With the rapid development of deep resource extraction and underground space construction,the design of anchored support systems for jointed rock masses in complex stress environments faces significant challenges.This...With the rapid development of deep resource extraction and underground space construction,the design of anchored support systems for jointed rock masses in complex stress environments faces significant challenges.This study investigates the influence of prefabricated crack dip angles on the mechanical properties of anchored rock masses in deep soft rock roadways.By constructing similarity models of NPR(Negative Poisson’s Ratio)and PR(Positive Poisson’s Ratio)anchored solids,biaxial compression experiments under varying crack dip angles were conducted.Strain gauges,3D Digital Image Correlation(3D DIC),and acoustic emission monitoring were employed to systematically analyze the strength characteristics,deformation-damage evolution,and energy dissipation mechanisms of the two types of anchor systems.The results show that:(1)The stress-strain curves of anchored solids with prefabricated cracks exhibit a distinct bimodal characteristic.Compared to PR anchors,NPR anchors show 20%and 23%improvements in peak strength and elastic modulus,respectively,with residual strength enhanced by up to 34%.(2)Owing to high pre-tightening force and large deformation capacity,NPR anchors maintain superior integrity under increasing crack dip angles,demonstrating more uniform free-surface displacement and localized shear-tensile composite crack patterns.(3)Acoustic emission analysis reveals that NPR anchors exhibit higher cumulative energy absorption(300%improvement over PR anchors)and lack low-rate energy development phases,indicating enhanced ductility and impact resistance at high crack dip angles.(4)Crack dip angle critically governs failure mechanisms by modulating the connectivity between shear cracks and prefabricated fissures:bimodal effects dominate at low angles,while vertical tensile crack propagation replaces bimodal behavior at high angles.The study proposes prioritizing NPR anchor cables in deep engineering applications and optimizing support parameters based on crack dip angles to mitigate stress concentration and ensure the long-term stability of surrounding rock.展开更多
Island-arc magmatism is a crucial process in the Earth’s crustal growth.However,how the island-arc magma production rate(MPR)changes and the key influencing factors remains unclear.This study employs numerical models...Island-arc magmatism is a crucial process in the Earth’s crustal growth.However,how the island-arc magma production rate(MPR)changes and the key influencing factors remains unclear.This study employs numerical models to simulate island-arc growth,incorporating slab dehydration,mantle hydration and melting,and melt extraction.In addition,the impacts of convergence rate and slab dip angle on island-arc magma production were studied.Results suggest that,(1)MPR increases with higher convergence rates;high convergence rates enhance slab water transport efficiency and mantle wedge convection,thereby promoting water fraction and temperature in potential molten regions;(2)MPR initially rises and then falls as the slab dip angle varies from 30°to 45°,and to 60°.This variation is closely tied to water content in the wedge rather than mantle temperature.However,a higher slab dip promotes dehydration towards the potential-melting mantle wedge,which causes water to ascend to shallow areas and reduces the area of the potential molten region.Ultimately,a dip angle of 45°is optimal for retaining the most suitable water fraction and mantle wedge area,thereby maintaining the largest MPR;(3)convergence rate variation has a much larger influence on magma production rate than dip angle variation.When the convergence rate varies from 2 to 10 cm/a,the largest time-averaged MPR is 64.0 times the smallest one,whereas when the slab dip varies from 30°to 60°,the largest time-averaged MPR is only 3.5 times the smallest one.These findings align with numerous instances observed in modern-day subduction zones.展开更多
When mining the fully-mechanized longwall caving face along strike, the unstable equipment, the low top-coal recovery ratio and the difficulty in controlling surrounding rock may occur due to large dip angle. Consider...When mining the fully-mechanized longwall caving face along strike, the unstable equipment, the low top-coal recovery ratio and the difficulty in controlling surrounding rock may occur due to large dip angle. Considering the effects of strike angle on support stability, the ‘‘support-surrounding rock"mechanical models of support topple and support slip were established in this paper. On the basis, the influencing factors of support stability were analyzed and the technical measures of controlling support and surrounding rock stability were put forward. Then the loose particles simulation experiment was conducted to analyze the impacts of caving directions and methods on the top-coal recovery in large dip angle fully-mechanized caving face. Finally, the ‘‘upward sequence and double-openings doublerounds" caving technology was determined. The research results are of great scientific significance and practical values to improve large dip thick seam mining technology.展开更多
The flow behavior of liquefied sand is reported using a self-developed testing system that enables the flow processes of liquefied sand to be studied at different slopes of the soil layers.The test device is mainly co...The flow behavior of liquefied sand is reported using a self-developed testing system that enables the flow processes of liquefied sand to be studied at different slopes of the soil layers.The test device is mainly composed of a vibrating table,a transparent model box and a high-speed video monitoring camera.The tests replicated the horizontal and sloping flows of saturated sand in the model box,which can be tilted to various angles to study the flow characteristics of liquefied sand.The high-speed video monitoring camera captured and recorded the processes within the flowing sand.With increasing downslope,the strain,strain rate,duration time,and sand flow distance increased.The results of our experiment indicate that when selecting sites for engineering structures,the surface downslopes should be taken into account if liquefiable soils are present.Finally,some suggestions regarding site assessment and structural design for sites prone to liquefaction were presented.展开更多
The origin of arcuate islands and deep-sea trenches has been studied for a long time and various interpretations have been proposed. In this paper, some analytical models are put forward from a geometrical viewpoint a...The origin of arcuate islands and deep-sea trenches has been studied for a long time and various interpretations have been proposed. In this paper, some analytical models are put forward from a geometrical viewpoint and then the theoretical dip angles of the underthrusting slabs of circum-Pacific island arcs are computed and compared with those of the Benioff zone. As a result, it is found that the dip angle of the underthrusting slab is one of the main factors determining the curvature of the arcuate structure. The authors consider that this result may contribute to the plate theory.展开更多
