scholarly journals Shaking Table Test of Seismic Response of Immersed Tunnels under the Influence of Multiple Factors

2020 ◽  
Vol 2020 ◽  
pp. 1-17
Author(s):  
Zhiyong Ouyang ◽  
Jie Cui ◽  
Ruofan Luo ◽  
Peijie Li
Keyword(s):  
Seismic Response ◽  
Influencing Factors ◽  
Seismic Wave ◽  
Structural Damage ◽  
Soil Layer ◽  
Shaking Table ◽  
Site Conditions ◽  
Peak Strain ◽  
Structural Stiffness ◽  
Soil Layers

To explore the dynamic characteristics and influencing factors of immersed tunnels under the action of earthquakes, 5 groups of shaking table model tests were carried out. Three different site conditions (unsaturated sand site, homogeneous saturated sand site, and nonuniform site), structural stiffness, and seismic wave input direction were considered. By comparing the above influencing factors, the seismic response law affecting the immersed tunnels was obtained. The test results show that, under the action of horizontal earthquakes, the liquefaction of sand and the larger tunnel stiffness may influence the acceleration development of the soil layers; seismic wave input directions affect the excellent frequency and frequency range of the soil layers, and the liquefaction of sand and large structural stiffness change the shape of the Fourier spectrum curve of the soil layers; site conditions, structural stiffness, and seismic wave input direction have a significant effect on the internal forces of tunnels. Normally, the strain in the heterogeneous soil layer under the horizontal seismic wave input is the largest, and the peak strain of the upper side of the tunnel side wall and center column is larger than the lower part, while the mechanism of structural damage caused by vertical earthquakes is different.

scholarly journals Shaking Table Tests for Seismic Response of Orthogonal Overlapped Tunnel under Horizontal Seismic Loading

2021 ◽  
Vol 2021 ◽  
pp. 1-19
Author(s):  
Honggang Wu ◽  
Hao Lei ◽  
Tianwen Lai
Keyword(s):  
Dynamic Response ◽  
Seismic Response ◽  
Seismic Wave ◽  
Shaking Table Test ◽  
Shaking Table ◽  
Shaking Table Tests ◽  
Acceleration Response ◽  
Test Device ◽  
Deformation Stages ◽  
Superposition Effect

This paper presents the seismic dynamic response and spectrum characteristics of an orthogonal overlapped tunnel by shaking table tests. First, a prototype of the engineering and shaking table test device, which was used to design details of the experiment, was developed. Then, the sensors used in the test were selected, and the measurement points were arranged. Subsequently, the Wenchuan seismic wave with horizontal direction in different peak ground accelerations was inputted into the model, followed by a short analysis of the seismic response of the overlapped tunnel in the shaking table test as well as the distribution of the peak acceleration. Throughout the studies, the model exhibited obvious deformation stages during the seismic wave loading process, which can be divided into elastic, plastic, plastic enhancement, and failure stage. In particular, the time- and frequency-domain characteristics of the key parts of the tunnel were discussed in detail by using the continuous wavelet transform (CWT) based on the Morlet wavelet as the basis function. We found that the acceleration response was more intense within 25–60 s after the seismic wave was inputted. Furthermore, owing to “the superposition effect,” the seismic response at the crown of the under-crossing tunnel was stronger than that at the invert of the upper-span tunnel. The low and medium frequencies in the transformation of small scales (5–20) significantly affected the overlapped tunnel. These results elucidate the seismic dynamic response of the overlapped tunnel and provide guidance for the design of stabilizing structures for reinforcing tunnels against earthquakes.

scholarly journals Shaking Table Tests and Numerical Analysis on the Seismic Response of Karst-Crossing Socketed Piles in Dry Sandy Soil Foundation

2020 ◽  
Vol 15 (5) ◽  
pp. 701-709
Author(s):  
Peisen Wang ◽  
Hongyan Ding ◽  
Puyang Zhang
Keyword(s):  
Numerical Analysis ◽  
Seismic Response ◽  
Strain Distribution ◽  
Shaking Table ◽  
Karst Cave ◽  
Peak Strain ◽  
Shaking Table Tests ◽  
Karst Areas ◽  
Foundation Pile ◽  
Friction Pile

