Interlocking Of Particles Research Articles

Comparisons of weathered lateritic, granitic and volcanic soils: Compressibility and shear strength

Lateritic soil is rich in oxides of iron and aluminum (sesquioxide). The effects of these oxides on its mechanical behaviour are not well-understood. In this study, the compression and shear behaviour of a lateritic (LAT) soil was tested and compared to those of two other weathered granitic and volcanic soils (CDG and CDV) for the first time within the critical state framework. The mineralogy, chemical compositions and microstructure of these three soils were also measured by x-ray diffraction (XRD), x-ray fluorescence (XRF) and scanning electron microscopy (SEM) respectively. It is found that only LAT contains goethite, while other minerals are similar in all the soils. The content of iron and aluminum oxides in LAT is about 40% higher than that in CDV and CDG. LAT is found to be less compressible than CDV and CDG by 18% and 36% respectively, even though the former has a higher clay content than the latter two soils. The lowest compressibility of LAT is mainly attributed to its high content of sesquioxide, which induces the formation of more aggregates. The LAT has more intra-aggregate pores and hence less inter-aggregate pores than CDV and CDG. A smaller volume of inter-aggregate pores of LAT results in a lower compressibility. It is found that the critical state friction angles of LAT, CDV and CDG are 42°, 33° and 38°, respectively. The highest friction angle of LAT is likely attributed to the content of large particles and presence of goethite. Due to the high sesquioxide contents of LAT, many clay fines also form large aggregates leading to a more granular microstructure. Consequently, the number of particle contacts is increased and therefore enhancing particle interlocking. Goethite mineral found in LAT could enhance inter-aggregate interlocking through its contiguous singly coordinated OH groups.

Numerical and Experimental Investigation on Bonding Behavior of Cold Sprayed Porous WC-17Co Particles onto Different Substrates

Cold sprayed WC-Co metal matrix composite coatings have shown great potential in wear-resistance applications. This work aims to use experimental and numerical methods to clarify the deposition and particle–substrate bonding behavior of a single porous WC-17Co particle onto various substrates. To achieve this objective, porous WC-17Co particles were used as the feedstock; soft Al 2024 (Al alloy) and hard stainless steel 316 (SS) were used as the substrates. The experimental results revealed that brittle WC-Co particles tended to remain intact after depositing on a soft Al alloy substrate, but underwent serious fracture when impacting on a hard SS substrate. Further results indicated that the high energy dissipation and the consequent high stress concentration in the WC-Co particle was the main reason for inducing the particle fracture. In addition, two different mechanical interlocking mechanisms were identified during the WC-Co particle deposition process (namely WC reinforcement interlock and WC-Co particle interlock), dominating the particle-substrate bonding. A soft Al alloy substrate resulted in better interlocking than a hard SS substrate, thereby the corresponding particle bonding ratio was also much higher.

Discrete element model study into effects of particle shape on backfill response to cyclic loading behind an integral bridge abutment

The discrete element method, implemented in a modular GPU based framework that supports polyhedral shaped particles (Blaze-DEM), was used to investigate effects of particle shape on backfill response behind integral bridge abutments during temperature-induced displacement cycles. The rate and magnitude of horizontal stress build-up were found to be strongly related to particle sphericity. The stress build-up in particles of high sphericity was gradual and related to densification extending relatively far from the abutment. With increasing angularities, densification was localised near the abutment, but larger and more rapid stress build-up occurred, supported by particle reorientation and interlock developing further away.

Earthquake response of a multiblock nuclear reactor graphite core: Experimental model vs simulations

SummaryThe complex dynamics of a quarter‐scale model of a graphite nuclear reactor core, representative of the second generation of British advanced gas‐cooled nuclear reactors, is investigated numerically and experimentally. Advanced gas‐cooled nuclear reactor cores are polygonal, multilayer, arrays of graphite bricks, with each brick allowed to rock by design relative to each other in accordance with the boundary conditions. A 35 000 DOF, nonlinear finite element model of the core created by Atkins Nuclear, was analysed on a high performance computing facility at the University of Bristol, and a corresponding 8 t physical model, equipped with 3200 data acquisition channels, was built and tested on the University of Bristol 6‐DOF shaking table. In this paper, the two models are subjected to a series of (1) synthetic earthquake and (2) idealised harmonic input motions. The experimental data are used to compare and verify the two models and explore the dynamics of the core. A kinematic model of the response is also developed based solely on geometric constraints. The results are presented in the form of response maps and graphs. Important conclusions are drawn as to the dynamics and earthquake response of such systems, which inform numerical model validation. It is found that contrary to the case of a small number of rocking blocks that exhibit highly complex response patterns, the behaviour of the model at hand is both smooth and repeatable. An analogy between the response of the core and that of dense granular matter exhibiting particle interlocking and dilatancy is highlighted.

