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The experimental and numerical studies of carbon composite sandwich panels with stiffened polyurethane (PU) foam core were carried out. A novel concept of stiffening the panels by co-bonding to skin was introduced. The stiffening of PU core was conceptualized using carbon composite by wrapping and skin/facesheet was co-bonded. Four different sandwich panel configurations such as plain, longitudinal stiffening, transverse stiffening, and stiffening in both directions were manufactured. To explore the suitability of this novel concept for structural applications, the bending behavior of panels were investigated under three-point bend tests. A three-dimensional finite element model incorporating stiffness degradation concept was developed in ANSYS to understand the fundamental behavior of configured panels. Experimental and numerical results showed failure patterns like shear in foam core, indentation in composite skin and bulge/lift-off of outer composite stiffener. Comparative study of results showed that oriented stiffened sandwich panels have superior mechanical characteristics with 75% increase in the load-bearing capacity and 29% reduction in displacement. The failure patterns were envisaged through microscopy and computer-based tomography techniques. [ABSTRACT FROM AUTHOR]

Research on the deformation characteristics and failure modes of buried pipelines under local suspension conditions caused by groundwater loss in coal mining subsidence areas is conducive to grasping the failure evolution law of pipelines and providing technical support for the precise maintenance of gathering and transportation projects and the coordinated mining of gas and coal resources. First, a test system for monitoring the deformation of pipelines under loading was designed, which mainly includes pipeline load application devices, end fixing and stress monitoring devices, pipeline end brackets, and stress–strain monitoring devices. Then, a typical geological hazard faced by oil and gas pipelines in the gas–coal overlap area—local suspension—was used as the engineering background to simulate the field conditions of a 48 mm diameter gas pipeline with a localized uniform load. At the same time, deformation, top–bottom strain, end forces, and damage patterns of the pipeline were monitored and analyzed. The results show that the strain at the top and bottom of the pipeline increased as the load increased. In this case, the top was under pressure, and the bottom was under tension, and the conditions at the top and bottom were opposite.. For the same load, the strain tended to increase gradually from the end to the middle of the pipeline, and at the top, it increased significantly more than at the bottom. The tensile force carried by the end of the pipeline increased as the applied load increased, and the two were positively correlated by a quadratic function. The overall deformation of the pipeline evolved from a flat-bottom shape to a funnel and then to a triangular shape as the uniform load increased. In addition, plastic damage occurred when the pipeline deformed into a triangular shape. The results of the investigation clarify for the first time the mathematical relationship between local loads and ultimate forces on pipelines and analyze the evolution of pipeline failure, providing a reference for pipeline field maintenance. Based on this, the maximum deformation of and the most vulnerable position in natural gas pipelines passing through a mining subsidence area can be preliminarily judged, and then the corresponding remedial and protection measures can be taken, which has a certain guiding role for the protection of natural gas pipelines. [ABSTRACT FROM AUTHOR]

Anisotropic behaviors of layered rocks, characterized by the distinct mechanical responses to varying loading directions, have been widely studied in laboratory tests. However, understanding the microscale failure mechanisms of beddings and rock matrices is still challenging in laboratory scale. In this study, we present a numerical modeling based on PFC3D to investigate the mechanical responses of slates with five bedding angles (0°, 30°, 45°, 60°, 90°) under differential cyclic loading (DCL). The beddings and matrices are modeled using the same contact model to ensure the comparability of parameters, with the weakened parameters of beddings reasonably determined through X-ray diffraction (XRD). The damage evolution paths are characterized by the degradation of the bond diameter. The simulation results replicate realistic stress–strain curves documented in laboratory tests. We develop an acoustic emission (AE) algorithm for respectively monitoring the AE events occurring in beddings and matrices. Additionally, the release of the bond energy is captured to determine the b-values in simulation, and experimental data are used to validate its rationality. Finally, the macroscopic failure patterns obtained from numerical simulations are compared to the failed samples in laboratory test and the nuclear magnetic resonance (NMR) results, demonstrating a consistent correlation and verifying the validity of the proposed model. Highlights: The force chain evolution for different bedding angles was analyzed under differential cyclic loading. A dual system for monitoring AE events in beddings and rock matrices was created based on the 3D particle model. The method of calculating numerical b-value was given based on the released energy at bond failure. [ABSTRACT FROM AUTHOR]

This investigation focuses mainly on the failure behaviour and performance of angle and channel shear connectors in composite structures made with steel and brick aggregate concrete. It was observed that both angle and channel shear connectors did not fail themselves. However, in some specimens, localised connector yielding was observed in channel shear connectors. In both cases, concrete strata failed as either concrete crushing and shearing, combined splitting and bending, or complete splitting mode of failure. Crushing and shearing failure was noticed in specimens having smaller web and flange and were brittle in nature as compared to the failure of specimens with larger web and flange. Other parameters, such as shear resistance, energy absorption, and load-slip behaviour, were also investigated. Web height and flange width of both connectors significantly affected the ultimate shear capacity and slip of the brick aggregate concrete specimen. Channel connectors were found more flexible and carried more shear than angle connectors. Channel connectors had an average of 32.41% and 116.17% more ultimate load and slip capacity than the angle connectors in brick aggregate concrete, respectively. The load-carrying capacity, slip, and failure behaviour of the brick aggregate concrete were found similar to those of stone aggregate concrete. [ABSTRACT FROM AUTHOR]

