Propagation Radius Research Articles

Patterns of Changes in the Mechanical and Filtration Properties of Semi-Rock Soils Modified by Jet Cementation

When installing underground structures in soil layers with high groundwater filtration rates, special requirements are imposed on the material of anti-filtration curtains. The conditions of application of jet cementation technology for modification of watered fractured rocky soils of low strength in order to form a composite material with the required mechanical and filtration characteristics are considered.The technological parameters of the cementation process have been experimentally and theoretically determined to ensure the necessary radius of propagation of the bonding mixture, and methods of laboratory and field control of the modified zone have been developed. The maximum permissible values of the controlled parameters have been determined.

Experimental and numerical studies of the effects of micro/nano carbon fibers in the dynamic behavior of cement-based grouting materials for reinforcement of sand layers

Geological hazards of sand layers pose a serious threat to engineering safety. Grouting reinforcement technology is widely used in such conditions due to its convenience, economy, and effectiveness. To explore the reinforcement effect of carbon fiber (CF) modified cement-based grouting materials on sand layers, grouting solidified bodies (GSB) with CF contents of 0.0%, 0.5%, 1.0%, and 1.5% are selected for Split Hopkinson Pressure Bar (SHPB) impact tests, scanning electron microscope (SEM) scanning, and numerical simulation experiments. The mechanical properties of specimens under dynamic impact conditions and the reinforcement mechanism of CF are studied. Results show that GSB is a strain-rate-dependent material. With the increase of impact rate, peak stress, incident energy, transmitted energy, and dissipated energy of specimens gradually increase, while the integrity of specimens decreases. The CF content remarkably affects the mechanical properties of specimens. When the impact rate is constant, with the increase of CF content, the peak stress and transmitted energy of specimens show a decreasing–increasing– decreasing trend, and the performance of CF-1.0% specimens is optimal. The cement matrix is the main energy storage and release medium, accounting for 97.66% of the energy. When damaged, the cement matrix is mainly fractured. At the microcrack tip, CF influences the direction of crack propagation, reducing the radius of crack propagation, and the main failure mode of CF is debonding. CF can substantially improve the mechanical properties of specimens and reduce the number of cracks. Compared with CF-0.0%-cementitious material (CM) specimens, the peak stress of CF-1.0%-CM specimens is increased by 19.98%. The magnitude of CF force is related to the angle between crack and CF. As the angle increases from 0° to 90°, the CF force gradually increases, reaching the maximum at 90°, with an increase of 133.82%. At this angle, the anti-cracking effect of CF is most substantial. The research results can provide technical support for sand layer grouting reinforcement technology.

Calculating the number of radial cracks around a wellbore fractured by liquid CO2 phase transition blasting technology

Integrating liquid CO2 phase transition blasting (LCPTB) technology with hydraulic fracturing (HF) methods can help reduce wellbore damage, create multiple radial fractures, and establish a complex fracture network. This approach significantly increases the recovery efficiency of low-permeability oil and gas fields. Accurately calculating the number of fractures caused by LCPTB is necessary to predict production enhancement effects and optimize subsequent HF designs. However, few studies are reported on large-scale physical model experiments in terms of a method for calculating the number of fractures. This study analyzed the initiation and propagation of cracks under LCPTB, derived a calculation formula for crack propagation radius under stress waves, and then proposed a new, fast, and accurate method for calculating the number of fractures using the principle of mass conservation. Through ten rock-breaking tests using LCPTB, the study confirmed the effectiveness of the proposed calculation approach and elucidated the variation rule of explosion pressure, rock-breaking scenario, and the impact of varying parameters on number of fractures. The results show that the new calculation method is suitable for fracturing technologies with high pressure rates. Recommendations include enlarging the diameter of the fracturing tube and increasing the liquid CO2 mass in the tube to enhance fracture effectiveness. Moreover, the method can be applied to other fracturing technologies, such as explosive fracturing (EF) within HF formations, indicating its broader applicability and potential impact on optimizing unconventional resource extraction technologies.

