In this paper, a numerical model based on the coupling algorithm of SPH-FEM is established and verified by laboratory experiments, the fragmentation mechanism of granite impacted by the abrasive ...water jet is discussed. Compared with the experimental results, the error of erosion depth is less than 5.46%, the error of influence range around the punching is less than 3.89%, and the error of punching diameter is less than 7.16%. The numerical model shows that the material removal is usually caused by the diffusion around the jet stream, and the total amount is 84.06%. The results show that under the strong impact of the jet, it will penetrate all substances in the jet path. When the kinetic energy of the jet is decreases, the removal of materials usually follows the weak path, that is, through the cleavage plane of the feldspar grains and the contact interface between the mineral crystals.
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•A numerical model of heterogeneous granite is established.•The influence of granite minerals on the removal mechanism of AWJ is discussed.•The crushing process of granite impacted by AWJ is reproduced by simulation.•Two kinds of material removal forms of granite impacted by AWJ are described.
The development of deep geothermal resources encounters challenges related to high temperatures and hard reservoir rocks. Abrasive water jets (AWJ) offer a potential solution to enhance the ...efficiency of breaking high-temperature hard rocks in deep ground. This mainly originated from their combined characteristics of jet cooling impact and high-speed abrasive grinding. In order to investigate the dynamic deformation process and rock-breaking mechanism of high-temperature hard rocks cut by AWJ, laboratory tests were conducted on high-pressure abrasive water jets cutting granite, sandstone, and marble. Rock strains were monitored using dynamic strain gauges and the digital image correlation (DIC) technique. The results indicate that in the process of abrasive jet cutting high-temperature hard rock, the rock strain is divided into three stages: compression deformation, deformation release, and stable deformation. The strain response zone can be divided into strain concentration zone, strain transition zone, and strain weak response zone. The high strain region and heat exchange region of high-temperature hard rock during AWJ cutting process are almost consistent. Jet vaporization weakens the water cushion effect during the water hammer stage, leading to high strain concentration at the stagnation point of the jet. During the stagnation stage, the fluid weakens the binding of particles, the abrasive becomes more divergent, and the range of high strain response region expands. Unlike the dynamic strain generated by jet erosion of hard rock, when jet cutting rocks, the strain in the vertical jet direction is generally greater than that along the jet direction. The cutting effect increases with the increase of rock temperature. When the rock temperature is 300 °C, the cutting depth of sandstone, granite, and marble increases by 50 %, 120 %, and 180 %, respectively. Under the combined effects of high-frequency jet impact, high-speed abrasive grinding, and thermal stress, hard rock undergoes varying degrees of damage and failure.
Abrasive water jet is widely used in the field of deep hard rock cutting. To accurately and quantitatively evaluate the implementation effect of repeated cutting hard rock by jet, the ratio of the ...jet cutting speed to the cutting times is defined as an index to evaluate the rock-breaking effect and efficiency, and laboratory experiments of repeated cutting granite by abrasive water jet under different horizontal stress are carried out. The obtained results show that the increase of rock horizontal stress leads to a rougher cutting surface of the abrasive jet, the average growth rate of roughness is 34.8 and 15.8%, respectively, and increases the specific energy consumption rate of the rock breaking, the average growth rate of specific energy consumption is 11.8 and 38.9%, respectively. When the repeated cutting method is used to break rock, as the ratio of the cutting speed to the cutting times increases, the cutting surface roughness and the specific energy consumption of rock breaking decrease first and then increase. When the cutting speed is 9 mm/s and the cutting is repeated for 3 times, the breaking effect and efficiency are the best. Under the combined action of axial high-speed impact, radial rotary grinding, and water wedge cracking, the local mineral particles in the slot may undergo trans-granular or inter-granular fracture, which eventually evolves into spalling and macro-damage of mineral particles.
Highlights
The variation of geometric parameters of slot cut by abrasive water jet with different horizontal stress and repeated cutting times is analyzed.
The surface roughness changes after repeated jet cutting were analyzed using three-dimensional morphological scanning.
The micro morphological characteristics of the slot surface under repeated cutting by abrasive water jet are described.
The results could provide theoretical basis and production guidance for hydraulic cutting and breaking of deep hard rock.
To investigate the jet breaking mechanism of hard rocks under three-dimensional stress, jet breaking experiments under different ground stresses and horizontal stress differences were performed. The ...results showed that the rock-breaking holes were in the shape of an “inverted Ω". The ground stress had an obvious effect on the rock-breaking performance of the jet. As the ground stress increased, the rock strength increased, and the rock-breaking performance decreased by 28.56%. At ground stresses greater than 50 MPa, the rock-breaking performance increased by 20%. The horizontal stress difference made the pore wall stress concentrated and loosened the cementation between mineral particles. As the stress difference increased, the roughness increased, and the rock-breaking performance increased by 58.85% while the energy consumption decreased by 25.56%. The results of this study provide data and technical support for the jet breaking of hard rock in deep mine construction.
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•High-speed particle jet rock-breaking test was performed under deep in-situ stress.•The effect of stress difference on rock-breaking performance was examined.•The microscopic morphological characteristics of the crushing holes were studied.•The effect of three-dimensional stress on rock-breaking by a jet was determined.
