Shear Displacement Rate Research Articles

Long-runout mechanism and landsliding behaviour of large catastrophic landslide triggered by heavy rainfall in Guanling, Guizhou, China

A large catastrophic landslide was triggered by a heavy rainfall on 28 June 2010 in Guanling, Guizhou, China. The landslide buried two villages and killed 99 people along the runout path. The landslide involved the failure of about 985 000 m3of sandstone from the source area, with a runout of about 1.4 km over a total vertical distance of about 420 m. To understand the possible long-runout mechanism and behaviour of the landslide, a detailed field survey of the landslide was conducted and samples were taken from the runout path. The shear behaviour of the sample based on a series of ring shear tests was examined, and numerical simulation of the landsliding behaviour by using a numerical runout model (DAN-W) was performed in which the shear strength obtained by ring shear tests was used. The experimental results reveal that the residual shear strength measured along the pre-existing shear surface is independent of the shear displacement rate under partially drained conditions, suggesting that the relationship between shear and normal stresses obeys the frictional model. A bulk basal friction angle of 14.4° at the base of the moving mass was then obtained from the test results. The simulated results show that the selected rheological model and parameters based on ring shear tests could provide the best performance in simulating the landslide. Therefore, it is expected that the model and parameters could improve the precision of hazard zonation for areas with geological, topographical, and climatic features similar to the Guanling landslide area.

Dynamic Shear Strength of a Needle-Punched GCL for Monotonic Loading

This paper presents an experimental investigation of the dynamic internal shear strength of a hydrated woven/nonwoven needle-punched geosynthetic clay liner (GCL) for monotonic (i.e., single direction) loading conditions. Displacement-controlled shear tests were conducted using a large direct shear machine for four normal stress levels ranging from 141 to 1,382 kPa and seven shear displacement rates R ranging from 0.1 to 30,000 mm/min. For each normal stress, peak shear strength first increased and then decreased with increasing displacement rate. Maximum values of peak strength occurred for R=100–10,000 mm/min and were 16–23% higher than corresponding static values measured at R=0.1 mm/min. For each normal stress, residual shear strength first decreased and then increased with increasing displacement rate, with minimum values occurring at R=1 mm/min. On a relative basis, residual strengths show greater dependence on displacement rate than peak strengths. The standard displacement rate for static shear tests of hydrated GCLs (0.1 mm/min) generally yielded conservative values of peak shear strength but unconservative values of residual shear strength, especially for higher normal stress levels. The GCL experienced large post-peak strength reduction for all test conditions.

Dynamic Shear Strength of GMX/GCL Composite Liner for Monotonic Loading

AbstractThis paper presents an experimental investigation of the dynamic shear strength of a composite liner consisting of a high-density polyethylene (HDPE) textured geomembrane (GMX) over a hydrated nonwoven/nonwoven needle-punched geosynthetic clay liner (GCL) for monotonic (i.e., single direction) loading conditions. Displacement-controlled shear tests were conducted using a large direct shear machine for five normal stress levels ranging from 13 to 2071 kPa and five shear displacement rates ranging from 0.1 to 30,000 mm/min. GCL internal failures occurred at high normal stress and low displacement rate. As normal stress decreased or displacement rate increased, failure mode transitioned to the GMX/GCL interface. Peak strength envelopes are slightly nonlinear (concave-down) and show dependence on displacement rate at higher normal stress. Large-displacement strength envelopes show greater dependence on displacement rate at higher normal stress due to the effect of changing failure mode. The standard ...

A displacement based model to determine the steady state creep strain rate of short fiber composites

Abstract A novel analytical method is developed for predicting steady state creep of short fiber composites using shear-lag theory, imaginary fiber technique and polynomial displacement functions. Also, this method employs equilibrium and constitutive equations. Polynomial displacement method (PDM) is a new insight for analysis of plasticity and elasticity problems which can be used as a simple, exact and general method. PDM is more accurate than the available methods. Important novelties of the PDM are determination of unknowns such as shear stresses and displacement rates on top of the fiber analytically. In this paper, all unknowns are obtained by well-behaved polynomial displacement functions. These functions satisfy incompressibility and boundary conditions. In spite of the previous researches, strain rates and stresses are analytically obtained by PDM without non-analytical assumptions. Also, suitable agreements are found among present analytical method, numerical (FEM) and available published results.

