Tunneling Behavior Research Articles

Can high speed railway curb tunneling? Evidence from the independent directors' monitoring effect in China

This study examines the effect of opening a high-speed railway on the tunneling behavior of controlling shareholders. It uses the direct connection between listed companies and independent directors facilitated by the advent of high-speed railways and finds that the opening of high-speed railways can facilitate independent director monitoring and curb controlling owners' tunneling. A cross-sectional analysis shows that this curbing effect is more pronounced for companies with long geographic distances between companies and their independent directors, for independent directors with financial expertise, and for independent directors who live far from companies. The findings also show that the curbing effect is more pronounced for companies that are facing environments with poor legal protection and imply that independent director monitoring and legal protection can be substitutive. These findings support the hypothesis that the opening of high-speed railways can facilitate independent director monitoring and curb controlling owners' tunneling, implying that transportation infrastructure development not only affects social welfare at the macro level but also has a governance effect at the micro level.

Damage mechanism modelling of shield tunnel with longitudinal differential deformation based on elastoplastic damage model

Shield tunnels with great longitudinal differential deformations will adversely affect the service performance and optional safety of the metro system. Previous studies on the longitudinal mechanical behavior of shield tunnel are mostly carried out within the framework of elastic or elastic–plastic theory. However, assuming the concrete as elastoplastic body cannot properly reflect its nonlinear mechanical characteristics such as strain softening, stiffness degradation, etc., while damage or crack inevitably occurs when shield tunnel suffers large deformations. Therefore, the nonlinear damage characteristics of concrete material are considered in this paper, a novel positive/negative decomposition of stress tensor in energy norm is introduced herein to consider the asymmetric tensile/compressive material behavior of concrete, and a bi–scalar damage constitutive model of concrete is developed in turn. Then, to investigate the damage and degradation mechanisms of shield tunnel with differential deformation, the 3D discontinuous contact model is employed to develop the elaborate tunnel–soil numerical model. Results show that when shield tunnel suffers differential deformation, tensile damage dominates while compressive damage is minor, additional shear force and bending moment are induced, the ovality of tunnel cross section and serviceability also vary along the longitudinal direction. The damage and degradation of concrete material will reduce the tunnel integral stiffness and attenuate its ability to resist longitudinal and circumferential deformation. Besides, the segmental rebar is hard to yield, while the longitudinal coupling bolts on the lower half of tunnel segments with large deformation are inclined to yield. It should be noted that, the segmental rings near the inflection point of longitudinal deformation profile are most severely damaged, and exhibit the largest convergence deformation and lowest serviceability, where special attentions should be paid.

Numerical research on airflow-dust migration behavior and optimal forced air duct installation position in a subway tunnel during drilling operation

In order to efficiently control the severe dust pollution ahead of the driving face during drilling operation, this study combined the numerical simulation with field measurements to analyze the effect of installation position of the forced air duct on the airflow-dust migration behavior in a subway tunnel. Nine schemes of installation position of the forced air duct were chosen to in-depth investigate the dynamic variation of dust concentration in four personnel breathing zones, then the optimal installation position of the forced air duct with regard to the efficient dust suppression performance was determined. The numerical simulation results showed that from the perspective of the static excavation process, the optimal dust suppression performance was achieved when the forced air duct was installed in the bottom arch of 30 m from the driving face, and the average dust concentration in four personnel breathing zones was 31.78 mg/m3. While, from the perspective of 10 m dynamic excavation process, the optimal dust suppression performance was achieved when the forced air duct was installed in the bottom arch of 20 m from the driving face, and the average dust concentration in four personnel breathing zones was 33.21 mg/m3. Finally, the accuracy of the numerical simulation results was validated by field measurement.

Behavior of tunnels excavated with dip and against dip

Rock masses with remarked rock structure are likely to be highly anisotropic; thus, the relative orientation of the tunnel with respect to the rock structure will affect the tunnel behavior. Displacements measured at the walls of tunnels in highly anisotropic rock masses often reveal an asymmetric deformation pattern around the tunnel perimeter, which is often interpreted as the result of rock heterogeneity or changing geology. However, numerical and analytical investigation of tunnels in anisotropic rock masses show that the tunnel axis misalignment with the principal directions of stress and material anisotropy induce anti-symmetric axial displacements (i.e., axial distortion of the tunnel cross section) far behind the tunnel face. Near the face, the axial distortion is partially constrained, causing asymmetric radial displacements. In this study, tunnels excavated with and against dip of the major rock mass discontinuity are explored using 3D FEM modeling. A detailed analysis on the mechanisms associated with the direction of excavation is provided. It is shown that the asymmetric displacements near the face may strongly affect the displacements measured at the tunnel walls, which may explain the asymmetric displacements commonly observed on tunnels in anisotropic rock.

