The characterisation of the pore-fracture structure(PFS)and its evolution in coal during mining are essential for preventing gas outbursts and improving gas extraction efficiency.In this study,the evolution of the PFS...The characterisation of the pore-fracture structure(PFS)and its evolution in coal during mining are essential for preventing gas outbursts and improving gas extraction efficiency.In this study,the evolution of the PFS in coal samples under the condition of mining stress was directly captured in situ by combination of the mechanical testing system with high-precision visualisation nuclear magnetic resonance equipment.A fractional derivative model was established to describe the relationship between stress and porosity based on experimental results of the PFS under different stress states.The results showed that with an increase in the deviatoric stress,the adsorption pore content increases rapidly initially and then increases slowly or remains unchanged;the seepage pore and fracture(SPF)content decreases initially and then increases.The SPF compressibility coefficient decreases with an increase in the deviatoric stress.The fractional derivative model can accurately describe the stress sensitivity of the SPFs at the pre-peak stage,thus providing a new approach for accurately characterising the seepage characteristics of coal reservoirs.展开更多
Currently, scant attention has been paid to the theoretical analysis on dynamic response mechanism of the "Dualistic" structure rock slope.The analysis presented here provides insight into the dynamic respon...Currently, scant attention has been paid to the theoretical analysis on dynamic response mechanism of the "Dualistic" structure rock slope.The analysis presented here provides insight into the dynamic response of the "Dualistic" structure rock slope. By investigating the principle of energy distribution, it is shown that the effect of a joint plays a significant role in slope stability analysis. A dynamic reflection and transmission model(RTM) for the"Dualistic" structure rock slope and explicit dynamic equations are established to analyze the dynamic response of a slope, based on the theory of elastic mechanics and the principle of seismic wave propagation. The theoretical simulation solutions show that the dynamic response of the "Dualistic"structure rock slope(soft-hard) model is greater than that of the "Dualistic" structure rock slope(hard-soft)model, especially in the slope crest. The magnifying effect of rigid foundation on the dynamic response is more obvious than that of soft foundation. With the amplitude increasing, the cracks could be found in the right slope(soft-hard) crest. The crest failure is firstly observed in the right slope(soft-hard) during the experimental process. The reliability of theoretical model is also investigated by experiment analysis. The conclusions derived in this paper could also be used in future evaluations of Multi-layer rock slopes.展开更多
To study the seepage and deformation characteristics of coal at high temperatures,coal samples from six different regions were selected and subjected to computed tomography(CT)scanning studies.In conjunction with ANSY...To study the seepage and deformation characteristics of coal at high temperatures,coal samples from six different regions were selected and subjected to computed tomography(CT)scanning studies.In conjunction with ANSYS software,3 D reconstruction of CT images was used for the establishment of fluidsolid conjugate heat transfer model and coal thermal deformation model based on the microstructures of coal.In addition,the structure of coal was studied in 2 D and 3 D perspectives,followed by the analysis of seepage and deformation characteristics of coal at high temperatures.The results of this study indicated that porosity positively correlated with the fractal dimension,and the connectivity and seepage performances were roughly identical from 2 D and 3 D perspectives.As the porosity increased,the fractal dimension of coal samples became larger and the pore-fracture structures became more complex.As a result,the permeability of coal samples decreased.In the meantime,fluid was fully heated,generating high-temperature water at outlet.However,when the porosity was low,the outlet temperature was very high.The average deformation of coal skeleton with different pore-fracture structures at high temperatures showed a trend of initial increase and subsequent decrease with the increase of porosity and fractal dimension.The maximum deformation of coal skeleton positively correlated with connectivity but negatively correlated with the fractal dimension.展开更多
Understanding the variations in microscopic pore-fracture structures(MPFS) during coal creep under pore pressure and stress coupling is crucial for coal mining and effective gas treatment. In this manuscript, a triaxi...Understanding the variations in microscopic pore-fracture structures(MPFS) during coal creep under pore pressure and stress coupling is crucial for coal mining and effective gas treatment. In this manuscript, a triaxial creep test on deep coal at various pore pressures using a test system that combines in-situ mechanical loading with real-time nuclear magnetic resonance(NMR) detection was conducted.Full-scale quantitative characterization, online real-time detection, and visualization of MPFS during coal creep influenced by pore pressure and stress coupling were performed using NMR and NMR imaging(NMRI) techniques. The results revealed that seepage pores and microfractures(SPM) undergo the most significant changes during coal creep, with creep failure gradually expanding from dense primary pore fractures. Pore pressure presence promotes MPFS development primarily by inhibiting SPM compression and encouraging adsorption pores(AP) to evolve into SPM. Coal enters the accelerated creep stage earlier at lower stress levels, resulting in more pronounced creep deformation. The connection between the micro and macro values was established, demonstrating that increased porosity at different pore pressures leads to a negative exponential decay of the viscosity coefficient. The Newton dashpot in the ideal viscoplastic body and the Burgers model was improved using NMR experimental results, and a creep model that considers pore pressure and stress coupling using variable-order fractional operators was developed. The model’s reasonableness was confirmed using creep experimental data. The damagestate adjustment factors ω and β were identified through a parameter sensitivity analysis to characterize the effect of pore pressure and stress coupling on the creep damage characteristics(size and degree of difficulty) of coal.展开更多