Residual strength and creep behaviour on the slip surface of specimens of a landslide in marine origin clay shales: influence of pore fluid composition

Active landslides in clay shales are widespread in Mediterranean countries. One of their characteristics is that the mobilized shear strength corresponds to the residual strength. The residual friction angle of clays depends on pore fluid composition which, in formations of marine origin, could have changed after emersion from the sea because of a number of processes, e.g., contact with rain or fresh water. This study aims at evaluating the influence of pore fluid composition and of its changes on the behaviour of Costa della Gaveta landslide, used as a case study. The natural pore fluid composition was analysed; then, the influence of such composition on the residual strength, and the effects of its variation on the shear creep behaviour were investigated. The paper shows that the natural pore fluid is a composite salt solution with variable concentration. It exhibits characteristics close to those of seawater at about 30 m depth, whereas it is very dilute close to the ground surface. Salt solutions at various concentrations and distilled water were thus used to simulate in the laboratory tests the effects of the different natural pore solutions. The results show that the residual friction angle varies significantly within the field concentration range. Moreover, exposure to distilled water causes a noticeable decrease in the residual strength during tests under constant shear displacement rate. Consistently, under constant driving shear stresses, time dependent displacements are observed, evolving with primary, secondary and tertiary creep phases, characterized, respectively, by decreasing, constant and increasing displacement rates.

EVALUATION OF SHEAR STRENGTH OF MODEL ROCK JOINTS BY EXPERIMENTAL STUDY

In this paper, variation of the shear strength of artificial rock joints under constant normal loading condition is studied. Idealised joint surfaces were prepared using a developed molding method with special mortar and shear tests were performed on these samples under CNL conditions. Different levels of normal load and shear displacement were applied on the samples to study joint behaviour before and during considerable relative shear displacement. Nine types of saw-tooth joints have been selected for simplicity of modelling to quantify the effect of CNL conditions on joint shear behaviour. It was found that the shear strength of joints is related to rate of shear displacement, joint roughness (varying joint asperity angles) and applied normal stress condition. Finally, based on the experimental results and observations made of sheared joint samples, a new peak shear strength envelope is proposed to model sawtooth type joints tested under CNL conditions.

LABORATORY MODELLING OF ROCK JOINTS UNDER SHEAR AND CONSTANT NORMAL LOADING

In this paper, the shear behaviour of artificial rock joints under constant normal loading conditions is studied. Idealised joint surfaces were prepared using a developed molding method with special mortar and shear tests were performed on these samples under CNL conditions. Different levels of normal load and shear displacement were applied on the samples to study the shear behaviour of sawtooth shaped joints before and during considerable relative shear displacement. Nine types of saw-tooth joints have been selected for simplicity of modelling to quantify the effect of CNL conditions on joint shear behaviour. It was found that the shear strength of joints is related to rate of shear displacement, joint roughness and applied normal stress condition. Finally, based on the experimental investigations and observations made of sheared joint samples, four conceptual models of shear stress-shear displacements have been developed. These four models summarize the entire experimental results based on elastic, dilation and residual zone defined along the shear displacement axis. The findings of this study expand current state of knowledge of joint shear strength which may be of significance for further research and for understanding the shear behaviour of rock joints for a stability analysis of the designed structures in surface and underground rock engineering.

Frictional behavior of simulated biotite fault gouge under hydrothermal conditions

Abstract We investigated frictional properties of biotite under hydrothermal conditions by shearing simulated biotite gouge sandwiched between saw-cut driving blocks, using a testing system with argon as confining medium. Experiments were conducted under an effective normal stress of 200 MPa, with pore pressure of 30 MPa. Temperatures were varied from room temperature to 600 °C, with shear displacement rate stepped at standard velocities (1.22–0.122 μm/s) and slow velocities (0.244–0.0488 μm/s) to acquire rate dependence of friction. Our results show that the friction coefficient of biotite ranges from 0.25 to 0.44, significantly lower than that of muscovite documented in previous studies. The steady-state rate dependence shows velocity strengthening at temperatures of 25 °C to 200 °C, and transitions to velocity weakening at temperatures above 300 °C. The velocity weakening is quite minor with (a − b) ranging from − 4 × 10− 4 to − 9 × 10− 4, and stick–slip motions at temperatures from 400 °C to 600 °C are found to be related to submicron dc values corresponding to critical stiffness higher than the actual stiffness surrounding the fault, thus leading to unstable slips. Microstructures of deformed samples show three types corresponding respectively to three different temperature ranges. While brittle structures are dominantly associated with deformation at 100 °C, significant plastic deformation occurred at higher temperatures. Deformation at temperatures of 200 °C to 400 °C are characterized with shear fracture zones accompanied with plastic deformation mostly associated with basal glide. Intensively deformed zones are the characteristic structures for samples deformed at 500 °C to 600 °C, accompanied with shear fracture zones and moderately deformed zones. It is evident that biotite alone is not weak enough to explain a weak fault like the San Andreas Fault, thus overpressured pore fluid or another weaker mineral is needed to produce a weak fault with apparent friction coefficient of 0.1–0.2. The around-neutral velocity weakening found for biotite may be appropriate in modeling fault creep transients in the mid crust.

