Failure Process Research Articles

Microscopic Discrete Element Study of Aggregate Size on Uniaxial Compression Failure Process of Recycled Aggregate Concrete

Microscopic Discrete Element Study of Aggregate Size on Uniaxial Compression Failure Process of Recycled Aggregate Concrete

Unraveling landslide failure mechanisms with seismic signal analysis for enhanced pre-survey understanding

Abstract. Seismic signals, with their remote and continuous monitoring advantages, have been instrumental in unveiling various landslide characteristics and have been widely applied in the past decades. However, a few studies have extended these results to provide geologists with pre-survey information, thus enhancing the understanding of the landslide process. In this research, we utilize the deep-seated Cilan landslide (CL) as a case study and employ a series of seismic analyses, including spectrogram analysis, single-force inversion, and geohazard location. These techniques enable us to determine the physical processes, sliding direction, mass amount estimation, and location of the deep-seated landslide. Through efficient discrete Fourier transforms for spectrograms, we identified three distinct events, with the first being the most substantial. Further analysis of spectrograms using a semi-log frequency axis generated by discrete Stockwell transform revealed that Event 1 consisted of four sliding failures occurring within 30 s with decreasing sliding mass. Subsequent Events 2 and 3 were minor toppling and rockfalls, respectively. Geohazard location further constrained the source location, indicating that Events 1 and 2 likely originated from the same slope. Subsequently, the sliding direction retrieved from single-force inversion and the volume estimation were determined to be 153.67° and 557 118 m3, respectively, for the CL. Geological survey data with drone analysis corroborated the above seismological findings, with the sliding direction and source volume estimated to be around 148° and 664 926 m3, respectively, closely aligning with the seismic results. Furthermore, the detailed dynamic process observed in the spectrogram of Event 1 suggested a possible failure mechanism of CL involving advancing, retrogressing, enlarging, or widening. By combining the above mechanism with geomorphological features identified during field surveys, such as the imbrication-like feature in the deposits and the gravitational slope deformation, with video from the event, we can infer the failure mechanism of retrogression of Event 1 after shear-off from the toe. Then, the widening activity was caused by the failure process for subsequent events, like Events 2 and 3. This case study underscores the significance of remote and adjacent seismic stations in offering seismological-based landslide characteristics and a time vision of the physical processes of landslides, thereby assisting geologists in landslide observation and deciphering landslide evolution.

Thermal conductivity of planar net-τ, planar net-τ-graphene, and planar net-τ-silicene heterostructure with a glance at the process of failure

Thermal conductivity of planar net-τ, planar net-τ-graphene, and planar net-τ-silicene heterostructure with a glance at the process of failure

Non-linear shear characteristics and wear behaviors of joints considering the factors of roughness, size effect, and joint strength

This study investigates the non-linear shear behaviors and failure mechanisms of rock-like materials with three-dimensional joint regarding various sample diameters (d), joint roughness coefficients (JRC), and joint wall strength ratios (SR). A series of cylindrical specimens were prepared and underwent direct shear tests. The peak shear stress (τmax) decreases by 13.09%–25.98% with an increasing d due to the intensified stress concentration resultant from a diminished contact area. A higher JRC increases τmax by 13.16%–50.70% due to enhanced interlocking effects. An increase in SR improves the matrix mechanical properties, resulting in a gentle growth in τmax by 7.30%–18.27%. The normal displacement (δv)–shear displacement (u) curves and failure morphologies of the joints indicate that, as d decreases or JRC and SR increase, the curves gradually move upward and the failure modes of the joints transfer from plastic shear flow to brittle shear failure. Furthermore, the finite element method simulation was introduced to analyze the mesoscopic wear characteristics of the joint surfaces. The results reveal that the process of joint failure can be categorized into three stages including wear, shearing, and further smoothing, and the failure degree on the joints exacerbates with a smaller d or larger JRC and SR. Additionally, an improved non-linear shear failure criterion considering the influences of size effect, SR, and JRC is developed based on the Barton's JRC-JCS (joint compressive strength) model, with the average error reduced significantly from 8.12% to 3.23%.

