Search

The bedding structure of layered tunnels has a significant impact on the evolution of excavation damage, yet research on the relevant evolution mechanisms is scarce. In view of this, this paper develops a mesh-free numerical method to simulate the progressive damage process of tunnel excavation and proposes a method for applying stress boundaries within the SPH framework. Through this method, simulations of tunnel excavation damage under different bedding dip angles and stress ratios are conducted. The results show that the following: in the simulation of excavation damage of a tunnel without bedding structures, specific areas around the tunnel exhibit characteristics of tensile–shear composite failure and shear failure, verifying the rationality of the algorithm; under different bedding dip angles, a damage zone is first generated around the tunnel, and shear cracks appear at the tangent of the bedding plane and the tunnel, with the damage degree being the largest when α = 30° and the smallest when α = 45°; and under different stress ratios, the damage starts around the tunnel, continuously evolves, and finally forms a failure zone inside the bedding plane joints tangent to the tunnel, and the damage degree increases with the increase in the stress ratio. This study discusses the damage mechanisms under different calculation schemes and provides a reference for understanding the excavation damage mechanisms of layered tunnels. [ABSTRACT FROM AUTHOR]

Slurry shields rely on the formation of a compact filter cake to maintain excavation face stability and ensure construction safety. In strata with high permeability, significant slurry loss occurs, making filter cake formation and air tightness maintenance challenging. In this study, light organic walnut shell was selected as an additive coarse particle material for slurry. Slurries incorporating two types of coarse particles, sand and walnut shell, were prepared, and tests on slurry permeation and air tightness of the filter cake were conducted in three different strata. The results indicate that the addition of coarse particles effectively improves filter cake formation and air tightness in high-permeability strata. It is essential to use graded particles in highly permeable strata, with controlled maximum and minimum particle sizes. As the content of coarse particles increases, the air tightness of the filter cake initially increases and then decreases. Notably, the air tightness of filter cakes containing walnut shell is superior to those containing sand. Replacing sand with walnut shell as a slurry plugging material enhances filter cake quality in high-permeability strata. For highly permeable strata with a permeability coefficient greater than 1.0 × 10−3 m/s, an addition of 30 g/L to 40 g/L is recommended. [ABSTRACT FROM AUTHOR]

The oasis of En-Gedi, on the western shore of the Dead Sea, served during the late Iron Age as a regional hub for the Judahite activity in the Judean Desert. The main Iron Age site in En-Gedi is Tel Goren, a small mound in the oasis plain, excavated in the 1960s by Benjamin Mazar and Immanuel Dunayevsky. The exposed Iron Age remains, attributed to the lowermost occupation (Stratum V), yielded substantial material assemblages associated with a thick destruction layer dated to the early 6th century b.c.e. The excavators interpreted the site as an unfortified, short-lived agricultural estate dedicated to the production of high-valued commodities. Drawing on a critical reassessment of past excavations, coupled with new evidence gathered in small-scale excavations conducted in 2020, it is suggested that the development of late Iron Age Tel Goren was a gradual process that involved at least two major phases, as well as the construction of a fortified compound on the summit of the hill. The implications of this suggestion are further examined within the broader regional and historical context, shedding new light on the multiphase trajectory of Judah's expansion into its eastern fringe during the late monarchic period. [ABSTRACT FROM AUTHOR]

The aim of this paper is to present the preliminary results of the recent osteological analysis of the human remains discovered to the north of the funerary temple of King Djedkare at south Saqqara. The excavation began in spring 2018 as a part of Djedkare Project of the exploration and documentation of the pyramid complex of king Djedkare, directed by Mohamed Megahed. This paper will investigate some of the burials discovered in the so-called T.g area which is situated between the funerary temple of the king and the south side of the pyramid of the queen. The burials date back from the late Second Intermediate Period probably to the 1st millennium BCE based on the preliminary analysis of the pottery. The burials were discovered in three levels, the earlier burials in the bottom levels of the debris were in extended north-south or east-west position. Also, the upper-level burials were in extended east-west positions. The Middle level contains burials in ceramic coffins Besides the variety of burial customs and the correlation between age, sex, and grave good, The good preservation of bones surface allowed to record the pathological diseases. Many evidences recorded for activity-related skeletal changes, including degenerative disease in the spines and other joints in the older adult groups. Moreover, trauma (including fractures) was noted in any individuals, affecting the shoulders, femurs, hands and pelvis. It is likely that childhood stress observed in several individuals in the form of iron deficiency anaemia and dental developmental disorders. In some cases, evidence for spondylolysis, which might have been unilateral or bilateral, was observed. More unusual pathological conditions observed included infectious defects in the skull of a young adult female and a possible case of blunt force trauma. Several dental diseases were observed in Djedkare secondary cemetery individuals, including tooth attrition, abscesses, ante-mortem tooth loss and calculus, which related to age changes. This preliminary overview study will contribute to add new non-elite cemetery results and aim to make it accessible for researchers additionally, investigate the biological profile as sex, age, stature. Moreover, sheds light on the distribution of pathologies inside the assemblage. [ABSTRACT FROM AUTHOR]

The rockburst phenomenon in excavation endeavours reveals a multitude of complexities and obstacles that significantly impact both the technical and financial dimensions of project execution. Investigating critical rockburst factors in underground excavations is of considerable importance for addressing pivotal safety issues and operational complexities within the field of underground excavation projects. This research proposes an innovative approach based on an expert-based fuzzy cognitive map (FCM) framework, aiming to identify and prioritize the key critical rockburst factors prevalent in underground excavations and tunnelling. A tailored cognitive map of the parameters of problem was constructed, integrating 56 critical and critical factors meticulously curated by a team of seasoned managers, engineers, deputy managers, trainee engineers and assistant managers. The structured cognitive map was meticulously developed, considering the relative weights of the identified critical factors and their intricate interrelationships—all informed by the invaluable insights and expertise of seasoned engineers in the field. Subsequently, the cognitive map underwent a systematic solution process, whereby the causal relationships and influences amongst the identified critical factors were analysed and factored in. The outcomes of the comprehensive analysis unveiled several critical factors: lack of rockburst risk assessments, high in situ stress, presence of rock seams and weak layers, rock quality variations, and geological heterogeneity as the most paramount concerns demanding immediate attention and strategic intervention. By adopting the proposed FCM approach and leveraging the collective expertise of industry professionals, this research offers a robust and systematic framework for comprehensively assessing and addressing the key challenges associated with rockburst events in underground excavations and tunnelling projects, thereby fostering enhanced project performance and efficacy within the field. Highlights: A comprehensive fuzzy cognitive map, based on industry professionals, emphasiSes 56 critical rockburst factors. In rockburst events, the created map considers factor weights, enabling systematic analysis and strategic intervention for project efficacy. Key concerns revealed include the absence of risk assessments, high in situ stress, rock seams, quality variations and geological heterogeneity. Utilising fuzzy cognitive map and industry expertise provides a robust framework for addressing rockburst challenges in underground projects. [ABSTRACT FROM AUTHOR]

