scholarly journals Prototype Experimental Investigation of the Failure Mechanism and Crack Propagation of Segment Lining for Staggered Jointed Assembly

2020 ◽  
Vol 2020 ◽  
pp. 1-14
Author(s):  
Songyu Cao ◽  
Kun Feng ◽  
Xun Liu ◽  
Mingqing Xiao ◽  
Chuan He ◽  
...  
Keyword(s):  
Single Point ◽  
Failure Process ◽  
Safety Evaluation ◽  
Vertical Displacement ◽  
Railway Tunnel ◽  
Slow Increase ◽  
Prototype Test ◽  
Longitudinal Joint ◽  
Control Section ◽  
Three Stages

In order to ascertain the failure characteristics of a segment structure with distributed mortises and tenons, one should be aware of the rules of key parameters and the development of cracks during the failure process. In this paper, based on the Foguan-Guangcheng Intercity Railway Tunnel Project, a prototype test of the structure of a segment with a staggered joint assembly was performed to study the local mechanical characteristics of the segment lining of the vault. The main conclusions were as follows: (1) The failure process in the test was classified as large eccentric compression failure, and the bearing capacity limit was M = 1993 kN m. (2) The overall displacement distribution of the segment structure was funnel-shaped, and the failure process was divided into three stages, that is, the elastic stage, the elastoplastic stage, and the plastic stage. Thus, it is recommended that the index of the single-point displacement limit of this tunnel be reduced appropriately to be between 1.5 and 1.8%. (3) The change rule of the longitudinal joint opening of the segment can be divided into three stages, that is, slow increase, accelerated increase, and sharp increase. For normal use, the limit of the opening of the longitudinal joint is set at 3 mm. (4) The width of the structural crack and the vertical displacement of the control section can be used as the safety evaluation index of this project. When either a large increase in the width of the crack occurs or the displacement specified above is reached, it can be considered that the structure is about to fail, and immediate protective measures must be taken.

scholarly journals Design of a scanning laser meter for monitoring the spatio-temporal evolution of snow depth and its application in the Alps and in Antarctica

2016 ◽  
Vol 10 (4) ◽  
pp. 1495-1511 ◽  
Author(s):  
Ghislain Picard ◽  
Laurent Arnaud ◽  
Jean-Michel Panel ◽  
Samuel Morin
Keyword(s):  
Spatial Variability ◽  
Snow Depth ◽  
Laser Scanning ◽  
Single Point ◽  
Measurement Techniques ◽  
Strong Wind ◽  
Slow Increase ◽  
Automatic Instrument ◽  
Spatio Temporal ◽  
Wind Events

Abstract. Although both the temporal and spatial variations of the snow depth are usually of interest for numerous applications, available measurement techniques are either space-oriented (e.g. terrestrial laser scans) or time-oriented (e.g. ultrasonic ranging probe). Because of snow heterogeneity, measuring depth in a single point is insufficient to provide accurate and representative estimates. We present a cost-effective automatic instrument to acquire spatio-temporal variations of snow depth. The device comprises a laser meter mounted on a 2-axis stage and can scan  ≈  200 000 points over an area of 100–200 m2 in 4 h. Two instruments, installed in Antarctica (Dome C) and the French Alps (Col de Porte), have been operating continuously and unattended over 2015 with a success rate of 65 and 90 % respectively. The precision of single point measurements and long-term stability were evaluated to be about 1 cm and the accuracy to be 5 cm or better. The spatial variability in the scanned area reached 7–10 cm (root mean square) at both sites, which means that the number of measurements is sufficient to average out the spatial variability and yield precise mean snow depth. With such high precision, it was possible for the first time at Dome C to (1) observe a 3-month period of regular and slow increase of snow depth without apparent link to snowfalls and (2) highlight that most of the annual accumulation stems from a single event although several snowfall and strong wind events were predicted by the ERA-Interim reanalysis. Finally the paper discusses the benefit of laser scanning compared to multiplying single-point sensors in the context of monitoring snow depth.

Three Dimensional Elastic-Plastic Numerical Simulation of Tunnel Excavation Sequence of Dalian Speed Railway

2012 ◽  
Vol 170-173 ◽  
pp. 1474-1478
Author(s):  
An Nan Jiang ◽  
Hong Wei Yang ◽  
Hong Fu Xin ◽  
Bing Bai
Keyword(s):  
Numerical Simulation ◽  
Damage Zone ◽  
Three Dimensional ◽  
Ground Surface ◽  
Soft Rock ◽  
Vertical Displacement ◽  
Stability Control ◽  
Surrounding Rock ◽  
Railway Tunnel ◽  
Elastic Plastic

Dalian speed railway tunnel is located in complex soft rock and soil, the road foundation deform and surrounding rock stability control is a concern problem. Along with the unloading process of excavation, surrounding rock moving to inner hole, while exceeding the elastic limitation, the plastic deform and the surrounding rock destroy then occurred. The paper adopted three dimensional elastic-plastic method based on Mohr-Coulomb yielding criterion and carried out numerical simulation of excavation process, in order to analyze and compare the surrounding rock vertical displacement contour, ground surface settlement and damage zone corresponding to different construction sequence. The elastic-plastic numerical method can reflect the damage and destroy character of nonlinear soil material of surrounding rock corresponding to different construction scheme, the simulation result has active guiding meaning for the Dalian speed railway tunnel construction design and dynamic analysis.

