Sudden Slip Research Articles

Wheel Speed Effect on Transient Lateral Force and Its Characterization by Ramp-Step Steer Test Method

ABSTRACT The concept “relaxation length” serves as one of several ways to characterize the transient lateral response for a rolling tire. Most test methods developed to identify relaxation length tightly link to Pacejka’s single-contact-point linear transient model. Its underlying assumption is that the traveled distance during the transition interval is always a constant regardless of the wheels’ linear rolling speed. The current research provides physical data against this strong assumption. The data is acquired through a newly-developed test method named the “ramp-step steer method”. The ramp-step steer method features a nonstop, high rolling speed, and fast-changing slip angle procedure that cannot be fulfilled by the conventional “start-stop-resume” step steer method. Thanks to the high dynamic capability of the equipment in GCAPS Corp., the proposed test method becomes feasible. A novel data postprocessing scheme accompanies the test method as well. The ramp-step steer method is independent of any specific models and replicates the scenario of a rolling tire subjected to a sudden slip angle change from on-vehicle to an indoor environment. The wheel speed effect on the tires’ transient lateral response is reflected through a proposed quantity, Ly, which is a more general descriptor and can downscale to relaxation length under specific circumstances. Ly itself does not associate with any model, so the remaining study explains the speed effect through an updated model. The present research aims to provide a better way of characterizing tires’ lateral transient behavior and is not an alternative to identify the key parameter “relaxation length” in Pacejka’s model. Another contribution of the research is categorizing and separating the hierarchy of various transient tire models.

Extraction of transient signal from GPS position time series by employing ICA

Transient deformation, such as post-seismic slip, slow slip and pre-seismic slip events, is a limited low-frequency deformation that can last for hours to months, in contrast to a sudden slip on a fault caused by earthquakes. Continuous Global Positioning System (CGPS), one of the most common geodetic techniques for continuously monitoring crustal deformation, is capable of capturing transient deformation signals. A critical point in characterizing transient deformation signals is the development of extracting and deciphering transient deformation signals from a huge and messy data set of position time series. Principal Component Analysis (PCA), one of the data-driven methods, has been employed to derive transient deformation signals from position time series combing with Kalman filtering. Independent Component Analysis (ICA) performs well in recovering and separating the sources of observed data, however, it is rarely used in extracting transient deformation signals. We aim to decompose the transient deformation signals from the daily GPS observation deployed in Akutan Island from 2007 to 2015 with the ICA method and obtain the spatiotemporal responses to the source signals of transient deformation. Our results indicate that ICA method can also characterize effectively transient deformation signals spatially and temporally. Additionally, the independent relationship between sources obtained by ICA allows for flexibility in linearly combining different sources.

Behaviour and design of the ‘lockbolt’ demountable shear connector for sustainable steel-concrete composite structures

In order to promote sustainable steel-concrete composite structures, special shear connectors that can facilitate deconstruction are needed. A lockbolt demountable shear connector (LB-DSC), including a grout-filled steel tube embedded in the concrete slab and fastened to a geometrically compatible partial-thread bolt, which is bolted on the steel section’s top flange of a composite beam, was proposed. The main drawback of previous similar demountable bolts is the sudden slip of the bolt inside its hole. This bolt has a locked conical seat lug that is secured inside a predrilled compatible counter-sunk hole in the steel section’s flange to provide a non-slip bolt-flange connection. Deconstruction is achieved by demounting the tube from the top of the slab by unfastening using a simple modified wrench. The mechanical behaviour of the proposed connector is assessed by four pushout tests that were conducted per Eurocode 4 recommendations. The tests showed high shear resistance, and high stiffness as compared to other DSCs, while the slip capacity results classified the LB-DSC as a ductile shear connector according to Eurocode 4. A refined nonlinear finite element model (FEM) was validated through the tests and reliably reproduced the experimental behaviour. Consequently, the calibrated FEM model was applied to carry out extensive parametric analyses to investigate the strength and geometry effects of concrete slab, infilled grout, tube, and bolt on the structural behaviour of the LB-DSC. On the basis of numerical and experimental results, a design equation is derived to predict the shear resistance of the LB-DSC.