The fracture (pore) development of coal specimen under axial stress loading and hydraulic permeability affects directly the mechanical indexes and the permeability characteristics. In this paper, using theoretical analysis and mechanical test methods, the relationships between permeability and fractal dimension, ringing count response under coal specimen fracture (pore) were analyzed, and the acoustic emission fractal-permeability model of coal specimens under hydraulic-loading coupling were established. The permeability experiments of coal specimens with hydraulic-loading coupling in different confining pressures (2−5 MPa，Δpw/p'c=0.75) were carried out, and the mechanical behavior, permeability characteristics and acoustic emission rules of coal specimens in different confining pressures (water pressure) were analyzed, and the relationship between the failure morphology of coal samples under different confining pressures and the acoustic emission positioning was discussed. The strength enhancement characteristics and the relationships between failure pattern and acoustic emission location of coal specimens under confining pressures were discussed. The rationality of the fractal-permeability model of coal specimens under hydraulic-loading coupling was verified. The results showed that the fracture (pore) change of coal specimen was consistent with acoustic emission ringing, the fracture (pore) development was closely related to the fractal dimension and the permeability, and the acoustic emission fractal and permeability could be characterized by the volume strain in the permeability experiments. The acoustic emission fractal-permeability model of coal specimen under hydraulic-loading coupling could be analyzed by a two-stage mathematical model. The permeability of the coal specimen showed the process of short-term decrease, long-term slow increase, rapid increase and slight decline, and the ringing count showed the wave-like development of rapid increase - decrease - increase - decrease during the total stress-strain process of coal specimen, the minimum permeability lagged behind the critical point of volume strain compression and expansion, and the minimum permeability varied from 0.124×10−17 m2 to 1.250×10−17 m2. With the increase of confining pressure (2−5 MPa), the peak deviating stress, peak axial strain and peak volume strain of coal specimen all showed an increasing trend, the linear characteristics were significant, the lag of peak permeability behind peak strength showed a decreasing trend, the reduction reached 93.34%, and the loudest ringing count (corresponding to the peak strength) showed an increasing trend. The effective cohesion and the effective internal friction angle of the coal specimen increased to 6.511 6 MPa and 36.56º under hydraulic coupling, respectively. With confining pressure (2−5 MPa) increase, the acoustic emission information of coal specimen changed from single inclined plane to irregular inclined plane, the angle of the main fracture plane from small angle to high angle, and the instability mode from single block shear to multi-block compression, and the specimen fracture could be expressed by acoustic emission positioning ringing count. Three experiment curves of acoustic emission fractal-volume strain, permeability and volume strain, and fractal and permeability of the coal specimens were consistent with the theoretical curves, the correlation during compression stage with confining pressure 2−5 MPa was 0.882−0.999, 0.950−0.998 and 0.849−0.997, respectively. The correlation during the expansion stage was 0.937−0.996, 0.891−0.998 and 0.873−0.966, respectively.

The understanding of rainfall-induced landslides on gentle, loose-fill slopes is limited in comparison to steep slopes. Hence, two physical model tests were conducted on silty sand slopes under continuous rainfall: one on a bare slope and the other on a slope planted with ryegrass. The slope angle of 25° is much lower than the internal friction angle of slope material (34.3°), which makes the model test fall well into the category of gentle slope. For the initially unsaturated bare slope, a rainfall event with return period of 18 years could trigger a rapid and retrogressive global sliding, which differs from previous findings that gentle slopes would only experience shallow failure. A sudden increase in pore-water pressure was simultaneously observed, which might be generated by the wetting-induced collapse of unsaturated loose soil. On the other hand, the stability of the slope with grass plantation was significantly enhanced, and it was able to withstand rainfall event more severe than those with a return period of 100 years, with only minimal deformation. The results suggest that the gain in shear strength due to ryegrass roots surpasses the additional sliding force caused by the increased water retention capability. Additionally, it is found that the abrupt change in pore pressure was no longer indicative of slope failure in the case of the grass-reinforced slope. [ABSTRACT FROM AUTHOR]

To assess connections between these notches throughout fracture formation under stress, the mechanical performance of granite specimens with two non-parallel notches underwent a biaxial compression test. The first notch had a 45° angle, whereas the second had a variable angle (0°, 45°, 90°, 130°, and 180°). Three ligament angles (0°, 45°, and 90°) were measured between the inner tips of two notches and the horizontal axis. The ligament length, distance between the inner tips of the two notches, and both notch lengths were each 2 cm. These samples were examined at 0, 1, and 3 MPa confining pressures. By using the particle flow code (PFC), simulated results of the evaluations were run after the trials. It was discovered that the specimens' failure strengths were influenced by the notch's geometric characteristics, which in turn impacted the failure mechanism as well as fracture geometry. The number of tensile fractures had an impact on the specimens' failure strengths. Whilst also increasing the ligament angle, more induced tensile cracks were produced. In the early stages of loading, just a few AE events were found, but after that, they multiplied quickly before approaching the peak stress. By raising the confining pressure, the AE hits were increased and delay failure was occured. The failure strength and AE hits are significantly impacted by the second notch's angle. In constant ligament angel, the compressive strength of models containing overlapped joint were more than that with non-overlapped joints. In models containing non-overlapped notches, the model with ligament angles of 0° and 45° had maximum and minimum compressive strength, respectively. In models containing overlapped notches, the model with ligament angles of 90° and 45° had maximum compressive strength and minimum compressive strength, respectively. In all ligament angles, minimum compressive strength was occurred when the upper joint angle was 45°. Both the computational and experimental methodologies showed that the specimens' failure pattern and compressive strength were very comparable. [ABSTRACT FROM AUTHOR]

Mining-induced landslides are a common form of disaster in the mountainous areas of coal mines. To clarify the deformation and failure patterns of such slopes under the mining action, the particle discrete element method was employed to simulate the destabilization damage process of the anticline coal seam slope under two conditions, single-seam mining and three-seam mining, and analyze the characteristics of crack expansion and rock fragmentation during slope deformation, based on the field investigation of typical mining-controlled landslides. The results show that: 1) In a single-seam condition, an arch-ring type deformation zone is created in the roof area after the coal seam is excavated and evolves into a fallen rock body; while the rock body at the interval of multi-layer excavation will be bent sink collapse, forming a large area of rock fragmentation. 2) Under different excavation conditions, the internal crack evolution and rock fragmentation of the slope are slow at the beginning of the formation of the fall zone and stress redistribution. The stage of roof emergence and rock bending fracture is the main stage of rock fracture and fragmentation. 3) The anti-inclined coal seam mining-controlled mountain failure pattern is mainly manifested as follows: Coal seam mining →Arch-loop-like fall of the roof →Bending and sinking of the internal rock →Pulling and breaking of the trailing edge →Failure of the locking zone at the foot of the slope → Shallow sliding of the fragmented rock. This study provides a new direction for the analysis of the destabilization mechanism of mining-controlled slopes and scientific guidance for the prevention and control of landslide hazards in mining areas.

The underground storage of gases, such as CO2 and H2, in the porous media is a critical component for achieving carbon neutrality and economical energy storage. While previous research has predominantly focused on gas injection in one piece of uniform porous media, and gravity is often neglected, the reality is that natural storage formations are typically multi-layered porous systems. An in-situ gas injection apparatus based on highresolution micro-CT was utilized to investigate gas injection behaviors and failure patterns in layered porous media systems. The system includes a reservoir layer and a cap layer, where both capillarity and permeability are meticulously controlled. Our findings reveal that all cases experience cycles of a pressure built-up period and a sudden pressure release when a barrier, either capillarity or effective stress, is overcome. Drainage conditions within the layered system significantly impact both the volume of gas trapped and the failure patterns observed. Effective stress analyses show that the key determinants of failure patterns are capillarity, effective stress, and excess pore fluid pressure, affected by pore size, cap layer thickness, gas injection rate and permeability. Five distinct failure patterns are categorized: capillary invasion, fracture opening, integral uplifting, local heaving, and violent liquefaction-based on two dimensionless parameters. This work provides new insights into understanding the gas injection dynamics in layered porous media. [ABSTRACT FROM AUTHOR]

