This research explores the potential for the evaluation and prediction of earth pressure balance shield performance based on a gray system model.The research focuses on a shield tunnel excavated for Metro Line 2 in Da...This research explores the potential for the evaluation and prediction of earth pressure balance shield performance based on a gray system model.The research focuses on a shield tunnel excavated for Metro Line 2 in Dalian,China.Due to the large error between the initial geological exploration data and real strata,the project construction is extremely difficult.In view of the current situation regarding the project,a quantitative method for evaluating the tunneling efficiency was proposed using cutterhead rotation(R),advance speed(S),total thrust(F)and torque(T).A total of 80 datasets with three input parameters and one output variable(F or T)were collected from this project,and a prediction framework based gray system model was established.Based on the prediction model,five prediction schemes were set up.Through error analysis,the optimal prediction scheme was obtained from the five schemes.The parametric investigation performed indicates that the relationships between F and the three input variables in the gray system model harmonize with the theoretical explanation.The case shows that the shield tunneling performance and efficiency are improved by the tunneling parameter prediction model based on the gray system model.展开更多
A multi-purpose prototype test system is developed to study the mechanical behavior of tunnel sup-porting structure,including a modular counterforce device,a powerful loading equipment,an advanced intelligent manageme...A multi-purpose prototype test system is developed to study the mechanical behavior of tunnel sup-porting structure,including a modular counterforce device,a powerful loading equipment,an advanced intelligent management system and an efficient noncontact deformation measurement system.The functions of the prototype test system are adjustable size and shape of the modular counterforce structure,sufficient load reserve and accurate loading,multi-connection linkage intelligent management,and high-precision and continuously positioned noncontact deformation measurement.The modular counterforce structure is currently the largest in the world,with an outer diameter of 20.5 m,an inner diameter of 16.5 m and a height of 6 m.The case application proves that the prototype test system can reproduce the mechanical behavior of the tunnel lining during load-bearing,deformation and failure processes in detail.展开更多
The control of slurry pressure aiming to be consistent with the external water and earth pressure during shield tunnelling has great significance for face stability,especially in urban areas or underwater where the su...The control of slurry pressure aiming to be consistent with the external water and earth pressure during shield tunnelling has great significance for face stability,especially in urban areas or underwater where the surrounding environment is very sensitive to the fluctuation of slurry pressure.In this study,an optimal control method for slurry pressure during shield tunnelling is developed,which is composed of an identifier and a controller.The established identifier based on the random forest(RF)can describe the complex non-linear relationship between slurry pressure and its influencing factors.The proposed controller based on particle swarm optimization(PSO)can optimize the key factor to precisely control the slurry pressure at the normal state of advancement.A data set from Tsinghua Yuan Tunnel in China was used to train the RF model and several performance measures like R2,RMSE,etc.,were employed to evaluate.Then,the hybrid RF-PSO control method is adopted to optimize the control of slurry pressure.The good agreement between optimized slurry pressure and expected values demonstrates a high identifying and control precision.展开更多
Owing to long-distance advancement or obstacles,shield tunneling machines are typically shut down for maintenance.Engineering safety during maintenance outages is determined by the stability of the tunnel face.Pressur...Owing to long-distance advancement or obstacles,shield tunneling machines are typically shut down for maintenance.Engineering safety during maintenance outages is determined by the stability of the tunnel face.Pressure maintenance openings are typically used under complicated hydrogeological conditions.The tunnel face is supported by a medium at the bottom of the excavation chamber and compressed air at the top.Owing to the high risk of face failure,the necessity of support pressure when cutterhead support is implemented and a method for determining the value of compressed air pressure using different support ratios must to be determined.In this study,a non-fully chamber supported rotational failure model considering cutterhead support is developed based on the upper-bound theorem of limit analysis.Numerical simulation is conducted to verify the accuracy of the proposed model.The results indicate that appropriately increasing the specific gravity of the supporting medium can reduce the risk of collapse.The required compressed air pressure increases significantly as the support ratio decreases.Disregarding the supporting effect of the cutterhead will result in a tunnel face with underestimated stability.To satisfy the requirement of chamber openings at atmospheric pressure,the stratum reinforcement strength and range at the shield end are provided based on different cutterhead aperture ratios.展开更多
Facial support in slurry shield tunneling is provided by slurry pressure to balance the external earth and water pressure.Hydraulic fracturing may occur and cause a significant decrease in the support pressure if the ...Facial support in slurry shield tunneling is provided by slurry pressure to balance the external earth and water pressure.Hydraulic fracturing may occur and cause a significant decrease in the support pressure if the slurry pressure exceeds the threshold of the soil or rock material,resulting in a serious face collapse accident.Preventing the occurrence of hydraulic fracturing in a slurry shield requires investigating the effects of related influencing factors on the hydraulic fracturing pressure and fracture pattern.In this study,a hydraulic fracturing apparatus was developed to test the slurry-induced fracturing of cohesive soil.The effects of different sample parameters and loading conditions,including types of holes,unconfined compressive strength,slurry viscosity,and axial and circumferential loads,on the fracturing pressure and fracture dip were examined.The results indicate that the fracture dip is mainly affected by the deviator stress.The fracturing pressure increases linearly with the increase in the circumferential pressure,but it is almost independent of the axial pressure.The unconfined compressive strength of soil can reflect its ability to resist fracturing failure.The fracturing pressure increases with an increase in the unconfined compressive strength as well as the slurry viscosity.Based on the test results,an empirical approach was proposed to estimate the fracturing pressure of the soil.展开更多