An extensive database consisting of measurements of ground movements and pore pressures from 48 deep excavations is presented. The ground conditions for all cases are soft, normally consolidated clays, often underlain by a coarser layer of soil, i.e., confined aquifer, on top of bedrock. Traditionally wall and ground movements caused by deep excavations have been predicted without assessing effects of groundwater drainage or the influence of installation of tie-back anchors or foundation piles. This study clearly shows that the observed ground movements exceeded expected values based on induced shear movements and significant deformations occur at far distance from the excavation. The cause of the deformations is largely consolidation settlements due to pore pressure reduction, with a zone of influence recorded at up to 400 m distance from the excavation. The construction methods and opening of drainage paths to the confined aquifer is as important for pore pressure reduction, as exposing the confined aquifer itself. In addition, the groundwater drawdown is shown to be dependent on the ground conditions and mitigation measures. It is also shown that the pore pressure reduction and zone of influence may be very small if no drainage path is created, i.e., in case of strutted excavations and no piles or driven piles, or when the bedrock surface is not exposed. The drilling of tie-back anchors and piles are also seen to influence ground movements, especially at a distance of 2–4 times the excavation depth. Charts produced from the database enable estimation of expected groundwater drawdown including zone of influence. In addition, they can support decisions on construction methods, need for mitigating measures and extent of monitoring program in relation to deep excavations. [ABSTRACT FROM AUTHOR]

The release of ground stress brought on by overlying excavation poses a significant threat to regular tunnel operation, especially when the foundation pit intersects the tunnel inclination, and the torsional deformation of the tunnel also needs to be considered. Based on the foundation pit intersecting with the subway tunnel at an angle, the U-shaped soil reinforcing (USR) technique was introduced to limit the tunnel heave produced by overlying excavation. The Topcon MS05A automated monitoring system was used to track the following: (1) the evolution of the tunnel heave over time and space; (2) the convergent deformation of the cross section; and (3) the torsional deformation. The reinforcement efficiency of the USR method was assessed with numerical simulations, and the effect of intersection angles and reinforcement dimensions on the deformation of the underlying tunnel was further discussed. In addition, an optimal design was suggested for the USR method that considers cost. Tunnel deformation utilizing the USR method was reduced by 63.40%, and the maximum heave was observed to be merely 6.5 mm. The influence zone on the tunnel by overlying excavation was up to 2.5 times the excavation widths, and the tunnel always produced clockwise rotation. Backfilling generates significant and sharp distortion, so the backfilling speed must be carefully controlled. The foundation pit spanning the tunnel at a small angle caused a bigger heave and torsion of the tunnel, which should be avoided. The proposed optimization approach can determine the cost based on the tunnel deformation control criteria. This study provided a valuable reference for the protection of adjacent excavations of subway tunnels in deep sandy strata. [ABSTRACT FROM AUTHOR]

To avoid engineering challenges during roadway excavation or workface mining in weakly cemented soft rock, the characteristics of this rock under the influence of associated stress paths must be explored. Therefore, this study investigates the principal strain and generalized shear strain of weakly cemented soft rock under a directional shear stress path, through a series of principal-stress directional shear tests conducted using a hollow cylinder apparatus. The damage morphology characteristics for different major principal-stress directions are also discussed. The results show that the major principal strain (ɛ1) gradually increased with increasing major principal-stress direction angle (α), when α ranges from 0° to 45°, whereas the minor principal strain (ɛ3) and intermediate principal strain (ɛ2) gradually decreased. The peak stress of the soft rock gradually decreased and a main slip-damage crack developed in the major principal-stress direction. The peak generalized shear strain increased slowly in the first compression–torsion stage and rapidly in the second. As α ranges from 45° to 90°, ɛ1 and ɛ2 decreased gradually whereas ɛ3 increased gradually. The peak stress also increased slowly, with the main crack developing in the minor principal-stress direction. Additionally, the peak generalized shear strain rapidly decreased in the first tension–torsion stage and then slowly decreased in the second. The principal-stress rotation space transformation matrix was introduced to modify the Lade–Duncan (L-D) criterion, and the criterion reliability was verified using the peak value of the soft rock deviatoric stress under different principal-stress directions. The modified L-D criterion considered the effects of both the principal-stress magnitude and direction. The results are of great significance for studying the influence of principal-stress direction and provide an important method to investigate the mechanical properties of rocks with complex stress paths comprehensively. [ABSTRACT FROM AUTHOR]

Translational rockslides caused by toe excavation are one of the commonly seen geohazards in mountainous regions due to line traffic construction. Quantifying their failure extension length (FEL) and travel distance is of significant interest as well as huge challenges in landslide hazard assessment. In this paper, a simple criterion is proposed for predicting these two factors based on the principles of rigid body limit equilibrium and kinetic energy theorem. Further, the proposed criterion is validated against the field observations and numerical results with a practical case of the Xinjianan landslide, a medium-sized translational rockslide that occurred in 2013 in Nanchuan District, Chongqing. The findings indicate that a tiny discrepancy can be found in FEL between the field observations and the proposed criteria, while this discrepancy could be considerable in travel distance between different methods. However, the relative discrepancies all fall within 20%, deemed acceptable. [ABSTRACT FROM AUTHOR]

To validate the feasibility of the microseismic monitoring in the early warning of rockburst in TBM excavation engineering, and to study the rockburst characteristics of surrounding rock, a newly developed microseismic(MS) monitoring system was employed in the Tianshan-Shengli tunnel to detect MS activities, and then to predict and warn the rockburst disasters. The system not only has the advantages of accuracy of artificial analysis, but also has the real-time analysis and early warning function of cloud service platform, of which positioning accuracy for MS events is about 5-10 m. The prediction criterion of rockburst risk level adopted multiple evaluation indexes such as energy, moment magnitude and quantity of MS events. It reveals that the evolution of maximum energy has a good positive correlation with that of maximum moment magnitude, through analyzing the monitored MS events. According to the field statistical results of rockburst information, the rockburst generally occurs two days after the rockmass is exposed from the tunnel boring machine (TBM) tail shield, which belongs to the delayed rockburst. The preliminary application cases indicate that the rockburst prediction and early warning based on MS monitoring can serve the safety construction of TBM excavation project well. [ABSTRACT FROM AUTHOR]

