean soils. Currently, many in-situ remediation technologies are less suitable at low-permeability sites due to the limitations of soil permeability. This work defines a low-permeability site as a site with hydraulic co...

Seismic stability is of vital importance for municipal solid waste (MSW) landfills and this study proposes an advanced numerical approach considering material and contact nonlinearity for seismic analysis of landfill. The MSW is modeled as porous media through the u-p formulation and the bounding surface plasticity model based on the double-phase a...

Soil-bentonite slurry trench cutoff walls have been extensively used as engineered barriers for contaminant containment. In some regions without appropriate sodium bentonite (NaB), local calcium bentonite (CaB) that is cheap and abundantly available may be considered as an alternative material. However, CaB has a poor swelling capacity and it is im...

Flowslide disasters of municipal solid waste (MSW) landfills generally have a long flow distance. In the condition of extremely large deformation, the strength of MSW cannot be reinforced by embedded fibers (also called hardening) with fiber pullout. To describe this softening behavior of MSW in a state of large strain, this study proposes a double...

Geotextile-geomembrane interface has low shear strength and strain-softening characteristics which might induce progressive failure in landfills. The interlocking between asperities and filaments and wearing of them have significant influence on the interface shear behaviors between textured geomembrane (GMB) and thermally bonded nonwoven geotextil...

Gas diffusivity is a crucial parameter for modeling the mass flow and transport in the fields of engineering, agriculture and environment. However, existing models were only developed for single-porosity media and underestimated the diffusivity of gas in fractured or cracked media. This study develops a fractal diffusion model of gas in unsaturated...

This paper presents an experimental investigation of the shear behavior of the interface between a high-density polyethylene geomembrane and a needle-punched nonwoven geotextile (GT) under monotonic loading conditions. Direct shear tests were conducted using a self-designed experimental apparatus. The effects of interface types (textured geomembran...

Contaminants stored in the low permeability sediments will continue to threaten the adjacent shallow groundwater system after the aquifer is remediated. Understanding the storage and discharge behavior of contaminants in the aquitards is essential for the efficient remediation of contaminated sites, but most of the previous analytical studies focus...

The gas diffusivity of porous media under dry and wet conditions is valuable in many science and engineering fields, but its accurate measurement remains challenging and time-consuming. This study develops a fractal theoretical model to predict the diffusion behavior of gas in heterogeneous porous media over the entire saturation range. In this mod...

Aeration, which creates an aerobic environment by air injection, has been proven to be an effective method to accelerate waste stabilization and reduce pollution load in landfills. To reveal the multi-field coupling interactions in an aerobic landfill, this study developed a three-dimensional multifield coupled model involving anaerobic–aerobic bio...

Aquitards contaminated by chlorinated solvents may act as a secondary source slowly releasing contaminants into adjacent aquifers, thus severely hampering the remediation of groundwater systems. Accurate predicting the long-term exchange of solvents between aquifers and aquitards can more effectively guide site management and remediation. This stud...

A clear understanding of long-term bio-hydro-thermo-mechanical (BHTM) behaviors of landfilled Municipal Solid Waste (MSW) is essential to better design and manage landfills, which requires the development of both analytical and numerical models that can represent typical behaviors of MSW. In this study, a novel multi-phase, multi-component numerica...

Volatile organic compounds (VOCs) contamination may occur in subsurface soil due to various reasons and pose great threat to people. Petroleum hydrocarbon compound (PHC) is a typical kind of VOC, which can readily biodegrade in an aerobic environment. The biodegradation of vapor-phase PHC in the vadose zone consumes oxygen in the soil, which leads...

A solar power tower plant includes a solar tower and tens of thousands of heliostats, where the latter accounts for 40–50% of the total cost. To reduce heliostat costs, a new type of heliostat support structure that consists of a pre-stressed high-strength concrete (PHC) pipe pile and cast-in-place concrete is proposed. However, the performance and...

A geosynthetic liner system that consists of geomembrane (GMB) and geosynthetic clay liner (GCL) is vital for landfill stability analysis and it is essential to investigate the shear characteristics of GMB/GCL interface. This paper introduces a new direct shear apparatus for various geosynthetic interfaces with innovative designing, and using this...

The sources of pollution, in general, are divided into nonpoint sources and point sources. Cutoff wall as a low-permeability vertical barrier has been widely employed for control and containment of these two types of pollution sources. Previous cutoff wall models mainly were limited to the nonpoint source pollution with constant concentrations. Hen...

Geosynthetic interfaces within composite liner systems usually play an important role in failure events of landfills and should be well considered in stability assessment. A constitutive model based on the disturbed state concept is proposed to describe the shear behavior of geosynthetic interfaces under both static and dynamic conditions. The inte...

Fracturing technology that can enhance the delivery of amendments has attracted attention in the remediation of low-permeability contaminated sites. However, there are few works on the enhanced delivery of amendments based on multi-point injection in a fracture-matrix system. This study develops a two-dimensional analytical model for enhanced deliv...

During the operation of landfills, leachate recirculation and aeration are widely applied to accelerate the waste stabilization process. However, these strategies may induce high pore pressures in waste, thereby affecting the stability of the landfill slope. Therefore, a three-dimensional numerical analysis for landfill slope stability during leach...

