TBM pressure models: observations, theory and practice

Mechanized tunnelling in soft ground has evolved significantly over the last 20 years. However, the interaction between the tunnel boring machine (TBM) and the ground is often understood through idealized concepts, focused mostly on the machine actions in detriment of the reactions from the ground. These concepts cannot be used to explain several mechanisms that have been observed during the construction of mechanized tunnels. Therefore, this paper presents the path from field observations to the theoretical developments to model the TBM-ground interaction more realistically. Some ideas on how these developments can be applied into practice are presented. Finally, a discussion is proposed about how an effective collaboration between academia and industry can alleviate the current concentration of knowledge in the state of practice

Seismic prediction and imaging of geological structures ahead of a tunnel using surface waves

To improve the performance and safety of tunnel constructions, we introduce a new seismic prediction method utilizing tunnel surface waves to detect relevant geological structures ahead of the tunnel face. On the basis of both synthetic and field data, we investigate the propagation characteristics of such surface waves propagating along the tunnel wall. We further introduce a simple but robust automatic prediction scheme that can estimate the distance to a reflector ahead of the tunnel

Análise da subsidencia xerada pola escavación de dous túneles utilizando máquinas tuneladoras EPB (Earth Pressure Balance). Estudio da relación entre as variables de perforación e os asentamentos inducidos.

Currently the development in the use of underground space in urban environments is being instrumental in the planning and management of cities. This use of underground space arises as a result of the growth of cities, demanding infrastructure that accommodate and respond to all that the city needs demand. One of the key pieces to carry out sustainable urban development is improving its transport and communication. For this, new rail and road networks are being designed and implemented using the latest technologies in underground excavations. An example of development of underground space for improving the transport network is the one that is running in London; Crossrail. Crossrail is the largest underground construction project that is currently underway in Europe. It is the development of a new railway network that would connect the West Zone (Reading) with the East (Abbey Wood and Shenfield) London area, through the British capital. A total of 42 km of tunnels have been excavated tunnel boring machines used. 10 sections of tunnels have been dug with 8 TBMs that have passed under the city, sharing space with the underground network in London, the Thames river, large Racacielos, old foundations, stations, collectors and underground rivers at depths up 40 m. This urban environment requires absolute control of the subsidence that may arise. The objective is to determine the influence that the excavation of two tunnels by EPB, has generated over the seats and set a proceeding that, depending on the evolution of the excavation, anticipate the possibility of generating a seat surface.Actualmente el desarrollo en el uso del espacio subterraneo en entornos urbanos esta siendo pieza clave en la planificacion y gestion de las ciudades. Este uso del espacio subterrano surge como la consecuencia del crecimiento de las ciudades, demandando infraestructuras que den cabida y respuesta a todas las necesidades que la ciudad demanda. Una de las piezas clave para poder llevar a cabo un desarrollo urbano sostenible es la mejora de su red de transporte y comunicacion. Para ello, nuevas redes ferroviarias y viarias se estan diseñando y ejecutando, utilizando las ultimas tecnologias en excavaciones subterraneas. Un ejemplo de desarrollo del espacio subterraneo para la mejora de la red de transporte es el que se esta ejecutando en Londres; Crossrail. Crossrail es el mayor proyecto de construccion subterraneo que se esta realizando actualmente en Europa. Consiste en el desarrollo de una nueva red ferroviaria que conectara la la zona Oeste (Reading) con la zona Este (Abbey Wood y Shenfield) de Londres, atravesando la capital britanica. Un total de 42 km de tuneles han sido excavados utilizado maquinas tuneladoras. 10 tramos de tuneles se han excavado con 8 tuneladoras que han pasado por debajo de la ciudad, compartiendo el espacio con la red de metro de Londres, el rio Thames, grandes racacielos, antiguas cimentaciones, estaciones, colectores y rios subterraneas a profundidades de hasta 40 m. Este entorno urbano exige un control absoluto de las subsidencias que se puedan generar. El objetivo es determinar la influencia que la excavacion de dos tuneles mediante EPB, tiene sobre los asientos generados y establecer un procedimento que, en funcion de la evolucion de la excavacion, anticipe la posibilidad de generar un asiento en superficie.Actualmente o desenvolvemento no uso do espazo subterráneo en ambientes urbanos está fundamental para a planificación e xestión das cidades. Este uso subterrano espazo xorde como resultado do crecemento das cidades, esixindo infraestrutura que acomodar e responder a todo o que a cidade ten demanda. Unha das pezas clave para levar a cabo o desenvolvemento urbano sostible e mellorar o seu transporte e comunicación. Para iso, novas redes ferroviarias e estradas están sendo deseñados e implementados utilizando as recentes tecnoloxías en escavacións subterráneas. Un exemplo de desenvolvemento do espazo subterráneo para mellorar a rede de transporte é o que está a ser executado en Londres; Crossrail. Crossrail é o maior proxecto de construción subterránea que está actualmente en curso en Europa. É o desenvolvemento dunha nova rede ferroviaria que ligaría a Zona Oeste (Reading) co Oriente (Abbey Wood e Shenfield) Área de Londres, a través da capital británica. Un total de 42 km de túneles foron excavados túnel máquinas de perforación usados. 10 seccións de túneles foron escavados con 8 TBM que pasaron baixo a cidade, dividindo espazo coa rede de metro de Londres, o río Támesis, gran Racacielos, fundacións antigas, estacións, recolectores e ríos subterráneos en profundidades de ata 40 m. Este ambiente urbano esixe control absoluto da subsidência que poida xurdir. O obxectivo é determinar a influencia que a escavación de túneles por dous EPB, xerou ao longo dos asentos e establecer un proceso que, dependendo da evolución da excavación, prevista a posibilidade de xerar unha superficie de asento