Non-linear creep modeling of short-fiber composites using Hermite polynomials, hyperbolic trigonometric functions and power series

A novel analytical model is presented for analyzing the steady-state creep in short-fiber composites under axial load utilizing the previous shear-lag theory, the imaginary fiber technique and also new approaches of Hermite polynomials, hyperbolic trigonometric functions and power series. The steady-state creep behavior of the matrix is described by an exponential law, while the fibers behave elastically. In this model, in spite of the previous researches, some unknowns such as shear stress, displacement rates, and creep strain rates are correctly determined in all regions of the unit cell without using any further assumptions. In comparison with previous analytical approaches, the results of the present work are closer to the FEM simulations. This strong method can be used in various problems in applied physics and mechanics such as elastic and plastic analysis of nano-composites.

Methodology for seismic and post-seismic stability assessment of natural clay slopes based on a viscoplastic behaviour model in simplified dynamic analysis

A co-seismic viscoplastic sliding model, composed of two consequential behaviour phases, was realised in order to assess the co-seismic and post-seismic stability of natural slopes. The model takes into consideration the development and distribution of available strengths in pre-seismic conditions, as well as the viscoplastic behaviours manifested during monotonic and impulsive fast shearing tests on different clayey soils. In relation to the strength increase produced by the shear displacement rate, phase I is present during sliding on pre-existing failure surfaces at the residual state and/or in weak bands at the fully softened state. In this latter case, this is limited to small displacements. Conversely, phase II is characterised by strength decrease and occurs if and when the inertial dynamic load mobilises the “impulsive critical shear strength”, which is greater than the shear strength available in the pre-seismic static field. This implies the development of a first failure or a new failure surface with high shear displacements along these surfaces. The simplified dynamic analysis for infinite slopes, integrated by the behaviour model introduced in this paper, highlights a less conservative nature in comparison to that of the classic Newmark approach with one single exception. This occurs on attainment of the “static break point” where the co-seismic displacements obtained are comparable or even greater than those attainable from the classic Newmark approach. Furthermore, in relation to the co-seismic development of shear strength, it is possible to estimate in the short term as well as in the long term the post-seismic instability after the main shock.

Frictional Properties of Sedimentary Rocks and Natural Fault Gouge from the Longmen Shan Fault Zone, Sichuan, China

In this paper, we report friction experiments performed on samples collected from the region hit by the 2008 Wenchuan earthquake in the Longmen Shan fault zone (LFZ) of Sichuan, southwestern China. The materials tested consisted of simulated gouges prepared from intact clay-rich mudstone and sandstone, a calcite limestone, plus a natural fault gouge from a trenched, surface rupture cutting the mudstone and sandstone. The clay-rich samples, including the natural gouge, were dominated by illite and quartz. In our experiments, we sheared 1-mm-thick gouge layers between saw-cut driver blocks, using a triaxial testing machine at conditions corresponding to ∼2 km depth in the LFZ. Temperature was varied from 25°C to 150°C, and to investigate the velocity dependence of friction, we stepped the shear displacement rate between 1.22 and 0.122 μ m/s. Our results show that the natural gouge was more illite-rich and much weaker than the protolith mudstone and sandstone and showed a steady-state friction coefficient of ∼0.4 compared with ∼0.6 for the latter. The limestone gouge displayed values of 0.6–0.7. All samples, except the limestone, showed stable, velocity-strengthening slip. The limestone showed velocity-strengthening at 25°C–50°C, but quasi-static oscillations at 100°C–150°C along with velocity-weakening behavior at 150°C. We apply our results to discuss the role of the sedimentary rocks studied during events such as the Wenchuan earthquake and argue that the clay-rich sediments of the region may have a damping effect upon ruptures propagating from depth, whereas the limestone may accelerate propagation, producing significant stress drops.

