Twin curved tunnels are often encountered in shield tunnelling,where significant complexities in densely exploited underground space are observed.In this study,the ground settlement and tunnel deformation due to twin-...Twin curved tunnels are often encountered in shield tunnelling,where significant complexities in densely exploited underground space are observed.In this study,the ground settlement and tunnel deformation due to twin-curved shield tunnelling in soft ground were investigated using numerical simulation and field monitoring.Different curvature radii of twin curved tunnels and subsequent effects of tunnel construction were considered to reveal the tunnelling effect on ground surface settlement and tunnel deformation.The results show that the settlement trough yields one offset towards inside of curved shield tunnelling.The location of settlement trough and maximum settlement were affected by curvature radius but except for the shape and width of settlement trough.Adjacent parallel twin-curved shield tunnelling could increase the offset of existing settlement trough and maximum settlement.Then,an empirical prediction of surface settlement trough due to twin-curved shield tunnelling with same tunnel diameters in soft clay was proposed,which was applicable to curvature radius less than 800 m.Finally,a minimum radius of 600 m of curvature tunnel was proposed in terms of allowable convergence deformation of tunnel.The result could provide guidance on safety evaluation for twin curved shield tunnelling construction.展开更多
An improved artificial bee colony-random forest(IABC-RF)model is proposed for predicting the tunnel deformation due to the excavation of an adjacent foundation pit.A new search strategy of the artificial bee colony(AB...An improved artificial bee colony-random forest(IABC-RF)model is proposed for predicting the tunnel deformation due to the excavation of an adjacent foundation pit.A new search strategy of the artificial bee colony(ABC)algorithm is herein developed and incorporated,with the results showing that a much higher computational efficiency can be achieved with the new model,while high computational accuracy can also be maintained.The improved ABC algorithm is thereafter utilised and combined with the random forest(RF)model,where four important hyper-parameters are optimized,for a tunnel deformation prediction.Results are thoroughly compared with those of other prediction methods based on machine learning(ML),as well as the monitored data on the site.Via the comparisons,the validity and effectiveness of the proposed model are fully demonstrated,and a more promising perspective can be seen of the method for its potential wide applications in geotechnical engineering.展开更多
A parametric study was conducted to determine the influence of different bolt parameters(bolt length and diameter)on the maximum induced boundary displacements in jointed rockmass,using a numerical method based on fin...A parametric study was conducted to determine the influence of different bolt parameters(bolt length and diameter)on the maximum induced boundary displacements in jointed rockmass,using a numerical method based on finite element code.Three different types of jointed systems(Type A,Type B,and Type C)were considered and analyzed.Type A displays normal joint closure,Type B demonstrates a combination of normal and shear joint closure,and in Type C,the majority of the joint is loaded in shear condition.The ground surface settlement profiles for these three joint systems,under unsupported conditions,are presented in this work.For the same rockmass properties,the cases in Type A and Type B exhibit the maximum and minimum settlement,respectively.For each joint type,the effect of variable bolt parameters on the tunnel boundary is studied in terms of the total displacement.The simulation results confirm that an increase in the bolt length does not significantly reduce the boundary displacement,whereas an increase in the bolt diameter substantially reduces the tunnel boundary displacement.展开更多
By integrating literature reviews, site observa- tion, field monitoring, theoretical analysis, summarization, etc., a construction strategy was proposed and verified for tunneling with big deformation in this paper. T...By integrating literature reviews, site observa- tion, field monitoring, theoretical analysis, summarization, etc., a construction strategy was proposed and verified for tunneling with big deformation in this paper. The tunnel was in phyllite, shotcrete cracks and steel arch distortion were observed, and a big deformation with a maximum of 2.0 m was monitored during the initial stage of the construction. Through carefully examining the site observation and laboratory test results, a construction principle was established for the tunneling on the basic concept of maintaining the rock strength/stiffness and keeping the rock dry, by providing confinement pressure to the rock, reducing the rock exposure time, keeping water out of the tunnel, etc. To achieve the construction principle, a set of specific construction measures with 11 items was further proposed and applied to the construction. To check the effectiveness of the construction measures, field monitoring was carried out, which showed that the rock deformation was well controlled and the tunnel became stable. An allowable deformation was then determined using the Fenner formulae and the monitored data in order to guide further construction, which received a good result. From this study, it can be concluded that providing quick strong initial support and reserving core soil at the working faceare extremely important to control the rock deformation and keep the tunnel stable.展开更多