DEM-aided direct shear testing of granular sands incorporating realistic particle shape

Discrete element method (DEM) of granular sands incorporating the effect of the realistic particle shape has been an important issue for many years. In this context, this study proposed a novel framework for the generation of realistic-shaped particles of natural sands in 3D DEM simulations. The generation framework mainly included micro-CT (μCT) scanning of sand particles, image processing of μCT images, spherical harmonic reconstruction of the particle surface, and clump generation by the overlapping multisphere clump method (OMCM) in DEM simulations. To validate the accuracy of OMCM, the volume and inertia moment of the clump were carefully investigated, and a set of optimized generation parameters was then determined to ensure the accuracy of the clump and the limit number of the filling spheres. Based on the generation framework, a clump sample with realistic particle shapes and a corresponding sphere sample were generated to conduct a series of direct shear testing. The simulation results demonstrated that the realistic particle shape highly increases the particle interlocking rather than the anisotropic intensity of strong contact force chains, and in turn enhances the shear resistance and the shear-induced dilation of the sands. It was also found that the inter-particle contacts of the clump sample have higher friction mobilization than that of the sphere sample, which identified the micromechanism of the shape effect on the particle interlocking.

Influence of water content and shear rate on the mechanical behavior of soil-rock mixtures

Soil-rock mixtures (S-RMs) are widely distributed in the nature. The mesoscopic deformation and failure mechanisms as well as the macro-mechanical behaviors of the S-RMs depend largely upon the rate of deformation, water content and particle sizes. In this research, a series of large-scale direct shear tests with different water contents and different grain-size distributions were conducted to study the influence of the aforementioned factors on the mechanical properties of the S-RMs. Due to the effect of the rock blocks’ breakage in the S-RMs, the relationship between the shear strength and the vertical stress of S-RM follows a power law instead of a linear one. It is found that there exists a threshold value for the vertical stress during the shearing process, below which the soil strength is mainly determined by the inter-locking of particles and the re-arrangement of meso-structure, and otherwise large-sized rock blocks are gradually broken into smaller fragments, resulting in a decrease in the soil strength. The shear rate can also significantly influence the degree of particle breakage and the meso-structural rearrangement of the S-RMs, namely, under low shear rate, the particles of the samples are fully broken resulting in enhanced macro-strength. As a result, the lower the shear rate, the higher the macroscopic strength. So under unsaturated conditions, the water content will affect the strength of the S-RMs by reducing the strength of rock blocks. As the water content increases, the soil strength decreases gradually, and assumes a moderate value when the water content reaches 8%. At the same water content, the soil strength increases with the sizes of large rock blocks. For the occlusion, breakage and structure re-arrangement of the oversized rock blocks inside S-RM, which have a huge influence on the mechanical characteristics of the samples.

Micromechanical analysis on the compaction of tetrahedral particles

Understanding the roles of particle properties in powder compaction is important to many industrial products, such as tablets in pharmaceutics, briquettes in iron ore handling and green compacts in powder metallurgy. However, the role of particle shape in bulk compression and how it is related to the properties of the final compact are not well understood. In this study, we investigated the structural evolution, force distribution and compact strength of tetrahedral particles using discrete element method, with a focus on the effect of particle interlocking due to non-spherical particle shape. Tetrahedral particles were constructed using clumped sphere approach, which allows multiple contacts being set up between two contacted particles. Die compaction followed by unconfined compression were conducted on the assemblies of both spherical and tetrahedral particles. The results showed that the tetrahedral particle shape reduces the degree of particle rearrangement at the early stage of bulk compression but enhances the resistance to bulk deformation at the later stage due to enhanced shear resistance at interparticle contacts. The compact of tetrahedral particles presents a higher compressive strength due to increased number of interparticle bonding. Compared to the spherical particles, the macroscopic failure mode tends to be more ductile for the tetrahedral particles. The tetrahedral particle shape has no effect on the dominant bond failure mode but leads to a wider shear banding, more dispersed bond breakage and a slower bond breakage process. This work highlights the role of particle shape in densification mechanism and mechanical response of the formed powder compact.