The continuous mechanical mining technology represents the development trend and significant transformation in excavation techniques for non-coal mines. It embodies a systematic and integrated innovation encompassing rock breaking methods, rock-breaking equipment, excavation methods, and excavation processes. Based on the current status of continuous mechanical mining technology in non-coal mines, this paper firstly outlines the technical characteristics of mechanical mining and summarizes the key scientific and technological challenges to be addressed. It provides an overview of various mechanical cutter-based rock-breaking methods, rock mass cuttability, and the development and application of continuous mechanical excavation technology. In response to the problems and challenges facing continuous mechanical mining technology in non-coal mines, this paper proposes a four-tier approach for technological breakthroughs; "process needs-technological breakthroughs-equipment research and development-engineering application." Research will be conducted across multiple aspects, including rock-breaking theory, key technologies, mining equipment, mining methods, and complete sets of processes, aiming to promote the development and advancement of safe, efficient, green, continuous, and intelligent non-explosive mechanical mining technologies and equipment for non-coal mines in China. [ABSTRACT FROM AUTHOR]

Investigations into the temporally evolving stress state below the base of excavations and underground structures are very scarce, in contrast to studies of horizontal earth pressures during the construction stage. Therefore in this work, the measured temporal response in terms of vertical and horizontal effective stresses and displacements below a tunnel slab at the base of an excavation located in a deep sensitive clay deposit is reported. In addition to the measured unloading response over time, the completeness of the site description and complementary measurements enables future benchmarking of numerical models at boundary and element level. Instrument clusters of earth pressure cells and piezometers were installed at three locations in one cross-section. The monitoring data allow the interpretation of effective stress paths and stress ratios, K = σ h ′ / σ v ′ , at soil element level covering the construction and the serviceability stages. The in situ stress ratios enable a unique comparison to prior laboratory studies of K during unloading. The data presented herein on the evolution of K corroborate, although approximately, previous studies at laboratory scale. Furthermore, at system level, the monitoring data reveal the intricate interplay between deformations resulting from excavation and pile driving. [ABSTRACT FROM AUTHOR]

Since Artificial ground Freezing (AGF) appeared in the 1880s in the mining sector in Europe, it has been used for various construction applications worldwide. In recent years, it has been increasingly popular in urban projects due to its versatility and applicability to complicated site conditions. So far, it has been used to stabilize substrata to nearly 1,000 m below the ground surface, which is considered not possible for many other ground improvement technologies. Due to the growth in field applications, the practice and theories related to AGF have become more mature in the most recent two decades. The improvement in understanding of this topic is a result of lessons that have been learned through numerous projects, as well as a variety of comprehensive studies that have been completed. This paper reviews the existing practice, the recent development on AGF and the challenges of AGF. [ABSTRACT FROM AUTHOR]

ABSTRACT Although considerable research has explored the static and seismic bearing capacity of strip footings on slopes or excavations, the influence of clay strength anisotropy on the bearing capacity of strip footing near excavations, specifically considering pseudo‐dynamic conditions, remains unexplored. This study used the finite element limit analysis (FELA) method to evaluate the impact of clay strength anisotropy on the seismic bearing capacity of strip footings. The effects of various dimensionless parameters on the bearing capacity were examined, which include shear wavelength, the setback distance ratio, vertical height ratio, soil strength ratio, soil strength heterogeneity, anisotropic ratio, and horizontal and vertical acceleration coefficients. Design charts were developed to compute the seismic bearing capacity of strip footings on nonhomogeneous and anisotropic excavations under pseudo‐static conditions. Furthermore, the effects of vertical acceleration coefficients and shear wavelength on the seismic bearing capacity of strip footing near excavation in nonhomogeneous and anisotropic soils were investigated. [ABSTRACT FROM AUTHOR]

Underground excavation by freezing method can ensure the safety of the surrounding structures. The influence of excavation of a connecting channel between two tunnels by freezing method on adjacent pipelines is studied in this paper. Combined with field measurement, numerical simulation, and theoretical analysis, the stress and deformation law of the whole process of channel excavation by freezing method is studied. Based on Euler–Bernoulli beam theory prediction, the influence of temperature field and excavation parameters on the longitudinal deformation of pipeline is analyzed. The results show that the excavation rate significantly affects the pipeline settlement, and the settlement surges when the excavation rate exceeds 1.0 m/d. At the same time, the thick frozen soil wall formed by low freezing temperatures enhances the supporting ability and effectively reduces the formation disturbance and settlement. The study focuses on the influence of connecting channel excavation on the pipelines under uniform formation conditions, and puts forward the evaluation method of pipeline safety to provide a theoretical reference for engineering practice. [ABSTRACT FROM AUTHOR]

This study aims to investigate the responses of shield tunnel structures subjected to disturbances caused by bilateral pit excavation, and it systematically reveals for the first time the impact mechanism of bilateral pit excavation on the distribution of perimeter pressure and deformation patterns of shield tunnels. Using a bilateral pit excavation project in Nanjing as a case study, this research establishes methods for calculating longitudinal displacement and circumferential pressure of tunnels under bilateral pit excavation conditions, employing the image source method for analysis. A refined three-ring segment model is developed, and the load structure method is used to analyze the impact of deep foundation excavation on the tunnel located between the two excavation sites. The results indicate that, compared to unilateral excavation, bilateral excavation significantly increases the perimeter pressure at the top and bottom of the tunnel, with a smaller increase in pressure at the arch waist. The deformation pattern is characterized by contraction at the top and bottom and expansion at the waist, forming a transverse elliptical deformation. The maximum vertical convergence values of the middle segment ring are 25.00 mm at the top and 25.88 mm at the bottom, with a vertical absolute convergence value of 44.5 mm and a convergence ratio (ΔDt/Dt) of 0.72%. As the foundation coefficient increases, the perimeter pressure at the top and bottom of the tunnel also increases. When the tunnel is closer to the foundation pits (Sp decreases), the perimeter pressure at the bottom of the tunnel increases. Conversely, as the distance between the two foundation pits (S) increases, the impact of excavation on the tunnel shifts from the upper part to the lower part, resulting in decreased upper perimeter pressure and increased lower perimeter pressure. The research findings provide important references for similar engineering projects. [ABSTRACT FROM AUTHOR]

