Compressive Normal Stress Research Articles

Experimental Study of Shear Behavior of Rock Joints under Two Types of Boundary Conditions: Constant Normal Load and Constant Normal Stiffness

Shear destruction of rock mass along weakened planes is one of the main reasons of the failure of career boards, underground workings and rock slopes. The paper deals with laboratory testing of rock joints under direct shear loading. Special test and measurement complex was created to study deformation and strength characteristics of rock joints. Test specimens were made from single slab of sandstone of homogeneous structure. Shear tests have been conducted under constant normal load (CNL) and constant normal stiffness (CNS) boundary conditions at three values of normal compressive stress: 0.5 MPa, 1.2 MPa and 1.8 MPa. The analysis of test results allowed to reveal patterns of changes of deformation-strength properties of rock joints depending on the level of normal load, boundary conditions and roughness values. The ultimate shear stress is always higher under CNS boundary condition than CNL for the same values of normal compressive stress. Shear stress practically retains constant value after reaching the ultimate stress under CNL boundary conditions and it decreases under CNS conditions. The values of ultimate shear stresses, shear modulus and the length of linear section on “shear stress–shear displacement” curve increases with increasing surface roughness at the equal levels of normal compressive stress.

An experimental study: various influence factors affecting interfacial shear performance of UHPC-NSC

Ultra-high performance concrete (UHPC) is an innovative cement-based material with high tensile and compressive strengths, extremely low permeability, and excellent durability. It is suitable for repair and rehabilitation of damaged normal strength concrete (NSC) structures. However, in order to ensure that the UHPC layer co-works well with the NSC structures, a good shear bond between UHPC and NSC is the main concern. In this study, the shear properties of UHPC-NSC interface were systematically studied through a series of double-sided direct shear tests, and the shear capacity and corresponding interfacial failure modes were obtained. Different factors affecting the shear capacity of the UHPC-NSC interface were discussed, namely, strength of NSC, age of UHPC at loading, curing regime for UHPC, surface treatment of NSC substrate, wettability of NSC substrate, addition of expansive agent for UHPC, and exertion of tensile or compressive stress on the interface except for shear stress. The test results showed that the interface between the UHPC layer and NSC substrate exhibited an excellent bond behavior. Most specimens failed in a mode of partial interface failure + partial NSC failure or complete NSC failure in shear, and the remaining few specimens developed purely interface failure. Also, shear failure of some test specimens performed a certain degree of brittleness. According to the test results, the higher the strength or wettability of NSC substrate, the greater the shear capacity of the interface. The shear capacity of UHPC-NSC interface increased rapidly when the age of UHPC increased from 3 days to 7 days, and at the age of 7 days, the shear strength of UHPC-NSC interface could reach more than 90% of the final shear strength. It was revealed that the shear strength of UHPC-NSC interface with steam curing for UHPC at a temperature of 90 °C reduced by 12.9% compared to that with normal curing. The addition of expansive agent to UHPC slowed down the development of the shear capacity of UHPC-NSC interface at the early age and slightly reduced the shear capacity at the age of 28 days and 180 days. Roughing NSC surfaces could significantly improve the interfacial shear capacity. Moreover, the number and area of UHPC tenons in the holes, UHPC grooved joints or post-installed rebars could also affect the shear capacity of the interface. The shear capacity of UHPC-NSC interface under combined tensile and shear stresses decreased significantly, while the shear capacity under combined compressive and shear stresses increased obviously with the increment of shear capacity gradually decreased as the increase of normal compressive stress.

Stress-strain state of a reinforced stepped bimodular column

The article discusses the reinforced stepped column under the action of forces applied along its axis. The column is clamped at the ends and made of a bimodular material, that is, a material having different elastic moduli in tension and compression. Formulas for normal stresses are obtained, depending on the mechanical characteristics of the column material, the geometrical values of the column, and the reinforcement bars. Numerical calculations were carried out for a column made of fibro-foam concrete, in which the elastic modulus of tensile strength is greater than the elastic modulus of compression. The influence of different modulus of the material on the stressed state of the column in the compressed and stretched parts was investigated. The graphs of the normal stresses as a function of the number of reinforcement bars of the stretched zone with a constant number of reinforcement bars in the compressed zone with and without bimodularity are given. It is shown that in some cases normal tensile stresses without bimodularity are 46% less than with bimodularity, and compressive normal stresses are 29% more than with bimodularity.