Elastic and Viscoelastic Models of Crust Deformation in Strike-slip Fault

The crust, when viewed over a long period, moves towards one another. Crusts might experience sudden slip on a fault plane and caused fractures or cracks. There are three different types of faults, normal, reverse, and strike-slip faults. Induced stress due to sudden rupture on fault planes capable of creating stress and need to be measured quantitatively to comprehend the earthquake process. To understand the stress that occurs in strike-slip faults in the earth’s crust, the previous researchers study the use of elastic materials as the material of the earth’s crust, so that the earth crust’s deformation is elastic. However, elastic material has linear stress and strain relationship that results in reversible deformations or returns to their original shape. This material is not suitable for modeling the earth’s crust’s long-term deformation, where the deformation of the earth’s crust can be permanent, so a model is needed to solve this problem. In this study, we will compare the stress in the strike-slip fault in the upper crust with elastic materials, while the lower crust and upper mantle have viscoelastic materials compared to purely elastic materials through numerical simulations. This comparison is made to see the comparison between the two approaches with the earth’s layers’ actual state. The two models is chosen to represent the different failure processes of the earth crust, i.e. the elastic deformation part describes the response to stress in a short period, and the viscous deformation can explain the response over a more extended period. The study of both materials above is based on plate tectonic theory, in which the lithosphere plates will relatively move to each other because the layer material underneath is solid but can flow like a liquid for a long period.

Laboratory earthquake prediction of granite

Earthquake prediction refers to predicting the magnitude, location, and time of earthquakes and is challenging. Four attempts to predict the magnitude, location, and time of the laboratory earthquake of granite were made. First, the stick-slip failure process of granite samples was studied by a homemade test setup, and the whole process was monitored in real-time by strip strain gauges, rosette strain gauges, and acoustic emission (AE) transducers. Second, six parameters related to the stress drop were selected: dry density, Young's modulus, loading rate, static friction coefficient of the interface, normal stress, and shear stress. The prediction model of stress drop was established based on a backpropagation neural network (BPNN) considering the above six parameters. The stress drop in this paper is positively correlated with the released energy (magnitude) when the simulated fault slips suddenly. Third, the simulated fault interface was scanned by a high-precision 3D topography scanner before the stick-slip tests, and then the 3D topography scanning image was quantitatively measured based on digital image processing (DIP). According to the measurement results, the relationship between the nucleation position and the microstructure of the simulated fault interface was discussed. Fourth, the characteristics of AE parameters (absolute energy, ringing count rate, amplitude, b1 value) in the stick-slip process were studied. This paper aims to determine the precursory factors of sudden slip. This study helps explain the mechanism of shallow-focus earthquakes.

Fault reactivation induced by tunneling activity in clay material: Hints from numerical modeling

Seismic events with magnitude 3 and above have been associated with the removal of rock mass in mining environment since long-time. On the contrary, little is known about the possible seismic events induced by tunneling, although it presents similarities with mining. One great example is the case of the 57 km long Gotthard Base Tunnel excavation, which has been associated more than hundred seismic events, with the largest one having magnitude of ML 2.4, damaging the tunnel infrastructures (e.g. gallery floor or portal area).Different underground structures will be built probably up to 1000 m below ground for the construction of future deep geological for the storage of nuclear waste. While seismic risk will probably not constitute a liability for the storage site construction, it is important to understand the potential for reactivation of seismogenic features located nearby the future location of emplacement tunnels.Here we present numerical simulations aimed at understanding the potential for fault reactivation during tunnel construction in clay material, a potential host rock for nuclear waste repository. We evaluate the evolution of the stress changes during the simulation of the excavation with FLAC3D numerical solver. A strain-softening friction model is used to simulate the occurrence of a sudden slip on a fault zone when critical conditions for reactivation are satisfied. This constitutes a worst-case scenario, given the low seismogenic potential of clay rocks. We also present a sensitivity analysis on several critical parameters including fault frictional properties, stress conditions, as well as different tunnel sizes at varying distance from a nearby failure plane, with the final purpose of evaluating safety of a potential nuclear repository site on the short- and long-term.

