scholarly journals Displacement Characteristics of Shallow-Buried Large-Section Loess Tunnel with Different Types of Pre-Supports: A Case Study of New Badaling Tunnel

2019 ◽  
Vol 10 (1) ◽  
pp. 195 ◽  
Author(s):  
Daoping Liu ◽  
Dingli Zhang ◽  
Qian Fang ◽  
Zhenyu Sun ◽  
Liqiang Cao ◽  
...  
Keyword(s):  
Cross Sections ◽  
High Speed ◽  
Ground Surface ◽  
In Situ Tests ◽  
Large Section ◽  
High Speed Railway ◽  
Excavation Process ◽  
Ground Surface Settlement ◽  
The Face

Three-bench seven-step excavation method (TSEM) has been widely used in large-section loess tunnels for high-speed railway in China. As the most commonly applied pre-supports, pipe roofs and leading ductules are broadly used in the ground reinforcement of loess tunnels. Their application is to ensure face stability and prevent tunnel collapse during construction. This study focused on the impacts of the TSEM on the ground surface settlement (GSS), as well as the tunnel displacement characteristics for the high-speed railway tunnels with large cross-sections in loess ground. Furthermore, the reinforcement effects of the two kinds of pre-supports were compared in this study. In-situ tests for a total of 12 sections were conducted to reveal the GSSs and displacement characteristics for the shallow-buried large-section loess tunnels. The monitoring results showed that the excavation process plays a significant role on the GSSs and tunnel displacements. A maximum value was observed for the tunnel displacement rate at the excavation of the upper and middle benches, where the face instability or collapse were prone to occur. The GSS trough curves were deviated to the early excavation side, with no conformation to the Gauss distribution. After a series of comparisons, we concluded that the pre-reinforcement effect of the pipe roof is better than that of the leading ductule for the loess tunnels.

Study on the Effect of Jet Grouting Pile Reinforcing Soft Soil Subgrade

2012 ◽  
Vol 594-597 ◽  
pp. 1420-1428 ◽  
Author(s):  
Gang Yu Liu ◽  
Bing Long Wang
Keyword(s):  
High Speed ◽  
Soft Soil ◽  
Ground Surface ◽  
Horizontal Displacement ◽  
Composite Foundation ◽  
Original Design ◽  
Obvious Effect ◽  
High Speed Railway ◽  
Jet Grouting ◽  
Ground Surface Settlement

Composite foundation is commonly used to control the soft soil subgrade settlement. Considering that post-construction settlement of high speed railway is strictly controlled, it’s supposed to use jet grouting pile to strengthen the existed composite foundation and it’s necessary to analyse the effectiveness. Take a line as an example, analyse embankment settlement regularity of the original design mixing pile reinforcement and jet grouting pile reinforcement, evaluate the effect of the jet grouting pile reinforcement. The results show that the jet grouting pile reinforcement on the basis of original design does not have obvious effect on the embankment surface and ground surface settlement control, but effectively controls horizontal displacement at toe of slope and improves the foundation stability.

In-situ investigation on mud pumping in ballastless high-speed railway and development of remediation method

2022 ◽  
pp. 100713
Author(s):  
Zhangbo Wan ◽  
Weichang Xu ◽  
Zhiyuan Zhang ◽  
Chuang Zhao ◽  
Xuecheng Bian
Keyword(s):  
High Speed ◽  
High Speed Railway ◽  
In Situ Investigation ◽  
Mud Pumping

scholarly journals Improvement and In-Situ Application of an Evaluation Method of Ballasted-Track Condition Using Digital 2-D Image Analysis

2020 ◽  
Vol 10 (21) ◽  
pp. 7946
Author(s):  
Bongsik Park ◽  
Yeong-Tae Choi ◽  
Hyunmin Kim
Keyword(s):  
Image Analysis ◽  
High Speed ◽  
Evaluation Method ◽  
Recognition Rate ◽  
High Speed Railway ◽  
Analysis Methods ◽  
Track Condition ◽  
Ballasted Track ◽  
Track Irregularity

The advancement in digital image analysis methods has led to the development of various techniques, i.e., quantification of ballast gravel abrasion. In this study, the recognition rate of gravel aggregates has been significantly increased by improving the image analysis methods. The correlation between the track quality index (TQI), which is the standard deviation of vertical track irregularity and represents the condition of a high-speed railway, and the number of maintenance works was analyzed by performing an image analysis on the samples collected from various locations of a high-speed railway. The results revealed that roundness has the highest correlation with the TQI, whereas sphericity has the highest correlation with the number of maintenance works. The ballast replacement would be performed to improve maintenance efficiency if the abrasion of the ballast aggregates becomes approximately 10%.