Free Swelling and Modulus of Elasticity of Compacted Black Cotton Soil Treated with Reclaimed Asphalt Pavement

Black Cotton Soil (BCS), collected from Numan, in north-eastern region of Nigeria was stabilized with Reclaimed Asphalt Pavement (RAP), collected from failed road surface, along Minna-Bida road in Niger state Nigeria. The BCS was replaced with RAP at 0%, 10%, 20%, to 100% by weight of the soil. X-ray diffraction test on the BCS revealed predominantly, presence of quartz, microcline, albite and kaolinite, while that of RAP shows quartz, albite, orthoclase, phylogopite and actinolite. Maximum Dry Density (MDD) of the mixtures increased from 1890kg/m 3 at 0% RAP content to maximum value of 2036kg/m 3 at 30% RAP, after which the value reduced to 1925kg/m 3 at 100% RAP. Scanning Electron Microscopy showed fewer cracks in mixture with 20 and 30% RAP contents, rather an interlocking of particles of different sizes in a very dense state was revealed. Unconfined Compressive Strength (UCS) increased from 392kN/m 2 at 0% RAP to 947kN/m 2 at 30% RAP content, representing 58.6% increase. The values, thereafter, reduced to 17.5kN/m 2 at 100% RAP content. Modulus of Elasticity increased from 10.4Mpa at 0% RAP to 42.5MPa at 30% RAP, representing 75.5% increase. The values, thereafter, reduced to 2.9MPa at 100% RAP content. The swelling potential of the mixtures reduced from medium at 0% RAP content to low at 30% RAP content.

Effect of Stress Direction on the Undrained Monotonic and Cyclic Behaviour of Dense Sands

Geotechnical design may be unsafe if the anisotropic behaviour of soil is not considered. The behaviour of anisotropic materials depends on the principal stresses and their directions. A detailed experimental programme was conducted to study the effect of stress direction on the monotonic and cyclic behaviour of dense sand. A total of 20 undrained tests were performed at a constant mean confining stress (σ'0m) constant intermediate principal stress ratio (b= (σ2-σ3)/(σ1-σ3)), and principal stress directions (α). Two fine sands, Babolsar and Toyoura, were selected as the test materials. The isotropic consolidated specimens were prepared using the wet tamping technique. The results showed that the major principal stress direction had little considerable effect on the mobilized friction angle at steady state or phase transformation. The results showed that stress direction had a significant effect on the non-coaxiality between the principal strain increment direction and the principal stress direction. The soil fabric was led to significant non-coaxiality value before the peak shear strength. Increasing the octahedral shear strains decreased the non-coaxiality value due to destruction of the soil particle interlock (soil fabric). The effect of stress direction on non-coaxiality and excess pore water pressure generation was also investigated.

Micro-structure and motion of two-dimensional dense short spherocylinder liquids

We numerically investigate the micro-structure and motion of 2D liquids composed of dense short spherocylinders, by reducing the shape aspect ratio from 3. It is found that reducing shape aspect ratio from 3 causes a smooth transition from heterogeneous structures composed of crystalline ordered domains with good tetratic alignment order to those with good hexagonal bond-orientational order at an aspect ratio equaling 1.35. In the intermediate regime, both structural orders are strongly deteriorated, and the translational hopping rate reaches a maximum due to the poor particle interlocking of the disordered structure. Shortening rod length allows easier rotation, induces monotonic increase of rotational hopping rates, and resumes the separation of rotational and translational hopping time scales at the small aspect ratio end, after the crossover of their rates in the intermediate regime. At the large shape aspect ratio end, the poor local tetratic order has the same positive effects on facilitating local rotational and translational hopping. In contrast, at the small shape aspect ratio end, the poor local bond orientational order has the opposite effects on facilitating local rotational and translational hopping.