Excavations in Israel of Byzantine and early Islamic sites have yielded some interesting gaming boards that are not always understood by the archaeologists who found them. Because they are organised in parallel rows of 'holes', most are presented as 'mancala' gameboards – which some may be, indeed; however, boards offering three or four rows of squares or depressions cannot reasonably be mancalas, nor can they be held as 'senet', the Egyptian game. So, what are they? Reviewing the relevant literature, this article will try in this article to disentangle these finds, the more so as they are often well dated to periods which have rarely been looked into. [ABSTRACT FROM AUTHOR]

The purpose of this paper is to capture the mechanical response of the support structure of deep excavation subject asymmetric load. A two-dimensional (2D) numerical analysis model was established by taking a pipe gallery deep excavation subject to asymmetric load as an example. The numerical analysis results were in good agreement with the measured data, thus verified the validity of the numerical model. On this basis, the stress and displacement of support structure caused by the change in foundation asymmetric load were studied. According to the numerical results, horizontal displacement of the diaphragm wall (DW) was dominant, and the maximum horizontal displacement of the DW was 7.54 mm when the deep excavation was completed. With the increase in asymmetric load, the left wall displacement continued to increase, while the displacement of the right DW continued to decrease, and the maximum horizontal wall displacement occurred near the excavation face. The DW was the main bending component, and the maximum wall bending moment when the deep excavation was completed was 173.5 kN·m. The maximum wall bending moment increased with the increase in asymmetric load, and the maximum wall bending moment on the left of the deep excavation was greater than that on the right. The inner support sustained the main component of axial force, with the axial force peaking at 1051.8 kN when the deep excavation was completed. The axial force of the inner support increased with increasing the asymmetric load, and the axial force of the second inner support was obviously greater than that of the first inner support. This research has a positive effect on the design and optimization of deep excavation support structure subject to asymmetric load on ground surface. [ABSTRACT FROM AUTHOR]

Only a few Swiss fossil localities are known globally and of which, the UNESCO World Heritage Site Monte San Giorgio, which extends from Switzerland into Italy, is the most important one. Following the discovery of the occurrence of articulated skeletons of marine reptiles in the local mines, large excavations were organized by Bernhard Peyer from the University of Zurich starting 1924. With this collection of articles, we commemorate the successful excavations and research, which initiated the publication of a series of monographies, mostly on the vertebrates but also on the invertebrates of this locality. Especially with the discovery of several remarkably similar Konservat-Lagerstätten in China, the discoveries from Monte San Giorgio gained global relevance. New methodologies such as computed tomography produced a wealth of new data, particularly on endocranial anatomy of several tetrapods. [ABSTRACT FROM AUTHOR]

This study takes a nearby foundation pit project of a high-speed railway in Yancheng City, Jiangsu Province as an example to investigate the impact of deep foundation pit projects on groundwater and the surrounding environment. Through on-site monitoring, in-situ testing, and numerical simulation, we conducted a comprehensive study of the impact of foundation pit projects on groundwater and the surrounding environment. The evolution of groundwater levels and surface displacement during the excavation of foundation pits was analyzed, and a method for measuring the permeability of target soil layers in situ was studied. The simulation of recharge under various soil conditions was performed, and the outcomes demonstrated the effective isolation of hydraulic connections between the interior and exterior of the foundation pit by the water-resistant curtain. Precipitation head and constant head recharging tests were employed to ascertain the actual permeability. The characteristic time method calculation exhibited remarkable efficiency and accuracy in determining the permeability coefficient of the recharging soil layer. Recharging phreatic and confined water layers has differing degrees of influence on surface deformation, with the impact of confined water layers requiring more time to stabilize. These findings contribute significantly to a more comprehensive understanding of the environmental repercussions associated with deep excavation projects, thereby enhancing safety and environmental protection measures in excavation construction practices. [ABSTRACT FROM AUTHOR]

This paper focuses on the performance of a braced deep excavation in soft soil based on field monitoring and numerical modeling. Laboratory tests were conducted to determine the soil parameters used in the modified Cam-Clay (MCC) model. Intelligent field monitoring means were adopted and a three-dimensional model was established. Spatial and temporal effects induced by the excavation are investigated for the deep-large foundation pit in soft soil. Deformation characteristics of the enclosure structure and the surrounding environment throughout the excavation process are presented. The behaviors of diaphragm walls, columns, the maximum wall deflection rate, ground surface settlement, and utility pipelines were focused on and investigated during the whole excavation process. Besides, the axial forces of the internal supports are analyzed. Based on the measured and simulated data, the following main conclusions were obtained: the numerical simulation results are in good agreement with the measured values, which proves the accuracy of the model parameters; the wall and the ground surface showed the maximum displacement increment at stage 9, which was a coupled product of the "creep effect" of the soft soil in Nanjing, China and the "depth effect" of the excavation; as the excavation progressed, the ground settlement changed from a "rising" to a "spoon-shaped" trend, dvm was measured between dvm = 0.0686%H and dvm = 0.1488%H; the rebound deformation curve of the pit bottom was corrugated, and the depth of disturbance of the pit bottom after the completion of soil unloading was 2-3 times the excavation depth; the closer the pipeline is to the corner of the pit, the less the excavation process will affect the settlement of the pipeline and the less the obvious pit corner effect will occur; the support strength of the buttress and the longest corner brace should be strengthened during the actual construction process to ensure the stability of the foundation deformation. [ABSTRACT FROM AUTHOR]

The application of steel strut force servo systems in deep excavation engineering is not widespread, and there is a notable scarcity of in-situ measured datasets. This presents a significant research gap in the field. Addressing this, our study introduces a valuable dataset and application scenarios, serving as a reference point for future research. The main objective of this study is to use machine learning (ML) methods for accurately predicting strut forces in steel supporting structures, a crucial aspect for the safety and stability of deep excavation projects. We employed five different ML methods: radial basis function neural network (RBFNN), back propagation neural network (BPNN), K-Nearest Neighbor (KNN), support vector machine (SVM), and random forest (RF), utilizing a dataset of 2208 measured points. These points included one output parameter (strut forces) and seven input parameters (vertical position of strut, plane position of strut, time, temperature, unit weight, cohesion, and internal frictional angle). The effectiveness of these methods was assessed using root mean square error (RMSE), correlation coefficient (R), and mean absolute error (MAE). Our findings indicate that the BPNN method outperforms others, with RMSE, R, and MAE values of 72.1 kN, 0.9931, and 57.4 kN, respectively, on the testing dataset. This study underscores the potential of ML methods in precisely predicting strut forces in deep excavation engineering, contributing to enhanced safety measures and project planning. [ABSTRACT FROM AUTHOR]

