Volcanic terrains exhibit a complex structure of pyroclastic deposits interspersed with sedimentary processes,resulting in irregular lithological sequences that lack lateral continuity and distinct stratigraphic patte...Volcanic terrains exhibit a complex structure of pyroclastic deposits interspersed with sedimentary processes,resulting in irregular lithological sequences that lack lateral continuity and distinct stratigraphic patterns.This complexity poses significant challenges for slope stability analysis,requiring the development of specialized techniques to address these issues.This research presents a numerical methodology that incorporates spatial variability,nonlinear material characterization,and probabilistic analysis using a Monte Carlo framework to address this issue.The heterogeneous structure is represented by randomly assigning different lithotypes across the slope,while maintaining predefined global proportions.This contrasts with the more common approach of applying probabilistic variability to mechanical parameters within a homogeneous slope model.The material behavior is defined using complex nonlinear failure criteria,such as the Hoek-Brown model and a parabolic model with collapse,both implemented through linearization techniques.The Discontinuity Layout Optimization(DLO)method,a novel numerical approach based on limit analysis,is employed to efficiently incorporate these advances and compute the factor of safety of the slope.Within this framework,the Monte Carlo procedure is used to assess slope stability by conducting a large number of simulations,each with a different lithotype distribution.Based on the results,a hybrid method is proposed that combines probabilistic modeling with deterministic design principles for the slope stability assessment.As a case study,the methodology is applied to a 20-m-high vertical slope composed of three lithotypes(altered scoria,welded scoria,and basalt)randomly distributed in proportions of 15%,60%,and 25%,respectively.The results show convergence of mean values after approximately 400 simulations and highlight the significant influence of spatial heterogeneity,with variations of the factor of safety between 5 and 12 in 85%of cases.They also reveal non-circular and mid-slope failure wedges not captured by traditional stability methods.Finally,an equivalent normal probability distribution is proposed as a reliable approximation of the factor of safety for use in risk analysis and engineering decision-making.展开更多
Enhanced geothermal development system is an effective means to develop hot dry rock geothermal resources,and its reasonable structural design is crucial to the efficient exploitation of hot dry rocks.In this paper,a ...Enhanced geothermal development system is an effective means to develop hot dry rock geothermal resources,and its reasonable structural design is crucial to the efficient exploitation of hot dry rocks.In this paper,a multi-lateral well enhanced geothermal development system,which is composed of one low-permeability thermal reservoir,three multi-lateral injection wells,three multi-lateral production wells and three artificial fractures,was designed based on the traditional dual-well development model.Then,a 3D hydrothermal coupling numerical evaluation model was established by using the local heat balance method,and its accuracy and reliability were verified according to Lauwerier analytical theory of fractured flow and heat transfer.Finally,the influence of reservoir parameters,well layout parameters,and injection-production parameters on the heat production performance of this enhanced geothermal development system were explored based on the water-rock coupling mechanism inside the reservoir in the process of thermal production.And the following research results were obtained.First,the“rock invasion effect”of the cold front in the fractures of the multi-lateral well development system is stronger than that in the matrix.Increasing the reservoir permeability can improve the internal heat transfer effect,but also enhances the“invasion performance”of cold front.Second,the annual thermal energy extraction of the system gradually decreases over time and it also decreases with the increase of the injection temperature.It increases with the increase of the reservoir permeability in the early stage of the operation,but decreases greatly after the completion of the thermal breakthrough.Third,the system's thermal energy extraction rate and production mass flow rate are less influenced by reservoir porosity and injection temperature,but they decrease with the increase of the vertical spacing of injection-production wells.Fourth,the production temperature decreases greatly with the increase of the reservoir permeability,increases with the increase of the reservoir porosity,and decreases with the decrease of the vertical spacing of injection-production wells.Fifth,the heat production performance of the system in the early stage can be improved by increasing the length of the production well,and the heat production capacity of the system can be enhanced to a certain degree by increasing the injection-production pressure difference,but excessive pressure difference will impact the service life of the reservoir seriously.展开更多