The prediction of the stress field of deep-buried tunnels is a fundamental problem for scientists and engineers. In this study, the authors put forward a systematic solution for this problem. Databases from the World ...The prediction of the stress field of deep-buried tunnels is a fundamental problem for scientists and engineers. In this study, the authors put forward a systematic solution for this problem. Databases from the World Stress Map and the Crustal Stress of China, and previous research findings can offer prediction of stress orientations in an engineering area. At the same time, the Andersonian theory can be used to analyze the possible stress orientation of a region. With limited in-situ stress measurements, the Hock-Brown Criterion can be used to estimate the strength of rock mass in an area of interest by utilizing the geotechnical investigation data, and the modified Sheorey's model can subsequently be employed to predict the areas' stress profile, without stress data, by taking the existing in-situ stress measurements as input parameters. In this paper, a case study was used to demonstrate the application of this systematic solution. The planned Kohala hydropower plant is located on the western edge of Qinghai-Tibet Plateau. Three hydro-fracturing stress measurement campaigns indicated that the stress state of the area is SH - Sh 〉 Sv or SH 〉Sv 〉 Sh. The measured orientation of Sn is NEE (N70.3°-89°E), and the regional orientation of SH from WSM is NE, which implies that the stress orientation of shallow crust may be affected by landforms. The modified Sheorey model was utilized to predict the stress profile along the water sewage tunnel for the plant. Prediction results show that the maximum and minimum horizontal principal stres- ses of the points with the greatest burial depth were up to 56.70 and 40.14 MPa, respectively, and the stresses of areas with a burial depth of greater than 500 m were higher. Based on the predicted stress data, large deformations of the rock mass surrounding water conveyance tunnels were analyzed. Results showed that the large deformations will occur when the burial depth exceeds 300 m. When the burial depth is beyond 800 m, serious squeezing deformations will occur in the surrounding rock masses, thus requiring more attention in the design and construction. Based on the application efficiency in this case study, this prediction method proposed in this paper functions accurately.展开更多
For a soft rock tunnel under high stress in jointed and swell soft rock (HJS), two construction schemes pilot-tunneling enlarging excavation and step-by-step excavation were optimized using FLAC20, and the deformati...For a soft rock tunnel under high stress in jointed and swell soft rock (HJS), two construction schemes pilot-tunneling enlarging excavation and step-by-step excavation were optimized using FLAC20, and the deformation effects of the two construction schemes were verified by field tests. Based on engineer- ing geological investigation and mechanical analysis of large deformations, the complex deformation mechanisms of stress expansion and structural deformation of the soft rock tunnel were confirmed, and support countermeasures from the complex deformation mechanism converted to a single type were proposed, and the support parameters were optimized by field tests. These technologies were proved by engineering practice, which produced significant technical and economic benefits.展开更多
For the Guanshui Road Station tunnel project of Guiyang Metro Line 2,the wind pavilion group was moved out of the main tunnel to reduce the number of openings in the main tunnel,and the wind pavilion group was excavat...For the Guanshui Road Station tunnel project of Guiyang Metro Line 2,the wind pavilion group was moved out of the main tunnel to reduce the number of openings in the main tunnel,and the wind pavilion group was excavated in a triangular configuration at the entrance of the main tunnel.Based on the finite element software ABAQUS,a three-dimensional model is established to study the influence of different triangular-distribution tunnels excavation schemes on the surface settlement and tunnel stability.The objective of this study is to reveal the change rules of surface settlement,deformation and force in the support structures and the surrounding rock and identify the best excavation scheme for this tunnel configuration.Results show that to control the surface settlement and the deformation of the support structures,the optimal excavation sequence involves excavating the upper fresh air exhaust tunnel before the lower running tunnel.To control the stress of the support structures,the optimal excavation involves excavating the lower running tunnel before the upper fresh air exhaust tunnel.In this project,the most reasonable excavation sequence of the tunnel is from top to bottom.The most reasonable thickness of tunnel penetration is 5 m.展开更多