On the basis of the shape and inner structure of volcanic edifice,the dip angle and coherence were selected to recognize the buried volcanic edifices in Songliao Basin.Five volcanic edifices were recognized in both tw...On the basis of the shape and inner structure of volcanic edifice,the dip angle and coherence were selected to recognize the buried volcanic edifices in Songliao Basin.Five volcanic edifices were recognized in both two methods in the first volcanic cycle of Yingcheng Formation and the prediction perfectly corresponds to the drilling results in well XS8 area.The results are satisfying when the prediction method were employed in the exploration and development of Qingshen gas field.展开更多
In rock mass and mining engineering,shock waves induced by engineering disturbances significantly affect rock mass stability.To explore the dynamic mechanical behavior and energy dissipation mechanisms of single-fract...In rock mass and mining engineering,shock waves induced by engineering disturbances significantly affect rock mass stability.To explore the dynamic mechanical behavior and energy dissipation mechanisms of single-fractured composite rock masses under impact loading,a series of tests were conducted using a split Hopkinson pressure bar(SHPB)system with a 50 mm rod diameter.Specimens containing a single inclined fracture with seven different dip angles and located in different lithological layers were tested.The results show that both peak stress and peak strain exhibit a non-monotonic trend with increasing dip angleα-first decreasing,then increasing,reaching a minimum atα=45°.This behavior is attributed to enhanced energy concentration and dissipation in the fracture zone,where shear-dominated failure leads to more effective crack propagation and stress redistribution.Moreover,the proportion of crushing energy dissipation is significantly affected by the fracture dip angle,reaching a minimum atα=45°and a maximum atα=90°,indicating a transition from shear to tensile failure modes with increasing angle.Lithology also plays a crucial role:grey sandstone specimens absorbed more energy compared to yellow sandstone,implying higher impact resistance due to differences in microstructural cohesion.The evolution of fragment fractal dimension with increasing dip angle follows an"M-shaped"trend,reflecting changes in fragmentation intensity and failure mode.Notably,yellow sandstone tends to produce higher fractal dimensions,with larger mass but smaller volume of powdered debris,indicating more intense fragmentation.This study reveals the coupling effect of fracture dip angle and lithology on dynamic mechanical response and energy evolution,providing new insights into the failure mechanisms of layered composite rock masses under impact loading.展开更多
In this study,to better decide the effect of coal seam dip angle upon the dynamic change of the crossfusion in gas transport and storage areas during the progress of working face in the high gas thick coal seam,a two-...In this study,to better decide the effect of coal seam dip angle upon the dynamic change of the crossfusion in gas transport and storage areas during the progress of working face in the high gas thick coal seam,a two-dimensional physical simulation experiment regarded as the theoretical research was conducted to properly explore the variation law of overburden fracture.The results demonstrated that the boundary of the gas transport zone was located in the region of fracture separation.The boundary of the gas storage area was located in the abrupt penetration zone.Also,according to the information theory,the state of the gas transport and storage areas was determined by the changing trend of the fracture rate and fracture entropy.The mathematical representation model of the dip effect in gas transport and storage areas was established.The criteria upon which the regional location of the gas transport area and gas storage area can be based were put forward.The cross-fusion evolution process of the dip effect in gas transport and storage areas was revealed as well.The research results could provide guidance for realising directional and accurate gas extraction.展开更多
Slopes consisting of interbedded strata of soft and hard rock mass, such as purplish red mudstone and grey brown arkosic sandstone of Jurassic age, are very common in Sichuan basin of China. The mudstone is soft whil...Slopes consisting of interbedded strata of soft and hard rock mass, such as purplish red mudstone and grey brown arkosic sandstone of Jurassic age, are very common in Sichuan basin of China. The mudstone is soft while the sandstone is hard and contains many opening or closing joints with a high dip angle. Some are nearly parallel and the others are nearly decussated with the trend of the slopes. Many natural slopes are in deformation or sliding because of those reasons. The stability of cutting slopes and supporting method to be taken for their stability in civil engineering are important. In this paper, the stability and deformation of the slopes are studied. The methods of analysis and support design principle are analyzed also. Finally, the method put forward is applied to study Fengdian high cutting slope in Sichuan section of the express way from Chengdu to Shanghai. The results indicate that the method is effective.展开更多
It is inevitable to encounter fault zones in tunnel construction.These faults can lead to significant deformations and potential collapses of the surrounding rock in the tunnel.Therefore,it is crucial to study the inf...It is inevitable to encounter fault zones in tunnel construction.These faults can lead to significant deformations and potential collapses of the surrounding rock in the tunnel.Therefore,it is crucial to study the influence of different fault angles on tunnel deformation.The Tabaiyi Tunnel,located in Yunnan Province of China passes through a multi-stage fault zone.The dynamic response characteristics of the surrounding rock in the Tabaiyi Tunnel were studied under various fault dip angles and the most unfavorable angle was identified.Physical model tests were conducted using two types of anchor cables with specific parameters.Additionally,a relationship between the engineering rock mass and energy absorption by the anchor cables was established,demonstrating the advantages of negative Poisson's ratio(NPR)anchor cables.Experimental results indicate that stress concentration tends to occur at the junctions between faults and the surrounding rock mass.Tunnels supported by NPR anchor cables effectively mitigate amplification effects,achieving energy absorption increases of up to 87%compared to positive Poisson's ratio(PR)anchor cables.Furthermore,the highest acceleration amplification was observed at a fault dip angle of 45°,with peak acceleration reaching twice that of the original input wave,indicating that this angle should be avoided in tunnel design.These findings provide valuable insights for the safe management of tunnels traversing fault zones.展开更多