Solutions for unloading stress waves in the continuous medium are widely applied to analyze the transient effect of excavation unloading in deep-buried tunnel engineering. This paper explores a semianalytic model for studying dynamic stress adjustments during transient excavation unloading in deep underground tunnels. The model employs finite time steps and toroidal elements on temporal and spatial scales, utilizing an iterative algorithm for dynamic response calculation. Griffith and Mohr–Coulomb strength criteria are introduced to calculate the difference in the critical generalized additional stress. This difference classifies stress adjustment paths into crack–shear (crack first and then shear) and shear models (shear only). Updated discontinuous boundaries are considered in the cracked element. Investigating the effects of unloading duration and initial in situ stress on dynamic response, a stress release index is realized to quantify the dynamic stress adjustment. Shorter unloading durations lead to more pronounced stress fluctuations, and higher stress release aggregation results in smaller plastic zones. Positive correlations between initial in situ stress and response characteristics are observed, resembling triaxial unloading test results. The model proposed in this paper enhances the understanding of the failure mechanism in the unloading process for deep hard rocks in underground engineering. [ABSTRACT FROM AUTHOR]

Aiming at the condition of shield tunnel undercrossing the foundation of a pile group directly, using the settlement and inclination of the pile caps as the evaluation index, the reinforcing effect of the pregrouting of the soil around the pile foundation, the deep hole grouting behind the tunnel segment, and the combination of the two reinforcement methods are analyzed through three-dimensional numerical simulation. A reasonable reinforcement scheme is found and applied to practical engineering. The results show that for the pregrouting reinforcement of the soil around the pile, the optimal reinforcement scheme is to extend 0.5 m around the pile cap in the plane and vertically from the surroundings of the pile cap to 1/3 of the pile length below the bottom of the cap. When deep hole grouting reinforcement is adopted, larger reinforcement range and a certain range of radial reinforcement radius of tunnel section will result in a better effect of reinforcement. The combination of the two schemes is better than the single use of one. The practical application results show that the combined reinforcement scheme can effectively control the influence of shield tunnel excavation on the pile foundation of an elevated waiting hall. [ABSTRACT FROM AUTHOR]

Tunnel excavation breaks the original groundwater balance, leading to groundwater loss, wastage of water resources, and damage to the local ecological environment. The focus is on effectively predicting the impact of unexcavated tunnels on the groundwater environment and using this prediction to guide construction. This study established an evaluation system by analyzing factors such as natural geography, engineering geology and hydrogeology at the tunnel site. The sensitivity evaluation model of groundwater environment affected by tunnel excavation was established by combining the Analytic Hierarchy Process (AHP) and fuzzy mathematics. The tunnel site was evaluated based on the Wanshishan tunnel on the southern extension of Xiamen rail line 3. Given that previous research primarily provided an overall assessment of the environmental impact of tunnels, while the impact on the groundwater environment varied due to different regional geological conditions and special features such as fault fracture zones, this study evaluated different mileage sections along the tunnel excavation route based on surrounding rock grades. The study found that, for section K5 + 540, the comprehensive evaluation index was 2. 864 8, indicating a sensitivity level between average and moderately strong. Overall, the groundwater environment of the whole tunnel site was categorized into four levels: moderately Validation through field geophysical exploration and other assessment models confirmed the reliability and rationality of the findings, providing a valuable reference for the design of water control and drainage schemes in engineering projects. [ABSTRACT FROM AUTHOR]

Reasonable support force is crucial for the stability of the excavation face in sandy pebble tunnels. By utilizing the existing failure mode of the logarithmic spiral curve, this study combined the collapse arch model with the limit analysis method to establish a failure model for the excavation face in sandy pebble tunnels. A calculation method for the ultimate supporting force applicable to the excavation face of sandy pebble tunnels was also proposed. Then, the theoretical analysis presented in this paper was compared with numerical simulation and existing theories to determine the failure areas under different internal friction angles and cohesion values. Finally, the excavation face stability of a shield tunnel in Beijing was analyzed using theoretical analysis and numerical simulation methods. The results showed that the analytical solution proposed in this paper was in good agreement with the limit supporting force derived from existing research, with convenient and accurate calculations. The limit supporting force decreased nonlinearly with the increase of the internal friction angle, and was more sensitive to changes in the friction angle when the angle was small. The limit supporting force decreased approximately linearly with the increase in cohesion. When the burial depth was small, it had a more significant impact on the limit supporting force. When the C / D ratio exceeded 1. 0, the increase of the burial depth of the tunnel had no obvious effect on the limit supporting force, and the friction angle had a very significant effect on the failure area. With the increase of internal friction angle, the failure area decreased significantly. Cohesion had little impact on the failure area, i. e., the size of the energy dissipation surface remained nearly unchanged under different cohesion values. For the shield tunnel in Beijing, the calculation based on the limit analysis method optimized the collapse range and shape, making the failure mode more reasonable while increasing the failure range, achieving excellent engineering application results. [ABSTRACT FROM AUTHOR]

Compared with the traditional "earth pressure balance" tunneling mode, the "air-pressure assisted" mode of shield tunneling has a more complex mechanism for maintaining excavation face balance, with significant differences in ground deformation and tunneling parameters compared to conventional full-chamber earth pressure balance tunneling mode. In order to quantitatively assess the stability of the excavation face under the air-pressure assisted tunneling mode and to determine a reasonable air-pressure setting, this study proposed an evaluation method for overall excavation face stability in the air-pressure assisted mode by using the limit equilibrium method, considering the spatial surface characteristics of the slip surface. Based on the Krabbe formula, considering the layering of the strata and the influence of groundwater, the formula for calculating gas loss was modified. In addition, a comparative tunneling test was conducted under different tunneling modes in the same strata condition, comparing the overall stability, air-pressure loss, ground settlement and tunneling parameters of the excavation face. The results showed that: according to the proposed overall stability evaluation method and the gas loss calculation method, the experimental section of this project met the overall stability requirements for air-pressure assisted tunneling. The selected air compressor had sufficient power for maintaining air-pressure stability in the strata, and the air-pressure setting met the requirements of engineering safety. Compared to the full-chamber earth pressure balance mode, the total thrust and cutterhead torque in the air-pressure assisted mode were reduced by 35% and 44%, respectively, while the advancing speed increased by 173% and energy consumption decreased by 66%. The air-pressure assisted tunneling mode resulted in a higher ground loss rate and relatively larger surface settlement. [ABSTRACT FROM AUTHOR]