The Characteristic Features of Composite Materials Specimen’s Static Fracture Investigated by the Acoustic Emission Method

2012 ◽  
Vol 232 ◽  
pp. 28-32 ◽  
Author(s):  
Alexander Urbahs ◽  
Mukharbiy Banov ◽  
Vladislav Turko ◽  
Kristine Tsaryova
Keyword(s):  
Acoustic Emission ◽  
Composite Materials ◽  
Failure Process ◽  
Unidirectional Composite ◽  
Deformation Curve ◽  
Acoustic Emission Method ◽  
Emission Method ◽  
Static Fracture ◽  
Three Stages ◽  
Characteristic Features

The work is dedicated to the experimental study of micromechanics process of unidirectional composite materials’ specimens under static loading till its fracture using acoustic emission method compared with the strain-load deformation curve. An attempt is made to identify subtle effects of the failure process of the composite material which is impossible using the traditional methods of the strain measurement. The prospect of applying the method of acoustic emission (AE) for the development and improvement of existing methods of model tense- analysis is shown. The characteristic stages of the damage accumulation for unidirectional composites’ specimens and the effect of training on these processes are shown experimentally. It’s shown that the AE-deformation diagram have three stages in contrast to commonly used load-strain deformation curve with one stage. So it become possible to investigate the physical process of composite unit’s fracture under static load.

scholarly journals Influences of High-Speed Train Speed on Tunnel Aerodynamic Pressures

2021 ◽  
Vol 12 (1) ◽  
pp. 303
Author(s):  
Jianming Du ◽  
Qian Fang ◽  
Jun Wang ◽  
Gan Wang
Keyword(s):  
High Speed ◽  
Peak Pressure ◽  
Stage I ◽  
Stage Ii ◽  
Stage Iii ◽  
High Speed Train ◽  
Railway Tunnel ◽  
Maximum Peak ◽  
Train Speed ◽  
Three Stages

To comprehensively investigate the characteristics of aerodynamic pressures on a tunnel caused by the whole tunnel passage of a high-speed train at different speeds, we conduct a series of three-dimensional numerical simulations. Based on the field test results obtained by other researchers, the input parameters of our numerical simulation are determined. The process of a high-speed train travelling through a railway tunnel is divided into three stages according to the spatial relationship between the train and tunnel. Stage I: before train nose enters the entrance; Stage II: while the train body runs inside the tunnel; Stage III: after the train tail leaves the exit. The influences of high-speed train speed on the tunnel aerodynamic pressures of these three stages are systematically investigated. The results show that the maximum peak pressure value decreases with increasing distance from the entrance and increases with increasing train speed in Stage I. There is an approximately linear relationship between the three types of maximum peak pressure (positive peak, negative peak, and peak-to-peak pressures) and the power of the train speed in Stage II. These three types of maximum peak pressure values of the points near tunnel portals increase with increasing train speed in Stage III. Moreover, these three types of maximum peak pressure in the tunnel’s middle section at different train speeds are more complex than those near the tunnel portals, and there is one or more turning points due to the superimposed effects of different pressure waves.

scholarly journals Dynamic Response of Railway Bogie Due to Change in Vertical Primary Suspension Stiffness Parameters

2011 ◽  
Vol 5 (1) ◽  
pp. 19
Author(s):  
Karim H. Ali Abood ◽  
R. A. Khan
Keyword(s):  
Mathematical Model ◽  
Dynamic Response ◽  
Lateral Displacement ◽  
Single Point ◽  
Vertical Displacement ◽  
Roll Angle ◽  
Dynamic Responses ◽  
Model Combination ◽  
Suspension Stiffness ◽  
Yaw Angle

A mathematical model of a railway carriage moving on tangent tracks is constructed by deriving the equations of motion concerning the model in which single-point and two-point wheel-rail contact is considered. The presented railway carriage model comprises of carbody and front and rear simple conventional bogie with two leading and trailing wheelets attached to each bogie. The railway carriage is modeled by 31 degrees of freedom which govern vertical displacement, lateral displacement, roll angle and yaw angle dynamic response of wheelset whereas vertical displacement, lateral displacement, roll angle, pitch angle and yaw angle dynamic response of carbody and each of the two bogies. Linear stiffness and damping parameters of longitudinal, lateral and vertical primary and secondary suspensions are provided to the railway carriage model. Combination of linear Kalker's theory and nonlinear Heuristic model is adopted to calculate the creep forces in which introduced at wheel and rail contact patch area. Computer aided-simulation is constructed to solve the governing differential equations of the mathematical model using Runge-Kutta fourth order method. Principle of limit cycle and phase plane approach is applied to realize the stability and to evaluate the concerning critical hunting velocity at which railway carriage starts to hunt. Numerical simulation model is used to study the dynamic responses of a railway carriage bogie subjected to specific parameters of wheel conicity and primary suspension characteristics. A comparison to study the sensitivity of railway carriage bogie to dynamic responses is also presented at different vertical primary suspension stiffness parameters.

