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The splitting tensile tests on the artificial jointed rock mass specimens were carried out using cylindrical samples after being exposed to high temperatures. The effects of the dip angle of joint plane, the radial elastic modulus, the radial peak strain, the damage variable D, the loading rate and the high temperature on the tensile strength of the jointed rock mass were investigated. Test results show that: (1) when the past-exposed high temperature is the same and the dip angle β (the angle between the joint plane and the horizontal plane) of joint plane increases from 0° to 90°, both the tensile strength and the radial elastic modulus first decrease and then increase. However, the damage variable D increases with the dip angle β rising from 0° to 60°, and decreases with the dip angle β elevating from 60° to 90°. (2) When both the dip angle β and the loading rate are the same, as the exposed high temperature increases from room temperature 25 to 400 °C, the tensile strength, the radial elastic modulus decreases and the radial peak strain all gradually decrease, whereas the damage variable D increases gradually. (3) When both the dip angle β and the past-exposed temperature are the same, as the loading rate increases from 0.05 to 5.0 mm/min, the tensile strength and the radial elastic modulus both increase gradually, whereas the damage variable D decreases gradually.

Crack propagation and rock failure under hydromechanical coupling have typical time-dependent characteristics, and the subcritical crack propagation is one of the most important causes of rock instability. Rheological tests based on mortar specimens containing single internal 3-D cracks and the corresponding numerical simulations are carried out to investigate the time-dependent characteristics of the crack propagation, the failure mode of rocks, and the effects of water pressure and crack dip angle. The mortar specimen exhibits a tensile-shear failure mode under the hydromechanical coupling as observed in rheological tests, and a macro-fracture penetrates the upper and lower ends of the specimen. The propagation rate of the crack decreases first and then increases. The crack propagation can be divided into three stages according to the relationship between the propagation rate and fracture parameters. The water pressure significantly reduces the time required for rock failure due to its promoting effect on the crack propagation rate, which has negative effects on the long-term stability of rocks. Cracks with a dip angle of 45° are more likely to cause rock failure under hydromechanical coupling, while cracks with larger dip angles exhibit a better long-term stability.

When a pig mounted with permanent magnets gets stuck in the pipeline, it can be located by detecting the magnetic anomalies on the ground using a single-axis magnetic sensor. In order to collect the magnetic anomaly efficiently through single-axis magnetic sensor, a geometric detection model and calculation method for single-axis magnetic anomaly detection is established in this paper. The distribution of magnetic inclination and declination of the measuring points is obtained. The results indicate that the magnetic inclination of all measuring points vary within a small range of 2°, and this value is highly dependent on the magnetic sensor which is configured aboveground around the geomagnetic inclination. However, the magnetic declination at different points of detection surface is subject to the geomagnetic components and the Y-axis component of the magnetic field of magnets. The magnetic declinations distribute irregularly and vary in a wide range. Therefore, to achieve a high-efficiency detection with the single-axis sensor, the sensor shall be placed in such a manner that the magnetic inclination thereof coincides with the geomagnetic inclination. The magnetic declination of the sensor can be calculated using s, the superposed Y-axis component induced by the permanent magnets, and the corresponding formula given in this paper. The article demonstrates the feasibility of locating a blocked pig in the pipeline based on the single-axis magnetic anomaly detection. It will have a practical significance in guiding the engineering detection. Keywords: Pig blockage, Pig locating, Single-axis magnetic anomaly, Magnetic anomaly detection, Optimized installation of sensor

Understanding the characteristics of drawing body shape is essential for optimization of drawing parameters in longwall top coal caving mining. In this study, both physical experiments and theoretical analysis are employed to investigate these characteristics and derive a theoretical equation for the drawing body shape along the working face in an inclined seam. By analyzing the initial positions of drawn marked particles, the characteristics of the drawing body shape for different seam dip angles are obtained. It is shown that the drawing body of the top coal exhibits a shape-difference and volume-symmetry characteristic, on taking a vertical line through the center of support opening as the axis of symmetry, the shapes of the drawing body on the two sides of this axis are clearly different, but their volumes are equal. By establishing theoretical models of the drawing body in the initial drawing stage and the normal drawing stage, a theoretical equation for the drawing body in an inclined seam is proposed, which can accurately describe the characteristics of the drawing body shape. The shape characteristics and volume symmetry of the drawing body are further analyzed by comparing the results of theoretical calculations and numerical simulations. It is shown that one side of the drawing body is divided into two parts by an inflection point, with the lower part being a variation development area. This variation development area increases gradually with increasing seam dip angle, resulting in an asymmetry of the drawing body shape. However, the volume symmetry coefficient fluctuates around 1 for all values of the seam dip angle variation, and the volumes of the drawing body on the two sides are more or less equal as the variation development volume is more or less equal to the cut volume. Both theoretical calculations and numerical simulations confirm that the drawing body of the top coal exhibits the shape-difference and volume-symmetry characteristic.

Earth’s equatorial ionosphere exhibits substantial and unpredictable day-to-day variations in density and morphology. This presents challenges in preparing for adverse impacts on geopositioning systems and radio communications even 24 hours in advance. The variability is now theoretically understood as a manifestation of thermospheric weather, where winds in the upper atmosphere respond strongly to a spectrum of atmospheric waves that propagate into space from the lower and middle atmosphere. First-principles simulations predict related, large changes in the ionosphere, primarily through modification of wind-driven electromotive forces: the wind-driven dynamo. Here we show the first direct evidence of the action of a wind dynamo in space, using the coordinated, space-based observations of winds and plasma motion made by the National Aeronautics and Space Administration Ionospheric Connection Explorer. A clear relationship is found between vertical plasma velocities measured at the magnetic equator near 600 km and the thermospheric winds much farther below. Significant correlations are found between the plasma and wind velocities during several successive precession cycles of the Ionospheric Connection Explorer’s orbit. Prediction of thermospheric winds in the 100–150 km altitude range emerges as the key to improved prediction of Earth’s plasma environment. Observations from the National Aeronautics and Space Administration Ionospheric Connection Explorer confirm the link between thermospheric winds and ionospheric plasma variability.

The lithology of Ahvaz city is very complex due to a combination of tectonic activities, flood plain sedimentation, and faulting. These features form subsoil of layers with different types and abrupt changes in stiffness. This lithology combined with a reverse fault may have significant effect on site amplification. This can be very destructive and may cost thousands of lives and needs to be investigated. In this research, the effect of abrupt changes in type and stiffness of material of layers and the variation of dip angle of faulting is studied numerically using finite element Plaxis software and finite difference Flac software. Based on the data from geotechnical studies in Ahvaz city area, some soil profiles and material properties are selected to perform the parametric study. It was concluded that the contrast in stiffness of material has a significant effect on the site amplification. In case of a soft interlayer embedded in dense layers with comparable thickness, the amplification ratio (AR) increases with increasing the stiffness of interlayer. But if its stiffness is higher than the surrounding layers, the AR decreases, as it cannot transmit the shear wave. Also, it was found that the AR increases as the thickness of the softer interlayer increases, due to the domination of the soft interlayer in soil profile. Moreover, it was concluded that in case of the presence of a fault in homogeneous silty clays, AR is not affected by the dip angle of the fault; however, the minimum amplification happens at a dip angle of 45°. Also, it was found that in case of a faulted stiff silty clay with a loose sandy interlayer, a dip angle of 30° yields an AR of 6.25 and a large displacement, which is destructive. But, in case of a faulted soft silty clay profile including a dense sandy interlayer, the maximum AR corresponds to a dip angle of fault of 45°.

