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Yajing Liu - One of the best experts on this subject based on the ideXlab platform.
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numerical simulations on megathrust rupture stabilized under strong Dilatancy strengthening in slow slip region
Geophysical Research Letters, 2013Co-Authors: Yajing LiuAbstract:[1] Episodic slow slip events (SSEs) typically involve a few millimeters to centimeters of slip over several days to months at depths near or further downdip of megathrust seismogenic zones. Despite its widespread presence in subduction margins, it remains unknown how SSEs interact with the seismogenic zone and affect megathrust ruptures. Here, I construct a 2-D thrust fault model governed by rate-state friction to investigate how fault Dilatancy influences the amplitude and spatial distribution of‘ coseismic slip, afterslip, and SSEs. Model results illustrate that, under strong Dilatancy and high pore pressure around the friction stability transition, coseismic rupture stops at the onset of SSEs. Modeled SSEs have lower velocities, longer recurrence intervals and durations, and larger slip amounts as Dilatancy becomes stronger, demonstrating a transition from short-term to long-term type of SSE behavior. These results qualitatively explain the range of spatial distributions of SSEs and megathrust ruptures observed or inferred in natural subduction zones. Furthermore, the relative depths of SSEs and megathrust afterslip may serve as an indicator of Dilatancy effectiveness.
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role of fault gouge Dilatancy on aseismic deformation transients
Journal of Geophysical Research, 2010Co-Authors: Yajing Liu, Allan M RubinAbstract:[1] In the vicinity of episodic aseismic transients in several subduction zones, the presence of interstitial fluids and near-lithostatic pore pressure has been proposed to interpret seismic observations of high P to S wave speed ratio and high Poisson's ratio. Under such conditions, fault stabilization by Dilatancy-induced suction during increased shear strain rates becomes very efficient. We analyze the frictional and hydraulic conditions for spontaneous transients on a fluid-infiltrated fault including Dilatancy and pore compaction in the framework of rate and state friction with a “membrane diffusion” approximation. In both a simplified spectral model and a 2-D Cascadia-like subduction fault model, the fault response is mainly controlled by three nondimensional parameters: (1) W/h*, the along-dip width of the high pore pressure, velocity-weakening fault relative to a characteristic nucleation size, (2) a drainage parameter U, the relative time scales for fluid diffusion and friction evolution, and (3) a Dilatancy parameter E, the relative contributions to stress drop from Dilatancy and friction evolution. The incorporation of Dilatancy enables aseismic transients at much larger values of W/h* than is possible under conditions of constant pore pressure. An analytic estimate of the maximum slip velocity as a function of W/h*, E, and U is derived and agrees reasonably well with the simulation results. The dependence of the properties of modeled transients on the drainage parameter U is similar to that on the Dilatancy parameter E. For U (E) less than 1, maximum velocity decreases, while recurrence period remains relatively constant. For U (E) greater than 1, maximum velocity approaches the steady state velocity, and recurrence period approaches the period at neutral stability. In the subduction fault model using gabbro gouge friction properties, the slip per episode and the recurrence period increase with W/h*, generally following the trend defined without Dilatancy. The maximum velocity with Dilatancy can be several orders of magnitude smaller than that without, in particular for larger values of E and values of W/h* near the no-Dilatancy stability limit.
Laddu Indika Nalin De Silva - One of the best experts on this subject based on the ideXlab platform.
