Harmonising Rock Mechanics and the Environment comprises the proceedings (invited and contributed papers) of the 12th ISRM International Congress on Rock Mechanics (Beijing, China, 18-21 October 2011). The contributions cover the entire scope of rock mechanics and rock engineering, with an emphasis on the critical role of both disciplines in sustai

On the variability of squeezing behaviour in tunnelling

Squeezing conditions in tunnelling are characterized by the occurrence of large deformations of the opening or high rock pressure that may overstress the lining. Squeezing is associated with poor quality rock. Tunnelling in squeezing ground involves great uncertainties. It is therefore very important to gain a better understanding of the underlying mechanisms. Triaxial testing is the main source of information in order to understand the mechanical features of squeezing ground. Despite the complexity of the squeezing mechanism and the behaviour observed under relatively simple loading conditions, most of previous research work and engineering design practice considers the ground as a linearly elastic, perfectly plastic material obeying the Mohr-Coulomb yield criterion. While the MC model is capable of predicting the final strength and post-failure volumetric behaviour of the squeezing rock, it cannot map some potentially important pre-failure features or the occasionally observed contractant plastic deformation. In addition, the MC model usually leads to an overestimation of the strength under undrained conditions, which is unsafe for tunnel design. The present thesis mainly addresses the influence of constitutive modelling on predictions about the response of squeezing ground to tunnelling in order to provide some general guidelines for basic engineering analysis. This objective is achieved by investigating the behaviour of squeezing rocks theoretically and experimentally, using samples from several tunnel projects, including the Gotthard base tunnel and the planned Gibraltar strait tunnel.

Numerical Methods in Geotechnical Engineering IX contains 204 technical and scientific papers presented at the 9th European Conference on Numerical Methods in Geotechnical Engineering (NUMGE2018, Porto, Portugal, 25—27 June 2018). The papers cover a wide range of topics in the field of computational geotechnics, providing an overview of recent developments on scientific achievements, innovations and engineering applications related to or employing numerical methods. They deal with subjects from emerging research to engineering practice, and are grouped under the following themes: Constitutive modelling and numerical implementation Finite element, discrete element and other numerical methods. Coupling of diverse methods Reliability and probability analysis Large deformation – large strain analysis Artificial intelligence and neural networks Ground flow, thermal and coupled analysis Earthquake engineering, soil dynamics and soil-structure interactions Rock mechanics Application of numerical methods in the context of the Eurocodes Shallow and deep foundations Slopes and cuts Supported excavations and retaining walls Embankments and dams Tunnels and caverns (and pipelines) Ground improvement and reinforcement Offshore geotechnical engineering Propagation of vibrations Following the objectives of previous eight thematic conferences, (1986 Stuttgart, Germany; 1990 Santander, Spain; 1994 Manchester, United Kingdom; 1998 Udine, Italy; 2002 Paris, France; 2006 Graz, Austria; 2010 Trondheim, Norway; 2014 Delft, The Netherlands), Numerical Methods in Geotechnical Engineering IX updates the state-of-the-art regarding the application of numerical methods in geotechnics, both in a scientific perspective and in what concerns its application for solving practical boundary value problems. The book will be much of interest to engineers, academics and professionals involved or interested in Geotechnical Engineering.

Tunnels and Underground Cities: Engineering and Innovation meet Archaeology, Architecture and Art. Volume 7: Long and Deep Tunnels contains the contributions presented in the eponymous Technical Session during the World Tunnel Congress 2019 (Naples, Italy, 3-9 May 2019). The use of underground space is continuing to grow, due to global urbanization, public demand for efficient transportation, and energy saving, production and distribution. The growing need for space at ground level, along with its continuous value increase and the challenges of energy saving and achieving sustainable development objectives, demand greater and better use of the underground space to ensure that it supports sustainable, resilient and more liveable cities. The contributions cover a wide range of topics, from studying tunnels in squeezing ground conditions, via case studies on the Brenner Base Tunnel, the second Gotthard Tunnel, CERN (HL-LHCand the Dubai Strategic Sewerage Tunnel, to TBM steering difficulties. The book is a valuable reference text for tunnelling specialists, owners, engineers, archaeologists, architects, artists and others involved in underground planning, design and building around the world, and for academics who are interested in underground constructions and geotechnics.

