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Equatorial Plasma Bubbles (EPBs) are ionospheric irregularities that take place near the magnetic equator. EPBs most commonly occur after sunset during the equinox months, although they can also be observed during other seasons. The phenomenon significantly disrupts radio wave signals essential to communication and navigation systems. The national network of Global Navigation Satellite System (GNSS) receivers in Indonesia (>30° longitudinal range) provides an opportunity for detailed EPB studies. To explore this, we conducted preliminary 3D tomography of total electron content (TEC) data captured by GNSS receivers following a geomagnetic storm on December 3, 2023, when at least four EPB clusters occurred in the Southeast Asian sector. TEC and extracted TEC depletion with a 120-minute running average were then used as inputs for a 3D tomography program. Their 2D spatial distribution consistently captured the four EPB clusters over time. These tomography results were validated through a classical checkerboard test and comparisons with other ionospheric data sources, such as the Global Ionospheric Map (GIM) and International Reference Ionosphere (IRI) profile. Validation of the results demonstrates the capability of the Indonesian GNSS network to measure peak ionospheric density. These findings highlight the potential for future three-dimensional research of plasma bubbles in low-latitude regions using existing GNSS networks, with extensive longitudinal coverage.

Abstract We report our analysis of multi‐diagnostic ionospheric observations over Indonesia following the 15 January 2022 Tonga volcano eruption. Observation data from the Indonesian global navigation satellite system (GNSS) CORS network, ionosondes, and GNSS ionospheric scintillation and TEC monitor receivers, in conjunction with the Himawari‐8 satellite imagery, were used in the analysis. The Lamb waves from the eruption, traveling at ∼310 m/s, reached eastern part of Indonesia (∼5,000 km from Tonga) approximately 4 hr after the eruption. The Lamb waves traversed the Indonesian region for 4 hr and 40 min, around sunset period. As a result, some unseasonal equatorial plasma bubbles (EPBs) occurred over this longitude sector, with an interesting initial development pattern. There was a directional split in the zonal drift velocity of these EPBs, where some EPBs drifted eastward with a velocity of 138.0 ± 6.9 m/s and others westward with a velocity of 39.6 ± 2.0 m/s. At the same time, traveling ionospheric disturbances (TIDs) from the Tonga eruption also propagated over the Indonesian region with a velocity of 434.6 ± 21.7 m/s. In the total electron content (TEC) data, interactions between EPBs and TIDs were observed over the region. There were enhancements in the rate‐of‐TEC index (ROTI) and S4 scintillation index, indicating the presence of ionospheric density irregularities. A turbulent ionospheric F‐layer, due to these EPBs and TIDs, caused either spread‐F echoes or a loss of F‐region traces in the ionograms. An intensification of sporadic‐E layer, lasting for a few hours, was also observed in the ionograms.

Parameters of foam penetration in earth pressure balance (EPB) shield tunnelling, such as permeability coefficients and penetration distances, significantly impact tunnel face stability. However, existing studies have faced inaccuracies in analysing these parameters due to imitations in experimental methods. This study addresses this issue by employing enhanced methods for a more precise analysis of foam penetration. Experiments involving three distinct sand types (coarse, medium, and fine) and three foam expansion ratios (FER) (10, 15, and 20) are conducted using a modified model test setup. Benefiting from a novel computer vision-based method, the model test outcomes unveil two distinct foam penetration paths: liquid migration (Lw) and bubble migration (Lf). Three penetration phases — namely, injection, blockage & drainage, and breakage — are identified based on Lw and Lf variations. The initial “injection” phase conforms to Darcy's law and is amenable to mathematical description. The foam with FER of 15 has the maximum viscosity and, hence the Lf and permeability in the penetration tests with FER of 15 are the lowest in the same sand. The bubble size distribution of foam with different FER shows minor differences. Nevertheless, the characteristics of foam penetration vary due to the distinct particle size distribution (PSD) of different sands. Foam penetration creates low-permeability layers in both medium and fine sands due to the larger bubble size of the foam compared to the estimated pore sizes of medium and fine sands. While the coarse sand results in a different situation due to its large pore size. The distinctive characteristics of foam penetration in different sand strata are notably shaped by FER, PSD, and pore size distributions. These insights shed light on the complex interactions during foam penetration at the tunnel face, contributing valuable knowledge to EPB shield tunnelling practices.

We investigate the interactions between medium-scale traveling ionospheric disturbances (MSTIDs) and the equatorial ionization anomaly (EIA) as well as between MSTIDs and equatorial plasma bubbles (EPBs) on the night of 13–14 May 2013, based on observations from multiple instruments (an all-sky imager, digisonde, and global positioning system (GPS)). Two dark bands (the low plasma density region) for the MSTIDs were observed moving toward each other, encountering and interacting with the EIA, and subsequently interacting again with the EIA before eventually dissipating. Then, a new dark band of MSTIDs moved in the southwest direction, drifted into the all-sky imager's field of view (FOV), and interacted with the EIA. Following this interaction, a new dark band split off from the original dark band, slowly moved in the northeast direction, and eventually faded away in a short time. Subsequently, the original southwestward-propagating dark band of the MSTIDs encountered eastward-moving EPBs, leading to an interaction between the MSTIDs and the EPBs. Then, the dark band of the MSTIDs faded away, while the EPBs grew larger with a pronounced westward tilt. The results from various observational instruments indicate the pivotal role played by the high-density region of the EIA in the occurrence of various interaction processes. In addition, this study also revealed that MSTIDs propagating into the equatorial region can significantly impact the morphology and evolution characteristics of EPBs. [ABSTRACT FROM AUTHOR]

