142 research outputs found
Recommended from our members
Experimental and Numerical Modeling of Seismic Earth Pressures on Retaining Walls with Cohesive Backfills
No full textObservations from recent earthquakes show that all types of retaining structures with non-liquefiable backfills perform very well and there is limited evidence of damage or failures related to seismic earth pressures. Even retaining structures designed only for static loading have performed well during strong ground motions suggesting that special seismic design provisions may not be required in some cases. The objective of this study was to characterize the seismic interaction of backfill-wall systems using experimental and numerical models, with emphasis on cohesive soils, and to review the basic assumptions of current design methods.In the experimental phase of this research, two sets of centrifuge models were conducted at the Center for Geotechnical modeling in UC Davis. The first experiment consisted of a basement wall and a freestanding cantilever wall with level backfill, while the second one consists of a cantilever wall with sloping backfill. The soil used in the experiments was a compacted low plasticity clay. Numerical simulations were performed using FLAC2-D code, featuring non-linear constitutive relationships for the soil and interface elements. The non-linear hysteretic constitutive UBCHYST was used to model the level ground experiment and Mohr-Coulomb with hysteretic damping was used to model the sloping backfill experiment. The simulations captured the most important aspects of the seismic responses, including the ground motion propagation and the dynamic soil-structure interaction. Special attention was given to the treatment of boundary conditions and the selection of the model parameters. The results from the experimental and numerical analysis provide information to guide the designers in selecting seismic design loads on retaining structures with cohesive backfills. The experimental results show that the static and seismic earth pressures increase linearly with depth and that the resultant acts at 0.35H-0.4H, as opposed to 0.5-0.6H assumed in current engineering practice. In addition, the observed seismic loads are a function of the ground motion intensity, the wall type and backfill geometry. In general, the total seismic load can be expressed using Seed and Whitman's (1970) notation as: Pae=Pa+dPae, where Pa is the static load and dPae is the dynamic load increment. While the static load is a function of the backfill strength, previous stress history and compaction method, the dynamic load increment is a function of the free field PGA, the wall displacements, and is relatively independent of cohesion. In level ground, the dynamic load coefficient can be expressed as dKae=1/2gH2(0.68PGAff/g) for basement walls and dKae=1/2gH2(0.42PGAff/g) for cantilever walls; these results are consistent with similar experiments performed in cohesionless soils (Mikola & Sitar, 2013. In the sloping ground experiment the seismic coefficient came out to dKae=1/2gH2(0.7PGAff/g), which is consistent with Okabe's (1926) Coulomb wedge analysis of the problem. However, that slope was stable under gravity loads even without the presence of the retaining wall (FS=1.4). Measured slope displacements were very small and in reasonable good agreement with the predictions made with the Bray and Travasarou (2007) semi-empirical method. The experimental data was not sufficient to determine accurately the point of action of the seismic loads. However, the numerical simulations and Okabe's (1926) limit state theory suggest that the resultant acts between 0.37H-0.40H for typical values of cohesion. While the resultant acts at a point higher than 0.33H with increasing cohesion, the total seismic moment is reduced due to the significant reduction in the total load Pae, particularly for large ground accelerations. The results also show that typical retaining walls designed with a static factor of safety of 1.5 have enough strength capacity to resist ground accelerations up to 0.4g. This observation is consistent with the field performance of retaining walls as documented by Clough and Fragaszy (1977) and the experimental results by al Atik and Sitar (2010) and Geraili and Sitar (2013).The evaluation of earth pressures at the wall-backfill interface continues to be a technical challenge. Identified sources of error in the present study include the behavior of pressure sensors, the geometric and mass asymmetry of the model and the dynamic interaction between the model and the container. While these centrifuge experiments reproduced the basic response of prototype models, ultimately, instrumented full-scale structures are most essential to fully characterize the response of tall walls and deep basements with varieties of backfill
Recommended from our members
Constitutive Modeling of Weakly Cemented Sands
