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

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.

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

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.295-298.2030 ◽

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.

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Numerical Modeling of Soil-Pile-Interaction with Near and Far Field Earthquake's Effects

Civil Engineering Journal ◽

10.28991/cej-2017-00000096 ◽

2017 ◽

Vol 3 (5) ◽

pp. 351-364

Author(s):

Mohammad Shahmohammadi Mehrjerdi ◽

Ahmad Ali Fallah ◽

S.T. Tabatabaei Aghda

Keyword(s):

Yield Surface ◽

Direct Method ◽

Response Spectrum ◽

Near Field ◽

Soft Clay ◽

Structural Response ◽

Time History ◽

Far Field ◽

Plasticity Model ◽

Surface Plasticity

This paper studies Near and Far Field effects of the response of a column-pile to earthquakes considering Dynamic-Soil-Structure-Interaction (DSSI) effects in soft clay (Vs<180 m/s ) and stiff clay (180<Vs<375 m/s). Opensees software that can simulate the dynamic time history analysis is used. Both kinematic and inertial interactions are considered and Finite Element Method (FEM) is used to solve DSSI. The direct method applies to 3D modeling of the layered soil and column-pile. A Pressure Independ Multi Yield Surface Plasticity Model is used to simulate different kinds of clay behavior. Time history seismic analyses provide for the mass and stiffness matrices to evaluate dynamic structural response with and without directivity effects for Near and Far Field earthquakes. Results show that the Multi-Yield-Surface-Kinematic-Plasticity-Model can be used instead of bilinear springs between piles and clay soil, for both Near Field and Far Field earthquakes. In addition, comparing Near and Far Field analyses, acceleration response spectrum at the top of the structure in the Far Field increases with the softness of the soil more than that in the Near field.

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

Advances in Civil Engineering ◽

10.1155/2020/8813303 ◽

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.

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Sensitivity of InSAR and teleseismic observations to earthquake rupture segmentation

Geophysical Journal International ◽

10.1093/gji/ggaa351 ◽

2020 ◽

Vol 223 (2) ◽

pp. 875-907 ◽

Cited By ~ 1

Author(s):

Andreas Steinberg ◽

Henriette Sudhaus ◽

Sebastian Heimann ◽

Frank Krüger

Keyword(s):

Robust Estimation ◽

Field Data ◽

Near Field ◽

Point Sources ◽

Data Sets ◽

Systematic Bias ◽

Far Field ◽

Single Source ◽

Significant Difference ◽

Source Mechanisms

SUMMARY Earthquakes often rupture across more than one fault segment. If such rupture segmentation occurs on a significant scale, a simple point-source or one-fault model may not represent the rupture process well. As a consequence earthquake characteristics inferred, based on one-source assumptions, may become systematically wrong. This might have effects on follow-up analyses, for example regional stress field inversions and seismic hazard assessments. While rupture segmentation is evident for most Mw > 7 earthquakes, also smaller ones with 5.5 < Mw < 7 can be segmented. We investigate the sensitivity of globally available data sets to rupture segmentation and their resolution to reliably estimate the mechanisms in presence of segmentation. We focus on the sensitivity of InSAR (Interferometric Synthetic Aperture Radar) data in the static near-field and seismic waveforms in the far-field of the rupture and carry out non-linear and Bayesian optimizations of single-source and two-sources kinematic models (double-couple point sources and finite, rectangular sources) using InSAR and teleseismic waveforms separately. Our case studies comprises of four Mw 6–7 earthquakes: the 2009 L’Aquila and 2016 Amatrice (Italy) and the 2005 and 2008 Zhongba (Tibet) earthquakes. We contrast the data misfits of different source complexity by using the Akaike informational criterion (AIC). We find that the AIC method is well suited for data-driven inferences on significant rupture segmentation for the given data sets. This is based on our observation that an AIC-stated significant improvement of data fit for two-segment models over one-segment models correlates with significantly different mechanisms of the two source segments and their average compared to the single-segment mechanism. We attribute these modelled differences to a sufficient sensitivity of the data to resolve rupture segmentation. Our results show that near-field data are generally more sensitive to rupture segmentation of shallow earthquakes than far-field data but that also teleseismic data can resolve rupture segmentation in the studied magnitude range. We further conclude that a significant difference in the modelled source mechanisms for different segmentations shows that an appropriate choice of model segmentation matters for a robust estimation of source mechanisms. It reduces systematic biases and trade-off and thereby improves the knowledge on the rupture. Our study presents a strategy and method to detect significant rupture segmentation such that an appropriate model complexity can be used in the source mechanism inference. A similar, systematic investigation of earthquakes in the range of Mw 5.5–7 could provide important hazard-relevant statistics on rupture segmentation. In these cases single-source models introduce a systematic bias. Consideration of rupture segmentation therefore matters for a robust estimation of source mechanisms of the studied earthquakes.

