scholarly journals Numerical Study on the Longitudinal Response Characteristics of Utility Tunnel under Strong Earthquake: A Case Study

2020 ◽  
Vol 2020 ◽  
pp. 1-12
Author(s):  
Guoyi Tang ◽  
Yumei Fang ◽  
Yi Zhong ◽  
Jie Yuan ◽  
Bin Ruan ◽  
...  
Keyword(s):  
Seismic Response ◽  
Strong Earthquake ◽  
Numerical Study ◽  
Soft Soil ◽  
Near Field ◽  
Element Model ◽  
Far Field ◽  
Response Characteristics ◽  
Longitudinal Response ◽  
Utility Tunnel

In this paper, the longitudinal seismic response characteristics of utility tunnel subjected to strong earthquake was investigated based on a practical utility tunnel project and numerical method. Firstly, the generalized response displacement method (GRDM) that was used to conduct this study was reviewed briefly. Secondly, the information of the referenced engineering and the finite element model was introduced in detail, where a novel method to model the joints between utility tunnel segments was presented. Thirdly, a series of seismic response of the utility tunnel were provided, including inner force and intersegment opening width. The results showed that (i) the seismic response of the utility tunnel under far-field earthquake may be remarkable and even higher than that under near-field earthquake; (ii) sharp variation of response may occur at the interface between “soft” soil and “hard” soil, and the variation under far-field earthquake could be much more significant. This research provides a reference for the scientific study and design of relevant engineering.

Vibration Propagation Law and Control Test of Ultra Soft Soil Ground under Impact Load

2013 ◽  
Vol 295-298 ◽  
pp. 2030-2033
Author(s):  
Zhang Ming Li ◽  
Wen Xiu Zeng
Keyword(s):  
Impact Load ◽  
Soft Soil ◽  
Near Field ◽  
Far Field ◽  
Horizontal Distance ◽  
Negative Power ◽  
Propagation Law ◽  
Safe Control ◽  
The Impact ◽  
Control Distance

Through in situ tests on the impact vibration of a typical muck ground treatment major project directed by the first author, the vibration propagation law under the impact load for the ultra soft soil ground is obtained, and quantitative environmental safe control distance on the vibration influence is also gained. The main results are the two aspects. (1) The attenuation law of both level and vertical peak vibration acceleration with the horizontal distance can be described well by the negative power function; and the ground vibrations caused by tamping impact can be distinguished between two types, i.e. near-field and far-field. Near-field tamping vibration influence is confined to a small range of the tamping center, which decays obviously faster than the one of far-field. (2) The radius of influence of tamping vibration depends not only on the tamping energy but also the soil type. Loose, slightly dense soft soil has a larger energy absorption capacity and a smaller effect radius of tamping vibration than the dense and hard soil; and the vibration safe control distance is determined as 27.3m in the tests according to the safe boundary determined code of industrial and civil architecture in China.

scholarly journals Shaking Table Test and Numerical Verification for Free Ground Seismic Response of Saturated Soft Soil

2018 ◽  
Vol 2018 ◽  
pp. 1-14
Author(s):  
Xuelei Cheng ◽  
Chunyi Cui ◽  
Zongguang Sun ◽  
Jinhong Xia ◽  
Guangbing Wang
Keyword(s):  
Numerical Simulation ◽  
Seismic Response ◽  
Effective Stress ◽  
Shaking Table Test ◽  
Soft Soil ◽  
Pressure Ratio ◽  
Free Field ◽  
Shaking Table ◽  
Response Characteristics ◽  
Fully Coupled

This paper investigates shaking table test (1g) and numerical simulation (fully coupled) of vertically propagating shear waves for saturated soft free field. A large-scale shaking table model test was performed to study seismic response characteristics of saturated soft soil free field. According to test results of seismic response features of free field system in saturated soft soil, the free field nonlinearity fully coupled numerical model of dynamical effective stress of saturated soft soil was established using OpenSEES, based on the u-p formulations of dynamic consolidation equation as well as effective stress solution method for saturated two-phase media. The numerical simulation of the free field seismic response of saturated soft soil under various test conditions was performed and the calculated results were compared with the shaking table test results. The results show the following. (1) With the increase of input ground motion intensity, the characteristic frequency of the saturated soft free ground decreases and the damping ratio increases gradually. (2) The saturated soft soil ground has short period filtering and long period amplification effect on the horizontal input seismic loads. The failure foundation takes on the isolation and shock absorption under strong ground motions. (3) The peak pore pressure ratio of the saturated soft soil ground is located in the shallow buried soil layer, and with the increase of the input ground motion intensity, the advantage of dynamic pore pressure ratio in this area is gradually weakened. (4) The numerical simulation results are consistent with the results of the shaking table test. This fully coupled effective stress numerical method can reasonably simulate the seismic response characteristics of free field in saturated soft soil, which lay the foundation for other more complex parameter extrapolation models of saturated soft soil sites. This research can provide the necessary technical experience for experimental study on non-free field.