Seismic responses of a free-standing two-story steel moment frame equipped with a cast iron-mortar sliding base

An experimental study was conducted to evaluate the dynamic behavior of a free-standing frame equipped with a movable base system using cast iron and mortar as the bearing materials. The preliminary friction test indicated that a graphite layer developed on the interface and exhibited stable friction behavior. The friction coefficient ranged from 0.33 to 0.36 when the applied normal compression stress ranged from 2.6 to 5.2 MPa. The effect of the variation of normal compression stress would be small. Shaking table tests on the free-standing frame showed that rock, slide, and rock-slide responses occurred. The cumulative slide distance reached 381 mm under JMA Kobe wave excitation; however, only a few cyclic slides occurred at the same locations along the moving track. Most surfaces sustained single slides. Similar results can be observed in other shaking conditions. The insufficient cyclic sliding and significant rocking resulted in a few graphite layers on the mortar surfaces. Friction coefficients were generally similar to those obtained in the preliminary friction tests; however, the values fluctuated when the rocking became significant. The collisions due to rocking caused strong horizontal acceleration responses and resulted in high friction coefficient. In addition, the strong horizontal acceleration responses caused by the collisions made the freestanding specimen unable to reduce the input horizontal acceleration notably, even when slippage occurred. Compared with the counterpart fixed-base specimen, the specimen equipped with the iron-mortar base could reduce the horizontal acceleration amplification response and the structural deformation, whereas the vertical acceleration response was doubled due to collisions from rocking.

Asymmetrical response of edge pyramidal dislocations in HCP zirconium under tension and compression: A molecular dynamics study

The structure and motion of <c+a> edge dislocations on the pyramidal I 101-1 plane in α-Zr was characterized by atomistic simulations. The dislocations dissociate into 1/6[022-3] and 1/6[4-043] partial dislocations with dissimilar core structures. In order to capture the slip behavior of the system, shear stress was applied, in tandem with tension or compression normal stress. The simulations indicate that the critically resolved shear stress (CRSS) increases under compression and decreases under tension. They also indicate that CRSS associated with a single dislocation depends on the direction of shear, as this alters the nature of the leading partial dislocation during slip. Finally, the molecular dynamics indicates that compression leads to cross-slip of the partial dislocations.

POWER ANALYSIS OF THE PROCESS OF BRITTLE MATERIALS DESTRUCTION IN UNIVERSAL CRUSHING MACHINE WITH ROLL LOCKER

The processing of friable materials used in metallurgical industry for production of definite size classes requires operation of crushing machines, including single-roll machines. Parameters of crushing process are degree and efficiency of crushing. The crushing degree is estimated by the ratio of dimensions of the initial crushing and resulting pieces and depends on the size of gap between the roll and the fixed jaw. Crushing efficiency is determined by mass of material crushed by consumed electric energy unit, and depends mainly on strength of crushed material. In order to reduce energy consumption needed for crushing, a single-roll crusher was developed at Siberian State Industrial University with forced feeding of crushing piece into the fracture zone due to the locker located on the roll. Forces of technological resistance appearing during machine operation are the main initial values for machine drive power and structural elements strength testing, thus, the operation power analysis is an integral stage in the design of any machine, including a crushing one. In the present work, forces acting on a crushing piece from roll side and fixed jaw in vertical and horizontal planes are identified. Based on the results obtained, it was determined that internal compressive forces acting on piece of crushing material cause action of normal compressive stresses in a piece, as well as an internal torque effect, which causes shearing stresses action, i.e. a complex stress state is generated in a fractioned piece with simultaneous action of normal and shearing stresses, under which action a fractioning piece is destroyed. Thus reduction in energy consumption for crushing is achieved, with all other conditions being equal. It reduces energy consumption of a single-roll crusher with forced feeding of material into the crushing zone.

A study of ultraprecision mechanical polishing of single-crystal silicon with laser nano-structured diamond abrasive by molecular dynamics simulation

In the present study, a newly proposed mechanical polishing method of single-crystal silicon with nano-structured diamond abrasives fabricated by laser was investigated, using molecular dynamics (MD) simulations. The results were compared to conventional mechanical polishing under the same machining parameters. Polishing forces, atomic displacement, development of hydrostatic and von Mises stresses in the subsurface zone, temperature distribution, and polished surface morphologies during nano-polishing were investigated. An analysis model was also built to explore the subsurface damage mechanism in terms of examining the hydrostatic and shear stress distributions during nano-polishing. The analyses demonstrated that structured abrasives in silicon polishing lead to lower polishing forces, thinner subsurface damage layer, lower hydrostatic stresses, lower defect atom numbers, and less compressive normal stresses. Nevertheless, structured nanoscale abrasive polishing leads to lower material removal rates. Additionally, more Si-II forms from Si-I, when polishing with #-shaped groove abrasive is performed.