A series of true triaxial unloading tests are conducted on sandstone specimens with a single structural plane to investigate their mechanical behaviors and failure characteristics under different in situ stress states...A series of true triaxial unloading tests are conducted on sandstone specimens with a single structural plane to investigate their mechanical behaviors and failure characteristics under different in situ stress states.The experimental results indicate that the dip angle of structural plane(θ)and the intermediate principal stress(σ2)have an important influence on the peak strength,cracking mode,and rockburst severity.The peak strength exhibits a first increase and then decrease as a function ofσ2 for a constantθ.However,whenσ2 is constant,the maximum peak strength is obtained atθof 90°,and the minimum peak strength is obtained atθof 30°or 45°.For the case of an inclined structural plane,the crack type at the tips of structural plane transforms from a mix of wing and anti-wing cracks to wing cracks with an increase inσ2,while the crack type around the tips of structural plane is always anti-wing cracks for the vertical structural plane,accompanied by a series of tensile cracks besides.The specimens with structural plane do not undergo slabbing failure regardless ofθ,and always exhibit composite tensile-shear failure whatever theσ2 value is.With an increase inσ2 andθ,the intensity of the rockburst is consistent with the tendency of the peak strength.By analyzing the relationship between the cohesion(c),internal friction angle(φ),andθin sandstone specimens,we incorporateθinto the true triaxial unloading strength criterion,and propose a modified linear Mogi-Coulomb criterion.Moreover,the crack propagation mechanism at the tips of structural plane,and closure degree of the structural plane under true triaxial unloading conditions are also discussed and summarized.This study provides theoretical guidance for stability assessment of surrounding rocks containing geological structures in deep complex stress environments.展开更多
Cyclic changes in the internal pressure of compressed air energy storage reservoirs in abandoned coal mines result in complex alternating loads on the rocks surrounding the energy storage reservoirs.These complex alte...Cyclic changes in the internal pressure of compressed air energy storage reservoirs in abandoned coal mines result in complex alternating loads on the rocks surrounding the energy storage reservoirs.These complex alternating loads can be regarded as multi-stage constant-amplitude cyclic loads following simplification.In this paper,the mechanical responses and acoustic emission(AE)characteristics of red sandstone with five bedding dip angles(0°,30°,45°,60°,and 90°)under such loads are investigated,and the damage evolution processes of the five specimens are revealed from both quantitative and microscopic perspectives.The results show that the fatigue deformation characteristics of the specimens are affected by the bedding dip angle.Under cyclic loads,the axially irreversible plastic deformations of the rocks increase,their elastic stiffness increases,their crack volumetric strain increases and then decreases,and their AE cumulative count/energy curves exhibit a ladder shape.A damage evolution model based on the crack volumetric strain is proposed,and the damage evolution process is divided into two stages:a rapid increase stage and a tendency toward stabilization stage.Through cluster analysis,the AE events are used to classify the damage into three categories:small-sized localized damage,large-sized tensile damage,and large-sized shear damage.Finally,the MohreCoulomb criterion is applied to analyze the relationship between the failure modes of the red sandstone specimens and the dip angle of the bedding.The results of this study will help to predict the stability and safety of compressed air energy storage reservoirs in abandoned coal mines.展开更多
The paper goal is to analyze the variability of foF2 at African equatorial stations and the effect of dip angle on this variability. The gap between the dip angle of Dakar and Ouagadougou is superior to that between D...The paper goal is to analyze the variability of foF2 at African equatorial stations and the effect of dip angle on this variability. The gap between the dip angle of Dakar and Ouagadougou is superior to that between Djibouti and Ouagadougou. The trend of the dip angle at Ouagadougou and Dakar decreases while that of Djibouti increases. The relative position of the station with respect to the equator and the trend sign explains the difference observed in foF2 variability at Dakar station and at the two other stations. At Djibouti and Ouagadougou, foF2 exhibits noon bite out profile during all solar cycle phases while at Dakar observed profile is dome or plateau during the maximum and the predominance afternoon peak for the other solar cycle phases.展开更多
To study the damage and failure of shale with different fracture inclination angles under uniaxial compression loading,in this work,RFPA2D-Thermal,a two-dimensional real failure process analysis software,was used for ...To study the damage and failure of shale with different fracture inclination angles under uniaxial compression loading,in this work,RFPA2D-Thermal,a two-dimensional real failure process analysis software,was used for numerical simulation.Numerical simulation results show that quartz in shale mainly affects the tensile and compressive strength of shale by increasing rock brittleness.The coupling of temperature and pressure will cause lateral and volume destruction of shale,which enables the shale body to be more easily broken.Fracture inclination is the key factor affecting shale damage patterns.The failure mode of shale with low-and high-angle fractures is mainly shear failure,and the compressive strength does not vary with crack inclination.The damage mode of obliquely intersecting fractured shale is slip damage along the fracture face,the compressive strength decreases and then increases with the fracture inclination,and a minimum value exists.The acoustic emission simulation results of the damage process effectively reflect the accumulated internal damage and macroscopic crack appearance until fracture instability when the prefabricated fractured shale is subjected to uniaxial compressive loading.The crack inclinations of 0°and 120℃ corresponds to the most complex"N"shape damage mode.The crack inclinations of 30°and 60°,and the damage mode is an inverted"λ"shape.展开更多
The 2015 Gorkha Earthquake in Nepal and the 2008 Wenchuan Earthquake in China occurred at the south and southeast margins of the Tibetan Plateau, respectively. Both earthquakes had similar magnitudes of Mw 7.8 and 7.9...The 2015 Gorkha Earthquake in Nepal and the 2008 Wenchuan Earthquake in China occurred at the south and southeast margins of the Tibetan Plateau, respectively. Both earthquakes had similar magnitudes of Mw 7.8 and 7.9, caused catastrophic loss of life and damage to property, and generated tens of thousands of landslides. Comparisons of pre-and post-quake satellite images supported by field investigations show that the Gorkha Earthquake triggered at least 2 064 large landslides （defined as covering an area ≥10 000 m2） over a -35 600 km2 region with a volume of （444-584）×10^6 （average 509×10^6） m3 and total area of 44.78×10^6 m2. In contrast, the Wenchuan Earthquake triggered 25 580 large landslides over a region of -44 000 km2 with a volume of （7 128-9 479）×10^6 （average 8 219×10^6） m3 and a total area of about 670.65×10^6 m2. Several controlling factors including topographic relief, slope steepness, and regional peak ground acceleration （PGA） were investigated to try to explain the great differences between the number, volume and area of the coseismic landslides associated with the two similar earthquakes. We found that the differences primarily arose from an unexpected factor, the dip angle of the seismogenic fault. This discovery should aid understanding the failure mechanisms of quake-triggered landslides, and suggests that more factors should be taken into consideration in estimating coseismic landslide volumes from earthquake magnitudes. KEY WORDS： Gorkha Earthquake, Wenchuan Earthquake, landslide, dip angle, seismogenic fault.展开更多