Failure and post-failure kinematic disaster processes of columnar rock masses based on 3D discontinuous deformation analysis

Failure and post-failure kinematic disaster processes of columnar rock masses based on 3D discontinuous deformation analysis

Research on the mechanism of multiphase pump pressurization failure process under stratified boundary conditions

The helical-axial multiphase pump, as a crucial power device in oil and gas extraction and transportation, has been extensively and profoundly researched. However, the effects of unconventional boundary behaviors on pump performance and internal flow mechanisms remain insufficiently understood, creating significant obstacles to the optimization design of the helical-axial multiphase pump. This study first confirms the existence of stratified inflow through visualization experiments, and then employs numerical simulations with stratified flow as the boundary condition for analyzing the helical-axial multiphase pump. The results indicate that stratified inflow has a markedly adverse impact on both pump head and efficiency; notably, at a gas volume fraction of 30%, the pump head decreases from 7.29 m to 1.67 m. The underlying mechanisms can be elucidated through changes in pressure distribution and velocity along the impeller streamlines. Stratified inflow causes the pressure curve to transition from a parabolic shape to an approximately linear configuration, leading to the presence of a cis-pressure gradient at the leading edge of the impeller, which results in unnecessary energy losses. Based on the impeller channel velocity distribution, it captures the presence of undesirable channel phenomena such as fluid roll-up and reflow in the low velocity region of the impeller. This research provides a detailed discussion of the overall impact of stratified inflow boundary behavior on pump performance, and the findings offer essential data for understanding failure mechanisms and optimizing the design of helical-axial multiphase pumps.

Meso-mechanical mechanism of ordered mica alignment on the progressive failure process of granite under different lateral stress directions

Meso-mechanical mechanism of ordered mica alignment on the progressive failure process of granite under different lateral stress directions

Simulating concrete cracking and failure under impact loading using a novel constitutive integration paradigm in non-ordinary state-based Peridynamics

Concrete cracking and failure under external loads are common in infrastructure, particularly under impact conditions where the variability of loads and the complexity of the cracking process present significant challenges. While the Bond-Based Peridynamic (BBPD) and Ordinary State-Based Peridynamic (OSBPD) models are widely used in concrete damage analysis due to their low computational cost, their simple constitutive laws limit their effectiveness in simulating concrete’s response to impact loading. To overcome this limitation, we propose a novel approach that integrates classical constitutive models into the Peridynamics (PD) framework. Specifically, we reformulate the Concrete Damage Plasticity Model 2 (CDPM2) within a non-ordinary state-based PD (NOSBPD) framework, resulting in the CDPM2-PD model. This model incorporates factors such as strain rate effects and strain hardening and introduces a bond damage criterion for both tensile and compressive damage. Through three numerical examples, the CDPM2-PD model demonstrates its ability to accurately capture the cracking and failure process of concrete under impact, showing strong agreement with experimental observations in areas such as failure mode transitions and crack patterns. These results validate the model’s effectiveness and offer a versatile method for integrating classical constitutive models into the NOSBPD framework for complex material analysis.

Anaerobic co-digestion of hydrothermal liquefaction of aqueous phase with municipal sludge and dewatering centrate.

For integrating hydrothermal liquefaction (HTL) of sludge treatment to municipal wastewater treatment plants, this study demonstrated the feasibility of thermophilic (55°C) anaerobic co-digestion of liquid product of HTL (HTL aqueous) with municipal sludge and its dewatering centrate. Seven semi-continuously fed digesters were operated for a total of 420 days. To obtain an optimal mixing ratio of the HTL aqueous with other co-substrates, a wide range of parameters were tested on influent and effluent of the digesters with 0.0%-43.3% of the chemical oxygen demand (COD) loading rate of the co-digesters contributed by HTL aqueous. HTL aqueous was generated from mixed sludge (20% total solids) at 350°C, 170bar, and 20min retention time. Thermophilic co-digesters with HTL aqueous contributing to 12.0%, 23.1%, and 43.3% of the total COD load were fully inhibited after 42, 29, and 15 days, respectively, while co-digesters with 1.21% and 2.74% of total COD contribution by HTL aqueous operated without any inhibition over 180 days. Biogas production in the co-digester with 4.89% COD contribution from HTL aqueous was also inhibited after 95 days of operation. This co-digester experienced a complete process failure for 42 days, followed by 218 days of partial (76%) steady inhibition before fully recovered. This indicates that thermophilic cultures can acclimatize to inhibitors in HTL aqueous to a certain extent. High levels of nitrogen heterocyclic compounds, such as pyridines and pyrazines, in HTL aqueous were determined to be the cause of inhibition in co-digesters fed with high volume of HTL aqueous. This study demonstrated the feasibility of valorizing HTL aqueous from mixed sludge in thermophilic co-digesters with a COD contribution as high as 4.89% from HTL aqueous.

