Development of the Block 37 in downtown Chicago included construction of a multi-story building and two tunnel connections, the State and Dearborn Street Connections. During excavation of the ...Dearborn Connection, the freight tunnel underlying the excavation zone developed a 5.2-m-long longitudinal crack at its crown and walls. Two Three-dimensional finite element analyses were conducted to study the impact of the Block 37 building and Dearborn Connection excavations on the freight tunnel that cracked during excavation. The pre-construction axial forces, bending moments and internal stresses computed based on long term loads were used to define the loading condition of the freight tunnel before construction. The results of the two finite element analyses were used to compute the construction-induced axial forces, bending moments and the corresponding internal stresses imposed on the segment of the freight tunnel concrete liner that was cracked, explain the cracking of the tunnel and assess the validity of the pre-construction loads at the tunnel liner.
New Studies in the Archaeology of Jerusalem and its Region is an annual journal that presents studies relating to recent findings in Jerusalem and its Region. The journal appears every October in ...conjunction with the conference, where the studies are presented. The Journal is a collaboration of the Israel Antiquities Authority, Tel Aviv University and the Hebrew University of Jerusalem. To date, 14 volumes have been published. The current issue presents studies on the following topics: the Walls of Jerusalem in the Iron Age; the Royal Landscape of Jerusalem; the Temple Mount Walls and Gates; Water in and to Jerusalem; Cultural Connections in the Art of Jerusalem and its Vicinity; and Islamic Jerusalem and Judea. In addition, several archaeological reports were included in the volume: Nahal Arza, the Gloria Hotel and a detailed typological study on lime-based plasters.
The time of arrival of people in Australia is an unresolved question. It is relevant to debates about when modern humans first dispersed out of Africa and when their descendants incorporated genetic ...material from Neanderthals, Denisovans and possibly other hominins. Humans have also been implicated in the extinction of Australia's megafauna. Here we report the results of new excavations conducted at Madjedbebe, a rock shelter in northern Australia. Artefacts in primary depositional context are concentrated in three dense bands, with the stratigraphic integrity of the deposit demonstrated by artefact refits and by optical dating and other analyses of the sediments. Human occupation began around 65,000 years ago, with a distinctive stone tool assemblage including grinding stones, ground ochres, reflective additives and ground-edge hatchet heads. This evidence sets a new minimum age for the arrival of humans in Australia, the dispersal of modern humans out of Africa, and the subsequent interactions of modern humans with Neanderthals and Denisovans.
This paper presents the construction of a large-scale basement excavation adjacent to the two running metro tunnels in Nanjing silty clay. To investigate the influences of excavation on existing ...tunnels, a numerical modelling was carried out to predict the possible deformation of tunnels before construction. Then, referring to the obtained numerical results, a targeted monitoring program was proposed and comprehensive field monitoring was performed to monitor the deep excavation and tunnels response over four years. The monitoring items include the diaphragm wall lateral deflection, the tunnel crown settlement, the springline horizontal displacement, the diameter convergence and the opening width of the segment joint. Based on monitoring results, the evolution of tunnels deformation was analysed, and the safety of tunnel structures was evaluated. According to the evaluation results, micro-disturbance grouting was proposed and adopted to correct the deformed tunnel, and the treatment effectiveness was evaluated. The results indicate that the evolution of tunnel crown settlement, springline horizontal displacement and diameter convergence can be divided into slow growth, rapid growth and stable growth stages, and they correspond to the pre-excavation, main excavation and post-excavation stages of deep excavation respectively. Based on the simple beam principle, the settlement range of tunnel can be taken two times the distance between the monitoring section with the maximum settlement and the section with the settlement of 0. In the process of micro-disturbance grouting treatment, the deformed tunnel goes through a correction stage and a rebound stage respectively, and the additional deformation induced by adjacent excavation is well corrected by micro-disturbance grouting.