Instability Mechanism of Surrounding Rock for Super-Large Cross Section at High-Speed Railway Tunnel Portal

2013 ◽  
Vol 353-356 ◽  
pp. 1597-1603
Author(s):  
Shuang Lan Wu ◽  
Shi Hao Yang ◽  
Xue Wen Zhang
Keyword(s):  
High Speed ◽  
Surrounding Rock ◽  
Instability Mechanism ◽  
Large Cross Section ◽  
Railway Tunnel ◽  
High Speed Railway ◽  
Construction Procedure ◽  
In Situ Conditions ◽  
Major Factors

Difficulties of tunnel construction mainly appear in the entrance and exit stage, some adverse geological problems may occur. In terms of the tunnel at the Changsha-Kunming section of the Shanghai-Kunming passenger line, firstly, adverse geological phenomena at tunnel exits was described. Secondly, major factors leading to disasters were listed, including geology, hydrology and construction procedure. Combined with in-situ conditions, Finite Element Method (FEM) was used to analyze the instability mechanism of surrounding rock after the upper arch gate was excavated by three-bench seven-step exaction method. At last, through comparison between computed result and measuring data, several basic conclusions was obtained. It can make much sense to similar engineering.

Studies on Surface Preparation Systems for Polyurea Protective Coating of Beijing-Shanghai High Speed Railway Bridge Concrete Beams

2012 ◽  
Vol 455-456 ◽  
pp. 765-774
Author(s):  
Wei Bo Huang ◽  
Xu Dong Liu ◽  
Zhang Jing ◽  
Ping Lu
Keyword(s):  
High Speed ◽  
Concrete Beams ◽  
Surface Preparation ◽  
Concrete Surface ◽  
Free Time ◽  
Railway Bridge ◽  
Surface Adhesion ◽  
High Speed Railway ◽  
Comprehensive Performance

. The comprehensive performance of three kinds of surface preparation systems of polyurea coatings for Beijing-Shanghai High-Speed Railway bridge concrete beams’ protection both in situ and in lab were studied in this paper. The pull-off test and visual inspection were used to determine the adhesion and coverage effect of the bug hole of shot blasted concrete surface. Adhesion tests were conducted both in situ and in lab over a period of 1 year. Five failure models were identified based on the failure mechanisms observed during the tests. It showed that, the adhesion strength of Qtech-112 system increased initially (from 2.7 to 4.8 MPa) and then tended to be stable (about 4.5MPa) both in lab and in situ, E1 and E2 system increased initially (from 1.2 to 1.9 MPa) then decreased to 1.3 MPa under low temperature. The tack free time of Qtech-112 was about 3 hours less than E1 and E2 system. Accordingly, the adhesion and tack-free time of epoxy based system (E1, E2) was very sensitive to application temperature and humidity in jobsite. Polyurethane based system (Qtech-112) have a good adhesion and surface coverage effect to concrete surfaces than epoxy based system under the same ambient condition, it showed an excellent comprehensive performance than epoxy one (E1, E2) both in adhesion and in elimination of pinhole for upcoming polyurea application.

scholarly journals Integration of Multiband InSAR and Leveling Measurements for Analyzing the Surface Subsidence of Shield Tunneling at Beijing-Zhangzhou High-Speed Railway

2021 ◽  
Vol 2021 ◽  
pp. 1-24
Author(s):  
Yueguan Yan ◽  
Qian Yang ◽  
Zhihui Jia ◽  
Xiaoyi Zhang ◽  
Huayang Dai ◽  
...  
Keyword(s):  
High Speed ◽  
Ground Surface ◽  
Synthetic Aperture ◽  
Shield Tunnel ◽  
Shield Tunneling ◽  
Modern Life ◽  
Tunnel Excavation ◽  
High Speed Railway ◽  
Synthetic Aperture Radar Interferometry ◽  
Surrounding Environment

In modern life, metro and high-speed rails have become indispensable transportation and have been playing an important role in many areas, especially in cities. The metro and high-speed rails have varying degrees of impact on the surface and surrounding buildings, which must be carefully understood to minimize the risk of hazards. This work is aimed at investigating the deformation of ground surface and the surrounding structures, caused by the excavation of underground tunnels. Because of the spatiotemporal characteristics of the land subsidence induced by underground tunnel construction, the measurements obtained from InSAR (Synthetic Aperture Radar Interferometry) and leveling techniques are integrated to study the subsidence phenomenon of the ground surface above the shield tunnels and the surrounding buildings. The subsidence-related parameters, including the advance angles, lag angles, and boundary angles, are derived from the deformation results. This study suggests that leveling and InSAR observations can provide technical support to study the subsidence of dense buildings on the surface of shield tunnel excavation and to protect the surrounding environment.

scholarly journals STUDY ON LAND SUBSIDENCE INCANGZHOU AREA BASEDON SENTINEL-1A/B DATA

2017 ◽  
Vol XLII-2/W7 ◽  
pp. 675-682
Author(s):  
H. Zhou ◽  
Y. Wang ◽  
S. Yan
Keyword(s):  
Ground Water ◽  
Land Subsidence ◽  
High Speed ◽  
Ground Surface ◽  
Relative Deformation ◽  
The West ◽  
Sar Images ◽  
Annual Average ◽  
High Speed Railway ◽  
Over Exploitation

