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To design a steel shear wall, dynamics of stress concentration on the columns and beam under lateral loads is essential. Therefore, it has been suggested that the thickness of plates should be reduced as much as possible. In cases where a plate with low thickness is not available, this is compensated by using either low-yield-stress plate or by preparing some holes in the structure. Two objectives are pursued in this study, namely, the formulation of a new time integration method for evaluating structural seismic behaviour, and to discover the influences of the yield strength of the steel plate and openings on the wall. The results obtained indicate that the proposed scheme can accurately assess the seismic performance of structures. In addition, in the shear wall with low yield stress, where the steel plate has 5% and 10% openings, there are no significant differences between the outputs of widespread and concentrated openings. The behaviours of these two kinds of shear walls are approximately the same.

Vibroflotation is an established ground improvement technique for granular materials. It densifies loose sands by means of shear and compressive deformation processes imparted by the horizontal vibrations of a vibrator probe at the required soil depth. The field experience and empirical relations used for the design of vibroflotation processes prompt further study and analysis. Numerical simulations of the method help provide insight into the process. A coupled Eulerian–Lagrangian framework was used to model the compaction process. The compaction process was modelled based on the pilgrim step method for a depth range from 25 m to 10 m. A hypoplastic constitutive model was used to characterise the stress–strain behaviour of the fine sand. Numerical results were validated against in-field cone penetration test measurements made before and after the compaction of fine sand in east Germany. The validation was followed by a parametric study in which the following were evaluated in terms of their effects on the extent and degree of compaction: frequency, relative density, shape of vibrator, spacing of compaction points, nature of compaction process and type of sand.

To study the effect of steel corrosion on the shear resistance of new shear connectors, push-out tests were carried out on three groups of six discontinuous perfobond rib shear connectors with different corrosion ratios. After testing, the displacement, strain distribution, crack development and relative slip between concrete and steel were assessed. Based on the experimental work, the effects of corrosion of perfobond ribs and transverse rebars on the shear resistance of the connectors were studied using finite-element models. The results showed that when the corrosion ratio was low, the corrosion of the perfobond rib increased the cohesion between the steel and the concrete, thereby improving the initial stiffness and ultimate bearing capacity (UBC) of the structure. With an increase in the corrosion ratio, expansion cracks on the joint surface led to bonding failure between the steel and concrete and the shear resistance of the structure was greatly reduced. When the corrosion ratio of the transverse rebars was 10%, the UBC of the connection decreased by only 5% and the initial stiffness hardly changed.

A series of direct simple shear (DSS) tests were carried out on a non-plastic sandy silt lead−zinc−silver tailings to develop a relationship between undrained shearing behaviour and density for contractive states. The critical state line was also obtained through triaxial compression tests to enable the DSS tests to be viewed in a critical state framework and allow comparison with in situ testing. It was found that the gravimetric water content (GWC) used to tamp the specimens had a significant effect on the resulting undrained strengths when attempting to achieve dense states — with higher GWC giving lower strength at a given density than a lower GWC. Intact and slurry deposited (SD) samples were also tested to access denser states without inducing tamping-related stresses. These showed a more consistent trend with the loose-tamped specimens, and with other data from the literature. Plausible explanations as to the causes of the increased strength of dense-tamped samples were obtained through estimating potential preconsolidation stresses and “locked in” horizontal stresses that may occur from dense tamping. The importance of these observations on the development of density−strength profiles in engineering practice was outlined.

The shear resistance of reinforced concrete beams is enhanced by arching action when loads are applied to their top face within around twice the beam effective depth (d) of the supports. Previous experimental investigations into shear enhancement have almost exclusively considered simply supported beams with a single point load applied within 2d of supports. Such academic tests are unrepresentative of practice, where loading and support conditions are usually more complex. For example, balanced cantilever cross-head girders of bridges and continuous beams can have multiple point loads applied to the flexural tension face within 2d of supports. Such cases have not previously been investigated experimentally. An experimental programme was thus carried out to investigate shear enhancement in balanced cantilever beams subjected to pairs of concentrated loads within the failing shear span. The shear resistance of the cantilever beams was found to be slightly less than matching simply supported beams, with the difference greatest for beams without shear reinforcement. A strut and tie model was developed for cantilever beams with pairs of concentrated loads applied to the tension face within 2d of the supports. Measured beam strengths were also compared with the predictions of various codes and non-linear finite-element analysis.

Progressive collapse of concrete flat slab structures is mainly governed by the structural response of the slab–column connections before and after local failure of the connections. A novel model is proposed to predict the structural response of column–slab connections after punching shear failure (post-punching shear). The proposed model considers the gradual activation and deactivation of flexural bars within and outside the punching shear cone as well as the contribution of integrity reinforcement. The model is formulated in terms of slab vertical displacements so that it can be applied to progressive collapse analyses including asymmetric cases such as in column removal scenarios commonly adopted in structural robustness design. The proposed model is validated using existing experimental data covering symmetric post-punching tests without shear reinforcement, with and without integrity reinforcement. Numerical modelling was also applied to verify the analytical model by means of three-dimensional explicit finite element modelling. Analytical and numerical models showed that asymmetric post-punching leads to a reduction of the peak post-punching strength due to an early fracture of the reinforcement whereas the residual shear strength in the connection immediately after punching can be higher in asymmetric cases.