Land is the space carrier for the existence and flow of other development factors.Activating rural land and promoting the circulation of other development factors through land management innovation is necessary to rea...Land is the space carrier for the existence and flow of other development factors.Activating rural land and promoting the circulation of other development factors through land management innovation is necessary to realize rural vitalization.This paper identifies the connotation of factor flow in the rural vitalization context,the action mechanism of land management innovation to boost the flow of development factors,the issues and obstacles restricting factor circulation,and the realization mechanism of the flow of development factors in rural vitalization.Based on the analytic paradigm constructed in the paper,the successful practice of promoting the flow of development factors through innovative land management in a model village is examined.The results show that:1)the unreasonable systems characterized by the land use system in rural areas are the main obstacles causing circulation issues in development factors.It is essential to engage in comprehensive reform to break down these long-lasting obstacles to the smooth flow of development factors.2)The land should play a leading role in the circulation of development factors in the background of rural vitalization;the main purpose of land management innovation is to activate the land factor,thereby promoting the circulation of other factors.3)The activated land factor will act as a‘trigger’to promote capital and technology in rural settings and use capital and technology to attract the inflow of talents and the return of migrant workers,whereby the population factor will act as a‘catalyst’for the cultivation of rural culture,bringing about the integration of various development factors.4)The innovation of land use and management,increased funding,and new technologies have brought multiple talents to Tengtou Village.The high-frequency mutual feedback between the village’s own and the external development factors resulted in its successful integration of industrial development.展开更多
基金This work was supported by the National Natural Science Foundation of China(Nos.51827901,52121003,52142302,and 51904309)the 111 Project(No.B14006)the Yueqi Outstanding Scholar Program of CUMTB(No.2017A03).
文摘The characterisation of the pore-fracture structure(PFS)and its evolution in coal during mining are essential for preventing gas outbursts and improving gas extraction efficiency.In this study,the evolution of the PFS in coal samples under the condition of mining stress was directly captured in situ by combination of the mechanical testing system with high-precision visualisation nuclear magnetic resonance equipment.A fractional derivative model was established to describe the relationship between stress and porosity based on experimental results of the PFS under different stress states.The results showed that with an increase in the deviatoric stress,the adsorption pore content increases rapidly initially and then increases slowly or remains unchanged;the seepage pore and fracture(SPF)content decreases initially and then increases.The SPF compressibility coefficient decreases with an increase in the deviatoric stress.The fractional derivative model can accurately describe the stress sensitivity of the SPFs at the pre-peak stage,thus providing a new approach for accurately characterising the seepage characteristics of coal reservoirs.
基金financially supported by Project of the National Natural Science Foundation of China (Grant No. 41002126)Project of State Key Laboratory of Geohazard Prevention and Geoenvironment Protection (Grant No. SKLGP2009Z010)
文摘Currently, scant attention has been paid to the theoretical analysis on dynamic response mechanism of the "Dualistic" structure rock slope.The analysis presented here provides insight into the dynamic response of the "Dualistic" structure rock slope. By investigating the principle of energy distribution, it is shown that the effect of a joint plays a significant role in slope stability analysis. A dynamic reflection and transmission model(RTM) for the"Dualistic" structure rock slope and explicit dynamic equations are established to analyze the dynamic response of a slope, based on the theory of elastic mechanics and the principle of seismic wave propagation. The theoretical simulation solutions show that the dynamic response of the "Dualistic"structure rock slope(soft-hard) model is greater than that of the "Dualistic" structure rock slope(hard-soft)model, especially in the slope crest. The magnifying effect of rigid foundation on the dynamic response is more obvious than that of soft foundation. With the amplitude increasing, the cracks could be found in the right slope(soft-hard) crest. The crest failure is firstly observed in the right slope(soft-hard) during the experimental process. The reliability of theoretical model is also investigated by experiment analysis. The conclusions derived in this paper could also be used in future evaluations of Multi-layer rock slopes.
