Particle Migration Research Articles

Microwave pyrolysis-engineered MOFs derivatives for efficient preferential CO oxidation in H2-rich stream

Microwave pyrolysis inherited the molecular-level engineering design of the CuCe-MOF: The tandem microwave pyrolysis firstly carbonized them to CuCe/C with topological structure, and improved the microwave absorption of MOFs in nitrogen atmosphere. Subsequently, CuCeO x catalyst was synthesized by its self-heating source of microwave in air, which endowed with molecular-level dispersed active sites to enhance preferential CO oxidation in H 2 -rich stream. • MOFs derivatives are achieved via tandem microwave pyrolysis. • Microwave pyrolysis inhibits the agglomeration of metal nanoclusters. • The tandem strategy solves the problem of poor microwave adsorption of MOFs. • Ligand carbonization provides dispersed heating sources by enhancing microwave absorption. • Microwave pyrolysis-engineered CuCeO x exhibits an outstanding performance of preferential CO oxidation. The versatile metal–organic framework (MOF) derivatives are achieved via microwave pyrolysis. The dipole vibration thermogenesis of molecules by microwave pyrolysis overcomes the issues of high energy consumption, slow heating rate, unregulated at the molecular-level, metal nanoclusters particles migration and coalescence caused by traditional thermal pyrolysis. For solving the poor microwave absorption of MOFs, a tandem microwave pyrolysis strategy is employed herein. Ligand carbonization enhances the conduction loss of microwaves and becomes a highly dispersed microwave heating source, which effectively inhibits the agglomeration. The CuCeO x catalysts obtained through this strategy retain the merits of bimetallic CuCe-MOFs with highly dispersed active species, and exhibit outstanding catalytic activities with the 100% conversion of CO being achieved at 75 °C for the preferential CO oxidation in H 2 -rich stream. These results demonstrate that the microwave pyrolysis-engineered MOFs uniformity has established catalyst with highly dispersed active species.

Lateral migration of cylindrical particle in a constricted microchannel—A numerical study

AbstractInertial migration of a single cylindrical particle in a constricted microchannel is addressed in this work. A computational model (two‐dimensional) has been constructed with the assistance of the immersed boundary finite volume method. The feedback forcing strategy is utilized for the simulation of lateral migration. The parameters like equilibrium position, migration time, and shortest equilibrium distance are computed to analyze the inertial migration characteristics of the particle. Also, a comprehensive parametric study has been performed on the migration behaviour of particles inside the constricted channel by addressing the effects of Reynolds number, diameter, initial release position, and constriction clearance. The parametric study shows that the equilibrium position changes with variations in the initial release position and particle diameter. On the other hand, it stays unaffected by changes in Reynolds number and constriction clearance. The parameters like the shortest equilibrium distance and migration time increase with a rise in Reynolds number and particle diameter. On the other hand, it reduces with the reduction in constriction clearance. Inspired by the parametric study results, in the following stage, a prediction model is created with an artificial neural network algorithm. This is used for an effective forecast of equilibrium position, migration time, and shortest equilibrium distance. Further, the computational model is utilized to check for the existence of a critical Reynolds number for the particle movement in a constricted microchannel. It is observed that the critical Reynolds number remains unchanged with a change in particle diameter. However, it increases linearly with an increase in constriction clearance.

A Numerical Analysis of the Leakage Characteristics of an Embankment Dam Slope With Internal Erosion

Leakage is a common defect of embankment dam slopes, and is usually accompanied by internal erosion. This study establishes a mathematical two-phase seepage coupling model that explicitly considers the effects of internal erosion. With the help of finite element software COMSOL Multiphysics®, we use this model to study the characteristics of fluid seepage, the fraction of leakage volume that is made up of migrated fine particles (migrated fine particles volume fraction), porosity, permeability, and displacement in the leakage process of a three-dimensional embankment dam slope, as well as to study the influence of the water level and leakage outlet size on the aforementioned features. Our results show that water seepage velocity gradually increases with time, especially at the downstream leakage outlet. Therefore, the erosion and migration of fine particles occur primarily at the downstream leakage outlet, resulting in a significant increase in the migrated fine particles volume fraction, porosity, and permeability. In addition, the maximum migrated fine particles volume fraction, the maximum porosity, and the maximum permeability in the slope increase nonlinearly with time. Curves for maximum displacement with a strength reduction factor can be divided into three stages: the early stable stage, the midterm nonlinear growth stage (creeping state), and the later rapid growth stage (instability state). We also find that the rise of the water level promotes the erosion and migration of fine particles on the slope and that the maximum migrated fine particles volume fraction and the maximum porosity increase with the water level. The values of the strength reduction factor for the creeping state decrease as the water level rises. Furthermore, the larger the size of the downstream leakage outlet, the larger the maximum migrated fine particles volume fraction and maximum porosity. However, the relationship between maximum displacement and strength reduction factor is nearly unaffected by the size of the leakage outlet.