Calculation method of spherically expanding flame propagation radius to consider ignition electrode effects

Ignition electrodes have an immense impact on the accurate measurement of the flame propagation spherical radius. In this study, a flame-radius calculation method is designed. The method is able to eliminate effects due to the ignition electrodes. The adaptability and optimization effects of the proposed method are analyzed. The results show that the ratio of the angle is affected by the ignition electrodes under the Han II method. There are three obvious divisions include a high-value area, a sharp-variation area, and a mild-variation area. The ratio of the angle affected by the ignition electrodes is only applicable to the mild-variation region when the flame presents respective convex and concave distributions. For these distributions, the increment rate of the mean radius is 0.4–0.85% and 0.42–3.19%. The reduced rate of the standard deviation of the radius extraction value is 11.91–22.1% and 5.13–17.99%, and the reduced rate of the radius extraction value range is 20.32–39.51% and 0.32–8.09%.

Dynamic coupling model of FDS and cellular automata considering trampling behavior

Fire accidents usually cause large casualties. In this paper, a fire evacuation model based on the dynamic coupling of FDS and CA, which dynamically couples disaster data and evacuation behavior, is designed to reflect the impact of disaster factors on the pedestrian evacuation process in real-time. Furthermore, pedestrians are divided into two categories, one type of pedestrians will choose to move against the wall to reduce the risk of stampede accidents, and the other type of pedestrian will evacuate to the exit according to the normal movement method. And considering the role of information transmission between pedestrians, the two types of pedestrians will transform into each other. In addition, the concept of pedestrian crowding, support, and friction is introduced and viewed as an influencing factor of normal pedestrian falls. Set the panic value as the influencing factor of the efficiency of pedestrian information transmission and the death probability of downed pedestrians. The impact of pedestrian density, pedestrian walking behavior towards walls, evacuation response time, information propagation radius, heat release rate of the fire source, and the interference of smoke on the pedestrians' visibility range on evacuation outcomes has been discussed through numerical simulations. The analysis shows that although the presence of pedestrians walking against the wall will slightly increase the evacuation time, when the available evacuation time allows, the risk of a stampede will be greatly reduced; The increase in evacuation response time will aggravate the panic psychology of pedestrians and increase the risk of stampede accidents; The increase of the pedestrian information transmission radius will reduce the risk of a stampede, and the effect is more obvious when the pedestrian density is smaller; Selecting building materials with lower heat release rates can effectively reduce the risk of fire incidents; The restriction of visibility range by smoke seriously endangers pedestrian safety and reduces the efficiency of evacuation.Our research results can play a reference and guide for future building disaster prevention design and public safety research.

Study on direct initiation process and initiation mechanism of acetylene/oxygen premixed gas detonation

Studying the process and mechanism of direct initiation of gas detonation is the basis for preventing serious gas explosion disasters and developing detonation propulsion power devices. This article utilizes a combustible gas combustion and explosion experimental system to achieve direct spherical acetylene/oxygen mixture detonation through a high-energy ignition system. The detonation velocity and flame structure evolution process in direct detonation were studied through schlieren images, and a critical detonation model was established to explain the direct detonation process. The critical detonation wave velocity for direct detonation was determined to be half of the CJ detonation velocity. Revealed the mechanism of detonation cell formation during the direct initiation process. The basic criterion for achieving direct initiation of spherical detonation has been obtained: to achieve direct detonation, when the overdrive detonation wave formed by the detonation source attenuates to half the detonation velocity of CJ, the propagation radius must not be less than a full detonation cell size. This article conducts in-depth research on the direct initiation process of acetylene/oxygen mixture detonation. The results obtained have essential value for developing and applying the detonation theory of acetylene fuel. At the same time, they have important practical significance for preventing gas fire and explosion accidents.

Effects of TiMoTa nano-crystalline interlayer on nucleation, adhesion and tribological behaviors of diamond coating

To investigate the influence of the transition layer on diamond nucleation and growth, the TiMoTa multi-alloy interlayers were firstly prepared on WC-6%Co cemented carbide by double glow plasma surface alloying technique, and diamond was then deposited using microwave plasma chemical vapor deposition system. The thickness of the TiMoTa interlayers increased from 1.2 μm to 2.7 μm with the deposition temperature increasing from 800 to 900 °C. Due to the formation of nano-crystalline structure and hard phase, the as-prepared TiMoTa interlayer exhibited high micro-hardness. In the diamond deposition process, the nano-carbide particles preferentially formed at the TiMoTa interlayers can effectively prevent the further diffusion of C, so the surface carbon concentration rapidly accumulates to the critical value required for the nucleation and growth of diamond microcrystals. Finally, a microscale wear-resistant diamond coating with good adhesion was grown on the transition layer, the crack propagation radius of the diamond coating is ∼162 μm, and can reach Hf 2–3 grade. Therefore, our prepared TiMoTa nano-crystalline interlayer provides a new path for the development of a high-quality diamond coating with good adhesion on cemented carbide.