This study aims to investigate hydrofracturing in double-layered soil through theoretical and experimental analysis,as multilayered soils where the difference in mechanical properties exists are generally encountered ...This study aims to investigate hydrofracturing in double-layered soil through theoretical and experimental analysis,as multilayered soils where the difference in mechanical properties exists are generally encountered in practical engineering.First,an analytical solution for fracturing pressure in two different concentric regions of soil was presented based on the cavity expansion theory.Then,several triaxial hydraulic fracturing tests were carried out to validate the analytical solution.The comparison between the experimental and analytical results indicates the remarkable accuracy of the derived formula,and the following conclusions were also obtained.First,there is a linear relationship between the fracturing pressure and confining pressure in concentric double-layered cohesive soil.Second,when the internal-layer soil is softer than the external-layer soil,the presence of internal soil on the fracturing pressure approximately brings the weakening effect,and the greater strength distinction between the two layers,the greater the weakening effect.Third,when the internal-layer soil is harder than the external-layer soil,the existence of the internal-layer soil has a strengthening effect on the fracturing pressure regardless of the proportion of internal-layer soil.Moreover,the influence of strength distinction between the two layers on the fracturing pressure is significant when the proportion of internal-layer soil is less than half,while it’s limited when the proportion is more than half.The proposed solution is potentially useful for geotechnical problems involving aspects of cohesive soil layering in a composite formation.展开更多
基金support by the National Natural Science Foundation of China(Grant Nos.52108377,52090084,and 51938008).
文摘This research explores the potential for the evaluation and prediction of earth pressure balance shield performance based on a gray system model.The research focuses on a shield tunnel excavated for Metro Line 2 in Dalian,China.Due to the large error between the initial geological exploration data and real strata,the project construction is extremely difficult.In view of the current situation regarding the project,a quantitative method for evaluating the tunneling efficiency was proposed using cutterhead rotation(R),advance speed(S),total thrust(F)and torque(T).A total of 80 datasets with three input parameters and one output variable(F or T)were collected from this project,and a prediction framework based gray system model was established.Based on the prediction model,five prediction schemes were set up.Through error analysis,the optimal prediction scheme was obtained from the five schemes.The parametric investigation performed indicates that the relationships between F and the three input variables in the gray system model harmonize with the theoretical explanation.The case shows that the shield tunneling performance and efficiency are improved by the tunneling parameter prediction model based on the gray system model.
文摘A multi-purpose prototype test system is developed to study the mechanical behavior of tunnel sup-porting structure,including a modular counterforce device,a powerful loading equipment,an advanced intelligent management system and an efficient noncontact deformation measurement system.The functions of the prototype test system are adjustable size and shape of the modular counterforce structure,sufficient load reserve and accurate loading,multi-connection linkage intelligent management,and high-precision and continuously positioned noncontact deformation measurement.The modular counterforce structure is currently the largest in the world,with an outer diameter of 20.5 m,an inner diameter of 16.5 m and a height of 6 m.The case application proves that the prototype test system can reproduce the mechanical behavior of the tunnel lining during load-bearing,deformation and failure processes in detail.
基金This work was supported by the Fundamental Research Funds for the Central Universities(2020YJS141)the Key Project of High-speed Rail Joint Fund of National Natural Science Foundation of China under Grant No.U1834208.
文摘The control of slurry pressure aiming to be consistent with the external water and earth pressure during shield tunnelling has great significance for face stability,especially in urban areas or underwater where the surrounding environment is very sensitive to the fluctuation of slurry pressure.In this study,an optimal control method for slurry pressure during shield tunnelling is developed,which is composed of an identifier and a controller.The established identifier based on the random forest(RF)can describe the complex non-linear relationship between slurry pressure and its influencing factors.The proposed controller based on particle swarm optimization(PSO)can optimize the key factor to precisely control the slurry pressure at the normal state of advancement.A data set from Tsinghua Yuan Tunnel in China was used to train the RF model and several performance measures like R2,RMSE,etc.,were employed to evaluate.Then,the hybrid RF-PSO control method is adopted to optimize the control of slurry pressure.The good agreement between optimized slurry pressure and expected values demonstrates a high identifying and control precision.
基金the Major Research of the National Natural Science Foundation of China(No.90715035)HI-Tech Research and Development Program of China(Code 2007AA11Z132).