This paper presents measurements of total pressures and pore pressures in the mixing chamber, the pore pressures in the soil in front of an earth pressure balance (EPB) at the Botlek Rail tunnel, as well as laboratory tests on foam infiltration behavior from foam–sand mixture to saturated sand. It shows that the plastering effect at the tunnel face is less effective for an EPB shield than for a slurry shield, as the pressure fluctuations are greater in the mixing chamber for an EPB shield, suggesting a higher water leakage at the tunnel face. The difference in the development of excess pore pressure at two different locations of the EPB shield suggests the influence of the soil permeability. Foam infiltration at the tunnel face can result in a low permeable layer that restricts the ground water flow. Results from laboratory tests suggest that foam infiltration will be influenced by foam injection ratio and soil permeability. As the foam infiltration length is only limited, no low permeable layer can be formed during drilling for fine sand conditions. While a larger foam infiltration length can be expected for medium sand condition. Field measurements on the development of pore pressures in the soils at the two different locations show agreement with the conclusions from laboratory tests. [ABSTRACT FROM AUTHOR]

Space based radio wave communication and navigation has become need of the society. Atmospheric (thermospheric-ionospheric) processes, such as Equatorial Plasma Bubbles (EPBs), affect the radio waves propagating through this region, causing heavy perturbations on signals received at ground. This paper investigates the causative mechanism of EPB through the ground based remotely sensed imaging observations of O (1S) 557.7 nm and O (1D) 630.0 nm emissions emanating from the upper mesosphere (∼100 km altitudes) and thermosphere-ionosphere (∼250 km altitudes) over a low - latitude station, Kolhapur (16.8° N, 74.2° E, and dip lat. 10.6°N). Our investigation revealed that the gravity waves evident in OI557.7 nm images exhibit a close association with the observed EPB structures. These mesospheric gravity waves were found to travel from the South to North with horizontal wavelengths ∼35 and ∼56 km on 13–14 April and 26–27 April 2015, respectively. The thermosphere-ionosphere measurements exhibited occurrence of the North–South aligned EPB moving to the east with an inter depletion distance (IDD) equal to ∼44 km and ∼64 km. These results provide evidences on association of the gravity waves with the EPB. [ABSTRACT FROM AUTHOR]

The content of this study combines city safety, optimum excavation situation, mining, geology, and civil engineering principles. Tunnel boring machines (TBM) are the most commonly used machines in the excavation of urban tunnels. These machines prevent the inward movement of the tunnel face and control the amount of settlement formed on the ground by applying pressure to the tunnel face. The most important question here is to determine the amount of pressure to be applied to the tunnel face. There are many widely accepted formulas used in the calculation of the face pressure and these formulas generally attempt to limit the settlements on the ground by using parameters such as groundwater level, overburden thickness, physical and mechanical properties of the surrounding rocks, etc. In this study, a new formula was developed. This new formula calculates the face pressure required to be applied by EPB to the tunnel face in order to prevent damage to a structure located on the route and within the area to be affected by tunnel excavation, instead of only preventing settlements on the surface. In the formula, produced within the scope of this study, in addition to other studies, 3D distances of the structure to which the deformation limitation will be made to prevent damage is also one of the parameters. [ABSTRACT FROM AUTHOR]

We investigate in detail the occurrence and evolution of ionospheric equatorial plasma bubbles (EPBs) during a moderate storm on 17 September 2021, using Global‐scale Observations of the Limb and Disk (GOLD) observations and Whole Atmosphere Community Climate Model‐eXtended (WACCM‐X) simulations. GOLD observations show that there were no EPBs on 16 September before the storm but EPBs occurred after the storm commencement on 17 September. The EPBs extended to ∼30° magnetic latitude. A diagnostic analysis of WACCM‐X simulations reveals that the rapid enhancement of prompt penetration electric fields (PPEFs) after the sudden storm commencement is the main reason that triggered the occurrence of the EPBs. Further quantitative analysis shows that vertical plasma drifts, which are enhanced by the PPEF, played a dominant role in strengthening the Rayleigh‐Taylor instability, leading to the occurrence of the EPBs and the large latitudinal extension of the EPBs to ∼30° magnetic latitude during the night of 17 September. Plain Language Summary: Equatorial plasma bubbles (EPBs) are frequently observed in the equatorial region after sunset and have been the focus of ionospheric research. They are an important space weather phenomenon that often significantly impact trans‐ionospheric radio wave signals. During geomagnetic storms, the occurrence and evolution of EPBs are more complicated, and their physical mechanisms are worthy of further investigation. In this study, we used Global‐scale Observations of the Limb and Disk (GOLD) observations and Whole Atmosphere Community Climate Model‐eXtended (WACCM‐X) simulations to study the occurrence and evolution of EPBs during a moderate storm on 17 September 2021. GOLD observations show that EPBs occurred after the storm commencement on 17 September, whereas no EPBs were observed on 16 September. Additionally, these EPBs extend to ∼30° magnetic latitude. According to the WACCM‐X simulation analysis, the rapid enhancement of the prompt penetration electric fields (PPEFs) after the sudden storm commencement resulted in a significant Rayleigh‐Taylor instability (RTI) on 17 September, triggering the occurrence of EPBs. Furthermore, quantitative analysis revealed that PPEF induces enhanced vertical plasma drifts, which are the main reason for the strengthening RTI and the large latitudinal extension of the EPBs on 17 September. Key Points: Equatorial plasma bubbles (EPBs) extended poleward to ∼30° magnetic latitude during a moderate storm on 17 September 2021Diagnostic analysis reveals that occurrence of EPBs was due to rapidly enhanced eastward prompt penetration electric field (PPEF) after the sudden storm commencementPPEF‐driven upward drifts are the main factor causing large Rayleigh‐Taylor instability, and thus the formation and large latitudinal extension of the EPBs [ABSTRACT FROM AUTHOR]

Abstract We investigate in detail the occurrence and evolution of ionospheric equatorial plasma bubbles (EPBs) during a moderate storm on 17 September 2021, using Global‐scale Observations of the Limb and Disk (GOLD) observations and Whole Atmosphere Community Climate Model‐eXtended (WACCM‐X) simulations. GOLD observations show that there were no EPBs on 16 September before the storm but EPBs occurred after the storm commencement on 17 September. The EPBs extended to ∼30° magnetic latitude. A diagnostic analysis of WACCM‐X simulations reveals that the rapid enhancement of prompt penetration electric fields (PPEFs) after the sudden storm commencement is the main reason that triggered the occurrence of the EPBs. Further quantitative analysis shows that vertical plasma drifts, which are enhanced by the PPEF, played a dominant role in strengthening the Rayleigh‐Taylor instability, leading to the occurrence of the EPBs and the large latitudinal extension of the EPBs to ∼30° magnetic latitude during the night of 17 September.