基金supported by the National Natural Science Foundation of China(Project Nos.51934004,51674158,51574158,and 51474106)the Major Program of Shandong Province Natural Science Foundation(ZR2018ZA0602)+2 种基金the Taishan Scholar Talent Team Support Plan for Advantaged&Unique Discipline Areasthe Science and technology support plan for Youth Innovation of colleges and universities in Shandong Province(2019KJH006)the special funds for Taishan scholar project(TS20190935)。
文摘To study the seepage and deformation characteristics of coal at high temperatures,coal samples from six different regions were selected and subjected to computed tomography(CT)scanning studies.In conjunction with ANSYS software,3 D reconstruction of CT images was used for the establishment of fluidsolid conjugate heat transfer model and coal thermal deformation model based on the microstructures of coal.In addition,the structure of coal was studied in 2 D and 3 D perspectives,followed by the analysis of seepage and deformation characteristics of coal at high temperatures.The results of this study indicated that porosity positively correlated with the fractal dimension,and the connectivity and seepage performances were roughly identical from 2 D and 3 D perspectives.As the porosity increased,the fractal dimension of coal samples became larger and the pore-fracture structures became more complex.As a result,the permeability of coal samples decreased.In the meantime,fluid was fully heated,generating high-temperature water at outlet.However,when the porosity was low,the outlet temperature was very high.The average deformation of coal skeleton with different pore-fracture structures at high temperatures showed a trend of initial increase and subsequent decrease with the increase of porosity and fractal dimension.The maximum deformation of coal skeleton positively correlated with connectivity but negatively correlated with the fractal dimension.
基金supported by the National Natural Science Foundation of China(Nos.52121003,51827901 and 52204110)China Postdoctoral Science Foundation(No.2022M722346)+1 种基金the 111 Project(No.B14006)the Yueqi Outstanding Scholar Program of CUMTB(No.2017A03).
文摘Understanding the variations in microscopic pore-fracture structures(MPFS) during coal creep under pore pressure and stress coupling is crucial for coal mining and effective gas treatment. In this manuscript, a triaxial creep test on deep coal at various pore pressures using a test system that combines in-situ mechanical loading with real-time nuclear magnetic resonance(NMR) detection was conducted.Full-scale quantitative characterization, online real-time detection, and visualization of MPFS during coal creep influenced by pore pressure and stress coupling were performed using NMR and NMR imaging(NMRI) techniques. The results revealed that seepage pores and microfractures(SPM) undergo the most significant changes during coal creep, with creep failure gradually expanding from dense primary pore fractures. Pore pressure presence promotes MPFS development primarily by inhibiting SPM compression and encouraging adsorption pores(AP) to evolve into SPM. Coal enters the accelerated creep stage earlier at lower stress levels, resulting in more pronounced creep deformation. The connection between the micro and macro values was established, demonstrating that increased porosity at different pore pressures leads to a negative exponential decay of the viscosity coefficient. The Newton dashpot in the ideal viscoplastic body and the Burgers model was improved using NMR experimental results, and a creep model that considers pore pressure and stress coupling using variable-order fractional operators was developed. The model’s reasonableness was confirmed using creep experimental data. The damagestate adjustment factors ω and β were identified through a parameter sensitivity analysis to characterize the effect of pore pressure and stress coupling on the creep damage characteristics(size and degree of difficulty) of coal.
基金Under the auspices of National Natural Science Foundation of China(No.42171255,42201204)。
文摘Land is the space carrier for the existence and flow of other development factors.Activating rural land and promoting the circulation of other development factors through land management innovation is necessary to realize rural vitalization.This paper identifies the connotation of factor flow in the rural vitalization context,the action mechanism of land management innovation to boost the flow of development factors,the issues and obstacles restricting factor circulation,and the realization mechanism of the flow of development factors in rural vitalization.Based on the analytic paradigm constructed in the paper,the successful practice of promoting the flow of development factors through innovative land management in a model village is examined.The results show that:1)the unreasonable systems characterized by the land use system in rural areas are the main obstacles causing circulation issues in development factors.It is essential to engage in comprehensive reform to break down these long-lasting obstacles to the smooth flow of development factors.2)The land should play a leading role in the circulation of development factors in the background of rural vitalization;the main purpose of land management innovation is to activate the land factor,thereby promoting the circulation of other factors.3)The activated land factor will act as a‘trigger’to promote capital and technology in rural settings and use capital and technology to attract the inflow of talents and the return of migrant workers,whereby the population factor will act as a‘catalyst’for the cultivation of rural culture,bringing about the integration of various development factors.4)The innovation of land use and management,increased funding,and new technologies have brought multiple talents to Tengtou Village.The high-frequency mutual feedback between the village’s own and the external development factors resulted in its successful integration of industrial development.