Efficient breaking of hard mineral rocks is an important prerequisite for deep metal mining. In order to study the rock breaking mechanism of abrasive water jet erosion of high-temperature hard rock ...in deep ground, the temperature deformation evolution law during the process of jet impact on rocks was simulated and experimentally studied. The results show that the distribution of jet pressure, jet velocity, and jet turbulent kinetic energy near the residence point of the jet impingement wall is generally high in the middle and low in the outside. The heat transfer distance r on the rock surface is approximately (1.5-2.0) times the nozzle diameter, and the heat transfer distance inside the rock is (1.0-1.5) times the nozzle diameter. The maximum heat flux density at the jet cooling wetting boundary can reach 450 W/mm
2
. Within 0-3 seconds of the erosion process, the average surface temperature sharply decreases and exhibits a downward trend of jet stagnation point radiating outward. The radius of jet cooling influence gradually increases. Due to the impact cooling effect, tensile stress is generated at the top of the rock sample, and the tensile stress in the lower part of the rock is converted into compressive stress. With the increase of jet pressure and treatment temperature, the area and range of erosion pits significantly increase, and there is a significant phenomenon of thermal cracking around the erosion pits. The research conclusion can provide new ideas and basis for hydraulic breaking of high-temperature hard rocks in deep ground.
An abrasive water jet (AWJ) is commonly used to develop deep geothermal resources, such as drilling in hot dry rock (HDR). The influence of rock mineral properties, such as mineral types, mineral ...contents, and grain size, on the formation of perforation by AWJ is unclear yet. In this study, we investigate AWJ impacts on three types of granite samples with different mineral fractions using a polarizing microscope and scanning electron microscope (SEM). The results show that when the grain size is doubled, the perforation depth increases by 16.22% under the same type of structure and properties. In general, fractures are more likely to be created at the position of rough surfaces caused by abrasive impact, and the form of fractures is determined by the mineral type. In addition, microstructure analysis shows that transgranular fractures typically pass through large feldspar particles and quartz removal occurs along mineral boundaries. The longitudinal extension of perforation depends mainly on the strong kinetic energy of the jet, while the lateral extension is controlled by the backflow. The results contribute to a better understanding of the process involved in the breaking of hard rock by abrasive jets during deep geothermal drilling.
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•A doubling of grain size results in a 16.22% increase in perforation depth.•Fractures are more likely to be created at the position of rough surfaces.•The form of fractures is determined by the mineral type.•Clarifies the mechanism of perforation lateral and vertical expansion.
In subsurface projects where the host rock is of low permeability, fractures play an important role in fluid circulation. Both the geometrical and mechanical properties of the fracture are relevant ...to the permeability of the fracture. To evaluate this relationship, we numerically generated self-affine fractures reproducing the scaling relationship of the power spectral density (PSD) of the measured fracture surfaces. The fractures were then subjected to a uniform and stepwise increase in normal stress. A fast Fourier transform (FFT)-based elastic contact model was used to simulate the fracture closure. The evolution of fracture contact area, fracture closure, and fracture normal stiffness were determined throughout the whole process. In addition, the fracture permeability at each step was calculated by the local cubic law (LCL). The influences of roughness exponent and correlation length on the fracture hydraulic and mechanical behaviors were investigated. Based on the power law of normal stiffness versus normal stress, the corrected cubic law and the linear relationship between fracture closure and mechanical aperture were obtained from numerical modeling of a set of fractures. Then, we derived a fracture normal stiffness-permeability equation which incorporates fracture geometric parameters such as the root-mean-square (RMS), roughness exponent, and correlation length, which can describe the fracture flow under an effective medium regime and a percolation regime. Finally, we interpreted the flow transition behavior from the effective medium regime to the percolation regime during fracture closure with the established stiffness-permeability function.
Introduction
The roots of Stephania succifera are used in traditional medicine for the treatment of several diseases. Research on this plant has mainly focused on bioactive alkaloids from the roots, ...and no previous work on compounds from the abundant leaves has yet been reported.
Objective
To identify and compare alkaloidal compounds in S. succifera roots and leaves and to predict the potential bioactivity of some alkaloids.
Methods
High‐performance liquid chromatography with quadrupole time‐of‐flight tandem mass spectrometry (HPLC‐QTOF‐MS/MS) was employed to identify alkaloidal compounds from S. succifera. The potential targets and bioactivities of most alkaloids were predicted using the PharmMapper server.
Results
Fifty‐six alkaloidal compounds, including protoberberine‐, aporphine‐, proaporphine‐, benzylisoquinoline‐, and lactam‐type alkaloids, were identified or tentatively identified in S. succifera roots and leaves based on the HPLC‐MS data. Forty‐one compounds have not been previously reported in S. succifera and eight of them have not been previously reported in the literature. Twenty‐four alkaloidal compounds were found in both roots and leaves. Twelve potential targets with different indications were predicted for some alkaloids.
Conclusion
Comparison of chemical constituents and their potential bioactivities for S. succifera roots and leaves indicated that diverse bioactive alkaloids were present in the leaves as well as the roots. PharmMapper provided new directions for bioactivity screening. This study will be helpful for further understanding the medicinal components of S. succifera and the rational utilisation of plant resources.
Fifty‐six alkaloidal compounds were identified or tentatively identified in Stephania succifera roots and leaves by HPLC‐QTOF‐MS/MS. Forty‐one compounds have not been previously reported in S. succifera and eight of them have not been previously reported in the literature. Twenty‐four alkaloidal compounds were found in both roots and leaves. Twelve potential targets with different indications were predicted for some alkaloids using PharmMapper. The results provide useful information on potential medicinal uses and guide further research on S. succifera.