Experimental Evaluation of the Multiphase Flow Effect on Sand Production Process: Prepack Sand Retention Testing Results

This paper considers a field with high-viscosity oil in a terrigenous weakly consolidated reservoir (sandstone) with a massive gas cap and an aquifer. The major challenge in the field operation is the migration of solid sand particles into the well, accompanied by a breakthrough of water and/or gas. The goal of the investigation was to evaluate the degree of influence on the sanding process of water and gas shares in the produced fluid and to determine the effect of pressure drop. The research methodology is based on a series of filtration experiments on small-sized bulk reservoir models. Particle size distribution of bulk models was created in accordance with that of the reservoir. The experiments were made in the form of Prepack Sand Retention Tests (SRT). Gas breakthrough allows sand production on a relatively high level for a longer amount of time, even though the concentration of solids in the produced fluid is lower than that of water breakthrough. On the other hand, water breakthrough triggers higher sand production, but it rapidly decreases as time goes on. Retained permeability of the model-screen system from the drawdown pressure (pressure gradient) and phase distribution of the flow were investigated. Moreover, a methodology has been developed for conducting filtration tests on bulk reservoir models to evaluate the efficiency of different screens (wire-wrapped screens, in particular).

Fully resolved simulations of viscoelastic suspensions by an efficient immersed boundary-lattice Boltzmann method

An efficient immersed boundary-lattice Boltzmann method (IB-LBM) is proposed for fully resolved simulations of suspended solid particles in viscoelastic flows. Stress LBM based on Giesekus and Oldroyd-B constitutive equation are used to model the viscoelastic stress tensor. A boundary thickening-based direct forcing IB method is adopted to solve the particle–fluid interactions with high accuracy for non-slip boundary conditions. A universal law is proposed to determine the diffusivity constant in a viscoelastic LBM model to balance the numerical accuracy and stability over a wide range of computational parameters. An asynchronous calculation strategy is adopted to further improve the computing efficiency. The method was firstly applicated to the simulation of sedimentation of a single particle and a pair of particles after good validations in cases of the flow past a fixed cylinder and particle migration in a Couette flow against FEM and FVM methods. The determination of the asynchronous calculation strategy and the effect of viscoelastic stress distribution on the settling behaviors of one and two particles are revealed. Subsequently, 504 particles settling in a closed cavity was simulated and the phenomenon that the viscoelastic stress stabilizing the Rayleigh–Taylor instabilities was observed. At last, simulations of a dense flow involving 11001 particles, the largest number of particles to date, were performed to investigate the instability behavior induced by elastic effect under hydrodynamic interactions in a viscoelastic fluid. The elasticity-induced ordering of the particle structures and fluid bubble structures in this dense flow is revealed for the first time. These simulations demonstrate the capability and prospects of the present method for aid in understanding the complex behaviors of viscoelastic particle suspensions.

Multiscale modeling of seepage-induced suffusion and slope failure using a coupled FEM–DEM approach

Suffusion refers to the detachment and migration of fine particles through voids among coarse particles and is one of the major causes of slope failure. This study investigates the seepage-induced suffusion and slope instability using a hierarchical multiscale finite–discrete element method (FEM–DEM). An erosion law with the critical hydraulic gradient for the onset of suffusion is proposed. Two examples, including one-dimensional suffusion and biaxial compression tests, are performed to verify the proposed scheme. Emphases are placed on reproducing suffusion and progressive slope failure process under seepage flow. The results indicate that a shear band is initiated from the slope toe and gradually extends to the crest. The increase of erosion rate accelerates the process of suffusion and slope failure, whereas a higher critical hydraulic gradient plays an opposite role. In addition, fines loss caused by suffusion occurs mainly on the slope surface, especially near the slope toe. Microscopic analyses on locally embedded representative volume elements (RVEs) indicate that RVEs inside the shear band experience severe deformation and microstructural changes, manifested by the rearrangement of soil skeletons and variation of contact force chains.