No full textAbstractConstitutive Modeling of Weakly Cemented SandsByChukwuebuka NwekeDoctor of Philosophy in Civil and Environmental EngineeringUniversity of California, BerkeleyProfessor Nicholas Sitar, ChairWeakly cemented sands are prominent in nature and can be found in many geologic deposits all over the world. The same is true for loose sand deposits, which conversely, create undesirable conditions for engineering design and execution. The primary difference between weakly cemented sand and loose sand is the presence of cementation, which enhances the mechanical properties and behavioral response of the former. As a result, the ability to replicate this cementation feature and use it to improve loose sand deposits has been (and is currently) an area of intense investigation and research. Traditional ground improvement methods employ the use of Portland cement via jet grouting, deep soil mixing, compaction grouting, and many others. These methods are considered “environmentally unfriendly” due to their use of “high-embodied” energy materials. A potential solution may lie in the realm of biocementation where sustainable ground improvement technologies use microbial metabolic activity to activate chemical reactions that inevitably induce precipitation of calcium carbonate, which accumulates at the grain contacts and binds the soil skeleton. These artificial cemented granular materials (biocement or Portland cement), as well as naturally cemented materials often serve as the foundation material or support foundation structures of varying overlying infrastructures. For this reason, there is a need for tools that are capable of assessing the improvements (or enhanced characteristics) of these types of sands, and predicting the performance under varying loading conditions.The focus of this dissertation is to gain a better understanding of the mechanics of cemented and uncemented sands, considering the vast similarities between both states, but highlighting the distinctions that may give insights into how the effects of cementation alter the mechanical properties of sands. Laboratory triaxial tests were used as a means to investigate the mechanical behavior. It was observed that light cementation preserved the characteristics of stress-strain response typical of uncemented sands, while it also significantly enhanced the strength and stiffness for even low levels of cement content. This was attributed to strengthening of the soil fabric that resulted from the formation of “cement bridges” at the interparticle contacts, which induced increased strength in shear and in compression. Furthermore, it was found that the stress-dilatancy theories used in modeling uncemented sands also apply to weakly cemented sands. Specifically, it was shown that the critical state conditions were relatively unaffected by cementation, leaving the dilatancy to harbor most, if not all, of the cementation enhancement effects. Nor-Sand “bounding plasticity” model was employed as the foundation model due to its ability to represent dilation of the material at low confining pressures. As such, attention was placed on enhancing the dilation component of the model via the inclusion of a cementation parameter that is a function of the amount of cement. In addition, the cementation parameter is capable of evolving with accumulated deformation, allowing for the transition from the cemented to uncemented state. The new model, N-We-Ce (Nor-Sand for Weakly Cemented sands) maintains usage of the majority of parameters from the Nor-Sand base model, while adding 4 – 6 new parameters (depending on the type of test data) describing the contribution of cementation to the strength and stiffness of the sand
Recommended from our members
3D Block Erodibility: Dynamics of Rock-Water Interaction in Rock Scour
No full textAbstract3D BLOCK ERODIBILITY: DYNAMICS OF ROCK-WATER INTERACTIONIN ROCK SCOURbyMichael Freeman GeorgeDoctor of Philosophy in Engineering – Civil & Environmental EngineeringUNIVERSITY OF CALIFORNIA at BERKELEYProfessor Nicholas Sitar, ChairErosion of rock by flowing water is an integral process in the evolution of natural landscapes as well as a critical hazard for key infrastructure such as dams, spillways, bridges and tunnels. The removal of individual blocks of rock is one of the primary mechanisms by which rock scour can occur. This research examined the influence of 3D geologic structure on erodibility of rock blocks with the aim to understand the basic mechanics of the process as well as to develop a predictive framework for block erodibility. To do this, a multifaceted research program was established. Field investigation of a prototype site in the Sierra Nevada Mountains in northern California was used as a basis for the development of an extensive series of hydraulic model experiments, which were complemented by theoretical deterministic and stochastic analyses based on 3D block theory.Past experimental studies have been limited to simplified cubic or rectangular block geometries in laboratory settings, with very little data regarding hydrodynamic pressures surrounding 3D blocks and subsequent block response to hydrodynamic loading. For more complex block shapes (as often found in nature), such simplifications in geometry can be problematic as the 3D orientation of discontinuities within the rock mass largely influence block removability, kinematics and stability. Accordingly, a major focus of this research was to obtain a high resolution experimental data set from both field and laboratory settings for hydraulic and rock mass parameters pertaining to 3D non-cubic block geometries.Field work was carried out in a prototype setting at an actively eroding unlined rock spillway at a dam site in northern California. High resolution rock mass data was obtained using light detection and ranging (LiDAR) scanning which permitted statistical characterization of rock mass parameter variability