Coupling Action Research Articles

Numerical Test Study on the Failure Mechanism of Coal-Rock Combined Body under the Coupling Action of Hydraulic and Mechanical

Coal and rock are often in an environment of hydraulic-mechanical coupling. In order to study the failure mechanism of the coal-rock combined body under the coupling action of hydraulic and mechanical, the RFPA-Flow software was used to analyze the failure mode, strength change law, and acoustic emission change law of the coal-rock combined body with different rock-to-coal height ratios under the combined action of uniaxial load and water pressure. The research results show that the peak strength, residual strength, and stress drop of coal-rock combined body with different rock-to-coal height ratios decrease after water pressure, which reduces the occurrence probability of rock bursts. However, the stress showed a vertical drop phenomenon in the later stage of loading, indicating that the coal-rock combined body still maintains the characteristics of brittle failure after being softened by water, and the roadway may still have rock bursts. The research conclusions can provide a theoretical basis for using water injection measures to prevent rock bursts in deep coal and rock masses.

Study on the Structural Plane Characteristics and Disaster-Induced Mechanism of the Yellow River Jingtai Stone Forest, Northwestern Loess Plateau, China

The Yellow River Jingtai Stone Forest (YJSF) is situated in the northwestern margin of the Chinese Loess Plateau, and it is not only one of the most precious and rare types of natural landforms in the Loess Plateau but also a protected area of valuable geological relics and landscapes in northwest China. Massive rock structural planes are present in the stone forest. However, few studies have been conducted on the rock mass structural planes for the slope’s stability. Based on the detailed field investigation, structural planes and their combination types are classified based on the rock mass. On this basis, combined with physical, mechanical, and hydraulic tests, the disaster-induced mechanism of the rock mass structural planes is classified and discussed. Results show that the structural planes of the YJSF can be divided into three types, namely, the primary structural plane, tectonic structural plane, and secondary plane. They not only combine with each other to cut the rock mass into different shape blocks but also jointly control the stability of the rock mass slope. The physical and mechanical tests and water sensitivity characteristics show that the conglomerates and muddy sandstones which are the main components of the YJSF have strong tensile and shear strengths under natural situations, while their strengths are reduced under immersion infiltration; in particular, the muddy sandstones are more sensitive to water and have a lower strength than that of the conglomerates. Finally, the disaster-induced mechanism of the YJSF is mainly related to the combination of various structural planes, which can be divided into four failure patterns, namely, creeping slide-tension failure, gradual failure, slipping failure, and dumping failure; coupling action of endogenic and exogenic geodynamic processes was responsible for their formation. The studied results will provide critical, theoretical, and technical support for the slope stability analysis, scenic geological heritage protection, and disaster warning in this area.

Seismic Performance and Design Method of Novel Resilient Outriggers

A novel seismic resilient outrigger was developed in this study, which is composed of high-strength steel chords with reduced beam sections (RBSs) and buckling restrained braces (BRBs). This energy-dissipating outrigger had a good deformation capacity and stable load-bearing capacity. Its chords remained elastic under the maximum considered earthquakes. Compared with conventional outriggers, it had a better energy dissipation capacity and seismic resilience. Experiments and finite element analyses were used to study the overall seismic performance of the resilient outrigger and deformation performance of the RBSs under the axial-flexural-shear coupling action, and the design method for the RBSs under this axial-flexural-shear coupling action was established. The seismic design method and details of the resilient outrigger are presented.