Calcareous sand, which is characterized by irregular morphologies and abundant intraparticle pores, poses difficulties for ocean construction. This study investigated the effects of microbially induced carbonate precipitation (MICP) treatment methods and grain size on the biocementation of calcareous sand. Calcareous sand specimens with a wide range of grain sizes were first treated by MICP with immersion and mix methods. Scanning electron microscopy analysis revealed the presence of air bubbles inside the specimens treated by the mix method, which hindered biocement production, further promoting the emergence of a gradual failure pattern and reducing the strength and stiffness of the sand specimens. A series of unconfined compressive strength tests indicated that the strength and stiffness of the calcareous sand specimens treated by the immersion method were considerably greater than those of the specimens treated by the mix method in the suitable grain size range. In addition, the immersion method was not suitable for sand specimens with a median grain size of <0.5 mm. By contrast, the mix method was suitable for sand specimens of various sizes. As with the immersion-treated specimens, the specimens treated by the mix method displayed better mechanical properties at the early treatment stages, although the mix method-treated specimens exhibited much lower increase rates of strength and stiffness; moreover, the mix method-treated specimens exhibited lower strength and stiffness after long-term treatment than the immersion-treated specimens. [ABSTRACT FROM AUTHOR]

Shale affects reservoir fracture sprouting and expansion during fracture modification. The aim of this study was to investigate the influence of calcite veins with distinct flaw inclinations on the stretch strength and destruction pattern of shale. In the text, we reconstructed 3D numerical models of shale with seven groups of different calcite vein inclinations using CT scanning of shale specimens from the Niutitang Formation in the Feng'gang No. 3 block in the northern part of Guizhou Province and performed Brazilian splitting simulation tests. Research shows the effect of the calcite vein angle on the ultimate tensile strength and damage mode of shale, and the damage modes mainly include tensile damage, tensile-shear damage, pressure-shear damage and compression damage. Calcite veins have a significant structural effect on the tensile strength of shale. Due to the change in calcite vein inclination, the stress decomposition on the specimen acts on the positive and shear stresses along the calcite vein direction changes significantly, which results in a large difference in the splitting stress between calcite veins and shale matrix when destabilization damage occurs. The research efforts have a key impact on the crack mechanism of shale hydraulic fracturing, fracture expansion law and the improvement of shale gas recovery rate. [ABSTRACT FROM AUTHOR]

To explore and compare the failure modes, deformation behaviors, and load-bearing capacities of single-edge notched (SEN) beams strengthened with carbon fiber-reinforced polymer (CFRP) and steel bars, static and dynamic three-point bending tests on both types of concrete beams have been carried out in this study. During the static tests, the electro-hydraulic servo machine served as a loading device to apply pressure to CFRP beams and reinforced concrete (RC) beams. During the impact experiments, different impact velocities were imparted by adjusting the drop hammer's height. Thus, information regarding crack propagation, energy absorption, and deformation was obtained. The results from the static tests showed that the RC beams predominantly experienced shear failure. In contrast, the CFRP beams primarily exhibited bending–shear failure, attributed to the relatively weaker bond strength between the bars and the concrete. Impact tests were conducted at three different velocities in this study. As the impact velocity increased, both types of concrete beams transitioned from bending failure to bending–shear failure. At the lowest velocity, the difference in energy absorption between beams reinforced with different materials was insignificant during the bending process. However, at the highest velocity, CFRP beams absorbed less energy than RC beams. The study of structures' impact failure modes and their mechanical characteristics offers valuable references for the anti-collision design and protection of structures. [ABSTRACT FROM AUTHOR]

It is of great significance to study the influence of freeze–thaw cycles on rock for the prevention and treatment of tunnel diseases in cold regions. Up to 300 freeze–thaw cycles were carried out on red sandstone, and the uniaxial compression and increasing amplitude cyclic loading tests were conducted to investigate its physical and mechanical responses. A damage calculating method is established, and a conceptual model is proposed to illustrate the behaviors of rock subjected to freeze–thaw cycles and increasing amplitude cyclic load. Research results indicate that the porosity of red sandstone increases in a negative exponential manner with the increase of freeze–thaw cycles, while the strength, residual strength, elastic modulus and Poisson's ratio decrease linearly. The strength of red sandstone can reduce by 21.27% when subjected to 300 freeze–thaw cycles. There are three kinds of acoustic emission (AE) patterns before failure, which are early active, medium term active and inactive. The damage considering the coupled effect of freeze–thaw cycles and increasing amplitude cyclic load can be calculated based on the elastic modulus degradation and damage release energy. By using the proposed method, a comparison of damage evolution between uniaxial compression and cyclic loading can be conducted, and the mechanical properties and damage propagation characteristics of rock can be predicted. The more freeze–thaw cycles the rock undergoes, the more microcracks inside it, and the more broken it becomes after failure. As the microcracks inside rock increase gradually, the internal structure of rock progressively becomes loose and brittle, resulting in a decrease in macroscopic mechanical characteristics such as strength and elastic modulus. Rock can be deemed as a system composed of a series of springs with different stiffnesses and lengths. The evolution of strength, elastic modulus and acoustic emission can be expressed by the failure and the uneven deformation between adjacent springs. Highlights: The effect of freeze-thaw cycles on physical and mechanical parameters are revealed. Rock damage and its growth rate increase as the freeze-thaw cycle increases. Damage is analyzed based on elastic modulus degradation and damage release energy. A spring conceptual model is proposed to illustrate the rock damage mechanism. [ABSTRACT FROM AUTHOR]

This study presents a new solution algorithm to calculate the bearing capacity coefficient Nγ for a fully rough strip footing located on an infinite slope considering different soil friction angles φ and ground slopes β° using the stress characteristics method. The results showed that Nγ coefficients decreased with an increase in slope inclination, and roughness contribution prevented further reduction, particularly for higher φ values. The higher contribution of the upside-sloping ground for footing laid on the infinite slope led to a lower reduction of the Nγ coefficients compared with the footing placed at the slope vicinity in terms of a larger area affected by the stress field, and a larger plastic region of the downface slope. The reduction value was more eminent for steeper slopes β ≥ 20° due to the tendency for nonsymmetrical failure pattern, especially for higher φ values. The findings of the current research and those described in the literature were in good agreement, so much so that the lower-bound limit analysis and the current solution technique virtually reflect the same trend. The load inclination values for footings located adjacent to the slope with β ≤ 30° were not meaningful, whereas for footing resting on an infinite slope with β ≥ 25° it exceeds 15°, which reflects the fact that its effect should not be neglected, especially for ground slopes greater than 20°. By increasing β°, the maximum values of plastic length and plastic depth on the left and right sides of the footing decrease and increase, respectively. The maximum depth of the plastic region for β ≥ 20° from around the right side of the footing shifts toward the downward-sloping face. The maximum width of the elastic wedge gradually reduces, and the intersection point of the left and right plastic regions slowly shifts to the left and upside of the footing. [ABSTRACT FROM AUTHOR]