A momentum-balance theory for the orientation of updrafts in density currents is developed for understanding squall-line–shear interactions. The motivation arises from studies showing the diagnostic limitations of the vorticity-balance theory by Rotunno et al. (1988) (RKW theory) under varying shear profiles, together with the flow-force balance constraint (FFB) which determines the shear-layer depth in optimal density currents. Considering that the FFB is derived from the horizontal momentum equation, momentum-balance concepts are explored as an alternative to RKW theory, by assuming that the updraft’s slope is determined by the balance between advective tendencies of inflowing air and the work done by pressure perturbations within the denser fluid. Density currents were simulated under diverse shear and buoyancy profiles. Results show that momentum-balance effectively diagnoses the updraft’s slope at low and mid-levels in experiments contemplating both “classic” c-ΔU variations, as well as changes to the shear and buoyancy vertical profiles. It is also found that cases with stronger system-relative inflow tend to produce deeper lifting of near-surface environmental air, notwithstanding the updraft’s slope. RKW theory’s quantitative criterion (c/ΔU) is not as effective at diagnosing the updraft’s slope nor the depth reached by near-surface parcels, although c/ΔU provides guidance for the updraft’s slope at upper levels. This result justifies a reinterpretation of c/ΔU as a measure of the impacts of wind velocities aloft on the updraft

Deformation behavior of a FeCrNi medium entropy alloy (MEA) prepared by powder metallurgy (P/M) method was investigated over a wide range of strain rates. The FeCrNi MEA exhibits high strain-hardening ability, which can be attributed to the multiple deformation mechanisms, including dislocation slip, deformation induced stacking fault and mechanical twinning. The shear localization behavior of the FeCrNi MEA was also analyzed by dynamically loading hat-shaped specimens, and the distinct adiabatic shear band cannot be observed until the shear strain reaches ~14.5. The microstructures within and outside the shear band exhibit different characteristics: the grains near the shear band are severely elongated and significantly refined by dislocation slip and twinning; inside the shear band, the initial coarse grains completely disappear, and transform into recrystallized ultrafine equiaxed grains by the classical rotational dynamic recrystallization mechanism. Moreover, microvoids preferentially nucleate in the central areas of the shear band where the temperature is very high and the shear stress is highly concentrated. These microvoids will coalesce into microcracks with the increase of strain, which eventually leads to the fracture of the shear band.

Geopolymer is an eco-friendly material used as an alternative to Portland cement and it can be used in construction practices as a repair material to concrete/as a structural element in construction/ as a whole. This study was mainly intended to understand the efficiency of geopolymers in the structural system when special concretes are involved in construction. Shear bond strength was evaluated for the combination of self compacting geopolymer concrete (SCGC) and normal self compacting concrete (SCC). SCGC was developed under external exposure curing conditions enabling it to be used in cast-in-situ production. This was achieved by binary blending of mineral admixtures, use of activator solutions, and superplasticizer. Comparative study on two types of push-off tests namely (1) Conventional Push-off test (Type 1) and (2) Push-off test with normal load acting over the shear interface (Type 2) were conducted to evaluate the interface shear strength. Test results were compared with selected shear friction models available from literature and the effect of introducing self compacting geopolymer concrete in composite interfaces were analyzed.

An analytical study on the compression, tension and shear strengths of concrete and corresponding size effect is conducted using the meso-scale finite-element method (FEM). Prior to the analysis, a method of defining concrete as a meso-scale composite and multi-phase is described. The concrete is assumed to be a composite with three phases: aggregates, cement matrix and interfacial transition zone. The material properties of each phase are applied. Behaviours relating to uniaxial and flexural compressive failure, splitting and direct tensile failure of concrete, and shear failure of reinforced concrete are analysed using the model constructed; the size effect is confirmed through these analyses. The performance of the analytical models is also evaluated by comparing experimental with analytical results. Finally, it is confirmed that the application of the meso-scale size analysis model is enough when studying the occurrence and progress of tensile cracks. This basic study represents a fresh application of meso-scale FEM analysis to concrete; in future research, the authors will apply meso-scale FEM analysis in a wider variety of fields.

Strike-slip faults, proven to be closely linked to hydrocarbon migration and accumulation, are widespread in the Tarim Basin Craton. Deformation patterns in the eastern part of the Central Uplift Belt of the Tarim Basin are analyzed in detail to understand the deformation model and genetic mechanism of strike-slip faults, how their patterns impact reservoir formation and influence oil and gas potential. Regional tectonic events are taken into consideration to identify the primary factors that controlled the development of strike-slip faults in the region. The Tazhong Uplift in the eastern part of Central Uplift Belt is believed to be a complex anticlinal uplift formed by compression-and-torsion acting on the Cambrian – Middle Ordovician platform during the middle–late Caledonian period. Multi-stage development of this north-trending fault–fold belt and the NE-trending strike-slip faults make it structurally complex. The NE-trending Paleozoic strike-slip faults were formed jointly by the differential thrusting of the Tazhong Uplift along Fault No. I and the NE-trending shear sliding of the basal fault blocks during the middle–late Caledonian – early Hercynian. Based on the distribution of effective source rocks, the tectonic setting during the period critical to hydrocarbon accumulation, and the distribution of conductive faults, the northern slope of the Tazhong Uplift— especially its west-central part where the NE-trending faults are developed is not only located close to the northern hydrocarbon source rock area but also possesses conditions suitable for the development of carbonate reservoirs. In addition, the NE-trending faults provide passage for initial development of the reservoir and the subsequent migration of oil and gas from the Aman area to the uplifted zone, making the Tazhong Uplift an extremely favorable area for oil and gas accumulation with substantial potential for exploration.

Landslide is a commonly occurring natural disaster and also a societal hazard in the world. Rainfall is considered as one of the major triggering factors for cause of landslide slope failures. In the present study, a constitutive model is proposed and analyzed using mathematical theory, which deals better with geomorphic changes causing landslides. The constitutive behavior of soil is characterized along the planar shear plane and comprised of different soil properties with different strength parameters. The stiffness parameter of the soil along the shearing plane is analyzed to study the effect of infiltration and seepage of rainfall. The impact of water seepage on the stability analysis of landslide were discussed with importance. The present study shows the results that rainfall infiltration on the slope and the difference in the water level can tremendously influence the stability of landslide.