Geotechnical engineering design of a tunnel support system - a case study of Karuma (600MW) hydropower project

Tunnels have been built since 2180 B.C., through the stone age. They became popular worldwide since the eighteenth century, as transportation, military, mining, conveyance, storage and flood control structures. Due to the increasing world population, urbanization and industrialization, the construction of underground tunnel structures are preferred as they limit interferences with existing surface uses of the land and water bodies. Although underground tunnels are a common flexible construction alternative, they are high hazard risk structures. The risks are mostly related to ground conditions. Tunnels buried at depth disturb in-situ conditions, cause ground instability and ultimately failure. Widespread tunnel failures, though not publicly advertised because of their adverse implications, have claimed human lives, cleared cities, cost 100 million United States dollars' worth in financial losses and year-long project delays. As such, stability of the structures is crucial to prevent the catastrophes thereby reducing societal outcries. Permanency of underground structures is ensured by provision of adequate resistance to any impeding failure of the ground surrounding deep underground excavations. The effectiveness of the ground-support interaction depends on geology, material properties, geotechnical parameters, loads of the surrounding ground mass and mechanism of the interaction. Using actual project information, the factors influencing stability, structural resistance as well as methods to select the required support are explored in this dissertation. The study used typical geological data of an underground tunnel component of Karuma, a proposed 600MW hydropower project in Uganda. It doubles as the largest hydropower project and first underground construction, to date. The project is located along the River Nile in a sensitive ecosystem neighboring both a major national park and the Great Rift Valley system in East Africa. The instability problem at Karuma was assessed using scientific and universal tunneling practice. Typical site data formed input for the geotechnical engineering design of the tunnel support based on analytical, observational and empirical methods. The study demonstrated that all methods were independent and dissimilar for the same geotechnical engineering challenge of the underground structure. The most comprehensive method was the one based on geotechnical engineering principles and rock mechanics theory. The outcomes of the different approaches in this study were unique functions of their underlying scientific philosophies. The study proposes that in designing adequate support systems to resist forces causing failure of underground tunnels, excavations buried in the ground should encompass several methods. The most conservative design should be chosen to ensure permanency

Risk analysis for tunneling projects

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, 2010.Cataloged from PDF version of thesis.Includes bibliographical references (p. 574-589).Tunnel construction is increasing world wide. Although the majority of tunnel construction projects have been completed safely, there have been several incidents that have resulted in delays, cost overruns, and sometimes more significant consequences such as injury and loss of life. To help eliminate these accidents, it is necessary to systematically assess and manage the risks associated with tunnel construction. In order to better understand the conditions under which accidents occur, a database of 204 tunnel construction accidents was assembled. This is the most comprehensive database known to date. The database was analyzed to better understand the causes of accidents. Influence diagrams were constructed containing the main factors, and the interactions between them. These served as the basis of the risk assessment methodology presented in this work. The risk assessment methodology consists of combining a geologic prediction model that allows one to predict geology ahead of the tunnel construction, with a decision support model that allows one to choose amongst different construction strategies the one that leads to minimum risk. The geologic prediction model is based on Bayesian networks because of their ability to combine domain knowledge with data, encode dependencies among variables, and their ability to learn causal relationships.(cont.) The combined geologic prediction - decision support model was then applied to the Porto Metro, in Portugal. The results of the geologic prediction model were in good agreement with the observed geology, and the results of the decision support model were in good agreement with the construction methods used. More significant, however, is the ability of the model to predict changes in geology and consequently changes in construction strategy. This was shown in two zones of the tunnel were accidents occurred, where the model predicted an abrupt change in geology, and the construction method should have been changed but was not. Using the model could have possibly avoiding the accidents. This risk assessment methodology provides a powerful tool with which planners and engineers can systematically assess and mitigate the inherent risks associated with tunnel construction.by Rita L. Sousa.Ph.D

Index to 1986 NASA Tech Briefs, volume 11, numbers 1-4

Short announcements of new technology derived from the R&D activities of NASA are presented. These briefs emphasize information considered likely to be transferrable across industrial, regional, or disciplinary lines and are issued to encourage commercial application. This index for 1986 Tech Briefs contains abstracts and four indexes: subject, personal author, originating center, and Tech Brief Number. The following areas are covered: electronic components and circuits, electronic systems, physical sciences, materials, life sciences, mechanics, machinery, fabrication technology, and mathematics and information sciences

Index to 1985 NASA Tech Briefs, volume 10, numbers 1-4

Short announcements of new technology derived from the R&D activities of NASA are presented. These briefs emphasize information considered likely to be transferrable across industrial, regional, or disciplinary lines and are issued to encourage commercial application. This index for 1985 Tech Briefs contains abstracts and four indexes: subject, personal author, originating center, and Tech Brief Number. The following areas are covered: electronic components and circuits, electronic systems, physical sciences, materials, life sciences, mechanics, machinery, fabrication technology, and mathematics and information sciences

NASA patent abstracts bibliography: A continuing bibliography. Section 1: Abstracts (supplement 29)

Abstracts are provided for 115 patents and patent applications entered into the NASA scientific and technical information system during the period January 1986 through June 1986. Each entry consists of a citation, an abstract, and in most cases, a key illustration selected from the patent application