Spatial Evolution Law Research Articles

Spatiotemporal Characteristics and Influencing Factors of Tourism-Urbanization-Technology-Ecological Environment on the Yunnan-Guizhou-Sichuan Region: An Uncoordinated Coupling Perspective.

The tourism, urbanization, technology, and the ecological environment both promote and restrict each other. Coordinating the relationship between the four is of great significance to the realization of high-quality sustainable regional development. Taking the Yunnan–Guizhou–Sichuan region as an example, this paper constructs an uncoordinated coupling model for the tourism–urbanization–technology–ecological environment system. Using exploratory spatial analysis and geographic information systems, this paper reveals the temporal and spatial evolution law affecting the uncoordinated coupling relationship between tourism, urbanization, technology and the ecological environment in the Yunnan–Guizhou–Sichuan region from 2010 to 2020, before establishing a panel Tobit model that is used to explore the factors affecting the four systems. The research shows the following: (1) The level of comprehensive development for tourism, urbanization, technology, and the ecological environment in Yunnan, Guizhou, and Sichuan has increased rapidly. Of all these, the tourism industry was the most affected by COVID-19 in 2020, while the level of urbanization, technology, and ecological environment developments in the three provinces has become similar over time. (2) Uncoordinated development between cities is a prominent problem; while the uncoordinated coupling spatial agglomeration in various regions is relatively stable, the proportion of cities with no significant agglomeration form amounts to more than 70%, with mostly low–low (L–L) and high–high (H–H) agglomeration types. (3) The degree to which uncoordinated coupling exists among the four systems in the Yunnan–Guizhou–Sichuan region is affected by many factors. Only eco-environmental pressure has a significant positive correlation with the degree of uncoordinated coupling, while the tourism scale, economic urbanization, eco-environmental response, and investment in technology have a significant negative correlation. These results provide a theoretical basis and practical references for strengthening the government’s macro-control and promoting collaborative regional development.

Spatial and Temporal Evolution of Urban Green Space Pattern Based on GIS Sensors and Remote Sensing Information: Taking Xi’an as an Example

In order to solve the practical application of the continuously developing remote sensing technology in urban planning, this paper proposes a method of temporal and spatial evolution of urban green spatial pattern based on GIS remote sensing information. Based on the Landsat Image data of the main urban area of Xi’an from 2000 to 2012, different classification methods are used to extract the urban green space information and compare the accuracy. The classification results with high accuracy are selected to analyze the temporal and spatial evolution law of urban green space and the change of landscape pattern in the study area. In this paper, the change of vegetation coverage can be divided into five levels: significant degradation: <-0.006; slight degradation: -0.006~-0.002; stable: -0.002~0.002; slight improvement: 0.002~0.006; and significant improvement: >0.006. The results of this paper prove that this method can be used to understand and evaluate the ecological consequences of urbanization and improve our quality of life. At the same time, it can provide basic information for decision-making.

Detection of coal fire by deep learning using ground penetrating radar

Coal fire seriously endangers coal resources. Accurate detection of its combustion range is the basis of disaster control. In this paper, a deep learning-based method of recognizing coal fire using ground-penetrating radar (GPR) is proposed, which improves the accuracy and speed of delineating coal fire areas. The self-built coal fire physical model is scanned by the GPR, and the radar images are obtained. The test results are compared with GPR images to summarize the spatial evolution law of coal fire areas and interpret the signal characteristics of the coal fire in radar images. The signal characteristics include combustion cavity, combustion surface, and underground combustion collapse surface. Comparing different algorithms, the results show that the YOLOv5l has the highest detection accuracy, which meets the need for detection of the coal fire. The proposed method lays the foundation for the detection of the combustion range in the coal fire areas.