Visualization and quantitative statistics of experimental hydraulic fracture network based on optical scanning

The formation of hydraulic fracture-network is an important goal for stable and increased production of unconventional oil and gas resources. However, due to the extremely complex mechanical behavior of hydraulic-fracture propagation, there is still a lack of fine, effective and systematic evaluation methods on 3D fracture-network structure. The quantitative characterization of hydraulic-fractures is of great significance to reveal the law of fracture propagation and to evaluate the reservoir stimulation effectiveness reasonably. Although the micro-cracks evolution process follows a random rather than deterministic pattern, the overall fracture morphology is featuring statistical regularity. In this study, after the indoor hydraulic-fracturing simulation experiments of the tight sandstone specimens, 3D optical scanning was used to visualize the fracture-network. On this basis, two aspects of quantitative statistics of 3D complex fracture-networks were established by plane and sphere cuttings for the first time, including angle distribution statistics and spatial variation statistics. Comparative analyses with reported methods showed that, the overall deflection of the macroscopic fracture-networks varies synchronously with the local roughness of the main hydraulic fractures closest to the wellbore, which satisfied exponential function or power-law function relationship between them. The variation of the area proportion with the propagation radius reflects the specific fracture propagation process such as crack initiation, bifurcation and arrest, and could be used to assess the complexity of the fracture-network. Moreover, a new stimulation evaluation index Es was established by comprehensively considering the stimulated-reservoir-area, the dispersion degree of the angle distribution and the complexity of spatial variation for 3D fracture-network. The insights gained warrant further applicability on hydraulic-fracturing in the actual engineering scale.

Ionic communication for implantable bioelectronics.

Implanted bioelectronic devices require data transmission through tissue, but ionic conductivity and inhomogeneity of this medium complicate conventional communication approaches. Here, we introduce ionic communication (IC) that uses ions to effectively propagate megahertz-range signals. We demonstrate that IC operates by generating and sensing electrical potential energy within polarizable media. IC was tuned to transmit across a range of biologically relevant tissue depths. The radius of propagation was controlled to enable multiline parallel communication, and it did not interfere with concurrent use of other bioelectronics. We created a fully implantable IC-based neural interface device that acquired and noninvasively transmitted neurophysiologic data from freely moving rodents over a period of weeks with stability sufficient for isolation of action potentials from individual neurons. IC is a biologically based data communication that establishes long-term, high-fidelity interactions across intact tissue.

MEASUREMENTS OF CHARACTERISTICS FOR FRAGMENTATION – BURSTING HEADS

The paper deals with questions appearing at investigation of high explosive-fragmentation heads of medium calibre when the blast waves (BW) generated by the flying fragments affect the results of velocity of the BW generated by the head itself (HBW). A method used by the authors for protection of measurement sensors against destructive action of the fragments is described. Distribution of produced fragments regarding the sizes and in function of scattering angle was studied. Mean velocity of highest speed (2100 m/s) fragments was measured on the base of first 10 m. Distribution of HBW velocities in function of radius of propagation was measured.

Experimental study of foam propagation and stability in highly permeable porous media under lateral water flow: Diverting groundwater for application to soil remediation

Foam propagation and stability in highly permeable porous media, encountered in soil pollution applications, are still challenging. Here, we investigated the application of foam for blocking the aquifer to divert the flow from a contaminated zone and, therefore, ease the remediation treatments. The main aim was to better understand the critical parameters when the foam is injected into a highly permeable aquifer with high groundwater flow velocity (up to 10 m/day). A decimetric-scale 2D tank experimental setup filled with 1 mm glass beads was used. The front part of the 2D tank was made of transparent glass to photograph the foam flow using the light-reflected method. The water flow was generated horizontally through injection and pumping points on the sides of the tank. The pre-generated foam was injected at the bottom center of the tank. Water streamlines (using dye tracing) and water saturation were investigated using image interpretation. Results show that 100% of the water flow was diverted during the injection of the foam. Foam stability in porous media depends significantly on the horizontal water flow rate. Recirculating water containing the surfactant increases foam stability. The main mechanism of destruction was identified as the dilution of the surfactant in water. However, the head-loss measurements showed that despite foam destruction, the relative permeability of the water phase in the media remained quite low. Injection of foam increases the radius of gas propagation, thanks to foam's high viscosity, compared to a pure gas injection case. These results are new highlights on the efficiency of foam as a blocking agent, showing that it can also serve as a means for gas transport more efficiently in porous media, especially for soil remediation applications.