Recent years have witnessed several accidents associated with tunnel face failure in cobble-rich soil in the city of Chengdu, China. Due to its lack of cohesion, cobble-rich soil can be easily disturbed by shield tunneling. Based on the general conditions of the Chengdu Metro Line 1 project, the mechanisms of face failure of tunnels in cobble-rich soil driven with earth pressure balance (EPB) machines are studied. Specifically, we present results of tests carried out using a laboratory reduced-scale model of EPB tunneling operations in cobble-rich soil. The failure kinematics and limit face pressures are presented and analyzed. Then a three-dimensional (3D) discrete-element method (DEM) model, which is able to simulate the main EPB excavation processes is employed to gain further insight into the mechanisms of face failure in cobble-rich soil. Comparisons of these results with the observations based on previous studies are discussed. The results reveal a fundamentally different tunnel-face failure mechanism in cobble-rich soil in contrast with that in clayey or sandy soils. It shows that the ground movement during face failure is sudden in cobble-rich soil, which is different from the progressive mechanism in frictional–cohesive materials. The observed sinkhole at surface takes the shape of an oval, and the failure zone behind tunnel face extends almost as far as that ahead of the face, which is different from the observations in previous studies. The failure zone is found to be wider than that of sandy soils in both the transverse and longitudinal directions.

Estimating surface settlement induced by excavation construction is an indispensable task in tunneling, particularly for earth pressure balance (EPB) shield machines. In this study, predictive models for assessing surface settlement caused by EPB tunneling were established based on extreme gradient boosting (XGBoost), artificial neural network, support vector machine, and multivariate adaptive regression spline. Datasets from three tunnel construction projects in Singapore were used, with main input parameters of cover depth, advance rate, earth pressure, mean standard penetration test (SPT) value above crown level, mean tunnel SPT value, mean moisture content, mean soil elastic modulus, and grout pressure. The performances of these soft computing models were evaluated by comparing predicted deformation with measured values. Results demonstrate the acceptable accuracy of the model in predicting ground settlement, while XGBoost demonstrates a slightly higher accuracy. In addition, the ensemble method of XGBoost is more computationally efficient and can be used as a reliable alternative in solving multivariate nonlinear geo-engineering problems.

The use of Earth Pressure Balance (EPB) shields is still very modest for tunneling in urban areas in Brazil. This study analyzed and integrated geological data and excavation parameters of a segment of Route 2 (Lot 3) of the Line 5—Lilac (São Paulo Metro), between Campo Belo Station and Jesuíno Maciel Shaft. This segment is 557 m long and represents one of the first experiences on tunneling in transitional mixed face with pressurized shield machines in Brazil. The excavation performed an average advance rate of 7.7 m/day and intercepted different proportions of gneisses, saprolites, and residual soils. The results show how the excavation parameters respond to different geological materials. The sections excavated in mixed transitional ground conditions had several negative effects on the excavation process, similarly to that described in other projects worldwide. Finally, results also suggested the nominal torque was insufficient for excavation of the segment. [ABSTRACT FROM AUTHOR]

One of the most widely used methods for the excavation of metro tunnels is mechanized excavation using an earth pressure balance (EPB) boring machine. Predicting the penetration rate of the boring machine can significantly reduce costs in mechanized excavation. Geological and geotechnical factors, machine specifications, and operational parameters can be influential on the penetration rate of the machine. Important geotechnical factors include cohesion, friction angle, and soil shear modulus. Among the important machine parameters, the thrust force of the jacks, the torque, and the rotational speed of the cutter head can be mentioned. In this study, after analyzing the main component, eliminating the outlier data, and normalizing the data, by considering the geotechnical factors and various parameters of the mechanized boring machine, the penetration rate of the EPB machine in the Tabriz metro line 2 tunnel has been predicted. For this purpose, linear regression methods, fuzzy logic using Mamdani and Sugeno algorithms, neuro-fuzzy method, and metaheuristic algorithms were used. To validate each model, statistical indices of the coefficient of determination (), root mean squares error (RMSE), and performance indicator (VAF) were used. The results of the studies showed that the neuro-fuzzy method has a better prediction of the penetration rate in comparison to other methods. Also, the results of the sensitivity analysis revealed that the cutter head torque had the greatest effect on the penetration rate of the EPB machine.

Previous studies show equatorial plasma bubbles (EPBs) mainly occur after sunset and usually drift from west to east. In this work, two EPBs occurred after midnight and lasted to sunrise, and were observed by multi‐instruments (two all‐sky imagers (ASIs), global positioning system, Swarm satellite, and a digisonde) during a geomagnetically quiet night of December 18–19, 2018. Our observations also show that plasma depletion structure (PDS) also occurred at that night. EPBs occurred in the region of PDS and showed a special evolution process during the night. Those PDS gradually disappeared with time, but strip‐like EPBs remained clearly in airglow images. Near sunrise, new PDS appeared to merge with those EPBs to form large PDS. Meanwhile, EPBs showed different zonal drifts within a very narrow longitudinal zone (∼2°). One EPB remained stationary while the other showed a small eastward drift. These results are different from post‐sunset EPBs in previous studies. During the lifetime of those ionospheric plasma irregularities, upward and downward motion of the peak height and virtual height of the ionospheric F region was observed by a digisonde, which indicates that the evolution of EPBs should be related to the vertical drift of ionospheric plasma. Besides, based Thermosphere‐Ionosphere‐Electrodynamics General Circulation Model (TIE‐GCM) simulations, we suggest the different zonal drifts of those EPBs might related to plasma zonal drifts caused by zonal winds. Key Points: The evolution of equatorial plasma bubbles (EPBs) occurring in the region of plasma depletion structure, from post‐midnight to sunrise, were observed during a geomagnetically quiet nightEPBs showed different zonal drifts in the observations: one remained stationary and the other drifted eastwardVertical drifts of ionospheric plasma are the driver of EPB evolution and different zonal drifts may be related to zonal wind variations [ABSTRACT FROM AUTHOR]

