Initial Shear Stress Research Articles

Experimental Investigation on Shear Mechanical Behavior of Sandstone Containing a Pre-existing Flaw Under Unloading Normal Stress with Constant Shear Stress

Excavation, river incision and anchor cable relaxation would result in unloading of stress in at least one direction of rock masses in caverns or slopes, and the unloading failure is prominent and it even shows remarkable tensile failure. The previous direct shear tests with constant normal stress can no longer meet these circumstances. However, the experimental study of rock shear behavior under unloading normal stress condition is rare. This paper presents an innovative experimental method to study the mechanical behaviors of sandstone containing a pre-existing flaw under unloading normal stress with constant shear stress. Five failure patterns were identified based on the analysis of crack propagation and their mechanical properties. The failure pattern transforms from mixed tensile–shear failure to tensile failure then to shear failure with the increase of flaw angle. Initial normal stress is greater, the propagating cracks behave as stronger tensile fractures. The peak dilatancy angle increases and decreases with the increase of the initial normal and shear stresses, respectively. Internal friction angle and cohesion both decrease first and then increase with the increase of flaw angle. The branch crack, extent of exfoliation, shear scratch and failure pattern are different from that in the traditional direct shear tests. Unloading normal stress significantly weakens the shear strength compared to traditional direct shear tests, suggesting that the shear strength parameters used in stability evaluation of rock excavation engineering should be determined by unloading tests. The results enrich the basic theory of rock mechanics.

The Near‐Fault Ground Motion Characteristics of Sustained and Unsustained Free Surface‐Induced Supershear Rupture on Strike‐Slip Faults

AbstractThe free surface is shown to be one of the key factors that may promote supershear rupture propagation on strike‐slip faults even if its initial shear stress is not larger enough as predicted by the Burridge‐Andrews mechanism. However, previous study has shown the free surface‐induced supershear rupture may be unsustained, which turns to sub‐Rayleigh rupture itself as the rupture propagates. We study the near‐field ground motion of sustained and unsustained supershear ruptures using the finite difference method based on the dynamic rupture processes of three vertical strike‐slip faults with the same initial stresses and different hypocenter depths. Both the unsustained supershear ruptures with shallower hypocenter depths show the sub‐Rayleigh characteristics in the peak ground velocity distribution, that is, strong amplitude is noticed beyond the end of the fault without any observed Mach cone. We observe that the arrival time differences between the maximum fault‐perpendicular and fault‐parallel velocity reveal the Mach cone clearly for the sustained supershear rupture. A distinct supershear phase in the high‐frequency seismograms is observed. We also compare the 70° dip strike‐slip case in which unsustained supershear rupture may still present sub‐Rayleigh characteristics in the near‐field ground motion, and the break of symmetry perturbs the normal stress as rupture propagates, which has a key influence in the rupture propagation and ground motion. Our work provides a new insight to understand the supershear rupture in nature earthquakes and the relationship between the ground motion and the rupture process on the fault.

Investigation of Initial Static Shear Stress Effects on Liquefaction Resistance Using Discrete Element Method Simulations

Prior laboratory and in situ investigations show that monotonic preshearing can have a significant effect on the cyclic response of granular materials. The underlying mechanics that are responsible for these changes in behavior in response to preshearing are not well characterized, however. Herein, we use the discrete-element method (DEM) to simulate undrained monotonic and cyclic simple shear tests with the constant volume method. Through published comparisons to laboratory data, DEM simulations have been shown to reasonably predict the cyclic response of granular materials, making them an appropriate tool for studying the effects of initial static shear stress on liquefaction initiation. Mechanical coordination number and the normal force-weighted fabric tensor are used to describe the evolution of fabric after monotonic preshearing and during cyclic loading. We find that higher initial static shear stress induces smaller cyclic strength in stress-controlled cyclic simple shear tests, but that there is no such effect in strain-controlled cyclic simple shear tests in which the normal force-weighted anisotropy is removed in the first three loading cycles. In addition, the stability of specimens is found to be closely related to pore-pressure increases. Finally, we show that the effect of initial static shear stress on liquefaction resistance is a combination of reduced stability before cyclic loading and accumulated shear strain during cyclic loading.