Experiment and numerical simulation on the fine particle migration behaviors for the collection efficiency enhancement of a wire-plate electrostatic precipitator in pig house

In this paper, an integrated numerical model is presented and validated to investigate the particle charging and migration behaviors in a wire-plate electrostatic precipitator (ESP) for the collection efficiency (η) enhancement of the ESP in the piggery. Calculations of the RNG k-ε model, corona model, and particle tracking model are coupled in our model by utilizing MATLAB and COMSOL Multiphysics. This model is used to investigate the influence of various factors, such as the particle diameter (dp), flow velocity (u), and applied voltage (V), on the performance of ESP. Simultaneously, a visual experimental platform for PM2.5 migration is established for verification. The calculated results show that the predicted values of potential distribution, u distribution, and η are in good agreement with the previously reported experimental data. Moreover, the calculated results indicate that two elliptical shapes are produced by a relatively high electric potential and space charge density in the surrounding of the discharge corona wires. Furthermore, η first decreases with the increase of dp, remains unchanged in the range of 0.1–1.0 μm, and then increases until became constant in the range of 1.0–10 μm, revealing the interaction between diffusion charging, electric field charge, and fluid drag. In addition, the experimental and calculation results indicate that the η of PM2.5 increases with the decrease of u and increase of V. Notably, η of 2.0 μm is 100% at u = 1 m/s, V = 50 kV. Therefore, both the migration behavior solution method and the rules of η dependence on PM2.5 provide a scientific parameter control method for improving the air quality in pig house.

A novel approach for pore-scale study of fines migration mechanism in porous media

The migration of fine particles in oil reservoir rock is the most important cause of formation damage and permeability impairment. The mechanism of this phenomenon includes fines detachment, mobilization, agglomeration, and re-attachment, which lead to throat clogging and/or blocking. Therefore, accurate modeling of this complex mechanism requires a model with high solver efficiency.In this work, based on the physical features of fines migration in pore throat, the conventional DPM model of ANSYS FLUENT software was initially modified by UDF code. Then, predetermined scenarios of suspension injection into a two dimensional (2D) microchannel were simulated for predicting pressure drop as a function of injected pore volume using the modified DPM model. Next, based on these simulation results, a proxy model using the artificial neural network (ANN) was developed for computational cost reduction of fines migration modeling in the microchannel (pore throat). Secondly, a dual pore scale numerical model by combination of proxy model and pore network modeling approach was developed to predict pressure drop as well as permeability impairment in a network of microchannels (porous media). Moreover, for rapid computation of pressure drop in the network model, a meta-heuristic method of rain optimization algorithm (ROA) has been used. Finally, for model validation, a series of laboratory tests including suspension injections into the glass micromodels were conducted.A comparison of simulation results using both proxy model and dual pore scale model with experimental data shows a good agreement and according to the obtained results, a decrease in the particles mean size, and Reynolds number as well as increase in particles concentration lead to increase in pressure drop and permeability reduction. On the other hand, use of a proxy model based on artificial neural network and a meta-heuristic method of rain optimization algorithm lead to significant computational cost reduction, while the accuracy of fines migration modeling is high enough. Hence, using our modeling approach for fines migration study in porous media as an accurate and fast computational tool can help for a better understanding of this phenomenon, which is very important in the petroleum industry.

Up-to-Date Procedures in Female Stress Urinary Incontinence Surgery: A Concise Review on Bulking Agents Procedures.

To avoid complications related to mid-urethral slings (MUS), alternative procedures to treat stress urinary incontinence (SUI), such as urethral bulking agents (UBAs) have been adopted. The aim of this review is to narratively report the efficacy and safety of UBAs for SUI treatment. For this review, research from PubMed and EMBASE was performed to evaluate relevant studies that were undertaken from January 2012 to January 2022. Nineteen prospective studies were included. Several definitions of subjective and objective success were adopted. At a follow-up of <24 months, significant improvement was widely observed, even if with a heterogeneous rate of success between 32.7–90%, and a reinjection rate of 8.3–77.3%. Compared with other procedures, MUS resulted as significantly superior to UBAs but was balanced by a higher complication rate. Acute urinary retention, urinary tract infection and de novo urgency, and other complications, such as injection site rupture, urethral erosion and particle migration have been described after UBAs. SUI after UBAs treatment resulted in improvements in all studies and can be considered a safe and effective option to treat SUI. However, homogenous and longer-term data lack, limiting general recommendations. Thus, larger RCTs evaluating long-term effects are required.