Reliability Modeling and Analysis of Competing Failure Systems With Damage Evolution Effect

ABSTRACTIn practical industrial engineering, systems with dependent and competing failure modes, such as aerospace systems and civil engineering structures, are ubiquitous. These systems usually simultaneously experience two failure modes: gradual internal degradation and external shock. The ultimate failure of the system results from the competition between the soft failure processes and the hard failure processes. With the wide application of intelligent management and artificial intelligence systems, this paper particularly focuses on the damage evolution processes of a system with intelligent characteristics, such as the damage self‐healing processes. By combining the cumulative shock model with the shock model to create a mixed shock model, we analyze the evolution processes of internal performance degradation and external shock damage induced by the self‐healing mechanism. We propose a novel system reliability model with dependent and competing failure processes that has practical significance for improving the accuracy of competing failure systems reliability assessments. Finally, to verify the practicability and validity of the model, empirical studies were conducted using examples of the corrosion process and prestressed strength of concrete degradation of reinforcement concrete (RC) pillar pier of sea bridges with pre‐mixed self‐healing capsules.

P-268. Root Cause Analysis of Healthcare-Associated Infections: A Case Study Methodology Using Pareto Charts, Ishikawa Diagrams, and Machine Learning

Abstract Background This paper introduces a method for analyzing the root causes of healthcare-associated infections (HAIs), stressing the importance of a holistic approach that merges clinical and epidemiological data.Figure 1Pareto Chart with the Main Specific Secondary Factors for HAIs Diagnosed in a General Hospital, January to September 2023. Pareto Chart with the Main Specific Secondary Factors for HAIs Diagnosed in a General Hospital, January to September 2023. Methods Risk and causal factors for HAI were identified and categorized into primary and secondary groups. A review of case studies and literature identified 63 factors, which were then organized into four primary categories: surgical factors, invasive procedures, care process failures, and intrinsic patient characteristics. Each category included specific secondary factors; for instance, intrinsic patient characteristics encompassed 18 factors such as neurogenic bladder, diabetes mellitus, and obesity. Active infection surveillance involved recording these factors for each patient and correlating them to specific infections. The analysis utilized Pareto charts, Ishikawa diagrams, and decision trees to summarize root causes in a case series study. From Pareto, construct Ishikawa, global (HAI), and for each topography.Figure 2Ishikawa Diagram for HAIs Diagnosed in a General Hospital, January to September 2023. Ishikawa Diagram for HAIs Diagnosed in a General Hospital, January to September 2023. Results During the active surveillance of 386 healthcare-associated infections (HAIs) diagnosed in a general hospital from January to September 2023: tracheobronchitis and pneumonia (178), surgical site infection (74), urinary tract infection (56), primary bloodstream infection (29), gastrointestinal infection (21), and other infections (28). A total of 2,323 potential risk and causal factors were recorded. The number of factors associated with each infection varied, ranging from zero (indicating no factors were identified with the infection) to 18 factors identified in a single case. The primary factor that predominated was intrinsic patient factors (44%), followed by failures in care processes (27%), surgical factors (21%), and invasive procedures (8%). With the risk factor data recorded during active infection surveillance, it's feasible to automate case-by-case critical analysis, for example, through mail merges, integrating data in spreadsheets with texts in Word.Figure 3Decision Tree Based on Secondary Factors to Stratify the Type of HAI. Decision Tree Based on Secondary Factors to Stratify the Type of HAI. Conclusion Our analysis illustrates how integrating clinical and epidemiological data can pinpoint critical factors contributing to HAIs. In addition to case series analysis, recording factors during active surveillance automates critical case-by-case analysis.Figure 4Example of an automated critical case-by-case analysis of a ventilator-associated pneumonia. Example of an automated critical case-by-case analysis of a ventilator-associated pneumonia. Disclosures All Authors: No reported disclosures

Investigating Deformation and Failure Mechanisms of Discontinuous Anti-dip Bench Rock Slopes Through Shaking Table Tests and Numerical Simulations

Abstract Large-scale shaking table tests and numerical simulations were conducted to investigate the deformation and failure mechanisms of an anti-dip bench rock slope with discontinuities. The study introduces the Displacement Baseline Offset Ratio (DBOR) to characterize the instability and failure processes of slopes when they reach a plastic state under seismic excitations. It examines the peak ground displacement and earth pressure responses, as well as the cumulative damage processes of the slope model to provide insight into the deformation and failure mechanisms. The results show a significant displacement amplification effect at elevated points of the slope when subjected to seismic excitations. Furthermore, as the input frequency of the sine wave increases, the amplitude of the displacement response at the upper part of the slope accelerates. The widest bench divides the entire slope into smaller segments, hindering the deformation and failure across the benches and reducing stress transfer from the upper slope, thereby preventing stress concentration at the toe of the slope. The distribution of DBOR suggests that plastic deformation is more pronounced on the inner side of the bench than on the outer side, leading to earlier cracking on the inner side. A critical displacement threshold for seismic damage of each bench is established based on residual displacement responses and critical peak acceleration. These findings provide theoretical references for the risk assessment and seismic design of bench rock slopes.