Stable gas gravity drainage is considered an effective method to enhance oil recovery, especially suitable for deep buried, large dip angle, and thick oil reservoirs. The influence of reservoir heterogeneity on controlling the gas–oil interface and sweep characteristics of injected gas is particularly important to design reservoir development schemes. In this study, according to the interlayer characteristics of Donghe carboniferous oil reservoirs in the Tarim Basin, NW China, 2D visual physical models are established, in which the matrix permeability is 68.1 mD and average pore throat radius is 60 nm. Then, hydrocarbon gas gravity drainage simulation experiments are carried out systematically, and a high-speed camera is used to record the process of gas–oil flow and interface movement. In this experiment, the miscible zone of crude oil and hydrocarbon gas is observed for the first time. The interlayer has an obvious shielding influence, which can destroy the stability of the gas–oil interface and miscible zone, change the movement direction of the gas–oil interface, and reduce the final oil recovery after gravity drainage. The remaining oil mainly is distributed near the interlayers. The higher displacement pressure leads to increased stability of the gas–oil displacement front and later gas breakthrough, which leads to higher oil recovery. The lower gas injection rate contributes to a slower front velocity and wider miscible zone, which could delay gas breakthrough. For the immiscible gas gravity drainage, there is a critical gas injection rate, with which the oil recovery factor is the highest.

The geometries of trenches vary worldwide due to continuous plate boundary reorganization. When two trenches intersect to generate a corner, a subduction cusp is formed. Although subduction cusps are frequently observed throughout historical plate movement reconstructions, few studies have been conducted to explore the controlling factors of trench migration and slab morphology along subduction cusps. Here, we use a 3-D dynamic subduction model to explore the influence of the overriding plate strength, initial slab-pull force, and initial cusp angle on the evolution of subduction cusps. Our numerical model results suggest the following: 1) subduction cusps have a tendency to become smooth and disappear during the subduction process; 2) the slab dip angle is smallest in the diagonal direction of the subduction cusp, and a larger cuspate corner angle leads to a larger slab dip angle; 3) the asymmetric distribution of the overriding plate strength and initial slab-pull force determine the asymmetric evolutionary pathway of subduction cusps. Our results provide new insights for reconstructing the evolution of subduction cusps from seismological and geological observations.

Digital panoramic borehole imaging technology has been widely used in the practice of drilling engineering. Based on many high-definition panoramic borehole images obtained by the borehole imaging system, this paper puts forward an automatic recognition method based on clustering and characteristic functions to perform intelligent analysis and automatic interpretation researches, and successfully applied to the analysis of the borehole images obtained at the Wudongde Hydropower Station in the south-west of China. The results show that the automatic recognition method can fully and quickly automatically identify most of the important structural planes and their position, dip, dip angle and gap width and other characteristic parameter information in the entire borehole image. The recognition rate of the main structural plane is about 90%. The accuracy rate is about 85%, the total time cost is about 3 h, and the accuracy deviation is less than 4% among the 12 boreholes with a depth of about 50 m. The application of automatic recognition technology to the panoramic borehole image can greatly improve work efficiency, reduce the time cost, and avoid the interference caused by humans, making it possible to automatically recognize the structural plane parameters of the full-hole image.

Monitoring small magnitude induced seismicity requires a dense network of seismic stations and high-quality recordings in order to precisely determine events’ hypocentral parameters and mechanisms. However, microseismicity (e.g. swarm activity) can also occur in an area where a dense network is unavailable and recordings are limited to a few seismic stations at the surface. In this case, using advanced event detection techniques such as template matching can help to detect small magnitude shallow seismic events and give insights about the ongoing process at the subsurface giving rise to microseismicity. In this paper, we study shallow microseismic events caused by hydrofracking of the PNR-2 well near Blackpool, UK, in 2019 using recordings of a seismic network which was not designed to detect and locate such small events. By utilizing a sparse network of surface stations, small seismic events are detected using template matching technique. In addition, we apply a full-waveform moment tensor inversion to study the focal mechanisms of larger events (ML > 1) and used the double-difference location technique for events with high-quality and similar waveforms to obtain accurate relative locations. During the stimulation period, temporal changes in event detection rate were in agreement with injection times. Focal mechanisms of the events with high-quality recordings at multiple stations indicate a strike-slip mechanism, while a cross-section of 34 relocated events matches the dip angle of the active fault., Karlsruher Institut für Technologie (KIT) (4220), https://earthquakes.bgs.ac.uk/data/broadband_stationbook.html

This study analyzes the flux transfer event (FTE)-type flux ropes and magnetic reconnection around the dayside magnetopause during BepiColombo’s Earth flyby. The magnetosheath corresponds to a high plasma β (~ 8) and the IMF has a significant radial component. Six flux ropes are identified. The motion of flux rope together with the maximum magnetic shear model suggests that the reconnection X-line swipes BepiColombo near the magnetic equator due to an increase of the radial IMF. The flux rope with the highest flux content contains a clear coalescence signature, i.e., two smaller flux ropes merging, supporting theoretical predictions the flux content of flux ropes can grow through coalescence. The secondary reconnection associated with coalescence exhibits a large normalized guide field and a reconnection rate comparable to the reconnection rate measured at the magnetopause (~ 0.1).

The terrain conditions and geological structure of the mountainous areas in western China are complex. To meet the design requirements for the expressway, the route adopts the design of deep-buried super-long tunnels in hilly areas. If the highway tunnel passes through faulty structures, such as improper selection of structure and foundation form, it can cause collapse and structural instability during construction. Therefore, basic characteristics of faults and information that is more accurate should be provided during the survey process to avoid subsequent problems. The frequency and magnitude of earthquakes in this study area are high and available data show that the Xiaojiang fault was still active during the Quaternary Holocene period, which is a high-risk area for earthquakes. Therefore, a set of comprehensive technologies, such as geophysical prospecting, geological survey, and drilling, and was used to identify faults and their characteristics and to visually display underground information within a certain depth range. Here, the magnetotelluric method was used to analyze the electrical characteristics and structure of the highway tunnel. In addition, the electrical characteristics and structure of the Xiaojiang fault were discussed. Geological surveys and drilling agree well with the analysis and interpretation of the research results and further proposed a processing and interpretation method for correcting the dip angle of the fault using the statistical results from the long axis dip angle of the tensor polarization map for the wave impedance. Thus, a large amount of information in the tunnel site can be effectively obtained for predicting and evaluating the Xiaojiang fault. Furthermore, our results provide strong technical support for designing and operating highway tunnels, with meaningful experience and reference for future geophysical processing and interpretation.