for use in a probabilistic scour prediction model. Two instrumented artificial rock block were cast in existing block molds to capture hydrodynamic pressures and block displacements during spill events. Climatic conditions in northern California, however, prevented reservoir discharges on the blocks such that no data to date have been collected.A scaled physical hydraulic model, loosely representing conditions at the above field site was also performed. The advantage of the laboratory model was the ability to investigate a broad range of variables and flow conditions not readily achievable in a field setting. For the model, an instrumented 3D block mold was constructed that could be rotated with respect to the flow direction to study the influence of discontinuity orientation on block erodibility. As would be expected, the block erodibility threshold was found to be highly dependent on the flow direction. This can be attributed to changes in kinematic constraints associated with the block mold geometry in the downstream direction as well as the relative profile of block protrusion above the channel bottom. Three separate block response types were observed which are closely associated with block kinematic resistance. Pressure values, represented by the dimensionless average dynamic pressure coefficient, Cp, were determined as a function of the block mold orientation, turbulence intensity, block protrusion height, and flow velocity. Overall, the average hydrodynamic pressures on block faces were found to be adequate in the evaluation model block stability. Accordingly, the data presented herein may be applied to a variety of flow conditions.A reliability-based, block theory framework was also developed for evaluation of 3D block erodibility given parameter uncertainty associated with the inherent variability within the rock scour process. Block theory provides a rigorous analytical methodology to identify removable blocks, determine potential failure modes, and assess 3D block stability. Block stability is evaluated in a pseudo-static manner using block theory limit equilibrium and kinematic constraint equations. Theoretical predictions for block erodibility threshold compare well with those obtained from hydraulic model testing for both high and low turbulence flows. Improved prediction was observed for some cases when a mobilized joint friction angle was used.Applicability of the reliability-based, block theory methodology was demonstrated through two example analyses for the field site in northern California. Removable blocks from the spillway channel were identified and analyzed deterministically to determine their erodibility threshold. Variability in rock mass parameters was included based on statistical analysis of the LiDAR data set to calculate the failure probability of the block with the lowest erodibility threshold. FORM analysis for parameter importance indicates block protrusion height, followed by rock joint orientations and flow velocity, are the most influential variables on block stability, while joint friction angle is relatively insignificant.From a design standpoint, the benefit of the proposed methodology is that 3D, site-specific geologic structure information can be incorporated into evaluation of rock mass erodibility. Variability in site parameters can be addressed in a probabilistic manner to classify locations most susceptible to erosion as well as identify the most influential variables affecting rock block stability. This can lead to more efficient scour remediation designs as well as more focused field and laboratory efforts to investigate parameters with the most impact on the system. Furthermore, reliability data can be useful for designers and infrastructure owners in decision making and management of risk at a specific site
Slavo Grum\u27s cultural heritage in Šmartno pri Litiji
No full textDiplomsko delo se ukvarja s kulturno zapuščino Slavka Gruma v Šmartnem pri Litiji in poskuša ugotoviti, v kolikšni meri je vplival na kraj. Zanima nas, na kak način je Slavko Grum biografsko povezan s Šmartnim, kako je Šmartno dojemal in ga zapisal v pismih in kakšna je kulturna podoba Šmartnega, nastala pod njegovim vplivom, ki se odraža preko poimenovanj ustanov, obeležij in organizacije dogodkov. Po pregledu biografije Slavka Gruma sledi ugotovitev, da Šmartno ni le njegov rojstni kraj, pač ga je redno obiskoval med študijskimi počitnicami, vsaj do jeseni 1926, poleg tega pa ga je s Šmartnim povezovala močna vez z njegovo muzo Jožo Debelak, prav tako Šmarčanko. Do Šmartnega Slavko Grum goji dvojen odnos: hkrati ga dojema kot domač dom in hkrati kot dolgočasno podeželsko mesto. Po Slavku Grumu je v Šmartnem poimenovana ena lokacija, rojstna hiša je označena s spominsko ploščo, hišo je prenovila prejšnja lastnica in ostaja v zasebni lasti. Dogajanje v povezavi s kulturno zapuščino Slavka Gruma ni enakomerno, pač pa strnjeno ob obletnicah rojstva in smrti, tudi ob prihajajoči 120-letnici rojstva se načrtuje več dogodkov: izid dveh knjig s tematiko Slavka Gruma in postavitev njegovega kipa. Večje zanimanje za Gruma se šele prebuja, v načrtih je odprtje Grumovega ustvarjalnega centra, ki bi poskrbel za celostno skrb za Grumovo in splošno lokalno kulturno dediščino, a prihodnost tega centra ostaja nedorečena.The diploma paper deals with the cultural heritage of Slavko Grum in Šmartno pri Litiji and the impact he left on the village. The