This research advances the understanding of deep excavation impacts by integrating a refined Finite Element Method (FEM) analysis with empirical data, specifically examining the behavior of retaining structures in urban environments. Unlike prior studies that predominantly relied on theoretical models, this paper combines FEM with statistical methods, particularly ANOVA, to identify critical factors affecting the performance of barrette walls during excavation. The primary objective of this study is to analyze the deformation and force behaviors at various depths, thereby enhancing the predictive capabilities of existing models. The findings highlight significant variations in horizontal displacements (Uy) and vertical displacements (Uz) across different excavation stages, with notable mean differences ranging from 0.000529420 m to 0.000700240 m for Uy and -0.017563652 m for Uz. Axial forces (N1) also show significant increases with depth, reaching a mean difference of 516.137991 kN/m. These results underscore the importance of adaptive design strategies in deep excavation projects. However, the study is limited by the specific geological conditions and the scope of empirical data used for model validation. Practical recommendations include enhancing real-time monitoring systems and applying refined methodologies. [ABSTRACT FROM AUTHOR]

A foundation pit's excavation area, which is determined by its radius in a circular foundation pit, exerts a considerable influence on the pit's behavior. Using a full-scale experiment on a circular foundation pit retained by a prefabricated recyclable supporting structure (PRSS), this study develops a series of axisymmetric numerical models to systematically investigate the influence of excavation radius on the pit's deformation, stress, and stability. Furthermore, simulation results from axisymmetric models are compared with those from plane strain models to illustrate the influence mechanism. The results show that at a given excavation depth, the deflection and bending moments of the supporting piles, the earth pressure on the non-excavation side, and ground surface settlement increase with the enlarged excavation radius, but the increase rate progressively decreases. However, the foundation pit's safety factor decreases with an increasing excavation radius and gradually stabilizes. When the excavation radius exceeds 50 m, its influence on the foundation pit's behavior significantly diminishes. The axisymmetric model results closely approximate those from the plane strain models, suggesting that the spatial arching effects of the circular foundation pit can be disregarded. [ABSTRACT FROM AUTHOR]

In the simulation of foundation pit excavation, the traditional element birth–death method commonly used tends to encounter issues such as uncoordinated deformation and changes in the constitutive model, affecting the accuracy of the prediction results. To address these issues, this study proposes the use of element tracking. By duplicating elements for temporary supports or structures requiring changes in material properties and appropriately activating or deactivating them at the right moments, the simulation of the foundation pit excavation process can be achieved more precisely. Using the construction process of the Tangxi Passenger Transport Station's comprehensive transportation hub foundation pit as an example, this study applied the proposed simulation method and compared the results with actual measurements, demonstrating its effectiveness. This research offers a more accurate approach for simulating foundation pit excavation and provides a reference for similar numerical simulation problems. [ABSTRACT FROM AUTHOR]

Large landslides can involve the multiple failures of regional slopes. To understand the effect of lateral thrust caused by the failure of one slope on its surroundings, the failures of two adjacent highway slopes in Guangdong Province, China, were investigated in detail. The interactive failure processes and landslide morphological characteristics of the two slopes were first analyzed based on the on-site investigation. Then, a plane mechanical model of a large-scale slope was established to evaluate the significant influence of the lateral thrust generated by the west slope acting on the east excavated slope. Furthermore, the extrusion effect of the west slope was modelled under the alternate excavation disturbance and rainfall by transferring the thrust forces onto the interface elements, and the induced failure mechanism and instability mode of the east slope under lateral thrust were reproduced numerically. The results show that the compression-shear failure occurred at the middle and rear slope bodies because of the lateral thrust, which led to the formation of a thrust landslide and the final instability of the east slope. [ABSTRACT FROM AUTHOR]

Grazing livestock in uplands was a widespread practice in late Medieval and early modern Europe, but there can be uncertainty about the date and function of archaeological sites associated with herding. This paper reviews fieldwork on such sites in northern and northwestern Europe and reports on the excavation of a hut and enclosure in the mountains of southwestern Ireland. The hut was found to have been built in the 16th or 17th centuries a.d. and was probably used to oversee dairy animals (likely cows). The enclosure was dated to the early 18th or early–mid-19th century a.d. and is more likely associated with goat milking. The excavations demonstrate that construction dates can be obtained for pastoral sites in uplands of northwestern Europe. Furthermore, with careful reading of features in the surrounding landscape and consideration of documentary and ethnographic evidence, fieldwork can help determine the nature of pastoral economies over time. [ABSTRACT FROM AUTHOR]

Reality Capturing – Innovative use of drones for planning, documentation and preservation of evidence in specialist civil engineering The GoWest commercial quarter – a future‐orientated, sustainable commercial location is currently being built on the site of the former Reemtsma cigarette factory in Berlin‐Schmargendorf. On an area of approx. 50,000 m2, 12 commercial courtyards with up to 6 upper floors are being built. The entire quarter will have a full 3‐storey basement. The 14 metre deep excavation pit is secured with a diaphragm wall in conjunction with a supporting beam shoring in front of it. A digital 3D model of the construction site created using reality capturing is being used to plan the excavation pit and document the construction work. The possible applications of such a model are presented in this article. [ABSTRACT FROM AUTHOR]

Report of the working group for recommendations on excavations: current and future works The working group for excavations of the German Geotechnical Society (DGGT) has since 1968 regularly published recommendations for analysis, design and construction of excavations. The present report provides an overview of current works of the working group. In the reporting period, the focus has been on the participation in commenting on the drafts of the new Eurocode 7 and the design of struts. Further points to discuss were a supplement to Eurocode 0 and questions how to design soldier pile walls with a supporting wedge. [ABSTRACT FROM AUTHOR]

Verification of sufficient anchor lengths with the FEM for double back anchoring The article analyses the necessity of the minimum length of grouted anchors for excavation walls. The required verification of a sufficient anchor length is to be carried out according to current standards with the verification of stability in the lower failure plane. Here, calculations using the finite element method (FEM) are not intended. The future Europe‐wide standardisation will foreseeably lead to an increased use of the FEM for stability verifications, without all details of these verifications having already been defined. The verification of the sufficient anchor length of single back‐anchored excavation walls using the FEM has already been analysed. A stepwise reduction of the shear parameters of the soil was identified as the most suitable method. However, this does not correspond to the procedure specified in the current German standard of a comparison of the existing anchor force with a possible anchor force from an investigation of the lower failure plane. The article uses an example to investigate whether the method of stepwise reducing the shear parameters of the soil also leads to plausible results for double‐anchored excavation walls. Here, the determination of the failure mechanisms in the subsoil is of high importance. One question is whether a variation of both anchor lengths results in different failure mechanisms, as it is the case applying classic methods. [ABSTRACT FROM AUTHOR]