Experimental studies on suction-assisted installation of the modified suction caisson in dense sand

The modified suction caisson (MSC) consists of an internal compartment (IC) and an external structure (ES), being an innovative foundation for offshore structures. Penetration of the MSC into the desired position under the combination of the self-weight and applied suction is an issue for design. Model tests were performed on the MSC in saturated dense fine sand to explore the installation behavior of the MSC. Results show that the optimal method of penetrating the MSC (i.e., the maximum penetration is obtained) is only pumping out the air and water encased in the IC. During suction-assisted installation, subsidence regions around the IC and ES were found. The sand particles in the subsidence regions were found to move downwards along the external walls of the IC and ES. The length of sand particles migration path along the IC is higher than that along the ES, indicating that seepage effect in sand outside the IC is stronger than that outside the ES. Installation mechanisms under various installation methods were elaborated by analyzing the seepage distribution in sand around the MSC. Based on the method proposed by Houlsby and Byrne, modified equations of estimating the required suction of MSC were proposed. The research can provide guidance for the MSC installation design.

Shear-induced migration in concentrated suspensions: Particle mass conservation, contact pressure and jamming

A two-velocity fluid model is presented to describe particle migration in mono-disperse suspensions of neutrally buoyant particles. In contrast to previous migration models, the proposed formulation allows us to impose explicit boundary conditions on particle velocity, and thereby to satisfy strict mass conservation for the particle phase. In addition, the upper bound on particle volume fraction (jamming limit) is strictly enforced through a non-smooth complementarity condition and the introduction of a particle jamming pressure. The model is applied to an axisymmetric Poiseuille flow and solved using a finite-element method. For that purpose, a specific, fully implicit algorithm based on non-smooth optimisation tools is developed and validated. Preliminary comparisons with experimental data from the literature show promising agreement. In particular, the model properly captures the formation of an inner plug region, in which the suspension is saturated and jammed. • New particle migration model for suspension. • Strict mass conservation for each phase. • Two-velocity description. • Jamming via non-smooth complementarity condition.

Automatic ECG analysis system with hybrid optimization algorithm based feature selection and classifier

Cardio vascular disease threatens human life with higher mortality rate. Therefore it is quite important to monitor. An arrhythmia is an abnormal heart beat and rhythm which causes the disease. The best tool to find the heart rhythm of heart is Electro Cardiogram (ECG) which provides information about the different types of arrhythmias. This paper aims at proposing an automatic framework by employing multi-domain features to classify ECG signals. Proposed work uses optimum method of feature selection to improvise the efficiency of the classification process. A hybrid optimization algorithm is used for feature selection and proposed to optimize the parameters of the existing Support Vector Machine (SVM) classifier. Proposed hybrid optimization algorithm was developed using Particle Swarm Optimization (PSO) and Migration Modified Biogeography Based Optimization (MMBBO) algorithm. Algorithm provides an improved solution to the optimizing the parameters of ECG signals. Results are evaluated by implementing in MATLAB software and the performance is justified with comparative analysis. The proposed framework enhances the process of automatic prediction of various arrhythmias or rhythm abnormalities which performs in gaining better accuracy. For data sets, the average classification accuracy of this method is 97.89%. This result is an improvement of 4–5% over the comparison of other methods.

Continuous organelle separation in an insulator-based dielectrophoretic device.

Heterogeneity in organelle size has been associated with devastating human maladies such as neurodegenerative diseases or cancer. Therefore, assessing the size-based subpopulation of organelles is imperative to understand the biomolecular foundations of these diseases. Here, we demonstrated a ratchet migration mechanism using insulator-based dielectrophoresis in conjunction with a continuous flow component that allows the size-based separation of submicrometer particles. The ratchet mechanism was realized in a microfluidic device exhibiting an array of insulating posts, tailoring electrokinetic and dielectrophoretic transport. A numerical model was developed to elucidate the particle migration and the size-based separation in various conditions. Experimentally, the size-based separation of a mixture of polystyrene beads (0.28 and 0.87 m) was accomplished demonstrating good agreement with the numerical model. Furthermore, the size-based separation of mitochondria was investigated using a mitochondria mixture isolated from HepG2 cells and HepG2 cells carrying the gene Mfn-1 knocked out, indicating distinct size-related migration behavior. With the presented continuous flow separation device, larger amounts of fractionated organelles can be collected in the future allowing access to the biomolecular signature of mitochondria subpopulations differing in size.