Although migration of subsurface volatile organic compounds (VOCs) from contaminant sources in unsaturated soil widely exists, the related analytical models are quite limited. A two-dimensional analytical solution is hence developed to simulate vapor diffusion from the subsurface contaminant source in the layered unsaturated zone. The contaminant s...

In a bioreactor landfill, waste biodegradation, generation of gas and leachate, two-phase flow and mechanical deformation closely couple with each other. Recirculated leachate can accelerate waste biodegradation and generation of landfill gas. A significant mechanical deformation occurs due to biodegradation and suction change, and the increase in...

This study provides an analytical solution for forecasting one-dimensional molecular diffusion of organic pollutants in triple-layer composite liner system considering the coupling effect of thermal diffusion. The solution is appropriate for two typical bottom boundaries, i.e., Dirichlet and Neumann boundaries. The solution is verified against expe...

Predicting the migration behavior of volatile organic compounds (VOCs) vapor is essential for the remediation of subsurface contamination such as soil vapor extraction. Previous analytical prediction models of VOCs migration are mostly limited to constant-concentration nonpoint sources in homogeneous soil. Thus, this study presents a novel analytic...

A sanitary landfill with significant sliding indications was studied through field investigations and numerical analyses. A translational deformation mode was discovered, and the leachate level of the landfill reached approximately 0.8 times the height of the waste body, which was extremely adverse for stability. Subsequent analyses revealed that t...

A one-dimensional analytical model is proposed to analyze contaminant diffusion through a composite geomembrane cut-off wall (CGCW) composed of a geomembrane (GMB) and a bentonite cut-off wall (BCW). The model considers degradation process of contaminant and time-dependent inlet boundary condition which are common in engineering practices. Moreover...

Predicting the fate and transport of contaminants in a subsurface environment is essential to the evaluation and remediation of soil and groundwater pollution. Point source models have been widely used to describe the accidental leakage of contaminants and the intended injection of chemicals, but previous researches are limited to a single source i...

Performance evaluation of the embankment subject to climate change and dynamic train loads is important to the safety of high speed railway (HSR). In this study, based on an elasto-plastic unsaturated soil model, a coupled hydraulic-mechanical-air finite element analysis method is proposed, which integrates the analysis under rainfall condition and...

To overcome the weaknesses of traditional landfills, a modified aerobic landfill concept with intermediate covers of coarse material between waste layers functioning as facilities of drainage and aeration has been proposed recently. In this study, a one-dimensional coupled model, including aerobic biodegradation, oxygen diffusion, and advection, is...

Cutoff walls are widely used as in-situ vertical barriers to control pollution plumes migration in aquifer. A two-dimensional analytical model for the transport of organic contaminants through a layered subsurface system with a cutoff wall is developed. The model considers a coupled advection-dispersion-adsorption-degradation process in the whole s...

This paper investigates the dynamic response of an axially loaded Timoshenko beam coupled with a multilayered transversely isotropic (TI) half‐space subjected to a moving load. An axial force induced by the thermal expansion is taken into account in the Timoshenko beam. The half‐space considers the alternate distribution of an arbitrary number of T...

The composite liner system consisting of geomembrane (GMB) and geosynthetic clay liner (GCL) has been widely used in landfills. Although there have been a lot of studies on the monotonic shear behavior of GMB/GCL composite liner, the dynamic test data are still very limited and consequently, the dynamic shear mechanism is not clear. A series of dis...

The dynamic shear behavior of composite liner interface is of great importance for landfill seismic analysis. In this study, an experimental investigation of the shear behavior of the interface between smooth high density polyethylene (HDPE) geomembrane (GMB) and compacted clay liner (CCL) is presented. A series of displacement-controlled cyclic sh...

Textured geomembrane (GMB) and nonwoven geotextile (GTX) are usually used together in liner systems of MSW landfills, but the low shear strength of GMB/GTX interface is extremely detrimental to the stability of landfills, especially under earthquake loading. To study the dynamic shear strength of the GMB/GTX interface, a series of displacement-cont...

A new analytical model for organic contaminant transport through GMB/CCL (geomembrane and compacted clay liner) composite liner is developed, which can consider adsorption, diffusion and thermodiffusion processes and is applicable for typical bottom boundary conditions. The separation of variables method is adopted to derive the solution. The prese...

The internal shear strength of a geosynthetic clay liner (GCL) within composite liner systems is crucial for the stability of landfills and should be carefully considered in the design. To explore the shear strength and failure mechanism of the extensively used needle-punched GCL, a series of displacement-controlled direct shear tests with five nor...

Landfilling is the primary method used for municipal solid waste (MSW) disposal. To design, optimize, and manage landfills with a life span of several decades, a deeper understanding of long-term MSW behaviors is necessary and worthwhile. These behaviors should be modeled using approaches that account for coupled processes so as to capture the evol...

Horizontal spacing of horizontal extraction gas wells can be designed to achieve a 90% pumping rate of the total generated landfill gas (LFG) from given waste properties (viz: gas permeability, landfill gas generation and non-homogeneity with depth), cover characteristics and vacuum pressure. However, cover characteristics and vacuum pressure are a...

The vertical, rocking and horizontal vibrations of a rigid disk on multi-layered soils are studied by using a coupled approach of stiffness matrix method and “integral equation method”. Considering groundwater level, the layered soils consist of a number of dry layers and saturated layers, and a bedrock at the bottom. To allow the assembly of a glo...