scholarly journals Numerical Study of the Near-Field and Far-Field Properties of Active Open Cylindrical Coated Nanoparticle Antennas

2011 ◽  
Vol 3 (6) ◽  
pp. 1093-1110 ◽  
Author(s):  
Junping Geng ◽  
R. W. Ziolkowski ◽  
Ronghong Jin ◽  
Xianling Liang
Keyword(s):  
Numerical Study ◽  
Near Field ◽  
Far Field ◽  
Coated Nanoparticle

scholarly journals Experimental and numerical study of rotor aeroacoustics

2017 ◽  
Vol 16 (6) ◽  
pp. 460-475 ◽  
Author(s):  
Robert Stepanov ◽  
Vladimir Pakhov ◽  
Andrey Bozhenko ◽  
Andrey Batrakov ◽  
Lyaysan Garipova ◽  
...  
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
High Resolution ◽  
Numerical Study ◽  
Near Field ◽  
Far Field ◽  
Acoustic Data ◽  
Technical University ◽  
Helicopter Acoustics

The work documents recent experiments at the Kazan National Research Technical University named after A.N. Tupolev (Kazan Aviation Institute), related to helicopter acoustics. The objective is to measure nar-field acoustics of rotors in hover and provide data suitable for computational fluid dynamics validation. The obtained set of data corresponds to a scaled rotor of known planform and the results are of high resolution. An advantage of the current dataset is that direct near-field acoustic data is made available and this allows for easy and direct comparisons with computational fluid dynamics predictions, without the need to use far-field aeroacoustic methods.

scholarly journals On the Seismic Response of Protected and Unprotected Middle-Rise Steel Frames in Far-Field and Near-Field Areas

2014 ◽  
Vol 2014 ◽  
pp. 1-11 ◽  
Author(s):  
Dora Foti
Keyword(s):  
Seismic Response ◽  
Ground Motions ◽  
Near Field ◽  
Shaking Table ◽  
Far Field ◽  
Base Shear ◽  
Friction Dampers ◽  
Steel Moment Resisting Frames ◽  
Damage Indices ◽  
Moment Resisting

Several steel moment-resisting framed buildings were seriously damaged during Northridge (1994); Kobe (1995); Kocaeli, Turkey (1999), earthquakes. Indeed, for all these cases, the earthquake source was located under the urban area and most victims were in near-field areas. In fact near-field ground motions show velocity and displacement peaks higher than far-field ones. Therefore, the importance of considering near-field ground motion effects in the seismic design of structures is clear. This study analyzes the seismic response of five-story steel moment-resisting frames subjected to Loma Prieta (1989) earthquake—Gilroy (far-field) register and Santa Cruz (near-field) register. The design of the frames verifies all the resistance and stability Eurocodes’ requirements and the first mode has been determined from previous shaking-table tests. In the frames two diagonal braces are installed in different positions. Therefore, ten cases with different periods are considered. Also, friction dampers are installed in substitution of the braces. The behaviour of the braced models under the far-field and the near-field records is analysed. The responses of the aforementioned frames equipped with friction dampers and subjected to the same ground motions are discussed. The maximum response of the examined model structures with and without passive dampers is analysed in terms of damage indices, acceleration amplification, base shear, and interstory drifts.

DYNAMIC SOIL-PILE-RAFT INTERACTION IN NORMALLY CONSOLIDATED SOFT CLAY DURING EARTHQUAKES

2012 ◽  
Vol 06 (03) ◽  
pp. 1250031 ◽  
Author(s):  
MA KANG ◽  
SUBHADEEP BANERJEE ◽  
FOOK-HOU LEE ◽  
HE PING XIE
Keyword(s):  
Soft Soil ◽  
Near Field ◽  
Soft Clay ◽  
Bending Moment ◽  
Far Field ◽  
Field Soil ◽  
Active Length ◽  
Significant Difference ◽  
The Difference ◽  
Flexible Pile

This paper examines the seismic response of clay pile-raft system with flexible and stiff piles using centrifuge and numerical studies. Centrifuge studies showed that interaction between pile-raft and clay will cause a significant softening in the clay adjacent to the pile-raft which produced a lengthening of resonance period in near-field soil compared to the far-field soil. The difference of response among the raft and the soil at both near- and far-field indicates that ground motion at both near- and far-field cannot be representative of raft motion. There is also significant difference between flexible and stiff pile response. It has been shown in a previous study that, for stiff pile, the soft clay acts as an inertial loading medium rather than a supporting medium. For this reasons, the bending moment diagram extends deep into the soft soil stratum. However, for flexible pile, the supporting effect of the surrounding clay is much more significant than in stiff pile. As a result, the bending moment envelope for flexible pile under earthquake shaking is very similar to the head-loaded test results, with an active length of pile below which no significant bending moment occurs.