A numerical study on subsurface quality and material removal during ultrasonic vibration assisted cutting of monocrystalline silicon by molecular dynamics simulation

Molecular dynamics (MD) simulation is used to study the subsurface quality and material removal of single crystal silicon with a diamond tool during ultrasonic elliptical vibration assisted cutting (UEVAC), 1D ultrasonic vibration assisted cutting (1D UVAC) and traditional cutting (TC) process. In the simulations, a long-range analytical bond order potential is used to describe the interaction inside the silicon specimen, providing a more accurate depiction of the atomic scale mechanisms of ductile plasticity, brittle fracture, and structural changes in silicon. The results show that UEVAC and 1D UVAC in cutting brittle material silicon causes a much smaller cutting force, much lower von Mises stress at the subsurface, larger material remove rate, lower compressive normal stress and and smaller shear stress In addition, the hydrostatic stress of subsurface for TC and 1D UVAC is much higher than that for UEVAC, which results in fewer Si-II and bct5-Si formed from the original Si-I in UEVAC. Moreover, the number of other atoms for UEVAC is overall smaller than those of using TC and 1D UVAC, which confirms that UEVAC produces a better subsurface. And atomic flow field analysis shows that the UEVAC tends to cut silicon in a more ductile mode. Besides, the temperature in front of tool edge and below the tool flank face of TC is much higher. This means that 1D UVAC and UEVAC have a positive effect on the tool life. However, the temperature in subsurface zone is overall larger, which reveals that 1D UVAC and UEVAC have a negative effect on the subsurface temperature.

Initial orientation of the fretting fatigue cracks in shrink-fit connection specimens

The bending configuration of shrink-fitted connection fretting fatigue tests causes a fluctuation of the contact pressure and in turn a more favourable condition for shear, rather than tensile, crack initiation. According to the classification Type I (shear) and Type II (tensile) fretting cracks, the type II was only observed for the tests with no surface enhancement, which experienced the lowest fretting strength and then a reduced pressure fluctuation effect. The crack initial direction was predicted as the critical plane orientation undergoing the maximum FS stress parameter, for the shallow type I shear cracks. If the critical plane is searched at the fretting hot-spot, the incorrect outward direction is obtained, since the orthogonal direction, with the same shear stress amplitude, experiences a more compressive maximum normal stress. On the contrary, with the application of the Point Method, taking the stress location at half the critical distance and by following the potential critical plane, a higher shear stress along the inward direction is obtained. The more compressive stress below the contact can therefore be compensated, and then the inward shallow direction is correctly predicted.

Embrittlement of an elasto-plastic medium by an inclusion

A mathematical model for the embrittlement of a long elastic-plastic crack by a relatively small, misfitting inclusion is presented. The model makes direct contact with the Dugdale–Bilby–Cottrell–Swinden model as a limiting case. The particular case of an oxide inclusion with a triangular cross-section at the tip of an intergranular crack in the Ni-based superalloy RR1000 at 650,^{circ }hbox {C} is considered. The positive misfit of the intrusion provides an additional tensile load on the crack tip and on the plastic zone, raising the local stress intensity factor k_I and the crack tip opening displacement {varDelta } u above those when the inclusion is replaced by a dislocation-free zone of the same length. It is shown that for a given misfit strain and inclusion shape, the enhancement of k_I and {varDelta } u is controlled by a dimensionless parameter omega = (sigma /sigma _1)sqrt{c/(2l)} where sigma is the applied stress, sigma _1 is the yield stress, c is the crack length and l is the length of the inclusion. The anti-shielding effect of the intrusion is significant only when omega lesssim 6. As a result of the anti-shielding effect of the intrusion, the stress singularity at the crack tip always exceeds the compressive normal stress that exists within the thickest part of the intrusion when it is isolated. It is also shown that the gradient of the hydrostatic stress within the intrusion subjected to different applied stresses drives the oxygen diffusion and, hence, assists the oxidation at the grain boundary. The fracture toughness is considerably greater than that of a bulk sample of the oxide particle, which we attribute to the plastic zone.