Dynamic rupture simulations with heterogeneous initial stresses inversed from a given slip distribution: A case study of the 2017 Mw 6.5 Jiuzhaigou earthquake

Heterogeneous initial stresses are extremely important in understanding the physics of earthquake rupture processes. We propose a method to estimate heterogeneous initial stresses by comparing the slip from dynamic rupture simulations and the input joint inversion result and apply it to the 2017 Mw 6.5 Jiuzhaigou earthquake, which occurred in the intersection area of the Minjiang, Tazang and Huya faults, in Sichuan Province, China, with the slip distributed on two distinct left-lateral strike-slip faults as shown in previous geodetic and seismic joint inversion. We use the seismic efficiency empirical relation to infer the average stress, and the average stress drop is estimated using the static stress drop. With the angle of the maximum principal stress and the nucleation fault determined from the relocated aftershocks, different principal stresses are calculated with different combinations of average stress and average stress drop. The initial normal and residual stresses can be determined using the projection of the principal stresses. The initial shear stresses are generated by adding the residual stress and the heterogeneous stress drop, which is generated by a set of Gaussian random numbers with a given mean and the variance, and mapped one-by-one with the given slip on the fault so that the area with a large slip has a large stress drop. By comparing the slip from dynamic rupture simulations and the input joint inversion result, we show that the case with a 36 MPa average stress and 2.1 MPa average stress drop provides the best-fitting slip snapshots. The dynamic Coulomb stress change shows that the 2017 Mw 6.5 Jiuzhaigou earthquake could bring the southeast of the Tazang fault and the middle of the Minjiang fault closer to failure. This work provides a new insight to understand the initial stresses of nature earthquakes.

Influences of train speed on permanent deformation of saturated soft soil under partial drainage conditions

To better understand the cumulative settlement of railway ground under the repeated train loads, the effects of cyclic stress (σd), initial static shear stress (σs), and effective mean principal stress (p0') on the permanent deformation of saturated silty clay are examined and evaluated through a series of cyclic load triaxial tests under the partial drainage conditions. As the results, the permanent strain of soil under different test conditions increases exponentially with the increase of Cyclic Stress Ratio (CSR = σd/2p0'), which can be predicted by an empirical prediction formula, irrespective of the cyclic stress (σd) and the effective mean principal stress (p0'). Besides, the influence of different embankment stiffness and train speed on the distribution of cyclic stress (σd) railway ground is analyzed by a three-dimensional (3D) numerical simulation. For ballastless track structures, reducing stiffness of embankment slightly affect cyclic stress (σd) on the railway ground, whereas increasing train speed significantly increases cyclic stress (σd) on the railway ground. Furthermore, the cumulative settlement of soft soil ground calculated by the Chinese code method (CM) and the dynamic method (DM) considering the train speed is compared, which indicates that CM may underestimate the settlement value of railway ground when the train speed increases (i.e., v = 112 m/s).

Hybrid Color Glass Condensate and hydrodynamic description of the Relativistic Heavy Ion Collider small system scan

Multi-particle correlation observables in the Relativistic Heavy Ion Collider small system scan are computed in a framework that contains both initial state momentum anisotropies from the Color Glass Condensate effective theory and final state hydrodynamic evolution. The initial state is computed using the IP-Glasma model and coupled to viscous relativistic hydrodynamic simulations, which are followed by microscopic hadronic transport. All parameters of the calculation were previously constrained using experimental data on Au+Au collisions at the same center of mass energy. We find that the qualitative features of the experimental data, such as the system and centrality dependence of the charged hadron momentum anisotropy, can only be reproduced when final state interactions are present. On the other hand, we also demonstrate that the details of the initial state are crucially important for the quantitative description of observables in the studied small systems, as neglecting the initial transverse flow profile or the initial shear stress tensor, which contain information on the momentum anisotropy from the Color Glass Condensate, has dramatic effects on the produced final state anisotropy. We further show that the initial state momentum anisotropy is correlated with the observed elliptic flow in all small systems, with the effect increasing with decreasing multiplicity. We identify the precise measurement of v2 in d+Au and Au+Au collisions at RHIC energy at the same multiplicity as a means to reveal effects of the initial state momentum anisotropy.