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stress Dilatancy relationships of sand in the simulation of volumetric behavior during cyclic torsional shear loadings
Soils and Foundations, 2014Co-Authors: Laddu Indika Nalin De Silva, Junichi Koseki, Seto Wahyudi, Takeshi SatoAbstract:Abstract In order to describe the volumetric behavior of soil subjected to shearing, a relationship that deals with the ratio of plastic strain increments to stress ratio (i.e. a stress–Dilatancy relationship) is required in addition to the stress–shear strain relationship. In view of the above, stress–Dilatancy relationships during cyclic torsional shear loadings were experimentally investigated in the current study. Based on the experimental results, a bilinear non-unique stress–Dilatancy model was proposed for stress controlled drained cyclic torsional shear loading. The stress–Dilatancy relationships during virgin loading and subsequent cyclic loading were modeled separately by considering the effects of stress history (over-consolidation or normal consolidation). Then the volume change of Toyoura sand specimens subjected to cyclic torsional shear loading was simulated by combining the simulation of stress–shear strain relationship with the proposed stress–Dilatancy relationships. It was observed from the comparison of the experiment results with the simulation of volumetric strain that, after combining with accurate modeling of stress–shear strain relationship, the proposed stress–Dilatancy relationship can reasonably simulate the volumetric behavior of sand subjected to various drained cyclic torsional shear loadings.
D. Labrie - One of the best experts on this subject based on the ideXlab platform.
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Post-yield Strength and Dilatancy Evolution Across the Brittle–Ductile Transition in Indiana Limestone
Rock Mechanics and Rock Engineering, 2017Co-Authors: G. Walton, A. Hedayat, E. Kim, D. LabrieAbstract:An extensive uniaxial and triaxial compression testing programme was performed on Indiana Limestone to assess its behaviour across the brittle–ductile transition. Particular attention has been paid to the post-yield evolution of strength and Dilatancy. Specimens tested at σ _3 = 30 MPa displayed a fully ductile failure mechanism, whereas specimens tested at σ _3 = 15 MPa and σ _3 = 20 MPa displayed transitional mechanisms, which were neither fully brittle nor fully ductile. Based on an examination of failure localization and Dilatancy characteristics, the stress at which crack volumetric strain begins to increase was found to be an indicator of individual specimen ductility. In contrast to less porous rocks, the reversal of total volumetric strain did not coincide with the onset of axial strain nonlinearity under unconfined conditions. With respect to post-yield strength, a major change in the rate of friction mobilization relative to plastic shear strain was observed across the brittle–ductile transition. The Dilatancy of the specimens was also found to undergo a major change, with the plastic shear strains to mobilization of peak Dilatancy in the ductile regime being approximately one order of magnitude higher than in the brittle regime.
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post yield strength and Dilatancy evolution across the brittle ductile transition in indiana limestone
Rock Mechanics and Rock Engineering, 2017Co-Authors: G. Walton, A. Hedayat, E. Kim, D. LabrieAbstract:An extensive uniaxial and triaxial compression testing programme was performed on Indiana Limestone to assess its behaviour across the brittle–ductile transition. Particular attention has been paid to the post-yield evolution of strength and Dilatancy. Specimens tested at σ 3 = 30 MPa displayed a fully ductile failure mechanism, whereas specimens tested at σ 3 = 15 MPa and σ 3 = 20 MPa displayed transitional mechanisms, which were neither fully brittle nor fully ductile. Based on an examination of failure localization and Dilatancy characteristics, the stress at which crack volumetric strain begins to increase was found to be an indicator of individual specimen ductility. In contrast to less porous rocks, the reversal of total volumetric strain did not coincide with the onset of axial strain nonlinearity under unconfined conditions. With respect to post-yield strength, a major change in the rate of friction mobilization relative to plastic shear strain was observed across the brittle–ductile transition. The Dilatancy of the specimens was also found to undergo a major change, with the plastic shear strains to mobilization of peak Dilatancy in the ductile regime being approximately one order of magnitude higher than in the brittle regime.
Guansheng Han - One of the best experts on this subject based on the ideXlab platform.