Fracture patterns induced by supercritical-water fracturing show complex fracture networks with branched and isolated fractures. Such fracture patterns are expected to effectively increase permeability and significantly improve the heat exchange surface area. We clarify the mechanism of complex fracture induced by supercritical water using a coupled model and discuss the performance of the supercritical-water fracturing under geothermal environments. The numerical approaches to the coupled model are the pore-scale network method and finite element method with cohesive elements. Supercritical-water fracturing in granite at the laboratory scale was simulated and compared with the experimental results. The simulation results of fracture patterns are in good agreement with the experimental results. The results suggest that low viscosity of supercritical water leads to a strong seepage effect in granite, which reduces the effective stress over a wide area and makes it easier for shear failures to occur. We also found that differential stress and large confining stress induce more complex cloud-fracture networks. Our results clearly show that fracturing with supercritical water is effective not only for the geothermal resources that are considered so far but also for the development of the area at even deeper depths, which can contribute a leap forward in geothermal development.

Fluid pressurization within the fault zone generates increasing pore pressure and stress change which is liable to create shear and/or brittle fractures within the reservoir volumes and subsequently generating earthquakes of varying magnitudes. Here, we explored time-dependent fault weakening processes in the fault zone which are dependent on several factors, including the rate of cold-water injection, modes of injection (hydromechanical (HM) and thermo-hydro-mechanical (THM) interactions), and changing fault spatial configurations using data from Niger Delta Basin. The variation in the stability of different fault models in withstanding stresses induced by HM and THM fluid interactions is evident. Fault permeability enhancement and the behaviour of slip event under isothermal and non-isothermal conditions revealed that stress and pore pressure perturbations have a first order control on the rate of fault dilation and compression. It is observed that the progressive cooling of the reservoir induced thermal stress which induced the timing of slip by unloading the fault to earlier seismic rupture in the non-isothermal case, and accelerates the magnitude of the fault reactivation and the accompanied induced seismicity. Owing to increased tendency of shear failure during injection, fracture opening through shear dilation is more enhanced in THM simulation as the fracture permeability is significantly higher than in HM. This effect becomes increasingly more dominant with intermediate fault angle and joint orientation. Certain fault/joint configurations which were resistant to shear failure under isothermal injection had their frictional resistance broken by thermal stress. The results also indicate that there is higher pore pressure build-up in THM than in HM as the injection rate increases and reservoir temperature drops during cold injections.. This study has demonstrated the importance of fully characterizing the fracture geometries and configurations of normal faulting regime in addition to fluid injection conditions when developing fractured reservoirs to mitigate seismic risks and hazards that could result from early fault reactivation.

This paper presents the results of a study focused on evaluating the seismic performance of school buildings located in a region of high seismicity in the Pacific Coast of Mexico. For this purpose, a family of three archetype school buildings having typical plan view with one-, two-, and three-story height were designed with out-of-date 1990s seismic requirements. Detailed analytical models representative of the archetype school buildings included modelling the nonlinear behaviour of captive reinforced concrete (RC) columns and the adjacent partial-height infill masonry walls commonly found in this type of structures. The analytical models were subjected to a set of 22 as-recorded mainshock-aftershock seismic sequences gathered at stations placed on the subduction zone of the Mexican Pacific Coast. Drift-based fragility curves for captive RC columns failing in shear, which represent the probability of reaching or exceeding four damage states, based on experimental tests are introduced in this study for evaluating their seismic performance. This investigation revealed that the two- and three-story school buildings exhibit larger inter drift demands at the ground story than those exhibited by the one-storey school building, which led to a weak first-storey mechanism under some mainshock earthquake ground motions. Furthermore, it was noted that aftershocks increased the state of damage at the ground storey due to the increase of damage in the captive RC columns. Findings of this investigation highlight the priority of implementing retrofit strategies, mainly for three-storey school buildings.

Felsic rocks of the Erzgebirge in the Central European Variscides experienced ultra-high pressure metamorphism at ∼340 Ma, followed by nearly isothermal decompression during channel like rapid exhumation within ∼10 Ma. Despite the general time frame of exhumation and emplacement within mid-crustal levels is known, available geochronological data do not provide a detailed timescale of individual stages of the entire process. Addressing this problem we combined white mica 40Ar/39Ar ages obtained from multi-grain step heating and multiple single grain total fusion experiments with mineral chemical, structural and tectono-metamorphic constraints. Gneisses of the channel center are characterized by E-W elongated white mica exclusively aligned in the continuous foliation. The rocks of the channel contact zone and in the hanging and footwall contain NW-SE stretched white mica parallel to the foliation, but also components of ductile to brittle-ductile shear bands truncating the main foliation. Well defined weighted plateau ages of all samples range between 340.0 ± 1.1 Ma and 327.9 ± 1.3 Ma, confirming previously published data, but represent presumably mixed ages due to multi-phase deformation. Single grain age distributions, in contrast, exhibit two statistically significant age peaks at 338.6 ± 0.2 Ma and at 332.8 ± 0.3 Ma. Rocks without shear bands exclusively contain white mica belonging to the older age fraction, whereas rocks with shear bands show a broad age scatter including both age fractions. We interpret these age distributions as being independent of closure temperature, but reflecting different dynamic recrystallization events. The older age fraction reflects the formation of the main foliation during west-directed emplacement of the ultra-high pressure rocks in mid-crustal levels at ∼339 Ma, whereas the shear band related neo- or recrystallization is responsible for the younger age fraction dating the final transport in the upper crust at ∼333 Ma.

Lubricant behaves non-Newtonian at high shear stress and high shear rate. The non-Newtonian shear behavior of oil such as shear-thinning, viscoelasticity, and limiting shear stress could have influences on almost all characteristics of an elastohydrodynamic lubrication (EHL) contact, that is, the central film thickness, the coefficient of friction, and the temperature rise in the lubricating film. For example, for lubricants of large molecular weight or of polymer blended ones, there can be inlet shear-thinning, which would reduce the EHL film thickness. For the EHL traction in a rolling/sliding EHL contact, it cannot be reasonably predicted without the consideration of non-Newtonian rheology. In EHL numerical studies, the non-Newtonian properties and the constitutive equations are expressed by the concept of generalized viscosity [Formula: see text], which can be either a function of shear rate [Formula: see text] or a function of shear stress [Formula: see text]. In this way, a non-Newtonian lubrication problem could be solved as a generalized Newtonian problem based on solvers for a Newtonian EHL problem. According to the function of the generalized viscosity [Formula: see text], numerical solutions can be classified into shear rate-based ones and shear stress-based ones. In this work, these two kinds of numerical solutions are revisited. And their efficiency is compared for a two-dimensional (2D) non-Newtonian point contact EHL problem (here 2D means non-Newtonian flow in both the x and y directions). Results show that the shear rate-based numerical solution has a higher efficiency than the shear stress-based one. The shear rate-based 2D generalized Newtonian method is more suitable to analyze multiple EHL contacts in angular contact ball bearings and gears with complex 2D flow and/or transient EHL lubrication problems.