Using the double-difference relocation algo- rithm, we relocated the 20 April 2013 Lushan, Sichuan, earthquake （Ms 7.0）, and its 4,567 aftershocks recorded during the period between 20 April and May 3, 2013. Our res...Using the double-difference relocation algo- rithm, we relocated the 20 April 2013 Lushan, Sichuan, earthquake （Ms 7.0）, and its 4,567 aftershocks recorded during the period between 20 April and May 3, 2013. Our results showed that most aftershocks are relocated between 10 and 20 km depths, but some large aftershocks were relocated around 30 krn depth and small events extended upward near the surface. Vertical cross sections illustrate a shovel-shaped fault plane with a variable dip angle from the southwest to northeast along the fault. Furthermore, the dip angle of the fault plane is smaller around the mainshock than that in the surrounding areas along the fault. These results suggest that it may be easy to generate the strong earthquake in the place having a small dip angle of the fault, which is somewhat similar to the genesis of the 2008 Wenchuan earthquake. The Lushan mainshock is underlain by the seismically anomalous layers with low-Vp, low-Vs, and high-Poisson＇s ratio anomalies, possibly suggesting that the fluid-filled fractured rock matrices might signifi- cantly reduce the effective normal stress on the fault plane to bring the brittle failure. The seismic gap between Lushan and Wenchuan aftershocks is suspected to be vulnerable to future seismic risks at greater depths, if any.展开更多
The irregularity of jointed network poses a challenge to the determination of field mechanical param-eters of columnar jointed rock mass(CJRM),and a reasonable prediction of deformation and strength characteristics of...The irregularity of jointed network poses a challenge to the determination of field mechanical param-eters of columnar jointed rock mass(CJRM),and a reasonable prediction of deformation and strength characteristics of CJRM is important for engineering construction.The Voronoi diagram and three-dimensional printing technology were used to make an irregular columnar jointed mold,and the irregular CJRM(ICJRM)specimens with different dip directions and dip angles were prepared.Uniaxial compression tests were performed,and the anisotropic strength and deformation characteristics of ICJRM were described.The failure modes and mechanisms were revealed in accordance with the final appearances of the ICJRM specimens.Based on the model test results,the empirical correlations for determining the field deformation and strength parameters of CJRM were derived using the dip angle and modified joint factor.The proposed empirical equations were used in the Baihetan Project,and the calculated mechanical parameters were compared with the field test results and those obtained from the tunneling quality index method.Results showed that the deformation parameters determined by the two proposed methods are all consistent with the field test results,and these two methods can also estimate the strength parameters effectively.展开更多
To quantitatively determine the effect of different factors such as fracture width,dip angle,extension and filling material on Stoneley wave amplitude decreasing,the shock tube experiment method was changed from fixin...To quantitatively determine the effect of different factors such as fracture width,dip angle,extension and filling material on Stoneley wave amplitude decreasing,the shock tube experiment method was changed from fixing the sample and vertically moving the sensor in the borehole to fixing the sensors along the shock tube wall and vertically moving the sample without drilling the borehole in it.The measurement accuracy and the signal-to-noise ratio of the first Stoneley wave were improved by the time corrections and amplitude corrections of Stoneley wave signals.At the same time,21 sets of core models with different fracture parameters were processed for this measurement method by using full-diameter carbonate core,and relative amplitudes were defined to characterize Stoneley wave amplitude decreasing.The experimental results show that the relative amplitude of Stoneley wave exponentially decreases with increasing fracture width.The relative amplitude of Stoneley wave linearly decreases with increasing fracture dip angle.The relative amplitude of Stoneley wave exponentially decreases with increasing fracture extension.The relative amplitude of Stoneley wave decreases with increasing the permeability of filling material in the fracture.Under the above four conditions,the fracture width has the greatest effect on the decreasing of Stoneley wave amplitude,followed by the fracture extension and the permeability of filling material,and finally the fracture dip angle.展开更多
The maximum distance at which an electromagnetic(EM)logging while drilling(LWD)tool detects an approaching boundary is defined as the depth of detection(DOD).Ultra-deep detection capability of the transient multicompo...The maximum distance at which an electromagnetic(EM)logging while drilling(LWD)tool detects an approaching boundary is defined as the depth of detection(DOD).Ultra-deep detection capability of the transient multicomponent EM logging measurement is investigated here.First,we adopt sine and cosine transform to calculate the transient multicomponent responses.Compared to the cosine transform,sine transform is more accurate in solving late-time responses.Then,a time-domain geosignal is introduced to sense the boundary.Results show that DOD of this transient EM measurement can be up to tens of meters,including directionally sensitivity.Additionally,by studying the decay characteristics of different components with time,cross component is confirmed to decay much faster than the coaxial/coplanar components in the formation coordinate system.A pseudo-inversion is thereby proposed to determine the dip angle of anisotropic stratified formation.Theoretical simulation results indicate that this algebraic method can determine the true dip at some particular moments.It is still stable and valid even when considering random measurement errors.Moreover,we establish the linear relationship between the time at which the half-point of geosignal curve appears and the distance to boundary(DTB),which would assist in the quick determination of DTB.展开更多
The attenuation relationship of ground motion based on seismology has always been a front subject of engineering earthquake.Among them,the regional finite-fault source model is very important.In view of this point,the...The attenuation relationship of ground motion based on seismology has always been a front subject of engineering earthquake.Among them,the regional finite-fault source model is very important.In view of this point,the general characteristics of regional seism-tectonics,including the dip and depth of the fault plane,are emphasized.According to the statistics of regional seism-tectonics and focal mechanisms in Sichuan,China,and the sensitivity of estimated peak ground acceleration(PGA)attenuation is analyzed,and the dip angle is taken as an average of 70°.Based the statistics of the upper crustal structure and the focal depth of regional earthquakes,the bottom boundary of the sedimentary cover can be used as the upper limit for estimating the depth of upper-edge.The analysis shows that this value is sensitive to PGA.Based on the analysis of geometric relations,the corresponding calculation formula is used,and a set of concepts and steps for building the regional finite-fault source model is proposed.The estimation of source parameters takes into account the uncertainty,the geometric relationship among parameters and the total energy conservation.Meanwhile,a set of reasonable models is developed,which lay a foundation for the further study of regional ground motion attenuation based on seismology.展开更多
基金supported by the National Natural Science Foundation of China(Grant Nos.52174096 and 52304110).