Grading opening and shearing deformation of deep outward-dip shear belts inside high slope: A case study

Tectonic shear belts, with their low mechanical strengths, large spatial extents and obvious shearing damage, present challenges for the excavation of high slopes. In this study, we described the basic unloading performances of shear belts induced by excavation through observational data and numerical back analysis. The unloading deformation and failure processes of deep outward-dipping shear belts exposed on a hydraulic slope nearly 300 m tall were investigated first. The field observation and monitoring data indicated that the excavation-induced deformation pattern of the outward-dipping shear belt can be divided into two stages: primarily opening deformation normal to the shear belt during the first stage and primarily shear deformation along the shear belt during the second stage, manifested as opening and shear cracks along the active shear belt. Then, the numerical and analytical analysis were performed to expose the displacement evolution of the shear belt during the multistep excavation of the slope from the top down. The back analysis showed that the grading deformation mechanism of the shear belt was primarily related to the reduction of normal compressive stress on the shear belt's plane due to slope excavation. The reinforcement schemes, including a prestressed anchor cable to limit deep unloading deformation and a prestressed rock bolt to restrain the surface relaxation of the rock mass of the slope, were also discussed. In practice, actual excavation and corresponding monitoring data indicated that the unloading mechanism and supporting measures for the shear belt presented in this study were reasonable and effective. These presented experiences can also enrich the stability analysis and support design for similar high slopes.

A Shearing Strain Model for Cylindrical Stress States

Abstract. A shearing strain model for soil was developed that includes soil behavior under compressive normal and shear stresses great enough to attain maximum compaction. The model was developed for a clay and a clay loam from triaxial data with various stress loading paths. This model relates the ratio of maximum shear stress acting on the cylindrical sample (tmax) to major principal stress (s1), to the ratio of maximum natural shearing strain to natural volumetric strain occurring after shear stress is initiated. The model accurately describes the shearing distortion of triaxial soil samples under cylindrical stress loading prior to yielding by plastic flow. This model predicts soil shearing strain for input stress states that realistically represent field conditions. Keywords: Principal stress and strain, Shearing strain, Shear stress, Soil compaction, Soil parameters, Triaxial tests.

Hypothesis of orogenesis

The mechanism of mountain forming is based on the phenomenon of the formation of compressive normal horizontal stresses exceeding gravitational. These stresses are due to contact friction between the layers of rocks. To reveal the mechanism of mountain forming, the vector method of the body equilibrium on the path of maximum effective tangential stresses of a triangular element is used, taking into account the external and internal forces acting on it. It is shown that the total vector of these forces, taking into account internal and contact friction, is directed against the gravitational force and generates mountain forming. A generalization of experimental observations on the elevation of rock structures and anomalous manifestations of rock pressure is given.

The Dinevar transtensional pull-apart basin, NW Zagros Mountains, Iran: a geological study and comparison to 2D finite element elastic models

The Dinevar transtensional pull-apart basin is a NW–SE trending basin located in the northwest part of the Zagros Mountains, Sanandaj–Sirjan tectonic zone, Iran. This basin was formed by oblique extension in a strike-slip fault system, which was controlled by the pre-existing Sahneh and the Mianrahan faults. In addition to a field study, we constructed a 2D finite element elastic model based on the major fault segments. According to the field study, various geological structures are formed around the pre-existing fault segments, including pencil structures with 13 < aspect ratio < 19, tight to open asymmetric folds, oblique–normal faults, synthetic and antithetic faults, normal and reverse fault drags, and negative and hybrid-type flower structure. FE-model results show that around the fault step is a zone of displacement gradient that indicates extension (transtension) within the overlapping zone. Consequently, subsidence is predicted over the releasing fault step. The modelled stress distributions within the fault step and around the fault segment tips are asymmetric. Elastic modelling shows that the mean normal stress within the step is tensional, which would impede plastic yield, while the region outside the step is characterised by compressive mean normal stress. The mean normal stress pattern is characterised by a regional minimum, localised inside the extensional step (transtension zone), and two local maximum and minimum couples, formed at the advancing and retreating sides, respectively, in the fault segment tips. The results show that two main subsidence regions (depocentres or sub-basins) form along and in the proximity of the fault segment tips. The imposed relative motion is entirely accommodated by creep on the faults, which causes plastic strain to accumulate outside the faults, mostly localised within the fault step. This localised strain between fault segments could initiate connecting faults or reactivate earlier faults, generally at high angles relative to the master fault segments as suggested by the stress and strain patterns. The rotation and magnitude variation in the stress and strain trajectories reflects heterogeneous deformation. In general, the Dinevar transtensional pull-apart basin is characterised by an elongate rhomboidal- to trapezoidal-shaped geometry. The modelled stress distribution and strain localisations within the basin are in general agreement with the locations of fault segments within the Dinevar transtensional pull-apart basin.