A tomographic analysis of Mt. Pollino area (Italy) has been performed using earthquakes recorded in the area during an intense seismic sequence that occurred between 2010 and 2014. 870 local earthquakes with magnitude ranging from 1.8 to 5.0 were selected considering the number of recording stations, the signal quality, and the hypocenter distribution. P- and S-wave arrival times were manually picked and used to compute 3D velocity models through tomographic seismic inversion. The resulting 3D distributions of VP and VS are characterized by high resolution in the central part of the investigated area and from surface to about 10 km below sea level. The aim of the work is to obtain high-quality tomographic images to correlate with the main lithological units that characterize the study area. The results will be important to enhance the seismic hazard assessment of this complex tectonic region. These images show the ductile Apennine platform (VP = 5.3 km/s) overlaying the brittle Apulian platform (VP = 6.0 km/s) at depth of around 5 km. The central sector of the area shows a clear fold and thrust interface. Along this structure, most of the seismicity occurred, including the strongest event of the sequence (MW 5.0). High VP (>6.8 km/s) and high VP/VS (>1.9) patterns, intersecting the southern edge of this western seismogenic volume, have been interpreted as water saturated rocks, in agreement with similar geological context in the Apennines. These fluids could have played a role in nucleation and development of the seismic sequence. A recent study revealed the occurrence of clusters of earthquakes with similar waveforms along the same seismogenic volume. The hypocenters of these cluster events have been compared with the events re-located in this work. Jointly, they depict a 10 km × 4 km fault plane, NW-SE oriented, deepening towards SW with a dip angle of 40–45°. Instead, the volume of seismicity responsible for the ML 4.3 earthquake developed as a mainshock-aftershock sequence, occurring entirely within the average-to-low VP/VS Apennine platform. Our results agree with other independent geophysical analyses carried out in this area, and they could significantly improve the actual knowledge of the main lithologic units of this complex tectonic area.

The numerous effects of adjacent structures should be considered in the design and construction of subway stations. The subway station expansion project confined to a small space in Shenzhen City was taken as engineering background to study the earth pressure distribution in a limited space. Both theoretical analysis and laboratory model testing methods were used to study the mechanical behavior of the subway station retaining structure adjacent to a pile foundation. The main conclusions are as follows: (1) When the soil around the foundation pit is non-cohesive, the soil pressure is smaller than that calculated by classical soil pressure theory, and the difference between the two increases with an increase in the angle of internal friction. If the lateral inclination continues to increase, then the pressure will approach the value determined by classical theory. (2) The soil pressure distribution and variation rule are greatly influenced by factors such as the length-diameter ratio, excavation depth, internal friction angle and friction between the soil and retaining structure. The dip angle of the sliding surface of the finite soil increases with decreasing friction angle and is inversely correlated with the aspect ratio. The active soil pressure is inversely proportional to the internal friction angle of the soil and positively correlated with height. When the internal friction angle is constant and the length–diameter ratio is equal to the critical length–diameter ratio, the active earth pressure coefficient is equal to the Coulomb active earth pressure coefficient and reaches its maximum value. (3) The deformation of the foundation pit retaining structure has an important influence on the distribution of soil pressure around it. These results offer a reference for the engineering design and construction of supporting structures for deep foundation pits adjacent to existing adjacent structures.

Jointed rock mass has special discontinuous structure, which shows complex anisotropic mechanical properties. In order to grasp the complex mechanical properties, a group of joint rock specimens with different dip angles were made by similar ratio to carry out uniaxial compression tests, and the peak strength of the rock specimens and their variation with dip angles β were obtained. The peak failure modes of the specimens were analyzed. The results show that the mechanical properties of the specimens are controlled by joint surface and rock block. Compared with the intact specimens, the mechanical parameters of the joint specimens are all reduced to varying degrees, and the compressive strength of the joint specimens is U-shaped with the joint inclination Angle, and the minimum value appears in the specimens with the joint inclination Angle of 60°.When the joint dip Angle is \(\beta = 0^\circ\sim{3}0^\circ\), the fracture failure along the axial stress direction occurs. When the joint dip Angle is \(\beta >45^\circ \), the rock begins to slip along the bedding plane. When the joint inclination Angle is \(\beta =90^\circ \), splitting failure along the bedding plane occurs. The research results can provide reference for engineering deformation and stability analysis of jointed rock mass.

In this paper, we analyzed low latitude geoelectric field variations and Geomagnetically Induced Current ( $$GIC$$ ), associated with disturbed geomagnetic field variations in West Africa. For this purpose, variations of geomagnetic field components $$H$$ , $$D$$ and $$Z$$ , and geoelectric field horizontal components $$Ey$$ and $$Ex$$ were examined during geomagnetically disturbed periods, with the daily means of the Ap index higher than 20 nT. Variations of geoelectric field components $$Ey$$ and $$Ex$$ were identified as associated with disturbed variations of the geomagnetic field. The $$GIC$$ was estimated from the observed $$Ey$$ and $$Ex$$ based on system parameters configuration with $$a = b = 50~\,{\text{A}}\,{\text{km/V}}$$ . The disturbance fluctuations in the geoelectric field components and the estimated GIC exhibit a diurnal trend, with higher amplitudes during the daytime. The impulses in the geoelectric field components and the estimated $$GIC$$ are stronger in the southern stations than in the northern stations. On the average, these impulses decrease from LAM to TOM, with a slight enhancement near the magnetic equator.

An inverse modelling study on the interpretation of magnetic anomalies caused by 2D dyke-shaped bodies was carried out using the differential search algorithm (DSA), a novel metaheuristic inspired by the migration of super-organisms. We aimed at estimating dyke parameters that include amplitude coefficient, depth, half-width, origin and dip angle. First, the resolvability of these parameters and algorithm-dependent parameters of the DSA that affect the performance were determined. Two theoretical and two field anomalies were used in the evaluations. Theoretical anomalies comprise one and two isolated dykes. The effect of noise content was also investigated in these cases. The inversion approach was then applied to two known magnetic field anomalies measured over the Marcona iron mine in Peru and the Pima copper mine in the US state of Arizona. The results showed that the efficiency of the DSA increases significantly with the use of optimal parameter sets of the inverse magnetic problem. Furthermore, cost function maps and relative frequency histograms showed that the parameters half-width and amplitude can be estimated with some uncertainties, while the remaining significant model parameters of the source body can be solved with negligible uncertainties. Findings indicated that the DSA provided satisfactory solutions in accordance with actual data and previously obtained results. Thus, it can be concluded that DSA is an efficient tool for interpreting magnetic anomalies caused by magnetised 2D dykes.

Systems, methods, and apparatuses for generating a subsurface image using diffraction energy information are disclosed. The systems, methods, and apparatuses may include converting a shot gather into one or more plane-wave gather using a Radon transform. The plane-wave gathers may be extrapolated into source-side wavefields and receiver-side wavefields and further generate a pseudo dip-angle gather. The diffraction energy information may be extracted from the pseudo dip-angle gather, and an image containing subsurface features may be generated from the extracted diffraction energy information. The receiver-side wavefields may be decomposed using a recursive Radon transform.

