This study investigates the influence of the elastic modulus(E)of the composite strata on the trough width coefficient(i).It is hypothesized that,in composite strata,the relationship between the trough width coefficie...This study investigates the influence of the elastic modulus(E)of the composite strata on the trough width coefficient(i).It is hypothesized that,in composite strata,the relationship between the trough width coefficient(i)and the stratum thickness(H)follows a piecewise linear trend.Specifically,within strata of identical elastic modulus(E),i exhibits a linear correlation with H,while variations in E affect the slope of this correlation.Building upon the non-iterative analytical method(NIAM)for evaluating tunnel excavation responses in composite strata,this study proposes two novel approaches:the crucial point method(CPM)and the standard curve method(SCM).These methods incorporate the elastic modulus into the estimation of i.The values of i obtained via NIAM and refined through CPM and SCM are validated against field data using the parameter K.The results are consistent with existing research findings,thereby confirming the reliability of the proposed methodology.Furthermore,the study investigates the relationship between tunnel depth(h0)and tunnel radius(R),and explores the interactions among the layer number of stratum(n),elastic modulus(E),and layer thickness(H).A reduction coefficient(η)is introduced to improve the model's accuracy.The proposed approach is applied to nine tunnel engineering cases,and comparisons with measured data demonstrate its accuracy and practical applicability.展开更多
The negative Poisson’s ratio(NPR)bolt is an innovative support element distinguished by its high strength,elongation,and a slightly negative Poisson’s ratio.Unlike conventional prestressed(PR)bolts with a positive P...The negative Poisson’s ratio(NPR)bolt is an innovative support element distinguished by its high strength,elongation,and a slightly negative Poisson’s ratio.Unlike conventional prestressed(PR)bolts with a positive Poisson’s ratio,the NPR bolt exhibits a quasi-ideal plastic response without a prominent yield platform,enabling it to sustain high prestress with a substantial safety margin,which is particularly advantageous for jointed rock masses.However,investigations into the shear resistance mechanisms of NPR bolts under varying prestress levels remain limited.This study conducted full-scale double shear tests to assess the shear strength,deformation behavior,energy absorption,and failure mechanisms of NPR bolts under different prestress conditions.To ensure a fair comparison with PR bolts,a prestress utilization coefficient(PUC)was introduced.The results reveal that at a PUC of 0.25,the NPR bolt achieved peak axial force,shear displacement,and peak shear force values that are 2.41,1.88,and 2.13 times greater than those of the PR bolt,respectively.Shear performance was optimized at a prestress level of 100 kN,with energy absorption reaching 47.1 kJ,which is 2.8 times that of the PR bolt.Furthermore,the necking ratio was significantly reduced,indicating more distributed plastic deformation and delayed failure.Field applications verified the superior performance,resulting in a 27.4%reduction in roof settlement and enhanced structural integrity.These findings confirm that NPR bolts possess excellent shear resistance,energy absorption,and deformation adaptability,and optimizing prestress significantly enhances their support performance,providing a strong basis for geotechnical engineering applications.展开更多
An analytical model based on complex variable theory is proposed to investigate ground responses due to shallow tunneling in multi-layered ground with an arbitrary ground surface load.The ground layers are assumed to ...An analytical model based on complex variable theory is proposed to investigate ground responses due to shallow tunneling in multi-layered ground with an arbitrary ground surface load.The ground layers are assumed to be linear-elastic with full-stick contact between them.To solve the proposed multi-boundary problem,a series of analytic functions is introduced to accurately express the stresses and displacements contributed by different boundaries.Based on the principle of linear-elastic superposition,the multi-boundary problem is converted into a superposition of multiple single-boundary problems.The conformal mappings of different boundaries are independent of each other,which allows the stress and displacement fields to be obtained by the sum of components from each boundary.The analytical results are validated based on numerical and in situ monitoring results.The present model is superior to the classical model for analyzing ground responses of shallow tunneling in multi-layered ground;thus,it can be used with assurance to estimate the ground movement and surface building safety of shallow tunnel constructions beneath surface buildings.Moreover,the solution for the ground stress distribution can be used to estimate the safety of a single-layer composite ground.展开更多
基金support from the National Natural Science Foundation of China(Grant No.52278387).