Decreasing the shear stress-induced in-plane molecular alignment by unprecedented stereolithographic delay in three-dimensional printing

The shear stress-induced in-plane molecular alignment in 3D printed polymer is decreased with an increased stereolithographic delay. The molecular alignment represented by the through-thickness (perpendicular to the layers) permittivity (100 Hz) is reduced by 39% to approach that of the bulk polymer. Consequently, the through-thickness piezoelectric coupling coefficient is decreased by 27%. Two types of resins (Resin 1, acrylate ester resin, viscosity 95 cP; Resin 2, methacrylate resin, viscosity 2950 cP) that differ in the viscosity are used for the synthesis of 3D printed components. Resin 2 experiences higher values of the shear stress, resulting in more molecular alignment. During the period of the delay, molecular orientation randomization occurs and is more sluggish for Resin 2. The degree of molecular alignment is more pronounced for 3D printed components with smaller layer thickness (25–50 μm), as the shear stress experienced is higher. The proposed analytical model predicted that the shear stress responsible for the molecular alignment for the component with a layer thickness of 25 μm and a platform speed of 3 mm/s is 38 and 1200 kPa for Resins 1 and 2, respectively. The corresponding peak normal compressive stress (unprecedentedly measured) is 5.6 and 22 kPa, respectively. Moreover, the stress increases abruptly as the piston approaches its lowest position and decreases after reaching the peak stress. The rate of stress decrease is more pronounced for Resin 1.

Susceptibility for extrusion welding of AlMg alloys

The extrusion of hollow profiles from high strength aluminium alloys through porthole dies causes serious problem in practice. Mainly, this is due to low weldability of these alloys and high extrusion force. The present paper discusses the investigations undertaken to determine the weldability of hard AlMg alloys using the original method and device. Main advantage of the proposed method is that it allows for the reflection of real welding conditions occurring in a welding chamber of the porthole die. Weldability tests were performed for alloys: 5754 (3.5% Mg), 5083 (4.5% Mg), 5019 (5.6% Mg) and 5xxx (7.1% Mg) in a wide range of temperature, unit pressure (normal compressive stress) and duration of welding. Microstructure and strength properties of the welds were examined. Most favourable welding conditions for the tested alloys, allowing for obtaining high strength welds were defined. To validate the laboratory experiments the extrusion trials were performed in the industrial conditions, in which the round tubes from 5754 alloy were produced using the porthole dies. The tensile strength of the welds in the extruded tubes is comparable to that for the solid material. Strength of the welds as well as of the solid material strongly increases with magnesium content in the alloy.

Influence of permeability anisotropy on heat transfer and permeability evolution in geothermal reservoir

Extracting heat energy from geothermal reservoirs essentially relies on circulating cold fluid within fractured hot rocks. The intrinsic anisotropic permeability in the reservoir directly affects the path of flow and the associated thermal drawdown from cooling procedure. Consequently, each individual component including thermal, hydraulic, and mechanical field needs to be considered, to evaluate the influence of permeability anisotropy on the thermal production and evolution of rock properties. In this work, the fully implicit coupled simulator TFReact was successfully implemented to generate results prototypical of an enhanced geothermal system. Anisotropic permeability values were generated from the variation of fracture spacing at three orthogonal principal directions, with identical initial fracture aperture. Five case scenarios of permeability anisotropy were simulated to evaluate the influence of anisotropic thermal drawdown in triggering permeability evolution. Analysis of the propagation of the thermal front from injector to producer indicated that low anisotropic permeability values will lead to late cold water breakthrough at producer, slower migration rate and wider sweep area than high anisotropic permeability values. Isotropic permeability scenario showed a lower thermal gradient profile, comparing against the scenarios of anisotropic permeability. The anisotropic value of 0.01 produced the highest power output, while isotropic permeability generated the least power output. Induced thermal stress resulted an unloading response by reducing compressive normal stress in sub-horizontal direction, and thereby increase fracture aperture in sub-horizontal direction. Invariably, the induced thermal expansion stress increased the compressive stress and reduced fracture aperture and permeability. After the same timing of injection-production cycle, the highest anisotropic permeability scenario resulted a factor of 2.5 increment in evolving fracture permeability, while lowest anisotropic permeability scenario lead to a factor of 0.35 decrease in changing fracture permeability. The generated thermal output suggested the most favorable strategy in maximizing thermal sweep across the reservoir, by prompting thermal transfer normal to direction of injector-producer.