A settlement prediction model considering tidal loading and traffic loading of soft soil subgrade

A large number of soft soil subgrade projects have been built in the tidal-flat zone of southeast China. Where, in addition to bearing the traffic loading, the soft soil subgrade may be swallowed up by tidal water. Therefore, the soft soil subgrade will bear long-term coupling action of tidal loading and traffic loading in the tidal-flat zone. Excessive settlement accidents of the subgrade occur frequently in the tidal-flat zone. In this study, a new dynamic constitutive relation considering seepage characteristics was used and the UMAT subroutine was embedded in ABAQUS. FE parametric analysis was analyzed considering three influencing factors of tidal amplitudes, traffic loading amplitude and tidal period. A multi-factor coupling settlement prediction expression considering tidal loading and traffic loading of soft soil subgrade suitable for soft soil subgrade in the tidal-flat zone was proposed. In addition, a settlement prediction program of soft clay subgrade under the combined tidal loading and traffic loading was designed and developed to facilitate engineering use. The research results can be applied to the subgrade projects in the tidal-flat zone, and provide a reference for engineering decision-making and disaster prevention and mitigation.

Fourier regression model predicting train-bridge interactions under wind and wave actions

A train-bridge system crossing a sea can be subjected to extreme environmental conditions such as the concomitant actions of wind and waves, which adversely affect the entire system. This study proposes an approach to evaluate the train-bridge interaction under wind and wave actions. The wind and wave parameters are collected using structural health monitoring (SHM), then correlated using copula models. The wind-bridge, wind-train, and wave-bridge interactions are solved using a real-time co-simulation (RTCS) solution. Besides, this paper introduces a surrogate model named the Fourier regression model (FRM) and Generalized cross-validation (GCV) algorithm to substitute further RTCS calculations. The best solution is obtained by searching for the optimal K value using the GCV algorithm. The results indicate that the dynamic indices of the system are more sensitive when the wind-wave coupling action is considered than when only the wind load is applied. Moreover, the bridge responses for 100 years return period are about 5%∼50% greater than that of 50 years and 25 years return periods. The train responses increase by 7%∼16% compared to the 50 years and 25 years return periods.

Analysis of the Coupling Effect of Thermal and Traffic Loads on Cement Concrete Pavement with Voids Repaired with Polymer Grout

Under the repeated action of traffic and thermal loads, a cement concrete pavement slab may partially lose contact with its base course, and voids may develop underneath the slab. Such distress will greatly impact the pavement performance. To fill the voids and restore the base support to the slab, the technology of polymer grouting has been increasingly adopted in recent years due to its advantages of quick application and high efficiency. There is, however, a lack of research on the mechanistic responses and performance of such a repaired rigid pavement under coupled influences of thermal and traffic loads. Existing literature has mainly focused on normal cement concrete pavement structures (i.e., without polymer grouted voids). This study intends to fill the research gap by investigating the time-domain characteristics of thermal stress response of a cement concrete pavement with underlying voids filled with polymer grout, along with design traffic loads. The finite element method was adopted with a 3-dimensional nonlinear temperature field within the pavement. A program module was developed in the Abaqus FEA software environment for temperature effect analysis. It was found that under the coupling action of thermal and traffic loads, thermal stress had a greater influence on the critical slab stress at the slab corner than those at other slab locations. Through the comparative analysis before and after polymer grouting repair, the critical tensile stress at the slab corner under the vehicle and thermal loads can be effectively reduced. The polymer performance is stable after three years.

Carbonation Characteristics and Bearing Capacity Attenuation of Loaded RC Beam Coupled with Chloride Erosion

The durability of a concrete bridge structure is a systematic problem composed of material, structure, natural environment, and service environment. Various factors are coupled, which affect each other, and single‐factor research cannot fundamentally solve this problem. In this paper, the carbonation characteristics of RC beams with different loading states under the coupling action of carbonation and chloride erosion are studied. Through the experiment, the author tries to find the influence of stress state and chloride ion erosion on the carbonation of concrete and analyze the failure mode and the attenuation rules of the flexural and shearing capacity of the corroded RC beams under the coupling action. For this purpose, five groups of experiments under different working conditions were designed, including chloride ion erosion and carbonation experiments without external load of the cubic blocks, and chloride erosion and carbonation coupling experiments of RC beams under different stress states and stress levels. The carbonation rate of concrete can be reduced by 56%∼60% under the coupling action of chloride salt. Different loading states and stress levels have an obvious influence on carbonation and chloride ion corrosion, which further affects the corrosion rate of steel bars. Under a low corrosion rate, the bending and shear failure modes of the corroded beams are similar to those of the noncorroded beams, and the section strain distribution still approximately conforms to the plane section assumption. The relationship between the relative ultimate shear strength or the relative ultimate flexural strength and the average section‐corrosion rate of the reinforcement is approximately linear.