research focuses on the author’s biographical connection to Šmartno, his understanding and portrayal of the place in his letters and the cultural image of Šmartno that developed under his influence which is apparent in the names of establishments, memorials and organised events. His biography suggests that Šmartno was not only Grum’s place of birth, but also a destination he regularly visited during his holiday, at least till 1926. He also developed a strong bond with his muse, Joži Debelak, who was also from Šmartno. Grum had an ambivalent attitude towards the town. It was a place he called home as well as a boring rural town. Šmartno has named one location after the author. The house of his birth is marked with a memorial plaque and was renovated by the former owner. The house remains in private possession. Celebrations regarding Grum’s cultural heritage are inconsistent, centred mostly around the days marking his birth and death. Many events are planned for the upcoming 120th anniversary of his birth, including the publishing of two books on Slavko Grum and uncovering his statue. Though we can observe an increase in the interest in Slavko Grum, the plans for establishing Grum’s creative centre which would care for the author’s and the local cultural heritage, remain unclear
Recommended from our members
Seismic Earth Pressures on Retaining Structures and Basement Walls in Cohesionless Soils
No full textObservations of the performance of basement walls and retaining structures in recent earthquakes show that failures of basement or deep excavation walls in earthquakes are rare even if the structures were not designed for the actual magnitude of the earthquake loading. Failures of retaining structures are most commonly confined to waterfront structures retaining saturated backfill with liquefaction being the critical factor in the failures. Failures of other types of retaining structures are relatively rare and usually involve a more complex set of conditions, such as sloping ground either above or below the retaining structure, or both. While some failures have been observed, there is no evidence of a systemic problem with traditional static retaining wall design even under quite severe loading conditions. No significant damage or failures of retaining structures occurred in the recent earthquakes such as Wenchuan earthquake in China (200) and, or subduction zone generated earthquakes in Chile (2010) and Japan (2011). Therefore, this experimental and analytical study was undertaken to develop a better understanding of the distribution and magnitude of seismic earth pressures on cantilever retaining structures. The experimental component of the study consists of two sets of dynamic centrifuge model experiments. In the first experiment two model structures representing basement type setting were used, while in the second test a U-shaped channel with cantilever sides and a simple cantilever wall were studied. All of these structures were chosen to be representative of typical designs. Dry medium-dense sand with relative density on the order of from 75% to 80% was used as backfill. Results obtained from the centrifuge experiments were subsequently used to develop and calibrate a two-dimensional, nonlinear, finite difference model built on the FLAC platform.The centrifuge data consistently shows that for the height of structures considered herein, i.e. in the range of 20-30 ft, the maximum dynamic earth pressure increases with depth and can be reasonably approximated by a triangular distribution This suggests that the point of application of the resultant force of the dynamic earth pressure increment is approximately 1/3H above the base of the wall as opposed to 0.5-0.6 H recommended by most current design procedures. In general, the magnitude of the observed seismic earth pressures depends on the magnitude and intensity of shaking, the density of the backfill soil, and the type of the retaining structures. The computed values of seismic earth pressure coefficient (∆Kae) back calculated from the centrifuge data at the time of maximum dynamic wall moment suggest that for free standing cantilever retaining structures seismic earth pressures can be neglected at accelerations below 0.4 g. While similar conclusions and recommendations were made by Seed and Whitman (1970), their approach assumed that a wall designed to a reasonable static factor of safety should be able to resist seismic loads up 0.3 g. In the present study, experimental data suggest that seismic loads up to 0.4 g could be resisted by cantilever walls designed to an adequate factor of safety. This observation is consistent with the observations and analyses performed by Clough and Fragaszy (1977) and Fragaszy and Clough (1980) and Al-Atik and Sitar (2010) who concluded that conventionally designed cantilever walls with granular backfill could be reasonably expected to resist seismic loads at accelerations up to 0.4 g.Finally, numerical models using FLAC finite difference code were quite successful and able to produce a reasonably good agreement with the results of the centrifuge experiments. However, while the finite difference models were able to capture the main aspects of the seismic response observed in the centrifuge experiments, the results of the analyses were highly sensitive to the selection of soil and interface parameters. Therefore, numerical models used for future designs should be carefully calibrated against experimental data in order to provide reliable results