The foundation piles in karst areas have different mechanical properties from those in other areas. Targeting a critical highway bridge in a karst area, this paper designs two kinds of foundation pile models: friction pile, and KCSP, based on theories on dynamic tests. Then, shaking table tests were carried out to ascertain the features of pile strain distribution of KCSP under earthquakes. During the tests, a large laminar suspended shear box was adopted to mimic the boundary effect of soil. In addition, numerical simulations were conducted to disclose the effects of karst cave on pile strain. The test results indicate that: the peak strain of KCSP increased with the peak acceleration; For both KCSP and friction pile, the peak strain decreased first and then increased along the depth; The presence of karst cave can adversely affect the seismic response of foundation pile; The taller the karst cave, the larger the peak strain of the pile; the peak strain of KCSP was larger at the two ends, and smaller in the middle. The numerical analysis shows that: the peak strain of foundation pile in karst cave increased significantly with cave height; The peak strain of the pile passing through multiple caves was similar to that of the pile passing through only one cave, under the same cave height; But the multi-cave scenario differed from the single-cave scenario in peak strain distribution. The research results provide new insights into the seismic design of pile foundation of bridges in karst areas.

scholarly journals Study on the Seismic Effect of the Interbedded Soil Layer in the Yinchuan Alluvial Plain

2021 ◽  
Vol 2021 ◽  
pp. 1-12
Author(s):  
Shun Yang ◽  
Xin Han ◽  
Qiyun Lei ◽  
Sihan Yu ◽  
Chao Liu
Keyword(s):  
Seismic Response ◽  
Soil Layer ◽  
Peak Ground Velocity ◽  
Equivalent Linearization ◽  
Silty Clay ◽  
Spectral Acceleration ◽  
Ground Acceleration ◽  
Soil Layers ◽  
Amplification Effect ◽  
Soil Model

This paper presents a numerical analysis of two types of representative site profiles in the Yinchuan Plain under earthquake loading. The analyzed soil profiles, based on borehole investigations performed over the years, are used to explore the seismic response of the sites in this area. In total, eleven stratified soil models are used in this study, which can be grouped into two categories: a single interbedded soil model and multiple interbedded soil model. A one-dimensional equivalent linearization method is applied to evaluate the seismic response of different soil models under four exceeding probabilities in terms of peak ground acceleration (PGA), peak ground velocity (PGV), peak ground displacement (PGD), and spectral acceleration (Sa). The results show that the significant amplification effect of PGA occurs in rare and extremely rare earthquakes, with an amplification ratio of 1.4∼1.7 when the single silty clay layer is located at the model ground. In this scenario, the spectral acceleration is amplified at a period of approximately 1.0 s. For the multilayered soil cases, the amplification effect tends to decrease, whereas the characteristic periods increase with increasing numbers of soil layers and the ground acceleration is deamplified under a high motion intensity when the number of soil layers is ≥ 5. This study, to a certain degree, has reference value for seismic microzonation in this area.

Floating Roof Influence on Seismic Response of Large Vertical Storage Tank

2013 ◽  
Vol 671-674 ◽  
pp. 1399-1402
Author(s):  
Ying Sun ◽  
Jian Gang Sun ◽  
Li Fu Cui
Keyword(s):  
Seismic Response ◽  
Storage Tank ◽  
Numerical Solutions ◽  
Fluid Pressure ◽  
Seismic Intensity ◽  
Site Conditions ◽  
Storage Tanks ◽  
Analysis Model ◽  
Base Shear ◽  
The Impact

To study the impact of floating roof on seismic response of vertical storage tank structure system subjected to seismic excitation, select 150000m3 storage tanks as research object, and the finite element analysis model of storage tanks with and without floating roof were established respectively. The seismic response of these two types of structure in different site conditions and seismic intensity were calculated and the numerical solutions were compared. The results show that floating roof has little impact on base shear and base moment in different site conditions and seismic intensity. Floating roof can effectively reduce the sloshing wave height. The influence of floating roof on dynamic fluid pressure decreases with the increase of seismic intensity, which is less affected by ground conditions.

scholarly journals Variations of deep soil moisture under different vegetation types and influencing factors in a watershed of the Loess Plateau, China

2016 ◽  
Vol 20 (8) ◽  
pp. 3309-3323 ◽  
Author(s):  
Xuening Fang ◽  
Wenwu Zhao ◽  
Lixin Wang ◽  
Qiang Feng ◽  
Jingyi Ding ◽  
...  
Keyword(s):  
Soil Moisture ◽  
Influencing Factors ◽  
Loess Plateau ◽  
Vegetation Restoration ◽  
Native Vegetation ◽  
Watershed Scale ◽  
Vegetation Types ◽  
Deep Soil ◽  
Soil Layers ◽  
Management Measures