Tunnel Behaviour Caused by Basement Excavation in Clay

Many researchers have investigated the effect of basement excavation on tunnel deformation. However, the influence of consolidation on the interaction of basement-tunnel-soil is rarely considered or systematically studied in clay. In this study, three-dimensional coupled-consolidation finite element analyses were conducted to investigate the effect of consolidation on the tunnel response to excavation. An advanced nonlinear constitutive model was adopted, and numerical parametric investigations were conducted to study the effect of the excavation depth, tunnel stiffness, soil permeability coefficient, and consolidation time on the tunnel response. The results revealed that the basement excavation led to stress release, which caused tunnel heave. Owing to the dissipation of excess negative pore water pressure, the tunnel heave further increased to become approximately twice as large compared with that observed when the foundation pit excavation had just been completed. As the consolidation time increased, the longitudinal tunnel heave and tunnel diameter change caused by the foundation pit excavation gradually increased, but the growth rate was slower down. When the consolidation time changed from 50 days to 150 days, the maximum tunnel heave at the crown and the maximum tunnel diameter change increased by 1.18 and 1.48 times, respectively. The soil’s permeability coefficient did not have a significant effect on the tunnel heave at the crown nor on the tunnel diameter change. The results obtained by this study are expected to be useful as an engineering reference for the analysis of soil structure problems in clay.

Material and Device Structure Designs for 2D Memory Devices Based on the Floating Gate Voltage Trajectory.

Two-dimensional heterostructures have been extensively investigated as next-generation nonvolatile memory (NVM) devices. In the past decade, drastic performance improvements and further advanced functionalities have been demonstrated. However, this progress is not sufficiently supported by the understanding of their operations, obscuring the material and device structure design policy. Here, detailed operation mechanisms are elucidated by exploiting the floating gate (FG) voltage measurements. Systematic comparisons of MoTe2, WSe2, and MoS2 channel devices revealed that the tunneling behavior between the channel and FG is controlled by three kinds of current-limiting paths, i.e., tunneling barrier, 2D/metal contact, and p-n junction in the channel. Furthermore, the control experiment indicated that the access region in the device structure is required to achieve 2D channel/FG tunneling by preventing electrode/FG tunneling. The present understanding suggests that the ambipolar 2D-based FG-type NVM device with the access region is suitable for further realizing potentially high electrical reliability.

Short and Long-term Behaviours of Bored Tunnels in Port-Said Clay

This study investigates the behaviour of bored tunnels in the Port-Said very soft to firm clay deposit in El-Tina Plain, north-eastern Egypt. Recent studies provided full characterization of the physical, mechanical and time-dependent properties of Port-Said Clay. This characterization enabled simulating its constitutive behaviour using the stress-dependent Modified Cam Clay model. The finite difference method is utilized to simulate the interaction between the tunnel and Port-Said Clay. The results are presented in terms of the pore water pressure regime, shear strain level, ground surface settlement and tunnel lining bending moment. The results show significant effect of the face and grouting pressures on the tunnel’s short and long-term behaviours. The term “reference hydrostatic pressure” is introduced to evaluate short-term face stability as a more practical and easy-to-quantify parameter compared to the conventional stability number. New empirical equations are developed to describe the long-term surface settlement trough (maximum settlement and trough width) in terms of the grouting pressure and tunnel diameter for tunnels in similar soft clay deposits.

Numerical study of water inflow into tunnels in stratified rock masses with a dual permeability model

Stratification planes form an anisotropic structural setting in the stratified rock mass, and strongly influence the water inflow into tunnels. However in the numerical simulation studies, the equivalent porous model pays little regard for the anisotropic structural setting and the discrete fracture network model costs too much computing power. In this study, a dual permeability model is utilized to calculate the water inflow into tunnels and the anisotropic flow behavior with finite element numerical simulations. The dual permeability model takes the stratification planes into artery fractures, and consider the rock matrix with other fractures as an equivalent isotropic medium. Parameters including the piezometric head above the tunnel center, the artery fracture angle, and the artery fracture spacing are studied and discussed. It is shown that both the piezometric head above the tunnel center and the artery fracture spacing affect the water inflow a lot. In this research, the influence of the artery fracture spacing on water inflow is larger than that of the piezometric head above the tunnel center when the artery fracture spacing 4.62 m. What is more, the artery fracture angle affects the water inflow slightly but it controls the flow direction. The water inflow case of the Huangjiagou Tunnel is used to verify the proposed model. The results show that the dual permeability model could give good predictions to the Huangjiagou Tunnel and describe the anisotropic flow behavior in stratified rock mass tunnels.