Analysis on the Seismic Response of Hangzhou Metro Tunnel in Soft Soils

2012 ◽  
Vol 446-449 ◽  
pp. 966-969
Author(s):  
Guo Cai Wang ◽  
Jun Yao ◽  
Ling Sha ◽  
Lin Chun Yu ◽  
Xu Wei Zheng
Keyword(s):  
Seismic Response ◽  
Seismic Design ◽  
Soft Soil ◽  
Underground Structure ◽  
Response Analysis ◽  
Response Characteristics ◽  
Finite Element Software ◽  
Calculation Results ◽  
Earthquake Load ◽  
Metro Tunnel

A large number of earthquake disasters indicate that the underground structure, such as metro tunnel, is not safe and reliable as people think, and can also be destroyed and collapsed under dynamic load, e.g. earthquake. Therefore, it is necessary to study the seismic response analysis of underground structure in great detail for underground structure under dynamic loading, especially under the earthquake load. Hence, in view of the soft soil of Hangzhou, the 3D non-linear finite element software ADINA is used to study the seismic response of section tunnel of Hangzhou metro line 1, to summarize the earthquake response characteristics of the subway underground structure, and to provide the calculation results of metro tunnel’s seismic response and the change rule of lining deformation and stress. The conclusions obtained can provide some reference values in the seismic design of metro tunnel in soft soil regions.

scholarly journals Numerical Study on the Impact Instability Characteristics Induced by Mine Earthquake and the Support Scheme of Roadway

2021 ◽  
Vol 2021 ◽  
pp. 1-16
Author(s):  
Guang-jian Liu ◽  
Shan-lin Li ◽  
Zong-long Mu ◽  
Wen Chen ◽  
Lei-bo Song ◽  
...  
Keyword(s):  
Rock Mass ◽  
Coal Mine ◽  
Numerical Study ◽  
Steel Strip ◽  
Near Field ◽  
Element Model ◽  
Static Stress ◽  
Impact Failure ◽  
Coal Rock ◽  
The Impact

Rockburst of deep roadway was induced by the superposition of mine earthquake disturbance and high static stress exceeding the limit strength of coal-rock mass. To study the roadway impact instability characteristics caused by mine earthquake disturbance and to propose an optimized support scheme, the discrete element model of the roadway structure was established based on the 1305 working face of the Zhaolou Coal Mine. The influence of mine earthquake amplitude and hypocenter location on the roadway was analyzed. The mesocrack evolution characteristics of the roadway were simulated and reproduced. Characteristics of stress field, crack field, displacement field, and energy field of the disturbed roadway with different support schemes were studied. The results showed that the greater the amplitude of the mine earthquake was, the severer the roadway impact failure was. The upper and left hypocenters had a significant influence on the roadway. The superposition of the high static stress and the dynamic stress due to the far-field mine earthquake resulted in the impact instability of coal-rock mass around the roadway, causing severe roof subsidence as well as rib and bottom heave. The evolution of tensile cracks caused the severe impact failure of roadway from a mesoscopic perspective. Using the flexible support to reinforce the roadway retarded the stress decline in roof and rib, improved the self-stability, reduced the number of near-field cracks, and decreased the displacement. Meanwhile, it allowed the roof and rib deformation, which was conducive to releasing elastic energy in surrounding rocks and reducing mine earthquake energy. The cracks and deformation in the floor were controlled by using the floor bolt. The optimal support scheme for a roadway to resist mine earthquake disturbance was proposed: “bolt-cable-mesh-steel strip-π-beam + floor bolt.” The research results have a specific guiding significance for the support of the coal mine roadway.

scholarly journals Numerical Study on Energy Dissipation of Steel Moment Resisting Frames under Effect of Earthquake Vibrations

2014 ◽  
Vol 2014 ◽  
pp. 1-13 ◽  
Author(s):  
Mohsen Gerami ◽  
Davood Abdollahzadeh
Keyword(s):  
Numerical Study ◽  
Near Field ◽  
Active Faults ◽  
Far Field ◽  
Input Energy ◽  
Rupture Propagation ◽  
Fault Rupture ◽  
Moment Frames ◽  
Fault Rupture Propagation ◽  
Structure Height

In the regions near to active faults, if the fault rupture propagation is towards the site and the shear wave propagation velocity is near the velocity of fault rupture propagation, the forward directivity effect causes pulse-like long-period large-amplitude vibrations perpendicular to the fault plane which causes a large amount of energy to be imposed to structures in a short time. According to previous investigations, the amounts of input and dissipated energies in the structure represent the general performance of the structure and show the level of damage and flexibility of the structure against earthquake. Therefore, in this study, the distribution of damage in the structure height and its amount at the height of steel moment frames under the pulse-like vibrations in the near fault region has been investigated. The results of this study show that the increase rate of earthquake input energy with respect to increase in the number of stories of the structure in the near field of fault is triple that in the far field of fault which then leads to a 2–2.5 times increase in the earthquake input energy in the high rise moment frames in the near field of fault with respect to that in the far field of fault.

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