This paper presents the results of a laboratory testing program that was designed to investigate the mechanical behaviour of the Tournemire argillite. Eighty rock samples were obtained from boreholes drilled at different angles in the walls and floor of an existing gallery at the Tournemire Underground Research Laboratory (URL), France. The experimental program consists of the measurement of the physical properties of the argillite and its mechanical response to loading during uniaxial tests, triaxial tests with various confining pressures, unconfined and confined cyclic tests, and Brazilian tests. Since the Tournemire argillite is characterized by the presence of closely spaced bedding planes, the rock specimens were loaded in different directions to bedding planes (i.e., loading orientation angle, θ = 0°, 30°, 45°, 60°, and 90°). Acoustic emission data were also recorded to detect the initiation and propagation of micro-cracks during the uniaxial tests. Most of the tests were performed at the natural moisture content of the rock specimens as delivered to CANMET Laboratories in Ottawa, Canada, where the experiments were conducted. The main objective of the testing program is to identify the mechanical properties of the Tournemire argillite. This paper mainly focuses on the description and interpretation of the test results. The development of an elastoplastic-damage model to describe the mechanical behaviour of the Tournemire argillite is the subject of another paper.

The shear strength and stick-slip behaviour of a rough rock joint are analysed using the complex network approach. We develop a network approach using correlation patterns of void spaces of an evolvable rough fracture (crack type II). Correlation among networks' properties with the hydro-mechanical attributes (obtained from experimental tests) of fracture before and after slip is the direct result of the revealed non-contacts networks. We show that networks' parameters yield a close relation to the contact zones' attachment-detachment sequences through the evolution of frictional interfaces. Furthermore results showed correlated patterns of sheared interfaces demonstrating assortative networks indicating the role of ‘hubs’ in driving frictional interfaces. Also, we discuss the scaling of fraction of ‘loops’ in formed networks with different stages of shear strength evolution. Our method can be developed to investigate the complexity of stick-slip behaviour of faults as well as new interpretations of friction laws in terms of network parameters.

Introduction: Piles transfer structural loads to the ground (1) at the surface of their shafts and (2) at their toe (Fig.1). In the calculation of these two components of load transferred from a pile to the soil mass, both the deformation characteristics and the strength properties of the soil need to be taken into consideration. In unsaturated soils, matric suction changes the stressstrain-strength behavior of the soil. Similarly, the adhesion and the friction angle at the contact area between the soil and the pile shaft are affected by the changes in matric suction. In this paper, the effect of soil suction on the shaft resistance and toe resistance of a pile is examined. The pile under consideration is described by Georgiadis et al. (2003). In the present study, soil-pile interaction is analyzed as a contact mechanics problem using COMSOL. The pile is 20 m long and its diameter is 1m. The pile is embedded in the soil with linearly varying matric suction between the ground surface and the GWT which is at D=10m (Fig. 2).

The efficiency of energy piles depends on their dimensions and the heat and moisture transfer characteristics of soils and pile materials. Conductive heat transfer in soil deposits is based on the solution of the Fourier equation with relevant initial and boundary conditions. The equation contains two parameters representing the thermal properties of material: the coefficient of thermal conductivity and the volumetric heat capacity. In this paper, the results of an experimental study are presented first. Tests were conducted earlier to determine the heat and moisture transfer characteristics of a silty soil from the Mackenzie River Valley. COMSOL is used to simulate the heat and moisture transfer in two soil columns and the computational and experimental results are compared. Subsequently, the finite element analysis is extended to the analysis of an energy pile.