Lattice Boltzmann simulation of particles inertial migration with slippery surface and moderate concentration in circular tube flow

Hydrodynamic migration of spherical slippery particles suspended in a cylindrical channel flow is numerically studied in this paper. The effects of the particle concentration of particle ([Formula: see text], tube-to-particle diameter ratio ([Formula: see text] and Knudsen number (Kn), respectively, with ranges of [Formula: see text] and [Formula: see text] with the channel Reynolds number of [Formula: see text], are concerned in the simulations. The objective of this work is to explore the pipeline transportation of relatively large and moderately dense particles with slippery surface, for which the characteristics have not been comprehensively exhibited in the literature. Such particle-resolved suspension flow is solved by a three-dimensional lattice Boltzmann method, where a curved kinetic boundary condition is adopted to resolve the velocity slip phenomenon at the fluid-particle interface, and the particle-particle collision is performed by a repulsive force model. The results elucidate that the effect of particle focusing is less marked at intermediate concentrations. At larger [Formula: see text], some particles may migrate to the center of channel due to the aggravation of the mutual collision. The increase of Re contributes to the particle focusing at low [Formula: see text], but not for the case of higher [Formula: see text]. On the other hand, the [Formula: see text] generally has a negative effect on the inertial focusing. Furthermore, the migration velocity of particles reduces and the behavior of inertial focusing is enhanced simultaneously, with the increase of Kn.

Dynamic interplay between metal nanoparticles and oxide support under redox conditions.

The dynamic interactions between noble metal particles and reducible metal-oxide supports can depend on redox reactions with ambient gases. Transmission electron microscopy revealed that the strong metal-support interaction (SMSI)-induced encapsulation of platinum particles on titania observed under reducing conditions is lost once the system is exposed to a redox-reactive environment containing oxygen and hydrogen at a total pressure of ~1 bar. Destabilization of the metal-oxide interface and redox-mediated reconstructions of titania lead to particle dynamics and directed particle migration that depend on nanoparticle orientation. A static encapsulated SMSI state was reestablished when switching back to purely oxidizing conditions. This work highlights the difference between reactive and nonreactive states and demonstrates that manifestations of the metal-support interaction strongly depend on the chemical environment.

Effects of particle morphology on the shear response of granular soils by discrete element method and 3D printing technology

AbstractThe development of quantitative correlation between particle morphology and shear responses of granular soils is an ongoing challenge. Herein, 3D printing technology, combined with the experiments and discrete element simulations were conducted to study the effects of different particle shapes on the particle migration, the development of shear zone, and the anisotropy of particle contact during shearing. Both numerical simulations and experimental tests confirmed that the increase of modified shape parameterShstrengthens the interlock between particles, which in turn limits the shear deformation in the direction of shearing. As the shear load increases further, the rotation of particles begins to develop from both sides of the shear box boundary, which gradually expands to the center, and finally forms a stable disturbance region in the center of the specimen; meanwhile, the positions of the maximum particle rotation appear at the center and boundary of the shear zone. Moreover, particle shape does not affect the distribution of fabric anisotropy before loading, however, the change of particle shape parameterShmakes the fabric anisotropy become prominent. In addition, particle shape is found to improve the shear resistance by changing the number and distribution of contacts between particles, rather than the contact force among particles.

Thermodynamic evaluation and particle migration of hybrid nanofluids flowing through a complex microchannel with porous fins

A compound method is established by adding Al2O3-TiO2/Water (W) nanofluids and porous media in a microchannel to reduce pressure drop and enhance heat transfer in the limited heat dissipated area. Effects of porosity and hybrid nanofluids are numerically investigated in the laminar region. Pressure drop, Nusselt number, velocity and temperature fields are used as indicators to evaluate the characteristics of flow and heat transfer. Furthermore, the analytical methods including thermodynamic evaluation and nanoparticle migration were performed to reveal the essential mechanism of heat transfer enhancement. Compared with non-porous microchannels, the maximum reduction of porous microchannels is 9.73% (ε = 0.5), 8.3% (ε = 0.6) and 6.8% (ε = 0.7) for pressure drop, while the maximum agument is 23.53% (ε = 0.5), 20.59% (ε = 0.6) and 16.67% (ε = 0.7) for Nusselt number. The permeability of fluid reduces pressure drop and enhances heat transfer in the porous region. The maximum heat transfer irreversibility reduces up to 64%, and exergy efficiency reaches 88% by adding nanofluids and porous media. Nanoparticle migration originating from thermophoresis affects the concentration distribution near the wall, and cold-hot fluids fully mix in the porous region, thereby increasing heat transfer. The effect of thermophoretic diffusion of dilute nanofluids in micro-scale convective heat transfer is higher than that in the macro-scale one.