文摘This study investigates the influence of the elastic modulus(E)of the composite strata on the trough width coefficient(i).It is hypothesized that,in composite strata,the relationship between the trough width coefficient(i)and the stratum thickness(H)follows a piecewise linear trend.Specifically,within strata of identical elastic modulus(E),i exhibits a linear correlation with H,while variations in E affect the slope of this correlation.Building upon the non-iterative analytical method(NIAM)for evaluating tunnel excavation responses in composite strata,this study proposes two novel approaches:the crucial point method(CPM)and the standard curve method(SCM).These methods incorporate the elastic modulus into the estimation of i.The values of i obtained via NIAM and refined through CPM and SCM are validated against field data using the parameter K.The results are consistent with existing research findings,thereby confirming the reliability of the proposed methodology.Furthermore,the study investigates the relationship between tunnel depth(h0)and tunnel radius(R),and explores the interactions among the layer number of stratum(n),elastic modulus(E),and layer thickness(H).A reduction coefficient(η)is introduced to improve the model's accuracy.The proposed approach is applied to nine tunnel engineering cases,and comparisons with measured data demonstrate its accuracy and practical applicability.
基金supported by the State Key Laboratory of Intelligent Construction and Healthy Operation and Maintenance of Deep Underground Engineering(Grant No.SDGZ2505)the Postdoctoral Fellowship Program of the China Postdoctoral Science Foundation(Grant No.GZB20250742)the General Program of the China Postdoctoral Science Foundation(Grant No.2025M773213).
文摘The negative Poisson’s ratio(NPR)bolt is an innovative support element distinguished by its high strength,elongation,and a slightly negative Poisson’s ratio.Unlike conventional prestressed(PR)bolts with a positive Poisson’s ratio,the NPR bolt exhibits a quasi-ideal plastic response without a prominent yield platform,enabling it to sustain high prestress with a substantial safety margin,which is particularly advantageous for jointed rock masses.However,investigations into the shear resistance mechanisms of NPR bolts under varying prestress levels remain limited.This study conducted full-scale double shear tests to assess the shear strength,deformation behavior,energy absorption,and failure mechanisms of NPR bolts under different prestress conditions.To ensure a fair comparison with PR bolts,a prestress utilization coefficient(PUC)was introduced.The results reveal that at a PUC of 0.25,the NPR bolt achieved peak axial force,shear displacement,and peak shear force values that are 2.41,1.88,and 2.13 times greater than those of the PR bolt,respectively.Shear performance was optimized at a prestress level of 100 kN,with energy absorption reaching 47.1 kJ,which is 2.8 times that of the PR bolt.Furthermore,the necking ratio was significantly reduced,indicating more distributed plastic deformation and delayed failure.Field applications verified the superior performance,resulting in a 27.4%reduction in roof settlement and enhanced structural integrity.These findings confirm that NPR bolts possess excellent shear resistance,energy absorption,and deformation adaptability,and optimizing prestress significantly enhances their support performance,providing a strong basis for geotechnical engineering applications.
基金This study was supported by the Fundamental Research Funds for Central Universities(No.2022JBZY041)the National Natural Science Foundation of China(Grant Nos.52208382,51738002,and 52278387).
文摘An analytical model based on complex variable theory is proposed to investigate ground responses due to shallow tunneling in multi-layered ground with an arbitrary ground surface load.The ground layers are assumed to be linear-elastic with full-stick contact between them.To solve the proposed multi-boundary problem,a series of analytic functions is introduced to accurately express the stresses and displacements contributed by different boundaries.Based on the principle of linear-elastic superposition,the multi-boundary problem is converted into a superposition of multiple single-boundary problems.The conformal mappings of different boundaries are independent of each other,which allows the stress and displacement fields to be obtained by the sum of components from each boundary.The analytical results are validated based on numerical and in situ monitoring results.The present model is superior to the classical model for analyzing ground responses of shallow tunneling in multi-layered ground;thus,it can be used with assurance to estimate the ground movement and surface building safety of shallow tunnel constructions beneath surface buildings.Moreover,the solution for the ground stress distribution can be used to estimate the safety of a single-layer composite ground.