Glaciation is considered as one of the main natural processes that can have a significant impact on the long term performance of a deep geological nuclear waste repository (DGR) located in the Northern Hemisphere. The northern part of the American continent has been subjected to a series of strong glaciation and deglaciation events over the past million years. The last glacial cycle in the Northern Hemisphere started approximately 110,000year ago. During that cycle, southern Ontario was buried under a continental ice sheet, with a maximum thickness of up to 3000m at about 20,000years ago. The ice cap retreated approximately 10,000years ago. However, field data from deep boreholes in sedimentary rocks of southern Ontario show anomalous pore water pressure including underpressure and overpressure zones. In this paper, a large-scale coupled hydro-mechanical (HM) model is developed to investigate the hydro-mechanical (HM) response of the sedimentary rocks of southern Ontario to past glacial cycles. Particular emphasis has been placed on the evolution of pore water pressures and surface displacements. The HM model is verified using analytical solutions. The results of the large-scale HM modeling study shows that the past glaciation, particularly the second cycle (22,000 apb) had significant impact on the pore water pressure gradient and effective stress distribution in the sedimentary rocks of southern Ontario. Furthermore, good agreement between the large scale modeling results and anomalous pressures leads us to the conclusion that these anomalies could be glacially induced. The results of this research can provide information that will contribute to a better understanding of the impact of future glaciations on the long term performance of DRGs in sedimentary rocks.

The shear strength and stick-slip behavior of a rough rock joint are analyzed using the complex network approach. We develop a network approach on correlation patterns of void spaces of an evolvable rough fracture (crack type II). Correlation among networks properties with the hydro -mechanical attributes (obtained from experimental tests) of fracture before and after slip is the direct result of the revealed non-contacts networks. Joint distribution of locally and globally filtered correlation gives a close relation to the contact zones attachment-detachment sequences through the evolution of shear strength of the rock joint. Especially spread of node's degree rate to spread of clustering coefficient rate yielded possible stick and slip sequences during the displacements. Our method can be developed to investigate the complexity of stick-slip behavior of faults as well as energy /stress localization on crumpled shells/sheets in which ridge networks are controlling the energy distribution.

A complex network approach on a rough fracture is developed. In this manner, some hidden metric spaces (similarity measurements) between apertures profiles are set up and a general evolutionary network in two directions (in parallel and perpendicular to the shear direction) is constructed. Also, an algorithm (COmplex Networks on Apertures: CONA) is proposed in which evolving of a network is accomplished using preferential detachments and attachments of edges (based on a competition and game manner) while the number of nodes is fixed. Also, evolving of clustering coefficients and number of edges display similar patterns as well as are appeared in shear stress, hydraulic conductivity and dilation changes, which can be engaged to estimate shear strength distribution of asperities.

Understanding of rock joint behaviors, either in single or mass form, under the several natural or artificial forces has been the subject of numerous researches during the evolution of rock mechanics field. Rock joint performance as a result of collective behavior of constructed elements (say fraction/pixel in each surface), interacting with each other, determines nonlinear picture of a changeable system. Obviously, one cannot predict the rich behavior of the whole by merely extrapolating from the treatment of its units (Boccara 2004, Vicsek 2002, Hakan 1989). Absent of fully prediction and nonlinear essences of behavior are prevalent gesture of complex systems. The term complex system formally refers to a system of many parts which are coupled in a nonlinear fashion. When there are many non-linearities in a system (many components), behavior can be highly unpredictable. Complex systems research studies such behavior. Complex systems research overlaps with nonlinear dynamics research, but complex systems consist of a large number of mutually interacting dynamical parts. The success in describing of interwoven systems using physical tools as a major reductionism is associated with the simplifications of the interactions between the elements so that complexity reduction is a rescue pathway to regulation of approximated analyses of collective particles having swing states, complicated structures, and diversity of relations among elements. Complex networks have been developed in the several fields of science and engineering for example social, information, technological, biological and earthquake networks are the main distinguished networks (Albert & Barabasi 2002, Abe & Suzuki 2006).On the other hand, to catch on Hydro-mechanical and mechanical behavior of a rock joint, domination on to the surface morphology and its evolution as well as aperture is irrefutable. In addition to these procedures, the mechanical properties and hydraulic conductivity of the being joint are compared with the network properties. Upon this comparison, the distribution of shear strength –for each profile- is estimated.