This paper describes an investigation carried out on the behaviour of buildings with a dual lateral load-resisting system, comprising a reinforced concrete (RC) moment frame and steel plate shear walls (SPSW), subject to near-fault (NF) and far-fault (FF) earthquakes. Experimental validation of a one-bay, three-storey, RC frame with SPSWs was done using structural analysis software. The seismic performance of four buildings with various numbers of storeys was then compared using finite-element software. The non-linear dynamic behaviour of the four building was also modelled. Based on the results, it was found that the standard seismic design spectrum defined by Iranian Code of Practice for Seismic Resistant Design of Buildings does not satisfy all structural demands developed by NF earthquakes. The spectrum should be modified, especially for areas near active faults. The results also revealed that the impact of FF earthquakes on low- to mid-rise structures is more profound compared to that of NF earthquakes. Conversely, it was also found that NF earthquakes have greater impacts on taller buildings than that of the FF motions.

Large earthquakes in the Tibetan Plateau generally occur on block-boundary faults and produce coseismic surface ruptures that indicate the sense of block movement. However, seismic hazard in the block is less concerned. The Mw 7.3 Maduo earthquake on 22 May 2021 hit the internal Bayan Har block, which provides a rare opportunity to study the deformation features of the intra-block tectonics in central Tibet and related kinematics implications. We developed the high-resolution survey via the DJI drone of Phantom 4 Pro RTK and detailed field observations, to sum up the typical characteristics of the Maduo coseismic surface rupture zone. Then we classified these surface ruptures based on rupture orientation, spatial distribution, and stress state and analyzed their kinematic mechanisms. Our results indicate that (1) the typical surface ruptures of the Maduo earthquake are shear fractures, tensional cracks, and mole tracks, which follow the Riedel shear model; (2) the Riedel shear structures reveal a sinistral strike-slip movement sense for the seismogenic fault, accordant with regional tectonics; (3) seismic potential on minor faults in the interior block should be emphasized highly. This study will not provide insights into the kinematics of surface ruptures on a strike-slip fault but will strengthen the understanding of seismic hazards on an intra-block active fault.

Accurate measurement of acoustic velocities of sedimentary rocks is essential for prediction of rock elastic constants and well failure analysis during drilling operations. Direct measurement by advanced logging tools such as dipole sonic imager is not always possible. For older wells, such data are not available in most cases. Therefore, it is an alternate way to develop a reliable correlation to estimate the shear wave velocity from existing log and/or core data. The objective of this research is to investigate the nature of dependency of different reservoir parameters on the shear wave velocity (Vs) of clastic sedimentary rocks, and to identify the parameter/variable which shows the highest level of dependency. In the study, data-driven connectionist models are developed using machine learning approach of least square support vector machine (LSSVM). The coupled simulated annealing (CSA) approach is utilized to optimize the tuning and kernel parameters in the model development. The performance of the simulation-based model is evaluated using statistical parameters. It is found that the most dependency predictor variable is the compressional wave velocity, followed by the rock porosity, bulk density and shale volume in turn. A new correlation is developed to estimate Vs, which captures the most influential parameters of sedimentary rocks. The new correlation is verified and compared with existing models using measured data of sandstone, and it exhibits a minimal error and high correlation coefficient (R2 = 0.96). The hybridized LSSVM-CSA connectionist model development strategy can be applied for further analysis to predict rock mechanical properties. Additionally, the improved correlation of Vs can be adopted to estimate rock elastic constants and conduct wellbore failure analysis for safe drilling and field development decisions, reducing the exploration costs.

We present results from a natural deformed shear zone in the Turon de Técouère massif of the French Pyrenees that directly addresses the processes involved in strain localization, a topic that has been investigated for the last 40 years by structural geologists. Paleopiezometry indicates that differential stresses are variable both spatially across the zone, and temporally during exhumation. We have, however, also calculated strain rate, which remains constant despite changes in stress. This result appears to be at odds with recent experimental deformation on monophase (olivine) rocks, which indicate that strain localization occurs dominantly as a result of constant stress. We hypothesize that in the Turon de Técouère massif—and many natural shear zones—strain localization occurs as a result of reactions, which decrease the grain size and promote the activation of grain size sensitive deformation mechanisms. From a tectonics perspective, this study indicates that the deformation rate in a particular plate boundary is relatively uniform. Stress, however, varies to accommodate this deformation. This viewpoint is consistent with deformation at a plate boundary, but it is not the typical way in which we interpret strain localization.

In order to study the instantaneous mechanical properties of rock mass discontinuities with different 3D morphologies during the shear process, the Brazilian splitting method is used to prepare natural rock mass discontinuities, and the high-precision 3D scanning test of discontinuities is carried out. The Z 2 is selected as the evaluation parameter of the discontinuities. Based on the graded cyclic shear test results of discontinuities, the influence of the morphology characteristics on the strength and deformation characteristics is analyzed. With the increase of shear times, the 3D morphology characteristic parameters of the structural plane decrease steadily after the graded cyclic shear. Based on the test curve, the graded cyclic shear characteristics of rock mass discontinuities are analyzed from the shear deformation, and the shear process of the discontinuities is finely divided by combining with the variation characteristics of shear stiffness. Combined with the 3D morphology parameters, an empirical formula for the shear strength of discontinuities is proposed. Through verification, the effect of the new model is better than that of the classical JRC-JCS model.