文摘With the rapid development of deep resource extraction and underground space construction,the design of anchored support systems for jointed rock masses in complex stress environments faces significant challenges.This study investigates the influence of prefabricated crack dip angles on the mechanical properties of anchored rock masses in deep soft rock roadways.By constructing similarity models of NPR(Negative Poisson’s Ratio)and PR(Positive Poisson’s Ratio)anchored solids,biaxial compression experiments under varying crack dip angles were conducted.Strain gauges,3D Digital Image Correlation(3D DIC),and acoustic emission monitoring were employed to systematically analyze the strength characteristics,deformation-damage evolution,and energy dissipation mechanisms of the two types of anchor systems.The results show that:(1)The stress-strain curves of anchored solids with prefabricated cracks exhibit a distinct bimodal characteristic.Compared to PR anchors,NPR anchors show 20%and 23%improvements in peak strength and elastic modulus,respectively,with residual strength enhanced by up to 34%.(2)Owing to high pre-tightening force and large deformation capacity,NPR anchors maintain superior integrity under increasing crack dip angles,demonstrating more uniform free-surface displacement and localized shear-tensile composite crack patterns.(3)Acoustic emission analysis reveals that NPR anchors exhibit higher cumulative energy absorption(300%improvement over PR anchors)and lack low-rate energy development phases,indicating enhanced ductility and impact resistance at high crack dip angles.(4)Crack dip angle critically governs failure mechanisms by modulating the connectivity between shear cracks and prefabricated fissures:bimodal effects dominate at low angles,while vertical tensile crack propagation replaces bimodal behavior at high angles.The study proposes prioritizing NPR anchor cables in deep engineering applications and optimizing support parameters based on crack dip angles to mitigate stress concentration and ensure the long-term stability of surrounding rock.
基金Supported by the National Natural Science Foundation of China(Nos.42176068,42476063,92058213,42376081,42121005)。
文摘Island-arc magmatism is a crucial process in the Earth’s crustal growth.However,how the island-arc magma production rate(MPR)changes and the key influencing factors remains unclear.This study employs numerical models to simulate island-arc growth,incorporating slab dehydration,mantle hydration and melting,and melt extraction.In addition,the impacts of convergence rate and slab dip angle on island-arc magma production were studied.Results suggest that,(1)MPR increases with higher convergence rates;high convergence rates enhance slab water transport efficiency and mantle wedge convection,thereby promoting water fraction and temperature in potential molten regions;(2)MPR initially rises and then falls as the slab dip angle varies from 30°to 45°,and to 60°.This variation is closely tied to water content in the wedge rather than mantle temperature.However,a higher slab dip promotes dehydration towards the potential-melting mantle wedge,which causes water to ascend to shallow areas and reduces the area of the potential molten region.Ultimately,a dip angle of 45°is optimal for retaining the most suitable water fraction and mantle wedge area,thereby maintaining the largest MPR;(3)convergence rate variation has a much larger influence on magma production rate than dip angle variation.When the convergence rate varies from 2 to 10 cm/a,the largest time-averaged MPR is 64.0 times the smallest one,whereas when the slab dip varies from 30°to 60°,the largest time-averaged MPR is only 3.5 times the smallest one.These findings align with numerous instances observed in modern-day subduction zones.
基金provided by the National Key Basic Research Program of China (973 Program) (No. 2015CB251600)the Qing Lan Projectthe Priority Academic Program Development of Jiangsu Higher Education Institutions (PAPD)
文摘When mining the fully-mechanized longwall caving face along strike, the unstable equipment, the low top-coal recovery ratio and the difficulty in controlling surrounding rock may occur due to large dip angle. Considering the effects of strike angle on support stability, the ‘‘support-surrounding rock"mechanical models of support topple and support slip were established in this paper. On the basis, the influencing factors of support stability were analyzed and the technical measures of controlling support and surrounding rock stability were put forward. Then the loose particles simulation experiment was conducted to analyze the impacts of caving directions and methods on the top-coal recovery in large dip angle fully-mechanized caving face. Finally, the ‘‘upward sequence and double-openings doublerounds" caving technology was determined. The research results are of great scientific significance and practical values to improve large dip thick seam mining technology.
基金supported by the National Natural Science Foundation of China(No.41831291)。
文摘The flow behavior of liquefied sand is reported using a self-developed testing system that enables the flow processes of liquefied sand to be studied at different slopes of the soil layers.The test device is mainly composed of a vibrating table,a transparent model box and a high-speed video monitoring camera.The tests replicated the horizontal and sloping flows of saturated sand in the model box,which can be tilted to various angles to study the flow characteristics of liquefied sand.The high-speed video monitoring camera captured and recorded the processes within the flowing sand.With increasing downslope,the strain,strain rate,duration time,and sand flow distance increased.The results of our experiment indicate that when selecting sites for engineering structures,the surface downslopes should be taken into account if liquefiable soils are present.Finally,some suggestions regarding site assessment and structural design for sites prone to liquefaction were presented.
文摘The origin of arcuate islands and deep-sea trenches has been studied for a long time and various interpretations have been proposed. In this paper, some analytical models are put forward from a geometrical viewpoint and then the theoretical dip angles of the underthrusting slabs of circum-Pacific island arcs are computed and compared with those of the Benioff zone. As a result, it is found that the dip angle of the underthrusting slab is one of the main factors determining the curvature of the arcuate structure. The authors consider that this result may contribute to the plate theory.
基金Supported by NSFC Project No 40372066,and SRFDP No 20030183042
文摘On the basis of the shape and inner structure of volcanic edifice,the dip angle and coherence were selected to recognize the buried volcanic edifices in Songliao Basin.Five volcanic edifices were recognized in both two methods in the first volcanic cycle of Yingcheng Formation and the prediction perfectly corresponds to the drilling results in well XS8 area.The results are satisfying when the prediction method were employed in the exploration and development of Qingshen gas field.