Modelling and computation of large-scale open atmosphere hydrogenair deflagration

Studying of gas deflagration is important for a safety purpose in gas industry. A modelling approach based on large eddy simulation (LES) technique for modelling turbulent flow combined with the species mass fraction equations for modelling combustion is used. Different flame acceleration mechanisms, hydrodynamic & thermo-diffusive instabilities, turbulence, and their interaction in addition to flame quenching model are used to model chemical reaction rate. An algebraic model for flame-generated turbulence is incorporated. The model is tested against large scale open atmosphere hydrogen-air experiment. The flame propagation radius and the overpressures are qualitatively compared well with experiment and the state-of-the-art simulations.

Injection Rate-Dependent Deflecting Propagation Rule of Hydraulic Fracture: Insights from the Rate-Dependent Fracture Process Zone of Mixed-Mode (I-II) Fracturing

Mixed-mode (I-II) fracturing is a prominent mechanical characteristic of hydraulic fracture (HF) deflecting propagation. At present, understanding the effect of injection rates on HF deflecting propagation remains challenging and restricts the control of HF deflecting propagation bearing tensile and shear stresses with fluid injection rates. Our recently published experimental results show that the fracture process zone (FPZ) length of mixed-mode (I-II) fractures in rock-like materials increases with the rising quasistatic loading rate. Both the deformation in FPZ and the generation of real fracture surfaces are tensile. On this basis, the rate-dependent mixed-mode (I-II) cohesive fracture model was proposed under quasistatic loading, and a couple of theoretical outcomes were obtained. Under different injection rates, the deflecting HF propagates step-by-step under mixed-mode (I-II) fracturing, and the HF extension path is supposed to be straight in each step. With the increment of injection rate, the increased (tensile) FPZ length is the stable propagation distance of deflecting HF in each step and besides deteriorates the fracture resistance discontinuity of FPZ developing to be a real tensile fracture. Thus, the mixed-mode (I-II) fracture tends to propagate unstably driven by kinetic energy once FPZ develops completely under fast loading. Moreover, two injection rate-dependent (IRD) HF deflecting propagation modes were determined, i.e., the step-by-step stable-propagation and step-by-step unstable propagation modes. HF deflection occurs in the step alternation of fracture propagation. With the increasing fluid injection rate, the increased FPZ length and kinetic energy (from fracture resistance discontinuity) extend the stable and unstable HF propagation distance along the initial direction in an extension step, respectively. Therefore, fast fluid injection improves the HF deflecting propagation radius; i.e., it inhibits the HF deflecting propagation or promotes HF extension along the initially designed direction. The injection rate-dependent HF deflecting propagation modes (based on the proposed model) were validated by further processing of published true triaxial physical simulation tests of hydraulic fracturing. The ordinal response of Fiber Bragg grating sensors embedded along the fracture propagation path, and the continuous fluctuant injecting pressures validate the step-by-step propagation of the hydraulic fracture. The test-measured deflecting HF trajectory indicates that high fluid injection rates remarkably increase the HF deflecting radius, which is consistent with the theoretical analysis in this work. The above findings can provide theoretical bases for controlling the HF deflecting propagation in the surrounding rock of mines and oil-gas reservoirs.

Mathematical model of water absorption area in intensive garden irrigation from the ground

This article presents the results of field experiments to irrigate intensive gardens, located in water-scarce areas, from the soil with special piles. Experiments were conducted in Kagan district of Bukhara region in 2016 to determine the optimal procedure for in-soil irrigation of apple variety "Pinc lady" in the intensive orchard, established in 2016 at the farm "Siyavush Kamron FOOD" in cooperation with Turkey. In this case, a mathematical model was developed to determine the irrigation area corresponding to the radius of propagation of the roots of three-year-old trees and to calculate water consumption. This makes it possible to determine the norms of irrigation of intensive garden trees. This method can be used to set half scrubby intensive gardens in such areas where water is insufficient and use energy-saving technologies in the future.

