AbstractThe ground-improvement technique is commonly used to restrain the wall displacement induced by excavation and resist the basal heave for deep excavations in soft clays. In this paper, a ...three-dimensional finite-element stability analysis was conducted to evaluate the effect of different ground-improvement properties and patterns on enhancing the factor of safety against basal heave in deep excavations. The results showed that a large downward movement of soil behind the wall could induce a large upward movement below the excavation, which is mainly resisted by the weight of the interior soil mass and the frictional resistance acting on the contact surface area between the wall and the soil inside the excavation. When the ground improvement was not contacted with the wall, the failure initially occurred on the wall interface, causing the soil inside the excavation to move upward along with the ground improvement, which resulted in an insignificant increase in the factor of safety. Hence, the ground improvement should be contacted to the wall to establish a higher basal heave resistance, where the increase of the safety factor was governed by the amount of the ground improvement that contacted the wall. Furthermore, a simplified method was proposed to calculate the factor of safety with and without ground improvement, which was validated by the results from the finite-element method.
•A Burgers-viscoplastic strain-softening (BVSS) model has been implemented into CODE_BRIGHT.•The BVSS is capable to simulate the time-dependent plastic behavior of geomaterials.•A coupled solid-fluid ...model is used to simulate the interaction between solid deformations and fluid flow.•The coupled solid-fluid response of tunnel excavation in saturated time-dependent plastic rock masses has been analyzed.
This article provides a general numerical approach for modelling the response of deep tunnels excavated in saturated time-dependent plastic rock masses, considering a coupled solid-fluid interaction and time-dependent plastic behaviour. In order to do that, a Burgers-viscoplastic strain-softening model has been developed and implemented into the finite element method software CODE_BRIGHT, and a coupled solid-fluid model is used to simulate the interaction between solid deformations and fluid flow. Parametric analyses are then performed to analyse the influence on the tunnelling response of different time-dependent models, different standstill times and different excavation rates. It has been observed that the time-dependent model selection is crucial to simulate the response of underground excavations. Additionally, the coupled solid-fluid results are significantly different from the purely mechanical ones. The liquid pressure build-up in the vicinity of the tunnel face and the overpressure dissipation with time due consolidation can be accounted for. Moreover, the higher the excavation rate, the larger build-up of liquid pressures occurs.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
What became of towns following the official end of ‘Roman Britain’ at the beginning of the 5th century AD? Did towns fail? Were these ruinous sites really neglected by early Anglo-Saxon settlers and ...leaders? Developed new archaeologies are starting to offer alternative pictures to the traditional images of urban decay and loss revealing diverse modes of material expression, of usage of space, and of structural change. The focus of this book is to draw together still scattered data to chart and interpret the changing nature of life in towns from the late Roman period through to the mid-Anglo-Saxon period. The research centres on towns that have received sufficient archaeological intervention so that meaningful patterns can be traced. The case studies are arranged into three regional areas: the South-East, South-West, and Midlands. Individually each town contains varying levels of archaeological data, but analysed together these illustrate more clearly patterns of evolution. Much of the data exists as accessible but largely unpublished reports, or isolated within regional discussions. Detailed analysis, review and comparisons generate significant scope for modelling ‘urban’ change in England from AD 300-600. ‘Towns in the Dark’ dispels the simplistic myth of outright urban decline and failure after Rome, and demonstrates that life in towns often did continue with variable degrees of continuity and discontinuity.
This volume presents the multiyear archaeological investigations of Cerro Juanaqueña and related sites in northwestern Chihuahua, Mexico. These remarkable terraced hilltop settlements represent a ...series of watershed developments, including substantial dependence on agriculture and early experiments with village living, fortified settlements, collective labor, and communal architecture. Part of a larger, regional development, they parallel changes in northern Sonora and southern Arizona. The emergence of large fortified agricultural villages at 1300 BC before the use of ceramics was an unexpected discovery that changed how archaeologists view early agriculture in this region. The authors place their work in a regional and theoretical context, providing detailed analyses of radiocarbon dates, structures, features, and artifacts. Authors Hard and Roney, and their contributors, present innovative analyses of plant and animal remains, ground stone, chipped stone, and landscape evolution. Through comparisons with a global cross-cultural probe of hilltop sites and a detailed examination of the features and artifacts of Cerro Juanaquen~a, Hard and Roney argue that these cerros de trincheras sites are the earliest fortified defensive sites in the region. Readers with interests in ancient agriculture, warfare, village formation, and material culture will find this to be a foundational volume.