Experimental Investigation of Burst Failure Mechanism Under Polyaxial Loading Conditions

Abstract Effective monitoring and early warning methods are crucial for enhancing safety and sustainability in deep resource extraction, which are particularly important for mitigating rock/coal burst failures. This study introduces a newly modified thick-walled hollow cylinder (TWHC) testing system for rock and coal burst at the laboratory scale. Fracture initiation and propagation, leading to bursting on the wall of a cylindrical opening in granite, bluestone and coal are characterised by real-time acoustic emission (AE) responses. In this study, a borescope was used synchronously to observe the dynamic failure processes of rock/coal bursts and to verify AE results. The internal fracture morphologies of granite, bluestone and coal specimens were acquired using X-ray micro-Computed Tomography (μCT). We analysed the intrinsic mechanism of strain energy evolution of bursting and found that the average energy consumed by the induced cracking and released kinetic energy during bursting is approximately ~ 8, 25 and 18% of the total absorbed strain energy of granite, bluestone and coal, respectively. We found the average mass of the ejected rock/coal fragments to be ~ 0.3–0.5 g, whilst the rock/coal ejection velocity ranged from 10.5 to 19.8 m/s for the hollow coal, bluestone and granite. The results also indicate that granite and bluestone have the highest potential for violent bursting failure.

The Random RFPA Method for Modelling Rock Failure

Abstract The random rock failure process analysis (RRFPA) method was developed in this research to characterize the material spatial variability and uncertainty in rock failure modelling. The random field theory (RFT) was integrated with the traditional rock failure process analysis (RFPA) to model rock heterogeneity. In this approach, the variation of rock properties is represented as a function of relative distance, such that the influence of material intrinsic correlation on its fracturing behaviour can be appropriately captured. To validate the theory, 300 RRFPA simulations were conducted to investigate the failure characteristics of rock samples under compressive loading. The results showed that by incorporating a spectrum of material properties, the numerical outcomes exhibited distinct upper and lower bounds of stress across all testing scenarios, closely aligning with the experimental relationships. The histograms for uniaxial compressive strength and elastic modulus showed that both properties followed normal distributions, with the average values of 10.099 MPa and 1.818 GPa, respectively. The corresponding coefficients of variation were 0.450 and 0.038. The localized failure tended to result in a more rapid release of acoustic emission energy, but generated smaller cumulative energy compared to the overall failure pattern. In general, the maximum relative error of the RRFPA model was only 0.66% for uniaxial compressive strength, elastic modulus, and critical axial strain.

Mechanical Properties and Energy Evolution Laws of Rocks Under Freeze–Thaw

In high-altitude mountainous areas, the phenomenon of rock frost damage under repeated freeze–thaw cycles are pronounced, with the deformation and failure processes of rock often accompanied by energy dissipation. To elucidate the energy evolution mechanism of rocks under freeze–thaw cycles, triaxial compression tests and numerical simulation tests were conducted under different freeze–thaw cycles. Results from indoor tests indicate that successive freeze–thaw cycles deteriorate the mechanical properties of rocks. Compared to conditions without freeze–thaw cycles, after 40 freeze–thaw cycles, the peak stress of the rock decreased by 42.8%, the elastic modulus decreased by 64%, and, with increasing confining pressure, the rate of decrease lessened, indicating that confining pressure can inhibit the decline in the mechanical properties of rocks. As the freeze–thaw cycles increase, the total absorption energy (TAE) of rocks gradually decreases. Meanwhile, with increasing confining pressure, the TAE, elastic strain energy (ESE) and dissipated energy (DE) of rocks all gradually increase. However, as the confining pressure increases, the TAE increases by 781%, the ESE increases by 449%, and the DE increases by 6381%. Numerical simulation results reveal that with an increase in the freeze–thaw cycles, shear failure phenomena gradually decrease while tensile failure phenomena gradually increase. During the compression process, the evolution of internal cracks in rocks demonstrates a trend of slow–steady–rapid development, with the number of cracks produced being positively correlated with the freeze–thaw cycles. The performance can provide valuable insights into the degradation mechanism of the mechanical properties of rocks and failure analysis in high-altitude mountainous areas.