This paper, obtaining 39scenesof images of the Sentinel-1 A/B, monitored the Cangzhou area subsidence from Mar. 2015 to Dec. 2016 basing on using PS-InSAR technique. The annual average subsidence rate and accumulative subsidence were obtained. The results showed that the ground surface of Xian County,Cang County, Cangzhou urban area had a rebound trend; Qing County, the east of Cang County ,the west of Nanpi County and Dongguang County appeared obvious subsidence, and the accumulated subsidence in Hezhuang village of Dongguang County reached 47 mm. And from that the main reason leading to these obvious subsidence was over-exploitation of ground-water. At last, it analyzed the settlement of the High-Speed Railway (HR) which was north from the Machang town of QingCounty and south to the Lian town of Dongguang County in Cangzhou.The relative deformation of the HR between the two sections which was Lierzhuang village of Cang County and Chenxin village of Nanpi County arrived at 30 mm. Moreover, this paper discussed the application of Sentinel-1 A/B SAR images in monitoring urban land subsidence and the results provided important basic data for the relevant departments.

scholarly journals Experimental Study on Structural Form and Excavation Model of Urban Metro Cross Transfer Station with Super Large Cross Section and Shallow Excavation

2020 ◽  
Vol 2020 ◽  
pp. 1-13
Author(s):  
Zhi Lin ◽  
Xiang Chen ◽  
Hongyun Yang ◽  
Chongguo Cheng ◽  
Huasong Wang ◽  
...  
Keyword(s):  
Large Scale ◽  
Ground Surface ◽  
Construction Method ◽  
Surrounding Rock ◽  
Structure Form ◽  
Large Section ◽  
Response Characteristics ◽  
Ground Surface Settlement ◽  
Transfer Structure ◽  
The Stability

The construction of urban underground cross-interchange transfer subway stations often encounters the difficulties of shallow-buried, different surrounding rock, large spans and heights, congested road traffic, and surrounding buildings sensitive to the construction sequence. Therefore, there is a need for an underground project that controls the stability of underground space and ground subsidence. Based on the construction difficulties of a certain station (the maximum excavation area over 760 m2), this paper conducts a comprehensive selection design of the structure, construction mechanics response, and control technology of this type of interchange station structure and construction excavation. First of all, based on the design experience of large-scale underground transfer transportation engineering and taking full consideration of the stratum conditions, an “arch-wall” cross transfer structure method is proposed. The refined numerical analysis shows that the structure can fully utilize the stratum conditions to reduce the ground surface settlement. Then, in view of the stability of surrounding rock during the construction of a large section, based on the traditional large section excavation method, a construction method of “cross rock beam + heading method” was proposed. In order to verify the effect of the construction method, the three-dimensional detailed numerical model was used to simulate the construction conditions, and the mechanical response characteristics and displacement changes of surrounding rock under each excavation step are explored. Simultaneous interpreting with the traditional large section excavation method, the results show that the new method has advantages in controlling the stability of the surrounding rock. Meanwhile, in order to ensure the safe construction of the project, the self-developed multifunctional engineering test system for traffic tunnels is used to carry out a large-scale physical model experiment to simulate the entire process of the “arch-wall” cross transfer structure construction response characteristics. By analyzing the data of measuring points, the results show that the structure form and the excavation method cause the ground surface settlement, stress, and structural forces meet the requirements for safe construction. Finally, the station can be safely constructed under the new structure form and construction method. Therefore, the structure form and method proposed in this paper can be adapted to the large-scale underground structure under construction in complex environments.

Mud pumping in the roadbed of ballastless high-speed railway

Géotechnique ◽  
2021 ◽  
pp. 1-49
Author(s):  
Xuecheng Bian ◽  
Zhangbo Wan ◽  
Chuang Zhao ◽  
Yujun Cui ◽  
Yunmin Chen
Keyword(s):  
High Speed ◽  
Laboratory Tests ◽  
Fine Particles ◽  
Water Source ◽  
Vicious Cycle ◽  
High Speed Train ◽  
High Speed Railway ◽  
Mud Pumping ◽  
Favorable Conditions

Mud pumping intendedly avoided in the design of a ballastless high-speed railway still occurred and induced extraordinary track vibrations. In this study, in situ investigations and laboratory tests were performed to disclose the initiation and development of mud pumping detected in the field. The in situ investigations indicated that mud pumping principally appeared at both ends of the concrete base up to a maximum distance of 2 m. Precipitation, instead of groundwater, was found to be the water source triggering mud pumping, which infiltrated into the graded gravel roadbed through the detachments of the ends of the overlying concrete bases due to the whipping effect. Once mud pumping occurred, the vibrations of concrete bases were aggravated and caused severe track settlements under train loads. The results of laboratory tests indicated that the infiltrated rainwater was retained in the roadbed above the less permeable subgrade, and the roadbed contained an unstable particle skeleton with excessive plastic fine particles, both of which provided favorable conditions to form mud pumping under dense high-speed train loads. Soil particles less than 7.1 mm in diameter migrated during mud pumping, which first accumulated at the lower roadbed, then gradually migrated to the upper roadbed actuated by generated hydraulic gradient, and finally pumped out through the detachments around the expansion gaps, thereby resulting in large amounts of voids in the roadbed and a vicious cycle if not timely treated. These features of mud pumping in ballastless tracks differ from those of ballasted tracks and will benefit the development of remediation measures and improvement of slab track designs.

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