基金the project PID2022-139202OB-I00Neural Networks and Optimization Techniques for the Design and Safe Maintenance of Transportation Infrastructures:Volcanic Rock Geotechnics and Slope Stability(IA-Pyroslope),funded by the Spanish State Research Agency of the Ministry of Science,Innovation and Universities of Spain and the European Regional Development Fund,MCIN/AEI/10.13039/501100011033/FEDER,EU。
文摘Volcanic terrains exhibit a complex structure of pyroclastic deposits interspersed with sedimentary processes,resulting in irregular lithological sequences that lack lateral continuity and distinct stratigraphic patterns.This complexity poses significant challenges for slope stability analysis,requiring the development of specialized techniques to address these issues.This research presents a numerical methodology that incorporates spatial variability,nonlinear material characterization,and probabilistic analysis using a Monte Carlo framework to address this issue.The heterogeneous structure is represented by randomly assigning different lithotypes across the slope,while maintaining predefined global proportions.This contrasts with the more common approach of applying probabilistic variability to mechanical parameters within a homogeneous slope model.The material behavior is defined using complex nonlinear failure criteria,such as the Hoek-Brown model and a parabolic model with collapse,both implemented through linearization techniques.The Discontinuity Layout Optimization(DLO)method,a novel numerical approach based on limit analysis,is employed to efficiently incorporate these advances and compute the factor of safety of the slope.Within this framework,the Monte Carlo procedure is used to assess slope stability by conducting a large number of simulations,each with a different lithotype distribution.Based on the results,a hybrid method is proposed that combines probabilistic modeling with deterministic design principles for the slope stability assessment.As a case study,the methodology is applied to a 20-m-high vertical slope composed of three lithotypes(altered scoria,welded scoria,and basalt)randomly distributed in proportions of 15%,60%,and 25%,respectively.The results show convergence of mean values after approximately 400 simulations and highlight the significant influence of spatial heterogeneity,with variations of the factor of safety between 5 and 12 in 85%of cases.They also reveal non-circular and mid-slope failure wedges not captured by traditional stability methods.Finally,an equivalent normal probability distribution is proposed as a reliable approximation of the factor of safety for use in risk analysis and engineering decision-making.
基金Project supported by the Science and Technology Planning Project of Sichuan Province“Design of Hot Dry Rock Geothermal Resources Development Scheme and Research on Thermo-Hydro-Mechanical Coupling Mechanism”(No.:2020JDRC0088)the Youth Team Project for Scientific and Technological Innovation on Process Equipment Mechanics and Safety Evaluation of Southwest Petroleum University(No.:2018CXTD12).
文摘Enhanced geothermal development system is an effective means to develop hot dry rock geothermal resources,and its reasonable structural design is crucial to the efficient exploitation of hot dry rocks.In this paper,a multi-lateral well enhanced geothermal development system,which is composed of one low-permeability thermal reservoir,three multi-lateral injection wells,three multi-lateral production wells and three artificial fractures,was designed based on the traditional dual-well development model.Then,a 3D hydrothermal coupling numerical evaluation model was established by using the local heat balance method,and its accuracy and reliability were verified according to Lauwerier analytical theory of fractured flow and heat transfer.Finally,the influence of reservoir parameters,well layout parameters,and injection-production parameters on the heat production performance of this enhanced geothermal development system were explored based on the water-rock coupling mechanism inside the reservoir in the process of thermal production.And the following research results were obtained.First,the“rock invasion effect”of the cold front in the fractures of the multi-lateral well development system is stronger than that in the matrix.Increasing the reservoir permeability can improve the internal heat transfer effect,but also enhances the“invasion performance”of cold front.Second,the annual thermal energy extraction of the system gradually decreases over time and it also decreases with the increase of the injection temperature.It increases with the increase of the reservoir permeability in the early stage of the operation,but decreases greatly after the completion of the thermal breakthrough.Third,the system's thermal energy extraction rate and production mass flow rate are less influenced by reservoir porosity and injection temperature,but they decrease with the increase of the vertical spacing of injection-production wells.Fourth,the production temperature decreases greatly with the increase of the reservoir permeability,increases with the increase of the reservoir porosity,and decreases with the decrease of the vertical spacing of injection-production wells.Fifth,the heat production performance of the system in the early stage can be improved by increasing the length of the production well,and the heat production capacity of the system can be enhanced to a certain degree by increasing the injection-production pressure difference,but excessive pressure difference will impact the service life of the reservoir seriously.