Perception Action Aware-Based Autonomous Drone Race in a Photorealistic Environment

The development of autonomous, fast, agile small Unmanned Aerial Vehicles (UAVs) brings up fundamental challenges in dynamic environments with fast and agile maneuvers, unreliable state estimation, imperfect sensing, coupling action, and perception in real-time under severe resource constraints. However, autonomous drone racing is a challenging research problem at the intersection of computer vision, planning, state estimation, and control. To bridge this, we propose an approach in the context of autonomous, perception-action aware vision-based drone racing in a photorealistic environment. Our approach integrates a deep convolutional neural network (CNN) with state-of-the-art path planning, state estimation, and control algorithms. The developed deep learning method is based on computer vision approaches to detecting the gates and estimating the flyable area. The planner and controller then use this information to generate a short, minimum-snap trajectory segment and send corresponding motor commands to reach the desired goal. A thorough evaluation of our proposed methodology has been carried out using the Gazebo and FlightGoggles (photorealistic sensor) environments. Extensive experiments demonstrate that the proposed approach outperforms state-of-the-art methods and flies the drone more consistently than many human pilots. Moreover, we demonstrated that our proposed system successfully guided the drone through tight race courses, reaching speeds up to 7m/s of the 2019 AlphaPilot Challenge.

Carbonation Treatment to Repair the Damage of Repeatedly Recycled Coarse Aggregate from Recycled Concrete Suffering from Coupling Action of High Stress and Freeze-Thaw Cycles

Carbonation Treatment to Repair the Damage of Repeatedly Recycled Coarse Aggregate from Recycled Concrete Suffering from Coupling Action of High Stress and Freeze-Thaw Cycles

Study on Strength and Deformation Characteristics of Cemented Gangue Backfill Body Under the Coupling Action of Load and Salt Erosion

Study on Strength and Deformation Characteristics of Cemented Gangue Backfill Body Under the Coupling Action of Load and Salt Erosion

Effect of Soil Salt Content on Stray Current Corrosion of Buried Metal

In order to study the effect of soil salt content on the corrosion of buried metal by the stray current in urban rail transit, a small experimental platform for the buried metal corrosion is built. The corrosion rate and mass loss of buried carbon steel specimens in soil samples with or without DC stray current are measured and calculated when different content of NaCl is added into the soil samples, respectively. The experimental results show that the corrosion rate and mass loss of the buried metal increase with the increase of soil salt content. DC stray current will aggravate the corrosion of the buried metal. The corrosion degree of buried metal will be seriously aggravated under the coupling action of DC stray current and salt. When there is no DC stray curren, the corrosion degree of buried metal is relatively small, and the influence of soil salt content on the buried metal corrosion is also relatively small. Finally, a multiphysics simulation model corresponding to the experiment is established to verify the experimental results. The simulation results are basically consistent with the experimental results, which proves the accuracy of the experimental results. The research results can provide a theoretical basis for the corrosion protection design of subway stray current.

Strength and Microstructure of Cement Paste Under the Coupling Action of Electric Field and Nano-Carbon Black

Strength and Microstructure of Cement Paste Under the Coupling Action of Electric Field and Nano-Carbon Black

The influence of opposite-side high temperature on the frozen behavior of containment concrete under single-side salt freeze-thaw method

In the paper, based on the single-side salt freeze–thaw method and by heating the opposite-side of concrete specimen, the frost resistance of containment concrete under the coupling action of salt freeze–thaw cycles and high temperature was studied. The experimental results indicate within a certain high temperature range, the exfoliation mass per unit area (M) of concrete decreases linearly with the growth of the opposite-sided temperature, while the loss of relative dynamic elastic modulus of concrete decreases slightly with the growth of the opposite-sided temperature; and the thermodynamic simulation also shows the temperature of freeze–thaw surface rises obviously with the opposite-side high temperature due to heat conduction, and the freeze–thaw process is slowed down obviously. In addition, the relative exfoliation mass per unit area (λ) is introduced to assess the frost resistance of concrete under single-side freeze–thaw cycles, and a numerical model between the relative exfoliation mass per unit area (λ) and the high temperature (t) of the opposite side of concrete is constructed. This study provides an idea for the durability of concrete under different temperature environmental conditions.