Recommended from our members
Development of a Coupled 3-D DEM-LBM Model for Simulation of Dynamic Rock-Fluid Interaction
No full textScour of rock is a challenging and interesting problem that combines rock mechanicsand hydraulics of turbulent flow. On a practical level, rock erosion is a critical issue facingmany of the world’s dams at which excessive scour of the dam foundation or spillway cancompromise the stability of the dam resulting in significant remediation costs, if not directpersonal property damage or even loss of life. The most current example of this problem isOroville Dam in Northern California where massive scour damage to both the service andemergency spillways during the flood events of February 2017 led to the evacuation of morethan 188,000 people living downstream of the dam.This research is specifically aimed at developing the ability to numerically evaluate rock-water interaction, building upon the experimental and analytical work by George and Sitar. The focus is on producing simulation techniques capable of consid-ering the interaction between three-dimensional polyhedral rock blocks interacting with fluidsuch that the complex shape of the blocks is captured in both the fluid and solid numericalmodels. Accounting for the rock block geometry and orientations is essential in capturingthe correct kinematic response.To this end, a three-dimensional, open-source program to generate the fractured rockmass was developed based on a linear programming approach. The application runs onApache Spark which enables it to run locally, on a computer cluster or on the Cloud. Theprogram automatically maintains load balance among parallel processes and can be scaledup to meet computational demands without having to make any changes to the underlyingsource code. This enables the program to generate real-world scale block systems containingmillions of blocks in minutes.The second stage of this research effort focused on developing a new open-source DiscreteElement Method (DEM) program capable of analyzing the kinematic response of fracturedrock. The contact detection computations for DEM are also based on a linear programmingapproach such that similar logic and data structures can be used in both the block generationand DEM code, though the DEM code is written in C++. The program was validated against2analytical solutions as well as other numerical solutions and has been shown to accuratelycapture the kinematic response of three-dimensional polyhedral rock blocks.The DEM formulation was then extended to perform coupled fluid-solid interaction anal-yses by coupling it with the weakly compressible Lattice Boltzmann Method (LBM). Anew algorithm, which extends the partially saturated approach, was developed to considerthree-dimensional convex polyhedra moving through the fluid domain. The algorithm usesboth linear programming and simplex integration for the coupling process. The LBM codeand the new fluid-solid coupling algorithm were validated against experimental data andthe capabilities of the new coupled DEM-LBM implementation were explored by evaluatingthe performance of the program in simulating several different problems involving fluid-solidinteraction. The results show that the program is able to accurately capture the interactionbetween polyhedral rock blocks and fluid; however, further performance improvements arenecessary to simulate realistic, field scale problems. Particularly, adaptive mesh refinementand multigrid methods implemented in a parallel computing environment will be essentialfor capturing the highly computationally intensive and multiscale nature of rock-fluid inter-action
Recommended from our members
Master's thesis recital (composition)
No full textBreathing sunlight : for violin and violoncello duo (Sean Riley, violin ; Seth Russell, violoncello) -- Lagan Bina : for Hindustani vocalist and string quartet (Saili Oak, Hindustani vocalist ; Sara Sasaki, violin ; Shruthi Kattumenu, violin ; Sean Flynn, viola ; Akshaya Avril Tucker, violoncello) -- Shaam : for sitar and sinfonietta (Aruna Kharod, sitar ; Nicholas Perry Clark, conductor ; prismatx ensemble & guests) -- Three songs : for Hindustani vocalist, soprano, and sinfonietta (Saili Oak, Hindustani vocalist ; Suzanne Lis, soprano ; Nicholas Perry Clark, conductor ; prismatx ensemble & guests)Musi
Cardiovascular Attributable Risk and Risk Factors Evaluations as a Matter of Statistics and Data Mining Confluences
No full textCardiovascular diseases represent a severe threat for humanity, being the first cause of death and hospitalization in both genders. An impressive number of studies have been developed in order to identify a set of factors causing this kind of illness, but only few of them were able to pay significant resources in analyzing large population samples (tens of thousands) and for longer periods of time (decades). This paper’s objective is to continue the previous researches of the eProCord project and to validate with concrete data the theoretical model developed for the attributable risk (AR). It will consider the same risk factors for myocardial infarction identified by INTERHEART study and the same work hypothesis. We will also evaluate if a certain value of the AR is also confirmed by the invoked disease of the patient. Using statistical and data mining tools we will investigate the prediction potential of the chosen factors and the opportunity to extend them in order to capture any cardiovascular disease. The empirical tests rely for now on a sample of 236 patients.Cardiovascular Disease, Myocardial Infarction, Attributable Risk, Roc, Data Mining, Classification