基金financially supported by the National Natural Science Foundation of China(No.52204137)the Outstanding Young Scientific and Technological Talents Project of Liaoning University of Science and Technology(NO.2023YQ10)+3 种基金the Education Department Foundation of Liaoning Province(NO.LJKQZ20222317)the Natural Science Foundation of Shandong Province(Grant No.ZR2020QE121,ZR202211080074)the upport Program for Youth Innovation and Entrepreneurship in Higher Education Institutions of Shandong Province(Grant No.2022KJ101)the Support Program for Youth Innovation and Entrepreneurship in Higher Education Institutions of Shandong Province(Grant No.2022KJ101)。
文摘In rock mass and mining engineering,shock waves induced by engineering disturbances significantly affect rock mass stability.To explore the dynamic mechanical behavior and energy dissipation mechanisms of single-fractured composite rock masses under impact loading,a series of tests were conducted using a split Hopkinson pressure bar(SHPB)system with a 50 mm rod diameter.Specimens containing a single inclined fracture with seven different dip angles and located in different lithological layers were tested.The results show that both peak stress and peak strain exhibit a non-monotonic trend with increasing dip angleα-first decreasing,then increasing,reaching a minimum atα=45°.This behavior is attributed to enhanced energy concentration and dissipation in the fracture zone,where shear-dominated failure leads to more effective crack propagation and stress redistribution.Moreover,the proportion of crushing energy dissipation is significantly affected by the fracture dip angle,reaching a minimum atα=45°and a maximum atα=90°,indicating a transition from shear to tensile failure modes with increasing angle.Lithology also plays a crucial role:grey sandstone specimens absorbed more energy compared to yellow sandstone,implying higher impact resistance due to differences in microstructural cohesion.The evolution of fragment fractal dimension with increasing dip angle follows an"M-shaped"trend,reflecting changes in fragmentation intensity and failure mode.Notably,yellow sandstone tends to produce higher fractal dimensions,with larger mass but smaller volume of powdered debris,indicating more intense fragmentation.This study reveals the coupling effect of fracture dip angle and lithology on dynamic mechanical response and energy evolution,providing new insights into the failure mechanisms of layered composite rock masses under impact loading.
基金supported by the National Natural Science Foundation of China(No.5217-4205)Shaanxi Provincial Outstanding Youth Science Fund Project(No.2023-JC-JQ-40)+4 种基金National Key Research and Development Project(No.2023YFC3009004)Key Project of Shaanxi Provincial Department of Education(No.22JY040)Xinjiang Uygur Autonomous Region Key Research and Development Task Special Project(No.2022B01034-3)Key Laboratory of Green Coal Mining in Xinjiang,Ministry of Education(No.KLXGY-KA2404)Shaanxi Provincial Key Research and Development Task General Project(No.2024GX–YBXM-490)。
文摘In this study,to better decide the effect of coal seam dip angle upon the dynamic change of the crossfusion in gas transport and storage areas during the progress of working face in the high gas thick coal seam,a two-dimensional physical simulation experiment regarded as the theoretical research was conducted to properly explore the variation law of overburden fracture.The results demonstrated that the boundary of the gas transport zone was located in the region of fracture separation.The boundary of the gas storage area was located in the abrupt penetration zone.Also,according to the information theory,the state of the gas transport and storage areas was determined by the changing trend of the fracture rate and fracture entropy.The mathematical representation model of the dip effect in gas transport and storage areas was established.The criteria upon which the regional location of the gas transport area and gas storage area can be based were put forward.The cross-fusion evolution process of the dip effect in gas transport and storage areas was revealed as well.The research results could provide guidance for realising directional and accurate gas extraction.
文摘Slopes consisting of interbedded strata of soft and hard rock mass, such as purplish red mudstone and grey brown arkosic sandstone of Jurassic age, are very common in Sichuan basin of China. The mudstone is soft while the sandstone is hard and contains many opening or closing joints with a high dip angle. Some are nearly parallel and the others are nearly decussated with the trend of the slopes. Many natural slopes are in deformation or sliding because of those reasons. The stability of cutting slopes and supporting method to be taken for their stability in civil engineering are important. In this paper, the stability and deformation of the slopes are studied. The methods of analysis and support design principle are analyzed also. Finally, the method put forward is applied to study Fengdian high cutting slope in Sichuan section of the express way from Chengdu to Shanghai. The results indicate that the method is effective.
基金funded by the National Natural Science Foundation of China(Grant No.42377154).
文摘It is inevitable to encounter fault zones in tunnel construction.These faults can lead to significant deformations and potential collapses of the surrounding rock in the tunnel.Therefore,it is crucial to study the influence of different fault angles on tunnel deformation.The Tabaiyi Tunnel,located in Yunnan Province of China passes through a multi-stage fault zone.The dynamic response characteristics of the surrounding rock in the Tabaiyi Tunnel were studied under various fault dip angles and the most unfavorable angle was identified.Physical model tests were conducted using two types of anchor cables with specific parameters.Additionally,a relationship between the engineering rock mass and energy absorption by the anchor cables was established,demonstrating the advantages of negative Poisson's ratio(NPR)anchor cables.Experimental results indicate that stress concentration tends to occur at the junctions between faults and the surrounding rock mass.Tunnels supported by NPR anchor cables effectively mitigate amplification effects,achieving energy absorption increases of up to 87%compared to positive Poisson's ratio(PR)anchor cables.Furthermore,the highest acceleration amplification was observed at a fault dip angle of 45°,with peak acceleration reaching twice that of the original input wave,indicating that this angle should be avoided in tunnel design.These findings provide valuable insights for the safe management of tunnels traversing fault zones.
基金supports from the National Natural Science Foundation of China (Grant Nos.52004143 and 52374095)the open fund for the Laboratory of Mining Response and Disaster Prevention and Control in Deep Coal Mines (Grant No.SKLMRDPC21KF06).
文摘A series of true triaxial unloading tests are conducted on sandstone specimens with a single structural plane to investigate their mechanical behaviors and failure characteristics under different in situ stress states.The experimental results indicate that the dip angle of structural plane(θ)and the intermediate principal stress(σ2)have an important influence on the peak strength,cracking mode,and rockburst severity.The peak strength exhibits a first increase and then decrease as a function ofσ2 for a constantθ.However,whenσ2 is constant,the maximum peak strength is obtained atθof 90°,and the minimum peak strength is obtained atθof 30°or 45°.For the case of an inclined structural plane,the crack type at the tips of structural plane transforms from a mix of wing and anti-wing cracks to wing cracks with an increase inσ2,while the crack type around the tips of structural plane is always anti-wing cracks for the vertical structural plane,accompanied by a series of tensile cracks besides.The specimens with structural plane do not undergo slabbing failure regardless ofθ,and always exhibit composite tensile-shear failure whatever theσ2 value is.With an increase inσ2 andθ,the intensity of the rockburst is consistent with the tendency of the peak strength.By analyzing the relationship between the cohesion(c),internal friction angle(φ),andθin sandstone specimens,we incorporateθinto the true triaxial unloading strength criterion,and propose a modified linear Mogi-Coulomb criterion.Moreover,the crack propagation mechanism at the tips of structural plane,and closure degree of the structural plane under true triaxial unloading conditions are also discussed and summarized.This study provides theoretical guidance for stability assessment of surrounding rocks containing geological structures in deep complex stress environments.