Characterizing the subsurface structure is an important parameter for the improvement of seismic hazard assessment. Due to the tectonic complexity of the earth, some deep fractures do not reach the earth’s surface and are not detectable with visual analysis. Therefore, the lack of knowledge of faults and fractures can result in disasters, especially in urban planning. Many geophysical methods can be used to estimate subsurface structure characterization. However, a more reliable method is required to assess seismic hazards and reduce potential damage in metropolitan areas without destroying buildings and structures. This paper aims to identify hidden faults and structures using shear wave velocity sections. To do this, surface wave dispersion curve was extracted from the vertical component of microtremor array recording using the spatial autocorrelation (SPAC) method in two profiles and 13 array stations (perpendicular to the altitudes) to obtain shear wave velocity structure (Vs) in the west of Mashhad, northeast of Iran. The results of shear wave velocity profiles (Vs) indicate sudden changes in the thickness of sediments. This can be related to the displacement of a normal fault in this area causing the bottom rock to fall and an increase in the alluvial thickness in the central part of the plain. The velocity in the floor rock is 2000 meters per second in this area. According to the surface outcrops and water wells data, its material is slate and Phyllite metamorphic rocks that are exposed in the adjacent heights. Besides, the seismic profile results were well consistent with electrical resistance data and well logs indicating that the tool array method is flexible, non-invasive, relatively fast, and effective for urban areas with satisfactory accuracy.

The possibility that pressure-loaded natural fractures in naturally fractured formations may contribute to wellbore instability merits further investigation. The present study analyzes in detail the state of stress around a wellbore with pressurized natural fractures nearby. Synthetic examples are given of unanticipated well instability when pressure-loaded natural fractures occur in the vicinity of the wellbore at the time of first penetration of the naturally fractured formation. The locations of shear failure are controlled by the stress field distortion due to the fluid pressure in the natural fractures. Various shear failure criteria are used to quantify where and when the critical stress for shear is reached. Rather than shear failure, tension failure may also occur at the wellbore. For example, wellbore stability is jeopardized by unintended circulation loss when the mud load causes unexpected hydraulic fracturing during drilling operations. The method of solution is a recently developed linear superposition method (LSM) of elastic displacements. The LSM models show static solutions of the stress state, and a dynamic version of the method (TLSM) uses time-stepped superposition to model fracture propagation processes. Time-stepped solutions show how fluid pressure-loaded natural fractures near a newly drilled well may alter the fracture propagation paths. The study also includes examples of stress concentrations near boreholes prepared with slotted perforations commonly used during fracture treatment operations in both conventional and unconventional fields.

Locating the shear, or flexural, center of non-symmetric cross-sectional beams is a key element in the teaching of structural mechanics. That is, establishing the point on the plane of the cross-section where an applied load, generating a bending moment about a principal axis, results in uni-directional deflection, and no twisting. For example, in aerospace structures it is particularly important to assess the propensity of an airfoil section profile to resist bending and torsion under the action of aerodynamic forces. Cross-sections made of thin-walls, whether of open or closed form are of special practical importance and form the basis of the material in this paper. The advent of 3D-printing allows the development of tactile demonstration models based on non-trivial geometry and direct observation.

Fluid flow in fractures has the potential to drastically change the economic, environmental, and safety risks associated with a subsurface operation. This work focuses on the analysis of experimental shear fracturing and subsequent shear displacement of a shale specimen that contains multiple pre-existing natural fractures. A triaxial direct shear apparatus with concurrent µCT imaging allowed continuous monitoring of sample permeability and changes in fracture geometry during fracture creation, displacement, and changes in stress. Steady-state, low Reynolds number fluid flow simulations were used to determine the changes of each individual fracture’s hydraulic aperture due to displacement and effective stress. The development of anisotropy in the hydraulic aperture of a generated shear fracture was determined for shear displacements of 0.38, 0.74, and 2.04 mm. At high confining stress (30 MPa), shear displacement significantly reduced the hydraulic aperture of the shear fracture to below flow detectable limits and X-ray imaging resolution (23 × 23 × 23 µm3). The shear generated fracture was found to be more sensitive to changes in effective stress compared to the pre-existing natural fractures. Existing models derived from fluid flow equations accounting for stochastic fracture roughness were able to partially fit the simulated flow properties of the pre-existing fractures, but no model was found to fit the flow properties of the newly formed shear fracture. These results are the first report of simultaneous changes in the geometry and flow properties of surrounding, parallel natural fractures as a shear fracture is generated with varying stress and shear displacement conditions.

Acid rain is often formed in southwestern China. Red-bed landslides often occur and cause major social and economic losses. The shear-slip process of red-bed landslides is affected by the creep characteristics of the weak interlayers in the rock mass. Samples of red-bed soft rock with weak interlayers of mudstone in Lufeng County of the Central Yunnan Water Diversion Project were tested in shear-creep tests in an acid environment. Combining with the functional relationship between the viscoelastic modulus and the acidic environment change, a stress-acidity-strain–time model is established based on the Burgers model. The results show that the long-term strength of the red-bed soft-rock weak interlayer in a mudstone gradually decreases with the increase of acidity. The viscoelastic modulus is linearly related to acidity. Compared with the traditional Burgers model, the improved Burgers model taking into account the effect of the acidic environment provides improved accuracy in describing the shear-creep behavior of the red-bed soft-rock weak interlayers.

Hot shear-compression deformation (HSCD) of in situ TiBw/Ti6Al4V composites with network architecture was conducted at variant temperature from 1123 to 1223 K and strain rate from 10−3 to 10−1 s−1 by using shear-compression specimens (SCS). According to equivalent stress and strain curves, the activation energy was calculated to be 631.1 kJ/mol in α+β phase region. In addition, the appearance of shear bands in the gage region was a typical evidence that shear was the major deformation during HSCD. Furthermore, dynamic recovery (DRV) and dynamic recrystallization (DRX) occurred in the shear bands, resulting in a decrease in flow stress. The mechanism of DRX in α+β phase region included the continuous rotation of substructure which was attributed to continuous dynamic recrystallization (cDRX) and formation of fine equiaxed grains which experienced nucleation and growth was attributed to discontinuous dynamic recrystallization (dDRX). Additionally, the existence of TiBw could promote the process of DRX by providing high density dislocations and nucleation sites.