THE SEISMIC BEHAVIOUR OF TUNNELS IN LIQUEFACTION SOIL: A NUMERICAL STUDY

Underground structures can be severely damaged during strong earthquakes. Potential damage to infrastructure due to uplift increases in liquefied soils. Several models can be used to simulate soil liquefaction. This study presents a new numerical method to estimate the overall response of shallow-buried tunnels and to interpret the liquefaction mechanism in saturated sand around the structure under seismic action. The new method stems from the energy-based concept that can be used to compute the excess pore water pressure () and turn it into external forces that would cause the uplift of the underground structure. This study uses a comparative numerical study of implementing the computer code, FLAC on the seismic performance of underground structures using this energy-based approach procedure to estimate pore pressure built-up and evaluate the underground structures' uplift. Moreover, the proposed pore water pressure model is validated against well-documented laboratory data. Also, several study parameters have been considered to investigate the seismic behavior of tunnels.

Negative Capacitance, Negative Resistance in CNT/TiO2/SiO2/p-Si Heterostructure for Light-Emitting Diode Applications

The novel in this article is the appearance of negative capacitance at low frequency in this structure carbon nanotube/TiO2/SiO2/p-Si, which has not been studied yet in terms of its structural, electrical, and dielectric properties. The CNT/TiO2/SiO2/p-Si was synthesized as a metal oxide semiconductor (MOS) structure. The structural, electrical, dielectric, and capacitance were investigated by XRD, I-V, and C-V measurements. Besides the electrical properties, we present here a comprehensive study of capacitance and its variation with frequency, voltage, and temperature. Through this study, we can control and tune the capacitance in terms of its value as well as its signal polarity as positive or negative values the tunneling behavior and negative resistance were realized in I-V measurements. The capacitance vs temperature, voltage, and frequency was explored, it takes positive values reaching its maximum of about 2.12 × 10−9–2.4 × 10−7 F at high frequencies from 2 × 107–103 Hz, but at low frequency from 103–10 Hz, it takes high positive and negative values to reach 4 × 10−3–5 × 10−3 F respectively.

ANALYZING THE INFLUENCE OF THE EXPLOSION DEPTH ON THE STRESS-STRAIN BEHAVIOR OF CIRCULAR TUNNEL IN SATURATED SOIL

This paper presents the effects of the explosion depth on the stress-strain behavior of circular tunnel in saturated soil with 2 approaches: experiment and numberical method (SAP2000 ver 12.0). The result of experiment and numerical methods indicate the factors on the declining of explosion energy for design the tunnel in saturated soil subjected to blast loading purpose.

Seismic vulnerability of a soil-steel composite tunnel – Norway Tolpinrud Railway Tunnel Case Study

Transport infrastructure, such as tunnels and underground structures, are usually built using reinforced concrete solutions. Since the 1970s, many transport structures (culverts, bridges, tunnels and animal crossings) have been made from corrugated steel plates and surrounding backfill (also known as soil-steel structures). These structures are a good alternative to reinforced concrete solutions because they can be built rapidly with substantial 40–50% cost savings. The behaviour of soil-steel structures under typical static and dynamic loads is reasonably well recognised. However, the seismic analysis of these structures is usually conducted in a limited range, mainly for small culverts. Therefore, it is important to know how soil-steel composite tunnels behave under seismic excitations. The analysis in this work was made for the Tolpinrud railway tunnel in Norway. The paper presents the numerical analysis under seismic excitations using the DIANA FEA program based on the finite element method. Non-linear models with the El Centro and Ancona records were used to analyse the problem. Four different numerical models of the tunnel were considered. The paper analyses two methods of modelling the steel shell of the tunnel and the impact of using reinforced concrete (RC) beams to strengthen the shell. In models I and II, the shell was modelled as corrugated, and in models III and IV as flat. Additionally, it was found that the influence of additional RC beams (models II and IV) is negligible. Moreover, significant frequencies caused by given seismic excitations were determined. It was also found that the use of destructive earthquakes of similar intensity and different duration caused a low level of stresses in the soil-steel tunnel models. As a result of the conducted research, it was recommended that model I is the most suitable for this type of analysis. The obtained results can help recognise the behaviour of such tunnels located in seismic areas.