Recent years have witnessed several accidents associated with tunnel face failure in cobble-rich soil in the city of Chengdu, China. Due to its lack of cohesion, cobble-rich soil can be easily disturbed by shield tunneling. Based on the general conditions of the Chengdu Metro Line 1 project, the mechanisms of face failure of tunnels in cobble-rich soil driven with earth pressure balance (EPB) machines are studied. Specifically, we present results of tests carried out using a laboratory reduced-scale model of EPB tunneling operations in cobble-rich soil. The failure kinematics and limit face pressures are presented and analyzed. Then a three-dimensional (3D) discrete-element method (DEM) model, which is able to simulate the main EPB excavation processes is employed to gain further insight into the mechanisms of face failure in cobble-rich soil. Comparisons of these results with the observations based on previous studies are discussed. The results reveal a fundamentally different tunnel-face failure mechanism in cobble-rich soil in contrast with that in clayey or sandy soils. It shows that the ground movement during face failure is sudden in cobble-rich soil, which is different from the progressive mechanism in frictional–cohesive materials. The observed sinkhole at surface takes the shape of an oval, and the failure zone behind tunnel face extends almost as far as that ahead of the face, which is different from the observations in previous studies. The failure zone is found to be wider than that of sandy soils in both the transverse and longitudinal directions. [ABSTRACT FROM AUTHOR]

The Constellation Observing System for Meteorology, Ionosphere, and Climate (COSMIC) Radio Occultation data has been previously used as a way of investigating the climatology of Equatorial Plasma Bubbles (EPB). These low‐density regions can cause random phase and amplitude scintillation of satellite signals and forecasting these is an important priority in the space physics community. The ability to build useful forecasting models depends on the underlying data sets used in testing and validating these models. Correctly identifying days of EPB activity is important, but statistical studies using large data sets require the use of automated detection methods. Many of these detection methods heavily reduce data sets by removing unfavorable data, such as COSMIC profiles where the maximum scintillation occurs in the E region. This study presents a new F region s4max9sec index that can be used to study the presence of F region scintillation without excluding profiles that exhibit E region scintillation. The new index is shown to decrease EPB occurrence through the increase in available data, and is also shown to detect EPB events previously excluded from climatological studies. Calculation of the climatology using the new index is shown to resolve some differences that exist in the EPB climatology literature, particularly the location of the maximum scintillation occurrence during the equinox seasons. The use of this index is highlighted as a potential for studying F region scintillation in the presence of E region scintillation; an area of research that needs to be expanded for a complete understanding of EPBs. Key Points: A new F region S4max9sec index is proposed for investigating F region scintillationCOSMIC EPB climatology is improved using the new index which increases available F region data providing agreement with other studiesThe new index is used to highlights that the difference between EPB climatology maxima in the literature is due to data selection criteria [ABSTRACT FROM AUTHOR]

How can online government platforms meet principles of inclusivity and deliberation? We reflect on this question based on a recent case of online participatory budgeting in a neighborhood of The Hague, the Netherlands (Duinoord Begroot). In terms of inclusivity, our findings suggest that sending out personal invitations and setting few voting requirements can contribute to online voting rates. Furthermore, the use of few participation criteria in the initial stages of the process can enhance the diversity of gathered ideas. In terms of deliberation, we discuss how the structure of an online platform may ‘nudge’ citizens towards deliberation. The results indicate that while the platform generated an equal distribution of arguments in favor of and against proposals, it did not engage citizens en masse in online discussions. We suggest that building incentives and feedback loops into the platform could address this limitation.

Geotechnical and tunneling aspects during the construction of the U5 in Frankfurt am Main The new district Europaviertel in Frankfurt is developed, and will be connected to the public transport system. Therefore, two tunnel tubes of 7.1 m in diameter and approximately 840 m in length will be excavated with an EPB‐TBM. The ARGE U5 Europaviertel, PORR and Stump, were selected by the client, the Stadtbahn Europaviertel Projektbaugesellschaft (SBEV), to build the tunnels. The start for the tunnel drive of the south tube was in August 2019. The project has challenging subsoil conditions. Especially the Frankfurt Clay with chalk and sandstone layers is important but also the western part, directly after the start of each tunnel drive, is challenging due to the heterogeneous subsoil conditions, too. [ABSTRACT FROM AUTHOR]

Molecularly identified indigenous entomopathogenic bacteria (EPB) Xenorhabdus have been used to access their efficiency against cotton Aphid Aphis gossypii (Glov.). An efficient formulation of different parts of bacterial culture such as, cell-free supernatant, crude cell extract, bacterial culture and methanol extract in in vitro and green house condition have been exploited. The results have shown that different formulants of EPB produced significant effects on Aphid mortality, change in population density, population reduction and fecundity. Cell-free supernatant of new EPB species Xenorhabdus steinernematis n.sp. strain PAK. CB10 (KU097324) and the other X. indica PAK. S.B.56 (MF521953) resulted in both the highest mortality rate [(94.33±2.05, 100.00±0.00)%] @ 300µl/10ml at 30ºC and the lowest fecundity [(65.00±3.00) eggs/gravid female] in green house condition after 5 days of treatment. Crude cell extract of all bacterial fractions were found to be least effective as compared to cell-free supernatant, bacterial suspension and methanol extract suggesting that EPB has the potential to release its metabolites with insecticidal mode of actions in the surrounding culture media. New species proficiency was evaluated in comparison with other indigenous isolates and resulted in most efficient at 30ºC after 24h and proved to have good effectiveness as biological control agent and can be easily used instead of live bacteria in future formulations. [ABSTRACT FROM AUTHOR]