On the Mechanism of Laboratory Earthquake Nucleation Highlighted by Acoustic Emission

Dynamics of granular media is the key to understanding behavior of many natural systems. In this work we concentrate on studying regularities of deformation of a gouge-filled fault. Confined granular layer – model fault – subjected to an external stress may display sudden slip owing to rearrangement of the granular layer. In nature fast slip along a fault results in an earthquake. To understand fault behavior better, we have conducted a comprehensive analysis of acoustic emission (AE) data that accompany stick-slip in granular media. Here we reveal and trace the emergence of two populations of AE. The first one is characterized by a waveform with a harsh onset, while the second one exhibits a gradual amplitude rise and a tremor-like waveform. During a regular stick-slip the statistical properties of the first population remains intact. The second one is very sensitive to alterations of stress conditions, and its scaling parameters correlate with the change of mechanical characteristics of the fault. Probably, AE populations were identified corresponding to two gouge-filled fault subsystems – a load-bearing granular network and an ensemble of relatively unloaded grains in the granular layer. The detected regularities point to a compound self-organization processes in fault zones and suggest that the final stage of earthquake preparation can be revealed in analyzing the scaling characteristics of seismic-acoustic data.

Plastic Deformation and Creep in Solid Helium

Helium crystals are quantum solids, with unusual mechanical properties. Quantum zero point motion prevents helium from freezing, unless pressure is applied, and helium crystals are extremely compressible, with elastic constants orders of magnitude smaller than those of conventional solids. In such quantum solids, tunneling allows atomic exchange and defects may move easily at low temperatures. The unusual mobility of dislocations and isotopic impurities in $$^4$$ He crystals can reduce their shear modulus at small strains by as much as 90%. For large strains, solid helium crystals are extraordinarily soft and ductile near their melting points, flowing under millibar stresses. At low strain rates, this high-temperature creep is thermally activated and involves diffusion of vacancies, which allow dislocations to move via climb. At low temperatures, these processes freeze out and helium crystals are much less ductile. Deformation proceeds via sudden slip events—dislocation avalanches—with a wide range of sizes and timescales. In this paper, we review experiments on plastic deformation and flow in solid $$^4$$ He and $$^3$$ He during the past 50 years, and discuss the plastic deformation mechanisms in solid helium that have been identified from these experiments.

Hypothetical Physics and Chemistry of Volcanic Eruptions: The Doorway to Their Prediction

This article presents a further development of the hypotheses concerning the possibility of predicting (“tectonic”) earthquakes [1]. Those hypotheses are based on the conversion of all types of released energy into heat and active chemical substances. One of the important sources of this phenomenon is the release of the latent energy trapped and stored during the Earth’s accretion. The latent energy of primordial hydrogen and helium escaping from the Earth’s core and lower mantle causes degassing processes [2] [3]. This latent energy converts into totally different types of chemical, electromagnetic and thermal energies of active compounds that are responsible for the major endogenic terrestrial processes. The dominating theories in seismology and volcanology are that an earthquake results from a sudden slip of a tectonic fault and that only magma and the gases contained in magma supply the volcanic energy resulting in the conclusions that earthquakes and eruptions are unpredictable. Volcanic eruption is considered herein to be a special case of the earthquake-process in which earthquake hypocenters rise to the Earth’s surface. A possible solution is proposed ([1] and herein) based on the analyses of the physicochemical processes as participants in earthquake and eruption preparations (foreshocks - major shock - aftershocks - volcanic eruptions) and on the characteristic rates of reflection of these processes on the Earth’s surface. Influences of Sun-Moon-tides and volcanic (“harmonic”) tremors are analyzed from physical-chemical point of view. The case of the 1980 eruption of Mount St. Helens and the proposed monitoring of the recommended additional data provides a way of selecting a complex of reliable earthquake and volcanic eruption precursors.