Determining trigger factors of soil mass failure in a hollow: A study based in the Sichuan Province, China

Soil mass failure disasters are among the most destructive disasters in mountainous areas worldwide, and they continue to receive significant attention in the literature. However, factors that influence soil mass failure in hollows have not been explored via experimental approaches. In this study, we conducted a series of indoor hollow–flume experiments to exhibit how the three factors, namely, initial moisture content, slope angle, and clay content, influence the collapse of soil mass under surface runoff conditions. Our findings revealed that the major processes causing soil mass failure were internal seepage erosion resulting from subsurface runoff, migration of fine particles, development of tension cracks, increase in pore water pressure, and decrease in cohesion. Fluctuations in pore water pressure were characterized by two main trends: (1) an abrupt rise under static liquefaction and (2) a decrease before failure due to dilatancy. The time required for soil mass failure first decreased and then increased with the increase in moisture content. The soil mass with an initial moisture content of ∼12.5% was more critical to the failure. In addition, the time required for soil mass failure decreased with increasing slope angle, revealing a slope angle of 40° to be more prone to failure. The buildup of pore water pressure was found to increase with clay content; soil with a clay content of ∼7.5% required the shortest amount of time to initiate slides. Thus, our results provide a thorough insight into the processes and factors involved in the initiation and development of soil mass failure in hollow areas, which can be used by public agencies to improve monitoring, early warning, and forecasting systems. Notably, our study can help identify risk-prone source areas, and sensors can be installed to monitor potential mass failure locations.

Sorption-enhanced glycerol steam reforming over hierarchical hollow Ni-CaO-Ca12Al14O33 bi-functional catalyst derived from hydrotalcite-like compounds

Hydrogen production with in situ CO2 capture by the sorption-enhanced steam reforming (SESR) technology is a promising concept to reduce anthropogenic CO2 emissions. However, its practical applicability is limited by rapid, sintering-induced cyclic performance decay at high reaction rate and decarbonation temperatures. Here, we design a highly stable bi-functional catalyst with a surface spatial confinement strategy. The bi-functional catalyst has a hierarchical hollow microsphere structure, in which the shell is composed of layered metal oxides. The sintering resistance of Ca and Ni species is found to arise from the surface spatial confinement effect in which the aggregation and migration of Ni and CaO particles are suppressed by the layers. High stability for SESRG reaction with only 35% loss of sorption enhancement effect is observed after 20 cycles of repeated SESEG-decarbonation, during which H2 purity is maintained at 99%. The result shed light on the design of the stable bi-functional catalysts in the SESR reaction.

Research on permeable pores in collapse column fillings with different gradation structures

Particle loss is an important cause of water inrush catastrophes in collapsed columns. In order to study the relationship between the lost particles of different graded rock samples and the pore structure of the subsidence column filling, experiments were designed and the changes of the seepage parameters of graded rock samples during the particle migration process under different permeable water pressures P and axial loads F were determined. The results show that: (1) There will be obvious collapse, silting and particle loss behaviors in the sample during different loading processes, and the rock samples with gradation values of n = 0.3 and n = 0.5 are dominant; (2) The relationship between porosity φ and bearing pressure The exponential function can be used to fit the loads F well, and the porosity decreases with the increase of the bearing load. The water surging characteristics before and after 1.2 MPa are mainly in the turbulent water gushing stage, accompanied by instantaneous slurry. Possibility of splashing and indenter sliding; (3) After infiltration, the condition of the remaining skeleton rock samples in the cylinder generally shows a trend of first decreasing rapidly, then increasing slowly, and then decreasing; (4) The gradation value n of the sample and the bottom There is a good correlation between the damaged area and the mean value S of the maximum area of the top water inrush channel. The maximum area increase of the damaged area and the maximum area increase of the water inrush channel show an opposite trend. The permeable pores of the graded samples can be divided into There are three situations of digging and collapse, water inrush gap and scouring hole, and the pore seepage process can be divided into 4 stages of inoculation of water seepage, rapid adjustment, rapid scour and steady flow.