Effects of initial static shear stress orientation on cyclic behavior of calcareous sand

The current study investigated the effect of the initial static shear stress orientation on the liquefaction behavior of Hormuz Island calcareous sand. An experimental study was performed using nine monotonic and 43 cyclic undrained bidirectional simple shear tests. The experiments were conducted on loose and dense samples having different cyclic shear ratios and initial static shear ratios (α) at two orientations. It was found that, as the value of α increased, the shear behavior and failure mechanisms changed. The results showed that calcareous sand responded differently to changes in α and in the symmetrical tests (α = 0) showed higher resistance to liquefaction than siliceous sand. Contrary to siliceous sand, as α increased to 0.1, the value of K α increased to greater than 1 for loose Hormuz sand specimens. Moreover, an increase in α from 0.1 to 0.3 caused a slight increase (less than 10%) in the K α value for dense specimens. It was also observed that liquefaction resistance in the perpendicular loading mode was higher than in the parallel mode under the same conditions. It would appear that reversal of shear stress plays an important role in cyclic resistance and behavior in the parallel and perpendicular loading modes. A model is proposed to predict liquefaction resistance for calcareous sand in the presence of α.

Effect of High Temperature and Inclination Angle on Mechanical Properties and Fracture Behavior of Granite at Low Strain Rate

Comprehensive understanding of the effects of temperature and inclination angle on mechanical properties and fracture modes of rock is essential for the design of rock engineering under complex loads, such as the construction of nuclear waste repository, geothermal energy development and stability assessment of deep pillar. In this paper, a novel inclined uniaxial compression (inclined UCS) test system was introduced to carry out two series of inclined uniaxial compression tests on granite specimens under various inclination angles (0–20°) and treated temperatures (25–800 °C) at 5° inclination. Experimental results revealed that the peak compression stress and elastic modulus gradually decreased, while peak shear stress increased nonlinearly with the increasing inclination angle; the peak compression and shear stress as well as elastic modulus slightly increased from 25 to 200 °C, then gradually decreased onwards with the increasing temperature. The effect of temperature on peak axial strain was the same as that on peak shear displacement. Acoustic emission (AE) results suggested that the relationship between crack initiation stress, inclination angle and treated temperature followed a similar trend as that of the peak compression stress and elastic modulus. Particularly, the crack initiation (CI) stress threshold and shear stress corresponding to CI threshold under 800 °C were only 7.4% of that under 200 °C and revealed a severe heat damage phenomenon, which was consistent with the results of the scanning electron microscopy (SEM) with the appearance of a large number of thermal pores observed only under 800 °C. The failure modes tended to shear failure with the increasing inclination angle, indicating that the shear stress component can accelerate sliding instability of rocks. On the other hand, the failure patterns with different temperatures changed from combined splitting-shear failure (25–400 °C) to single shear failure (600 and 800 °C). The study results can provide an extremely important reference for underground thermal engineering construction under complex loading environment.

Laboratory and theoretical evaluation of impact of packing density, particle shape, and uniformity coefficient on erodibility of coarse‐grained soil particles

AbstractSedimentation – including erosion, transport, and deposition of coarse‐grained particles – is a primary and growing environmental, engineering, and agricultural issue around the world. Soil erosion occurs when the hydrodynamic force induced by flowing water exceeds the geotechnical resistance of soils, as measured by critical shear stress for initiation of soil‐particle motion. Even though various quantitative methods have been suggested with respect to different types of soil, the most widely accepted formula to estimate critical shear stress for coarse‐grained soil is a direct function of the median grain size of the soil particles; however, the erosion resistance of soils also varies with other geotechnical properties, such as packing density, particle shape, and uniformity coefficient. Thus, in this study, a combined rolling–lift model for particle detachment was derived based on theoretical analysis. A series of experimental flume tests were conducted with specimens prepared with standard soil types, as well as laboratory‐prepared mixtures of coarse‐grained soil to validate the theoretical model and determine the effect of other geotechnical properties on the erosion characteristics of coarse grains, coupled with the effect of median particle size. The results indicated that the median grain size is the primary variable determining the resistance of coarse grains, but the critical shear stress also varies with the packing density of the soil matrix. In addition, angular particles show more erosion resistance than rounded particles, and the erosion potential of a soil decreased when the grain is well graded (higher value of uniformity coefficient). Additionally, regression analysis was performed to quantify the effect of each parameter on the critical shear stress of coarse grains. © 2020 John Wiley & Sons, Ltd.