Water spewing from the screw conveyor often occurs in cohesionless soil strata below the groundwater level during tunnel excavation with earth pressure balanced (EPB) tunnel boring machines (TBM). Foaming agents have been extensively employed as soil conditioner during the use of EPB TBMs to change the properties of soil, and the conditioned soil, with its low permeability, was the key to reduce the frequency of water spewing. To determine effect of foam parameters on cohesionless soil permeability, the conditioned sand permeability under different foam liquid half-lives ( T hl ) foam expansion rates (FERs), and foam injection rates (FIRs) was tested. To verify the permeability test results, a case study was carried out to optimize the foam parameters for preventing water spewing. Based on these results, this paper suggests that high-stability foaming agents with a medium FER and FIR represent an effective way to reduce cohesionless soil permeability and to prevent water spewing. [ABSTRACT FROM AUTHOR]

Deep, but uneven, weathering of rock is common in tropical and sub-tropical areas. Infrastructure development in many Asian cities has required tunnelling through weathered rock profiles. The ground conditions for the tunnelling typically include saprolite, rock, and mixed faces of soil and rock. Where the rock is strong, and mixed ground is anticipated to be encountered over a significant proportion of the drive, slurry TBMs are typically specified in Singapore, based on local experience. Case studies of slurry and EPB tunnelling in mixed ground conditions, from Hong Kong, are presented, and compared, to illustrate the issues involved. For the EPB drive, there were very large increases in the Penetration Index and Specific Energy when working in pressurised EPB mode in ground conditions comprising >50% strong or stronger rock. In these ground conditions the rate of disc cutter replacement was significantly higher than when tunnelling in open mode in a full face of rock, on the same drive. Average progress rates fell to less than 3m per week in the most extreme conditions of 85% to 99% rock, with most of the time being spent on interventions, including a significant proportion of time required to cool the excavation chamber. It is postulated that these observations are related to the clogging of the cut chips of rock in the tool gap, ahead of the cutterhead, when the cut rock becomes the majority of the spoil. A slurry shield in comparable conditions in Hong Kong did not experience the spikes in Penetration Index, Specific Energy, or cutter wear, in mixed ground conditions, that were experienced during the EPB drive. [ABSTRACT FROM AUTHOR]

The need for rapid construction of the tunnel along with the safety of surface structures has increased the use of mechanized tunnel boring machines in the urban environment. In this paper, shield mechanized tunneling is introduced as one of the modern tunneling methods. In the following, the mechanism of operation of the TBM-EPB as the most commonly used boring machine in urban environments, along with the benefits of using this device, and the new technologies in the design of all-section boring machines, are introduced. Considering the importance of surface settlement in urban environments, controlling soil pressure, continuous injection of grout and controlling the volume of excavated materials, is one of the most important ways of preventing surface settlement in tunneling using a mechanized boring machine. In this study, the Plaxis software is used to investigate the effect of cement grout injections between the outer surface of concrete linings and the shield of the machine during tunnel boring operations on the surface settlement.

The performance of earth pressure balanced tunnel boring machines (EPB-TBM) is dependent of a variety of parameters. Moreover, these parameters interact in a rather challenging way, making it difficult to adequately model their behaviour. Artificial neural networks have the aptitude to model complex problems and have been used in a variety of construction engineering problems. They can learn from existing data and then be used to predict the results, which makes them adequate for modelling problems where large amount of data is generated. In this work, a multilayer feedforward artificial neural network has been used to predict the torque at the cutter head of an EPB-TBM. A time series neural network has been used, where torque was predicted as a function of the measured torque and the volume of the injected foam on previous time steps. Results indicate that feedforward artificial neural network can be used to predict the torque at the cutter head in a EPB-TBM [ABSTRACT FROM AUTHOR]

Clogging can be a massive problem during the mechanized excavation of tunnels. Soil conditioning with foams and/or polymers is normally used in these cases to decrease the adverse effect of clogging. In a research project the cone pull‐out test was used to assess the variation of adherence for four sticky clays with four commercial additives. Results show that the additives have also an impact on the basic mechanical properties of the clays such as liquid limit, plasticity index and shrinkage limit. The tests were performed on the one hand by spraying the additives on the metal surface of the cone and on the other hand by directly mixing them to the clays to reach the critical consistency index (i.e. where the maximum adherence with water was observed). Sprayed cone tests show for two clays a decrease in adherence. However, by directly mixing the additives to the clay, adherence considerably decreases, except for one kaolinitic clay. The results can be useful to select suitable additives or to develop new ones considering the geotechnical and mineralogical properties of the excavated clays. [ABSTRACT FROM AUTHOR]

Earth pressure balance (EPB) tunnel boring machines are shield machines that rely on their own excavated material as a support medium to maintain the support pressure at the face. This material also needs to have the necessary properties to be extracted, transported and, finally, disposed of. Whenever the natural material does not fulfil the necessary requirements, additives like water, foam, polymers, and fines, must be added, modifying the excavated ground to the desired conditions. The rheological properties of any excavated material, together with any additives, must be investigated and understood, as they will influence the flow behaviour of this conditioned material, directly affecting the machine operation and tunnel logistics. While studies assessing the flowability related to the EPB excavation of sand or clay soils are available, there is a lack of information on mixed soils. This paper presents the results from a testing campaign with mixed clay‐sand samples, aiming to reproduce a simplified tropical weathered mixed soil, investigating its flow behaviour when changing certain controlled variables: clay‐sand proportions, clay mineral, size of the clastic grain mixed with clay, water content, and additives (foam and polymers). Results from the tests conducted with a flow table, a slump test, and a rheometer device were compared, providing insights about the flow behaviour of the tested samples and its interaction with an EPB machine. [ABSTRACT FROM AUTHOR]

