Papers by Mariacristina Bonini
Prove specialistiche di laboratorio per la caratterizzazione meccanica delle rocce e delle discontinuità
Analisi numeriche di simulazione di prove triassiali per lo studio del comportamento rigonfiante dei terreni durante lo scavo di gallerie
Numerical Simulations of Compressive Tests on Bimrock
Numerical simulation of the time-dependent behaviour of Italian clay shales at laboratory scale
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FLAC applications to the analysis of swelling behaviour in tunnels
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Two and three dimensional modelling and monitoring of the Metro Torino
This paper describes the results of subsidence monitoring and back analysis of the tunnel respons... more This paper describes the results of subsidence monitoring and back analysis of the tunnel response along the first section of the Metro Torino Line 1. During excavation, surface settlements were monitored by means of surface levelling and the state of strain/stress in the segmental lining was measured at a number of cross sections. The paper is to gain insights into the ground behaviour analysed by numerical modelling. The aim is to assess the soil deformability and strength parameters as compared to the design values and to predict the stress-strain response in a representative cross section. This paper is concerned with the analysis of ground movements due to tunnelling at a number of monitoring stations during excavation of the Metro Torino Line 1, in a sand and gravel deposit, with presence of the water table. Consideration is given to the transverse and longitudinal settlement trough above and ahead of the advancing tunnel face. The aim is to gain insights into both the ground response and the geotechnical properties, as compared with design predictions and to analyse the interaction between the tunnel and an underground car park in the near vicinity.
Characterisation studies of Tectonised Clay Shales and implications in the excavation of large size tunnels
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Time-dependent behaviour of Italian clay-shales
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Performance monitoring and analysis of a yield-control support system in squeezing rock
Recent innovations in yield-control support systems allow to increase the rate of advance when tu... more Recent innovations in yield-control support systems allow to increase the rate of advance when tunneling in difficult conditions is associated with severely squeezing rock. Such systems which imply the insertion in the lining of highly deformable concrete elements are being adopted successfully in tunneling projects using conventional excavation methods. The Saint Martin access adit excavated in a Carboniferous Formation along the Base Tunnel of the Lyon-Turin rail line ispresented as a case study. Numerical analyses are discussed to compare the results of computed and measured performance of a typical monitored section and to find out possible optimizations of the support system adopted.
The paper deals with the mechanical behaviour of "bimrock" (block in matrix rock), char... more The paper deals with the mechanical behaviour of "bimrock" (block in matrix rock), characterized by a heterogeneous structure, constituted by rock blocks included in a small-grained, well-cemented material (matrix) with lower mechanical characteristics. The bimrock is a very peculiar material that may give rise to serious problems in engineering applications. To properly model this kind of problems it is necessary to suitably characterize the bimrock. In order to contribute to the understanding of the bimrock mechanical behaviour and to individuate strength and deformability laws suitable for the bimrock as an equivalent continuum, as the problem is clearly three-dimensional, 3D numerical analyses have been carried out by using the finite element method implemented in the Adina code. Uniaxial and triaxial compression tests on bimrock laboratory samples are simulated. Different volumetric proportions of the blocks are considered. The numerical results show the influence of ...
This paper deals with full face excavation of large size tunnels in rock masses of very poor qual... more This paper deals with full face excavation of large size tunnels in rock masses of very poor quality which exhibit squeezing behaviour. Time dependence is accounted for explicitly by using constitutive models which have been validated with reference to laboratory testing and in situ performance monitoring. The case study of the Saint Martin La Porte access adit (Lyon-Turin Base Tunnel)
Computers and Geotechnics, 2015
Tunnel Boring Machine (TBM) tunnelling in weak rock associated with high overburden is very deman... more Tunnel Boring Machine (TBM) tunnelling in weak rock associated with high overburden is very demanding due to the difficulties in predicting the complex interactions between the rock mass, the tunnel machine, its system components, and the tunnel support during excavation/construction. These factors affect the performance and even the feasibility of a TBM drive (sticking of the cutterhead and jamming of the shield may occur). In this respect, several computational models such as the Convergence-Confinement Method (CCM), axially symmetric model and three-dimensional (3D) simulation have been developed in the literature. Among these models, this paper presents three modelling techniques (i.e., a 3D simulator using the Finite Element Method (FEM), an axisymmetric model using the Finite Difference Method (FDM) and an LDP (Longitudinal Displacement Profile) approach based on the CCM), and applies them to the Headrace Tunnel from the Kishanganga Hydroelectric Project in India. The three approaches are not considered to be alternatives but rather complementary to each other, depending on the real situation. The LDP approach is a simplified analytical method but is still efficient to provide a conceptual framework for evaluating the ground-shield interplay during mechanised excavation. The FDM axisymmetric model represents a powerful tool (i.e., with a large deformation scheme available) for the simulation of ground behaviour and its interaction with the machine components, especially in the case of weak rocks with high deformability. However, when the conditions violate the important assumptions underlying these two approaches, true 3D numerical analyses are necessary, which consider all the TBM components. Finally, the paper highlights the potentials of the 3D simulator to model the basic features (i.e., stepwise conicity of the shield, backfilling layer and anisotropic in-situ stress state) of a shielddriven deep tunnel, which determine the tunnel's behaviour and its response to TBM advancement. The obtained results show that the 3D nature of the complex interactions and the in-situ state of stress, including the nonlinear behaviour can be better reproduced in a 3D simulation than in the other two methods.
