Deep excavations in silt strata can lead to large deformation problems,posing risks to both the excavation and adjacent structures.This study combines field monitoring with numerical simulation to investigate the unde...Deep excavations in silt strata can lead to large deformation problems,posing risks to both the excavation and adjacent structures.This study combines field monitoring with numerical simulation to investigate the underlying mechanisms and key aspects associated with large deformation problems induced by deep excavation in silt strata in Shenzhen,China.The monitoring results reveal that,due to the weak property and creep effect of the silt strata,the maximum wall deflection in the first excavated section(Section 1)exceeds its controlled value at more than 93%of measurement points,reaching a peak value of 137.46 mm.Notably,the deformation exhibits prolonged development characteristics,with the diaphragm wall deflections contributing to 39%of the overall deformation magnitude during the construction of the base slab.Subsequently,numerical simulations are carried out to analyze and assess the primary factors influencing excavation-induced deformations,following the observation of large deformations.The simulations indicate that the low strength of the silt soil is a pivotal factor that results in significant deformations.Furthermore,the flexural stiffness of the diaphragm walls exerts a notable influence on the development of deformations.To address these concerns,an optimization study of potential treatment measures was performed during the subsequent excavation of Section 2.The combined treatment approach,which comprises the reinforcement of the silt layer within the excavation and the increase in the thickness of the diaphragm walls,has been demonstrated to offer an economically superior solution for the handling of thick silt strata.This approach has the effect of reducing the lateral wall displacement by 83.1%and the ground settlement by 70.8%,thereby ensuring the safe construction of the deep excavation.展开更多
Coal mining in groundwater-rich coal fields will trigger failure of overlying strata,resulting in the formation of water-conducting fracture zone(WCFZ)and potentially leading to water-inrush accidents.In this study,a ...Coal mining in groundwater-rich coal fields will trigger failure of overlying strata,resulting in the formation of water-conducting fracture zone(WCFZ)and potentially leading to water-inrush accidents.In this study,a reliability model with consideration of spatial variability and uncertainty of strength parameters was proposed to predict the failure behaviour of overlying strata during coal mining in groundwater-rich coalfields.Rock strength parameters,including cohesion,internal friction angle,uniaxial tensile strength,and softening coefficient,are treated as random variables to determine the rock failure uncertainty.The experimental results of these geomechanical parameters at different positions are interpolated by the Kriging interpolation method.Spatially,the interpolated values are arranged as the average value of each random variable to demonstrate their autocorrelation.Furthermore,based on Mohr–Coulomb yield criterion,a performance function is deduced to calculate the failure probabilities of overburden rocks to evaluate the spatial scale of WCFZ.As a typical case,the failure features of adjacent overlying strata of No.7121 mining face in Qidong Coal Mine is analyzed.The results show that the risks of water-inrush are high when the mining face advances to 260–380 m and 1120–1240 m,which aligns with both field monitoring results and borehole observation results.The proposed model holds significant implications for prevention of water-inrush accidents in groundwater-rich coal mines.展开更多
Maintaining the stability of the excavation face is key for ensuring the safety of underwater shield tunnel construction.However,the majority of current studies on the stability of excavation face focus on the homogen...Maintaining the stability of the excavation face is key for ensuring the safety of underwater shield tunnel construction.However,the majority of current studies on the stability of excavation face focus on the homogeneous strata,with limited research conducted on the upper loose and lower dense strata.Active instability tests are conducted in this study,in concert with the digital image correlation(DIC)technique,to investigate the effects of different water pressure ratios in upper loose and lower dense water-rich strata.The accuracy of these model tests is verified using numerical simulations.The results indicate that as water pressure ratio decreases,there is an increase in both the peak displacement of surface settlement and the seepage path range of water ahead of the excavation face expands.In contrast,decreasing water pressure ratio will break the limit equilibrium state of the strata faster,cause the earth pressure on the cutterhead to change more rapidly,and increase the instability range of the strata.展开更多