Microstructural differences between naturally-deposited and laboratory beach sands
No full text© The Author(s), 2022. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Ferrick, A., Wright, V., Manga, M., & Sitar, N. Microstructural differences between naturally-deposited and laboratory beach sands. Granular Matter, 24(1), (2022): 9, https://doi.org/10.1007/s10035-021-01169-4.The orientation of, and contacts between, grains of sand reflect the processes that deposit the sands. Grain orientation and contact geometry also influence mechanical properties. Quantifying and understanding sand microstructure thus provide an opportunity to understand depositional processes better and connect microstructure and macroscopic properties. Using x-ray computed microtomography, we compare the microstructure of naturally-deposited beach sands and laboratory sands created by air pluviation in which samples are formed by raining sand grains into a container. We find that naturally-deposited sands have a narrower distribution of coordination number (i.e., the number of grains in contact) and a broader distribution of grain orientations than pluviated sands. The naturally-deposited sand grains orient inclined to the horizontal, and the pluviated sand grains orient horizontally. We explain the microstructural differences between the two different depositional methods by flowing water at beaches that re-positions and reorients grains initially deposited in unstable grain configurations.MM is supported by National Science Foundation (No. 1615203). NS is supported by National Science Foundation (No. CMMI-1853056)
Recommended from our members
Numerical Modeling of Soil Fabric of Naturally Deposited Sand
No full textThis dissertation provides a systematical investigation of computational approaches to mod- eling of granular materials. Granular materials are ubiquitous in everyday life and in a variety of engineering and industrial applications. Despite the apparent simplicity of the laws governing particle scale interactions, predicting the continuum mechanical response of granular materials still poses extraordinary challenges. This is largely due to the complex his- tory dependence resulting from continuous rearrangement of the microstructure of granular material, as well as the mechanical interlocking due to grain morphology and surface rough- ness. X-Ray Computed Tomography (XRCT) is used to characterize the grain morphology and the fabric of the granular media, naturally deposited sand in this study. The Level-Set based Discrete Element Method (LS-DEM) is then used to bridge the granular behavior gap between the micro and macro scale. The LS-DEM establishes a one-to-one correspondence between granular objects and numerical avatars and captures the details of grain morphology and surface roughness. However, the high fidelity representation significantly increases the demands on computational resources. Herein, we introduce an enhanced image processing workflow for XRCT images in order to optimize the grain and fabric resolution. A parallel version of LS-DEM is then introduced to significantly decrease the computational demands. The code employs a binning algorithm, which reduced the search complexity of contact de- tection from O(n2) to O(n), and a do- main decomposition strategy is used to elicit parallel computing in a memory- and communication- efficient manner. The parallel implementation shows good scalability and efficiency.High fidelity LS avatars obtained from XRCT images of naturally deposited sand are then used to replicate the results of triaxial tests using the new parallel LS-DEM. Both micro- and macro-mechanical behaviors of natural materials were well captured and validated with experimental data. The results of the numerical modeling show that the primary source of peak strength of sand is the mechanical interlocking between irregularly shaped grains. Flexible membrane simulations with a rotatable loading platen were found to accurately match experimentally observed relationships between deviatoric stress and mobilized friction angle with axial shortening for naturally deposited sand. Finally, we investigated the viability of modeling dynamic problems with newly formulated impulse-based LS-DEM. The new formulation is stable, fast and energy conservative, however, it may be numerically stiff when the assembly has a substantial mass difference or badly reconstructed particles as a result of poor image resolution. We also demonstrated the feasibility of modeling deformable structures in the rigid body framework and proposed several enhancements to improve the convergence of collision resolution, including a hybrid time integration scheme to separately handle at rest contact and dynamic collision. We also extended the impulse-based LS-DEM to include arbitrarily shaped topography surfaces and exploited algorithmic advantages to investigate interactions between topography and colliding objects. The novel formulation significantly improves performance and allows for larger timesteps, which is advantageous for observing the full development of physical phenomena such as rock avalanches
- …