Spatial variability in the radius of a jet-grout column is commonly encountered in practice. Although various prediction models for the column radius are available, they have been generally used to ...predict a nominal radius. The radius variation within a column has been seldom considered. In this study, the intracolumn radius variation was simulated as a lognormal stochastic process. This was done based on the existing prediction models where the column radius can be correlated with the undrained shear strength of in situ soils. A slab consisting of overlapping jet-grout columns was considered. The slab serves as an earth-retaining stabilizing structure in a deep excavation. The effects of radius variation on the mass performance of the slab were examined with the finite-element method. In addition, the positioning errors in jet-grout columns were also investigated. Owing to the random nature of the radius variation, Monte-Carlo simulations were performed to estimate the statistical characteristics of the mass performance of the slab. A strength reduction factor was introduced and tabulated to account for the effects of geometric imperfections in the column radius and column position. With the strength reduction factor, practitioners could quantitatively evaluate the effects of these geometric imperfections in design considerations. Practical recommendations on the column length and column spacing were also proposed.
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The ability of robotic excavators to acquire meaningful knowledge about materials during digging can augment their autonomous functionality, as well as optimize downstream operations in construction ...and mining. Some material properties, such as rock sizes, can be determined visually, but these methods cannot see what lies beneath. In this work, a classification methodology that utilizes only proprioceptive force data acquired from an autonomous digging system and machine learning algorithms is proposed for excavation material identification. The consistent performance synonymous with autonomous digging systems allows for the use of basic features extracted from the force data for classification. A proof of concept of this novel approach to excavation material classification is demonstrated through a binary classification of rock and gravel materials. Force data were obtained from full-scale autonomous loading trials with a 14-tonne capacity load-haul-dump machine at a mining and construction test facility. Preliminary results achieved a classification accuracy of 90%.
•A new methodology for material identification using only force data and machine learning•Proof-of-concept demonstrated using data from 86 full-scale autonomous excavation trials•Binary classification of rock and gravel materials evaluated•High classification accuracy (90%) achieved using basic signal features and simple classifiers
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
The Loess Plateau is one of the most vulnerable areas in the world as it is extremely susceptible to soil erosion and ecological destruction. Recently, the local government carried out the “Gully ...Land Consolidation Project” (GLCP) in the Loess Plateau region to increase farmland area, improve rural production and living conditions. Among all the GLCP engineering constructions, slope protection engineering plays an important role in ensuring the safety of the main project, residential lives and properties, although more theoretical and technical research on comprehensive protection of engineering slopes is required. In this study, a field experiment using 12 standard runoff plots (length 4m×width 2m) was performed in Yangjuangou catchment of Yan'an City, to compare and analyze the comprehensive benefit to vegetative growth, soil erosion and engineering benefit from four vegetation styles and three levels of slope gradient (45°, 53°,63°). Results show that under different slope gradient and vegetation styles, significant differences existed in the comprehensive benefit to slopes, as well as the levels of vegetative growth, soil erosion and engineering benefit. The comprehensive benefit of the 53° slope was significantly better than that of 45° and 63° slopes. In addition, the comprehensive benefit of slopes with one or more vegetation styles was better than that of non-vegetation covered slopes. With the increase in slope gradient, the vegetative growth and slope erosion indices of vegetation average height, species richness, vegetation coverage slope, runoff production and sediment yield, showed a remarkable declining trend. Conversely, the engineering benefit index including newly-increased farmland area and excavating earthwork volume, showed an increasing trend. Recently, agricultural geographical engineering (AGE) has become an indispensable method for ecological construction and agricultural development, resulting in an increase in research in the field of geography. These findings not only have theoretical significance and enrich our understanding of the influence of gradient and vegetation styles on excavation slope protection, but also have practical significance and provide a baseline for engineering parameters and suggestions for slope protection engineering strategies.
•A field experiment using 12 standard runoff plots was performed in the Loess Plateau.•The evaluation index system for assessing the comprehensive benefit of excavation slope were established.•The effects of slope gradients and vegetation styles on slope comprehensive benefits were compared and analyzed.•The benefit of the 53° slope was significantly better than that of 45° and 63° slopes.•The slopes with one or more vegetation styles were more stable than that of non-vegetation covered slopes.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
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