Spatial structure of overlying strata existed and evolved dynamically with the exploitation scope （boundary conditions） changes in coal mines and to induce rockburst. Based on the“key strata”theory, the integrated...Spatial structure of overlying strata existed and evolved dynamically with the exploitation scope （boundary conditions） changes in coal mines and to induce rockburst. Based on the“key strata”theory, the integrated spatial structure of overlying strata was put forward, which was composed of “O-X” structure in the plane section and “F” structure in the vertical section. The formation and ongoing instability of the“O-X”and“F”structures were called as dynamic evolution cycle of the overlying strata. Three basic categories of “O-X”, “F” and “T” structures were defined, and the strata behaviors of each spatial structure were analyzed. According to energy theory, mechanism of rockburst induced by spatial structure instability was discussed. The research expanded the scope of traditional ground pressure theory and provided a guide for the prevention of rockburst and mining tremors induced by structure instability of overlying展开更多
The strata deformation in mining area was monitored in Dabaoshan copper-iron mine,and an analytical method of strata energy release was put forward.On the basis of chaotic theory,by reconstructing the phase space for ...The strata deformation in mining area was monitored in Dabaoshan copper-iron mine,and an analytical method of strata energy release was put forward.On the basis of chaotic theory,by reconstructing the phase space for time series data of strata energy release,the saturated embedding dimension and the correlation dimension of the dynamic system were obtained to be 4 and 1.212 8,respectively,and the evolution laws of distances between phase points of strata energy release in the phase space were revealed.With grey theory,a prediction model of strata energy release was set up,the maximum error of which was less than 6.7%.The results show that there are chaotic characters in strata energy release during mining;after reconstructing phase space,the subtle changing characteristics of energy release can be magnified,and the internal rules can be fully demonstrated.According to the laws,a warning system for strata stability in mining area was established to provide a technical safeguard for safe mining.展开更多
基金supported by the National Natural Science Foundation of China (Grant Nos.52008039 and 52308425)the Natural Science Foundation of Hunan Province (Grant No.2021JJ40592).
文摘Deep excavations in silt strata can lead to large deformation problems,posing risks to both the excavation and adjacent structures.This study combines field monitoring with numerical simulation to investigate the underlying mechanisms and key aspects associated with large deformation problems induced by deep excavation in silt strata in Shenzhen,China.The monitoring results reveal that,due to the weak property and creep effect of the silt strata,the maximum wall deflection in the first excavated section(Section 1)exceeds its controlled value at more than 93%of measurement points,reaching a peak value of 137.46 mm.Notably,the deformation exhibits prolonged development characteristics,with the diaphragm wall deflections contributing to 39%of the overall deformation magnitude during the construction of the base slab.Subsequently,numerical simulations are carried out to analyze and assess the primary factors influencing excavation-induced deformations,following the observation of large deformations.The simulations indicate that the low strength of the silt soil is a pivotal factor that results in significant deformations.Furthermore,the flexural stiffness of the diaphragm walls exerts a notable influence on the development of deformations.To address these concerns,an optimization study of potential treatment measures was performed during the subsequent excavation of Section 2.The combined treatment approach,which comprises the reinforcement of the silt layer within the excavation and the increase in the thickness of the diaphragm walls,has been demonstrated to offer an economically superior solution for the handling of thick silt strata.This approach has the effect of reducing the lateral wall displacement by 83.1%and the ground settlement by 70.8%,thereby ensuring the safe construction of the deep excavation.
基金supported by the National Natural Science Foundation of China(42102208)the National Natural Science Foundation of China(41972256).