Experimental Study on the Deformation and Strength Characteristics of Saturated Clay under Cyclic Loading

The deformation and strength characteristics of saturated clay are studied through a cyclic triaxial test of clay in the Wenchuan earthquake area. Specifically, the effects of cyclic stress ratio, initial shear stress, and vibration frequency on the dynamic characteristics of saturated clay are analysed. Results show a failure strain in the dynamic strain development of saturated clay. Before the failure strain, the dynamic strain of soil develops slowly. After the failure strain, the soil strain increases sharply and leads to failure. Under the same confining pressure, the failure strain produced by different cyclic stress ratios has a linear relationship with the failure frequency. The dynamic strain development curve of saturated clay can be simplified to failure, transition, and stability types, which are mainly affected by the cyclic stress ratio. Initial shear stress and vibration frequency have significant effects on the deformation and strength characteristics of saturated clay. The larger the initial shear stress or the lower the vibration frequency is, the more sufficient the dynamic strain of soil develops and the fewer the number of cycles required to reach the same dynamic strain. Under the same number of cycles, the larger the initial shear stress or the lower the vibration frequency, the smaller the dynamic stress required to cause soil failure and the lower the dynamic strength of the soil. A turning point exists in the dynamic strength curve of clay. The smaller the initial shear stress or the higher the vibration frequency, the smoother the curve after the turning point and the smaller the tangent slope.

Corrigendum to “Experimental Study on the Effects of Initial Shear Stress and Vibration Frequency on Dynamic Strength of Saturated Sands”

Corrigendum to “Experimental Study on the Effects of Initial Shear Stress and Vibration Frequency on Dynamic Strength of Saturated Sands”

Influence of pulsed electrical discharge, hydrostatic pressure and temperature on rheological properties of sunflower cake during oil pressing

For the successful implementation of emerging electrical technologies in the oil pressing process, optimization of process parameters in combination with parameters from electrical process are crucial. The rheological property could be a simple and reliable efficiency indicatort of oil pressing. Knowledge of rheological properties is necessary for the design and development of appropriate equipment and process calculations. The objective of this work was to evaluate the effect of the following pre-treatments: pulsed electrical discharge (PED), temperature (28, 38 and 45 °C), overpressure (980, 1805 and 2800 Pa) and effect of initial oil content (40, 48.5 and 56%) on rheological properties of sunflower seed cake. The rheological behavior of sunflower seed cake was determined by using a rotational viscometer with a hydraulic system and thermostatic bath attached to the equipment. Using the mathematical apparatus and experimental data it was observed that the plastic viscosity of sunflower seed cake corresponds to the viscosity of the vegetable oil, which confirmed Bingham rheology assumption put forward in this work. Samples treated by PED had a modified material structure with an oil droplets and oil film on the surface. Single PED pre-treatment decreased initial shear stress from 24.36 to 22.89 Pa in samples where number of PED was 1800 per 60 s. Decrease in initial shear stress from 30.3 to 25.1 Pa was also observed when combination of temperature, pressure and PED was applied on seed cake. Reduction of the shear stress value, due to PED pre-treatment, enables to spend less energy during the oil pressing process. A positive linear relationship for overpressure and negative linear relationship for oil content and number of discharges on shear stress were obtained. The effect of temperature characterized by a decreasing of the plastic viscosity of the test material from 0.0985 to 0.0917 Pa s. The obtained parameters of the engineering rheological model allow prediction of rheological behavior of sunflower seed cake viscoplasticity flow over a wide range of shear rates in the pressing channel of the oil press.

Earthquake-induced flow liquefaction in fines-containing sands under initial shear stress by lab tests and its implication in case histories

Volume change of sands in shearing is either contractive or dilative depending on relative positions to SSL (Steady State Line) on the void ratio versus effective stress state diagram. This strongly affects how sands tend to liquefy during earthquakes and behave thereafter under initial shear stresses loaded by sloping ground or nearby structures. Torsional simple shear undrained cyclic loading test results are addressed here to categorize liquefaction behavior of sand specimens with various relative densities and fines contents Fc so that the specimens are positioned on both sides of SSL under the effect of different initial shear stress. A flow-type failure on the contractive side of SSL is particularly focused, and how to evaluate its potential in terms of Fc under initial shear stress is discussed. Lastly, unprecedented liquefaction-induced flow failures recently occurred in very gentle slopes are addressed to discuss their basic mechanism and possible scenario in view of the findings in the laboratory tests.

