Using Landsat TM and OLI multispectral image data, the accuracy of extracting sea area from different water body indices is compared. Finally, the improved normalized water body index (MNDWI) is ...selected to study the dynamic characteristics of the coastline and the progress of reclamation of Dalian in 1996, 2005, and 2015. The results show that: from 1996 to 2005, the area of land reclamation in Dalian reached 31.58km2, and 83.55km2 for 2015-2015. It is mainly used for dock construction, industrial land, aquaculture ponds, port docks, construction sites, residents Land, commercial and financial land, etc.; from 1996 to 2015, the total length of the coastline increased by 132.77km. The length of the artificial shoreline increased significantly, with its continuity in spatial distribution increased; the length of the bedrock shoreline was reduced due to the destruction of reclamation projects. Although large-scale land reclamation has brought good economic and social benefits to the local area, it also has a large impact on the marine and forest ecological environment. It is recommended to moderately develop coastal zone resources and further strengthen monitoring and supervision mechanisms.
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.
In this paper, the particle flow inside the nozzle is simulated by Computational Fluid Dynamics (CFD) method and the numerical results are verified by experimental observation. The motion ...trajectories of incident particles in different regions are investigated through trajectory analysis. In addition, the erosion damage mechanism was analyzed by the surface morphology and impact characteristics of the main abrasion region. The results show that the particle impact position gradually moves forward as the particle incident position moves away from the inlet center. Sensitivity analyses showed that erosion rate was most sensitive to pump pressure; impact frequency, impact velocity and impact angle were most sensitive to particle size, pump pressure and particle size, respectively. Due to the low angle impact of particles, the corresponding erosion damage mechanism is micro-cutting.
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•The trajectories of particles incident from varying regions of the inlet are discussed.•The sensitivity of varying parameters to the impact characteristics was evaluated.•The mechanism of particle erosion on the nozzle was comprehensively elucidated.•The work contributes profound insights into the erosion behavior of AWJ nozzles.
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.
The construction of smart villages is the trend of future rural development. This article uses Songbei Village as an example, using unmanned aerial vehicle (UAV) to achieve efficient and fast aerial ...photography to establish a three-dimensional (3D) model of the area. After the mining, the current situation of Songbei Village was analyzed, and some suggestions were provided for the economic development and rural layout of Songbei Village to promote the construction of smart villages in Songbei Village.
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.
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