文摘Coal mining in groundwater-rich coal fields will trigger failure of overlying strata,resulting in the formation of water-conducting fracture zone(WCFZ)and potentially leading to water-inrush accidents.In this study,a reliability model with consideration of spatial variability and uncertainty of strength parameters was proposed to predict the failure behaviour of overlying strata during coal mining in groundwater-rich coalfields.Rock strength parameters,including cohesion,internal friction angle,uniaxial tensile strength,and softening coefficient,are treated as random variables to determine the rock failure uncertainty.The experimental results of these geomechanical parameters at different positions are interpolated by the Kriging interpolation method.Spatially,the interpolated values are arranged as the average value of each random variable to demonstrate their autocorrelation.Furthermore,based on Mohr–Coulomb yield criterion,a performance function is deduced to calculate the failure probabilities of overburden rocks to evaluate the spatial scale of WCFZ.As a typical case,the failure features of adjacent overlying strata of No.7121 mining face in Qidong Coal Mine is analyzed.The results show that the risks of water-inrush are high when the mining face advances to 260–380 m and 1120–1240 m,which aligns with both field monitoring results and borehole observation results.The proposed model holds significant implications for prevention of water-inrush accidents in groundwater-rich coal mines.
基金supported by the National Natural Science Foundation of China(No.51978019)the Natural Science Foundation of Beijing Municipality(No.8222004),China.
文摘Maintaining the stability of the excavation face is key for ensuring the safety of underwater shield tunnel construction.However,the majority of current studies on the stability of excavation face focus on the homogeneous strata,with limited research conducted on the upper loose and lower dense strata.Active instability tests are conducted in this study,in concert with the digital image correlation(DIC)technique,to investigate the effects of different water pressure ratios in upper loose and lower dense water-rich strata.The accuracy of these model tests is verified using numerical simulations.The results indicate that as water pressure ratio decreases,there is an increase in both the peak displacement of surface settlement and the seepage path range of water ahead of the excavation face expands.In contrast,decreasing water pressure ratio will break the limit equilibrium state of the strata faster,cause the earth pressure on the cutterhead to change more rapidly,and increase the instability range of the strata.
基金Project (2013QNB30) supported by the Fundamental Research Funds for Central Universities,ChinaProject (2010CB226805) supported by the National Basic Research Program of China+3 种基金Project (51174285) supported by the National Natural Science Foundation of ChinaProject (2012BAK09B01) supported by the Twelfth Five-Year National Key Technology R&D Program,ChinaProject (SZBF2011-6-B35) supported by the Priority Academic Program Development of Jiangsu Higher Education Institutions,ChinaProject (SKLCRSM10X05) supported by the Independent Foundation of State Key Laboratory of Coal Resources and Safe Mining,China
文摘Spatial structure of overlying strata existed and evolved dynamically with the exploitation scope （boundary conditions） changes in coal mines and to induce rockburst. Based on the“key strata”theory, the integrated spatial structure of overlying strata was put forward, which was composed of “O-X” structure in the plane section and “F” structure in the vertical section. The formation and ongoing instability of the“O-X”and“F”structures were called as dynamic evolution cycle of the overlying strata. Three basic categories of “O-X”, “F” and “T” structures were defined, and the strata behaviors of each spatial structure were analyzed. According to energy theory, mechanism of rockburst induced by spatial structure instability was discussed. The research expanded the scope of traditional ground pressure theory and provided a guide for the prevention of rockburst and mining tremors induced by structure instability of overlying
基金Project (2010CB732004) supported by the National Basic Research Program of ChinaProject (51074177) supported by the Joint Funding of National Natural Science Foundation and Shanghai Baosteel Group Corporation,China
文摘The strata deformation in mining area was monitored in Dabaoshan copper-iron mine,and an analytical method of strata energy release was put forward.On the basis of chaotic theory,by reconstructing the phase space for time series data of strata energy release,the saturated embedding dimension and the correlation dimension of the dynamic system were obtained to be 4 and 1.212 8,respectively,and the evolution laws of distances between phase points of strata energy release in the phase space were revealed.With grey theory,a prediction model of strata energy release was set up,the maximum error of which was less than 6.7%.The results show that there are chaotic characters in strata energy release during mining;after reconstructing phase space,the subtle changing characteristics of energy release can be magnified,and the internal rules can be fully demonstrated.According to the laws,a warning system for strata stability in mining area was established to provide a technical safeguard for safe mining.
