High-speed Railway Construction Project Research Articles

Experimental Study on the Dynamic Characteristics of a New Long-Short Pile Composite Foundation under Long-Term Train Load

Long-short pile composite foundation (PC-LSPCF) composed of part-screw pile and cement-soil compaction pile is a new railway foundation treatment method, which has been widely used in high-speed railway construction projects in China. To explore the dynamic characteristics and deformation characteristics of railway PC-LSPCF under long-term train loads, the dynamic characteristics of long piles, short piles, and soil between piles under long-term train loads are tested by an indoor dynamic model test. The dynamic amplification of pile and soil under dynamic load and the temporal and spatial distribution of peak response are analyzed, and the stress and deformation development mechanism of PC-LSPCF under cyclic loading of large-cycle trains is revealed. The results show that the neutral point of the long pile is at 1/2 of the pile length and that of the short pile is at 3/8 of the pile length. The part-screw pile has a certain absorption effect on vibration energy. The deformation of a long-short pile composite foundation under long-term train loads can be divided into three stages: extreme growth, transition, and stability. The train speed is negatively correlated with the cumulative settlement of the long-short pile composite foundation. The higher the train speed, the smaller the cumulative settlement, and the smaller the number of cycles of the N-S curve entering the gentle period. As the number of train cyclic loads increases, the load-sharing relationship of the long pile-short pile-soil system will be redistributed. The research results have important reference significance for the optimization design of high-speed railway foundation treatment.

Field Research on the Treatment of Coastal Phase Liquefaction Foundation with Clay Interlayer Using Resonance Probe Compaction Method

The resonance probe compaction (RPC) method is an effective technique for particular soils, which mainly includes sandy and loess. However, the application of RPC on contaioning clay interlayer area has never been seen. In this study, a successful case of using the RPB method to treat the clay interlayer foundation is presented in detail. The test results of Huaiyan high-speed railway construction project are introduced. The test is divided into the laboratory test and the field test, mainly including standard penetration test (SPT), cone penetration test (CPT) and seismic wave cone penetration test (SCPT). The test results indicated that the cone resistance of silt and silty sand layers increased to an average of 2.13 times compared with an average of 4.39 MPa before treatment, and the sleeve friction whose initial average is 54.17 kPa increased to an average of 1.74 times. The existence of the clay interlayer does not affect the consolidation and drainage of the silt layer and the silt sand layer, and after the construction, the excess pore water pressure around the vibration point can be dissipated by more than 90% within 15 minutes. After reinforcement, the standard penetration number of subsoil, increased by about 15%–95% compared with an average of 19 blows before treatment and the clay particle content of some clay interlayers are reduced to less than 10%. The shear wave velocity of the subsoil in the treatment depth increased by about 15%–48% compared with 140 m/s before treatment. The RPC method was successful for the coastal phase liquefaction foundations.

Resilience Evaluation of High-Speed Railway Subgrade Construction Systems in Goaf Sites

When the high-speed railway construction project passes through goaf sites, the uncertain impacts from internal and external environments faced by the system are gradually characterized by complexity and variability, and the disastrous consequences are becoming increasingly prominent. The risk resistance ability and accident recovery ability of the high-speed railway subgrade construction system are crucial for improving the safety management level of the construction site. Based on the concept of resilience, this paper discusses the connotation of resilience applicable to the construction system of high-speed railway foundations in goaf sites, and an evaluation index system including 25 indicators is constructed. Then, the resilience evaluation model is constructed by ANP, entropy weight method and fuzzy comprehensive evaluation method. Taking the construction system of Taijiao high-speed railway subgrade in the underlying goaf as an example, this model is verified. The verification results show that the grade of construction system is II (high resilience). The evaluation result is consistent with the actual engineering situation, and the evaluation model is effective. It can be used as a theoretical basis for safety management of high-speed railway construction projects, and a full process analysis method based on resilience theory is established.

Research on Dynamic Response and Construction Safety Countermeasures of an Adjacent Existing Line Foundation under the Influence of a New Railway Line