Icebergs and ice ridges frequently Scour the surface of seabed deposits. Ice scouring can be problematic for offshore pipelines and other seabed installations. In order to reduce the risk of failure, pipelines are buried in the seabed. However, a stationary or moving ice feature could cause a significant increase in stresses and deformation in the seabed soil deposits below the contact surface between the soil and the ice, and consequently, might result in structural failure of buried pipeline. Safe burial depth for pipelines has been the subject of both experimental and numerical Studies. In this paper, two and three dimensional analyses are conducted using PLAXIS and ADINA. In these analyses, geometric and material nonlinearities are considered. In order to establish the validity of the finite element calculations, the experimental results reported in the literature and the numerical results obtained in the present study are compared. The emphasis is placed on determining the importance of (1) using interface elements between different materials such as soil and ice, soil and pipelines; (2) using the soil model correctly, and (3) using a three dimensional analysis rather than a two dimensional analysis. The changes taking placed in the deformation pattern and the stress states in the seabed soils resulting from ice scouring are determined. The effects of pipeline burial depth, the shape of the ice feature, and the characteristics of seabed soils on the stresses acting on the pipeline are evaluated.

A computational model illustrating the application of the ALE FE method to simulate three dimensional debris flows is presented. The paper studies the influence of the initial and boundary conditions on the dynamics of the debris flows on simplified terrain geometry. The effects of the loading conditions and soil properties are also illustrated. The paper demonstrates the applicability and versatility of the ALE method for the debris flow problem while satisfying all the principles of continuum mechanics.

A concern in the use of tire shreds as drainage media in landfill leachate collection systems is the impact of compression strains on the permeability of the waste material, as earlier work has reported that these materials experience large (25 to 50%) axial strains when subjected to vertical loading. This study examines the changes in permeability of a tire shred sample after being subjected to 30 to 50% axial strain from average vertical stresses of 75 to 330 kPa. The maximum vertical stress of 330 kPa approximated 40m of waste overburden. A constant-head permeability apparatus was fabricated to measure the permeability of the tire shred sample under different axial strains. Further, the fabricated assembly was capable of measuring permeability of the sample at various sample locations at a given strain level. Experimental results showed that despite experiencing large axial strains, the average permeability of the tire shred sample consistently remained two to three orders of magnitude higher than the design performance criterion of 0.01 cm/s for landfill drainage layers, suggesting that the compressible nature of tire shreds will not interfere in their use as a leachate collection drainage layer in municipal solid waste landfills.

This paper presents the results of an experimental study on the mechanical behaviour of an interface between sand and a steel plate. A simple shear type interface apparatus is used. Tests are conducted under a two-way, displacement-controlled cyclic loading condition. The effects of the initial soil density, number of displacement cycles, magnitude of normal stress, and amplitude of tangential displacement on the cyclic response of the interface are investigated. The interface behaviour is presented in terms of the shear stress mobilized on the interface, the changes taking place in sample height, and the components of tangential displacements resulting from soil deformation and from slip between the soil and the steel plate during displacement cycles.Key words: cyclic behaviour, soil–structure interface, simple shear, slip, laboratory testing.

The suitability of shredded tires or “tire chips” for use in the leachate collection drainage layer of a municipal solid waste landfill was investigated in terms of the: (1) compressibility of the tire chips and resulting changes in hydraulic conductivity under varying applied loads, and (2) effect of leachate pH on the shredded tries compressibility and hydraulic conductivity behavior. A constant head hydraulic conductivity apparatus was fabricated to measure the hydraulic conductivity of the tire shred sample under different axial strains. Further, the fabricated assembly was capable of measuring hydraulic conductivity of the sample at various sample locations at a given strain level. One aim of this study was to provide supporting information for permission to use tire chips as an alternative to crushed stone in the leachate collection system of a landfill. Shredded tires from two different sources were used in this study to investigate any differences in the sensitivity of the shredding process to compressibility and hydraulic conductivity responses under varied applied loads. Under applied vertical loads resulting in average vertical stresses of up to 440 kPa, equivalent to over 50 m of waste, the maximum normal strain recorded in each type of tire chip was observed to plateau at a strain level near or slightly greater than 0.5. The results of the permeability testing indicated average hydraulic conductivity values ranging between 0.67 and 13.4 cm/s under average applied normal stresses ranging from approximately 60 to 335 kPa and strain increments between 0.3 and 0.5. These results are one to three orders of magnitude higher than the hydraulic conductivity typically specified for drainage layers in leachate collection systems of 0.01 cm/s. Additional tests were also carried out to identify how landfill leachate and varied pH levels may affect the compressibility and hydraulic conductivity of the shredded tires. Care should be exercised in extending these results to field conditions, as the results presented are based on limited experimental testing data and a limited time frame.