scholarly journals Investigation of Concrete Base-Roadbed Surface Contact Variation-Induced Vibration Characteristics of Vehicle-Slab Track-Subgrade System considering Fluid-Solid Interaction

2019 ◽  
Vol 2019 ◽  
pp. 1-14 ◽  
Author(s):  
Kai-Wen Liu ◽  
Fei Yue ◽  
Qian Su ◽  
Bao Liu ◽  
Pengfei Zhou
Keyword(s):  
Surface Layer ◽  
High Speed ◽  
Pore Water Pressure ◽  
Water Pressure ◽  
Critical Length ◽  
Bottom Layer ◽  
Dynamic Responses ◽  
Continuous Contact ◽  
Slab Track ◽  
Fluid Solid Interaction

The excessive pumping of fines in saturated roadbed surface layer, which is induced by the fluid-solid interaction under dynamic loads from high-speed train, is a special form of high-speed railway subgrade defect reported recently. This can deteriorate the interface between nonballasted track structure bottom layer and roadbed surface layer and therefore lead to associated contact variation with the moving of trains. According to the dynamic Biot’s equations known as u-p formulation and the vehicle-track coupling dynamics theory, a vertical vehicle-slab track-subgrade coupling vibration model is developed to investigate the aforementioned contact variation-induced dynamic behavior of the whole system considering the fluid-solid interaction. Dynamic measurements from a field case study are adopted to verify the computation model proposed. Based on the numerical model validated, the effects of three contact variation statuses (continuous contact, vibrating contact, and contact loss) on dynamic responses of track subsystem and subgrade subsystem, such as dynamic pore-water pressure, vertical accelerations, and dynamic displacements both in time and frequency domains, are investigated. Also, a sensitivity analysis involving rail speeds and lengths of contact loss zone is performed, and the critical length of contact loss zone is suggested.

Numerical Analysis of Safety on Waste-Dumping Cover-Slope out of the Tailings Dam

2014 ◽  
Vol 501-504 ◽  
pp. 178-184
Author(s):  
Kai Yang ◽  
Shu Ran Lv ◽  
Chun Xue Wang
Keyword(s):  
Production Cost ◽  
Pore Water Pressure ◽  
Water Pressure ◽  
Bottom Layer ◽  
Tailings Dam ◽  
Waste Dump ◽  
Mining Companies ◽  
Tailings Dams ◽  
Before And After ◽  
Dump Slope

Mining companies intend to solve the problem of waste dump and reduce the production cost by dumping a large number of waste soils to cover slope outside the running tailings. Therefore, in order to discuss the safety of waste dump slope covering in front of the tailings dam, numerical method was adopted to study the seepage-line change law, the pore water pressure and anti-sliding safety before and after the waste dump covering out of tailings dam. The researches show that the key to waste-dump slope safety are the drainage performance of waste dump bottom layer and the anti-sliding safety of waste dump soil. The appropriate waste dump slope work can improves the tailings dams safety and solves the waste dump problem in mining production.

Experimental Study of the Influence of the Pore Water Pressure Evolution and the Shear Band Formation on the Extraction Resistance of Submerged Anchor Plates

2018 ◽  
Author(s):  
Manuela Kanitz ◽  
Juergen Grabe
Keyword(s):  
Experimental Study ◽  
Shear Band ◽  
Pore Water ◽  
High Speed ◽  
Pore Water Pressure ◽  
Water Pressure ◽  
Offshore Structures ◽  
Shear Band Formation ◽  
Band Formation ◽  
Anchor Plates

Floating offshore structures used to generate wind energy are founded on submerged foundations such as anchor plates. Their extraction resistance is of major importance during and at the end of the lifetime cycle of these offshore structures. During their lifetime cycle, the foundation is suspended to complex loading conditions due to waves, tidal currents and wind loads. To guarantee a stable structure, the extraction resistance of the anchor plates has to be known. At the end of the lifetime cycle of the offshore structures, the extraction resistance is mainly influencing the removal of the anchor plates. This resistance is a lot higher than the sum of its self-weight and hydrostatic and earth pressure acting on the structure. With initiation of a motion of the anchor plate, the volume underneath this structure is increased leading to negative pore water pressure until inflowing pore water is filling the newly created volume. In order to investigate this effect, an extensive experimental study at model scale with a displacement-driven extraction is performed. Pore pressure measurements are carried out at various locations in the soil body and underneath the plate. The soil movement is tracked with a high-speed camera to investigate the shear band formation with the particle image velocimetry method (PIV). The experiments will be conducted considering different packing densities of the soil body and at different extraction velocities to investigate their effect on the extraction resistance of anchor plates.

scholarly journals Effect of Improvement and Application of Composite Prefabricated Vertical Drain Method in Marine Soft Ground: A Case Study

2019 ◽  
Vol 2019 ◽  
pp. 1-18 ◽  
Author(s):  
Jianqing Jiang ◽  
Reqiang Liu
Keyword(s):  
High Speed ◽  
Pore Water Pressure ◽  
Water Pressure ◽  
Ground Improvement ◽  
Field Monitoring ◽  
Hyperbolic Model ◽  
Soft Ground ◽  
Prefabricated Vertical Drains ◽  
Prefabricated Vertical Drain