Numerical Methods in Geotechnical Engineering IX contains 204 technical and scientific papers presented at the 9th European Conference on Numerical Methods in Geotechnical Engineering (NUMGE2018, Porto, Portugal, 25—27 June 2018). The papers cover a wide range of topics in the field of computational geotechnics, providing an overview of recent developments on scientific achievements, innovations and engineering applications related to or employing numerical methods. They deal with subjects from emerging research to engineering practice, and are grouped under the following themes: Constitutive modelling and numerical implementation Finite element, discrete element and other numerical methods. Coupling of diverse methods Reliability and probability analysis Large deformation – large strain analysis Artificial intelligence and neural networks Ground flow, thermal and coupled analysis Earthquake engineering, soil dynamics and soil-structure interactions Rock mechanics Application of numerical methods in the context of the Eurocodes Shallow and deep foundations Slopes and cuts Supported excavations and retaining walls Embankments and dams Tunnels and caverns (and pipelines) Ground improvement and reinforcement Offshore geotechnical engineering Propagation of vibrations Following the objectives of previous eight thematic conferences, (1986 Stuttgart, Germany; 1990 Santander, Spain; 1994 Manchester, United Kingdom; 1998 Udine, Italy; 2002 Paris, France; 2006 Graz, Austria; 2010 Trondheim, Norway; 2014 Delft, The Netherlands), Numerical Methods in Geotechnical Engineering IX updates the state-of-the-art regarding the application of numerical methods in geotechnics, both in a scientific perspective and in what concerns its application for solving practical boundary value problems. The book will be much of interest to engineers, academics and professionals involved or interested in Geotechnical Engineering. This is volume 2 of the NUMGE 2018 set.

Squeezing ground represents a challenging operating environment as it may slow down or obstruct TBM operation. Due to the geometrical constraints of the equipment, relatively small convergences of 10-20 cm may lead to considerable difficulties in the machine area (sticking of the cutter head, jamming of the shield) or in the back-up area (e.g., jamming of the back-up equipment, inadmissible convergences of the bored profile, damage to the tunnel support). Depending on the number and the length of the critical stretches, squeezing conditions may even call into question the feasibility of a TBM drive. On account of this, and bearing in mind the steady increase in the number of tunnels excavated with TBMs through so-called "difficult ground conditions", the topic investigated in this PhD thesis is of great practical relevance.Based upon case histories reported in the literature, Part I sets out firstly to give an overview of the specific problems of TBM tunnelling under squeezing conditions. Part II presents a computational model which simulates accurately and efficiently the advancing TBM and the installed tunnel support in one single computational step applying the so-called "steady state method". Part III advances a number of theory-based decision aids, which will support rapid, initial assessments to be made of thrust force requirements. Part IV investigates the complex problem of the interaction between the advancing TBM, the consolidating ground and the lining. Emphasis is thereby placed on the effect of the gross advance rate and the effect of ground permeability on shield loading during regular TBM operation (the boring process including short standstills) and during a long standstill.

Experimental investigations for the modelling of anhydritic swelling claystones

This PhD thesis investigates the effectiveness of drainage measures with respect to two particularly important problems associated with tunnelling through water-bearing, weak ground: the stability of the tunnel face and the stability and deformation of grouting bodies. Water is an adverse factor with respect to the stability and deformation of underground structures due to the pore water pressure and the seepage forces associated with seepage flow towards the tunnel. Drainage boreholes reduce the pore water pressure and the seepage forces in the vicinity of the cavity. Furthermore, loss of pore water pressure increases the effective stresses and thus the shearing resistance of the ground („consolidation“), which is favourable in terms the deformation occurring during and after tunnelling. The goal of the PhD thesis is to elaborate a more detailed understanding of the interrelationships between drainage measures and the stability of the tunnel face and grouting bodies. The main objectives of the investigations relating to the tunnel face are: 1. analysis of face stability through limit equilibrium computations taking account of the numerically determined seepage flow conditions prevailing in the ground after the implementation of drainage measures; 2. systematic investigation of tunnel face stability considering several different drainage layouts and working out designnomograms; 3. consideration of a series of aspects limiting pore pressure relief and thus the effectiveness of drainage measures and their impact on face stability. The main objectives of the investigations with regard to grouting bodies are: 1. a study of the stabilizing effect of the virtual case of ideal drainage on tunnel support and plastification in grouted fault zones in plane strain conditions; 2. a comparison with the stabilizing effect of real drainage layouts, i.e. when considering pore pressure relief due to specific drainage borehole arrangements; 3. application of the drainage measure both before and after the injection works. In summary, the contribution of this PhD thesis is the detailed investigation of the static effects of drainage measures during tunnelling in water-bearing ground with respect to the stability of the tunnel face and the grouting body as well as the supply of design aids capable of providing a quick assessment of face stability when considering a number of advance drainage schemes.