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Analysis on Deep Excavation in Soft Soil Located on Sloped Bedrock

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.170-173.13 ◽

2012 ◽

Vol 170-173 ◽

pp. 13-19

Author(s):

Shong Loong Chen ◽

Cheng Tao Ho

Keyword(s):

Lateral Displacement ◽

Retaining Wall ◽

Soft Soil ◽

Soft Clay ◽

Observation Data ◽

Clay Layer ◽

Deep Excavation ◽

Element Analysis ◽

2D Strain ◽

Significant Difference

Deep excavations in soft-clay layer on sloped bedrock often leads to lateral displacement on retaining structures and uneven settlement due to unbalanced pressure generated from excavation. A construction project for which an excavation was complete in soft clay layer on sloped bedrock in Taipei City was adopted in the study. It is learned from the observation logs of the studied case that a significant difference exists in the lateral displacement of diaphragm wall and settlement between up and down-slope sides of sloped bedrock. Deep excavation is in fact profoundly complicated interaction between excavation strutting and soil. In general practice, the design of excavation is frequently simplified as a 2D strain behavior. However, the actual excavation on sloped bedrock is quite different from 1D or 2D simulation in a symmetric manner. Therefore, 2D finite element analysis program, PLAXIS, is introduced for the analysis on the behaviors of soil clay layer on sloped bedrock in excavation. The result is compared with onsite observation data, including displacement of retaining wall, settlement, axial loads of struts and others. The result of retaining wall displacement analysis is found consistent with the trend derived from onsite observation, which is possible for reference of similar engineering analyses and designs in the future.

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Estimation of Peak Acceleration and Bending Moment for Pile-Raft Systems Embedded in Soft Clay Subjected to Far-Field Seismic Excitation

Journal of Geotechnical and Geoenvironmental Engineering ◽

10.1061/(asce)gt.1943-5606.0001779 ◽

2017 ◽

Vol 143 (11) ◽

pp. 04017082 ◽

Cited By ~ 8

Author(s):

Siang Huat Goh ◽

Lei Zhang

Keyword(s):

Soft Clay ◽

Bending Moment ◽

Seismic Excitation ◽

Far Field ◽

Peak Acceleration

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Seismic Response of Container Crane under Near-Field and Far-Field Ground Motions

Applied Sciences ◽

10.3390/app11041740 ◽

2021 ◽

Vol 11 (4) ◽

pp. 1740

Author(s):

Van Bac Nguyen ◽

Jungwon Huh ◽

Bismark Kofi Meisuh ◽

Jongwoo Kim ◽

Inn-Joon Park

Keyword(s):

Seismic Response ◽

Shaking Table Test ◽

Ground Motions ◽

Near Field ◽

Bending Moment ◽

Shaking Table ◽

Far Field ◽

Container Crane ◽

National University ◽

Geometric Length

In this study, the seismic response of a container crane under near-field and far-field ground motions was investigated using a shaking table test on a 1/20 scale crane. The 1/20 scale crane was designed and fabricated based on the similitude laws, in which three independent quantities: geometric length, acceleration, and elastic modulus, were used to design the 1/20 scale crane. A series of shaking table tests were conducted at the Seismic Research and Test Center, Pusan National University, Yangsan Campus to evaluate the seismic response of the scale crane under near-field and far-field ground motions. The results show that the near-field ground motions can cause larger internal forces (that is, axial force and two bending moments) in the landside and seaside legs and larger portal drift than the far-field ground motions. The portal drift of the container crane subjected to the near-field ground motions was 43% higher than that of the container crane subjected to the far-field ground motions. Furthermore, when subjected to the near-field ground motion, the bending moment in the crane’s portal leg was 37% higher than the bending moment when the crane was subjected to the far-field ground motions.

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Cranial crassicaudiasis in two coastal dolphin species from South Africa is predominantly a disease of immature individuals

Diseases of Aquatic Organisms ◽

10.3354/dao03468 ◽

2020 ◽

Vol 139 ◽

pp. 93-102 ◽

Cited By ~ 3

Author(s):

MF Van Bressem ◽

P Duignan ◽

JA Raga ◽

K Van Waerebeek ◽

N Fraijia-Fernández ◽

...

Keyword(s):

South Africa ◽

Bone Development ◽

Bottlenose Dolphins ◽

Fatal Outcome ◽

Population Level ◽

Cape Coast ◽

Osteolytic Lesions ◽

Immune Mediated ◽

Significant Difference ◽

The Difference

Crassicauda spp. (Nematoda) infest the cranial sinuses of several odontocetes, causing diagnostic trabecular osteolytic lesions. We examined skulls of 77 Indian Ocean humpback dolphins Sousa plumbea and 69 Indo-Pacific bottlenose dolphins Tursiops aduncus, caught in bather-protecting nets off KwaZulu-Natal (KZN) from 1970-2017, and skulls of 6 S. plumbea stranded along the southern Cape coast in South Africa from 1963-2002. Prevalence of cranial crassicaudiasis was evaluated according to sex and cranial maturity. Overall, prevalence in S. plumbea and T. aduncus taken off KZN was 13 and 31.9%, respectively. Parasitosis variably affected 1 or more cranial bones (frontal, pterygoid, maxillary and sphenoid). No significant difference was found by gender for either species, allowing sexes to be pooled. However, there was a significant difference in lesion prevalence by age, with immature T. aduncus 4.6 times more likely affected than adults, while for S. plumbea, the difference was 6.5-fold. As severe osteolytic lesions are unlikely to heal without trace, we propose that infection is more likely to have a fatal outcome for immature dolphins, possibly because of incomplete bone development, lower immune competence in clearing parasites or an over-exuberant inflammatory response in concert with parasitic enzymatic erosion. Cranial osteolysis was not observed in mature males (18 S. plumbea, 21 T. aduncus), suggesting potential cohort-linked immune-mediated resistance to infestation. Crassicauda spp. may play a role in the natural mortality of S. plumbea and T. aduncus, but the pathogenesis and population level impact remain unknown.

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