Rupture process of the April 24, 2017, Mw 6.9 Valparaíso earthquake from the joint inversion of teleseismic body waves and near-field data

The central Chilean margin (32°–33°S) is characterized by the subduction of the Juan Fernández Ridge (JFR) beneath the continental South American plate. The JFR corresponds to a hotspot track composed by seamounts typically 3–3.5 km high above the surrounding seafloor, with a ridge-trench collision zone underlying the prominent Valparaiso Forearc Basin (VFB). This region has been affected by several large and mega earthquakes, where the last event corresponds to a complex seismic sequence that took place at the southern edge of VFB in April 2017. The spatio/temporal distribution of the seismic events is characterized by a predominant southeast migration of the seismicity. An Mw 6.9 earthquake triggered two days after the sequence started and occurred at the northern end of the rupture area of the 1985 Mw 8.0 Valparaiso earthquake. We compute the kinematic rupture process of the 2017 Mw 6.9 Valparaiso earthquake from the joint inversion of teleseismic body waves and near-field data. The Akaike’s Bayesian Information Criterion was used to objectively estimate both, the relative weighting between datasets and the weighting of spatial and temporal constraints used as a priori information. The coseismic slip is distributed over an area of dimensions ∼35 × 10 km2, with a maximum slip of 1.5 m. The rupture propagated unilaterally downdip. The source duration from the moment-rate solution is ∼20 s, with a total seismic moment of 3.05 × 1019 Nm (Mw 6.9). The analysis of the seismicity shows that most of the events occurred along the plate interface, foreshock clustered northern from the mainshock epicenter and the aftershocks occurred to the southeast, at a deeper location. The inverted regional moment tensors show similar faulting mechanism than the mainshock. The seismic sequence started two days before the mainshock and lasted for about two weeks, and a migration pattern of the seismicity was observed. The rupture of the 2017 Mw 6.9 earthquake nucleated where the San Antonio seamount (belonging to the JFR) is subducting, and propagated downwards along a zone that presents high interseismic coupling. The complex seismic sequence might be explained by an aseismic slip transient in the zone and the influence of the downdip migration of fluids from the accretionary prism along the subduction channel. The erosive and tunneling effect left by the sudden slip of the subducting seamount might provide the cavity for downdip migration of fluids and subsequent swarm seismicity.

Removable shear connector for steel-concrete composite bridges

The conception and experimental assessment of a removable friction-based shear connector (FBSC) for precast steel-concrete composite bridges is presented. The FBSC uses pre-tensioned high-strength steel bolts that pass through countersunk holes drilled on the top flange of the steel beam. Pre-tensioning of the bolts provides the FBSC with significant frictional resistance that essentially prevents relative slip displacement of the concrete slab with respect to the steel beam under service loading. The countersunk holes are grouted to prevent sudden slip of the FBSC when friction resistance is exceeded. Moreover, the FBSC promotes accelerated bridge construction by fully exploiting prefabrication, does not raise issues relevant to precast construction tolerances, and allows rapid bridge disassembly to drastically reduce the time needed to replace any deteriorating structural component (e.g., the bridge deck). A series of 11 push-out tests highlight why the novel structural details of the FBSC result in superior shear load-slip displacement behavior compared to welded shear studs. The paper also quantifies the effects of bolt diameter and bolt preload and presents a design equation to predict the shear resistance of the FBSC.

In situ micro-tensile testing on proton beam-irradiated stainless steel

Small-scale mechanical testing techniques are currently being explored and developed for engineering applications. In particular, micro-tensile testing can add tremendous value, since the entire stress-strain curve, including the strain to failure, can be measured directly. In this work, 304 stainless steel specimens irradiated with 2 MeV protons to 10 dpa (full-cascade setting in the Stopping and Range of Ions in Matter, SRIM, software) at 360 °C was evaluated using micro-tensile testing. It was found that even on the micron scale, the measured strain corresponds well with macroscopic expectations. In addition, a new approach to analyzing sudden slip events is presented.