To solve the construction difficulties of the rectangular pipe jacking in the boulder area in a complex geological environment, based on the pipe jacking project of the pedestrian passage of the Qieye Ridge in the transformation project of the Harbor Avenue in Xiangzhou District, Zhuhai City, Guangdong Province, the construction risks encountered by boulders during pipe jacking excavation were analyzed in conjunction with the actual engineering conditions. According to the size, shape, and distribution of the boulders, the advantages and disadvantages of different construction schemes when encountering boulders during pipe jacking construction process were discussed, and the engineering costs, environmental impact, construction difficulty, safety, and applicability of five obstacle handling schemes were systematically compared and analyzed. The best handling method suitable for this case project was selected to achieve the purpose of improving efficiency, reducing costs, and avoiding risks. The case project adopted the pre-treatment construction technology of the down-the-hole hammer in the casing technology to crush and remove the boulders, and successfully restored the pipe jacking excavation construction. This solution could ensure efficient, safe, and orderly clearance work and had excellent application effects. [ABSTRACT FROM AUTHOR]

In order to investigate the stress and strain state of the surrounding rock and the effect of supporting structure of the deep buried tunnel through the fault zone in mountainous area, taking Lianfeng Mountain Tunnel Project as the research background, based on ABAQUS large-scale finite element numerical computation program, the mechanics calculation model of the construction of the deep buried tunnel through the fault zone was established, and the change rule of the structural stress state and the horizontal and vertical settlement rule of the mountain after the tunnel excavation and lining were studied. The results showed that the settlement in the fault zone during tunnel excavation was much larger than that in the normal rock body; the stress difference between the surrounding rock and the peripheral mountain body at the fault zone was larger, and the stress difference at the junction with the normal mountain body was larger; the settlement caused by tunnel excavation affected the range of 50 m, and the settlement at the center of the twin tunnels increased with the increase of vertical height; the excavation of the second tunnel in the construction of the twin tunnels caused the increase of the strain of the first tunnel. [ABSTRACT FROM AUTHOR]

In a recent work, the authors demonstrated the merits of the diametrical core deformation technique (DCDT) for stress determination at an excavation face. An analytical model was developed and verified with laboratory tests. This paper aims to validate the DCDT in the field using a well-documented case study from a Canadian underground mine. Rock cores are extracted from the floor of a footwall drive 1000 m below surface for the purpose of estimating stress magnitude and orientation. The DCDT is applied to the extracted cores and the state of stress in the drift floor is estimated. On the other hand, a mine wide FLAC3D model was developed using the geomechanical data and in situ stress regime obtained from a previous study. The model is a pared-down version of a comprehensive FLAC3D mine wide model that simulates past mine-and-fill sequence and was calibrated with various burst criteria and recorded mining-induced seismic events. A comparison of FLAC3D and DCDT in terms of floor stress estimates and orientation shows good agreement. The DCDT could be used as a ground control tool to help detect stress-related ground control issues. Highlights: Extraction of rock cores from a drift floor 1000 m below surface for the purpose of stress estimation. Application of diametrical core deformation technique (DCDT) to estimate the biaxial state of stress—magnitude and orientation—in the floor. Development of a mine-wide 3D numerical model using geomechanical data and in situ stress regime. Validation of DCDT by comparison of stress orientation and magnitude estimates with calibrated numerical model. The comparison shows good agreement. [ABSTRACT FROM AUTHOR]

The article reports on the discovery of megalithic tombs in the Ahlen-Falkenberger Moor in Germany. As part of a research project, three passage graves were examined, in which well-preserved elements of the burial constructions were found. Various burial activities of the Funnel Beaker Culture could be identified and dated. The excavations and scientific analyses provide insights into the complex architecture and use, as well as the environmental development around the megalithic grave Wanna 1592. Various identifiable phases are presented, including the construction of the monument, the burial level and activities in the entrance area, human impacts in the surroundings, destruction and sealing of the chamber, disturbance of the outer stone packing, and the disappearance in the bog. The text describes archaeological finds and soil analyses at a burial mound in Wanna. Two deposits were found, one outside the chamber and one inside the chamber, which can be dated to the Late Bronze Age. Ceramic fragments and flint artifacts were also discovered. The soil analyses show that the burial mound was built on a Luvisol surface, which has transformed into a Podsol outside the mound. Micro-morphological analyses were also conducted, revealing further details about the soil development. The article describes the results of an investigation of megalithic graves in Ahlen-Falkenberg, Denmark. It is noted that the graves have similar construction features and fit into the regional distribution of passage graves. It is speculated that the graves were built in a continuous working process, with social aspects playing a role in the choice and construction of the megaliths. The graves were likely built within a short construction period, and the materials came from the immediate surroundings. The graves were used during the Early Neolithic period and later abandoned in the Late Neolithic period. In Schleswig-Holstein, the entrance of a dolmen was destroyed in the Late Neolithic period. With the continuous rise of the bog water level, Wanna 1591 and 1592 were situated in wet contexts at the end of the Neolithic period, and Wanna 1588 at the latest in the EBA. Human activities increasingly focused on the higher Ahlen Geests, which included landscape clearances. The last practices were carried out during the transition from the Bronze Age to the Iron Age in Wanna 1588, when pottery vessels were placed between two capstones. In conclusion, it can be said that the megalithic landscape of Ahlen-Falkenberg has been well-preserved thanks to peat growth over the past thousands of years, providing insights into the original building elements and techniques, as well as burial practices of the FBC megaliths in the Neolithic period. Further excavations are necessary to clarify open questions. [Extracted from the article]

Excavation-induced soil arching is a key factor influencing the responses of the ground and underlying structures. This soil arching below an excavation base is defined as downward soil arching in comparison with that above a trapdoor or tunnel, featured with the downward developing direction. To recognize and assess the downward soil arching, two centrifuge tests in the plane-strain condition were conducted in the dense and loose sand. Variations of Earth pressure, basal heave, and shear wave velocity below the excavation base were observed, and the influence of the relative density was also investigated. The test results indicated the existence of differential deformation and stress transfer below the excavation base, and the downward soil arching is confirmed. The contributions of the downward soil arching to the restriction of the excavation-induced stress release and the ground response were found. Further, the boundary of the loosened zone and the width of the arch foot were determined in the dense and loose sand, respectively. In addition, the arched-type basal heave and stress-related shear wave velocity were observed. The significant ground heave and reduction of the shear wave velocity were found within the loosened zone. [ABSTRACT FROM AUTHOR]