One of the commonly used techniques to improve marine soft ground is the drainage consolidation method by plastic board drains (PBDs). But some complex marine soft ground will cause construction inconvenience of PBDs in certain areas of these sites, thus affecting the improvement effect. An alternative possible approach to overcoming these deficiencies may be the combination of PBDs and sand wick drains (SWDs) (i.e., composite prefabricated vertical drains (CPVDs)) as vertical drainage channels in the same site. In order to verify the suitability and performance of this method in marine soft ground improvement, a case study was performed based on the field monitoring and construction of the marine soft ground of an intercity express railway project in China. The construction procedure using the CPVD system, the field monitoring instrumentation scheme, and the design of fill surcharge level were described, and the field monitoring data were presented. The settlement characteristics, dissipation features of pore water pressure, and the horizontal movement pattern were assessed. In addition, predictions of ultimate settlement, postconstruction settlement, and consolidation degree were discussed by applying a modified hyperbolic model. The results show that the marine ground improved by the CPVD system is suitable for the construction of intercity express railway and high-speed railway. The improvement construction period of complex marine soft ground will be greatly shortened by the proposed parallel construction programme. This work will provide technical supports and application reference for the improvement of the similar marine soft ground.

Influences on Liquefaction-Induced Damage of Pore Water Seepage into an Unsaturated Surface Layer

2020 ◽  
Vol 15 (6) ◽  
pp. 754-764
Author(s):  
Yohsuke Kawamata ◽  
Hiroshi Nakazawa ◽  
◽  
Keyword(s):  
Surface Layer ◽  
Pore Water ◽  
Groundwater Level ◽  
Water Movement ◽  
Pore Water Pressure ◽  
Water Pressure ◽  
Lateral Spreading ◽  
Soil Liquefaction ◽  
Water Seepage ◽  
Long Duration

Various studies have examined soil liquefaction and the resultant structure damage. The 1995 Southern Hyogo Prefecture Earthquake, a near-field earthquake, caused significant damage when the ground was liquified due to the rapidly increased pore water pressure in several cycles of major motions. Therefore, the effect of pore water movement during earthquakes has been assumed to be limited, and liquefaction has mainly been evaluated in undrained conditions. Additionally, the ground and building settlement or inclination caused by liquefaction are deemed to result from pore water drainage after earthquakes. Meanwhile, in the 2011 Tohoku Earthquake, off the Pacific Coast, a subduction-zone earthquake, long-duration motions were observed for over 300 s with frequent aftershocks. Long-duration motions with frequent aftershocks are also anticipated in a future Nankai Trough Earthquake. The effect of pore water movement not only after but during an earthquake should be considered in cases where pore water pressure gradually increases in long-duration motion. The movement of pore water during and after an earthquake typically results in simultaneous dissipation and buildup of water pressure, as well as volumetric changes associated with settlement and lateral spreading. Such effects must reasonably be considered in liquefaction evaluation and building damage prediction. This research focuses on pore water seepage into the unsaturated surface layer caused by the movement of pore water. Seepage experiments were performed based on parameters such as height of test ground, ground surface permeability, and liquefaction duration. In the tests, water pressure when the saturated ground below the groundwater level is fully liquified was applied to the bottom of the specimen representing an unsaturated surface layer. Seepage behaviors into the unsaturated surface layer were then evaluated based on the experiment data. The results show that the water level rises due to pore water seepage from the liquefied ground into the unsaturated surface layer right above the liquefied ground. For this reason, a ground shallower than the original groundwater level can be liquified.

Seismic Analysis of an Earth-Rock Dam on Thick Alluvial Deposit

2012 ◽  
Vol 594-597 ◽  
pp. 1811-1815
Author(s):  
Wei Jun Cen ◽  
Shuai Wang ◽  
Zhi Xiang Yang ◽  
Hui Sun
Keyword(s):  
Seismic Analysis ◽  
Pore Water Pressure ◽  
Limit Equilibrium ◽  
Water Pressure ◽  
Permanent Deformation ◽  
Dynamic Responses ◽  
Seismic Resistance ◽  
Dam Foundation ◽  
Dynamic Displacement ◽  
Alluvial Deposit

The nonlinear dynamic FEM was applied to analyze the dynamic response of a core-wall earth-rock dam on thick loess alluvial deposit. The dynamic responses of acceleration, dynamic displacement, permanent deformation and the liquefaction state of the dam were obtained. Meanwhile, both dynamic FEM limit equilibrium method and pseudo-static method were used to access the seismic resistance of dam slope stability. The results show that dynamic responses of acceleration and dynamic displacement are reasonable. The permanent deformation is mainly concentrated in the core wall. The downstream dam slope has enough seismic resistance stability. However, there will be big dynamic pore-water pressure in the dam foundation and the loess alluvial deposit will be liquefied during the earthquake. Therefore the resistance method of liquefaction should be adopted for the foundation.