Pervasive, unavoidable and uncontrollable creep failure generated in soft-rock engineering occasionally happens and therefore attracts extensive attention recently. However, due to soft rock’s multi-factor creep mechanism, it is still difficult to simulate the full-stage creep with the Distinct Element Method (DEM). In this study, we proposed an improved simulation method based on the classical Burger’s model and the Parallel Bonded model in Particle Flow Code (PFC). We apply the abovementioned models together to simulate the full-stage creep process in soft rock. The proposed process has considered the mesoscopic mechanical characteristics of DEM carefully and finally resulted in a parallel physical model, which is called Burger’s Bonded model in this paper. The DEM simulation test using Burger’s Bonded model was designed to compare with experiments. The experiments include a normal creep test and a uniaxial loading test with prefabricated cracks. In contrast to experimental results, the numerical results show that the average error during the whole creep process is less than 3%, the stress–strain curves and crack development process show great agreement. It is also found that the wing crack coalescence in soft rock is independent of the prefabricated crack angle, propagating with a fixed dip angle. The results show that the numerical method proposed in this paper can simulate the multi-factor-caused full stage (attenuated, steady, accelerated) creep process of soft rock in DEM, which provides new insights for theoretical research and engineering design.

We investigate the response of the ionosphere-thermosphere coupled system to the 22-23 June 2015 geomagnetic storm in the region above the Oukaimeden observatory in Morocco with a Fabry-Perot interferometer and the Swarm satellites. The measured thermospheric neutral winds are strong enough to have two direct consequences. First, they create a strong asymmetry in the equatorial ionisation crests on both sides of the magnetic equator (actually, they make the southern hemisphere crest disappear). This asymmetry is explained by the southerly thermospheric neutral wind that was blowing during the storm and is shown to be favoured by the season. Second, within the northern hemisphere ionisation crest, Swarm A and C detect km-size electron density structures. Those may be ascribed to gradient drift instability.

The cables of high-strength carbon fiber reinforced polymer (CFRP) plates are starting to be applied to large spatial structures. However, their main anchorage systems rely on the adhesive force, which entails risks to their integrity resulting from aging of the binding agent. In this study, a friction-based wedge anchorage system was designed for CFRP plates. The working mechanism of the proposed anchorage system was explored both theoretically and experimentally. The anti-slip mechanism and condition of CFRP plates were formulated so that the equivalent frictional angle of the contact surface between a CFRP plate and wedges must not be smaller than the sum of the dip angle of the wedge external conical surface and the frictional angle between the wedges and barrel. An analysis of the stress distribution in the anchorage zone of the CFRP plate was conducted using the Tsai-Wu failure criterion, which concluded that the compressive stresses should be reduced on the section closer to the load-bearing end of the anchorage system. Furthermore, the anchorage efficiency coefficient was proposed, which depends on stress concentration coefficients, plate thickness, length of anchorage zone, dip angle of wedge external conical surface, and its frictional angle. Then, it was determined that the minimum length of an anchorage zone for the CFRP plates with various specifications should be at least 49 times larger than the CFRP thickness. A finite element analysis and static tensile tests on six specimens were carried out. The experimental results revealed that the anchorage efficiency coefficient of the optimized anchor reached 97.9%.

Accretionary wedge earthquakes usually occur in the overriding crust close to the trench or above the cold nose of the mantle wedge. However, the mechanism and temperature properties related to the slab dip angle remain poorly understood. Based on 3D thermal models to estimate the subduction wedge plate temperature and structure, we investigate the distribution of wedge earthquakes in Alaska, which has a varying slab dip angle along the trench. The horizontal distance of wedge-earthquake hypocenters significantly increases from the Aleutian Islands to south–central Alaska due to a transition from steep subduction to flat subduction. Slab dehydration inside the subducted Pacific plate indicates a simultaneous change in the distances between the intraslab metamorphic fronts and the Alaskan Trench at various depths, which is associated with the flattening of the Pacific plate eastward along the strike. The across-arc width of the wedge-earthquake source zone is consistent with the across-arc width of the surface high topography above the fully dehydrated megathrust, and the fluid upwelling spontaneously influences wedge seismotectonics and orogenesis.

The calculation of deformation parameters of stratified rock mass is crucial to the deformation and stability evaluation of bedrock/surrounding rock in large projects like hydropower stations. In practice, these parameters are generally determined through in situ test on small rock mass or rock blocks. This strategy cannot reflect the influence of rock properties, directivity, and structural difference on deformation parameters. Based on the elastic theory, this paper derives the calculation formulas for the deformation parameters of stratified rock mass, and verifies them through large-scale in situ deformation tests. The results show that the theoretical solution to the deformation parameters of the stratified rock mass basically agrees with the results of the in situ tests. The deformation parameters of stratified rock mass have clear orthogonal anisotropy; the deformation moduli under the load parallel to stratum strike are always greater than that vertical to stratum strike. The dip angle of rock layer also affects the parameter anisotropy: when the dip angle is greater than 45°, vertical deformation moduli are greater than horizontal deformation moduli; when the dip angle is smaller than 45°, vertical deformation moduli are smaller than horizontal deformation moduli. The smaller the dip angle, the more prominent the influence of loading direction over the parameter anisotropy; the greater the difference in rock mass parameters, the more obvious that influence. Our model provides a desirable tool for researchers dealing with the anisotropy of deformation parameters of stratified rock mass.

Shale oil and gas fields usually contain many horizontal wells. The key of 3D structural modeling for shale reservoirs is to effectively utilize all structure-associated data (e.g., formation tops) in these horizontal wells. The inclination angle of horizontal wells is usually large, especially in the lateral section. As a result, formation tops in a horizontal well are located at the distinct lateral positions, while formation tops in a vertical well are usually stacked in the same or similar lateral position. It becomes very challenging to estimate shale layer thickness and structural map of multiple formation surfaces using formation tops in horizontal wells. Meanwhile, the large inclination angle of horizontal wells indicates a complicated spatial relation with shale formation surfaces. The 3D structural modeling using horizontal well data is much more difficult than that using vertical well data. To overcome these new challenges in 3D structural modeling using horizontal well data, we developed a method for 3D structural modeling using horizontal well data. The main process included 1) adding pseudo vertical wells at formation tops to convert the uncoupled formation tops to coupled formation tops as in vertical wells, 2) estimating shale thickness by balancing the shale thickness and dip angle change of a key surface, and 3) detecting horizontal well segments landing in the wrong formations and adding pseudo vertical wells to fix them. We used our improved method to successfully construct two structural models of Longmaxi–Wufeng shale reservoirs at a well pad scale and a shale oil/gas field scale. Our research demonstrated that 3D structural modeling could be improved by maximizing the utilization of horizontal well data, thus optimizing the quality of the structural model of shale reservoirs.