•An integrated parameter prediction framework is developed to assist TBM operation.•TBM operational parameters, thrust, cutterhead torque and advance rate are estimated.•Four machine learning ...algorithms, SVR, RF, BP-ANN, GBDT are applied.•Random forests-based feature importance technique is implemented to select inputs.•TBM working phases extraction is conductive for capturing data characteristics.
The adjustment of TBM operational parameters with regard to different strata significantly affects the safety, time and cost in tunnel construction. To assist TBM operation, this paper develops an integrated parameter prediction framework for hard rock tunneling based on combined pre-construction geological information and TBM operational data. The method involves three steps: extraction of TBM working phases based on operational data, selection of input feature from geological information and operational data, and development of prediction model using four machine learning algorithms. The proposed framework has been demonstrated and verified by applying it to a water conveyance tunnel project in China. The results show that the proposed framework performs well in predicting three critical TBM operational parameters, thrust, cutterhead torque and net advance rate, with the determination coefficient R2 all exceeding 0.8. A comparison study proves that the introduced TBM working phase extraction method is conductive for capturing data characteristics and making predictions, because it unveils the complex rock-machine interaction information underlying the operational data.
The stability of circular excavations in clay shales is a key issue in the drilling and tunnelling industries as well as in the field of deep geological waste storage. A large body of experimental ...evidence indicates that the damaged zone around these cavities is influenced by strong mechanical anisotropy induced by the layered material structure. The vast majority of numerical models adopted to date to analyse the stability of openings in layered rocks have been based on continuum mechanics principles using classic shear failure theory for elasto-plastic materials. However, a number of experimental observations demonstrate that clay shales may fail in a brittle manner under low-confinement conditions such as those characterizing the near-field of the excavation. Therefore, an alternative numerical approach based on non-linear fracture mechanics principles and the discrete element method is adopted to gain new insight into the failure process of this class of geomaterials. In order to account for the influence of clay shale microstructure on its mechanical behaviour a newly developed approach to capture the anisotropy of strength is proposed. With this numerical approach, the cohesive strength parameters of the fracture model are assumed to be a function of the relative orientation between the element bonds and the layering orientation. The effectiveness of the numerical technique is quantitatively demonstrated by simulating standard rock mechanics tests on an indurated claystone, namely Opalinus Clay. Emergent strength and deformation properties, together with the simulated fracture mechanisms, are shown to be in good agreement with experimental observations. The modelling technique is then applied to the simulation of the Excavation Damaged Zone (EDZ) around a circular tunnel in horizontally bedded Opalinus Clay. The simulated fracturing process is mainly discussed in the context of the damage mechanisms observed at the Mont Terri URL. Furthermore, the influence of in situ stress on resulting EDZ geometry is analysed together with possible implications for ground support and tunnel constructability. Modelling results highlight the importance of shear strength mobilization along bedding planes in controlling the EDZ formation process. In particular, slippage of bedding planes is shown to cause rock mass deconfinement which in turn promotes brittle failure processes in the form of spalling. The numerical technique is currently limited to two-dimensional analyses without any thermo-hydro-mechanical coupling.
•A new approach to model strength anisotropy with FEM/DEM was developed.•The proposed method was validated by simulating rock mechanics tests on Opalinus Clay.•The evolution of damage around a circular tunnel was investigated.•The importance of delamination of bedding planes in triggering brittle failure was shown.
•Investigation and monitoring methods for landslide caused by tunneling are provided.•The reason for extrusion deformation of lining is only the increasing external forces.•The necessary ...reinforcement measures for tunneling in landslide are proposed.