Using monitoring and simulation to analyze the failure characteristics of multizone landslides controlled by faults: a case study

Slopes influenced by multiple faults are prone to large-scale landslides triggered by multi-regional failures. Understanding the failure process and sequence is essential for the sustainable development of mining operations. This paper presents a method combining InSAR monitoring and numerical simulation to analyze the failure processes of slopes affected by multiple faults. Using the 298–710 m bench in the central area of the eastern slope of the Nanfen open-pit mine as a case study, the multidimensional small baseline subset (MSBAS) technique of InSAR was employed to calculate the vertical and horizontal deformation time series in the study area, enabling an analysis of the deformation characteristics of multizone bedding sliding. Subsequently, a numerical simulation was performed to replicate the three-dimensional evolution of the multizone failure. The simulation results aligned well with field surveys and InSAR monitoring data. Furthermore, the failure sequence analysis identified critical trigger zones within the region. The findings demonstrate that the proposed method effectively identifies the critical areas and movement sequence of multi-regional failures. In this paper, the faults disrupted the connectivity between slopes, acting as the initial trigger for entire landslide. The first failure occurred in a critical area, creating space for further sliding in other regions and reducing lateral constraints in neighboring areas, eventually leading to significant deformations. Therefore, by using this method to identify potential critical areas before landslides occur, targeted mitigation measures can be implemented to reduce the risk of such events.

Deformation and Failure Mechanism and Control of Water-Rich Sandstone Roadways in the Huaibei Mining Area

The sandstone roof rock in the Huaibei mining area contains abundant water at depths of 2–3 m. Water–rock interactions in the rock-surrounding roadway can cause significant deformation, seriously threatening the safety of mine operations. Investigating the deformation and failure mechanisms of water-rich sandstone is therefore of critical importance. In this study, X-ray diffraction and scanning electron microscopy were used to analyze the composition and microstructure of water-rich sandstone. Based on the stress state during the roadway excavation, a true triaxial loading scheme with four different stress paths was designed to study the effects of different moisture contents and loading methods on the mechanical properties of the sandstone. The results show that the deviatoric stress decreased for all stress paths. Acoustic emission (AE) characteristics during the deformation and failure processes were also studied, which indicated that the AE b-value decreased, increased, and then decreased again corresponding to the primary compaction, elastic deformation, and plastic deformation evolutionary processes in the internal microstructure of the rock. The variation in the b-value reflected the development and expansion of internal fractures. These findings provide useful insights for controlling the stability of the surrounding rock in water-rich roadways in coal mines.

Study on the Effects of Microstructural Heterogeneity on the Mechanical Behavior and Failure Process of Brittle Rocks Based on DEM

Study on the Effects of Microstructural Heterogeneity on the Mechanical Behavior and Failure Process of Brittle Rocks Based on DEM

Quasi-static and dynamic compression behavior of stacked pyramidal lattice structures with I-beam struts

This study investigates the quasi-static and dynamic compression performance of a newly designed stacked pyramidal lattice (SPL) structure composed of struts that resemble I-beams. These novel lattice structures are 3D-printed considering three different stacking sequences, and their stiffness, strength, and energy absorption properties are experimentally assessed through low-velocity impact (1.54 m/s) and quasi-static compression tests. Additionally, dynamic finite element (FE) simulations are carried out to delve deeper into the collapse mechanisms and failure processes. The findings indicate that the SPLs with I-beam struts outperform conventional SPLs with square struts of same mass showcasing superior rigidity, durability, and energy absorption. Specifically, we report enhancements in strength and energy absorption of 26% and 109% under quasi-static compression and 34% and 74% under low-velocity impact, respectively. The latter enhancements are attributed to the improved transverse bending stiffness of the I-shaped cross-section, resulting in lateral (sideward) buckling of the lattice struts. Both experimental and numerical findings demonstrate that altering the stacking sequence of the SPL can lead to significant improvements in the dynamic compression performance, with enhancements of up to 84% in collapse strength.

Failure of the farm bill process in 2023—a perspective from social media activity

Abstract In September 2023, the current farm bill was allowed to expire. This marked the fourth consecutive farm bill to see its authorization lapse before replacement legislation was signed into law. The failure in 2023 is notable as significant trade and covid shocks revealed needed reforms in farm and food safety nets. We develop a unique online and social media dataset and metrics to examine 2023 online activity to understand drivers of online farm bill discussion and implications for the future of the traditional farm bill political coalition. These findings echo the increasing concern about future farm bills amid a broadening political divide.