Cross-sectional, observational study. There is little reported on the in vivo mechanics and behavior of extensor pollicis brevis (EPB) in relation to wrist position. Wrist position is known to significantly influence tendon excursion and therefore function of the digits. Ultrasound imaging (USI) can be used to assess in vivo tendon behavior and excursion. An improved knowledge of the excursion of the EPB tendon is important in understanding normal tendon mechanics and potentially pathological tendon disorders such as de Quervains tenosynovitis. To assess the reliability of using USI to measure EPB tendon excursion and to quantify EPB tendon excursion in 3 wrist positions. USI with speckle-tracking analysis were utilized to assess 49 normal EPB tendons (25 subjects). Tendon excursion was measured in wrist flexion (45°), wrist neutral and wrist extension (45°) on 2 different occasions. The within- and between-session reliability of using USI to quantify EPB tendon excursion was "excellent" and "high," respectively. Wrist position had a significant influence on EPB tendon excursion (P ≤.05). EPB excursion in the neutral wrist position was statistically greater than the other 2 positions (P <.05). EPB tendon excursion has been shown to be dependent on the wrist positions of flexion and extension. The measures are notably lower than those found in cadaver studies; however, they follow a similar pattern with greatest excursion occurring in the neutral wrist position and least in flexion. This information is useful for EPB tendon rehabilitation and in consideration of biomechanics and pathogenesis of disorders that affect EPB tendon. In vivo EPB tendon excursion measures have been quantified, and wrist position has been found to have an influence on excursion. USI with speckle-tracking analysis are considered to be reliable methods for measuring EPB tendon excursion. • We assessed extensor pollicis brevis (EPB) tendon excursion with ultrasound imaging, during composite movement of the thumb, in 3 different wrist positions: neutral, extension, and flexion. • Fourty nine EPB tendons were imaged, from 25 participants. • The within-session reliability of quantifying EPB tendon excursion with ultrasound imaging was "excellent" (intraclass correlation coefficient: 0.87) and between-session reliability was acceptable (intraclass correlation coefficient: 0.76). • Wrist position had a statistically significant (P <.05) influence on EPB tendon excursion, with the greatest amount of EPB tendon excursion occurring with the wrist in neutral (2.78 mm). • The research represented level 4 evidence. [ABSTRACT FROM AUTHOR]

This present paper presents an adopted methodology for Micro Tunnel Boring Machine (TBM) selection, based on the results of a geological-geotechnical feasibility assessment of a microtunnel, planned for a natural gas pipeline beneath an active landslide, in the Corovode area, southern Albania. This example offers an excellent case study of diverse and demanding engineering geological formations, namely disturbed and sheared types of flysch rock masses, but also recent soil deposits. A tunnel drive will confront materials that may be prone to posing challenges, such as ravelling ground at the microtunnel face, chimney failures, water inflows, as well as deformations. The selection of the appropriate tunnelling method procedure is analysed and presented step by step, addressing all issues that cover the most critical aspects of the selection process. Finally, a geotechnical feasibility assessment is presented as an overall analysis of this work, taking into consideration all the crucial design parameters for several Micro TBM types along the tunnel. Besides the expected rock mass behaviour, the TBM selection is also based on the percentage of fines at the tunnel excavation profile, the permeability and hydraulic head, which is also investigated in this study, while sticky behaviour, clogging risk, presence of obstacles and mixed ground conditions are also taken into account. [ABSTRACT FROM AUTHOR]

Technological progress in tunneling has led to modern and efficient tunneling methods in vast underground spaces even under inappropriate geological conditions. Identification and access to appropriate and sufficient geological hazard data are key elements to successful construction of underground structures. Choice of the method, excavation machine, and prediction of suitable solutions to overcome undesirable conditions depend on geological studies and hazard analysis. Identifying and investigating the ground hazards in excavating urban tunnels by an EPB machine could augment the strategy for improving soil conditions during excavation operations. In this paper, challenges such as geological hazards, abrasion of the machine cutting tools, clogging around these tools and inside the chamber, diverse work front, severe water level fluctuations, existence of water, and fine-grained particles in the route were recognized in a study of Tehran subway line 7, for which solutions such as low speed boring, regular cutter head checks, application of soil improving agents, and appropriate grouting were presented and discussed. Due to the presence of fine particles in the route, foam employment was suggested as the optimum strategy where no filler is needed.

Water spewing from the screw conveyor often occurs in cohesionless soil strata below the groundwater level during tunnel excavation with earth pressure balanced (EPB) tunnel boring machines (TBM). Foaming agents have been extensively employed as soil conditioner during the use of EPB TBMs to change the properties of soil, and the conditioned soil, with its low permeability, was the key to reduce the frequency of water spewing. To determine effect of foam parameters on cohesionless soil permeability, the conditioned sand permeability under different foam liquid half-lives ( T hl ) foam expansion rates (FERs), and foam injection rates (FIRs) was tested. To verify the permeability test results, a case study was carried out to optimize the foam parameters for preventing water spewing. Based on these results, this paper suggests that high-stability foaming agents with a medium FER and FIR represent an effective way to reduce cohesionless soil permeability and to prevent water spewing.

Due to large porosity, high soil friction, less cohesion, low flow of waterless sand-pebble stratum and the problem of very difficult in achieving a soil pressure balance in the shield front during the earth pressure balance (EPB) shield construction process, the soil conditioning for EPB excavation in the waterless sand-pebble stratum along Urumqi rail transit line 1(L1) is studied. A series of laboratory tests are performed to investigate and assess the properties of selected additives and the conditioned soils. The additives test results show that foam A with relative higher half-life, foaming ratio and adhesion thickness can be adopted preferentially; the most optimal mass concentration ratio of three types of bentonites (named S1, S2 and S3) slurry are 1:6, 1:10 and 1:15, respectively when funnel viscosity is around 64/s. The slump test results showed a trend of increasing after first decreasing to zero when using a single additive such as water or bentonite slurry indicate single additive cannot achieve a better soil conditioning effect. Slump value can reach about 230 mm when conditioned the soil with 14% water content and only added 15% of the foam (concentrate rate is 3%), and the conditioned particles on the surface sediment are evenly dispersed, which is able to achieve an ideal effect in the shield. Economic and reasonable soil conditioning ratio is the water content to 14% + 6% bentonite (bentonite ratio is 1:15, funnel viscosity is 65.08/s) + 5% foam with the concentrate rate of 3%. The results can be used to provide guidelines for the excavation by use of EPB machine under such soil conditions. [ABSTRACT FROM AUTHOR]