This study examines the ionosphere response to gravitational forces of the lunar phase and dynamical disturbances of the stratospheric sudden warmings (SSWs). The total electron content (TEC) of global ionosphere maps is employed to examine responses of the equatorial ionization anomaly (EIA) crests to lunar phases and twelve SSW events during 2000–2013. The most prominent feature in the ionosphere is the EIA, characterized by two enhanced TEC crests at low latitudes straddling the magnetic equator, which can be used to observe ionospheric plasma dynamics and structures. Results show that the EIA crest appearance time on new/full moons (first/third quarters) leads (lags) that of the overall 14-year average, which causes a pattern of TEC morning enhancements (suppressions) and afternoon suppressions (enhancements). A statistical analysis shows that SSWs can also significantly cause the early appearance of EIA crests, regardless of the lunar phase. Thus, both lunar phase and SSWs can significantly modulate the appearance time of EIA crest and ionospheric plasma dynamics and structures.

To solve the problem that the covering device of sugarcane cannot be adequate for the agronomic standards of seed cane setts planting, a soil-covering and film-mulching device for sugarcane transverse planting was designed. The device includes a soil-covering part, soil-compacting part, and film-mulching part. Through theoretical analysis of key components, the factors affecting the cane seed covering quality for the device were obtained. A quadratic orthogonal rotation regression test was conducted by a homemade prototype to explore the effects of disk diameter, central distance, disk depth in soil, and dip angle on soil covering thickness. The results showed that the above factors all have an extremely significant effect on the soil covering thickness, and the effect degree of each factor from high to low is central distance, disk depth in soil, dip angle, and disk diameter within the range of test parameters. The optimal parameter combination, with the disk diameter, the dip angle, the central distance, the disk depth in soil, and the diameter of the soil-compacting wheel being 304.7 mm, 55.1°, 386.5 mm, 32.4 mm, and 300 mm, respectively, was obtained by Design-Expert software and verified by comprehensive field tests. The results showed that the covering thickness is in the range of 94–111 mm, the average value is 102.6 mm, and the breakage rate is no more than 2.6%. The emergence rate is 86.4%, which is an improvement of 9.3% over that of a traditional covering device. The results suggested that the device can conform to the agricultural covering standard of sugarcane planting and provide a design basis for the application and popularization of the soil-covering and film-mulching device.

Fault-crossing tunnels are often severely damaged under seismic dynamics. Study of the dynamic response characteristics of tunnels crossing faults is thus of great engineering significance. Here, the Xianglushan Tunnel of the Central Yunnan Water Diversion Project was studied. A shaking table experimental device was used, and four sets of dynamic model tests of deep-buried tunnels with different fault inclination angles were conducted. Test schemes of model similarity ratio, similar material selection, model box design, and sine wave loading were introduced. The acceleration and strain data of the tunnel lining were monitored. Analysis of the acceleration data showed that when the input PGA was 0.6 g, compared with the ordinary tunnel, the acceleration increases by 117% when the inclination angle was 75°, 127% when the inclination angle was 45°, and 144% when the inclination angle was 30°. This indicates that the dynamic response of the cross-fault tunnel structure was stronger than that of the ordinary tunnel, and the effect was more obvious as the fault dip angle decreased. Analysis of the strain data showed that the strain response of the fault-crossing tunnels was more sensitive to the fault dip. The peak strain and increase in fault-crossing tunnels were much larger than those of ordinary tunnels, and smaller fault dips led to larger increases in the strain peak, consequently, the tunnel would reach the ultimate strain and break down when the input PGA was smaller. Generally, the influence of fault inclination on the dynamic response of the tunnel lining should receive increased consideration in the seismic design of tunnels.

Light detection and ranging (LiDAR) can quickly and accurately obtain 3D point clouds on the surface of rock masses, and on the basis of this, discontinuity information can be extracted automatically. This paper proposes a new method to automatically extract discontinuity information from 3D point clouds on the surface of rock masses. This method first applies the improved K-means algorithm based on the clustering algorithm by fast search and find of density peaks (DPCA) and the silhouette coefficient in the cluster validity index to identify the discontinuity sets of rock masses, and then uses the hierarchical density-based spatial clustering of applications with noise (HDBSCAN) algorithm to segment the discontinuity sets and to extract each discontinuity from a discontinuity set. Finally, the random sampling consistency (RANSAC) method is used to fit the discontinuities and to calculate their parameters. The 3D point clouds of the typical rock slope in the Rockbench repository is used to extract the discontinuity orientations using the new method, and these are compared with the results obtained from the classical approach and the previous automatic methods. The results show that, compared to the results obtained by Riquelme et al. in 2014, the average deviation of the dip direction and dip angle is reduced by 26% and 8%, respectively; compared to the results obtained by Chen et al. in 2016, the average deviation of the dip direction and dip angle is reduced by 39% and 40%, respectively. The method is also applied to an artificial quarry slope, and the average deviation of the dip direction and dip angle is 5.3° and 4.8°, respectively, as compared to the manual method. Furthermore, the related parameters are analyzed. The study shows that the new method is reliable, has a higher precision when identifying rock mass discontinuities, and can be applied to practical engineering.

The Baiyanghe block in Fukang, Xinjiang, China, is rich in coalbed methane (CBM) resources, and several pilot experimental wells have yielded high production. Due to the high dip angle (35–55°) of the coal seam in this area, the lack of understanding of the geological characteristics, the physical properties of coal, and gas–water migration law lead to immature development techniques and poor overall development benefits. We first conducted desorption and adsorption tests on low-rank coal of this area and found residual gas in the coal. We established a coalbed methane desorption model suitable for this area by modifying the isotherm adsorption model. Next, by analyzing the influence of the gas–water gravity differentiation in the high–dip angle coal seam and the shallow fired coalbed methane characteristics in this area, we discovered the leakage of CBM from the shallow exposed area of the coal seam. Given the particular physical property of coal and gas–water migration characteristics in this area, we optimized the well pattern: (i) the U-shaped along-dip horizontal well group in coal seams is the main production well for gas production with a spacing distance of 312 m; (ii) a multistage fracturing well drilled in the floor of coal is for water production; and (iii) vertical wells with a spacing distance of 156 m in the shallow area is to capture CBM leakage. Using numerical simulation and net present value (NPV) economics models, we optimized the well pattern details. Applying our CBM desorption model, the numerical simulator can improve the accuracy of the low-rank coalbed methane productivity forecast. The optimization results demonstrated the following: 1) the cumulative gas production of single U-shaped well increased by 89% with the optimal well spacing, 2) the cumulative gas production of the well group increased by 87.54% after adding the floor staged horizontal well, and 3) the amount of CBM leakage decrease by 67.59%.

