Changsha Metro Line Research Articles

Impacts of On-board Energy Storage Devices on the Energy Consumption of Train Operations

Urban rail transit systems consume significant electrical power, with traction accounting for 50% of the total energy (from China Urban Rail Transit Association [1]). As operational mileage and vehicle counts rise, so does energy consumption, underscoring the importance of vehicular energy conservation. This study evaluates the impact of on-board energy storage devices on train energy efficiency. Using operational data from Changsha Metro Line 5 and incorporating literature reviews and simulations, the energy-saving potential was assessed. Integrating these storage devices with vehicle energy monitoring systems shows promising potential for energy conservation and operational efficiency. This research presents a viable strategy to reduce energy consumption in urban rail vehicles, enhancing system competitiveness.

Development and evaluation of a process-oriented 3D finite element model for earth pressure balance shield tunneling

Thrust system performs the task of driving the shield machine forward and adjusting its posture, ensuring that the shield advances along a designed tunnel alignment. However, there is still no unanimously agreed approach for incorporating the thrust system in shield tunneling simulation. For this purpose, an attempt is made to embed the parallel mechanism properties of thrust system in simulation, i.e., modeling the thrust system as a 4-spherical-prismatic-spherical (4-SPS) branched chain. Meanwhile, a mesh-to-mesh solution mapping technique is introduced to ensure mesh compatibility across the cutterhead-soil interface without losing the stress history information generated during soil excavation. Thereby, a process-oriented 3D finite element model is developed for earth pressure balance (EPB) shield tunneling. The proposed model is quantitatively evaluated by reproducing a comprehensive field dataset collected from Changsha Metro Line 6 project. It is demonstrated that the proposed model can accurately reproduce the measured data for total thrust, grouped cylinder pressure, and total torque with mean relative errors of 5.8 %, 9.6 %, and 7.8 %, respectively. Moreover, the model can well reproduce the highly varied spatial distribution of the grouped cylinder pressure, highlighting its potential in capturing the mechanics for the posture variation of EPB shield.

Risk assessment of shield tunneling crossing building based on variable weight theory and cloud model

Shield tunneling crossing buildings is a complex process involving multiple influencing factors. The conventional risk assessments for shield tunneling crossing buildings ignore the dynamic changes in index weights and fail to promptly reflect the impact of changes in index status on evaluation results. To solve this problem, a risk assessment model for shield tunneling crossing buildings is proposed based on the variable weight theory and cloud model. Firstly, a risk assessment indicator system for shield tunneling crossing buildings is constructed. The variable weight theory is used to calculate the weights of the evaluation indicators reasonably, taking into account the dynamic changes of the evaluation indicators and their impacts on the evaluation results. The cloud model theory is introduced to solve the randomness and fuzziness in the risk assessment of shield tunneling crossing buildings. The new model is applied to a case study of the risk assessment of shield tunneling crossing buildings during the construction of the Changsha Metro Line 4. Compared with the traditional weight model, the variable weight theory model calculates the weights of the indicators more reasonably. At the same time, it is verified that the model has good applicability and accuracy in the risk assessment of shield tunneling crossing buildings. This model provides a new approach to guide the safe operation management and disposal decision-making of shield tunneling crossing buildings.

Improved multi-objective grasshopper optimization algorithm and application in capacity configuration of urban rail hybrid energy storage systems