Adding steel fiber to concrete preparation to enhance residual strength and ductility is a potential solution to improve reliability of specific concrete members with compression–shear loading zones, such as deep beams, trusses and column joints, after exposure to high temperature. In this study, the primary aim is to explore the impact of steel fibers on concrete behaviors in shear failure under various exposure temperatures and normal stress. Compression–shear performance of steel fiber reinforced concrete was tested under several conditions of volume fraction of steel fibers (Vsf = 0, 1.0%, 1.5%, and 2.0%), exposure temperature (T = 20 °C, 200 °C, 400 °C, and 600 °C), and normal stress ratios (k = 0, 0.2, 0.4, 0.6, and 0.8), and compression–shear failure patterns and load–shear displacement curves were investigated. The results demonstrate that incorporation of steel fibers enhance ductile behavior of specimen under compression–shear loading, with a higher presence of friction traces and jagged edges appearing at shear interface. After temperature treatment above 400℃, the characteristics of tensile failure gradually disappear, while more crushed failure occurs. The peak shear strengths decrease significantly with the increase of exposure temperature. For different volume fraction of steel fibers (1.0%, 1.5%, and 2.0%), the shear strengths at 400 °C increase by 12.5%, 15.9%, and 11.1%, respectively. The optimal compression–shear strengthening effect is Vsf = 1.5%. Finally, according to the experimental results, the equivalent strength τoct − σoct theoretical calculation model is determined to be the most suitable compression–shear strength prediction of SFRC at various temperatures. [ABSTRACT FROM AUTHOR]

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To study the influence of inclusions on the fracture evolution and mechanical properties of mortar structures, a series of uniaxial compression tests for mortar samples containing cylinder inclusions of varying mechanical properties were conducted. The digital image correlation (DIC) technique was employed for the analysis of deformation characteristics. In addition, failure modes for each sample were determined using self-documenting code. The result shows that inclusions filled in holes significantly influence the mechanical properties and failure characteristics of mortar structures as they can change the stress distribution and cracking process. Cracks are typically initiated at the boundaries of the inclusions but will only extend into the inclusion if it is less robust than the surrounding matrix. Sample strength increases significantly with an increase in sample strength when the inclusion's strength does not surpass that of the surrounding material. Once the inclusion's strength exceeds that of the surrounding matrix, the strength of the specimen remains relatively unchanged. [ABSTRACT FROM AUTHOR]

Understanding and predicting the failure modes of transversely isotropic (TI) rocks is essential for designing stable structures and evaluating rock failure incidents, including ground falls, slope stability, and landslides. Compared to isotropic intact rock, TI intact rock exhibits distinct failure modes. Until now, the failure mode of TI rocks has often been related to layer orientation and confinement pressure, with little consideration given to micro-scale parameters. This study investigates how layer orientation and grain size influence the failure mode of layered sandstone under confined and unconfined conditions. A comprehensive laboratory experiments involved 105 layered sandstone samples, featuring variations in grain sizes (fine, medium, and coarse), application of five distinct confining pressures, and testing at seven different orientations. Through rigorous analyses of the post-failure layered sandstone using a random forest classification method, this study developed a predictive chart capable of determining TI rock failure mode based on layer orientation and confinement pressure. Intriguingly, the study also underscores that grain size exerts an insignificant impact on influencing these failure modes. The resultant predictive chart is expected to significantly enhance our comprehension and interpretation of rock failure in both laboratory and field applications, offering invaluable insights for engineering structures associated with TI rocks. Highlights: Confining pressure and layer orientation significantly influence the failure modes of transversely isotropic rocks, with grain size demonstrating negligible impact. The Random Forest Method constructed a predictive failure mode chart, effectively classifying regions into sliding/non-sliding and tensile/shear boundaries. The classification identifies three primary groups of failure modes: layer failure, matrix failure, and mixed failure. The classification of Type 1 and Type 2 mixed failures between the sliding and non-sliding regions, enhancing the granularity of classification. [ABSTRACT FROM AUTHOR]

The microscale mechanisms underlying the suction anchor–sandy soil interaction under slidable pulling actions of mooring lines remain poorly understood. This technical note addresses this knowledge gap by investigating the suction anchor–sandy soil interaction from micro to macro, with a particular emphasis on the effect of interface friction. The discrete element method (DEM) was utilized to simulate the sandy soil, while the finite element method (FEM) was employed to model the suction anchors. The peak pulling forces in numerical simulations were verified by centrifuge test results. The research findings highlight the significant influence of interface friction on the pulling force–displacement curves, as it affects the patterns of suction anchor–sandy soil interactions. Furthermore, clear relationships were established between the magnitude of interface friction, rotation angle, and pullout displacement of suction anchors. By examining the macro-to-micro behaviors of suction anchor–sandy soil interactions, this study concludes with a comprehensive understanding of failure patterns and their key characteristics under different interface friction conditions. The findings proved that the interface friction not only influences the anti-pullout capacity but also changes the failure patterns of suction anchor–soil interactions in marine engineering. [ABSTRACT FROM AUTHOR]

Abstract As the anisotropic behavior of sandstones and limestone along the Khorramabad-Zal expressway has not been studied, this research aims to examine the impact of layer orientation on the strength characteristics and failure patterns of layered sedimentary rocks using the Brazilian test. For this purpose, a total of 8 rock blocks were gathered from Kashkan sandstones and Sarvak limestones in three different locations along the Khorramabad-Zal highway in western Iran. The core specimens were drilled with 54 mm diameter and parallel to the laminations. Overall 150 disc-shaped specimens were subjected to Brazilian tensile strength (BTS) in ten different anisotropy angles, which refers to the angle between the loading direction and the lamination plane. The findings revealed that the highest and lowest BTS values were obtained at β = 70° and 20° for all three types of rock. After analyzing the samples that experienced the Brazilian test and examining their failure patterns, three primary modes of failure were identified: parallel to the lamination (PL), across the lamination (AL), and curved fracture (CF). Furthermore, the transitional angle, which signifies the point at which the dominant pattern of failure shifts from PL to AL or from PL to CF, was also determined.