Spatial Evolution, Driving Mechanism, and Patch Prediction of Grain-Producing Cultivated Land in China

China has implemented strict policies for protecting cultivated land, and the Chinese government has focused on the non-grain production (NGP) of cultivated land. This study aimed to analyze the spatial evolution law of grain-producing cultivated land (GPCL) in China between 2000 and 2018, explore the mechanism of GPCL, and simulate the spatial characteristics of GPCL in 2036. We used the Geographic Information System (GIS) and a patch-generating land-use simulation model, a new model that proposes a land expansion analysis strategy by improving previous rule-mining methods. China’s grain production rate (GPrate) shows a gradual upward trend between 2000 (36.98%) and 2018 (47.18%). The mutual conversion of GPCL and non-grain-producing cultivated land (NGPCL) are the primary transfer types. The evolution of GPCL is driven by climatic, economic, and social factors, of which population density is the most important factor. GPCL expansion patches are distributed in densely populated, economically developed, and warm and humid plain areas. Further, the simulation results showed that the GPrate in 2036 is estimated to be 41.39%, with GPCL transfer-in significantly exceeding the amount transferred out. Our results further cultivated land evolution-associated research and provide a basis for formulating scientific land-use policies for cultivated land protection for other countries.

Exploring the Temporal and Spatial Evolution Laws of County Green Land-Use Efficiency: Evidence from 11 Counties in Sichuan Province

With rapid urbanisation in China, sustainable urban development faces a major obstacle due to insufficient consideration of land-use efficiency. Currently, despite progress in analysing land-use efficiency, not every land manager has enough knowledge of green land use from a county perspective. Therefore, the objective of this research is to explore the spatiotemporal evolution law focused on county green land-use efficiency (CGLUE), which can support sustainable county development. Based on 10 specific CGLUE factors identified through a content-mining tool, this study explored the temporal and spatial evolution law of 11 counties in Sichuan Province using the ultra-efficient slacks-based measure (SBM), kernel density estimation, and Moran’s I statistic. The study found that (1) CGLUE factors cover the administrative area, total investment in fixed assets by region, the number of employed persons in secondary and tertiary industries, gross domestic product in secondary and tertiary industries, the average wage of staff and workers, basic statistics on per capita park green area, carbon emissions of land, the volume of industrial wastewater discharged, the volume of industrial sulphur dioxide emission, and the volume of industrial soot (dust) emission; (2) from a time-evolution perspective, CGLUE shows an increasing trend of time series evolution as a whole, and its dynamic evolution process has obvious differences in time. CGLUE increased, and the difference in CGLUE became larger from 2010 to 2012. CGLUE also increased, and the difference in CGLUE became smaller from 2013 to 2016. CGLUE also increased, and the difference in CGLUE became larger from 2017 to 2020; (3) from a spatial evolution perspective, the global spatial evolution laws of CGLUE show that the spatial agglomeration state has gone from strong to weak. Overall, however, Sichuan Province CGLUE maintains a high spatial agglomeration effect. The local spatial evolution laws show that the CGLUE of the 11 counties is positively correlated. The high–low CGLUE agglomeration areas are mainly distributed in Chengdu, Mianyang, Meishan and Yibin; the low–low CGLUE agglomeration areas are mainly distributed in Deyang, Yaan, and Zigong. The novelty of the research lies in these aspects: (1) the carbon emissions of land should be considered the undesired output of CGLUE; (2) CGLUE in Sichuan Province has various growing stages from a time perspective; (3) CGLUE in Sichuan Province has a high spatial concentration in Chengdu from spatial view, and these counties’ resources flow and interact at high speed. These findings offer a solid reference for the sustainable development of these 11 counties in Sichuan Province.

Analysis of Temporal and Spatial Evolution Characteristics of Land Subsidence in Western Songnen Plain Using Multisource Remote Sensing

Abstract The exploitation of underground fluid is an important factor leading to land subsidence. The effects of mining depth, frequency, and mode on land subsidence are also different. The objective of this study was to develop a multisource method—including optical remote sensing interpretation, Interferometric Synthetic Aperture Radar (InSAR) technology, and unmanned aerial vehicle (UAV)—to reveal the long-term temporal and spatial evolution law of subsidence characteristics driven by groundwater and oil extraction, as well as to reveal the formation mechanism and seasonal response law of land subsidence under the action of different driving factors. In this paper, we select the western region of Jilin Province located in Songnen Plain as the study area. The subsidence funnels in the study area are distributed in a porphyritic manner, and the distribution of the subsidence funnels has a certain correlation with the distribution of the pumping wells. In farmland areas, the subsidence is mainly caused by pumping groundwater. The annual land subsidence rate in the study area is -3.14 mm/a, and the maximum deformation rate in the study area is -22.05 mm/a. The subsidence is affected by the season, shown by the fact that it rises in the dry season and decreases in the rainy season. The subsidence in the west of Songnen Plain is caused by oil pumping and groundwater pumping, and groundwater pumping is dominant. The exploitation of underground fluid transfers the pressure borne by water or oil to the soil skeleton so as to increase and consolidate the effective stress of the soil layer and lead to land subsidence. The continuous observation of the surface in the western area of Songnen Plain is helpful to guide the safe production of agriculture and industry and ensure the smooth development of local industry and agriculture.