Steric Stabilization of γ-Fe2O3 Superparamagnetic Nanoparticles in a Hydrophobic Ionic Liquid and the Magnetorheological Behavior of the Ferrofluid

Hydrophobic ionic liquid ferrofluids (ILFFs) are studied for use in electrospray thrusters for microsatellite propulsion under nonatmospheric and in high-temperature environments. We synthesized a hydrophobic ILFF by dispersing sterically stabilized γ-Fe2O3 nanoparticles (NPs) in the ionic liquid 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide. A diblock copolymer, C4-RAFT-AA10-DEAm60, was synthesized to facilitate multipoint bidentate anchoring to the NP through the acrylic acid block. The DEAm60 layer was incorporated to generate steric repulsion between particles to protect against the aggregation of magnetized particles arising from dipole-dipole attraction. The effect of shearing and variation in the magnetic field strength on the steric repulsion was examined using the DLVO theory. The effect of varying the magnetic field strength and particle concentration on the viscoelastic properties of the ferrofluid was evaluated using rheometry. The viscosity of the ferrofluid increased with the magnetic field strength, indicating that the magnetized particles assembled into a structure. The level of straining required to break down the structure formed by the magnetized particles increased with the magnetic field strength and particle concentration. The absence of particle interlocking during shearing was indicated by the smooth viscosity versus shear rate traces. The DLVO analysis showed that increasing the magnetic attraction between the particles causes the DEAm60 brush layers on the particles to overlap more, resulting in an increase in the steric repulsion. As overlapping increases, osmotic repulsion is caused before progressing to a strong elastic repulsion. The effect of the polymer solubility and particle interaction due to hydrodynamic forces on the steric repulsion was also analyzed.

Codensification of Agroforestry Residue with Bio-Oil for Improved Fuel Pellets

Codensification of agroforestry residue with bio-oil can improve the pellet quality with reduced energy consumption and expand the utilization of bio-oil. This study comprehensively evaluates the effect of bio-oil addition on the storage, transportation, and combustion characteristics of the pellets. The results confirm that under a low pressure of 63.69 MPa bio-oils are more efficient in improving the pellet durability than selected solid additives due to the high viscosity which generated strong adhesion force during densification and enabled stronger particle interlocking of the feedstock. In addition, the hydrophobicity of the apple tree branches pyrolysis oil (APO) added pellets were enhanced, due to the introduction of hydrophobic groups and the improvements in the surface morphology. Besides, APO improved the energy density and fuel characteristics of the pellets via the change of chemical compositions. Above all, addition of the APO additive enhanced the quality of the fuel pellets. Moreover, by a...

IN-VITRO BIOCOMPATIBILITY STUDY OF HYDROXYAPATITE COATED ON CO-CR-MO WITH OXIDE INTERLAYER

The effects of oxide interlayer on cobalt-chromium-molybdenum substrate were investigated in order to improve the quality of hydroxyapatite (HA) coating as well as enhance the cell responses. Substrates were oxidized at temperature of 850 °C and 1050 °C for 3 hours. Oxidized substrates were then coated with HA slurry using dip coating technique. Analysis of surface morphology, thickness and chemical composition of oxide interlayer prior to HA coating were performed using field-emission scanning electron microscopy, energy dispersive X-ray spectroscopy and grazing X-ray diffraction respectively. It seems that rough surface of oxide interlayer provides better mechanical interlocking of HA particles to the substrate surface with no visible micro-cracks. In addition, the HA coated substrates with oxide interlayer also demonstrate strong attachment and better proliferation of cells compared to HA coated substrates without oxide interlayer. The results also demonstrates that cells were spread out more actively as earlier as day 7 and have greater extensions of filopodium on HA coated substrates with oxide interlayer. It is concluded that the introduction of an intermediate oxide layer on Co-Cr-Mo substrate prior to HA coating has shown a positive effect in terms of improving the quality of HA coating as well as cell bioactivity performance.

Aging simulation of the tailings from Stava fluorite extraction by exposure to gamma rays

Abstract Tailings storage facilities are disposal systems for storing the waste products of the mining industry consisting of a slurry mixture made of soil, rock and water that remain after the mineral values have been removed from the patent ore. Tailings dams are supposed to last forever, so after their deposition, tailings can experience aging processes with physical and chemical changes depending on the interactions between local conditions and source mineralogy. The consequences of these aging processes are increased interlocking of particles and oxidation processes, sometimes making previously safely held contaminants available and mobile. Among the long-term aging processes, the natural ionizing radiation (from radioactive isotopes of the soils, cosmic rays, and also ultraviolet rays from the sun) can be considered, as proposed in the current research. Furthermore, in many countries, tailings are beginning to be re-used as backfill, landscaping material or feedstock for cement and concrete. So if any, the long-term physical and chemical modifications could affect the hydraulic and mechanical behaviour of tailings with relevant economic consequences. For these reasons, wet and dry silty samples of tailings spilled out after the failure of the Stava tailings dam (Trentino Alto Adige, Italy) were exposed to gamma rays, as an accelerated aging technique to simulate the natural ionizing radiation, and then characterized. The modifications on physical and chemical properties were observed and, despite certain chemical stability, some physical changes were observed, particularly in terms of size particle distribution, inner porosity of the particles and specific surface.