Jointed rock mass with internal rough structural planes have a significant influence on the mechanical behaviour and damage mode of the rock mass. Based on the Weierstrass-Mandelbrot (W-M) fractal function, a numerical model containing a single rough fracture was established. Multi-parameters sensitivity analysis was carried out to determine the key parameters affecting the mechanical properties. By conducting experimental research on the single fracture inclination, fractal dimension, and surface precision of numerical model uniaxial compression, the influence laws of different parameters and the model cracking process were revealed. The results show that the cracks go through the process of sprouting from the single fracture and expanding to both sides, and the expansion of shear cracks in the structural plane reflects the roughness pattern of the structural plane. The higher the roughness was, the lower the peak uniaxial compression strength of the model was. The change of the parameters influenced the macroscopic cracking morphology of the model, and the model finally showed the destruction along the diagonal, the V-shaped destruction, the X-like destruction, and the X-type destruction. The results have an outstanding reference value for further researches on the application of three-dimensional rough discrete fracture networks.

Prefabricated retaining wall is in line with the development trend of greening and environmental protection of civil engineering, and has a broad application prospect. However, the seismic response of prefabricated retaining wall has not been systematically revealed. Therefore, in this study, a simple fabricated cantilever retaining wall with connecting plate was proposed, and the mechanical properties of prefabricated cantilever retaining under dynamic effect was investigated by the experimental and numerical methods. At first, the physical model experiments of prefabricated cantilever retaining with different vertical plate thicknesses were carried out. Subsequently, the mechanical properties of the prefabricated cantilever retaining were investigated. The research results show that the thickness of retaining wall significantly affects the failure pattern, the larger the thickness, the more complete the broken pattern. In addition, the connection between the vertical plate and the bottom plate is prone to cracks induced by stress concentration, eventually leading to damage. As the thickness of the vertical plate increases, the top stress of the vertical plate decreases but the bottom stress increases. The greater the embedded depth of the vertical plate, the larger the stress at bottom of the vertical plate. Furthermore, the effect of concrete strength on mechanical properties is not obvious. This study provides an idea for the dynamic response research of prefabricated retaining structure. [ABSTRACT FROM AUTHOR]

There is potential danger of conical shear failure surface in karst cave roof under pile foundation load. To understand the mechanical and failure characteristics of rocks under such conditions. In this study, an auxiliary device consisting of an indenter and a hollow support combined with a servo-controlled mechanical equipment was used to perform mixed compression-shear tests. The laboratory tests were studied numerically by finite difference methods. This study set up 4 groups of height variables 20, 30, 40, 50 mm and 3 groups of aperture variables 20, 30, 40 mm. AE (acoustic emission) tests are adopted to study the failure characteristics of specimen. The experimental results show that the peak load increases with the sample height while decreases with the aperture of support. This paper defines an apparent elastic modulus in terms of displacements and loads, which increases with height by 42.12, 51.7, and 49.00 KN/mm for apertures from 20 to 40 mm. The AE data show that the ratio of RA (ratio of rise time to maximum amplitude) to AF (average frequency of AE count) gradually increases as the support aperture increases, indicating that the aperture is approximately close to the radius of the indenter and that shear damage is approximately significant. The numerical simulation results show that the shear stress is the largest at the position where the upper surface of the specimen contacts with the indenter, and the displacement is the largest at the position where the lower surface of the specimen overlaps with the support hole. The extrusion phenomenon caused by dilatation is the main reason for the tensile failure detected during the experiment. [ABSTRACT FROM AUTHOR]

As the anisotropic behavior of sandstones and limestone along the Khorramabad-Zal expressway has not been studied, this research aims to examine the impact of layer orientation on the strength characteristics and failure patterns of layered sedimentary rocks using the Brazilian test. For this purpose, a total of 8 rock blocks were gathered from Kashkan sandstones and Sarvak limestones in three different locations along the Khorramabad-Zal highway in western Iran. The core specimens were drilled with 54 mm diameter and parallel to the laminations. Overall 150 disc-shaped specimens were subjected to Brazilian tensile strength (BTS) in ten different anisotropy angles, which refers to the angle between the loading direction and the lamination plane. The findings revealed that the highest and lowest BTS values were obtained at β = 70° and 20° for all three types of rock. After analyzing the samples that experienced the Brazilian test and examining their failure patterns, three primary modes of failure were identified: parallel to the lamination (PL), across the lamination (AL), and curved fracture (CF). Furthermore, the transitional angle, which signifies the point at which the dominant pattern of failure shifts from PL to AL or from PL to CF, was also determined. [ABSTRACT FROM AUTHOR]

Shale oil in China is mainly concentrated in lacustrine shale reservoir, which has poor structural continuity, strong heterogeneity and strong anisotropy. It is of theoretical significance to study the structural characteristics and mechanical properties of lacustrine shale to improve the exploitation effect of lacustrine shale oil in China. In this investigation, the lamellar lacustrine shale of Chang 7 member of Yanchang in Ordos Basin, which is rich in shale oil, is selected for study, the natural lamellar structures were characterized quantitatively and the true triaxial compression tests were concluded. It found that the thickness distribution of total, light, and dark laminae follows an exponential, power and transformed logarithmic function, which can be used to build lacustrine shale laminar structure models of different sizes more precisely. In addition, with increasing of intermediate principal stress, the ratios of crack initiation stress (σci) and damage stress (σcd) to peak strength (σc) both decrease, and the connection degree between the activated natural cracks and new cracks is more obvious. Moreover, it found that laminae types and morphologies have effect on the type and number of new cracks, and natural crack characteristics affect the connection form between natural and new cracks. These illustrate that the inhomogeneity of initial structure characteristics and the stress condition of true triaxial loading jointly affect the crack propagation and failure pattern of lacustrine shale, the reduced stress ratio and fracture combination failure mode indicates that lacustrine shale is a favorable rock facies for fracturing. These conclusions can provide part essential data for establishing the geometric model of lacustrine shale and provide theory reference for the optimization design of fracturing scheme in lacustrine shale oil exploitation. [ABSTRACT FROM AUTHOR]

Understanding the mechanical behaviour of jointed rock during seismic events is crucial for ensuring the stability of rock engineering. A series of uniaxial compression tests were conducted on granite specimens containing a persistent joint at strain rates (10−5–0.05/s). Acoustic emissions (AEs) were monitored to detect the rock fracturing, and the strain field on the specimen surface was measured by the digital image correlation technique. Three failure patterns of specimens were observed: rock splitting, joint slipping and mixed rock splitting–joint slipping. The shapes of typical strain–stress curves for the three patterns are different, but they are all characterised by multiple stress drops indicating significant rock fractures. When significant fractures occur, the frequency range of AEs expends and the dominant frequency of AEs becomes much larger. The specimen strength is affected by the strain rate, but this effect differs for different failure patterns of specimens. The joint inclination could influence the mode and profile of fractures near the joint, and the specimen strength and joint stiffness significantly decrease with increasing joint angle. This study could help better understand the behaviour of jointed rocks subjected to seismic loads. [ABSTRACT FROM AUTHOR]