Interaction between Screw Dislocation and Interfacial Crack in Fine-Grained Piezoelectric Coatings under Steady-State Thermal Loading

The mechanical behavior of fine-grained piezoelectric/substrate structure with screw dislocation and interface edge crack under the coupling action of heat, force and electricity are studied. Using the mapping function method, firstly, the finite area plane is transformed into the right semi-infinite plane, then the expression of the temperature field is given with the help of the complex function, and then the temperature field of the problem is achieved. By constructing the general solution of the governing equation with temperature function, the analytical expression of the image force is derived. Finally, the effects of material parameters, temperature gradient, coating thickness and crack size on image force are analyzed by numerical examples. The results show that the temperature gradient has a very significant effect on the image force, and thicker coating is conducive to the stability of dislocation and interface crack.

Social context facilitates visuomotor synchrony and bonding in children and adults

Interpersonal synchrony is a fundamental part of human social interaction, with known effects on facilitating social bonding. Moving in time with another person facilitates prosocial behaviour, however, it is unknown if the degree of synchronisation predicts the degree of social bonding. Similarly, while people readily fall in synchrony even without being instructed to do so, we do not know whether such spontaneous synchronisation elicits similar prosocial effects as instructed synchronisation. Across two studies, we investigated how context (social vs non-social stimulus) and instruction (instructed vs uninstructed) influenced synchronisation accuracy and bonding with the interaction partner in adults and children. The results revealed improved visuomotor synchrony within a social, compared to non-social, context in adults and children. Children, but not adults, synchronised more accurately when instructed to synchronise than when uninstructed. For both children and adults, synchronisation in a social context elicited stronger social bonding towards an interaction partner as compared to synchronisation in a non-social context. Finally, children’s, but not adults’, degree of synchrony with the partner was significantly associated with their feelings of social closeness. These findings illuminate the interaction of sensorimotor coupling and joint action in social contexts and how these mechanisms facilitate synchronisation ability and social bonding.

Experimental Study on Seepage Characteristics of Fractured Rock Mass under Different Stress Conditions

In order to obtain the mechanical behavior and permeability characteristics of coal under the coupling action of stress and seepage, permeability tests under different confining pressures in the process of deformation and destruction of briquette coal were carried out using the electrohydraulic servo system of rock mechanics. The stress-strain and permeability evolution curves of briquette coal during the whole deformation process were obtained. The mechanical behavior and permeability coefficient evolution response characteristics of briquette coal under stress-seepage coupling are well reflected. Research shows that stress-axial strain curve and the stress-circumferential strain curve have the same change trend, the hoop strain and axial strain effect on the permeability variation law of basic consistent, and the permeability coefficient with the increase of confining pressure and decreases, and the higher the confining pressure, the lower the permeability coefficient, the confining pressure increases rate under the same conditions, and the permeability coefficient corresponding to high confining pressure is far less than that corresponding to low confining pressure. The confining pressure influences the permeability of the briquette by affecting its dilatancy behavior. With the increase of the confining pressure, the permeability of the sample decreases, and the permeability coefficient decreases with the increase of the confining pressure at the initial stage, showing a logarithmic function. After failure, briquette samples show a power function change rule, and the greater the confining pressure is, the more obvious the permeability coefficient decreases.