基金supported by the National Natural Science Foundation of China(Grant No.52374078)the Fundamental Research Funds for the Central Universities(Grant No.2023CDJKYJH021)the Sichuan-Chongqing Science and Technology Innovation Cooperation Program Project(Grant No.2024TIAD-CYKJCXX0011).
文摘Cyclic changes in the internal pressure of compressed air energy storage reservoirs in abandoned coal mines result in complex alternating loads on the rocks surrounding the energy storage reservoirs.These complex alternating loads can be regarded as multi-stage constant-amplitude cyclic loads following simplification.In this paper,the mechanical responses and acoustic emission(AE)characteristics of red sandstone with five bedding dip angles(0°,30°,45°,60°,and 90°)under such loads are investigated,and the damage evolution processes of the five specimens are revealed from both quantitative and microscopic perspectives.The results show that the fatigue deformation characteristics of the specimens are affected by the bedding dip angle.Under cyclic loads,the axially irreversible plastic deformations of the rocks increase,their elastic stiffness increases,their crack volumetric strain increases and then decreases,and their AE cumulative count/energy curves exhibit a ladder shape.A damage evolution model based on the crack volumetric strain is proposed,and the damage evolution process is divided into two stages:a rapid increase stage and a tendency toward stabilization stage.Through cluster analysis,the AE events are used to classify the damage into three categories:small-sized localized damage,large-sized tensile damage,and large-sized shear damage.Finally,the MohreCoulomb criterion is applied to analyze the relationship between the failure modes of the red sandstone specimens and the dip angle of the bedding.The results of this study will help to predict the stability and safety of compressed air energy storage reservoirs in abandoned coal mines.
文摘The paper goal is to analyze the variability of foF2 at African equatorial stations and the effect of dip angle on this variability. The gap between the dip angle of Dakar and Ouagadougou is superior to that between Djibouti and Ouagadougou. The trend of the dip angle at Ouagadougou and Dakar decreases while that of Djibouti increases. The relative position of the station with respect to the equator and the trend sign explains the difference observed in foF2 variability at Dakar station and at the two other stations. At Djibouti and Ouagadougou, foF2 exhibits noon bite out profile during all solar cycle phases while at Dakar observed profile is dome or plateau during the maximum and the predominance afternoon peak for the other solar cycle phases.
基金Funded by the Guizhou Province Outstanding Young Scientifc and Technological Talents Training Plan(No.Qian Kehe Platform Talents-YQK[2023]012)National Natural Science Foundation of China(Nos.52104080,52264004)+4 种基金Guizhou Science and Technology Fund(No.[2021]401)Guizhou Science and Technology Fund(Qiankehe Support[2023]136)Guizhou Science and Technology Fund(Qiankehe Support[2022]227)Guizhou Science and Technology Fund(Qiankehe Strategic Search for Minerals[2022]ZD005)Natural Science Special(Special Post)Scientifc Research Fund Project of Guizhou University(No.[2021]51)。
文摘To study the damage and failure of shale with different fracture inclination angles under uniaxial compression loading,in this work,RFPA2D-Thermal,a two-dimensional real failure process analysis software,was used for numerical simulation.Numerical simulation results show that quartz in shale mainly affects the tensile and compressive strength of shale by increasing rock brittleness.The coupling of temperature and pressure will cause lateral and volume destruction of shale,which enables the shale body to be more easily broken.Fracture inclination is the key factor affecting shale damage patterns.The failure mode of shale with low-and high-angle fractures is mainly shear failure,and the compressive strength does not vary with crack inclination.The damage mode of obliquely intersecting fractured shale is slip damage along the fracture face,the compressive strength decreases and then increases with the fracture inclination,and a minimum value exists.The acoustic emission simulation results of the damage process effectively reflect the accumulated internal damage and macroscopic crack appearance until fracture instability when the prefabricated fractured shale is subjected to uniaxial compressive loading.The crack inclinations of 0°and 120℃ corresponds to the most complex"N"shape damage mode.The crack inclinations of 30°and 60°,and the damage mode is an inverted"λ"shape.
基金supported by the National Natural Science Foundation of China (Nos.41472202)
文摘The 2015 Gorkha Earthquake in Nepal and the 2008 Wenchuan Earthquake in China occurred at the south and southeast margins of the Tibetan Plateau, respectively. Both earthquakes had similar magnitudes of Mw 7.8 and 7.9, caused catastrophic loss of life and damage to property, and generated tens of thousands of landslides. Comparisons of pre-and post-quake satellite images supported by field investigations show that the Gorkha Earthquake triggered at least 2 064 large landslides （defined as covering an area ≥10 000 m2） over a -35 600 km2 region with a volume of （444-584）×10^6 （average 509×10^6） m3 and total area of 44.78×10^6 m2. In contrast, the Wenchuan Earthquake triggered 25 580 large landslides over a region of -44 000 km2 with a volume of （7 128-9 479）×10^6 （average 8 219×10^6） m3 and a total area of about 670.65×10^6 m2. Several controlling factors including topographic relief, slope steepness, and regional peak ground acceleration （PGA） were investigated to try to explain the great differences between the number, volume and area of the coseismic landslides associated with the two similar earthquakes. We found that the differences primarily arose from an unexpected factor, the dip angle of the seismogenic fault. This discovery should aid understanding the failure mechanisms of quake-triggered landslides, and suggests that more factors should be taken into consideration in estimating coseismic landslide volumes from earthquake magnitudes. KEY WORDS： Gorkha Earthquake, Wenchuan Earthquake, landslide, dip angle, seismogenic fault.