The shear mechanical behavior of discontinuities under unloading conditions induced by intensive rock mass excavation differs from that under loading conditions. Therefore, the mechanical parameters obtained from the conventional direct shear test cannot effectively be used to assess the stability of excavated rock masses. To solve this problem, we conducted a series of experiments on saw-toothed discontinuities with different undulating angles and initial shear stresses under unloading normal stress with constant shear stress. The test results showed that the shear pattern transformed from climbing to climbing-gnawing and then to gnawing patterns as the undulating angle and initial shear stress increased. The shear stress remained stable with increasing shear displacement after instability in the climbing pattern, decreased with fluctuations in the climbing–gnawing pattern, and dropped steeply in the gnawing pattern. A negative linear correlation exists between the unloading magnitude and the initial shear stress. Unloading normal stress promoted deformation rebound and sawtooth damage, reducing the mobilizing shear strength. Modified Patton and Barton shear strength criteria considering the undulating angle, initial stress, and failure pattern under unloading normal stress were proposed. Highlights: The shear mechanical behavior of saw-toothed discontinuities with different undulating angles and initial shear stresses under unloading normal stress with constant shear stress are investigated. The failure pattern changes from the climbing pattern to the climbing–gnawing pattern and then to the gnawing pattern as the undulating angle and the initial shear stress increase. Unloading promotes the increase in rebound deformation and the area of the damage zone, leading to the decrease in shear strength of saw-toothed discontinuities. The modified Patton criterion and the Barton criterion are proposed for unloading normal stress considering the undulating angle, initial stress state, and failure pattern. [ABSTRACT FROM AUTHOR]

Research on the deformation characteristics and failure modes of buried pipelines under local suspension conditions caused by groundwater loss in coal mining subsidence areas is conducive to grasping the failure evolution law of pipelines and providing technical support for the precise maintenance of gathering and transportation projects and the coordinated mining of gas and coal resources. First, a test system for monitoring the deformation of pipelines under loading was designed, which mainly includes pipeline load application devices, end fixing and stress monitoring devices, pipeline end brackets, and stress–strain monitoring devices. Then, a typical geological hazard faced by oil and gas pipelines in the gas–coal overlap area—local suspension—was used as the engineering background to simulate the field conditions of a 48 mm diameter gas pipeline with a localized uniform load. At the same time, deformation, top–bottom strain, end forces, and damage patterns of the pipeline were monitored and analyzed. The results show that the strain at the top and bottom of the pipeline increased as the load increased. In this case, the top was under pressure, and the bottom was under tension, and the conditions at the top and bottom were opposite.. For the same load, the strain tended to increase gradually from the end to the middle of the pipeline, and at the top, it increased significantly more than at the bottom. The tensile force carried by the end of the pipeline increased as the applied load increased, and the two were positively correlated by a quadratic function. The overall deformation of the pipeline evolved from a flat-bottom shape to a funnel and then to a triangular shape as the uniform load increased. In addition, plastic damage occurred when the pipeline deformed into a triangular shape. The results of the investigation clarify for the first time the mathematical relationship between local loads and ultimate forces on pipelines and analyze the evolution of pipeline failure, providing a reference for pipeline field maintenance. Based on this, the maximum deformation of and the most vulnerable position in natural gas pipelines passing through a mining subsidence area can be preliminarily judged, and then the corresponding remedial and protection measures can be taken, which has a certain guiding role for the protection of natural gas pipelines.

Objective: To analyze the failure patterns in patients with different histological subtypes of sinonasal malignancies (SNMs). Study Design: Retrospectively gathered data. Setting: Academic university hospital. Methods: Patients with SNMs treated at a tertiary referral center between January 1999 and January 2019 were included. We assessed the failure patterns within different histological subtypes. Results: The study included 897 patients. The median follow‐up time was 100 months. Adenoid cystic carcinoma (ACC) had a moderate risk of developing local recurrence (LR) and distant metastasis (DM). Compared with ACC, squamous cell carcinoma (SCC), adenocarcinoma (AC), soft tissue sarcoma (STS), and mucosal melanoma (MM) were classified as a high LR risk group. For DM, neuroendocrine carcinoma (NEC), STS, and MM were in the high‐risk group. Conclusions: ACC had intermediate local and distant failure risks, while SCC, AC, STS, and MM were at high LR risks. NEC, STS, and MM were at high DM risk. [ABSTRACT FROM AUTHOR]

Evaluation of the seismic performance of two historical stone arch bridges of the Iranian rail network is presented using a discrete element method. The total length of the bridges is 66.7 m and 106.1 m. The bridges consist of multi-span arches changing from 5 m to 48.6 m. The incremental dynamic analysis method is used to determine the damage, failure patterns, and acceleration of the collapse threshold. Using the discrete element method after static analysis under gravity load, dynamic analysis of bridges under both horizontal components of the earthquakes was performed simultaneously for different earthquake intensities until collapse. The results showed that the most extensive damage occurred in the smaller bridge with the onset of failures in the top spandrels of the arches and then the piers of the bridge, while in the larger bridge which had a large central arch span, damage and failure occurred more in the central arch and its spandrels. The collapse spectral acceleration of the larger bridge is considerably smaller than the smaller bridge such that the ratio of collapse spectral acceleration of the larger to smaller bridge varies only between 45% to 61%. The low spectral acceleration intensity of collapse indicates more seismic vulnerability of the larger bridge. [ABSTRACT FROM AUTHOR]

High strength concrete (HSC) with superior strength advantage has been gaining widespread attention and engineering endorsement in recent years. For a better understanding of the mechanical responses and failure mechanisms of HSC, a novel three‐dimensional (3D) mesoscale model considering the meso‐structural features of concrete was proposed in this paper. First, a series of uniaxial compressive tests were conducted to investigate the compressive properties of HSC specimens with a strength of 80–90 MPa. After that, a 3D three‐phase mesoscale model consisting of mortar, coarse aggregate, and the interfacial transitional zone (ITZ) between them, was developed to perform the mesoscopic simulations of HSC. Then, systematic analysis and discussions on the compressive properties of HSC were presented in terms of the stress–strain curves, compressive strengths/toughness, failure patterns, cracking process, etc. Results indicate that HSC exhibited obvious brittle failure characteristics, and its strength was significantly related to the water‐to‐cement ratio and mineral admixture. At meso‐level, the cracking behaviors of mortar and ITZ phases were well modeled using the developed mesoscale model. Additionally, it was found that the cracking behavior of HSC was significantly associated with the ITZ characteristics. The developed mesoscale modeling approach has been proven to simulate and investigate concrete's compressive properties in a reliable manner, and can be applied further to the property analysis of concrete materials and structures. [ABSTRACT FROM AUTHOR]