Effects of Anterior Shear Displacement Rate on the Structural Properties of the Porcine Cervical Spine

While the individual tissues of the vertebral joint demonstrate viscoelastic properties, the global viscoelastic properties of the lumbar vertebral joint are not well established. This study investigated how changes in displacement rate influenced the mechanical response of the porcine cervical spine (a surrogate or model for the human lumbar spine) exposed to acute anterior shear failure loading. Thirty porcine cervical spine specimens (15 C3-C4 and 15 C5-C6) were placed under a 1600 N compressive load and subsequently loaded in anterior shear to failure at one of three randomly assigned displacement rates (1 mm/s, 4 mm/s, or 16 mm/s). Ultimate anterior shear force, ultimate displacement, average stiffness, and energy stored until failure were calculated. Load rate in the elastic region was also calculated to compare the load rates used in this study to those used in previous studies. Changes in displacement rate affected the C3-C4 and C5-C6 specimens differently. C5-C6 specimens tested at 16 mm/s had an ultimate force that was 28% and 23% higher than at 1 (p=0.0215) and 4 mm/s (p=0.0461), respectively. The average stiffness to failure of the C5-C6 specimens tested at 16 mm/s was 52% higher than at 4 mm/s (p=0.0289). No such differences were found for the C3-C4 specimens. An increase in the anterior shear displacement rate did not necessarily demonstrate viscoelasticity of the vertebral joint. Specimen intervertebral levels were affected differently by changes in anterior shear displacement rate, which may have been a result of anatomical and postural differences between the two levels. Future studies should further investigate the effect of displacement rate on the spine and the inconsistencies between different specimen levels.

Viscous Properties of Granular Materials Having Different Particle Shapes in Direct Shear

The viscous properties of air-dried relatively poorly-graded granular materials having different particle shapes were evaluated by performing a series of direct shear (DS) tests. The applied loading histories include repeated step changes in the shear displacement rate (s) or repeated sustained loading stages during otherwise monotonic loading (ML) at a constant s under constant vertical stress. Test results of an angular gravelly soil (i.e., Chiba gravel-a) obtained from the present study and those of a wide variety of poorly-graded granular materials (i.e., glass beads and natural sands including Toyoura, Hostun, Silica No. 6a, Ticino, Silver Leighton Buzzard, Ottawa, Albany and Monterey sands) previously obtained by the authors are analysed. The viscous properties of granular materials can be adequately described by three basic parameters: i.e., the rate-sensitivity coefficient, the residual rate-sensitivity coefficient (or their ratio, i.e., the viscosity-type parameter) and the decay parameter. These parameters, as well as the viscosity type (i.e., Isotach, Combined, TESRA and P&N), are strongly affected by particle shape as quantified in terms of the degree of particle angularity while being rather independent of particle size. The creep deformation that takes place by sustained loading increases with an increase in the shear stress level, and it also increases with changes in the viscosity type associated with an increase in mainly the particle angularity and partly the coefficient of uniformity. The various viscous property types and transitions among them can be described by a single general equation incorporating these parameters. A non-linear three component model incorporating this general equation can simulate very well all of the various viscous responses observed in the DS tests referred to in the paper.

Viscous Property of Toyoura Sand Over a Wide Range of Shear Deformation Rate and its Model Simulation