基金the Major Research of the National Natural Science Foundation of China(No.90715035)HI-Tech Research and Development Program of China(Code 2007AA11Z132).
文摘自然地扔了或剩余土壤比 remolded 泥土展出更多的复杂行为。为结构化的土壤的一个双表面的损坏模型基于在我们的第一份报纸建立的热力学框架被开发。在概括消散的压力空间和实际压力空间之间的移动压力和转变被建立跟随一个系统的过程。建议模型的相应组成的行为被决定，它为 geomaterials 反映内部结构的配置和损坏行为。四进化变量 kij (i = D；R；j=V；S ) 并且基本参数位， s， v 和 e0 被介绍为自然泥土说明内部结构的进步损失。一系列充分， triaxial 测试和各向同性的压缩测试为北京和郑州天赋泥土的结构化并且重新组成的样品被执行。建议模型的确认被把数字结果与试验性的数据作比较检验。
基金The authors gratefully acknowledge financial support from the Joint Funds of the National Natural Science Foundation of China(Grant No.U1830208)the National Natural Science Foundation of China(Grant No.52008021).
文摘Owing to long-distance advancement or obstacles,shield tunneling machines are typically shut down for maintenance.Engineering safety during maintenance outages is determined by the stability of the tunnel face.Pressure maintenance openings are typically used under complicated hydrogeological conditions.The tunnel face is supported by a medium at the bottom of the excavation chamber and compressed air at the top.Owing to the high risk of face failure,the necessity of support pressure when cutterhead support is implemented and a method for determining the value of compressed air pressure using different support ratios must to be determined.In this study,a non-fully chamber supported rotational failure model considering cutterhead support is developed based on the upper-bound theorem of limit analysis.Numerical simulation is conducted to verify the accuracy of the proposed model.The results indicate that appropriately increasing the specific gravity of the supporting medium can reduce the risk of collapse.The required compressed air pressure increases significantly as the support ratio decreases.Disregarding the supporting effect of the cutterhead will result in a tunnel face with underestimated stability.To satisfy the requirement of chamber openings at atmospheric pressure,the stratum reinforcement strength and range at the shield end are provided based on different cutterhead aperture ratios.
基金This research was supported by the National Natural Science Foundation of China(Grant Nos.KCA313017533 and C16A300190).
文摘Facial support in slurry shield tunneling is provided by slurry pressure to balance the external earth and water pressure.Hydraulic fracturing may occur and cause a significant decrease in the support pressure if the slurry pressure exceeds the threshold of the soil or rock material,resulting in a serious face collapse accident.Preventing the occurrence of hydraulic fracturing in a slurry shield requires investigating the effects of related influencing factors on the hydraulic fracturing pressure and fracture pattern.In this study,a hydraulic fracturing apparatus was developed to test the slurry-induced fracturing of cohesive soil.The effects of different sample parameters and loading conditions,including types of holes,unconfined compressive strength,slurry viscosity,and axial and circumferential loads,on the fracturing pressure and fracture dip were examined.The results indicate that the fracture dip is mainly affected by the deviator stress.The fracturing pressure increases linearly with the increase in the circumferential pressure,but it is almost independent of the axial pressure.The unconfined compressive strength of soil can reflect its ability to resist fracturing failure.The fracturing pressure increases with an increase in the unconfined compressive strength as well as the slurry viscosity.Based on the test results,an empirical approach was proposed to estimate the fracturing pressure of the soil.
基金This study was supported by the Key Project of High-speed Rail Joint Fund of National Natural Science Foundation of China(Grant No.U1834208)the Fundamental Research Funds for the Central Universities(2020YJS141)。
文摘This study aims to investigate hydrofracturing in double-layered soil through theoretical and experimental analysis,as multilayered soils where the difference in mechanical properties exists are generally encountered in practical engineering.First,an analytical solution for fracturing pressure in two different concentric regions of soil was presented based on the cavity expansion theory.Then,several triaxial hydraulic fracturing tests were carried out to validate the analytical solution.The comparison between the experimental and analytical results indicates the remarkable accuracy of the derived formula,and the following conclusions were also obtained.First,there is a linear relationship between the fracturing pressure and confining pressure in concentric double-layered cohesive soil.Second,when the internal-layer soil is softer than the external-layer soil,the presence of internal soil on the fracturing pressure approximately brings the weakening effect,and the greater strength distinction between the two layers,the greater the weakening effect.Third,when the internal-layer soil is harder than the external-layer soil,the existence of the internal-layer soil has a strengthening effect on the fracturing pressure regardless of the proportion of internal-layer soil.Moreover,the influence of strength distinction between the two layers on the fracturing pressure is significant when the proportion of internal-layer soil is less than half,while it’s limited when the proportion is more than half.The proposed solution is potentially useful for geotechnical problems involving aspects of cohesive soil layering in a composite formation.