The need to accurately interpret geological models that approximate mineralized zones in a Basement Complex terrain necessitate the development of horizon loop electromagnetic method (HLEM) forward modeling solutions for such scenarios. The focus of the present work is on finding rapid forward modeling solutions for synthetic HLEM data as an aid in exploration for moderate to deep conductive mineral exploration targets.The main thrust is obtaining idealized HLEM models that are required for geological interpretation of the subsurface in such environment. The original HLEM equations developed by Wesley were extended to represent a horizontally stratified earth with a conductive approximated by shear zone. From these equations a computer program was written to calculate the HLEM responses for optimal conductor model with known values of coil separations (L), depth of burial (z) and angle of dip of the target.The thin conductive model was used because it is simple and suitable for different geological scenarios. The accuracy of the approximate forward solution has been confirmed for HLEM systems with various geometric ranges, frequencies and conductivities. Three models having varying overburden thickness, dip angle of target and source-receiver separation were used in the forward modeling. The effect of varying the dip angle,overburden thickness and coil separation was studied in all the three models used. The result obtained from the forward modeling showed that variation of the dip angle gave rise to changes in the amplitudes of the anomalies generated, while that of overburden and coil separation gave rise to changes in anomaly shape. Also, the geometry and position of the causative body were precisely delineated.

On 2 December 2020, a moderate and shallow Mw = 4.6 earthquake occurred in Boeotia (Central Greece) near the city of Thiva. Despite its magnitude, the co-seismic ground deformation field was detectable and measurable by Sentinel-1, ascending and descending, synthetic aperture interferometry radar (InSAR) acquisitions. The closest available GNSS station to the epicenter, located 11 km west, measured no deformation, as expected. We proceeded to the inversion of the deformation source. Moreover, we reassessed seismological data to identify the activated zone, associated with the mainshock and the aftershock sequence. Additionally, we used the rupture plane information from InSAR to better determine the focal mechanism and the centroid location of the mainshock. We observed that the mainshock occurred at a shallower depth and the rupture then expanded downdip, as revealed by the aftershock distribution. Our geodetic inversion modelling indicated the activation of a normal fault with a small left-lateral component, length of 2.0 km, width of 1.7 km, average slip of 0.2 m, a low dip angle of 33°, and a SW dip-direction. The inferred fault top was buried at a depth of ~0.5 km, rooted at a depth of ~1.4 km, with its geodetic centroid buried at 1.0 km. It was aligned with the Kallithea fault. In addition, the dip-up projection of the modeled fault to the surface was located very close (~0.4 km SW) to the mapped (by existing geological observations) trace of the Kallithea fault. The ruptured area was settled in a transition zone. We suggest the installation of at least one GNSS and seismological station near Kallithea, as the activated zone (inferred by the aftershock sequence and InSAR results) could yield events with M≥5.0, according to empirical laws relating to rupture zone dimensions and earthquake magnitude.

Despite the growing knowledge on geomagnetic paleosecular variations, the region around the Philippine archipelago remains to be a huge data gap in this regard. This work looked into rock magnetic information from

SUMMARY Accurate identification of the locations and orientations of small-scale faults plays an important role in seismic interpretation. We have developed a 3-D migration scheme that can image small-scale faults using diffractions in time. This provides a resolution beyond the classical Rayleigh limit of half a wavelength in detecting faults. The scheme images weak diffractions by building a modified dip-angle gather, which is obtained by replacing the two dip angles dimensions of the conventional 2-D dip-angle gather with tangents of the dip angles. We build the modified 2-D dip-angle gathers by calculating the tangents of dip angles following 3-D prestack time migration (PSTM). In the resulting modified 2-D dip-angle gathers, the Fresnel zone related to the specular reflection exhibits an ellipse. Comparing with the conventional 2-D dip-angle gather, diffraction event related a fault exhibits a straight cylinder shape with phase-reversal across a line related the orientation of the fault. As a result, we can not only mute the Fresnel zones related to reflections, correct phase for edge diffractions and obtain the image of faults, but also detect the orientations of 3-D faults using the modified dip-angle gathers. Like the conventional dip-angle gathers, the modified dip-angle gathers can also be used to image diffractions resulting from other sources. 3-D Field data tests demonstrate the validity of the proposed diffraction imaging scheme.

The rock structure and three-dimensional stress state play a vital role in the mechanical behaviour of rock masses. Here, a series of true triaxial compression tests (σ1 > σ2 > σ3) are conducted on jointed marble (50 × 50 × 100 mm3) containing a natural stiff joint, taken from the China Jinping Underground Laboratory (CJPL-II) project. The purposes of this study are to investigate the joint effect and estimate the stress dependency of jointed marble. The test results show that jointed marble can fail in four distinct forms, namely, splitting or shearing of intact marble, opening of the joint or sliding along the joint, and these failure modes are influenced by the joint configuration and the minimum and intermediate principal stresses. Generally, jointed marble has more brittle post-peak behaviour than intact marble. The linear Mogi-Coulomb failure criterion can be modified to describe the strength of the jointed marble under true triaxial compression. The jointed marble strength is more sensitive to the minimum principal stress than to the intermediate principal stress. A maximum decline of 25% in strength is observed, which corresponds to a joint dip angle of 60° at σ2 = 60 MPa and σ3 = 30 MPa. The link between the experimental results and in situ fracturing at CJPL-II is also demonstrated.

The brittleness prediction of shale formations is of interest to researchers nowadays. Conventional methods of brittleness prediction are usually based on isotropic models while shale is anisotropic. In order to obtain a better prediction of shale brittleness, our study firstly proposed a novel brittleness index equation based on the Voigt–Reuss–Hill average, which combines two classical isotropic methods. The proposed method introduces upper and lower brittleness bounds, which take the uncertainty of brittleness prediction into consideration. In addition, this method can give us acceptable predictions by using limited input values. Secondly, an anisotropic rock physics model was constructed. Two parameters were introduced into our model, which can be used to simulate the lamination of clay minerals and the dip angle of formation. In addition, rock physics templates have been built to analyze the sensitivity of brittleness parameters. Finally, the effects of kerogen, pore structure, clay lamination and shale formation dip have been investigated in terms of anisotropy. The prediction shows that the vertical/horizontal Young’s modulus is always below one while the vertical/horizontal Poisson’s ratio (PR) can be either greater or less than 1. Our study finds different degrees of shale lamination may be the explanation for the random distribution of Vani (the ratio of vertical PR to horizontal PR).

Based on well logging responses, sedimentary patterns and sandstone thickness, the distribution characteristics of meandering river sedimentary sand body of Neogene Minghuazhen Formation NmIII2 layer in the west of Shijiutuo Bulge, Chengning Uplift, Bohai Bay Basin were investigated. A new approach to calculate the occurrence of the sand-mudstone interfaces using resistivity log of horizontal well was advanced to solve the multiple solution problem of abandoned channel's orientation. This method uses the trigonometric function relationship between radius, dip and length of the resistivity log to calculate the occurrence qualitatively – quantitatively to help determine the true direction of the abandoned channels. This method can supplement and improve the architecture dissection technique for meandering river sandbodies. This method was used to study the dip angle and scale of the lateral accretion layers in point bar quantitatively to help determine the spatial distribution of lateral accretion layers. The fine architecture model of underground meandering river reservoir in the study area has been established. Different from traditional grids, different grid densities for lateral accretion layers and bodies were used in this model by non-uniform upscaling to establish the inner architecture model of point-bars and realize industrial numerical simulation of the whole study area. The research results can help us predict the distribution of remaining oil, tap remaining oil, and optimize the waterflooding in oilfields. Key words: Bohai Bay Basin, meandering river, horizontal well resistivity curve, lateral accretion layers, lateral accretion bodies, architecture modeling, remaining oil distribution

The prevention and forecast of coal and gas outburst has always been one of the key issues in coal mining safety. By simulating the process of tunneling in coal seam with different dip angle through FLAC3D software, the dangerous zone in which outburst may occur and the probability of outburst near the working face were predicted through the distribution of stress, displacement and plastic zone. Then we discussed the size of unstable area in the surrounding rock through the distribution of stress and the variation curve of the displacement on the roadway wall. The results show that, with an increase of the coal seam dip angle, the risk of outburst in the working face rises gradually. And the dangerous areas in which may outburst occur moves to the upper part of coal seam. The size of unstable area in the surrounding rock increases with the increase of coal seam dip angle.