ABSTRACT As part of a long-term research program to evaluate the rate effects on the stress-strain behaviour of geomaterials, the viscous properties of a poorly-graded relatively angular quartz-rich sand, Toyoura sand, under air-dried conditions, were investigated by performing a comprehensive series of direct shear (DS) tests at a fixed normal stress equal to 50 kPa. The tests were performed on loose and dense specimens subjected to the following different loading histories: a) monotonic loading (ML) at constant shear displacement rate (s) differing by a factor up to 100,000; b) ML at constant s including otherwise a number of step changes in s by a factor of 100; and c) a number of sustained loading (SL) stages during otherwise ML at constant values of s differing by a factor up to 1,000. Tests a) revealed that, with dense specimens, the peak shear strength is remarkably independent of s while the residual shear strength noticeably decreases with an increase in s. That is, the viscous property is the so-called TESRA type at the peak stress state, while it is the so-called Positive & Negative (P&N) type at the residual state. With loose specimens, both peak and residual shear strengths decrease with an increase in s, indicating that the viscous property is already the P&N type at the peak stress state and definitely so at the residual state. These results are qualitatively and quantitatively consistent with those from tests b), by which the viscosity properties were quantified in terms of the rate-sensitivity coefficient. The results from tests c) showed that creep shear displacement, Δs, increases with a decrease in the tangent stiffness at the immediately preceding ML phase or with an increase in the shear stress level during the SL stage. The value of Δs for a given period steadily increases with an increase in s during the immediately preceding ML phase. These trends of viscous behaviour are simulated all very well by a non-linear three-component model incorporating a general expression of viscous stress.

Viscous Behaviour of Unbound Granular Materials in Direct Shear

ABSTRACT The viscous properties of a variety of poorly graded unbound granular materials were investigated by direct shear tests on 12 cm-cubic specimens. A number of natural sands having different particle shapes and sizes as well as uniform glass beads having different particle sizes were used. The viscous properties were evaluated by changing the shear displacement rate many times during otherwise monotonic loading (ML) at constant shear displacement rate and normal pressure. Creep loadings were performed in two tests. Different types of viscous properties, which are affected by the particle shape but essentially independent of the particle size, are reported. The viscosity type varies as the shear displacement increases from the pre-peak regime towards the residual state. A new viscosity type, called “Positive & Negative”, was found with relatively round granular materials in the pre-peak regime and with relatively angular granular materials in the post-peak softening regime and at the residual state. Peculiar “rate-independent unstable behaviour” is observed with round natural sands and glass beads in the post-peak regime, which is more significant and frequent with glass beads. Controlled by the particle size, this behaviour is caused by the so-called stick/slip phenomenon. The viscous properties observed in the DS tests are quantified by the rate-sensitivity coefficient defined in terms of the shear and normal stresses, which are then converted to those defined in terms of the major and minor principal stresses, β13. These β13 values are consistent with those directly obtained by the triaxial and plane strain compression tests. The effects of particle size on the β13 value are negligible and the β13 value tends to decrease as the particle shape becomes more round.

Residual Strength Characteristics of Naturally and Artificially Cemented Clays in Reversal Direct Box Shear Test

The naturally cemented clay preserving chemical bonds that was gradually disintegrated by weathering is a soil exhibiting a progressive failure such as a landslide. The residual strength of soil possessing cementation properties given by diagenesis has not yet been investigated. The objective of this study is to clarify the residual strength characteristics of naturally and artificially cemented clays using an improved reversal direct box shear test apparatus. Based on the test results of reconstituted Kaolin clay, undisturbed, remolded and reconstituted samples of three natural clays, this paper describes the influence of normal stress, shear displacement rate, consolidation and shear histories on the residual strength of cemented clay. Especially, to simulate the same mechanical behavior as the naturally cemented clays, the cementation was artificially reproduced by adding cementing agents to slurry clay. Consequently, 1) the residual strength of cemented clay is independent of consolidation yield stress and initial void ratio. 2) The residual strength of cemented clay as well as non-cemented clay increases with increasing the shear displacement rate. 3) The residual strength of cemented clay as well as non-cemented clay is not affected by any stress history.

A Large Diameter Triaxial Apparatus to Measure Pore Pressure and Displacements on a Pre-existing Shear Zone/Plane

Abstract The development of an apparatus to measure pore pressure and displacements on a pre-existing shear zone/plane during triaxial testing is presented. The apparatus includes a newly developed 405-mm diameter triaxial cell, a miniature pore pressure transducer for monitoring shear-induced pore pressures, and a displacement transducer for measuring shear displacements. Tests were performed by mounting the pore pressure transducer onto the face of a pre-existing shear plane in the specimen and installing the displacement transducer inside the triaxial cell to monitor local deformations. The results reveal that pore pressures measured on the shear plane and the base of specimens of Athabasca clay, Highvale mudstone, and Fort McMurray highly weathered limestone are identical at a shear displacement rate equal or less than approximately 18 mm/day. This implies that when the shear displacement rate is less than about 18 mm/day for rocks/soils that have a permeability greater than 10−8∼10−9cm/s, the pore pressure obtained from in situinstrumentation, which may not be set exactly on the shear plane, can be used as the shear zone pore pressure.