The current recommendation for postoperative radiotherapy for esophageal cancer in China is mainly based on the data of incomplete two-field dissection of open left thoracotomy. At present, the type of surgery for esophageal cancer gradually transitions from open left thoracotomy to open right thoracotomy and from open esophagectomy to minimally invasive esophagectomy (MIE). Patients with early-stage esophageal cancer are selected as candidates for MIE. MIE is less invasive than open esophagectomy, and the right thoracic approach is conducive to more thorough lymph node dissection. However, few data and related studies are available on the patterns of failure after MIE in esophageal cancer, and guiding an adjuvant therapy is difficult. The feasibility of an adjuvant therapy for selective high-risk patients and the optimized treatment after MIE remains to be explored in clinical practice. In this regard, this article aims to review the safety of MIE, long-term survival outcomes, postoperative recurrence patterns, and recurrence rates of patients to discuss the value of postoperative adjuvant therapy and guide clinical treatment.

To explore and compare the failure modes, deformation behaviors, and load-bearing capacities of single-edge notched (SEN) beams strengthened with carbon fiber-reinforced polymer (CFRP) and steel bars, static and dynamic three-point bending tests on both types of concrete beams have been carried out in this study. During the static tests, the electro-hydraulic servo machine served as a loading device to apply pressure to CFRP beams and reinforced concrete (RC) beams. During the impact experiments, different impact velocities were imparted by adjusting the drop hammer’s height. Thus, information regarding crack propagation, energy absorption, and deformation was obtained. The results from the static tests showed that the RC beams predominantly experienced shear failure. In contrast, the CFRP beams primarily exhibited bending–shear failure, attributed to the relatively weaker bond strength between the bars and the concrete. Impact tests were conducted at three different velocities in this study. As the impact velocity increased, both types of concrete beams transitioned from bending failure to bending–shear failure. At the lowest velocity, the difference in energy absorption between beams reinforced with different materials was insignificant during the bending process. However, at the highest velocity, CFRP beams absorbed less energy than RC beams. The study of structures’ impact failure modes and their mechanical characteristics offers valuable references for the anti-collision design and protection of structures.

To study the influence of inclusions on the fracture evolution and mechanical properties of mortar structures, a series of uniaxial compression tests for mortar samples containing cylinder inclusions of varying mechanical properties were conducted. The digital image correlation (DIC) technique was employed for the analysis of deformation characteristics. In addition, failure modes for each sample were determined using self-documenting code. The result shows that inclusions filled in holes significantly influence the mechanical properties and failure characteristics of mortar structures as they can change the stress distribution and cracking process. Cracks are typically initiated at the boundaries of the inclusions but will only extend into the inclusion if it is less robust than the surrounding matrix. Sample strength increases significantly with an increase in sample strength when the inclusion’s strength does not surpass that of the surrounding material. Once the inclusion’s strength exceeds that of the surrounding matrix, the strength of the specimen remains relatively unchanged.

Abstract Shale reservoir is the research hotspot in the development of unconventional oil and gas resources. The properties of bedding plane have an important influence on the mechanical behavior of shale. According to the fracture characteristics of layered shale under Brazilian splitting load, the effects of bedding angle, bond strength ratio and natural fractures on the tensile strength and fracture pattern of layered shale in Brazilian splitting test were studied by particle flow code. The evolution mechanism of meso–macro fracture of shale is analyzed by combining the dynamic change process of particle mesoscopic force chain and crack. The results show that three types of fracture patterns are observed: splitting tensile failure of shale matrix, splitting tensile failure along bedding plane and tensile–shear composite failure along shale matrix and bedding plane. Mesoscopic cracks initiate at the top and bottom loading points of the disk. After the peak load, mesoscopic cracks propagate through and appear dense force chains until macroscopic failure occurs. The bond strength ratio of bedding plane affects the failure pattern and peak strength of the specimen. With the increase in bedding angle, the tensile strength decreases gradually. Considering the influence of natural fractures, the tensile strength of shale is lower, and the crack propagation is more complex. The research model and results provide theoretical basis for the mechanical properties evaluation and fracture pattern analysis of shale.

The low-permeability characteristic of sandstone-type uranium deposits has become the key geological bottleneck during the in-situ leaching mining, seriously restricting the development and utilization of uranium resources in China. At present, the blasting-enhanced permeability (BEP) and acidizing-enhanced permeability (AEP) are confirmed to be mainstream approaches to enhance the reservoir permeability of low-permeability sandstone-type uranium deposit (LPSUD). To clarify the synergistic effect of BEP and AEP, the acid-rock reaction and dynamic impact experiments were conducted, aiming to study the effect of chemical reactions on pore structure, dynamic mechanical properties and failure pattern of sandstone. Results show that with the increasing acid-rock reaction time, the total pore volume of samples is promoted largely and exhibits obvious chemical damage. The change of pore volume depends on the pore size, the 100–1000 nm and 1000–10000 nm pores are more susceptible to acid-rock reactions. The dynamic peak strength and the dynamic elastic modulus are decreased and the dynamic peak strain and strain rate are increased when lengthening the acid-rock reaction time, whose evolution laws can be fitted by the logistic expression, the linear expression and the exponential expression, respectively. The acid-rock reactions also have an influence on the fracture development of samples after the dynamic impact. The damaged fractures on the end faces of samples grow from the isolated short fracture, the isolated long fracture to the fracture network, and the damaged fractures on the sides of samples develop from the non-penetration fractures, penetration fractures to the multi-branch fractures. This study clarifies the physical and chemical combined damage mechanism, demonstrates the potential of reservoir stimulation by uniting the BEP and the AEP, and provides a theoretical reference for the reservoir stimulation of LPSUD.

Pretensioned Spun Precast concrete (SPC) pile has become a very popular solution for deep foundation systems for its easier installation, higher bearing capacity, and overall cost-effectiveness. The pile system also brings both material and construction sustainability to the environment through its cleaner construction process and reduced consumption of construction materials. However, the smaller shear area of SPC piles arising from its hollowness is a big concern particularly when they are subjected to earthquake-induced liquefaction situations. This paper investigates the shear behavior of hollow pre-tensioned SPC piles experimentally. A total of ten full-scale SPC piles comprising high-strength concrete (50 MPa) and high-tensioned (HT) steel strands were manufactured through the centrifugal rotation and steam curing construction process. The pile segments consist of a variation in two different diameters, numbers of strands, thicknesses, presence of spirals, and spacing. The compressive strength of concrete was determined from the compression tests of extracted core samples from the SPC piles. All pile specimens were tested under a four-point loading up to failure. The load-deformation responses, crack propagations, failure patterns, beam-deformation, and load-strain responses at the pile surface were investigated under different circumstances. The experimental results suggested that the presence of spirals plays a pivotal role in shear capacity and their failure patterns whereas the number of strands does not have a significant role in the shear capacity enhancement. The shear resistance of SPC piles was found in a range of 12–15 % and 8–11 % of their allowable axial capacity with and without the presence of spirals, respectively. The tested ultimate shear resistance is observed to be higher than that of all code-recommended values. This research offers useful information for the SPC pile’s shear design that demonstrates its application in deep foundations of the seismic regions.