Controlling effect of tectonic-paleogeomorphology on deposition in the south of Lufeng sag, Pearl River Mouth Basin

Paleogene depositional systems in the south of Lufeng sag have complex spatial distribution, which are influenced by pre-depositional paleogeomorphology and multi-period tectonic activities. In this paper, to clarify the controlling effect of tectonic-paleogeomorphology on sedimentary facies distribution and effectively guide oil and gas exploration, the Paleogene paleogeomorphic pattern in the south of Lufeng sag is reconstructed by the impression method, and the temporal and spatial evolution laws of the main faults are clarified. The results show that braided river deltas developed stably in the long-axis gentle slope belt of the lake basin, while the short-axis sedimentary system changed from fan deltas to braided river deltas in response to the change of active strength of dominant faults from strong to weak. It is found that the scale of the sedimentary fan is closely related to the activity of the main fault, the area of the catchment, and the vertical elevation difference. The steep cliff is controlled by the boundary fault with large fault throw and steep section, and there are wedge-shaped sand bodies near the steep cliff. The multi-level fault-step zone provides the driving force for the advancement of the sedimentary system, and the sand body extends for a long distance. It is established that the supply capacity of the source area and the accommodated space of the lake basin are coupled to control the deposition scale. Moreover, the slope controlled by the combination of paleogeomorphic assemblage and the activity of the main fault determines the sedimentary type, and the structural slope-break zone defines the spreading pattern of the sands. Cited as : Jiang, M., Chen, D., Chang, X., Shu, L., Wang, F. Controlling effect of tectonic-paleogeomorphology on deposition in the south of Lufeng sag, Pearl River Mouth Basin. Advances in Geo-Energy Research, 2022, 6(5): 363-374. https://doi.org/10.46690/ager.2022.05.02

The Spatial Evolution Law and Water Inrush Mechanism of Mining-Induced Overburden in Shallow and Short Coal Seam Group

In order to grasp the overburden evolution law of the shallow and short coal seam group, based on the key bed theory, a mechanical analysis of the longitudinal expansion of mining-induced overburden fractures in the coal seam group was carried out, and the spatial evolution characteristics of mining-induced overburden fractures were simulated by the numerical simulation method. The results show that in the process of working face advancement, with the continuous instability and failure of the overburden, the size and shape of the fracture network are also changed. The repeated mining of the lower coal seam further causes the secondary activation of the upper overburden, which makes the roof fractures of the partially compacted goaf violently move again. The “channel source” and “space source” continue to carry out the process of “generation-expansion-compression-generation-expansion”, in combination with pore fracture elastic theory. The water inrush characteristics of the whole coal seam are divided into three “solid-liquid” coupling stages: the original gap seepage stage, the initial water discharge stage of mining fissures and the water inrush stage of fractured rock mass. The steady value of water inflow and its variation characteristics with time are predicted by using the formula of deep well flow in a confined aquifer.