Experimental Study on the Effects of Unloading Normal Stress on Shear Mechanical Behaviour of Sandstone Containing a Parallel Fissure Pair

To gain deeper insight into the effects of unloading normal stress on shear mechanical behaviour, laboratory tests are carried out on the red-sandstone specimens containing a parallel fissure pair under the constant shear stress and the unloading normal stress. The results reveal that the trace of the entire rupture surface is mainly controlled by the rock bridge, and the impacts of the rupture surfaces of the unloading tests are narrower than those of the direct shear tests. Tensile failure, tension–shear failure, shear failure, and two-stage failure are observed, the failure rules of rock bridges are further summarized according to the ranges of the length and inclination of the rock bridge. The shear strength of the normal unloading test has a slight increase compared with that of the direct shear test. With an increase in the initial normal/shear stress, the shear strength of rock specimens increase; under the low to medium initial stress conditions, the shear strength increment has a linear growth tendency, but under the medium to high initial stress conditions, the growth trend slows down. The ratio of shear deformation on rupture surface increases with the increase of the initial shear stress but decreases with the increase of the initial normal stress. The ratio of shear deformation on rupture plane increases with the increase of the initial shear stress, and decreases with the increase of the initial normal stress, There is a little difference in the deformation ratio (shear damage deformation divided by tensile damage deformation, ΔDrs/ΔDrn) between the observed tensile failure and tension–shear failure. The dominate damage deformation under different geometric conditions is closely related to the failure patterns.

Moment rate of the 2018 Gulf of Alaska earthquake

The 2018 Gulf of Alaska earthquake (Mw 7.9) occurred in a region of the Pacific plate southwest of the Alaskan subduction zone. The earthquake was a strike-slip event, with the hypocenter located at a depth of about 25 km and a seismic moment equal to 0.96 × 1021 Nm. Two observed moment rates have been obtained by the Geoscope Observatory, France, and by the United States Geological Survey (USGS). Both of them can be interpreted as due to the failure of two asperities on the fault surface. We consider a discrete fault model, with two asperities of different areas and strengths, and show that the observed moment rates can be reproduced by appropriate values of the model parameters, as inferred from the available data. A good fit to the observed moment rates is obtained by a sequence of three dynamic modes of the system, including a phase of simultaneous slip of the asperities. The two moment rates are however characterized by different initial conditions, in terms of different initial shear stress distributions on the fault. Shear stresses on the asperities are calculated as functions of time during the event and show a similar evolution in the two cases, but with different final values. The model results show that the presence of simultaneous asperity motion can significantly increase the seismic moment of a large earthquake.

Recent advances in pore water pressure and liquefaction characteristics of low plasticity silty sands subjected to cyclic loading

Low plasticity sand-silt mixtures are very common in Italy either in natural depositional environment or in man-made earth-fill, hence the knowledge of their behavior is a crucial aspect in many practical applications. Due to higher compressibility features, significant strains and strength loss may be triggered by earthquakes. The results of a laboratory-based investigation undertaken on undisturbed samples of low plasticity silty-sandy soils recovered from a bank stretch after the 2012 Emilia Romagna earthquake in Italy, when serious damages and widespread liquefaction events were observed, are herein presented. Special emphasis was given to susceptibility to liquefaction and pore water pressure response in presence of an initial static shear stress. As part of the present work, the results of undrained cyclic simple shear (CSS) tests carried out on reconstituted specimens of sand-fines mixtures, covering a range of non plastic fines contents from 0% to 40%, were used for predicting undrained cyclic resistance through the concept of equivalent granular void ratio, e*. The conceptual framework based on e* appears appropriate for streamlining the effect of fines on cyclic liquefaction resistance of these intermediate soils, provided that fines content is less than a limiting value. Since an important stage in the assessment of liquefaction potential is to predict excess pore water pressure during cyclic loading, the results of CSS tests were also utilized for analysing pore water pressure generation models of silty sands over a wide range of fines contents.