Aiming at addressing problems of poor diversity and ergodicity of initial population, slow convergence speed, and susceptibility to local optima in conventional multi-objective grasshopper optimization algorithm (MOGOA), an improved MOGOA is proposed in this paper. The proposed algorithm is based on Sobol sequence, adaptive social force, cosine parameter c, as well as Levy flight mechanism (SACLMOGOA), where Sobol sequence is adopted to initialize the population, thereby improving the diversity and ergodicity of the initial population. The adaptive social force is proposed to enhance the global exploration ability in the early stage of iteration and the local development ability in the late stage of iteration. A cosine type parameter c is used to ensure sufficient exploration time and rapid convergence of the algorithm during position update process and Levy flight is used to guide some grasshoppers to mutate, enhancing the ability to escape from the local optima and improving the performance and efficiency of the algorithm. The proposed algorithm is tested with ZDT and DTLZ series benchmark test functions to validate its effectiveness, and it is also compared with conventional MOGOA, multi-objective particle swarm optimization, multi-objective gray Wolf, and multi-objective jellyfish algorithms. The simulation results demonstrate that the proposed algorithm outperforms other algorithms in terms of inverse generational distance (IGD), spread (SP), maximum spread (MS), run time and Wilcoxon rank sum test. Furthermore, the proposed algorithm is successfully applied to the capacity configuration of the urban rail hybrid energy storage systems (HESS) of Changsha Metro Line 1 in China, reducing the traction network voltage fluctuations by 3.3 % and 2.2 % compared to no HESS capacity configuration optimization, and by 14 % and 5.7 % compared to no HESS during train starting and breaking, respectively. While achieving the goal of energy-saving and voltage stabilization, the cost of the hybrid energy storage systems is minimized as well. All of these have demonstrated SACLMOGOA is an effective tool for solving complex multi-objective optimization problems in engineering.

Numerical Simulation of Flood Control Levee Deformation by Shield Tunnel Excavation through the Liuyang River: A Case Study

The interval section of the Liuyang River flood control levee project of the Changsha Metro Line 6 is used as the engineering background of this study. A three-dimensional finite element numerical model of a tunnel shield containing complex interfaces is established by using the multifield coupling software COMSOL. The paper studied the deformation of flood control levees under shield tunnel excavation working conditions. The results show that when the left line shield machine is excavated below the Liuyang River flood control levee, the deformation of the flood control levee and the surrounding rock of the tunnel is biased towards the built right line tunnel. And it has an impact on the bridge pile near the tunnel. When the shield of the left line crosses the flood control levee, it can easily cause a large deformation and displacement of the levee above the area between the two shields. To ensure the controlled deformation of the levee, the construction should ensure the spacing between the two tunnel palm faces as far as possible and should be far away from other structures on the levee. When the shield crosses the levee, the deformation that occurs at the base of the levee is significantly higher than the deformations that occur at other locations of the levee. Displacement monitoring and secondary reinforcement at the base of the flood control levee appear to be necessary. The numerical simulation results validate the feasibility of using the multifield coupling software COMSOL to study the construction modeling of shield tunnels through rivers and its advantages. This method provides a practical framework for similar tunnel performance engineering or displacement monitoring in future projects.

Effects of Different Construction Sequences on Ground Surface Settlement and Displacement of Single Long Pile due to Twin Paralleled Shield Tunneling

Shield tunneling activities inevitably pass through pile foundations at close distance in densely urban areas. Various studies have investigated the interaction between newly constructed tunnels and existing pile foundations. However, the influence of different construction sequences of twin paralleled shield tunneling on single long pile is seldom considered. A case was found in the project of Changsha Metro Line 5, where the twin paralleled tunnels were constructed near the Wanjiali Viaduct piles. A three-dimensional finite element model was established to analyze the pier settlement, ground surface settlement trough, and the vertical and horizontal displacement of pile under different construction sequences in layered soil. The results show that the adjacent pile and surrounding environment are affected substantially with the change of construction sequence of twin paralleled tunnels. The construction sequence of condition (b), in which the tunnel closer to the pile foundation is first constructed and then the tunnel farther away from the pile foundation is second constructed, can reduce the settlement of pier by 13.1%, the maximum surface settlement by 7.0%, the maximum vertical displacement of pile foundation by 7.9%, and the maximum horizontal displacement by 6.9%. The present findings can provide reference for similar projects.

Explainable data-driven optimization for complex systems with non-preferential multiple outputs using belief rule base

To better handle problems with non-preferential multi-outputs (NPMO), a new approach is proposed in this study by employing the belief rule base (BRB) to provide a superior nonlinearity modeling ability as well as good explainability. The new approach is thus called NPMO–BRB. First, a new optimization model is constructed where the optimization objective is the integration of multi-outputs and respective constraints are designed. Then, a new optimization algorithm with a new customized gene makeup is designed where the NPMO–BRB inferencing process is embedded in the fitness calculation procedure. A practical case study on Changsha Metro Line 4 is studied to use multiple geological parameters to infer multiple operational parameters. Case study results show that NPMO–BRB has shown superior performance in comparison with the random forest (RF), the backpropagation neural network (BPNN), the Gradient Gaussian Process (GPR), as well as multiple separate BRBs. Owing to the explainability provided by the NPMO–BRB approach, further investigations into the belief distribution comparison reveal more information that can be used as practical work guidelines.