Discussion of “Analysis of a Large Database of GCL Internal Shear Strength Results” by Jorge G. Zornberg, John S. McCartney, and Robert H. Swan, Jr.

The discusser cites Chiu and Fox (2004) regarding a large published database containing analysis of internal and interface geosynthetic clay liners (GCL) shear strengths, including those of the discusser. One item found in this database conflicts with the authors' results ? the failure envelope. For hydrated needle-punched GCLs, the non-linear regression analysis produced a zero intercept instead of the permitted non-zero intercept. This contradicts the authors' test results. In shear-induced excess pore pressures, the discusser states that the hypothesis of the authors -- that pore water suction causes progressively larger shear strengths with increasing shear displacement rate (SDR) at low normal stresses -- is not borne out in the data from Fox et al. (1998). As for SDR effects at high normal stress conditions, the discusser notes that more research is needed.

Experimental characterization and mechanical behavior analysis of intermetallic compounds of Sn–3.5Ag lead-free solder bump with Ti/Cu/Ni UBM on copper chip

Due to today’s trend towards ‘green’ products, the environmentally conscious manufacturers are moving toward lead-free schemes for electronic devices and components. Nowadays the bumping process has become a branch of the infrastructure of flip chip bonding technology. However, the formation of excessively brittle intermetallic compound (IMC) between under bump metallurgy (UBM)/solder bump interface influences the strength of solder bumps within flip chips, and may create a package reliability issue. Based on the above reason, this study investigated the mechanical behavior of lead-free solder bumps affected by the solder/UBM IMC formation in the duration of isothermal aging. To attain the objective, the test vehicles of Sn–Ag (lead-free) and Sn–Pb solder bump systems designed in different solder volumes as well as UBM diameters were used to experimentally characterize their mechanical behavior. It is worth to mention that, to study the IMC growth mechanism and the mechanical behavior of a electroplated solder bump on a Ti/Cu/Ni UBM layer fabricated on a copper chip, the test vehicles are composed of, from bottom to top, a copper metal pad on silicon substrate, a Ti/Cu/Ni UBM layer and electroplated solder bumps. By way of metallurgical microscope and scanning-electron-microscope (SEM) observation, the interfacial microstructure of test vehicles was measured and analyzed. In addition, a bump shear test was utilized to determine the strength of solder bumps. Different shear displacement rates were selected to study the time-dependent failure mechanism of the solder bumps. The results indicated that after isothermal aging treatment at 150 °C for over 1000 h, the Sn–Ag solder revealed a better maintenance of bump strength than that of the Sn–Pb solder, and the Sn–Pb solder showed a higher IMC growth rate than that of Sn–Ag solder. In addition, it was concluded that the test vehicles of copper chip with the selected Ti/Cu/Ni UBMs showed good bump strength in both the Sn–Ag and Sn–Pb systems as the IMC grows. Furthermore, the study of shear displacement rate effect on the solder bump strength indicates that the analysis of bump strength versus thermal aging time should be identified as a qualitative analysis for solder bump strength determination rather than a quantitative one. In terms of the solder bump volume and the UBM size effects, neither the Sn–Ag nor the Sn–Pb solders showed any significant effect on the IMC growth rate.

Shear-Displacement-Amplitude Dependent Pore-Pressure Generation in Undrained Cyclic Loading Ring Shear Tests: An Energy Approach

By conducting a series of shear-torque-controlled (STC) and shear-displacement-controlled (SDC) ring shear tests under undrained conditions, the effects of cyclic loading frequency, shear displacement rate, and overconsolidation ratio (OCR) on the pore-pressure generation were examined and analyzed by means of an energy approach. Cyclic STC tests demonstrated that as the frequency of loading increased, the shear energy ( Wtotal ) as well as the total shear displacement ( ltotal ) until liquefaction substantially decreased, while the number of cycles to liquefaction (N) increased with frequency. Nevertheless, SDC tests showed that Wtotal , ltotal , N did not vary with frequency. This dependency of Wtotal on the loading frequency in STC tests was inferred to be due to the different resultant shear displacement amplitude after shear failure but before liquefaction during cyclic shearing. The results of STC tests on samples with different OCRs showed that all these three parameters of Wtotal , ltotal , N incr...