We have carried out a geomechanical study of three wells, one each in the Niobrara A, Niobrara C, and Codell Sandstone to investigate how the state of stress and stress variations with depth affect vertical hydraulic fracture growth and shear stimulation of preexisting fractures. We determine that the higher magnitudes of measured least principal stress values in the Niobrara A and C shales are the result of viscoplastic stress relaxation. Using a density log and a vertical transverse isotropy velocity model developed to accurately locate the microseismic events, we theoretically calculated a continuous profile of the magnitude of the least principal stress with depth. This stress profile explains the apparent vertical hydraulic fracture growth as inferred from the well-constrained depths of the associated microseismic events. Finally, we determine that because of the upward propagation of hydraulic fractures from the Niobrara C to the Niobrara A, the latter formation experienced considerably more shear stimulation, which may contribute to the greater production of oil and gas from that formation.

The behaviour of concrete reinforced with steel fibres at elevated temperatures was investigated in terms of shear deterioration. Using three different steel fibre contents (0, 40 and 80 kg/m3), 45 push-off specimens were tested at five maximum temperatures (20, 150, 300, 500 and 700°C). The main objective of the research was to investigate the effect of steel fibres on the behaviour of concrete at different maximum temperatures in terms of shear failure. The results revealed enhanced ductility and shear strength at elevated temperatures. In addition, the crack widths and crack slips were measured using linear variable differential transducers. It was found that the use of steel fibres increased the shear strength of the concrete at ambient temperature by 103% and 102% for steel fibre contents of 40 and 80 kg/m3, respectively. Although this enhancement was reduced at the high temperatures (500 and 700°C), the mixes containing fibres still had higher residual shear strengths than the plain concrete mix. The steel fibre content also affected the ductility at both ambient and high temperatures.

We analyzed the deformation behavior of Mg-Gd-Nd(-Zn)-Zr alloys under high temperature uniaxial compression, and reported two special nucleation mechanisms of dynamic recrystallization (DRX): Nucleation and expansion of DRX based on reticular shear bands (Shear band dynamic recrystallization, SBDRX) and long chain twins (Twin dynamic recrystallization, TDRX). The reticular shear bands in Mg-Gd-Nd-Zr alloy are mainly caused by the crossing of strain gradients from different directions, which is related to the high activity of pyramidal slip at high temperature. The addition of Zn makes the DRX mechanism mutate, and TDRX is dominant in Mg-Gd-Nd-Zn-Zr alloy. The nucleation of a large number of {10–12} twins is abnormal, which may be related to the decrease of I 2 stacking fault energy caused by Gd/Nd–Zn compound addition. Based on the mechanical properties and microstructure, it can be concluded that the addition of Zn can promote the DRX, reduce the deformation resistance and improve the workability.

The outrigger structural system is one of the horizontal load resisting systems. In this system the belt truss ties all the external columns on the periphery of the structure and the outriggers connect these belt trusses to the central core of the structure thus restraining the exterior columns from rotation. The shear wall was implemented to oppose lateral loads. To complete these characteristic the Outrigger & wall belt system used in the structure. In this project a G+10 Storey structure has analysed using seven different cases named as RA1 to RA7-OTB. 1 to 7 indicates single outrigger system, shear core outrigger system truss belt support system with optimized trusses, at various locations under seismic zone III. The built up area used for various case as 315 sq. m. After performing result analysis, the comparative analysis of all the cases shows that the most efficient case for the above study is Case RA4. Here for efficiency of the project, two types of optimized truss belt support which has performed well and observed as most optimized and correspondingly minimum in all the cases. Keywords: Truss wall belt support, core wall belt support, outrigger, wall belt, CSI-ETABS, multi-storey

The geotechnical classification of soils by laboratory tests is usually used to determine the class of the soil under study for its subsequent use in construction projects. The interest is certainly well displayed. Indeed, an experimental program has been developed with the aim of studying the soil in the study area. To this end, oedometric and shear tests were carried out on several soil samples in the laboratory. This made it possible to understand the “stress-strain” behavior of these soils. As a result, the presence of a silty sand soil was found that is susceptible to collapse.

Рассматривается задача об отыскании оптимальной формы отверстия в вершине трещины продольного сдвига. Искомая форма отверстия удовлетворяет условию минимальной концентрации напряжений на его контуре. Исследуется влияние отверстия оптимальной формы на торможение трещины. Дается критерий и метод решения задачи по предотвращению хрупкого разрушения тела, ослабленного прямолинейной трещиной продольного сдвига. Используется минимаксный критерий. Получено условие хрупкого разрушения. The problem of finding optimal hole shape at the tip of a longitudinal shear crack is considered. The desired hole shape satisfies the condition of the minimum stress concentration on the contour. The effect of the optimal hole shape on deceleration of a crack is studied. A criterion and solution method for the problem of preventing brittle fracture of the solid weakened by rectilinear longitudinal shear crack is given. The minimax criterion is used. The brittle fracture condition is obtained.

The purpose of this paper is to present correlation coefficients for a variety of rock types that can be used in a suitable petroelastic model (PEM). The correlation coefficients for different rock types facilitate the application of a petroelastic model in reservoir flow models. By combining the correlation coefficients and the PEM, it is possible to obtain low-cost estimates of reservoir geophysical attributes. The rock types include dolomite, limestone, high porosity sandstone, poorly consolidated sandstone, tight gas sandstone, and well consolidated Gulf Coast sandstone.