scholarly journals Spatio-temporal evolution of snow depth observed by time-lapse laser scanning in the Alps and in Antarctica

2016 ◽  
Author(s):  
Ghislain Picard ◽  
Laurent Arnaud ◽  
Jean-Michel Panel ◽  
Samuel Morin
Keyword(s):  
Spatial Variability ◽  
Snow Depth ◽  
Laser Scanning ◽  
Single Point ◽  
Measurement Techniques ◽  
Strong Wind ◽  
Slow Increase ◽  
Automatic Instrument ◽  
Spatio Temporal ◽  
Wind Events

Abstract. Although both the temporal and spatial variations of the snow depth are usually of interest for numerous applications, available measurement techniques are either space-oriented (e.g. terrestrial laserscans) or time-oriented (e.g. ultrasonic ranging probe). Because of snow heterogeneity, measuring depth in a single point is insufficient to provide accurate and representative estimates. We present a cost-effective automatic instrument to acquire spatio-temporal variations of snow depth. The device comprises a lasermeter mounted on a two-axis stage and can scan ≈ 200,000 points over an area of 100–200 m2 in 4 hours. Two copies, installed in Antarctica and in the French Alps, have been operating daily, unattended over 2015 with a success rate of 65 % and 90 % respectively. The precision of single point measurements and long-term stability were evaluated to be about 1 cm and the accuracy to be 5 cm or better. The spatial variability in the scanned area reached 7–10 cm (root mean square) at both sites, which means that the number of measurements is sufficient to average out the spatial variability and yield precise mean snow depth. With such high precision, it was possible for the first time at Dome C 1) to observe a 3-month period of regular and slow increase of snow depth disconnected from snowfalls and 2) to highlight that most of the annual accumulation stems from a single event although several snowfall and strong wind events were predicted by the ERA-Interim reanalysis. At last the paper discusses the benefit of the RLS solution compared to multiplying single-point sensors in the context of monitoring snow depth.

scholarly journals The Unified Strength Theory for Plastic Limit Load Analysis of Vertical Shaft Lining

2018 ◽  
Vol 2018 ◽  
pp. 1-6
Author(s):  
Guangsi Zhao ◽  
Minghui Ren ◽  
Xianhao Qiu ◽  
Qinghua Xue
Keyword(s):  
Failure Process ◽  
Safety Evaluation ◽  
Limit Load ◽  
Plastic State ◽  
Practical Case ◽  
Plastic Limit ◽  
Strength Theory ◽  
Unified Strength Theory ◽  
Plastic Limit Load ◽  
Shaft Lining

Plastic limit analysis is a significant application for structural design and failure prediction, implying that the potential bearing capacity of material can be fully considered. Meanwhile, the failure process of structures usually occurs in the deformation of the plastic stage. Hence, it is important to investigate the mechanical properties of structures in the plastic state through proper mechanical models and principles. In this paper, the analytical stress expression and formulas for computing plastic limit load have been deduced based on the unified strength theory. Additionally, the relationships between plastic limit load of the shaft lining and the strength differential (SD) of structural material, the geometrical characteristic (R0/R) and the intermediate principal shear stress (b) have been discussed. Finally, the method of the plastic limit load is adopted for the safety evaluation of the shaft lining through a practical case.

Safety Analysis of Arch Dam

2012 ◽  
Vol 430-432 ◽  
pp. 1818-1821
Author(s):  
Yu Xia ◽  
Ying Ye Yu ◽  
Zhong Qing Zhang ◽  
Xiao Lian Zhao
Keyword(s):  
Specific Gravity ◽  
Safety Factor ◽  
Irreversible Process ◽  
Failure Process ◽  
Safety Evaluation ◽  
Local Deformation ◽  
Arch Dam ◽  
Normal Operation ◽  
The World ◽  
Rcc Arch Dam

Arch dam’s failure is a super nonlinear irreversible process. The failure process of it is quite important for safety evaluation. It analyses overload of the highest RCC arch dam of the world with explicit FEM and shows the process of dam’s failure from normal operation, local deformation to overall failure by water specific gravity overcharge method. It gives a more direct and precisely safety factor. This method is also can be used in other structures.

Research of Embankment Dam Structural Safety

2013 ◽  
Vol 275-277 ◽  
pp. 1525-1530
Author(s):  
Xiu Ying Ding ◽  
Ya Kun Zhang ◽  
Di Zhang
Keyword(s):  
Data Analysis ◽  
Slope Stability ◽  
Structural Stability ◽  
Safety Evaluation ◽  
Horizontal Displacement ◽  
Vertical Displacement ◽  
Structural Safety ◽  
Water Control ◽  
Embankment Dam ◽  
Review Analysis

A concrete embankment dam, for example, to run for the water control dam for many years conducted a vertical displacement, horizontal displacement data analysis and research; and the review of the dam slope stability, structural stability of the main dam crest review, analysis and research of the results,give the conclusion of the reasonable evaluation. Provide reference for the safety evaluation about the aging and dangerous water Construction.

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