After excavation of tunnels in interbedded surrounding rock, accidents such as rock peeling and arch crown collapse are prone to happen. In response to this issue, we first established an analysis model for the excavation of the interbedded surrounding rock tunnel through theoretical analysis, proposed corresponding failure criteria, and analyzed the reasons for the easy failure of the interbedded tunnel support structure based on the concept of principal stress difference. We also created interfaces in FLAC3D (version 6.0) software to restore the actual interbedded interface, verifying the effectiveness of principal stress difference in analyzing the deformation characteristics of the tunnel. Then, the instability forms of the interbedded surrounding rock tunnel were divided into two types, and effective support methods for the corresponding instability forms were proposed. Finally, based on the analysis results of the study, support was provided for the collapsed tunnel on site. A grouting large pipe shed was put to innovative use to support the tunnel arch waist, stabilizing the surrounding rock that is prone to shear slip and fracture at the upper part of the arch waist. The results indicate that the surrounding rock control effect is good. This study has a good reference value for on-site rapid construction and support design, and is of great significance for the instability prevention and control of interbedded surrounding rock tunnels. [ABSTRACT FROM AUTHOR]

A new grouting technique, double-row capsule grouting (DRCG), has been developed and implemented in practice. This grouting technique could effectively mitigate excavation-induced tunnel movement and ensure the serviceability of metro lines. However, its control mechanism and the factors that influence its performance are not fully understood. Based on a case history that utilized capsule grouting the precision of the numerical model is validated. Parametric studies are conducted to investigate the influence of the grouting location and volume on the tunnel deformation, bending moment, restoration ratio, and shear strain of the soil. In addition, a comprehensive comparison between the conventional grouting technique and DRCG is performed to illustrate the control mechanism of this innovative technique. The results could contribute to a better understanding of the factors that impact the performance of DRCG and an optimal application of DRCG, which facilitates its efficient implementation and further development in engineering. [ABSTRACT FROM AUTHOR]

Accurate prediction of excavation deformation and stress affects the safety of excavation engineering and the surrounding environment. However, the traditional calculation method ignores the influence of soil shear action and its nonlinear deformation characteristics. Therefore, this paper proposed a coupled analytical method for braced excavation considering the continuity of soil deformation and nonlinear pile–soil interaction. A nonlinear Pasternak two-parameter foundation model was developed based on the Pasternak foundation model and nonlinear p–y curves. The control differential equations for the excavation in the critical and embedded sections were derived. Also, the numerical solutions of excavation deformation and force under different boundary conditions were obtained by the finite difference method and Newton's iteration method. Further, the excavation calculation procedure considering the construction process and nonhomogeneity of soil was suggested. Through finite-element (FE) and engineering case analyses, the traditional calculation method overestimated the excavation deformation and internal force, while the proposed methods were consistent with the measured results. Finally, the effects of soil shear stiffness and initial foundation reaction modulus on the excavation were discussed, and we found that the two parameters had more significant impact on the wall bending moment than displacement. The results provide some reference for the design calculation of braced excavation. [ABSTRACT FROM AUTHOR]

Copyright of China Mining Magazine is the property of China Mining Magazine Co., Ltd. and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Excavating super-large-span tunnels in soft rock masses presents significant challenges. To ensure safety, the sequential excavation method is commonly adopted. It utilizes internal temporary supports to spatially partition the tunnel face and divide the excavation into multiple stages. However, these internal supports generally impose spatial constraints, limiting the use of large-scale excavation equipment and reducing construction efficiency. To address this constraint, this study adopts the "Shed-frame" principle to explore the feasibility of an innovative support system, which aims to replace internal supports with prestressed anchor cables and thus provide a more spacious working space with fewer internal obstructions. To evaluate its effectiveness, a field case involving the excavation of a 24-m span tunnel in soft rock is presented, and an analysis of extensive field data is conducted to study the deformation characteristics of the surrounding rock and the mechanical behavior of the support system. The results revealed that prestressed anchor cables integrated the initial support with the shed, creating an effective "shed-frame" system, which successively maintained tunnel deformation and frame stress levels within safe regulatory bounds. Moreover, the prestressed anchor cables bolstered the surrounding rock effectively and reduced the excavation-induced disturbance zone significantly. In summary, the proposed support system balances construction efficiency and safety. These field experiences may offer valuable insights into the popularization and further development of prestressed anchor cable support systems. [ABSTRACT FROM AUTHOR]

The tunnel boring machine (TBM) is typically used in hard-rock tunnel excavation. Owing to the unsatisfactory adaptability of TBM to the surrounding rock, when crossing high-strength and high-wear strata, the TBM can easily cause defects, such as abnormal wear on cutters and overload damage to bearings, thus affecting the construction efficiency and cost. Therefore, high-pressure waterjet technology should be applied to assist in rock breaking for efficient TBM tunneling. In this study, the effects of water pressure, nozzle diameter, and nozzle speed on cutting are investigated via laboratory experiments of cutting hard rock using high-pressure waterjets. The penetration performance of the TBM under different water pressures is investigated via a field industrial penetration test. The results show that high-pressure waterjets are highly efficient for rock breaking and are suitable for industrial applications, as they can accommodate the advancing speed of the TBM and achieve high-efficiency rock breaking. However, during the operation of high-pressure waterjets, the ambient temperature and waterjet temperature in the tunnel increase significantly, which weakens the cooling effect of the cutterhead and decreases the construction efficiency of the TBM. Therefore, temperature control and cooling measures for high-pressure waterjets during their long-term operation must be identified. This study provides a useful reference for the design and construction of high-pressure water-jet-assisted cutterheads for breaking road headers. [ABSTRACT FROM AUTHOR]

In the western mining region, weakly cemented rock layers above the coal seams often lead to frequent catastrophic accidents during mining due to their instability. To address this, this paper analyzes the movement characteristics of surrounding rock in the recovery roadway and the effectiveness of from nearby large coal pillar roadways. A mechanical model for the failure of weakly cemented roadways was established, and numerical simulations were used to verify the feasibility of leaving small coal pillars along soft, thick coal seams. Additionally, existing measurements were used to evaluate the impact of leaving small coal pillars on the deformation of the surrounding rock in the recovery roadway. The results show that after changing the coal pillar retention to 5 m in the 130,205 working face of the Yangchangwan mining area, the roadway is in a low-stress zone, with minimal surrounding rock deformation, meeting safety requirements for production. [ABSTRACT FROM AUTHOR]