Due to the weakness in mechanical properties of chlorite schist and the high in situ stress in Jinping II hydropower station, the rock mass surrounding the diversion tunnels located in chlorite schist was observed wit...Due to the weakness in mechanical properties of chlorite schist and the high in situ stress in Jinping II hydropower station, the rock mass surrounding the diversion tunnels located in chlorite schist was observed with extremely large deformations. This may significantly increase the risk of tunnel instability during excavation. In order to assess the stability of the diversion tunnels laboratory tests were carried out in association with the petrophysical properties, mechanical behaviors and waterlweakening properties of chlorite schist. The continuous deformation of surrounding rock mass, the destruction of the support structure and a large-scale collapse induced by the weak chlorite schist and high in situ stress were analyzed. The distributions of compressive deformation in the excavation zone with large deformations were also studied. In this regard, two reinforcement schemes for the excavation of diversion tunnel bottom section were proposed accordingly. This study could offer theoretical basis for deed tunnel construction in similar geological condition~展开更多
This study presents the construction of a river channel and a bridge adjacent to existing metro tunnels in Changzhou.The influence of simultaneous construction on these existing tunnels was investigated via 3D numeric...This study presents the construction of a river channel and a bridge adjacent to existing metro tunnels in Changzhou.The influence of simultaneous construction on these existing tunnels was investigated via 3D numerical modelling to predict tunnel deformation before construction.Then,a targeted protection scheme was developed according to the obtained numerical results.The full construction period field monitoring scheme can monitor tunnel responses during construction.Subsequently,the safety of the tunnel structures was evaluated according to the monitoring results,and the evolution of tunnel deformations was analysed.The analytical results can help to clarify the influence characteristics of different construction stages,verify the effect of the proposed protection scheme,and determine the disturbance mechanism of short-distance pile construction.According to the results,the tunnel deformation mainly occurred during pile construction and river channel excavation,and the tunnel vertical displacement and convergence were mainly affected by the construction.The anti-floating scheme of the partition excavation and casting effectively controlled the tunnel heave with an alarm value of approximately 6 mm.The penetration of the short-distance casing resulted in a tunnel deformation.The main construction influence area of the casing pile was within 6D(D is the pile diameter).展开更多
基金financially supported by the National Natural Science Foundation of China(Grant No.42307260)the Sichuan Natural Science Foundation(Grant No.2023NSFSC0882)the Open Project of the Research Center of Tunnelling and Underground Engineering of Ministry of Education(Grant No.TUC2022-03).
文摘Twin curved tunnels are often encountered in shield tunnelling,where significant complexities in densely exploited underground space are observed.In this study,the ground settlement and tunnel deformation due to twin-curved shield tunnelling in soft ground were investigated using numerical simulation and field monitoring.Different curvature radii of twin curved tunnels and subsequent effects of tunnel construction were considered to reveal the tunnelling effect on ground surface settlement and tunnel deformation.The results show that the settlement trough yields one offset towards inside of curved shield tunnelling.The location of settlement trough and maximum settlement were affected by curvature radius but except for the shape and width of settlement trough.Adjacent parallel twin-curved shield tunnelling could increase the offset of existing settlement trough and maximum settlement.Then,an empirical prediction of surface settlement trough due to twin-curved shield tunnelling with same tunnel diameters in soft clay was proposed,which was applicable to curvature radius less than 800 m.Finally,a minimum radius of 600 m of curvature tunnel was proposed in terms of allowable convergence deformation of tunnel.The result could provide guidance on safety evaluation for twin curved shield tunnelling construction.
基金sponsored by the National Natural Science Foundation of China(Grant Nos.52178386,51808193,and 51979270).
文摘An improved artificial bee colony-random forest(IABC-RF)model is proposed for predicting the tunnel deformation due to the excavation of an adjacent foundation pit.A new search strategy of the artificial bee colony(ABC)algorithm is herein developed and incorporated,with the results showing that a much higher computational efficiency can be achieved with the new model,while high computational accuracy can also be maintained.The improved ABC algorithm is thereafter utilised and combined with the random forest(RF)model,where four important hyper-parameters are optimized,for a tunnel deformation prediction.Results are thoroughly compared with those of other prediction methods based on machine learning(ML),as well as the monitored data on the site.Via the comparisons,the validity and effectiveness of the proposed model are fully demonstrated,and a more promising perspective can be seen of the method for its potential wide applications in geotechnical engineering.