The deformation process and failure mechanism of rock mass with increased joint roughness subjected to unconfined compression are investigated in this study using discrete element method. A numerical model is developed using soft-bonded particle and validated to realistically replicate the mechanical response of the rock mass. The micro-parameters of the rock material are first determined, and the effects of the joint roughness on the macromechanical response and fracture growth mechanism are then investigated. Analyses are also performed to examine the tensile and shear crack distributions, acoustic emission (AE) characteristics, coordination number, and crack anisotropy to advance the current understanding of the role of joint roughness on the mechanical behavior and deformability of rock mass. The results show that strength and deformability of the jointed rocks are highly dependent on the joint orientation and roughness. Joint roughness is found to restrain the propagation and coalescence of microcracks and AE events from the interlocking of asperities. In addition, the spatial distribution of the contact forces allows for better understanding of the effect of joint inclination angle on the response of the investigated rock samples.

Fractures in Cretaceous and early Tertiary strata record several deformation events that were imposed on the formations that fill the Raton Basin in Colorado and New Mexico. A regional, generally WNW-ESE striking extension-fracture set is present across much of the basin, but fracturing also includes both dip-slip and strike-slip conjugate shear-fracture sets as well as irregular deformation-band shear fractures. In some areas of the basin, the extension fractures are dynamically-compatible with associated conjugate shear fractures, both recording a maximum compressive stress that was horizontal, trending predominantly WNW-ESE. Fracture strikes vary from NW-SE to ENE-WSW but are approximately normal to the front of the Laramide thrust-fault system that forms the western edge of the basin, implying that fracturing was the result of a horizontal compressive stress anisotropy created by indentation of the thrust system into the basin margin. Fracture anomalies occur over local structures including a N-S basement wrench-fault system that connects two large anticlines within the basin, the Tercio and Vermejo Park anticlines, where N-S strike-slip offset along the basement wrench faults caused folding and fracturing in the overlying strata. The Laramide stress system in the basin changed from thrust-related WNW-ESE horizontal compression to the present-day N-S maximum horizontal compressive stress in mid-Tertiary time as the thrust system became inactive and was replaced by regional E-W extension. No new fracture sets were formed by the re-oriented stress system, although stress-release fractures normal to the regional set formed in outcrops as overlying strata were eroded. Fracture datasets were derived from three sources during this study: outcrops, image logs, and cores. Each source provides a somewhat different perspective on the fractures that enhance permeability in Raton Basin reservoirs. Taken together, the three datasets provide the basis for a relatively complete conceptual model of the Raton fracture system. Fracture-controlled permeability anisotropy will be greatest in the WNW-ESE direction, parallel to the strike of the dominant set of Laramide-age natural fractures, but hydraulic stimulation fractures will propagate N-S, across the strike of those fractures under the influence of the present-day stress system. The apertures of the WNW-ESE fractures will be susceptible to closure under that stress system since the maximum horizontal compressive stress is approximately normal to fracture strike.

Shear wave birefringence is a robust tool to infer the direction and strength of deformation in the lithosphere and sub-lithospheric mantle. Situated at the north-eastern flank of the Indian subcontinent, the Shillong plateau shows evidence of pop-up dynamics. It is bounded by major geologic structures from all the four corners. The present study presents new results from shear wave splitting using SKS, SKKS and PKS phases. A total of 749 waveforms were analysed to produce 129 high-quality splitting measurements. The delay time makes a distinctive variation in different parts of the plateau ranging from 0.4 to 2.4 s, while the trend of fast polarization direction (FPD) ranges from NE–SW to E–W along a north-south traverse. Shear at the base of the lithosphere due to absolute plate motion (APM) related strain of Indian plate explains the NE–SW (45 $$^\circ$$ ) directed deformation beneath the northern and central Shillong plateau. Situated away from the Indo-Eurasian collisional tectonics, the present deformation behaviour at the northern and central Shillong plateau mass are parallel to the APM of the Indian plate in a no net rotation reference frame, ruling out the possibility of compressional tectonics and major geological features in influencing the anisotropic pattern in this particular region. Contrary to other parts, the southern proximity of Shillong plateau displays a complex anisotropic behaviour and deformation parallel to the extension of Dauki fault. The transpressional tectonics along with coherent lithospheric deformation are supposed to be more active for an E–W aligned anisotropic behavior, though a possible attribution due to overthrusting and eastward lateral motion of the Indo-Burma fold belt may not be avoided.

Buried depth is an important factor affecting the deformation and failure of gob surrounding rock. Basing on triaxial compression unloading test and acoustic emission (AE) of limestone under three different initial confining pressures (5 MPa, 10 MPa, and 20 MPa) and three different stress paths, we analyzed the deformation and failure characteristics and energy releasing process of the virgin rock, the gob overburden rock, and the gob sidewall rock with different buried depths (within 1000 m). The results showed that, with the increase of buried depth, the shear fracture mainly propagated and the failure mode of the gob sidewall rock changed from brittleness to plasticity; however, the gob overburden rock was all brittle failure. Compared with shallow buried depths, the energy releasing triggered by confining pressure reduction in deep buried depths was more concentrated and intense. Under the background of deep buried depths, the peak strength and residual strength of the gob sidewall rock were the lowest, and the damage variable was the largest. We proposed that the first “acute phase” of AE can be wielded as the precursor information of the gob sidewall rock failure and crack propagation of hydraulic fracturing. The findings of the study are beneficial for the disaster prevention and control of deep mining in mountainous area, as well as fracturing evaluation.

Interlayer shear weakness zone (ISWZ) is a type of weak deformation zone in stratified rock masses with variable thicknesses and undulations, which is a major threat for many rock engineering construction projects on or within rock masses because of their poor mechanical properties and large-scale distributions. Existing studies mainly focused on the shear behaviours of weak interlayers of ISWZs without considering the effects of variable thickness and undulation. This study investigates the real occurrence of ISWZs located in the Baihetan Hydropower Station, and a metre-level 2D numerical geological model containing variable thickness and undulation of ISWZ was developed using the particle flow code PFC2D. A series of numerical direct shear tests were performed to investigate the shear properties of ISWZs considering the infilling ratios, joint roughness coefficient (JRC), and normal stress. The experimental results show that the infilling ratio is a vital parameter that controls the failure modes, shear strength, and shear dilatancy of ISWZs. The dilatancy and interlayer separation were found insignificant under high normal stresses compared to the cases under lower normal stresses. In case of first-order asperities, wear/striation mode failure changed to shearing off mode gradually with an increase in normal stresses. The role of structural surface asperities in shear resistance decreases with normal stress and infilling ratios. The second-order asperities tend to increase the dilatancy phenomenon if the infilling ratio is limited as well as the normal stress. The uniqueness and major finding of this study were discussed in detail. The results of this study will provide a new basis to investigate the shear properties of ISWZs at an engineering scale.