The current recommendation for postoperative radiotherapy for esophageal cancer in China is mainly based on the data of incomplete two-field dissection of open left thoracotomy. At present, the type of surgery for esophageal cancer gradually transitions from open left thoracotomy to open right thoracotomy and from open esophagectomy to minimally invasive esophagectomy (MIE). Patients with early-stage esophageal cancer are selected as candidates for MIE. MIE is less invasive than open esophagectomy, and the right thoracic approach is conducive to more thorough lymph node dissection. However, few data and related studies are available on the patterns of failure after MIE in esophageal cancer, and guiding an adjuvant therapy is difficult. The feasibility of an adjuvant therapy for selective high-risk patients and the optimized treatment after MIE remains to be explored in clinical practice. In this regard, this article aims to review the safety of MIE, long-term survival outcomes, postoperative recurrence patterns, and recurrence rates of patients to discuss the value of postoperative adjuvant therapy and guide clinical treatment. [ABSTRACT FROM AUTHOR]

Shale reservoir is the research hotspot in the development of unconventional oil and gas resources. The properties of bedding plane have an important influence on the mechanical behavior of shale. According to the fracture characteristics of layered shale under Brazilian splitting load, the effects of bedding angle, bond strength ratio and natural fractures on the tensile strength and fracture pattern of layered shale in Brazilian splitting test were studied by particle flow code. The evolution mechanism of meso–macro fracture of shale is analyzed by combining the dynamic change process of particle mesoscopic force chain and crack. The results show that three types of fracture patterns are observed: splitting tensile failure of shale matrix, splitting tensile failure along bedding plane and tensile–shear composite failure along shale matrix and bedding plane. Mesoscopic cracks initiate at the top and bottom loading points of the disk. After the peak load, mesoscopic cracks propagate through and appear dense force chains until macroscopic failure occurs. The bond strength ratio of bedding plane affects the failure pattern and peak strength of the specimen. With the increase in bedding angle, the tensile strength decreases gradually. Considering the influence of natural fractures, the tensile strength of shale is lower, and the crack propagation is more complex. The research model and results provide theoretical basis for the mechanical properties evaluation and fracture pattern analysis of shale. [ABSTRACT FROM AUTHOR]

Abstract Objective We analyzed the patterns of lymph node (LN) failure and prognosis in patients with regional recurrent nasopharyngeal carcinoma (rNPC) alone after primary intensity‐modulated radiotherapy (IMRT). Methods A total of 175 patients who were treated with IMRT between 2010 and 2015 and who experienced regional recurrence alone were included. Recurrent LNs were re‐located in the initial pretreatment imaging and IMRT plan and failures were classified as in‐field or out‐field based on target volume delineation. All patients underwent curative salvage treatment. Independent prognostic factors for overall survival (OS) were selected by multivariate Cox analysis. Results Level IIb (49.1%, 86/175) was the most frequent recurrence site, followed by level IIa (36%), level III (18.9%), level IVa (12%), the retropharyngeal region (8%), level Va (6.9%), and the parotid region (6.9%). A total of 264 recurrent LNs were recorded: 149 (56.4%) were classified as in‐field failure with a prescribed dose ≥66 Gy, 60 (22.7%) with 60 to

The microscale mechanisms underlying the suction anchor–sandy soil interaction under slidable pulling actions of mooring lines remain poorly understood. This technical note addresses this knowledge gap by investigating the suction anchor–sandy soil interaction from micro to macro, with a particular emphasis on the effect of interface friction. The discrete element method (DEM) was utilized to simulate the sandy soil, while the finite element method (FEM) was employed to model the suction anchors. The peak pulling forces in numerical simulations were verified by centrifuge test results. The research findings highlight the significant influence of interface friction on the pulling force–displacement curves, as it affects the patterns of suction anchor–sandy soil interactions. Furthermore, clear relationships were established between the magnitude of interface friction, rotation angle, and pullout displacement of suction anchors. By examining the macro-to-micro behaviors of suction anchor–sandy soil interactions, this study concludes with a comprehensive understanding of failure patterns and their key characteristics under different interface friction conditions. The findings proved that the interface friction not only influences the anti-pullout capacity but also changes the failure patterns of suction anchor–soil interactions in marine engineering.

Purpose: Actionable mutations are common in non-small cell lung cancer (NSCLC)with malignant pleural effusion(MPE)(MPE-NSCLC). The pattern of failure in MPE-NSCLC treated with targeted therapy after MPE control remains unclear. We aimed to investigate the failure pattern of such patients in a cohort study and explore the possibility of radiotherapy. Patients and methods: Computed tomography scans of 86 patients were reviewed in this study. We classified first pattern of failure after MPE control as initial disease sites only (IF), new distant sites only (NF), or IF and NF detected simultaneously (INF). Patients evaluated suitable for radiotherapy after disease progression were divided into two groups: D group without radiotherapy and RD group with radiotherapy. The Kaplan-Meier method and log-rank test were used for survival analyses. Results: Disease progression after MPE control was observed in 42 patients with complete serial imaging. Median time to any progression was 9.5 months. Rate of the IF, NF and INF were 50%, 17% and 33% for all patients, 60%,0% and 40% for patients with MPE recurrence (n=10,23.8%) and 47%, 22% and 31% for patients (n=32,76.2%) without MPE recurrence, respectively. Out of 10 patients(23.8%) with MPE recurrence, 7 patients simultaneous underwent primary tumor progression and 5 MPE were cytologically confirmed in 7 patients with examination. The overall survival (OS)rates at 1, 2, 3 years for the RD group and D group were 88.2%, 50.5%, 21.7% and 80.0%, 20.3%, 0%, respectively; the corresponding MST were 26.1 months and 17.5 months, respectively (c2 = 4.959, p =0.026). Conclusions: Our data indicates that 50% of patients with actionable mutations MPE-NSCLC after MPE control are likely to fail at their initial sites of disease and the use of radiotherapy may bring OS benefits during the course of their disease. Multicenter RCT is necessary to confirm the result in the future. [ABSTRACT FROM AUTHOR]