Numerical study on the behavior of utility tunnel subjected to ground surface explosion

Over the past few decades, underground utility tunnels have become increasingly popular in many countries, especially in North America and China. Utility tunnels host multiple services’ infrastructures inside an accessible underground space that allows regular inspection, maintenance, and easy replacement. Previous studies on the safety of underground utility tunnels were mainly focused on the seismic performances, their dynamic behaviors under accidental/hostile blast loads were seldomly investigated. TM 5-855-1 is frequently employed to calculate the ground shock load and responses of buried structures. However, it is only applicable for the cases with a scaled distance larger than 0.4 m/kg1/3. The present study performs a comprehensive numerical investigation on the blast performance of utility tunnel subjected to ground surface explosion with small scaled distance. With validated material and structural models, a FEM model based on a utility tunnel project is established. The influence of charge weight on blast resistance of the utility tunnel is studied numerically. The effect of the reinforcement ratio, shear reinforcement arrangement, buried depth and wall thickness are investigated under the scenario of a sedan car bomb overhead explosion. It is found that over 200 kg TNT ground surface explosion will cause a great threat to the utility tunnel with 2 m burial depth (scaled distance smaller than 0.4 m/kg1/3). The shear reinforcement arrangement is of great importance to the blast resistance of the utility tunnel. The failure mode of the roof can be changed from combined shear and flexural failure to flexural failure, with an increased reinforcement ratio. Increased wall thickness and buried depth can improve the blast resistance of the utility tunnel as expected. Safety buried depth, and wall thickness for a sedan car bomb overhead explosion are discussed in the present study.

Effects of the lining structure on mechanical and fracturing behaviors of four-arc shaped tunnels in a jointed rock mass under uniaxial compression

The diverse joint distributions in natural layered rock masses bring a great difficulty to the study on fracturing characteristics of surrounding rock in the process of tunnel excavation. The joint angle plays a vital role in the fracturing behaviors of tunnels. In this paper, taking the shallow-buried tunnel in layered rock masses as the background, a series of uniaxial compression tests were performed on the physical models containing joints and tubes made of high-strength gypsum. The fracturing characteristics of models with joints of different combinations are obtained, and the cracking mechanism of lining structure is further explored. Furthermore, the influences of linings on the stress distribution in surrounding rock and lining around tunnel and the displacement field in the model are investigated by a particle-based discrete element method. The supporting effect of lining on the stability of tunnels is finally evaluated.

Three-dimensional finite element analysis of urban rock tunnel under static loading condition: Effect of the rock weathering

Tunnel provide faster, safer and convenient way of transportation for different objects. The region where it is construction and surrounding medium has significant influence on the overall stability and performance of tunnel. The present simulation has been carried out in order to understand the behaviour of rock tunnel under static loading condition. The present numerical model has been validated with the laboratory scaled model and field data of underground tunnels. Both lined and unlined tunnels have been considered in this paper. Finite element technique has been considered for the simulation of static loading effect on tunnel through Abaqus/Standard. The Mohr-Coulomb material model has been considered to simulate elastoplastic nonlinear behaviour of different rock types, i.e., Basalt, Granite and Quartzite. The four different stages of rock weathering are classified as fresh, slightly, moderately, and highly weathered in case of each rock type. Moreover, extremely weathered stage has been considered in case of Quartzite rock. It has been concluded that weathering of rock and overburden depth has great influence on the tunnel stability. However, by considering a particular weathering stage of rock for each rock type shows varying patterns of deformations in tunnel.

Behavior of Soil Tunnel Digging when case of Tunnel Elharouche Skikda

The digging of one or more tunnels is a process that destabilizes the field, maintaining the stability of the tunnel wall and control of ground movements around the gallery resulting from each excavation and the interaction between two tunnels must be controlled. This research aims to analyze and understand the physical mechanisms games during the digging of two twin tunnels throughout the spatial configurations and evaluated the ground motion induced by the interaction between these two lasts. The three-dimensional effect of widening is taken into account using the decontainment  rate of soil adjacent to the excavation by the application of the convergence-confinement method. The modeling work is executed in two-dimensional, by using the finite difference code Flac-2D. A comparison of numerical simulation results with in-situ measurements was established in the particular case of two parallel horizontal tubes of the tunnel T4 on Elharouche Skikda and for which experimental data exist.

Research on the Development of China's Diversified Business Groups: Paragons or Parasites?