The excavation of a new high-speed railway causes the side slope adjacent to the existing line foundation to become airborne, and the excessive dynamic deformation or cumulative deformation caused by the dynamic load of trains will affect the normal service of the subgrade, even leading to its instability. To date, there are no relevant experimental data regarding this, and there is also a lack of corresponding specifications. The only available numerical simulation research results need to be verified in practice. Therefore, this study relies on the Shanghai–Nanjing intercity high-speed railway construction project adjacent to the existing Beijing–Shanghai line to carry out a subgrade dynamic response test to ensure the safe operation of the existing line. The test obtained the vibration displacement, frequency, acceleration, and other parameters of the existing subgrade construction in three stages: subgrade excavation, pile formation, and subgrade filling. From the test results: During the test period, the vertical surface vibration displacement and vibration acceleration have a certain attenuation along the depth direction. In the stage of subgrade excavation, the vibration displacement and vibration acceleration generated are the largest. The vertical vibration displacement amplitude reaches 1.9 mm, and the horizontal vibration displacement amplitude reaches 0.15 mm. The vibration frequency of the roadbed under the action of the train load is concentrated in the range of 0–50 Hz, and the vibration energy at the peak value is relatively large, which reflects the load action frequency of the train, and the peak value is mainly concentrated in the range of 20–40 Hz. These results show that the maximum vibration response peak appears in the subgrade excavation stage, that is, the most dangerous stage of the existing subgrade. The vibration acceleration and vibration displacement of each dynamic response parameter are important in that they reflect the dynamic performance of the subgrade and establish the index control standard, which can be used as a control index for roadbed dynamic stability monitoring. The dynamic test of the subgrade state provides data support for the reasonable opening of the construction skylight and the protection of the excavation slope. Taking into account the impact of piling vibration, technical measures such as static pressure, jumping construction, and setting up stress relief holes are adopted. The test results and engineering measures ensure the safe operation of the existing subgrade, and have important theoretical significance for guiding the construction of the new subgrade adjacent to the existing line.

Is Resilient Transportation Infrastructure Low-Carbon? Evidence from High-Speed Railway Projects in China.

Establishing resilient transport infrastructure is an effective way for cities to deal with external disturbances and uncertainties during rapid urbanization. However, human society is presently facing a series of sustainable development obstacles, where the energy shortage and environmental pollution are catching significant concerns. Hence, it is imperative to investigate the carbon emission of the growing number of resilient transportation infrastructure (RTI) projects. Through extracting the carbon emission factor (CEF), this study built the carbon emission measurement model (CEMM) to evaluate the carbon emission of 26 resilient high-speed railway construction projects in China. The results indicated that the carbon emissions of the entire high-speed railway infrastructure projects in China show regional and social environmental differences. Meanwhile, there are potential correlations and positive relationships between the resilience of the high-speed railway infrastructure projects and their carbon emission. Suggestions and recommendations for governments and construction enterprises are put forward to further improve the resilient and low-carbon development of transportation infrastructure in China.

Fiscal policy and the development of green transportation infrastructure: the case of China's high-speed railways

High-speed rail (HSR) has been highly valued as an accelerator of green economic growth. However, the difficulty in financing caused by the high investment demand and long construction cycle of high-speed rail is an ongoing dilemma facing the high-speed rail industry. Using data from Chinese cities from 2003 to 2018, this paper explores whether fiscal policy is conducive to solving financing problems for high-speed railway construction. At the same time, this paper investigates the economic and environmental benefits of high-speed rail construction investment for urban development. We find that fiscal policy helps reduce the financing cost of high-speed railway construction projects and attracts social capital, spurring investment in high-speed rail construction. When economic policy uncertainty rises, companies will choose more secure, "safe" investments to avoid potential risks, such as government-led high-speed rail construction projects, which has led to their further expansion. Regarding its economic effect, high-speed rail construction investment directly promotes urban productivity, investment scale, and industrial structure upgrades. Over the long term, investment in HSR construction helps curb urban pollutant emissions, thus contributing to urban eco-efficiency.

Development of risk-based standardized Work Breakdown Structure (WBS) to improve time performance on high-speed railway construction project

In Indonesia plans and studies for High Speed Railway (HSR) are not a new idea as they have been conducted before 2010. However, the plan to build HSR was just recently announced in 2015. Specifically, for the high-speed railway construction project in Indonesia, there is no standards that contains details of work activity packages and their methods for carrying out work in the field. This resulted in every railway-based construction project still using several methods from both overseas and Indonesian domestic experiences. Therefore, it is now necessary to standardize both the methods and work activities and suggested to be implemented for any highspeed railway project so that the work breakdown structure (WBS) can be standardized for any future rail and rail-based construction project. This can also minimize any potential risks and ensure the project is completed according to the targets in terms of quality, cost, and time. The methodology used in this study are to identify risks at construction project with a WBS matrix (observation and questionnaire). Analysis data in this study used statistical analysis. The result of this study is 15 risks selected from the 3 highest risks and 1 risk representing each category. The 3 (three) highest are Delay in issuing designs by the planner / designer, Delay in land acquisition by the project owner, Work activity has stopped due to weather factors. Risk representing each category are The subcontractor’s productivity does not match planning (Work packages), Delay in issuing designs by the planner / designer (Method/design), Work activity has stopped due to weather factors (Activity), Delay from suppliers in delivering material (Material resources), The planned productivity of equipment is not as needed (Equipment resources) and Human productivity is lower than demand (Human resources).