An interacting wing-crack based semi-analytical meso-scale model for describing elasto-plastic damage behavior of brittle rocks

An interacting wing-crack based mesoscale model was developed for describing the elastoplastic damage behaviors of brittle rocks under compressive loading. In the present model, the main deterioration process of the rock is assumed to be induced by the wing-crack propagation, attributing the macroscopic inelastic strain to the nucleation and growth of tensile ‘wings’ of the initial flaws. The initial flaws are assumed to follow a periodic distribution in space. To account for the interaction between microcracks, a spatial evolution law as a function of the wing length is introduced, and the influences of the wing-crack propagation on the discontinuous slip of the crack surface are taken into consideration. On this basis, the increment of the compliance tensor caused by wing-crack propagation is proposed, and an incremental-based constitutive model is constructed so that the total stress-strain relations involving post-peak softening and residual behavior can be reproduced. Further, through appropriate parameter selection, the proposed model can reasonably simulate the triaxial test results of Taiwan sandstone, and the correctness of the model is effectively validated. Finally, the intrinsic features of the model are explored through a series of parametric analyses, and the macroscopic mechanical behavior and damage evolution of the rock characterized by the model are investigated. The conclusions show that this model is of significant usage to describe the whole strain-stress relation and inelastic strain analysis. It is full of potential to deem various rock macroscale mechanisms to mesoscale crack evolution.

Analysis of Surface Deformation and Settlement Characteristics Caused by Tunnel Excavation and Unloading

Aiming at the problems of surface deformation and unloading settlement caused by urban tunnel construction, the basic characteristics of surface deformation caused by tunnel construction, the main influencing factors of surface deformation and settlement, and the temporal and spatial evolution law of stress field and displacement field of surface deformation and settlement are studied by using the comprehensive methods of evaluation factor analysis, theoretical research, and numerical simulation. The results show that the surrounding rock deformation of the tunnel is mainly concentrated in the arch crown and arch bottom, and the deformation gradually decreases from the center of the tunnel to the periphery. The surrounding rock of arch crown has sudden settlement, large deformation rate and amount, and poor stability of surrounding rock, and is prone to engineering accidents such as block falling and even collapse. The farther away from the tunnel, the smaller the degree of settlement. As the time step of tunnel excavation increases, the influence area of surface deformation and settlement increases gradually. After the tunnel adopts reasonable lining support, it can effectively prevent soil deformation transmission and restrain tunnel instability deformation, so as to prevent surface deformation and settlement by improving the self stability of surrounding rock and taking lining support and other measures.

Study on temporal and spatial evolution law for dust pollution in double roadway ventilation system of short wall continuous mining face.

To explore the laws of variations in the evolution of dust pollution within a double tunnel ventilation system at a short wall continuous mining face, a numerical simulation of air flow movement was conducted in this study. Results showed that after the wind flowing in the supporting and heading tunnels reached the head, the wind sides returned at speeds of 6.5 and 10.3m/s, respectively. Affected by the air volume and pressure differences between the two tunnels, part of the air flow entered the connecting tunnel at an average speed of 0.8m/s and moved to the heading tunnel. Affected by the turbulence at the driving face, a high dust concentration zone with a maximum dust concentration of 1700mg/m3 was formed in the tunnels at a distance of 15m from the heading. Dust blocked by the shuttle car accumulated and settled near it and formed a dust zone with an approximate average concentration of 750mg/m3 at a distance of 19-23m from the heading. The dust produced by the bolt machine formed a dust mass with an average concentration of 900mg/m3 at a distance of 0.5-4.5m from the head. Quantitative analyses of the changes in dust concentration with time at the position of a driver of the continuous mining machine, shuttle car, and anchor bolt machine were conducted, and functional formulae for the quadratic distribution were obtained. Suggestions for dust control were then proposed.

The temporal and spatial evolution law of construction land structure in central Yunnan urban agglomeration based on GIS

The temporal and spatial evolution law of construction land structure in central Yunnan urban agglomeration based on GIS

Physical Simulation Test on Surrounding Rock Deformation of Roof Rockburst in Continuous Tunneling Roadway