Comparative study of coral sand and silica sand in creep under general stress states

Coral sand has individual characteristics that differ from silica sand, such as creep behavior that is always attributed to particle crushing under high stress states. To understand the creep behavior of coral sand under general stress levels, three series of comparative triaxial tests relevant to the deviator stress, confining pressure, and relative density were performed on coral sand and silica sand creeping for more than 5 days. The volumetric, axial, and shear creeps of coral sand are considerably larger than those of silica sand, particularly under a relatively high confining pressure. The volumetric creep strain of coral sand was found to be contractive, but that of silica sand appeared dilative according to the creep time. This difference is not mainly governed by particle crushing in coral sand because the grain-size distribution prior to and after creep is similar. The grain skeletons were observed using a scanning electron microscope, finding that, independent of the grain size and shape, the coral grains include large amounts of cavities. The creep of coral sand under general stress conditions is mainly caused by particle interlocking, i.e., the angular regions of some particles interlock into the cavities of other particles due to particle rotation. This structuration is induced by breakage of asperities and voids during creep such as the local instability near cavities.

Effect of Particle Size and Cohesion on Powder Yielding and Flow

The bulk properties of powders depend on material characteristics and size of the primary particles. During storage and transportation processes in the powder processing industry, the material undergoes various modes of deformation and stress conditions, e.g., due to compression or shear. In many applications, it is important to know when powders are yielding, i.e. when they start to flow under shear; in other cases it is necessary to know how much stress is needed to keep them flowing. The measurement of powder yield and flow properties is still a challenge and will be addressed in this study. In the framework of the collaborative project T-MAPPP, a large set of shear experiments using different shear devices, namely the Jenike shear tester, the ELE direct shear tester, the Schulze ring shear tester and the FT4 powder rheometer, have been carried out on eight chemically-identical limestone powders of different particle sizes in a wide range of confining stresses. These experiments serve two goals: i) to test the reproducibility/consistency among different shear devices and testing protocols; ii) to relate the bulk behaviour to microscopic particle properties, focusing on the effect of particle size and thus inter-particle cohesion. The experiments show high repeatability for all shear devices, though some of them show more fluctuations than others. All devices provide consistent results, where the FT4 powder rheometer gives lower yield/steady state stress values, due to a different pre-shearing protocol. As expected, the bulk cohesion decreases with increasing particle size (up to 150 μm), due to the decrease of inter-particle cohesion. The bulk friction, characterized in different ways, is following a similar decreasing trend, whereas the bulk density increases with particle size in this range. Interestingly, for samples with particle sizes larger than 150 μm, the bulk cohesion increases slightly, while the bulk friction increases considerably—presumably due to particle interlocking effects—up to magnitudes comparable to those of the finest powders. Furthermore, removing the fines from the coarse powder samples reduces the bulk cohesion and bulk density, but has a negligible effect on the bulk friction. In addition to providing useful insights into the role of microscopically attractive, van der Waals, gravitational and/or compressive forces for the macroscopic bulk powder flow behaviour, the experimental data provide a robust database of cohesive and frictional fine powders for industrially relevant designs such as silos, as well as for calibration and validation of models and computer simulations.