Characteristics of embedded triple screw pump based on thermal-fluid-structure coupling

To accommodate special applications where installation space is limited and noise and vibration requirements are high, a new triple screw pump structure was proposed, which was integrated into a servo motor. The design optimizes the profile of the master and slave screws of the embedded triple screw pump. The temperature and pressure fields of the embedded triple screw pump, as well as the heat transfer and pressure distribution between the fluid in the pump and the screw, were investigated through a thermal-fluid-structure approach. The deformation and stresses of the screw were compared for three operating conditions: temperature loading, pressure loading, and thermal-fluid-structure coupling. The results show that the deformation and stresses in the screw tended to increase with increasing pressure and temperature and the pressure load caused more significant deformation and stresses in the screw than the temperature load. The screw deformation caused by pressure loading was found to be the main factor affecting the thermal-fluid-structure coupling. The screw deformation after coupling was smaller than the sum of the screw deformation caused by individual temperature and pressure loads, and the stress values were the same. The results indicate that the coupling action weakens the deformation and stresses in the master and slave screws.

Separation characteristics and structure optimization of double spherical tangent double-field coupling demulsifier

The demulsification and dewatering of the W/O emulsion are widely used in petrochemical industry, oilfield exploitation, and resource and environmental engineering. However, efficiently treating emulsion via traditional single methods. In this study, a new double-field coupling demulsification and dewatering device is proposed, where the conical structure of the device is double spherical tangential type. The numerical model for double-field coupling is established, especially, the population balance model (PBM) is used to simulate the coalescence and breakup of dispersed droplets under the double-field coupling action. And the effects of three conical structures on the internal flow and separation efficiency are analyzed. Results show that the conical structure has a significant effect on the coalescence of droplets, especially the double spherical tangential cone is more conducive for improving the coalescence ability of small droplets and improving the separation efficiency of the device. After optimization, the optimal R value of the double spherical tangential coupling device is 300 mm, and the separation efficiency can be up to 96.32%, which is 6.13% higher than the separation efficiency of the straight double-cone coupling device.

Study on stud performance of steel UHPC composite structure based on temperature

The stress and deformation of the specimen under static load and temperature load coupling are deduced by simulation. With the help of finite element software ABAQUS, the user subroutines DFLUX and FILM are called to introduce the temperature field, so as to realize the analysis and Research on the stress, displacement, PEEQ, arrangement and load slip curve of the stud under different action conditions. The results show that based on the existence of temperature stress, the service performance of studs under coupling action is significantly lower than that under static action alone, and the proportion of shear performance of studs in different rows is different. Through the research and analysis of the above phenomena, it can provide reference value for the research of temperature on the performance of studs in composite bridge deck and prolong the service life of bridge deck.

Hysteretic behavior of the hybrid coupled partially encased composite wall system

In order to investigate the seismic behavior of the hybrid coupled partially encased composite (PEC) wall system, two 2/3-scale three-story specimens with different elastic coupling ratios (CRelastic) were tested under cyclic loading. The results showed that the hysteretic curves of the two specimens were full and stable, indicating their robust cyclic performance and excellent energy dissipation capacity. Under reversed cyclic lateral loading, the specimens exhibited a two-stage yielding energy dissipation mechanism, in accordance with theoretical expectations. Both specimens dissipated a large amount of energy during loading, with the equivalent viscous damping ξeq reaching 0.32 and 0.35 at the maximum displacement level, respectively. Based on the experimental results, the refined finite element model for the hybrid coupled PEC wall was established in ABAQUS and validated. A parametric analysis demonstrated that the CRelastic and the design axial compression ratio (n) had significant influences on the seismic behavior of the hybrid coupled PEC wall. With increasing CRelastic, the lateral stiffness, strength, and yield displacement of the hybrid coupled PEC wall gradually increased, while its ductility deteriorated. Moreover, the ductility of the hybrid coupled PEC wall decreased with increasing n owing to the strong coupling action of the steel coupling beams. In order to ensure the good seismic performance and form a reasonable failure mode, the CRelastic and n in the hybrid coupled PEC wall should not exceed 65% and 0.5, respectively.