Foam as a soil conditioning agent has been extensively employed in earth pressure balanced (EPB) tunnel boring machines (TBM) to change the mechanical and hydraulic properties of soils for effective excavation. Foam stability is a critical parameter that influences the performance of foam and foam-conditioned soils. This paper examines foam stability under pressure through a novel foam generation – pressure chamber – foam capture testing system. A comprehensive suite of foam experiments was performed to examine the physical phenomenon of foam degradation and time-dependent foam properties under pressure. Testing results suggest that foam liquid loss is not an effective indicator for characterizing foam stability, while foam volume loss is a more appropriate measure of foam stability. Results also reveal that foam liquid drainage is significantly retarded at higher chamber pressure because foam bubbles are smaller and more uniform. Bubble size was not appreciably different in dry and wet foams. [ABSTRACT FROM AUTHOR]

This paper interprets ground movements induced by tunnel construction, by comparing monitoring data with analytical and numerical predictions based on an assumed set of deformation parameters at the cavity boundary. By minimizing differences between the computed and measured ground movements, optimal cavity deformation parameters can then be used to characterize the performance of the tunneling process. We compare the performance of three tunnel construction methods in stiff clay: (i) closed-face excavation using an Earth Pressure Balance (EPB) tunnel boring machine; (ii) open-face shield excavation; and (iii) sequential construction using the New Austrian Tunneling Method (NATM). The measured data were obtained from three projects in London each involving different tunnel size and depth, but all excavated through deep units of stiff London clay. The measured performance in each case is evaluated using analytical solutions, that assume linear elastic properties for an elastic half-space, and numerical simulations that use an effective stress soil model, MIT-S1, with input parameters calibrated to elemental behavior of the London Clay. Although the numerical analyses achieve better agreement with the measured data, the analytical solutions perform well and could be used in future studies. The results indicate that the closed-face tunneling provided the best control of volume loss, while open-face shield excavation caused the largest ovalization of the tunnel cavity. The proposed methodology offers a practical framework for cataloging and comparing tunnel performance in future projects. [ABSTRACT FROM AUTHOR]

The treatment of excavation by-products has been studied using Fenton and Heterogeneous Fenton processes, by the addition of zero-valent iron nanoparticles (nZVI) as catalyzer. This study demonstrated that both methods could significantly reduce the organic content of the liquid extract from excavated soils. Operating parameters, such as pH and catalyzer/oxidant (w/w) ratio, were varied to investigate their influence on the Total Organic Carbon (TOC) and Chemical Oxygen Demand (COD) removal efficiency. In addition, Biochemical Oxygen Demand (BOD) was evaluated before and after the treatment. The optimal conditions found for conventional Fenton process were: H 2 O 2 /COD = 1 (w/w), Fe(II)/H 2 O 2  = 0.1 (w/w) and pH = 2.5, whereas for Heterogeneous Fenton were: H 2 O 2 /COD = 0.75 (w/w), nZVI/H 2 O 2  = 1.5 (w/w) and pH = 3. Heterogeneous Fenton resulted more efficient with respect to conventional Fenton, leading to a TOC and COD removal efficiency equal to 75.95 and 85.52%, respectively. The BOD 28 /COD ratio after Heterogeneous Fenton increased by about 200%, indicating the suitability of this oxidation process to achieve a biodegradability increase. [ABSTRACT FROM AUTHOR]

Abstract: The Sydney Harbour crossing is a key element of Sydney Metro City & Southwest, which includes 15.5 km of twin tube running tunnels extending from Chatswood at the north through to Sydenham, south of the Central Buisness District (CBD). One of the key features is the 1 % length of the alignment that passes under Sydney Harbour. The rest of the alignment is through rock, but the harbour crossing is designed to pass through harbour sediments and mixed face conditions undersea. An in depth study and analysis was required to confirm the feasibility of the safe construction of this short length of the tunnel in sub‐aqueous, soft ground conditions. It was necessary to carry out detailed, targeted investigation of the ground to enable the selection of an appropriate tunnelling technique for constructing the tunnels. [ABSTRACT FROM AUTHOR]

Abstract: The capital of Qatar, Doha is being increasingly turned into a modern centre for industry, trade and sport. One essential precondition for this is the development of high‐capacity infrastructure with modern means of transport. This includes the construction of an underground railway network, which has to be completed in a very short time due to the football World Cup taking place in Qatar in 2022. The (part) project ”Metro Green Line Underground“ was awarded in summer 2013 to a Joint Venture comprised of Porr (lead), the Saudi Binladin Group and the local construction company HBK. It includes the turnkey completion of the underground part of the Green Line in the future underground system. This includes two tunnels with a length of 17 km each, six stations, crossover structures, several emergency exits and 32 cross passages and two road underpasses. The shield drive for the running tunnels began in late summer 2014 and could be completed after only 18 months of construction time in early 2016. In addition to explaining how the simultaneous operation of six EPB machines was successfully mastered, this article also describes the conventional tunnelling of the various connection and underpass structures under inner‐city conditions. [ABSTRACT FROM AUTHOR]

To guarantee effective EPB TBM face support and performance, it is necessary to understand the mechanical behavior of foam-conditioned soil under realistic pressure conditions. This paper investigates the behavior of foam-conditioned soil under applied total pressures of up to 5 bar. The study examines the effect of total stress, effective stress, and key soil parameter void ratio on the behavior of foam-conditioned soil. Shear strength and compression tests were carried out in a field-portable pressurized test chamber on two granular soils with a variety of foam parameters. The results demonstrate that void ratio and effective stress are the main factors that influence the performance of foam-conditioned soil. It was determined that a certain ratio of void ratio to maximum void ratio was required to prevent the development of appreciable effective stress and, thus, high shear strength and low compressibility. [ABSTRACT FROM AUTHOR]