Walkaway VSP cannot obtain accurate velocity field, as it asymmetrically reflects ray path and provides uneven coverage to underground target, thereby presenting issues related to imaging quality. In this study, we propose combining traveltime tomography and prestack depth migration for VSP of an angle-domain walkaway, in a bid to establish accurate two-dimensional and three-dimensional (3D) velocity models. First, residual curvature was defined to update velocity, and an accurate velocity field was established. To establish a high-precision velocity model, we deduced the relationship between the residual depth and traveltime of common imaging gathers (CIGs) in walkaway VSP. Solving renewal velocity using the least squares method, a four-parameter tomographic inversion equation was derived comprising formation dip angle, incidence angle, residual depth, and sensitivity matrix. In the angle domain, the reflected wave was divided into up- and down-transmitted waves and their traveltimes were calculated. The systematic cumulative method was employed in prestack depth migration of a complex surface. Through prestack depth migration, the offset-domain CIGs were obtained, and dip angle was established by defining the stack section horizon. Runge—Kutta ray tracing was employed to calculate the ray path from the reflection point to the detection point, to determine the incident angle, and to subsequently calculate the ray path from the reflection point to the irregular surface. The offset-domain residual depths were mapped to the angle domain, and a new tomographic equation was established and solved. Application in the double complex area of the Tarim Basin showed the four-parameter tomographic inversion equation derived in this paper to be both correct and practical and that the migration algorithm was able to adapt to the complex surface.

The main purpose of this research is to evaluate the effect of coal seam dip on the front abutment and side abutment stresses distribution around the longwall panels by FLAC3D software. For this purpose numerical modeling of five longwall panels in coal seam with dip angle of 0, 12, 22, 32 and 42 degree have been done. The results of numerical modeling have been shown that in all models, peak value of front abutment stress was found to act at a distance about 1–3 m in front of the panel face and the difference between this stresses in front of the working face is about 9.7 MPa. In this distance, the peak vertical stress is in the order of approximately 4–5 times the in-situ stress and then gradually decreases toward the initial field stress. Moreover numerical modeling results have been shown that increasing coal seam dip has no significant effect on the peak value of side abutment stress at the edge of pillar, but the side abutment stress concentration is nearer to the edge of pillar. At coal seam dip of zero and 12 degrees, maximum vertical stress occurs at a distance of 5.4 m from the pillar edge, whereas at the coal seam dip of 42 degrees, this stress occurs within 3 m of the pillar edge. However, increasing the dip of coal seam caused to increase entry roof displacement. The results are in good agreement with field observation.

Accurate modeling of fractures is a matter of growing scientific interest. Several existing methods for 3D fractures modeling are available only for oversimplified geometries, e.g. rectangle. The identification of intersections of complex polygonal fractures with dip angles has not been clearly resolved, which results in inaccurate grid transmissibility calculation between fracture cells. This study aims at obtaining an efficient modeling strategy for 3D fractures with arbitrary spatial distributions and field-scale fracture modeling application. The dimensionality reduction method based on coordinate transformation is employed to identify the intersections of arbitrary shaped polygon fractures with any dip angles. Meanwhile, fine grid cells are generated in the vicinity of fractures to adapt high-pressure gradients, which is favorable to the simulation accuracy. For another, the local refinement allows transitions of cell sizes from the near-fracture region to far-fracture region, reducing grid number and further computational cost. The model validation is given in a tailored case where Cartesian grids are used to model vertical fractures with a local grid refinement by the industry-reference simulator ECLIPSE-E100 and a good match is achieved by our model. Three complex examples with different fracture densities are computed to demonstrate the robustness and stability of the simulator. The influence of 3D fracture parameters on the oil production, including the height, dip angle, area and shape, is analyzed.

In an effort to explore the morphology of nighttime spread F at the lower mid-latitude European station of Nicosia, Cyprus (35°N, 33°E geographic; magnetic dip. 29.38°N), all ionograms recorded by the DPS-4D digisonde during the interval 2009–2016 have been analyzed. Subsequent detailed investigation was performed to establish the possible effect of various triggering mechanisms on spread F within the framework of Perkins instability on a statistical basis by correlating spread F occurrence particular wave pattern signatures (Satellite Trace/Multiple-reflected Echoes), gravity wave signatures, F layer uplift (h'F) and unstable sporadic E layers. The results verify the systematic manifestation and therefore the significance of TIDs and unstable sporadic E layers as triggering factors responsible for seeding spread F development and underline the frequent appearance of multi-reflected echoes and satellite traces as dominant precursors of mid-latitude spread F over European latitudes for the first time. Furthermore clear seasonal characteristics and inverse solar activity dependence of spread F occurrence in lower European mid-latitudes is established similar to southern hemisphere studies undertaken previously.

This work reports an experiment/simulation combination study on the magnetorheological (MR) mechanism of magnetic fluid based on Fe3O4 hollow chains. The decrease of shear stress versus the increasing magnetic field was observed in a dilute magnetic fluid. Hollow chains exhibited a higher MR effect than pure Fe3O4 hollow nanospheres under a small magnetic field. A modified particle level simulation method including the translational and rotational motion of chains was developed to comprehend the correlation between rheological properties and microstructures. Sloping cluster-like microstructures were formed under a weak external field (24 mT), while vertical column-like microstructures were observed under a strong field (240 mT). The decrease of shear stress was due to the strong reconstruction process of microstructures and the agglomeration of chains near the boundaries. The chain morphology increased the dip angle of microstructures and thus improved the MR effect under a weak field. This advantage made Fe3O4 hollow chains to be widely applied for small and low-power devices in the biomedical field. Dimensionless viscosity as a function of the Mason number was collapsed onto linear master curves. Magnetic fluid in Poiseuille flow in a microfluidic channel was also observed and simulated. A qualitative and quantitative correspondence between simulations and experiments was obtained.