To study the occurrence process, as well as the temporal and spatial evolution laws, of rockburst disasters, the roof deformation of continuous heading roadways during rockburst was studied through a physical similarity simulation test with a high similarity ratio and low strength. The deformation and failure evolution law of the roadway roof in the process of rockburst were analyzed by using detection systems, including a strain acquisition system and a high-power digital micro-imaging system. The results show that the rockburst of the roadway roof can be divided into four stages: equilibrium, debris ejection, stable failure, and complete failure stage. According to the stress state of a I–II composite crack, the theoretical buckling failure strength of the surrounding rock is determined as 1.43 times the tensile strength. The flexural failure strength of a vanadium-bearing shale is 1.29–1.76 times its compressive strength. With continuous advancement in the mining time, the internal expansion energy of the roadway roof-surrounding rock in the equilibrium stage continuously accumulates. The fracture network continuously increases, developing to the stable failure stage, with bending deformation, accompanied by continuous particle ejection until the cumulative stress in the failure stage increases, and the tensile state of the rock surrounding the roof expands radially into deep rock. A microscopic damage study in similar material demonstrated that the deformation of the roadway roof is non-uniform and uncoordinated. In the four stages, the storage deformation of the rock surrounding the roadway roof changes from small accumulation to continuous deformation, to the left (or deep rock). Finally, the roadway roof-surrounding rock becomes completely tensioned. The research results presented in this study provide a reference for the prediction and control of rockburst in practical engineering.

Comprehensive monitoring for rockburst at a pumped storage power station in northeast China

Rockburst is characterised by the wide occurrence areas and the long delayed time at a pumped storage power station in Heilongjiang province of China. For the study, a new method is proposed to identify the induced rockburst based on the combination of microseismic (MS) and electromagnetic radiation (EMR) monitoring methods. EMR monitoring method is introduced to make up for the shortcomings of the monitoring blind area caused by the propagation path of wave velocity during MS monitoring and a beneficial attempt is carried out for the comprehensive application of the two methods to monitor the rockburst. Firstly, a MS monitoring system is established around the underground powerhouse to recognize the propagation of micro-fracture during the deep excavation, while the typical five parameters including the frequency of the microseismic events, the total energy of daily events, energy index (EI), cumulative apparent volume (CAV) and microseismic signal b-value are analyzed to reveal the temporal and spatial evolution law of microseismic events. Secondly, an EMR monitoring system is also established near the MS events clusting area to study the characteristics of EMR produced from the fractured rock mass. The temporal and spatial variation of the two parameters including electromagnetic radiation intensity and pulse number are also analyzed and the distribution of higher values are compared with the geological structure. Finally, the correlation of electromagnetic signals, microseismic signals and local stress is studied based on theories of geophysics, electromagnetism and rock mechanics, and some credible results are obtained. Here are the following resluts: (1) The microseismic events are characterized by spatial clustering, and the joint action of the excavation disturbance and the weak structure body of the surrounding rock mass are the main factors for rockburst. The trend of sharp decrease of energy index and sudden increase of cumulative apparent volume generally indicates the occurrence of rockburst or macro-fracture. The magnitude of b value indicates that the rockburst failure type in the project belongs to fracture-slip rockburst. (2) The sudden change of electromagnetic radiation intensity in the fault fracture zone of the underground powerhouse can be used as the precursor information of rockburst or large-scale rupture events.(3) The micro-fracture activities revealed by EMR and MS methods are consistent in spatial distribution. The distribution of the peak values of electromagnetic radiation pulse number are basically consistent with the direction of the apparent stress migration disturbed by the field construction situation. So we can infer that it will play an important role to improve the accuracy of rockburst prediction based on the analysis of the multi-source singals.

Experimental and Numerical Analysis of Rock Burst Tendency and Crack Development Characteristics of Tianhu Granite

Rock burst is a serious nonlinear dynamic geological hazard in underground engineering construction. In this paper, a true triaxial unloading rock burst experiment and numerical simulation are carried out on Tianhu granite to investigate the rock burst tendency and crack development characteristics of surrounding rock after excavation. The experiment and numerical simulation process monitored the rock burst stress path to determine the rock burst stress. According to the evolution law of the frequency and amplitude of rock burst acoustic emission monitoring, the shape characteristics of rock burst fragments are analyzed. The rock burst numerical simulation analysis is carried out by the PFC software, and the temporal and spatial evolution law of cracks is obtained. The research results show that the laboratory experiment and numerical simulation of Tianhu granite have rock burst strengths of 163.4 MPa and 161 MPa, respectively, and the average rock burst stress ratio is 8.38, that is, the Tianhu granite has a low rock burst tendency. During the rock burst, the development of tensile cracks will produce flaky debris, and the development of shear cracks will produce lumpy debris. Rock burst will happen when the crack growth rate to be exceeded the unloading crack growth rate; therefore, it can be used as a precursor signal for the occurrence of rock burst.