Quantitative optimization of drainage strategy of coalbed methane well based on the dynamic behavior of coal reservoir permeability

The development of coalbed methane (CBM) is not only affected by geological factors, but also by engineering factors, such as artificial fracturing and drainage strategies. In order to optimize drainage strategies for wells in unique geological conditions, the characteristics of different stages of CBM production are accurately described based on the dynamic behavior of the pressure drop funnel and coal reservoir permeability. Effective depressurization is achieved by extending the pressure propagation radius and gas desorption radius to the well-controlled boundary, in the single-phase water flow stage and the gas–water flow stage, respectively, with inter-well pressure interference accomplished in the single-phase gas flow stage. A mathematic model was developed to quantitatively optimize drainage strategies for each stage, with the maximum bottom hole flow pressure (BHFP) drop rate and the maximum daily gas production calculated to guide the optimization of CBM production. Finally, six wells from the Shizhuangnan Block in the southern Qinshui Basin of China were used as a case study to verify the practical applicability of the model. Calculation results clearly indicate the differences in production characteristics as a result of different drainage strategies. Overall, if the applied drainage strategies do not achieve optimal drainage results, the coal reservoir could be irreversibly damaged, which is not conducive to expansion of the pressure drop funnel. Therefore, this optimization model provides valuable guidance for rational CBM drainage strategy development and efficient CBM production.

Effect of thermal cycling-dependent cracks on physical and mechanical properties of granite for enhanced geothermal system

Thermal cycling induced micro-cracks can change the physical and mechanical properties of geothermal energy reservoir, which may influence the heat and mass transfer performance as well as the stability of the reservoir. In this study, thermal cycling treatment was carried out on granite over the temperature range of 20–300 °C with 1–20 thermal cycles. The results show that thermal cycling promotes the initiation and propagation of intergranular and intragranular cracks, which are evenly distributed in all directions. With increase in the number of thermal cycles, the crack density (Pl) increases, resulting in increased permeability (K). The path of seepage passage is mainly between the mineral particles. Moreover, the critical crack propagation radius (rc) of rock decreases with increasing cracking degree, which leads to the decrease in rock fracture resistance. In particular, the fracture toughness (Keff) of granite decreases most when it is subjected to 1–5 thermal cycles. Water-cooling thermal cycling and cooling rate can significantly affect the micro-crack evolution, permeability and ability of granite to resist fracture. The changes in mechanical and physical properties observed in this work can provide basic theoretical reference for the rational selection of geothermal energy mining methods and process parameters, as well as the study of reservoir stability evaluation.

Coalbed methane production of a heterogeneous reservoir in the Ordos Basin, China

Macrolithotypes control the pore-fracture distribution heterogeneity in coal impacting gas adsorption, diffusion coefficient, and the gas flow. However, the behaviors that are impacted by coal macrolithotype are traditionally ignored and the drainage radius that linked to the macrolithotype contributions are lack of systematic research all the way. Thus, to evaluate the gas production relationship for macrolithotype, four blocks (bright, semi-bright, semi-dull, and dull) were obtained from the same seam. The methane absorption, diffusion, and permeability data were obtained and used in mathematical modeling to identify well production, drainage radius, and well-interference locations. Production data for 104 wells and 11 test wells were also obtained and with COMET3 simulation software to validate the mathematical model. From the bright to dull coal: there was a lower micropore contribution, a lower gas capacity, and lower gas diffusion coefficient. The cleat frequency and aperture differences impacted the reservoir permeability with bright coal having 195% higher than the dull coal. As these macrolithotype differences impact the coalbed methane (CBM) development and cause heterogeneous gas flow systems within the resource, a coupled mathematical model for comprehensive consideration of the adsorbent-diffusion-seepage was established capturing the macrolithotype contribution to the pressure propagation, gas flow, and gas drainage radius estimation. The bright coal had the higher Langmuir volume, CH4 diffusion coefficient, and permeability thus, producing a higher gas production volume, and a larger gas drainage area than the dull macrolithotype. Thus, the macrolithotype diversity and its stratification cause partitioning of the gas flow with multi-stage pressure drop effecting exploration and development. In addition, the well interference was also observed and show that the wells of bright and semi-bright coal have a continuous pressure drop, which achieving the purpose of overall pressure reduction.