Effects of induced anisotropy on multiple liquefaction properties of sand with initial static shear

The multiple liquefaction phenomenon has been attracting the attention of more and more researchers and engineers since the 2010–2011 Christchurch Earthquakes and the 2011 Great East Japan Earthquake. However, little has been known about the multiple liquefaction properties of sloped grounds. In this study, therefore, multiple liquefaction tests that consider the initial static shear stress, which have never been conducted before, were carried out with a special designed apparatus, the stacked-ring shear apparatus. A series of multiple liquefaction tests revealed that induced anisotropy, which is weak against the loading opposite to the direction of the initial static shear stress, was produced by the liquefaction of a sloped ground. As a result, a significant decrease in the liquefaction resistance during the next cyclic of shearing occurred. The indicators which influenced the magnitude of anisotropy were also discussed from the perspective of the reconsolidation procedures, the magnitude of initial static shear stress, and the type of ending of the previous liquefaction stage. In addition, it turned out that in the multiple liquefaction test with a larger initial static shear stress, the re-liquefaction resistance was higher because the shear stress opposite to the direction of the initial static shear stress, causing large negative dilatancy due to anisotropy, was smaller in that test.

Predicting the Tensile Behavior of Ti-6.6Al-3.3Mo-1.8Zr-0.29Si Alloy via the Temperature-Dependent Crystal Plasticity Method.

Uniaxial tensile flow properties of a duplex Ti-6.6Al-3.3Mo-1.8Zr-0.29Si alloy in a temperature range from 213 K to 573 K are investigated through crystal plasticity modelling. Experimental results indicate that the initial yield stress of the alloy decreases as the temperature increases, while its work-hardening behavior displays temperature insensitivity. Considering such properties of the alloy, the dependence of the initial critical resolved shear stress (CRSS) on temperature is taken into account in the polycrystal plasticity modelling. Good coincidence is obtained between modelling and the experimental results. The determined values of CRSS for slip systems are comparable to the published data. The proposed polycrystalline model provides an alternative method for better understanding the microstructure–property relationship of α + β titanium alloys at different temperatures in the future.

Bounding surface plasticity model for liquefaction of sand with various densities and initial stress conditions

A comprehensive data package of cyclic simple shear tests was used to critically check and revise a plasticity model for sand. These cyclic simple shear tests were performed using Monterey No. 0/30 sand with different relative densities and under complex loading conditions including asymmetrical cyclic loading with various initial shear stresses and overburden pressures. The newly revised model carries several novel concepts: using a strain increment dependent flow rule and loading/unloading criterion that results in explicit integrations of stress-strain model equations; the density dependency extended to more ingredients of the model structure, especially to plastic shear and bulk moduli that achieves ‘one set of model parameters for one sand’ for cyclic loading responses; and the appropriate use of three intrinsic history dependent variables, i.e., the latest stress reversal point, the virgin loading (i.e. maximum pre-stress) stress ratio, and the accumulated plastic deviatoric strains that contribute greatly to the enhanced capabilities of the revised model. The model is first calibrated based on three symmetrical cyclic loading responses. Using the single set of model parameters, the model is then used to predict the sand behavior under asymmetrical cyclic loadings and different initial confining pressures. Lastly, the model predictions are checked against empirical correlations established between cyclic resistance ratio (CRR) with initial shear stresses and confining pressures, or the commonly referred to Kα and Κσ effects. The obtained model predictions not only compare relatively well with the test data, but the Kα and Κσ effects based on model predictions follow the trend of empirical relationships too.

Effect of temperature on the structure of paste slurry at low constant shear rate

ABSTRACT The effect of temperature on the paste slurry structure under low constant shear rate was studied and the measurements of rheological curve were approached by means of the Brookfield R/S rheometer. The results showed that the distinction between the elastic, plastic and viscous properties of the paste slurry, the static yield stress, and dynamic yield stress were related to the shear rate. When the constant low shear rate was 0.05 s−1, the rheological curve of the paste slurry can effectively distinguish the elastic, plastic and viscous phases and can accurately test the static yield stress and dynamic yield stress, which better reflected the change characteristics of the paste slurry structure. When the temperature rose, the elasticity, plasticity, and viscosity of the paste slurry had enhanced, the initial shear stress and dynamic yield stress increased, the storage modulus and the static yield stress increased similarly. The plastic strain energy increased first and then decreased with increasing temperature. The time to reach the static yield stress was basically the same, independent of the temperature change, the time of reaching the dynamic yield stress increased with the increase of temperature. As the shearing continued, the time during the paste slurry structure reached the steady state was substantially equal and did not change with temperature.