Analysis of the behaviour of a yield-control support system in squeezing rock
ABSTRACT Recent innovations in yield-control support systems allow to increase the rate of advanc... more ABSTRACT Recent innovations in yield-control support systems allow to increase the rate of advance when tunnelling in difficult conditions is associated with severely squeezing rock. Such systems which imply the insertion in the lining of highly deformable concrete elements are being adopted successfully in tunnelling projects using conventional excavation methods. The Saint Martin access adit excavated in a Carboniferous Formation along the Base Tunnel of the Lyon-Turin rail line is presented as a case study. Numerical analyses are discussed to compare the results of computed and measured performance of a typical monitored section and to find out possible optimizations of the support system adopted.
Guidelines for TBM tunnelling in squeezing conditions – a case study
Géotechnique Letters, 2014
ABSTRACT This paper describes a study undertaken to derive hazard scenarios for the excavation of... more ABSTRACT This paper describes a study undertaken to derive hazard scenarios for the excavation of the Kishanganga hydroelectric project headrace tunnel, Kashmir, India. The tunnel is to be driven in poor rock mass conditions (meta-sandstones, meta-siltstones and shales) with expected squeezing behaviour under average to high overburden. The excavation is to be carried out using a double shield universal tunnel boring machine (TBM), with concurrent installation of a segmental lining (SL). The highly variable rock mass conditions and the limited data available, due to difficulty of access to the site, required a detailed preliminary study of the most relevant critical factors such as tunnel overburden, in situ state of stress and rock mass properties. Increasing levels of detail were adopted once the significant hazard scenarios for TBM jamming or overloading of the SL in short- and longterm conditions were outlined. The scenarios were first derived by simplified design methods with the rock mass represented as an elasto-plastic continuum. Subsequently, and following the results of laboratory tests on representative samples, numerical modelling studies were performed with the rock mass being modelled as an elasto-visco-plastic continuum.
The Saint Martin La Porte access adit (Lyon–Turin Base Tunnel) revisited
Tunnelling and Underground Space Technology, 2012
ABSTRACT This paper presents the monitoring data collected over a period of five years from Janua... more ABSTRACT This paper presents the monitoring data collected over a period of five years from January 2006 to December 2010, during which the Saint Martin La Porte access adit of the Lyon–Turin Base Tunnel was excavated through a Carboniferous Formation, a highly heterogeneous, overstressed and in cases anisotropic rock mass exhibiting a squeezing behaviour. The interest of these data stems from the information which became available along a significant tunnel length in the same rock mass, where a novel excavation and support method was adopted with highly deformable elements inserted in the shotcrete lining which allowed for controlled deformation, rate of deformation and stress in the rock mass and in the supports. A description of the geological and geomechanical conditions met and of the tunnel response in different cross sections is given in terms of developed convergences, rates of convergence, strain distributions around the tunnel and ahead of the face, including the state of stress in the supports. In conclusion an attempt is made to characterise the Carboniferous Formation in terms of the extent of squeezing and in view of the future excavation of the Base Tunnel.
State of Stress in Tunnel Lining in Squeezing Rock Conditions
Rock Mechanics and Rock Engineering, 2013
ABSTRACT The Saint Martin La Porte Tunnel, located in South Eastern France near the Italian borde... more ABSTRACT The Saint Martin La Porte Tunnel, located in South Eastern France near the Italian border is one of the access tunnels (together with La Praz and Modane) to the TGV tunnel currently under construction that will connect Lyon and Turin. The excavation of this tunnel through squeezing rock required the adoption of an innovative yield-control support system, assisted by comprehensive performance monitoing and advanced modelling studies. This technical note describes the investigations performed along the tunnnel between chainage 1229 and 1325 m in order to determine the state of stress in the concrete lining. A cast in place lining was chosen in an attempt to stop the large convergences, which occurred in a section where the yield-control system was not yet used. The laboratory tests performed for the cgaracterisation of the mechanical bahaviour of the concrete, the in situ stress relief tets in the lining and simplified numerical modelling are presented.
Rock Mechanics and Rock Engineering, 2009
This paper is a contribution to the study of tunnelling in difficult conditions, with attention p... more This paper is a contribution to the study of tunnelling in difficult conditions, with attention paid to large time-dependent deformations, which may develop either during construction, causing instabilities of the tunnel heading and of the face, or during the service life of the tunnel. Under these circumstances the construction costs may rise due to the delays in excavation time, the stabilisation and heavy support measures that need be adopted. Following a review of characterisation and modelling of time-dependent behaviour in rock, the mechanical behaviour of Clay Shales (CS), a structurally complex formation of the Apennines (Italy), is described. Then, the key factors involved in the selection of the constitutive model for CS are identified. Two constitutive models are selected and discussed and their specific material parameters determined. A case study of a large size tunnel is presented where numerical modelling by the finite difference method is carried out. The results of modelling are compared with the monitoring data in terms of radial convergence of the tunnel and extrusion of the tunnel face.
International Journal of Rock Mechanics and Mining Sciences, 2004
This paper describes the characterisation studies carried out so far on Italian clay shales, invo... more This paper describes the characterisation studies carried out so far on Italian clay shales, involved in the construction of significant tunnel lengths. Laboratory tests performed on cylindrical specimens, taken from either cubic samples at the tunnel face or from borehole drilling, point out the characteristics of clay shales: chaotic structure (tectonized and intensely fissured), sensitivity to ionic concentration of pore fluid, swelling/squeezing behaviour. Numerical analyses have been performed in order to reproduce the response of clay shales both at laboratory and in situ scale, in undrained and drained conditions. The difficulties in assessing the design parameters based on laboratory testing are evidenced, thus pointing out the importance of in situ observation and monitoring of the tunnel response during excavation.
Comportamento rigonfiante delle argille scagliose sulla base di nuove determinazioni sperimentali
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Papers by Mariacristina Bonini