A Computational Method for the Inelastic Postbuckling of Steel Space Structures with Bolt Slip

The nonlinear behavior of space structures has been researched by various authors using the total and updated Lagrangian formulations. In this paper, a corotated-updated Lagrangian (CR-UL) formulation is used for studying the postbuckling behavior of steel reticulated systems. This formulation is used since space truss elements contain large components of rigid body displacements. The global tangent stiffness is derived from the corotation (CR) principle and the local (natural) tangent stiffness is derived using the updated Lagrangian (UL) finite element formulation. A state determination procedure is used for including the inelastic behavior with mixed hardening. Here members are assumed to reach the material strength limit state, which is reasonable in large span space structures based on serviceability governed design, with no consideration made for member buckling. The effect of bolt slip in the member joints is included by using a sudden slip model under the service loads. The global nodal displacements and coordinates are updated based on the analytical model of the bolt slip displacement using a simple affine transformation. The effect of bolt slip on the global displacements and member forces has been studied and compared with the results of previous authors.

On “whether earthquake precursors help for prediction do exist”

Whether earthquake precursors help for prediction do exist? This paper attempts to answer this question from the mechanism of tectonic deformation. Because an earthquake is sudden slip on a fault, a physical process from slow to fast should happen prior to its occurrence. Consequently, observable precursors should appear before earthquakes. Whereas, to detect such precursors remains a difficult task. In addition to some limitations of the effort, such as observational instruments, deployment of measurement sites, and complicated relations between the precursor and main shock, it is an important step whether the crucial temporal stage can be recognized. An earthquake is a mechanical process. From the differential stress-time process, the deformation of the seismogenic fault should have four states, i.e. stability, meta-stability, meta-instability, and instability. In the stability and meta-stability stages, when the external force is removed, the strain of the fault can be recovered to some extent. As the causative fault enters the meta-instability stage, it is just the deformation stage dominated by release behind the stress peak strength. After this moment, even if no external force is loaded, the fault has entered an evolutional stage of self-instability, i.e. an irreversible deformation stage, indicating the seismic event is bound to occur. Thus, this stage has a relation of uniqueness with the burst of the earthquake.

Influence of contact aging on nanoparticle friction kinetics.

One of the oldest concepts in tribology is stick-slip dynamics, where a disruptive sequence of stick and slip phases determine the overall resistance in sliding friction. While the mechanical energy dissipates in the sudden slip phase, the stick phase has been shown to be characterized by contact strengthening mechanisms, also termed contact aging. We present experiments of sliding nanoparticles, where friction is measured as a function of sliding velocity and interface temperature. The resulting complex interdependence is in good agreement with Monte Carlo simulations, in which the energy barrier for contact breaking increases logarithmically with time, at a rate governed by thermal activation.

Geophysical signatures resolving hydrogeological complexities over hard rock terrain—a study from Southern India

A series of geophysical parameters have been applied with geological perception to resolve the hydrogeological complexities over granitic terrain at Hyderabad, India. Frequent failure of borehole drillings and the thrust conditions of community have prompted a noninvasive suitable tool, applied at small scale for pinpointing potential well site. Geophysical scanning, viz. electrical resistivity tomography (ERT), spontaneous potential (SP), and electrical gradient profiling (GP) were employed within the restricted space of housing complex to obtain the true characteristics of the subsurface lithology, where anomalies by the underground utility structures have been nullified. Results showed, in ERT, the low order of resistivity range 123 to 200 Ωm showing a plume like weathered zone underlain by sudden slip of massive granite (>217 Ωm) was of great interest to proceed further in the process. Here, the switchover in SP value from +18 mV to −17 mV and GP from mean value 10 to 90 mV/m was recorded. The anomalies in SP and GP were precisely coincided with the ERT where upcoming of subsurface massive granite next to the inferred fracture was noted. Drilling core logs satisfies the geophysical signatures ensuring the inferred saturated fracture with the total yield 1,302 gal/h.