Effects of degree of compaction and fines content of the subgrade bottom layer on moisture migration in the substructure of high-speed railways

2017 ◽  
Vol 232 (4) ◽  
pp. 1197-1210 ◽  
Author(s):  
Ren-Peng Chen ◽  
Han-Lin Wang ◽  
Peng-Yun Hong ◽  
Yu-Jun Cui ◽  
Shuai Qi ◽  
...  
Keyword(s):  
Surface Layer ◽  
Water Content ◽  
High Speed ◽  
Bottom Layer ◽  
Volumetric Water Content ◽  
Water Retention Capacity ◽  
Wetting Front ◽  
Moisture Migration ◽  
Double Line ◽  
Fines Content

Moisture migration and distribution in the substructure are found to be the important reasons for water-related problems in high-speed railways. In this study, a numerical model of a double-line ballastless track-bed consisting of a substructure (subgrade surface layer, subgrade bottom layer and subsoil) and a superstructure (including two concrete bases right above the substructure) was established. The superstructure was considered as an impermeable boundary in this model, while two fissures were set at the joint edges of the left-line concrete base and the surface layer, simulating the infiltration area of rainwater. The effects of degree of compaction and fines content of the bottom layer due to moisture migration in the high-speed railway substructure were investigated on this model by applying and analyzing the 2013 rainfall data of Hangzhou, China, for a three-year period. The results show that the saturation zones develop in the subgrade, after a three-year period, with the size increasing with the increase in the degree of compaction or fines content due to higher water retention capacity and lower permeability of the soil. Furthermore, the variations of volumetric water content at different depths of the left-fissure profile indicate that as the degree of compaction or fines content increases, the arriving time of the wetting front increases, but the fluctuation amplitude of the volumetric water content after the arrival of the wetting front decreases on the whole. The degree of compaction appears to present a more significant impact on these two parameters. In particular, a threshold value of the degree of compaction between 0.90 and 0.93 is observed, prolonging the arriving time of the wetting front remarkably at a certain elevation. Besides, it takes a longer time for the wetting front to pass through the interface between the surface layer and the bottom layer for each case. From a practical point of view, it will be beneficial to employ drainage methods to drain out the water before it reaches the bottom layer.

Analysis on Vibrations due to High-Speed Railway Tunnel and Control Measures

2012 ◽  
Vol 226-228 ◽  
pp. 381-386
Author(s):  
Xiao Juan Quan ◽  
Kai Shi ◽  
Yi Bo Yan
Keyword(s):  
Pore Water ◽  
High Speed ◽  
Pore Water Pressure ◽  
Water Pressure ◽  
Vertical Displacement ◽  
Normal Operation ◽  
Shield Tunnel ◽  
Tunnel Structure ◽  
High Speed Railway ◽  
Grouting Reinforcement

With the economy developing rapidly, China has entered the era of high-speed railway, but at the same time, the negative impact of high-speed railway is increasing obviously. The paper analyzes the induced environmental vibration problems due to the high-speed railway, the specific response in the power of the shield tunnel under the train loads, the tunnel structure and the surrounding strata, When the local layer is saturated sand, by calculating the pore water pressure and the layer stress, determining whether it can cause sand liquefaction phenomenon or not, judging the damage extent of tunnel structure, especially it may influences the normal operation of the train. The vertical displacement of the tunnel structure due to the dynamic train load may have impact on the normal operation of the train, where some preventive measures should be taken, such as concrete grouting reinforcement method. In this paper the non-reinforcement case is compared to the reinforcing ones, and different reinforcement ring thickness is studied in order to determine a reasonable thickness of the reinforcement. The main contents include the following work: （1）Response analysis by using the FLAC3D software to simulate the shield tunnel under the dynamic train loads which are the main cause of the displacement of the segment and surrounding strata. The simulation study mainly includes analysis of the changes of pore water pressure and stress. （2） Since train load can produce the vertical displacement, prevention and controlling measures should be taken, which mainly use grouting reinforcement.

Three-Dimensional Dynamic Response Analysis of Shield Tunnel under Train Loads

2011 ◽  
Vol 90-93 ◽  
pp. 2062-2067 ◽  
Author(s):  
Zhan Rui Wu ◽  
Tai Yue Qi ◽  
Lin Zhong
Keyword(s):  
Dynamic Response ◽  
High Speed ◽  
Pore Water Pressure ◽  
Water Pressure ◽  
Three Dimensional ◽  
Shield Tunnel ◽  
Response Analysis ◽  
High Speed Train ◽  
Lining Structure ◽  
Design Speed

The vibration loads will be produced between wheel and rail on the running of the high-speed Train. The vibration energy will be transferred to the ground formation through the rail, guiding bed and tunnel lining structure, thereby causing vibration between the formation and surface and environmental interference effect problems. Thus the research of related issues caused by the high-speed train vibration has the vital great significance. The train design speed of the Shiziyang shield tunnel for Guangzhou-Shenzhen-Hong Kong passenger dedicated line is up to 350km/h. In this paper the research object is located in the segment of the homogeneous formation of the Shiziyang shield tunnel. The analysis of this paper includes the dynamic response rules of the shield tunnel and formation under the single high-speed train loads and the law of the pore water pressure accumulation and dispersion under train cyclic loading.

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