Specific features of high-speed railway construction projects

The most important condition for the integration of the Russian transport infrastructure into the global logistics chain is the design and construction of high-speed railways. In the course of this research, the problems of implementation of high-speed highway “Moscow-Kazan” project by “High-speed Rail Lines” Joint stock Company were considered, and the necessity of large scale projects realization on high-speed railways construction was defined.Then, the aggregate demand values were determined, and the distribution of traffic between different transportation modes was predicted. Finally, the induced demand value was forecasted. Based on the predicted passenger flow characteristics, the indicators of train traffic were calculated.The passenger traffic on the road segment between Moscow and Kazan was studied. The methodology for passenger traffic calculation included the calculation of the induced demand, the possibility of passengers choosing the railway over other modes of transportation, and the evaluation of the demand fluctuations dynamics.The scientific novelty of this study is the application of an improved method of statistical analysis in the calculation of passenger traffic. Along with the theoretical results, the carried out research has an utmost practical importance-its results can be applied in the design of main railways.

Slope Stability of Embankments on Soft Soil Improved with Vertical Drains

The overloads of structures or embankments built on clayey soft ground are generally applied gradually, respecting a specific phasing. This phasing on construction allows the undrained shear strength of clay increasing over consolidation in order to avoid the risk of collapse during loading. In this work, the undrained shear strength of clay over the consolidation was estimated following SHANSEP method of which parameters proposed by eight researchers have been employed, as well as the slope stability analysis of embankments on soft soils during staged construction. Assessment of factor of safety for slope stability was conducted basing on the Bishop method. Additionally, the variations of undrained shear strength and factor of safety were presented. In order to validate the methods discussed in this study, slope stability analysis of five embankments constructed on clayey soft soils improved by the vertical drain technique in a high-speed railway construction project in Morocco was performed. For these embankments, field measurements about lateral displacement are presented. It was found that some of the adopted methods is in a good agreement with field measurements. Hence, generalization of these methods to many soft ground cases can be proposed.

Knowledge-based Minimization of Railway Infrastructures Environmental Impact

Life Cycle Assessment (LCA) and intelligent data analysis can help in reducing carbon and water footprints of rail infrastructure construction projects. The goal is to improve the railway construction processes with regard to their environmental impact, mainly in those aspects related to climate change such as carbon and water footprints.Based on a set of 27 indicators of every task in the construction process, a comprehensive compilation of basic information was performed, where the main project units and their sub-tasks were reviewed and analyzed.Afterwards, focus was on analyzing the transformation from environmental impact to carbon and water footprints, by means of the development of a consolidated evaluation methodology. A tool is being developed based on data mining and computational intelligence approaches. It will allow knowledge-based alternative project units scheduling, conditioned to previously selected specific footprint values and environmental indicators. This decision support system (DSS), based on multi-criteria and multi-objective intelligent optimization algorithms, will help to reduce carbon and water footprints of rail infrastructure construction projects by around 10% and 5%, respectively.Tests are going to be performed on two real high speed railway construction projects. That way, a global search procedure provides an analysis of the best alternatives in the scheduling and execution of the project units and their environmental impact offering a front of solutions displaying different trade-off amongst several ‘footprints’.Results will allow the development of a series of environmental impact indicators, which will support rail infrastructure construction companies becoming more sustainable and efficient by minimizing their environmental impact.

Roles of owners' leadership in construction safety: The case of high-speed railway construction projects in China

Owners' role in project safety improvement is drawing increasing attention in the academia. Their greatest leverage is the leadership to influence safety perception, motivation and behavior of other stakeholders. However, previous studies have not paid enough attention to owners' leadership and its impacting mechanisms, nor have they identified effective leadership behaviors related to high safety performance. This paper seeks to present a comprehensive interpretation of owners' role in construction safety by identifying their effective leadership practices and specific managerial measures. A case study was undertaken on Chinese high-speed railway construction projects currently undergoing significant safety improvement thanks to their owner's commitment to safety. The ethnographic research method was applied to collect empirical data, i.e. the owner's safety leadership and management practices. Based on grounded theory, four categories of safety leadership practices were identified to interpret what types of leaders are required in construction projects. Four safety managerial chains driven by safety leadership were synthesized. They give insights into the measures which owners can implement to improve construction safety. Concrete and specific measures were explored for construction owners, especially those in developing countries, to enhance their safety leadership and management. These findings can be used by construction owners to improve their safety leadership and reinforce their involvement in project safety management, especially when their industry is facing significant safety challenges and demanding transformational development.

Back Analysis of Parameters and Settlement Prediction of Chengdu Clay Ground Considering Its Creep Behavior

Chengdu - Mianyang – Leshan (C-M-L for short) high speed railway in Chengdu section is located in the ground of weathered Mud rock overlying deep Chengdu clay area. Based on Chengdu clay ground of in high-speed railway construction project of CML, this article introduced the Burgers model to establish the objective function to analysis rheological constitutive model. The visco-elastic parameters of Burgers model are determined by back analysis of field monitoring data. By the method of iterative back analysis by layer of visco-elastic parameters, based on measured result, predicted the late settlement, and comparison with the follow-up observations records to verify the Burgers model.