Deformations of tunnels and slopes are often induced by tunneling in landslide areas. However, the reinforcement measures for controlling slope deformation may be ineffective for preventing slope sliding, owing to the lack of a clear understanding regarding the slope failure and tunnel deformation modes. This study aimed to monitor the entire construction process of the Xiamaixi tunnel, to analyze the deformation characteristics of the lining and failure mode of the slope, and to evaluate the effectiveness of reinforcement measures. The deformation characteristics of the Xiamaixi tunnel and slope were studied in four stages (normal excavation, suspended excavation, continued excavation, and reinforcement and excavation) with reference to field investigations, geological boreholes, measurements, and numerical simulations. The maximum cumulative monitored deformations of the vault settlement and slope were 39.2 mm and 170.9 mm, respectively. The range of the landslide was 60 m along the tunnel axial direction, and 46 m along the tunnel transverse direction. It was found that a tunnel whose vault is located in a potential landslide area may be forced to extrude, but not slip, and that the extrusion deformation of the lining is only caused by the increasing external forces. Reinforcement measures (and other temporary supporting measures) were presented for the slope and auxiliary construction, and their effectiveness was assessed. Finally, the lessons learned were summarized, providing insights for preventing future similar incidents from reoccurring.
This volume presents a comprehensive review of palaeoenvironmental evidence and its incorporation with landscape archaeology from across the Mediterranean. A fundamental aim of this book is to bridge ...the intellectual and methodological gaps between those with a background in archaeology and ancient history, and those who work in the palaeoenvironmental sciences. The volume also aims to provide archaeologists and landscape historians with a comprehensive overview of recent palaeoenvironmental research across the Mediterranean, and also to consider ways in which this type of research can be integrated with what might be considered 'mainstream' or 'cultural' archaeology. This volume takes a thematic approach, assessing the ways in which environmental evidence is employed in different landscape types. It presents analyses of how people have interacted with soils and vegetation, and revisits the key questions of human culpability in the creation of so-called degraded landscapes in the Mediterranean. It covers chronological periods from the Early Neolithic to the end of the Roman period.
Complex geological conditions and/or inappropriate shield tunnel boring machine (TBM) operation can significantly degrade both the excavation and safety of tunnel construction. In recent years, the ...excavation behaviour of shield TBMs has been a popular topic in the literature given the large volume of data automatically collected by modern shields. These datasets provide an excellent opportunity to apply advanced data analysis techniques to improve predictions of shield tunnelling excavation behaviour. In this study, a framework to develop machine learning (ML)-based regression models for predicting the behaviour of an earth pressure balance (EPB) shield machine using tunnelling parameters is proposed. The feasibility of four ML algorithms, namely Linear Regression (LR), Decision Tree Regression (DTR), Support Vector Regression (SVR), and Gradient Boosting Regression (GBR), to predict EPB shield excavation behaviour is explored through their application to a recent tunnelling case history in sandy soils. The results show that the misestimates were primarily attributed to a reduction of screw conveyor rotational speed (SCRS), induced by a lower injection volume, the artificial manipulation of penetration rate (PR), the local variations of total jacking load, and the use of ‘breakout’ cutterwheel torque (CT). The GBR model provided the best performance, while LR often performs the worst due to its inability to handle highly nonlinear relationships. DTR prevented the overfitting problem by using a lower max depth parameter towards sacrificing its accuracy. The performance of SVR was seriously affected by loss functions. The proposed optimisation scheme that prevents the over-smoothing problem during the STL decomposition elevates further the prediction accuracy.
The construction of an underground opening leads to changes in the in situ stress regime surrounding the excavation. The opening influences the rock mass owing to the redistribution of the stresses ...and results in the disturbance of the surrounding ground. At great depths, massive to slightly or moderately fractured rock masses are usually encountered, and under high stresses, they are more likely to behave in a brittle manner during an excavation. While constitutive models have been developed and proposed for the numerical simulation of such excavations using continuum mechanics, this brittle response cannot be simulated accurately enough, since the material behaviour is governed by fracture initiation and propagation. On the contrary, discontinuum approaches are more suitable in such cases. For the purposes of this paper, the brittle behaviour of hard, massive rock masses and the associated spalling failure mechanisms were simulated by employing a finite–discrete element method (FDEM) approach using Irazu software. The generated numerical model was utilized to replicate field conditions based on the observations at the Atomic Energy of Canada Limited (AECL) Underground Research Laboratory (URL) test tunnel located in Pinawa, Manitoba, Canada. The model results are compared with field observation data to explicitly demonstrate the suitability of the method.
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