Analytical study of the direct initiation of gaseous detonations for small heat release

An analysis of the direct initiation of gaseous detonations in a spherical geometry is presented. The full set of constitutive equations is analysed by an asymptotic analysis in the double limit of Mach number close to unity (small heat release) and large thermal sensitivity. The quasi-steady curvature-induced quenching phenomenon is first revisited in this limit. Considering a realistic decrease rate of the rarefaction wave, the unsteady problem is reduced to a single nonlinear hyperbolic equation. The time-dependent velocity of the lead shock is an eigenfunction of the problem when two boundary conditions are imposed to the flow at the lead shock and at the burnt gas side. Following (Linan et al. , C. R. Mec. , vol. 340, 2012, pp. 829–844), the boundary condition in the quasi-transonic flow of burnt gas is expressed in terms of the curvature. Focusing our attention on successful initiation, the time-dependent velocity of the lead shock of a detonation approaching the Chapman–Jouguet regime is the solution of a nonlinear integral equation investigated for stable and marginally unstable detonations. By comparison with the quasi-steady trajectories in the phase space ‘propagation velocity versus radius’, the solution exhibits the unsteady effect produced upon the detonation decay by the long time delay of the upstream-running mode for transferring the rarefaction-wave-induced deceleration across the inner detonation structure from the burnt gas to the lead shock. In addition, a new and intriguing phenomenon concerning pulsating detonations is described. Even if the results are not quantitatively accurate, they are qualitatively relevant for real detonations.

Diffraction of cellular detonation wave over a cylindrical convex wall

Numerical simulations were performed to study diffraction of a cellular detonation wave over a 90∘ cylindrical convex wall. The dynamics of this diffraction phenomenon was described by the two-dimensional reactive Euler equations with a detailed hydrogen/oxygen chemistry model and solved numerically by using the adaptive mesh refinement code AMROC. The present numerical observations indicate that the continuous variation trend of area divergence ratio caused by the curved convex wall can make detonation transverse wave reflect on the wall and sustain the coupling of the diffracted detonation wave for a certain distance. The reflection of the transverse waves can also enhance the energy to promote the re-intiation of the diffracted detonation. As the wall curvature radius increases to a certain value, the detonation wave can even propagate stably without decoupling in the expansion area. The critical wall curvature radius for re-initiation is found to have negative correlation with the contained detonation cell number in the exit, while the critical radius for stable propagation is mainly determined by the initial pressure. The critical re-initiation criterion for the detonation diffraction is further explored by introducing two different re-initiation mechanisms and considering the width of an “equivalent exit” calculated by the Chester-Chisnell-Whitham theory to satisfy the re-initiation condition. Meanwhile the critical criterion of stable propagation is described quantitatively by applying the Dn−κ theory to confirm the relation between the propagation velocity and the curvature of the diffracted detonation wave front, and calculating the minimum curvature radius of the curved detonation wave front theoretically. The accuracy of the criterions are verified by compared with the numerical results.

Optimal design of a single-mode trench-assisted homogeneous multicore fibre with a minimum crosstalk level

We have proposed an optimal design of five different core structures (St1 – St5) for a seven-core trench-assisted multicore fibre, whose core radius and relative core/cladding refractive index difference Δ1 are optimal for single-mode propagation. The crosstalk performance and its reduction (in dB) with respect to variations in fibre design parameters, such as cladding/trench (Δ2) depth and trench width Wt are investigated. It is shown that some fibre operational parameters, like, fibre bending radius, operating wavelength and fibre length, affect the crosstalk performance. It is found that the crosstalk and its reduction amount are extremely dependent on the values of Δ1 and Δ2. The dispersion characteristics of the cores are investigated for all the proposed core structures and the observed dispersion is found to be about – 6 ps nm−1 km−1 at an operating wavelength of 1550 nm. An ultralow crosstalk (less than –100 dB per 100 km) can be achieved mainly with two proposed core structures (St4 and St5) having a suitably higher values of Δ1 along with a small core radius for single-mode propagation. The multicore fibre design with many cores (up to 55) is demonstrated to ensure a high transmission capacity.