“…Moreover, the creep deformation of overconsolidated sand is much less than normally consolidated sand. The creep deformation is less when overconsolidated ratio goes bigger [27]. However, creep strain approaches a similar time relationship after a transient period (15,20).…”
Multistage constant stress rates loading-creep tests were carried out on air-dried slate rockfill. The influences of the loading history on the creep deformation of rockfill were investigated, including the prior loading stress rate, the stress increment size of prior loading, and the history of early loading and early creep, in which 'prior loading' was defined as the loading just before the creep in the current loading-creep step, while 'early loading' or 'early creep' was that before prior loading. Regardless of the size of the prior loading stress increment, as long as there was a loading-creep process before this step of loading-creep, the time development process of the subsequent creep strain and strain rate was related to the creep stress and the prior stress rate before creep. The creep process had no obvious relationship with the early stress rate in the last step, as well as the earlier loading history before the last creep. The subsequent creep strain was positively correlated with the creep stress and prior stress rate. When the prior stress rate before creep was high, the subsequent creep rate and time were linear in the double logarithmic coordinate. The creep rate and time accorded with a power-law relationship which appeared to be the baseline for creep development. Whatever the prior loading rate, the creep rate time progression in the middle and later stages of the subsequent creep conformed to this baseline. Besides, when the prior stress rate was lower than a certain value, the initial strain rate of subsequent creep was significantly lower than the baseline, which decreases less until several minutes after the start of creep. The development law of creep rate at the initial stage could be generalized as a straight horizontal line in double logarithmic coordinates, which is kept almost unchanged for a certain time. The strain rate would not resume the power-law relationship with time until it approached the base creep rate. The inheritance and hysteresis of different prior strain rates to the initial stage of subsequent creep due to prior stress rate with the discrepancy, result in differences in the creep magnitude and time development process of creep rate. Moreover, the prior low strain rate both depressed the initial rate of subsequent creep and pushed back the initiation time of subsequent creep according to the power law.
“…Moreover, the creep deformation of overconsolidated sand is much less than normally consolidated sand. The creep deformation is less when overconsolidated ratio goes bigger [27]. However, creep strain approaches a similar time relationship after a transient period (15,20).…”
Multistage constant stress rates loading-creep tests were carried out on air-dried slate rockfill. The influences of the loading history on the creep deformation of rockfill were investigated, including the prior loading stress rate, the stress increment size of prior loading, and the history of early loading and early creep, in which 'prior loading' was defined as the loading just before the creep in the current loading-creep step, while 'early loading' or 'early creep' was that before prior loading. Regardless of the size of the prior loading stress increment, as long as there was a loading-creep process before this step of loading-creep, the time development process of the subsequent creep strain and strain rate was related to the creep stress and the prior stress rate before creep. The creep process had no obvious relationship with the early stress rate in the last step, as well as the earlier loading history before the last creep. The subsequent creep strain was positively correlated with the creep stress and prior stress rate. When the prior stress rate before creep was high, the subsequent creep rate and time were linear in the double logarithmic coordinate. The creep rate and time accorded with a power-law relationship which appeared to be the baseline for creep development. Whatever the prior loading rate, the creep rate time progression in the middle and later stages of the subsequent creep conformed to this baseline. Besides, when the prior stress rate was lower than a certain value, the initial strain rate of subsequent creep was significantly lower than the baseline, which decreases less until several minutes after the start of creep. The development law of creep rate at the initial stage could be generalized as a straight horizontal line in double logarithmic coordinates, which is kept almost unchanged for a certain time. The strain rate would not resume the power-law relationship with time until it approached the base creep rate. The inheritance and hysteresis of different prior strain rates to the initial stage of subsequent creep due to prior stress rate with the discrepancy, result in differences in the creep magnitude and time development process of creep rate. Moreover, the prior low strain rate both depressed the initial rate of subsequent creep and pushed back the initiation time of subsequent creep according to the power law.
“…From the perspective of material properties, the macroscopic essence of the strain rate effect was the hysteresis phenomenon of deformation damage during loading. As the loading rate increased, the specimen exhibited a higher stress state at the same strain value due to delayed deformation damage 34 . Figure 8 Loadādisplacement curves of hollow steel tubes under different loading rates.…”
An innovative energy-absorbing and bearing structure was proposed, which incorporated the coupling of glass microspheres with a metal tube. Glass microsphere-filled steel tube (GMFST) column, consisting of external steel tube and inner glass microspheres, was expected to give full play to the energy-absorbing and load-bearing capacities of the particle while restricting particle flow from collapsing, thereby enhancing the overall structural strength. Four groups of steel tubes and the GMFST specimens were designed and subjected to axial compression tests at four different loading rates to investigate the performance of the structure. These tests aimed to analyze the deformation mode, mechanical response, and energy absorption capacity of the GMFST columns under quasi-static to low-speed compression conditions. The results indicated that the deformation process and failure mode of GMFST columns were similar to those of hollow steel tubes, albeit with a different post-buckling mode. Filling the steel tubes with glass microspheres reduced the load fluctuation range, moderated loadādisplacement curves, and exhibited a strain rate strengthening effect. The GMFST columns demonstrated superior energy absorption capacity, with significant increases in crush force efficiency, the averaged crush force, and the total absorbed energy, particularly in terms of subsequent support capacity. The load-increasing reinforcement properties enabled GMFST columns to overcome the limitations associated with the unstable post-buckling path of energyāabsorbing damping structure, exhibiting outstanding load-bearing performance and stability in the later stages. The results provided valuable guidelines for designing and engineering high-performance GMFST columns, serving as a new type of energy-absorbing and supporting structure.
“…Furthermore, the particle size and shape distributions can be determined by the area of each fragment. Figure 2 shows a comparison of the initial particle size and shape distributions obtained by two-dimensional image analysis (Zeng and Liu, 2023a;Zeng and Liu, 2023b) and simulation. The particle size and shape of the crushable agglomerates in the simulation are close to those of actual coral sand particles.…”
Section: Particle Size and Shape Distribution Acquisitionmentioning
confidence: 99%
“…It is well known that coral sand particles are usually irregular, porous, and fragile. The particle size and shape significantly change when particle breakage occurs, and the mechanical properties of coral sand are considerably affected (Rui et al, 2020;Xiao et al, 2022;Zeng and Liu, 2023a;Zeng and Liu, 2023b). Therefore, it is necessary to explore the interaction between particle shape and particle breakage and analyze their combined effects on the mechanical behavior of coral sand for better foundation designs in offshore and ocean engineering.Many studies have been conducted to investigate the influence of particle breakage on the mechanical properties and shape evolution of breakable granular materials.…”
A series of biaxial tests with different initial particle shapes, confining pressures, bond strengths and depositional angles were conducted on coral sand by using a 2D discrete element method simulation. The interactions between particle shape and particle breakage were investigated, and their combined effects on the mechanical behavior of coral sand were analyzed. The test results showed that particle breakage considerably weakens the effect of particle shape and inherent anisotropy on shear strength. The difference between the internal friction angles of unbreakable and breakable agglomerates ĪĻ decreases with increasing aspect ratio AR, sphericity S, and depositional angle Īø. There exists a unique relationship between the relative breakage BrDe and the input energy E for the same agglomerates, which is independent of axial strain and confining pressure. However, this relationship is significantly influenced by the agglomerate shape and depositional angle, and irregular and low depositional angle specimens are more easily broken. In addition, the evolution of the aspect ratio AR and sphericity S of agglomerates was controlled by particle breakage, regardless of the axial strain, confining pressure, bond strength and depositional angle, and these trends were determined by the initial particle shape.
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