Microseismic Temporal-Spatial Precursory Characteristics and Early Warning Method of Rockburst in Steeply Inclined and Extremely Thick Coal Seam

Early warning of a potential rockburst risk and its area of occurrence helps to take effective and targeted measures to mitigate rockburst hazards. This study investigates the microseismic (MS) spatial-temporal precursory characteristic parameters in a typical steeply inclined and extremely thick coal seam (SIETCS) with high rockburst risk and proposes three spatial/temporal quantification parameters and a spatial-temporal early warning method. Analysis results of temporal parameters show that the sharp-rise-sharp-drop variation in total daily energy and event count can be regarded as a precursor for high energy tremor. The appearance of peak values of both energy deviation (≥20) and event count deviation (≥1) can be regarded as precursors that indicate imminent rockburst danger. A laboratory acoustic emission (AE) experiment reveals that precursor characteristics obtained from the study can be feasibly used to warn the rockburst risk. The spatial evolution laws of spatial parameters show that the high energy density index of MS (EDIM), velocity, velocity anomaly regions correlate well with stress concentration and rockburst risk areas. The field application verifies that the temporal-spatial early warning method can identify the potential rockburst risk in a temporal sequence and rockburst risk areas during the temporal early warning period.

Study on the Effect of Isotropic Initial Stress on the Anchoring Performance of Self‐Expanding Bolts

In order to study the anchoring performance of a new type of self‐expanding, high‐strength, precompression anchoring technology with a large amount of expansion agent (ω ≥ 5) cement slurry as anchoring solids under confined surrounding rock conditions, a rock mass anchoring device and methods that simulate in situ stress are developed, and real‐time monitoring of expansion stress and anchor pull‐out tests are carried out. The results show that the internal interface stress has a loss effect over time, and the stress loss value shows a linear increase trend with the dosage, but the loss rate shows a linear decreasing relationship with the dosage. This paper defines the coordinated additional stress and obtains its temporal and spatial evolution law in the rock mass. It is pointed out that there is a lag time difference between the peak of internal interface stress and the peak of coordinated additional stress, explaining its mechanical mechanism from the perspective of stress transfer. The strong restraint of the sealing section of the anchor hole causes the anchor solid to form a “shuttle‐shaped” microexpanded head with thin ends and a middle drum under the expansion stress. During the drawing process, the microexpanded head is “stuck” in the anchor hole and moves upward to form the unique “load platform effect” of the anchoring system. And the mechanical mechanism diagram of this effect is obtained. It is pointed out that this effect can greatly improve the ductility of the anchoring system and the ultimate energy consumption value of damage. A prediction model for the ultimate pull‐out force of self‐expanding bolts is established. It is pointed out that the initial confining stress value has an exponential effect on the ultimate pull‐out force. It shows that the surrounding rock with strong confinement constraints can greatly increase the ultimate pull‐out resistance of the bolt. The self‐expanding strengthening coefficient λ and the surrounding rock stress influence coefficient k are introduced, the bolt interface mechanics formula and energy equation of the self‐expanding anchor system are established, and the feasibility of the formula is verified by the calculation example. It is concluded that the ultimate pull‐out resistance of the anchorage with ω = 30 is increased by 3.38 times compared with the ordinary anchorage under the initial confining stress condition of 0.7 MPa, the prepeak displacement of the bolt is increased by 2.08 times, and the prepeak energy consumption of the anchoring system is increased by 7.34 times. The cost only increased by 0.023% based on the literature example.