Existing reinforced concrete (RC) beam–column joints, which are designed mainly to resist gravity load, may encounter serious problems in low to moderate seismic regions. The moderate earthquake in Ranau, Malaysia, affected numerous old buildings, mainly manifesting as uncontrolled crack propagation in RC members at the beam–column joint. Effects of shear reinforcement between shear link spacing on crack formation on four RC beam–column joints were investigated under cyclic lateral loading with acoustic emission (AE) monitoring. The control specimen (BCJ-1), which was designed in BS-8110, showed more irregular cracks thus concrete cover spall was observed at an earlier drift ratio (DR) level than for other specimens with additional shear reinforcement between shear link spacing. Sudden drop of AE hits beyond 2.25% DR level with a significant increase in crack width showed that BCJ-1 was no longer able to resist higher loads due to de-bonding between reinforcement and concrete. From the rise time/amplitude against average frequency (RA-AF) graphs, the mode of failure was determined according to DR stages concerning crack characteristics.

The Litang fault is a left-lateral secondary shear zone in the Sichuan-Yunnan active block that accommodates the tectonic deformation associated with the eastward extrusion of the upper crust of the Tibetan Plateau. Based on 1: 50 000 geological mapping of active faults, the Litang fault consists of three geometric segments, the Cuopuhu, Damaoyaba, and Litang segments, in the west of Litang, which are divided by the of Haizi Mountain uplift and the wide-angle bending and branching of the fault near Jinchanggou. This study also identifies the surface rupture of the A.D. 1890 earthquake, which is distributed intermittently along the ∼28 km long Damaoyaba segments and ∼25 km long Litang segments. The maximum horizontal displacement is 4.1 m along Damaoyaba segments, and 4 m along Litang segments. The rupture involves typical left-lateral shear movement. The two ruptures are divided by discontinuous segments or gaps that are ∼18 km long; thus, the total surface rupture is approximately 71 km long. The estimated moment magnitude was Mw7.3±0.1. A comprehensive analysis of data obtained from 5 trenches excavated along the Damaoyaba and Litang segments and the trench data by Xu et al. (2005) identifies age constraints of the 4 most recent paleoseimic events occurred B.C. 1468±54–1340±25, B.C. 52±25–A.D. 76±47, A.D. 1115±90, and A.D. 1890, respectively. The recurrence intervals are 1 415±80, 1 104±104, and 775±90 a, which are consistent with quasi-periodic earthquake recurrence behavior. The average recurrence interval is 1 098±112 a.

The influence of closed and open surface flaws on the stress distribution and failure in rock specimens is investigated. Heterogeneous finite element models are developed to simulate the compression tests on flawed rock specimens. The simulated specimens include those with closed flaws and those with open flaws on the surface. Systematic analyses are conducted to investigate the influences of the flaw inclination, friction coefficient and the confining stress on failure behavior. Numerical results show significant differences in the stress, displacement, and failure behavior of the closed and open flaws when they are subjected to pure compression; however, their behaviors under shear and tensile loads are similar. According to the results, when compression is the dominant mode of stress applied to the flaw surface, an open flaw may play a destressing role in the rock and relocate the stress concentration and failure zones. The presented results in this article suggest that failure at the rock surface may be managed in a favorable manner by fabricating open flaws on the rock surface. The insights gained from this research can be helpful in managing failure at the boundaries of rock structures.

On August 21, 2017, the volcanic island of Ischia was struck by a Mw 3.9 (http://cnt.rm.ingv.it/event/16796811) earthquake which caused two victims and heavy damages on wide portions of the Casamicciola Terme, Lacco Ameno and Forio municipalities. Following the Decree 1/2018 of the Government Commission for the reconstruction of damaged areas of Ischia Island, a Grade 3 Seismic Microzonation study was committed by each municipality to private consultants, who were scientifically supported by a multidisciplinary team of geologists, geophysicists and geotechnical engineers from CNR, INGV and University of Naples "Federico II". The existing data from previous geological and geotechnical investigations were integrated with the results of new geo-lithological surveys and geophysical measurements (HVSR, MASW, Down hole tests) carried out by the consultants. The whole amount of data was quality checked, homogenized and collected in a SQLite/SpatiaLite geodatabase using a QGIS open source software by the support team. A geo-lithological map of northern and western sides of the island was then produced, and the results of routine geophysical tests were coupled with those of seismic 2D ambient vibration arrays, to obtain shear wave velocity profiles (several hundreds of meters deep) down to the seismic bedrock, made of lithic tuffs and lavas, and to define its buried morphology. This in turn enabled to draw a map of seismically homogeneous microzones of the entire study area. Cyclic torsional shear tests were carried out on 10 undisturbed soil samples, mainly taken from epiclastic cover deposits, to characterize their non-linear behavior to be adopted for seismic response analyses. These latter were carried out along 1D profiles characterizing each microzone and along selected 2D cross sections running from the Mount Epomeo to the coast. The dynamic analyses allowed to detect and map areas characterized by variable amplification factors, of spectral accelerations throughout different ranges of periods (0.1-0.5s, 04.-0.8s, 0.7-1.1 s). The zones most prone to site amplification are those corresponding to localized graben-like depressions at the toe of Mount Epomeo, such as Maio neighborhood of Casamicciola, where thickened epiclastic covers are entrenched into blocks of uplifted bedrock and where a combination of 1D stratigraphic amplification and 2D reflection and diffraction effects is expected.