Generalization of treadmill-slip training to prevent a fall following a sudden (novel) slip in over-ground walking

The purposes of the study were to determine (1) whether treadmill-slip training could reduce the likelihood of falls during a novel slip in over-ground walking, and (2) to what extent such (indirect) training would be comparable to (direct) over-ground-slip training. A treadmill-slip training group (Group A, n=17) initially experienced repeated perturbations on treadmill intended to simulate forward-slip in over-ground walking. Perturbation continued and its intensity reduced when necessary to ensure subjects' successful adaptation (i.e., when they could land their trailing foot ahead of the slipping foot in at least 3 of 5 consecutive trials). They then experienced a novel slip during over-ground walking. Another 17 young adults in Group B experienced an identical novel slip that served as the controls. They then underwent more slip trials during over-ground walking. Their 16th slip trial was analyzed to represent the over-ground-slip training effect. Eight subjects (47%) in Group A fell upon their first treadmill slip, while all adapted successfully after a minimum of 15 slip trials. Upon the novel slip during over-ground walking, none of them fell in comparison to four subjects (23.5%) fell in Group B upon the same trial (p<0.05). Group A's control of stability, both proactive and reactive, was significantly better than that of Group B's on their first over-ground slip, while the level of improvement in the control of stability derived from indirect treadmill training was not as strong as that from direct over-ground-slip training, as demonstrated in Group B's 16th slip trial (p<0.001). These results clearly demonstrated the feasibility of fall reduction through treadmill-slip training.

Possible deep fault slip preceding the 2004 Parkfield earthquake, inferred from detailed observations of tectonic tremor

Earthquake predictability depends, in part, on the degree to which sudden slip is preceded by slow aseismic slip. Recently, observations of deep tremor have enabled inferences of deep slow slip even when detection by other means is not possible, but these data are limited to certain areas and mostly the last decade. The region near Parkfield, California, provides a unique convergence of several years of high‐quality tremor data bracketing a moderate earthquake, the 2004 magnitude 6.0 event. Here, I present detailed observations of tectonic tremor from mid‐2001 through 2008 that indicate deep fault slip both before and after the Parkfield earthquake that cannot be detected with surface geodetic instruments. While there is no obvious short‐term precursor, I find unidirectional tremor migration accompanied by elevated tremor rates in the 3 months prior to the earthquake, which suggests accelerated creep on the fault ∼16 km beneath the eventual earthquake hypocenter.

Insights on the kinematics of deep-seated gravitational slope deformations along the 1915 Avezzano earthquake fault (Central Italy), from time-series DInSAR

Among the causes of deep-seated gravitational slope deformations (DGSD), the most important is relief energy, which is closely related to the intensity of the active tectonic deformations, either at the regional scale or at the scale of a single active fault. We analyzed some examples of DGSD from the Eastern border of the Fucino basin, in the Central Apennines, where extensional tectonics has been active since the late Pliocene. Photogeological and field geomorphological analysis was performed to identify landforms typically associated with DGSD, such as counterslope scarps, double crests, trenches, and bulging slopes. These features are located on a mountain range at less than 1 km from the causative fault of the 1915 Avezzano earthquake. We used the SBAS Differential SAR Interferometry technique to measure the slow movements of the surface, and calculated differential vertical and horizontal ground velocities of 2–4 mm yr − 1 during the period spanning from 1992 to 2001. The quantitative information on the kinematics of the deformation provided some inferences on the different processes responsible for the evolution of the observed DGSD. The displacement time series shows non-linear deformation trends at some locations, possibly correlated with a strong meteorological event. We speculate that DGSD in this area are normally subject to slow deformation, and that sudden slip along sliding surfaces (observed in excavations) may sporadically be triggered off by extreme meteorological or seismic events. Evidence of catastrophic collapse of previous DGSD along the same mountain slope reinforce this hypothesis.

Ground support research at the WA School of Mines

Mining in Western Australia in the next two decades will be approaching depths and conditions in which the induced stress regimes will approach the strength of the rock masses surrounding the excavations. In such cases, failure may occur violently due to the energy stored within the rock masses. Furthermore, in those highly stressed regions of a rock mass, sudden slip on major structures in the vicinity of the excavations are more likely to occur with an associated release of energy in the form of compres sive and shear waves that excite the rock near the boundaries of excavations. In order to be prepared for such scenarios, and to ensure safe and economical excavations in the future, the WA School of Mines (WASM) and a number of sponsoring companies have conceptualized and undertaken a number of research projects in ground support technology. The projects range from static and dynamic laboratory testing of support and reinforcement elements to in-situ assessment of ground support corrosivity. The project background for each of the stabilization research projects at WASM has been summarized together with details of the methodology, current status, applications and future work.