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aggregate gradation effects on Dilatancy behavior and acoustic characteristic of cemented rockfill
Ultrasonics, 2019Co-Authors: Meimei Feng, Xianbiao Mao, Zhanqing Chen, Guansheng HanAbstract:Investigating the effect of the aggregate gradation on the material properties of cemented rockfill is significant for the green mining, economic benefit and engineering safety. Consequently, the ultrasonic test, uniaxial compression experiment and acoustic emission (AE) monitor on cemented rockfill were carried out, for which the aggregate satisfied Talbot gradation. The Dilatancy behavior and AE characteristic of cemented rockfill under load were investigated. The damage in the internal structure under compression was revealed by the deformation and AE signals of cemented rockfill. The effect of the Talbot index on the ultrasonic pulse velocity (UPV) and the strength parameters such as stress of Dilatancy onset and uniaxial compressive strength (UCS) of cemented rockfill was analyzed. The mechanical properties of cemented rockfill materials were evaluated by the establishment of the relation between the UPV and the strength parameter. The results show that The difference between the stress of Dilatancy onset and the UCS, the deformation performance and the activity of AE signals during Dilatancy are positive correlated with the Talbot index of aggregate in cemented rockfill. The relation between the UPV and the strength parameters (stress of Dilatancy onset and UCS) of cemented rockfill can be characterized by the positive linearity, and the UPV is also suitable for characterizing the stress of Dilatancy onset of cemented rockfill material. The cubic polynomial is more suitable for describing the relations between the parameters of strength and UPV and the Talbot index of aggregate than the quadratic polynomial, and the Talbot index with optimal aggregate gradation reflected the maximum strength of cemented rockfill material should be around 0.45-0.47.
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experimental investigation on Dilatancy behavior of water saturated sandstone
International journal of mining science and technology, 2017Co-Authors: Meimei Feng, Wenli Zhang, Guansheng HanAbstract:Abstract It is important to study the Dilatancy property of water-saturated rock for understanding the engineering behavior of loaded rock mass. This study carried out the uniaxial and triaxial compressive experiments on the water-saturated red sandstone, analyzed the influences of confining pressure and pore pressure on Dilatancy property of water-saturated rock, and discussed the reasonable basis of the stress of Dilatancy onset as a strength design parameter of rock engineering, finally established the prediction model of the stress of Dilatancy onset under the impacts of confining pressure and pore pressure. The results show that the strength parameters (the stress of Dilatancy onset and peak strength) and deformation parameters (axial strain and circumferential strain) of water-saturated sandstone increase with the confining pressure, and the relations can be fitted with a positive linear function. The cohesion and internal friction angle obtained from the stress of Dilatancy onset decrease by 11.57% and 7.33%, respectively, when compared with those obtained from the peak strength. The strength parameters and deformation parameters of water-saturated sandstone decrease basically with the increase of pore pressure, in which the relations between strength parameters or axial strain and pore pressure can be fitted with a negative linear function. However, the relation between the peak circumferential strain and the pore pressure should be characterized by a negative exponential function, and the circumferential strain at Dilatancy onset isn’t affected by the pore pressure.
Takeshi Sato - One of the best experts on this subject based on the ideXlab platform.
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stress Dilatancy relationships of sand in the simulation of volumetric behavior during cyclic torsional shear loadings
Soils and Foundations, 2014Co-Authors: Laddu Indika Nalin De Silva, Junichi Koseki, Seto Wahyudi, Takeshi SatoAbstract:Abstract In order to describe the volumetric behavior of soil subjected to shearing, a relationship that deals with the ratio of plastic strain increments to stress ratio (i.e. a stress–Dilatancy relationship) is required in addition to the stress–shear strain relationship. In view of the above, stress–Dilatancy relationships during cyclic torsional shear loadings were experimentally investigated in the current study. Based on the experimental results, a bilinear non-unique stress–Dilatancy model was proposed for stress controlled drained cyclic torsional shear loading. The stress–Dilatancy relationships during virgin loading and subsequent cyclic loading were modeled separately by considering the effects of stress history (over-consolidation or normal consolidation). Then the volume change of Toyoura sand specimens subjected to cyclic torsional shear loading was simulated by combining the simulation of stress–shear strain relationship with the proposed stress–Dilatancy relationships. It was observed from the comparison of the experiment results with the simulation of volumetric strain that, after combining with accurate modeling of stress–shear strain relationship, the proposed stress–Dilatancy relationship can reasonably simulate the volumetric behavior of sand subjected to various drained cyclic torsional shear loadings.