文摘A parametric study was conducted to determine the influence of different bolt parameters(bolt length and diameter)on the maximum induced boundary displacements in jointed rockmass,using a numerical method based on finite element code.Three different types of jointed systems(Type A,Type B,and Type C)were considered and analyzed.Type A displays normal joint closure,Type B demonstrates a combination of normal and shear joint closure,and in Type C,the majority of the joint is loaded in shear condition.The ground surface settlement profiles for these three joint systems,under unsupported conditions,are presented in this work.For the same rockmass properties,the cases in Type A and Type B exhibit the maximum and minimum settlement,respectively.For each joint type,the effect of variable bolt parameters on the tunnel boundary is studied in terms of the total displacement.The simulation results confirm that an increase in the bolt length does not significantly reduce the boundary displacement,whereas an increase in the bolt diameter substantially reduces the tunnel boundary displacement.
文摘By integrating literature reviews, site observa- tion, field monitoring, theoretical analysis, summarization, etc., a construction strategy was proposed and verified for tunneling with big deformation in this paper. The tunnel was in phyllite, shotcrete cracks and steel arch distortion were observed, and a big deformation with a maximum of 2.0 m was monitored during the initial stage of the construction. Through carefully examining the site observation and laboratory test results, a construction principle was established for the tunneling on the basic concept of maintaining the rock strength/stiffness and keeping the rock dry, by providing confinement pressure to the rock, reducing the rock exposure time, keeping water out of the tunnel, etc. To achieve the construction principle, a set of specific construction measures with 11 items was further proposed and applied to the construction. To check the effectiveness of the construction measures, field monitoring was carried out, which showed that the rock deformation was well controlled and the tunnel became stable. An allowable deformation was then determined using the Fenner formulae and the monitored data in order to guide further construction, which received a good result. From this study, it can be concluded that providing quick strong initial support and reserving core soil at the working faceare extremely important to control the rock deformation and keep the tunnel stable.
基金provided by the National Natural Science Foundation of China – China (No. 41274100)the Fundamental Research Fund for State Level Scientific Institutes (No. ZDJ2012-20)
文摘The prediction of the stress field of deep-buried tunnels is a fundamental problem for scientists and engineers. In this study, the authors put forward a systematic solution for this problem. Databases from the World Stress Map and the Crustal Stress of China, and previous research findings can offer prediction of stress orientations in an engineering area. At the same time, the Andersonian theory can be used to analyze the possible stress orientation of a region. With limited in-situ stress measurements, the Hock-Brown Criterion can be used to estimate the strength of rock mass in an area of interest by utilizing the geotechnical investigation data, and the modified Sheorey's model can subsequently be employed to predict the areas' stress profile, without stress data, by taking the existing in-situ stress measurements as input parameters. In this paper, a case study was used to demonstrate the application of this systematic solution. The planned Kohala hydropower plant is located on the western edge of Qinghai-Tibet Plateau. Three hydro-fracturing stress measurement campaigns indicated that the stress state of the area is SH - Sh 〉 Sv or SH 〉Sv 〉 Sh. The measured orientation of Sn is NEE (N70.3°-89°E), and the regional orientation of SH from WSM is NE, which implies that the stress orientation of shallow crust may be affected by landforms. The modified Sheorey model was utilized to predict the stress profile along the water sewage tunnel for the plant. Prediction results show that the maximum and minimum horizontal principal stres- ses of the points with the greatest burial depth were up to 56.70 and 40.14 MPa, respectively, and the stresses of areas with a burial depth of greater than 500 m were higher. Based on the predicted stress data, large deformations of the rock mass surrounding water conveyance tunnels were analyzed. Results showed that the large deformations will occur when the burial depth exceeds 300 m. When the burial depth is beyond 800 m, serious squeezing deformations will occur in the surrounding rock masses, thus requiring more attention in the design and construction. Based on the application efficiency in this case study, this prediction method proposed in this paper functions accurately.