Performance of ground improvement projects incorporating sustainable reuse of geo-composite wastes

Abstract Green geotechnical construction can have a significant contribution to the sustainability and resilience of infrastructural projects. As the amounts of wastes produced from different construction and mining activities continues to increase exponentially, green geotechnical applications incorporating waste and recycled materials become essential to minimize materials sent to landfill while reducing demand on natural resources. This paper investigates the use of geo-composite admixture produced from recycled materials in ground improvement projects. The developed geo-composite admixture is comprised of coal ash, blast furnace slag, and recycled bassanite to optimize the formation of ettringite within the soil matrix. The geo-composite admixture was mixed with small ratios of cement-soil to retain its stability in wet environment. The effect of geo-composite on the strength of stabilized soil is evaluated through unconfined compressive strength tests. The results demonstrated the effectiveness of the developed geo-composite admixture in stabilizing soft clay soils. As the admixture ratio increased, the soil mixture strength and dry unit weight increased while its water content decreased. The formation of ettringite enhanced as the admixture ratio in soil mixtures increased. The ettringite plays an important role in the permanent strength improvement of stabilized soil. Increasing the morphology of ettringite in soil matrix due to increased length of ettringite needles, which enhances interlocking of soil particles and consequently improves strength of soil mixture. Based on the achieved results, it is recommended to incorporate the developed geo-composite admixture in earthwork structures for more sustainable and resilient construction.

Effects of particle asphericity on the macro- and micro-mechanical behaviors of granular assemblies

Particle shape has been regarded as a key factor affecting mechanical behaviors of granular assemblies. The present work proposes a shape descriptor, i.e., asphericity, to isolate the effect of aspect ratio and angularity. A series of numerical triaxial compression tests are conducted on mono-disperse assemblies with different asphericities using a superball-based discrete element model. The corresponding mechanical behaviors are investigated from both macroscopic and microscopic points of view. Effects of particle asphericity are examined as well. It demonstrates that particle asphericity is able to enhance the particle–particle inter-locking with higher locked-in forces, showing an increasing proportion of sliding contacts, thereby making a granular assembly stiffer and stronger. In addition, weak contacts have a dominant proportion in the overall contact networks, positively correlated with asphericity. However, asphericity has an insignificant effect on the mean coordination number at the critical state. Furthermore, an established analytical stress–force–fabric relationship is verified using the present data. Anisotropy within an assembly is quantified in terms of several measures, i.e., contact normals, normal and tangential branch vectors, and normal and tangential contact forces. It is found that anisotropy of granular fabric is strongly determined by anisotropy sources in strong contact networks, where a larger asphericity results in a more anisotropic granular fabric.

Computational thermo-hydro-mechanics for multiphase freezing and thawing porous media in the finite deformation range

A stabilized thermo-hydro-mechanical (THM) finite element model is introduced to investigate the freeze–thaw action of frozen porous media in the finite deformation range. By applying the mixture theory, frozen soil is idealized as a composite consisting of three phases, i.e., solid grain, unfrozen water and ice crystal. A generalized hardening rule at finite strain is adopted to replicate how the elasto-plastic responses and critical state evolve under the influence of phase transitions and heat transfer. The enhanced particle interlocking and ice strengthening during the freezing processes and the thawing-induced consolidation at the geometrical nonlinear regimes are both replicated in numerical examples. The numerical issues due to lack of two-fold inf–sup condition and ill-conditioning of the system of equations are addressed. Numerical examples for engineering applications at cold region are analyzed via the proposed model to predict the impacts of changing climate on infrastructure at cold regions.

Influence of diatom microfossils on sediment shear strength and slope stability

AbstractDiatom microfossils have been detected in many natural marine sediment deposits around the globe and are held responsible for the disobedience to well‐established geotechnical relationships between index‐properties and shear strength. We revisit the static shear strength and present the first cyclic undrained shear strength experiments on diatom microfossil—clayey‐silt mixtures to study the role of diatoms on submarine slope stability. It is attested that the angle of internal friction (Φ) increases with diatom content, however, we provide evidence for a significant overestimation of Φ in previous studies. Based on direct shear tests at varying normal stresses ≤ 600 kPa we find Φ = 32° in contrast to 43° in pure diatom. Similarly, to static shear strength, cyclic shear strength increases with diatom content, however, in contrast to static shear strength the most drastic increase does not occur from 0% to 25% diatoms but from 75% to 100%. Interestingly, diatomaceous sediments tend to fail by liquefaction although well‐established relations between index properties and liquefaction susceptibility predict the opposite. Liquefaction failure is observed solely in samples containing ≥ 50% diatoms whereas samples with lower diatom content fail by cyclic softening. We conclude diatom microfossils in marine sediments significantly contribute to an increased slope stability under static and cyclic loading conditions since diatoms lead to higher resistance independently of the loading mode. The strength increase is interpreted as a result of particle interlocking and surface roughness, which is very efficient given the highly variable habitus of diatom species.