Abstract. Soil moisture in deep soil layers is a relatively stable water resource for vegetation growth in the semi-arid Loess Plateau of China. Characterizing the variations in deep soil moisture and its influencing factors at a moderate watershed scale is important to ensure the sustainability of vegetation restoration efforts. In this study, we focus on analyzing the variations and factors that influence the deep soil moisture (DSM) in 80–500 cm soil layers based on a soil moisture survey of the Ansai watershed in Yan'an in Shanxi Province. Our results can be divided into four main findings. (1) At the watershed scale, higher variations in the DSM occurred at 120–140 and 480–500 cm in the vertical direction. At the comparable depths, the variation in the DSM under native vegetation was much lower than that in human-managed vegetation and introduced vegetation. (2) The DSM in native vegetation and human-managed vegetation was significantly higher than that in introduced vegetation, and different degrees of soil desiccation occurred under all the introduced vegetation types. Caragana korshinskii and black locust caused the most serious desiccation. (3) Taking the DSM conditions of native vegetation as a reference, the DSM in this watershed could be divided into three layers: (i) a rainfall transpiration layer (80–220 cm); (ii) a transition layer (220–400 cm); and (iii) a stable layer (400–500 cm). (4) The factors influencing DSM at the watershed scale varied with vegetation types. The main local controls of the DSM variations were the soil particle composition and mean annual rainfall; human agricultural management measures can alter the soil bulk density, which contributes to higher DSM in farmland and apple orchards. The plant growth conditions, planting density, and litter water holding capacity of introduced vegetation showed significant relationships with the DSM. The results of this study are of practical significance for vegetation restoration strategies, especially for the choice of vegetation types, planting zones, and proper human management measures.

Shaking Table Test Study on Mid-Story Isolation Structures

2012 ◽  
Vol 446-449 ◽  
pp. 378-381
Author(s):  
Jian Min Jin ◽  
Ping Tan ◽  
Fu Lin Zhou ◽  
Yu Hong Ma ◽  
Chao Yong Shen
Keyword(s):  
Seismic Response ◽  
Seismic Isolation ◽  
Shaking Table Test ◽  
Base Isolation ◽  
Shaking Table ◽  
Natural Period ◽  
Isolation System ◽  
Isolation Layer ◽  
Lead Rubber Bearing ◽  
Complex Structural

Mid-story isolation structure is developing from base isolation structures. As a complex structural system, the work mechanism of base isolation structure is not entirely appropriate for mid-story isolation structure, and the prolonging of structural natural period may not be able to decrease the seismic response of substructure and superstructure simultaneously. In this paper, for a four-story steel frame model, whose prototype first natural period is about 1s without seismic isolation design, the seismic responses and isolation effectiveness of mid-story isolation system with lead rubber bearing are studied experimentally by changing the location of isolation layer. Respectively, the locations of isolation layer are set at bottom of the first story, top of the first story, top of the second story and top of the third story. The results show that mid-story isolation can reduce seismic response in general, and substructure acceleration may be amplified.

scholarly journals Depth-Dependent C-N-P Stocks and Stoichiometry in Ultisols Resulting from Conversion of Secondary Forests to Plantations and Driving Forces

Forests ◽  
2021 ◽  
Vol 12 (10) ◽  
pp. 1300
Author(s):  
Xiaogang Ding ◽  
Xiaochuan Li ◽  
Ye Qi ◽  
Zhengyong Zhao ◽  
Dongxiao Sun ◽  
...  
Keyword(s):  
Soil Depth ◽  
Soil Layer ◽  
Pinus Elliottii ◽  
Slash Pine ◽  
Pine Plantations ◽  
Secondary Forests ◽  
Masson Pine ◽  
Soil Layers ◽  
Soil C ◽  
Significant Difference

Stocks and stoichiometry of carbon (C), nitrogen (N), and phosphorus (P) in ultisols are not well documented for converted forests. In this study, Ultisols were sampled in 175 plots from one type of secondary forest and four plantations of Masson pine (Pinus massoniana Lamb.), Slash pine (Pinus elliottii Engelm.), Eucalypt (Eucalyptus obliqua L’Hér.), and Litchi (Litchi chinensis Sonn., 1782) in Yunfu, Guangdong province, South China. Five layers of soil were sampled with a distance of 20 cm between two adjacent layers up to a depth of 100 cm. We did not find interactive effects between forest type and soil layer depth on soil organic carbon (SOC), total nitrogen (TN), and total phosphorus (TP) concentrations and storages. Storage of SOC was not different between secondary forests and Eucalypt plantations, but SOC of these two forest types were lower than that in Litchi, Masson pine, and Slash pine plantations. Soil C:P was higher in Slash pine plantations than in secondary forests. Soil CNP showed a decreasing trend with the increase of soil depth. Soil TP did not show any significant difference among soil layers. Soil bulk density had a negative contribution to soil C and P stocks, and longitude and elevation were positive drivers for soil C, N, and P stocks. Overall, Litchi plantations are the only type of plantation that obtained enhanced C storage in 0–100 cm soils and diverse N concentrations among soil layers during the conversion from secondary forests to plantations over ultisols.

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