A study was performed on the University Link and Northgate Link projects in Seattle, WA, to investigate the use of apparent density evaluation methods for the identification of air pockets and plugging issues in the chamber of EPB TBMs. Both air pockets and plugging issues can result from improper soil conditioning and the TBM’s inability to mix the soil properly with the conditioning agents. An apparent density below unity indicates the formation of an air pocket in the top part of the chamber and an apparent density above the virgin soil density points to developing plugging issues in the cutterhead bays and pressurized chamber. From the conducted study it can be concluded that the presented apparent density evaluation methods are an effective way to identify issues in the excavation chamber of an EPB TBM and can be used as a mean to improve the soil conditioning process. [ABSTRACT FROM AUTHOR]

The marine clay deposits covering the bedrock under the Norwegian capital Oslo are very sensitive to pore pressure reduction. Existing tunnels under the city are draining the ground to varying extents, which have led to settlement damages to buildings and infrastructure. Oslo is the fastest growing capital in Europe, and there is great demand for underground excavations for trains, roads, subways, power cables, water, and wastewater. It will be very important to limit drainage into new tunnels during the construction phase and in the permanent state. This paper discusses the possibilities and limitations of pressurized (closed-mode) TBM-shield tunneling as an alternative to traditional drill and blast (or open-mode TBM excavation) with pre-excavation grouting. Earth pressure balance and slurry shield machines with gasketed precast concrete segmental linings, which are normally used in soil and soft rock tunneling, may give superior drainage control compared to non-pressurized (open) methods; but these machines have challenges with high wear when used in hard rock. The use of traditional hard rock single-shield machines built with the option to convert into closed-static-mode is another, and probably a more realistic alternative, which should be considered in order to better control drainage during the construction phase. [ABSTRACT FROM AUTHOR]

Studies were conducted for soil improvement in earth pressure balance (EPB) shield tunneling in sandy cobble strata based on the construction of the Chengdu Metro project in China. The results indicate choice of improver and optimal soil proportions. For mid-density sandy cobble with 8% water content, a slurry injection ratio greater than 25% meets the construction requirements. A mixture of slurry and foam achieves construction efficiency and flow plasticity of soil for a slurry injection ratio of 15% and foam injection ratio of 80-100%. For dense sandy cobble, water content of 7.5-10% and foam injection ratio of approximately 40% - or a slurry injection ratio higher than 10% and foam injection ratio of approximately 30% is desirable. A foaming agent with water is a good improver for mid-density sandy cobble strata tunneling; i.e., soil water content of 8.6-11% and foam injection ratio of 60-100%. For dense sandy cobble strata, a mixture of slurry and foam is suggested as the improver; foam injection ratio of 40-80% and a slurry injection ratio of approximately 10%. [ABSTRACT FROM AUTHOR]

• Sedimentation of the mixture induces plastering effect in fine sand strata. • Foam infiltration dominates in coarse-grained sand condition. • Increase in foam injection ratio leads to better plastering effect at the tunnel face. • A'drier' muck can be beneficial to the plastering effect at the tunnel face. This paper investigates the foam infiltration behavior from foam-sand mixture, resulting from foam conditioning of excavated sand inside of the excavation chamber of an Earth Pressure Balance (EPB) shield, into saturated sand at the tunnel face. The laboratory investigation was conducted using one dimensional element tests that simulate foam infiltration from the mixture into the saturated sand in front of the tunnel face. Pore pressures at different locations are measured near the sand surface, representing the tunnel face, while the sand column could provide a comparable hydraulic gradient to field conditions. Influences from foam injection ratio (FIR), remaining water content and sand type are examined. In the case of fine sand, it is found that there is little foam infiltration from the foam-sand mixture into the sand surface. Sedimentation of the foam-sand mixture on top of the saturated sand column is the dominating process that results in a dense mixture containing less liquid content with a smaller permeability. While for coarse-grained sand, foam infiltration will result in a foam infiltration zone with a lower permeability than the sedimented foam-sand mixture. Plastering effect at the tunnel face will increase with an increase in FIR and a decrease in remaining water content. Further analysis indicates that the sand matrix plays an important role in determining the permeability of a foam-sand mixture, as a higher density of sand results in a more tortuous seepage path for water. Mechanisms are discussed and implications for field applications are described. [ABSTRACT FROM AUTHOR]

Ligand activation of the aryl hydrocarbon receptor (AHR) accelerates keratinocyte differentiation and the formation of the epidermal permeability barrier. Several classes of lipids, including ceramides, are critical to the epidermal permeability barrier. In normal human epidermal keratinocytes, the AHR ligand, 2,3,7,8-tetrachlorodibenzo-p-dioxin, increased RNA levels of ceramide metabolism and transport genes: uridine diphosphate glucose ceramide glucosyltransferase (UGCG), ABCA12, GBA1, and SMPD1. Levels of abundant skin ceramides were also increased by 2,3,7,8-tetrachlorodibenzo-p-dioxin. These included the metabolites synthesized by UGCG, glucosylceramides, and acyl glucosylceramides. Chromatin immunoprecipitation-sequence analysis and luciferase reporter assays identified UGCG as a direct AHR target. The AHR antagonist, GNF351, inhibited the 2,3,7,8-tetrachlorodibenzo-p-dioxin-mediated RNA and transcriptional increases. Tapinarof, an AHR ligand approved for the treatment of psoriasis, increased UGCG RNA, protein, and its lipid metabolites hexosylceramides as well as increased the RNA expression of ABCA12, GBA1, and SMPD1. In Ahr-null mice, Ugcg RNA and hexosylceramides were lower than those in the wild type. These results indicate that the AHR regulates the expression of UGCG, a ceramide-metabolizing enzyme required for ceramide trafficking, keratinocyte differentiation, and epidermal permeability barrier formation., (Copyright © 2023 The Authors. Published by Elsevier Inc. All rights reserved.)