Analysis of hazardous waste based on GIS

The increasing production of hazardous waste and the imbalance of regional disposal capacity are more and more prominent in the contradiction between industrial development and environmental protection. His paper takes the production of hazardous waste as the research object, combined with the geographic information system, and based on the regional difference and institutional density of hazardous waste [1], starting from the production of hazardous waste in each province, reveals the temporal and spatial evolution law of hazardous waste production in China, and explores the potential gathering areas of high-risk hazardous waste and their site selection in the future. Based on the hazardous waste disposal capacity of each province, the production of hazardous waste in the next five years in the high-high-type regions was predicted by using the Holt-Winters model fitting prediction model [2]. The results show that there is no significant spatial autocorrelation of hazardous waste production in China. As can be seen from the local accumulation characteristics of hazardous waste production in each province, the high-high type is mainly concentrated in the eastern coastal area. During 2011-2019, the number of high-high type significant hot spots increased from 1 to 4.In the next five years, the production of hazardous waste in high-high-type regions will continue to increase, and it may move to the direction of decline in Shandong Province. Based on the weighted factor method, the proposed optimal location of hazardous waste treatment plant is located in Yancheng City, Jiangsu Province.

Simultaneous measurement of cloud microphysical parameters based on digital holographic interferometry

Investigation of cloud microphysical is of great significance in deepening the understanding of the radiation energy budget, water cycle process, and precipitation mechanism, and improving the scientificity and effectiveness of artificial precipitation. Especially under the action of turbulence, in addition to shear and inertia, the turbulence in the cloud will accelerate the collision of cloud droplets through vortex superposition. The above process will further complicate the cloud microphysical characters. At present, the methods of measuring cloud microphysical parameters based on light scattering, collision and imaging theories encounter bottlenecks: the inversion process needs to make the assumptions about cloud droplet spectrum and particle characteristics, the impact process will destroy particle characteristics, and the three-dimensional characteristics of cloud particles cannot be obtained. Because of its many advantages, such as fast, real-time, non-destructive, non-invasive, high-resolution, full-field optical measurement, etc., in-line digital holographic interferometry is considered as a new potential tool for the dynamical measurement of cloud microphysical property. In particular, the mutual interference between the particle image and twin image is small under far-field recording conditions. In this paper, the measurement method of the on-line digital holographic interferometry based on interference theory, combining optical information processing, depth of field compression, and gray gradient variance technology of fusion holograms, is investigated. This method, with a <i>z</i>-axis position accuracy of 0.01 mm and system resolution of 2 μm, is employed for simultaneously and finely detecting the cloud droplet spectrum, cloud particle diameter, and number concentration. In the experiment, the liquid droplet with a median diameter of 3.9 μm, produced by the ultrasonic atomizer, is used as an example of the cloud particle. The measurement results are consistent with realistic scenario. By using a high speed charge coupled device or complementary metal oxide semiconductor camera, this method can solve the technical bottleneck of three-dimensional fine characteristics of cloud particle in airborne measurement by using cloud droplet spectrometer. It can provide effective support for the research of liquid water in the cloud, entrainment, condensation, collision, and temporal and spatial evolution laws. In addition, it has reference significance for the study of particle dynamics. Simultaneously, this method provides a feasible solution for the measurement of cloud in land-based and airborne platforms.

Structural Mechanical Characteristics and Instability Law of Roof Key Block Breaking in Gob-Side Roadway

The influence of mining on the upper section of working face leads to the fracture of the lateral key block of the roof. From the goaf to the coal body, a group of “left-middle-right” key blocks are formed. According to the three different spatial position structure relations formed by roadway and broken key block in practical engineering, the mechanical causes of broken structure of key block in roof of roadway along goaf are analyzed. FLAC3D is used to simulate and analyze the deformation characteristics and stress state of key block structure model before and after roadway excavation, and the mechanical characteristics and instability mechanism of key block sliding and breaking under three spatial structure modes are obtained. With the help of the mathematical model of material mechanics, the structural mechanical behavior of key block model of roof before and after roadway excavation and the temporal and spatial evolution law of unloading and breaking are studied. The results show that the complex influence factors of mining disturbance and low strength of the weak rock mass will weaken the internal balance of “masonry beam” structure. When the roadway is located below the fracture line of the key block, the middle key block will rotate and lose stability with the side hinge joint of the goaf as the axis; when the roadway is located in the fracture line of the key block, it is easy for the middle key block to slide and lose stability; when the roadway is located outside the fracture line of the key block, the middle key block is in the state of complete collapse, the mechanical transmission mechanism of the surrounding rock in the vertical direction is weakened, and the surrounding rock is the most stable.