基金supported by the National Natural Scientific Foundation of China (41274059 and 40974021)Beijing Natural Scientific Foundation (8122039 and 8092028) to J. LeiSpecial Project for Basic Scientific Research (ZDJ2013-12) to G. Zhang
文摘Using the double-difference relocation algo- rithm, we relocated the 20 April 2013 Lushan, Sichuan, earthquake （Ms 7.0）, and its 4,567 aftershocks recorded during the period between 20 April and May 3, 2013. Our results showed that most aftershocks are relocated between 10 and 20 km depths, but some large aftershocks were relocated around 30 krn depth and small events extended upward near the surface. Vertical cross sections illustrate a shovel-shaped fault plane with a variable dip angle from the southwest to northeast along the fault. Furthermore, the dip angle of the fault plane is smaller around the mainshock than that in the surrounding areas along the fault. These results suggest that it may be easy to generate the strong earthquake in the place having a small dip angle of the fault, which is somewhat similar to the genesis of the 2008 Wenchuan earthquake. The Lushan mainshock is underlain by the seismically anomalous layers with low-Vp, low-Vs, and high-Poisson＇s ratio anomalies, possibly suggesting that the fluid-filled fractured rock matrices might signifi- cantly reduce the effective normal stress on the fault plane to bring the brittle failure. The seismic gap between Lushan and Wenchuan aftershocks is suspected to be vulnerable to future seismic risks at greater depths, if any.
基金This work was supported by the Fundamental Research Funds for the Central Universities,the Postgraduate Research&Practice Innovation Program of Jiangsu Province(Grant No.KYCX21_0487)the National Natural Science Foundation of China(Grant Nos.41831278,and 51579081).
文摘The irregularity of jointed network poses a challenge to the determination of field mechanical param-eters of columnar jointed rock mass(CJRM),and a reasonable prediction of deformation and strength characteristics of CJRM is important for engineering construction.The Voronoi diagram and three-dimensional printing technology were used to make an irregular columnar jointed mold,and the irregular CJRM(ICJRM)specimens with different dip directions and dip angles were prepared.Uniaxial compression tests were performed,and the anisotropic strength and deformation characteristics of ICJRM were described.The failure modes and mechanisms were revealed in accordance with the final appearances of the ICJRM specimens.Based on the model test results,the empirical correlations for determining the field deformation and strength parameters of CJRM were derived using the dip angle and modified joint factor.The proposed empirical equations were used in the Baihetan Project,and the calculated mechanical parameters were compared with the field test results and those obtained from the tunneling quality index method.Results showed that the deformation parameters determined by the two proposed methods are all consistent with the field test results,and these two methods can also estimate the strength parameters effectively.
基金Supported by the PetroChina’s Fundamental Research Project(2019A-3609)。
文摘To quantitatively determine the effect of different factors such as fracture width,dip angle,extension and filling material on Stoneley wave amplitude decreasing,the shock tube experiment method was changed from fixing the sample and vertically moving the sensor in the borehole to fixing the sensors along the shock tube wall and vertically moving the sample without drilling the borehole in it.The measurement accuracy and the signal-to-noise ratio of the first Stoneley wave were improved by the time corrections and amplitude corrections of Stoneley wave signals.At the same time,21 sets of core models with different fracture parameters were processed for this measurement method by using full-diameter carbonate core,and relative amplitudes were defined to characterize Stoneley wave amplitude decreasing.The experimental results show that the relative amplitude of Stoneley wave exponentially decreases with increasing fracture width.The relative amplitude of Stoneley wave linearly decreases with increasing fracture dip angle.The relative amplitude of Stoneley wave exponentially decreases with increasing fracture extension.The relative amplitude of Stoneley wave decreases with increasing the permeability of filling material in the fracture.Under the above four conditions,the fracture width has the greatest effect on the decreasing of Stoneley wave amplitude,followed by the fracture extension and the permeability of filling material,and finally the fracture dip angle.
基金the financial support from the National Natural Science Foundation of China(42074134,41974146,41574118)the Scientific and Technological Research Projects of Sinopec(JP22503,P21080)+1 种基金the Major Scientific and Technological Projects of China National Petroleum Corporation(ZD2019-184-001)Shandong Provincial Natural Science Foundation(ZR2020MD050)
文摘The maximum distance at which an electromagnetic(EM)logging while drilling(LWD)tool detects an approaching boundary is defined as the depth of detection(DOD).Ultra-deep detection capability of the transient multicomponent EM logging measurement is investigated here.First,we adopt sine and cosine transform to calculate the transient multicomponent responses.Compared to the cosine transform,sine transform is more accurate in solving late-time responses.Then,a time-domain geosignal is introduced to sense the boundary.Results show that DOD of this transient EM measurement can be up to tens of meters,including directionally sensitivity.Additionally,by studying the decay characteristics of different components with time,cross component is confirmed to decay much faster than the coaxial/coplanar components in the formation coordinate system.A pseudo-inversion is thereby proposed to determine the dip angle of anisotropic stratified formation.Theoretical simulation results indicate that this algebraic method can determine the true dip at some particular moments.It is still stable and valid even when considering random measurement errors.Moreover,we establish the linear relationship between the time at which the half-point of geosignal curve appears and the distance to boundary(DTB),which would assist in the quick determination of DTB.
基金National Natural Science Foundation of China(51678540,51778197)Heilongjiang Province Key Research and Development Program Guidance Project of China(GZ20220028)+2 种基金Heilongjiang Bayi Agricultural University Support Program for San Heng San Zong(ZRCPY202225)Heilongjiang Bayi Agricultural University Project of Scientific Research Initiation Plan for Learning and Introducing Talents of China(XYB2014-06)Daqing Science and Technology Plan Project of China(zd-2021-86).
文摘The attenuation relationship of ground motion based on seismology has always been a front subject of engineering earthquake.Among them,the regional finite-fault source model is very important.In view of this point,the general characteristics of regional seism-tectonics,including the dip and depth of the fault plane,are emphasized.According to the statistics of regional seism-tectonics and focal mechanisms in Sichuan,China,and the sensitivity of estimated peak ground acceleration(PGA)attenuation is analyzed,and the dip angle is taken as an average of 70°.Based the statistics of the upper crustal structure and the focal depth of regional earthquakes,the bottom boundary of the sedimentary cover can be used as the upper limit for estimating the depth of upper-edge.The analysis shows that this value is sensitive to PGA.Based on the analysis of geometric relations,the corresponding calculation formula is used,and a set of concepts and steps for building the regional finite-fault source model is proposed.The estimation of source parameters takes into account the uncertainty,the geometric relationship among parameters and the total energy conservation.Meanwhile,a set of reasonable models is developed,which lay a foundation for the further study of regional ground motion attenuation based on seismology.