Diversified business groups are a relatively common form of modern economy, which plays a key role in China's economic development and market process. Under the new economic situation, diversified business groups conform to the trend of economic development and play important roles in optimizing capital allocation, promoting labour employment, and enhancing brand strength. However, the development of diversified business groups is a "double-edged sword", and the positive and negative effects it brings must be fully considered. This paper discusses the formation reasons and advantages of diversified business groups in China, and also objectively analyses the tunneling behaviour, diversified discounts and rent-seeking problems that occurred during the development process.

Predicting TBM performance in soft sedimentary rocks, case study of Zagros mountains water tunnel projects

Soft rock formations are widespread throughout the mountainous regions of the world including the mountains of western and southern Iran. Therefore, it is very common to pass through soft rock formations while building long tunnels for various purposes in the mountainous regions. The soft sedimentary rocks are frequently found in Zagros Mountains located in the south and west of Iran, where most of Iran's water conveyance projects (long and deep tunnels) have been constructed or are under construction. The behavior of these rocks in tunneling projects has received much attention in the past decades, but some features comprising the boreability and performance of tunneling machines in such rocks have received little attention. Many of these sedimentary rocks, especially those composed mainly of clay minerals, exhibit “non-structurally controlled” behavior in deep tunnels and below the groundwater level, and are completely continuous. During loading by disc cutters, these rocks usually exhibit plastic behavior, and the formation of chips in these rock types are often different than brittle and discontinuous rocks. Obviously, this necessitates the development of special models to predict the TBM performance in these rocks. In this study, the machine performance in soft rock formations along some of the Zagros Mountains water tunnel projects has been investigated. Efforts have been made to develop a special empirical model for continuous (intact) soft rock formations to complement the models presented in previous studies. Evaluation of the relationships between different geological and machine performance and operating parameters in these projects indicated that there is a strong correlation between intact rock properties (uniaxial compressive strength) and two parameters including penetration and cutter load. New empirical models developed based on statistical analyses of machine performance in these projects are presented for predicting TBM performance in similar conditions.

Conduction Mechanism of Chitosan/Methylcellulose/1-Butyl-3 Methyl Imidazolium Bis (Trifluoromethylsulfonyl) Imide (BMIMTFSI) Biopolymer Electrolyte Doped with Ammonium Triflate

Chitosan/methylcellulose/1-butyl-3 methyl imidazolium bis (trifluoromethylsulfonyl) imide (BMIMTFSI) biopolymer electrolyte has been prepared via solution casting technique by doping with different weight percentages of ammonium triflate (NH4CF3SO3) salt. The films were characterized by impedance spectroscopy to measure the ionic conductivity. Samples with 25 wt.% of NH4CF3SO3 exhibited the highest conductivity of 7.64 × 10-4 S cm-1 at ambient. Dielectric data showed that the increase in conductivity could be due to the increase in the number of charge carriers, while modulus study confirmed the non-Debye behaviour. Temperature dependence study showed that the polymer electrolyte system obeyed the Arrhenius rule. Conduction mechanism analysis showed that this system matched the Quantum Mechanical Tunnelling (QMT) behaviour. X-ray Diffraction (XRD) spectra, which had been deconvoluted using Origin 8 software disclosed that samples with the lowest degree of crystallinity (Xc %) obtained the highest ionic conductivity. On the other hand, Fourier Transform Infrared (FTIR) spectra, which were also deconvoluted using the same software showed that samples with the highest ionic conductivity had the highest number of mobile ions in this system.

Full-scale tests on smoke temperature distribution in long-large subway tunnels with longitudinal mechanical ventilation

Long-large subway tunnel accommodates the requirements of high-speed operation of trains, but also poses challenges on smoke control in case of tunnel fire. In conjunction with full-scale fire tests and theoretical analysis, this paper studies the fire behaviors of long-large subway tunnel by focusing on maximum ceiling smoke temperature rise, and smoke temperature rise distribution. The space downstream of fire source are divided into three zones, namely, inclined plume zone (Zone I), smoke entrainment zone (Zone II) and smoke column zone (Zone III). This paper proves that ceiling smoke temperature rise (CSTR) distribution at both Zone II and Zone III are exponential functions, but with different exponents. This paper proposes a method to compute the above exponents for Zone II and Zone III respectively. Full-scale tests verify that the proposed theoretical prediction method could predict the CSTR distribution with a relative error within 20%. Particularly, the proposed method is compared with several current computation methods, and is found has better correlation with the test data. Moreover, the measured maximum CSTR is found to be between the results of Kurioka’s model and Li Ingason’s model, and is closer with the later.