Development and application of a multi-sensor integration detection and analysis device for metro gauge and track geometric state

In order to ensure the safe operation of subways, it is necessary to detect the metro gauge and track geometry in time. However, the manual detection and the large rail inspection car is inefficient and expensive. Therefore, we have developed a multi-sensor integration detection and analysis device. Sensors, such as a laser scanner, a gauge sensor, an angle sensor, and a single-chip computer, are integrated into a rail inspection trolley, and the functions of gauge detection, gauge analysis, rail gauge calculation, and superelevation calculation are realized. Through the calibration of an odometer and a sensor, the accuracy of the device can meet the requirements of the standard. The device is applied to Changsha Metro Line 3 to detect and analyze the gauge and track geometry state. Finally, the device realizes the functions of the gauge intrusion alarm, automatic input of graphics and gauge intrusion data, automatic identification of sleepers, and automatic collection of track geometry data.

Predictive model for the surface settlement caused by the excavation of twin tunnels

It is of great difficulty to accurately predict the stratum deformation caused by double-track or twin-tunnel construction because of the complex coupled interaction of the two tunnels. Although green-field ground movements can be well fitted using established empirical methods, the disturbance caused by the excavation of the first tunnel is expected to affect the soil deformation close to the second tunnel. Due to the lack of consideration of the influence of secondary disturbances, the computed results of conventional prediction methods often lead to large errors when compared to measured results. Based on the Peck formula, this paper first clarifies the influence mechanism of twin-tunnel excavation. The model is then calibrated using field data from a twin-tunnel excavation in Wuhan city. With the concern of disturbance due to prior tunnel excavation, the disturbance correction factor η(x) is introduced to deduce a prediction formula for the ground surface deformation caused by twin-tunnel construction. Finally, the proposed theory is verified based on the field measurements of a practical case study of the Changsha Metro Line 2 Project.

Evaluation of the land value-added benefit brought by urban rail transit: The case in Changsha, China

Accurate evaluation of land value-added benefit brought by urban rail transit (URT) is critical for project investment decision making and value capture strategy development. Early studies have focused on the value impact strength under the assumption of the same impact range for all stations. However, the value impact range at different stations may vary owing to different accessibilities. Therefore, the present study releases this assumption and incorporates the changed impact range into the land value-added analysis. It presents a method to determine the range of land value-added impact and sample selection using the generalized transportation cost model, then spatial econometric models are further developed to estimate the impact strength. On the basis of these models, the entire value-added benefit brought by URT is evaluated. A case study of the Changsha Metro Line 2 in China is discussed to demonstrate the procedure, model, and analysis of spatial impact. The empirical analysis shows a dumbbell-shaped impact on the land value-added benefit along the transit line with a distance-dependent pattern at each station. In addition, the land value-added benefit from Changsha Metro Line 2 reached 12.099 billion USD. Lastly, two main value-added benefit capture modes are discussed, namely, land integration development and special land tax.

Design and Application of Risk Early Warning System for Subway Station Construction Based on Building Information Modeling Real-Time Model

The problems faced by subway stations in the construction process are more complex than those by overground buildings. Therefore, the construction risk for such structures is highly unpredictable and the risk management is difficult. Building information modeling (BIM) technology has strong visualization, simulation, and integration characteristics that make it conducive to the development of a risk early warning system for underground engineering. According to the functional requirements of risk early warning for subway stations, a risk early warning system based on a BIM real-time construction model is designed in this study for a subway station construction. The operation process of the risk early warning system is established through the grey prediction method to propose the operation method of the early warning system. The early warning system is applied to the Xiangjiang New Town Station of Changsha Metro Line 4 in China to verify its feasibility.