2D finite-element elastic models of transtensional pull-apart basins

A set of two-dimensional finite-element elastic models are presented to provide insights on the evolution of transtensional pull-apart basins between two right-stepping, right-lateral fault segments. Three representative fault segment interaction geometries are modelled, showing underlapping, neutral and overlapping segments. Despite the simplifications of the 2D model, overall results are obtained that might help understanding the formation of pull-apart basins. Firstly, the orientations of the local σ1 and σ3 tensional stress directions markedly depend on the segment's position. Secondly, the mean normal stress is extensional in a transtensional basin between segments, while the region outside the step is characterized by more compressive mean normal stresses. Thirdly, the angle of offset between the fault segments is one of the most important parameters controlling the geometries of the transtensional pull-apart basins: connected depocenters with basin high and lozenge shape in the case of underlapping steps, spindle shape or lazy S or Z shape in the case of neutral steps, and broadly elongate rhomboidal to sigmoidal basins in the case of overlapping steps. Generally, en-échelon basin margin system, dual opposing asymmetric depocenter, intrabasin relative structural high, and wide basin width can be used as indicators that a pull-apart basin is developing in transtension zones.

Model of heterogeneous reinforced fiber foam concrete in bending

The paper considers a model of heterogeneous reinforced fiber foam concrete, given the bimodule in the elastic formulation. Based on the proposed model the analysis of stress-strain state of an I-beam of reinforced fiber foam concrete, arbitrarily supported and loaded arbitrarily. The dependence of maximum stress on the number of rods and their location in the compressed and stretched zones. The neutral line does not coincide with the main central axis in the bimodule materials, then the values of the maximum normal stresses also vary depending on the elastic moduli relations for tension and compression. This allows us to reasonably regulate the structural features of beams when the properties of fibrous concrete are taking into account. The value of the maximum normal stresses is compared with and without the bimodule material of the beam, from which it follows that the design load capacity of the beam increases with the bimodulity of the material taken into account. The magnitude of the maximum normal stresses in reinforced beams made of concrete of a cohesive structure with allowance for bimodulity was numerically investigated. It has been established that the normal tensile stress arising in a fiber-reinforced concrete beam is higher than in a beam of concrete of a fused structure by 42%. The value of the normal compressive stress is lower by an average of 38%.

Detailed micro-modelling of the direct shear tests of brick masonry specimens: The role of dilatancy

The mechanical parameters (shear strength of bed joints) derived from triplet tests can apparently be significantly different from those obtained through the so called “shove test” procedure executed on the same type of masonry. It was observed that this discrepancy may be caused by a wrong estimation of the compressive stress in the bed joints of the shove test. This article describes a numerical technique implemented in Abaqus to provide a sound interpretation of the phenomena involved in the failure of a mortar bed joint. The level of accuracy required to accomplish the objectives of the present study has driven the attention toward the detailed micro-modelling approach. Units and mortar joints have been modelled with continuum elements whereas the cohesive interfaces with zero thickness have been used for the unit-mortar interfaces. The material nonlinearities of masonry have been attributed to mortar and unit-mortar interfaces. The dilatancy of the bed joint during the shear failure process can generate, under certain boundary conditions, a local increase of the normal compression stress. Hence, particular attention has been dedicated to the modelling of this phenomenon. Several triplet tests and shove tests have been used as experimental benchmark for the numerical simulations. With the aim to accurately calibrate the parameter that controls the dilatancy, this work has paid attention also to the numerical-experimental comparison in terms of normal expansion of the joints, whereas commonly the comparison is generally carried out only in terms of shear stress-displacement curve. With the proposed technique, the triplet test and the shove test can be simulated with great accuracy. Thanks to these features, it has been also possible to relate the two types of test by highlighting the factors that affect the local normal stress during the shear failure process, providing a more detailed explanation of why and how the shove test results must be carefully interpreted in order to derive a realistic estimate of the shear strength of bed joints.