A mechanical model for the tilted workface floor along the tilted direction of coal seam was proposed. Stress expressions of an arbitrary point inside the tilted workface floor were deduced. Calculation formula for the maximum failure depth of the lateral floor strata of the tilted workface was also deduced. Based on the Mohr-Coulomb yield criterion, the tilted workface floor’s stress distribution, and failure depth and shape were simulated by using FLAC3D software for different coal seam’s dip angles, buried depths, and workface widths. Results show that the concentration coefficient, the peak value and the distance between the peak position of the lateral abutment pressure and the roadway on both sides of the tilted workface decreases with the increases in coal seam’s dip angle. The vertical stress isoclines present a “spoon-shaped” distribution along the tilted direction of workface. Both sides of the workface form “bubble-shaped” distribution shear stress and its peak value increases first and then decreases with the increases in coal seam’s dip angle and reaches maximum at 30°–35°. The tilted workface floor’s plastic failure zone presents a “spoon-shaped” distribution along the tilted direction of workface, which is large on the lower side and small on the upper side. The plastic zone’s failure depth increases first and then decreases with the increases in the dip angle of coal seam and reaches maximum at 30°.

In the mine fire period, the smoke plume temperature, critical air velocity, back-flow layer and other fire parameters in the lanes are subjected to environmental factors such as lane dip angle and...

The Jiaojia-type gold deposits, hosting >80% of gold resource in the Jiaodong Peninsula, Eastern China, are characterized by veinlet- and disseminated-style mineralization associated with the Mesozoic detachment faults. In this study, we performed multi-constraint geological modeling and spatial analysis involving 3D buffer analysis, shape analysis, and field analysis for the Dayingezhuang gold deposit to quantitatively assess the gold distribution and its association with geological features. The obtained spatial data were further integrated into three dimensional (3D) prospectivity modeling by fuzzy weights-of-evidence (WofE) and continuous WofE methods to evaluate mineral potential. Our results determine a quantitative correlation between phyllic alteration thickness and tectono-geochemical anomaly to construct the geometric models of alteration zone. The hydrothermal intensity extracted from the models shows a bimodal distribution and it is significantly high in the center of No. 2 orebodies, indicating an overprinting gold mineralization. The spatial analysis on the Zhaoping fault reveals that the most probable locations for gold deposition were determined to be in segments of the Zhaoping fault with a slope of 20° to 40°, dip angle changes of −5°, and undulation of near 0 m. All of the features likely result from structural controls on fluid flow and infiltration, as well as variations in the stability of Au-bearing complexes related to fault morphology. 3D prospectivity models generated by continuous transformed spatial evidence values with lower bias and uncertainty yielded a higher predictive efficiency than classified evidential layers. Our study not only highlights that gold enrichment of the Jiaojia-type deposit is essentially controlled by shape features of detachment faults, but also emphasizes the applicability of 3D prospectivity modeling in identifying potential gold mineralization at depth in the Jiaodong Peninsula.

Disposable blood collection needles become severely intertwined and hooked during stacking, and thus individually feeding disposable blood collection needles during mechanical packaging is difficult. Based on the physical characteristics of the blood collection needles during the stacking state, this study designed an automatic tidying and sorting mechanism by combining compound vibration, sorting, and conveying. During the feeding process, the compound vibration-type material-tidying mechanism tidies 20‒30 blood collection needles first; then, the material sorting and conveying mechanism transports the tidied blood collection needles individually. The orthogonal testing of the automatic material tidying process shows that various experimental factors are ranked by the significance level of the effect on the tidying process and the significance ranking is as follows: vertical vibration frequency > horizontal amplitude > vertical amplitude > horizontal vibration frequency. Experiments were performed after analyzing the optimal combination. The results demonstrate that when the horizontal vibration frequency is 1.7 Hz, the horizontal amplitude is 150 mm, vertical vibration frequency is 1.3 Hz, vertical amplitude is 30 mm, and material length after tidying is 265 mm. The automatic sorting and conveying experiment shows the effect of various experimental factors on the feed rate of the material, where the significance level of the effect is ranked as follows: vibration frequency > material quantity > channel dip angle. The experimental results show that when the number of materials is 25, the channel dip angle is 12°, and vibration frequency is 52.5 Hz. The material delivery efficiency reaches 0.51 s/root, meeting the requirement of five channels for 80000 root/day feeding efficiency. The study can provide reference for the realization of automatic feeding of large aspect ratio flexible materials in similar stacking state.

The problem of an unsteady squeezing flow of fluid between two parallel plates under the influence of an inclined magnetic field is analyzed. The longitudinal inclination angle of the applied magnetic field varies from 0 to 90 degrees. Viscous dissipation, Joule heating and the stretching velocity of the lower plate with suction or injection are also taken into account. The transformed nonlinear governing equations are solved numerically by a fourth-order Runge-Kutta scheme coupled with the shooting method. Impacts of the squeeze number, the magnetic parameter, the magnetic inclination angle, the lower-plate stretching parameter, the lower-plate suction/injection parameter and Eckert number on the velocity and temperature are pointed out, respectively. It is found that the inclination angle of the applied magnetic field also plays an important role in the velocity and heat transfer in squeezing flows. The influence of changing the magnetic field strength on the velocity and temperature can also be approximately achieved by adjusting the inclination angle of the applied magnetic field.

Surrounding rock control is problematic at irregular fully-mechanized working faces of inclined seams. This study investigated the evolution of mining-induced stress at a variable-length working face under different coal seam inclination angles by using FLAC3D software to establish an experimental model based on the occurrence conditions of the inclined seam and the layout of fully-mechanized working face in the western district of Pan’er mine in China. Analysis of the simulation data was used to determine the stress evolution of working face in the strike and dip directions under different dip angle conditions and reveal the relationship between mining stress evolution and coal seam inclination. Comparative analysis of the formation and evolution of mining-induced stress before and after the roadway connection was used to determine the mechanisms behind mining-induced stress evolution in the short face to long face connection process and to reveal asymmetrical differences in the mining-induced stress evolution of the upper, middle and lower parts of the coal seam along the dip direction. Based on the relationship between supports and surrounding rock, the structure of hydraulic powered supports, the entry arrangement and supporting characteristics, control methods to ensure the stability of surrounding rock are proposed such as a metal mesh above hydraulic powered supports and reinforcement at the junction. These measures are effective for preventing partial roof fall and rib spalling, loss of support stability and stress concentration at connecting entry and for achieving safe and efficient mining of irregular working faces in thick inclined seams.

Morphology of the subducting Indian lithosphere beneath Tibet is the key to understanding the tectonic evolution of the Tibetan plateau. In the present study we determine three-dimensional P-wave velocity images of the mantle under the entire Tibetan plateau and its adjacent areas by inverting ~200,000 teleseismic relative travel-time residuals recorded at 893 stations belonging to >32 portable seismic networks deployed in and around the plateau. An east-west varying high-velocity anomaly with a large dip angle down to the mantle transition zone is revealed clearly, which represents the subducting Indian slab. On the basis of the tomographic results, we propose a slab warping model to describe the complex subduction of the Indian plate beneath the plateau, which is characterized by lateral bending in addition to downward subduction. The complex geometry of the present Indian slab is possibly caused by non-uniform pulling of an earlier subducted slab in a process with the Indian slab detachment propagating laterally. As a result, a warping arc has formed beneath the Himalaya block to keep the Indian lithosphere intact. This slab warping model agrees well with many observations, such as magmatism and surface deformations in the western and southern Tibetan plateau.