Comparative Study on Grouting Protection Schemes for Shield Tunneling to Adjacent Viaduct Piles

Shield tunnels will inevitably pass through viaduct piles at a close distance due to the extensive construction of subways and viaducts in the city. In order to understand the influence of shield tunneling on the deformation of existing pile foundation and grouting protection measures, based on an engineering case, Changsha Metro Line 5 (from South Gaoqiao station to Guitang station), a three‐dimensional finite element model was established to analyze the deformation of bridge pile using grouting protection wall with different depths and shapes when the shield tunnel is under construction. The analytical results indicate that the grouting protection wall can effectively reduce the pile displacement; especially the grouting depth is 3 m below the bottom of the tunnel. Moreover, the L‐shaped grouting protection wall can effectively reduce the longitudinal displacement of the piles. The present findings may provide a reference for the design and construction of shield tunnels passing through viaduct piles.

Zone Fare System Design in a Rail Transit Line

As a widely existing form of public transit fare structures, zone fare system is traditionally designed in a separate way, which may lead to suboptimal results. This paper aims to concurrently address the zone division and fare calculation issues of the zone fare system design in a rail transit line. It is necessary to consider passengers as well as operators to find an impartial zone fare system. A fair zone fare system is one where the zone fares are as close as possible to the distance-based fares, for the fares of the distance-based fare system are highly correlated with the actual distance of trips. Thus, the fare deviations for the trips between the zone fare system and the distance-based fare system are utilized as the evaluation metric of fairness. To achieve the goal of minimizing fare deviations for all trips, we introduce three indexes: average absolute deviation, average squared deviation, and maximum mileage fare deviation. With the three indexes as the objective functions, we develop a joint optimization algorithm where a novel zone boundary adjustment scheme is proposed as the key technique. Numerical results show that the proposed algorithm can effectively provide a joint optimal scheme and the optimal number of planned zones is 5 for Changsha Metro Line 2. The proposed algorithm can provide guidance for the practical design and adjustment of the zone fare system.

Study on Influence of Construction Process of Double-Line Shield Tunnels on Frame Structure

This paper presents a study of the influence on stress and deformation of the frame structure induced by double-line shield tunnels during tunneling. Using the finite element software MIDAS/GTS, the construction process of double-line shield tunnels passing through the adjacent frame structure with a strip foundation was simulated. By comparing the ground settlement monitoring data of a building passing through Changsha Metro Line 2 with the numerical simulation results, it is found that the Midas GTS/NX finite element analysis is reliable and can be used to predict the impact of shield tunneling on the frame. The location and construction sequence of double-line shield tunnels were varied to investigate the response of frame structure. The results of the analysis are as follows: (1) the position and value of the maximum stress of the frame structure are different in different excavation locations. Under the condition that the left tunnel passes under the frame structure and the right tunnel passes through from the side of the frame structure, the maximum stress of the frame structure has the minimum. (2) The frame structure inclined towards the tunnel when double-line tunnels pass-through from the side of the frame structure. Under the condition that the left tunnel passes under the frame structure and the right tunnel passes through from the side of the frame structure, the frame structure produced the longitudinal inclination. (3) The maximum settlement of the strip footings locates the ①-axis position when double-line tunnels pass-through from the side of the frame structure. The maximum settlement of the strip footings locates the ⑤-axis under the condition that the left tunnel passes under the frame structure and the right tunnel passes through from the side of the frame structure. The maximum settlement of the strip footings locates the ⑥-axis position when the double-line tunnels pass under the frame structure. (4) Under the condition that the double-line tunnels pass-through from the side of the frame structure, the impact of different construction sequences on the frame structure is slightly different. The construction sequence of the synchronous excavation of two lines in the opposite direction is more likely to cause that the frame structure inclines to the tunnel during tunneling.

Design and Application of Automatic Monitoring System based on Static Force Level in Construction of Shield-bored Underneath Metro

When metro shield passes through existing operating lines, it is necessary to carry out automatic monitoring of existing lines. In this paper, taking the construction of Changsha Metro Line 4 under the shield of the existing Metro Line 2 as an example, the static level is set up in the construction affected area to monitor the vertical displacement of the track bed automatically. According to the actual situation of the site, a complete set of automatic monitoring system is designed, and a detailed site implementation scheme is formulated. Finally, the deformation data is analysed, and the characteristics of the whole system are summarized.