基金financially supported by the National Natural Science Foundation of China (Nos. 51474188, 51074140 and 51310105020)the Natural Science Foundation of Hebei Province (No. E2014203012)the Program for Taihang Scholars
文摘For a soft rock tunnel under high stress in jointed and swell soft rock (HJS), two construction schemes pilot-tunneling enlarging excavation and step-by-step excavation were optimized using FLAC20, and the deformation effects of the two construction schemes were verified by field tests. Based on engineer- ing geological investigation and mechanical analysis of large deformations, the complex deformation mechanisms of stress expansion and structural deformation of the soft rock tunnel were confirmed, and support countermeasures from the complex deformation mechanism converted to a single type were proposed, and the support parameters were optimized by field tests. These technologies were proved by engineering practice, which produced significant technical and economic benefits.
基金Projects(B200204032,2019B07914)supported by the Fundamental Research Funds for the Central Universities,ChinaProjects(51878667,51678571,51808193)supported by the National Natural Science Foundation of China。
文摘For the Guanshui Road Station tunnel project of Guiyang Metro Line 2,the wind pavilion group was moved out of the main tunnel to reduce the number of openings in the main tunnel,and the wind pavilion group was excavated in a triangular configuration at the entrance of the main tunnel.Based on the finite element software ABAQUS,a three-dimensional model is established to study the influence of different triangular-distribution tunnels excavation schemes on the surface settlement and tunnel stability.The objective of this study is to reveal the change rules of surface settlement,deformation and force in the support structures and the surrounding rock and identify the best excavation scheme for this tunnel configuration.Results show that to control the surface settlement and the deformation of the support structures,the optimal excavation sequence involves excavating the upper fresh air exhaust tunnel before the lower running tunnel.To control the stress of the support structures,the optimal excavation involves excavating the lower running tunnel before the upper fresh air exhaust tunnel.In this project,the most reasonable excavation sequence of the tunnel is from top to bottom.The most reasonable thickness of tunnel penetration is 5 m.
基金financial supports from the National Natural Science Foundation of China under Grant Nos.51009132,10972221,10672167 and 41172288the National Basic Research Program of China under Grant No. 2014CB046902
文摘Due to the weakness in mechanical properties of chlorite schist and the high in situ stress in Jinping II hydropower station, the rock mass surrounding the diversion tunnels located in chlorite schist was observed with extremely large deformations. This may significantly increase the risk of tunnel instability during excavation. In order to assess the stability of the diversion tunnels laboratory tests were carried out in association with the petrophysical properties, mechanical behaviors and waterlweakening properties of chlorite schist. The continuous deformation of surrounding rock mass, the destruction of the support structure and a large-scale collapse induced by the weak chlorite schist and high in situ stress were analyzed. The distributions of compressive deformation in the excavation zone with large deformations were also studied. In this regard, two reinforcement schemes for the excavation of diversion tunnel bottom section were proposed accordingly. This study could offer theoretical basis for deed tunnel construction in similar geological condition~
基金supported by the National Natural Science Foundation of China(Grant No.52078129).
文摘This study presents the construction of a river channel and a bridge adjacent to existing metro tunnels in Changzhou.The influence of simultaneous construction on these existing tunnels was investigated via 3D numerical modelling to predict tunnel deformation before construction.Then,a targeted protection scheme was developed according to the obtained numerical results.The full construction period field monitoring scheme can monitor tunnel responses during construction.Subsequently,the safety of the tunnel structures was evaluated according to the monitoring results,and the evolution of tunnel deformations was analysed.The analytical results can help to clarify the influence characteristics of different construction stages,verify the effect of the proposed protection scheme,and determine the disturbance mechanism of short-distance pile construction.According to the results,the tunnel deformation mainly occurred during pile construction and river channel excavation,and the tunnel vertical displacement and convergence were mainly affected by the construction.The anti-floating scheme of the partition excavation and casting effectively controlled the tunnel heave with an alarm value of approximately 6 mm.The penetration of the short-distance casing resulted in a tunnel deformation.The main construction influence area of the casing pile was within 6D(D is the pile diameter).