Optimizing Bus Line Based on Metro-Bus Integration

Metros are usually built and added on the basis of a completed bus network in Chinese cities. After the metro construction, it is faced with the problem of how to adjust and optimize the original bus lines based on the new metro system. This research mainly proposes a bus line optimization method based on bus and metro integration. In the consideration of the geographical space, the cooperation and competition relationship between bus and metro lines is qualitatively introduced according to the geographical location and service range of metro (800 m radius) and bus (500 m radius) stations. The competition and cooperation indexes are applied to define the co-opetition relationship between bus and metro lines. The bus line optimization model is constructed based on the co-opetition coefficient and Changsha Metro Line Number 2 is chosen as a case study to verify the optimization model. The results show that the positive competition, efficient cooperation, and travel efficiency between metro and bus has been significantly enhanced after optimization. Moreover, this paper provides a reasonable reference for public transport network planning and resource allocation.

Design and Application of Automatic Monitoring System based on Total Station in Construction of Shield-bored Underneath Metro

When metro shield passes through existing operating lines, it is necessary to carry out automatic monitoring of existing lines. Taking Changsha Metro Line 4 shield tunnelling through existing Metro Line 2 as an example, this paper carries out automatic deformation monitoring of existing Metro and judges the influence of shield tunnelling on existing Metro. According to the actual situation of the field, a whole set of automatic monitoring system is designed, and the detailed implementation plan is worked out. Finally, the deformation data are analysed, and the characteristics of the whole system are summarized.

Geological Disaster Survey and Treatment Strategies of Yingwanzhen Subway Station, Changsha

In order to solve such problems as ground subsidence, water and mud bursting and shield machine foundering in subway construction which are caused by water-rich karst geological conditions, complete technological process is established to detect and treat karst in urban areas. The occurrence of natural electric field frequency selection method and groundwater determine groundwater occurrence vector that karst and fault fracture zone, and make use of the grouting technology of karst fracture with the treatment. The construction of Yingwanzhen Stationon Changsha Metro Line No. 4 provesthe favorable effect of the detection technology and treatment measures, which provides experience and reference for the construction of Changsha subway and underground engineeringin other cities with water-rich karst areas.

Real-time analysis and regulation of EPB shield steering using Random Forest

Abstract Settlement control is an essential part of the tunnel construction process. This paper proposes two novel computational models based on the Random Forest (RF) algorithm for supporting automatically steering Earth Pressure Balanced (EPB) shield. The first model is utilized for predicting tunneling-induced settlement and the other estimates shield operational parameters. A PSO-RF hybrid algorithm which intergrates the Particle Swarm Optimization (PSO) and the RF algorithms is proposed to optimize shield operational parameters when the settlement exceeds the tolerated value. The proposed models are adopted in the case study of Changsha Metro Line 4 project. The results indicate that the predicted settlements show great agreement with the measured settlements. The face pressure and grout filling are the most significant shield operational parameters to control the settlement as a result of Global Sensitivity Analysis (GSA). The anomalous settlement (≥10 mm) can be controlled under tolerated value after the face pressure and grout filling values are optimized by the PSO-RF hybrid algorithm. Simultaneously, the consistency of the face pressure and grout filling values calculated by the PSO-RF and the grid search method demonstrates the feasibility and applicability of proposed hybrid algorithm.

Research of the Spray Curing System of Concrete Based on Fuzzy Control

In order to improve the efficiency of concrete curing and reduce the generation of cracks, a set of concrete spraying curing device is designed and developed by using computer control technology. The device can monitor the temperature and humidity of concrete in real-time and automatically control the spraying time according to the fuzzy control theory, so as to realize the intelligent curing of concrete. In the application of concrete curing on the side wall of Hanwangling station of Changsha metro line 4, it is verified that the maintenance system has obvious effects of spraying and moisturizing, reducing the generation of cracks and ensuring the construction quality of concrete.