scholarly journals Centrifuge Testing of Model Levees atop Peat: Experimental Data

2016 ◽  
Vol 32 (3) ◽  
pp. 1903-1924 ◽  
Author(s):  
Anne Lemnitzer ◽  
Riccardo Cappa ◽  
Samuel Yniesta ◽  
Scott Brandenberg
Keyword(s):  
Pore Pressure ◽  
Large Scale ◽  
Ground Motions ◽  
Pressure Sensors ◽  
Cyclic Behavior ◽  
Excess Pore Pressure ◽  
Data Repository ◽  
Centrifuge Testing ◽  
Centrifuge Tests ◽  
Seismic Deformation

Four large-scale centrifuge tests were performed at the NEES@UCDavis equipment site to study the cyclic behavior of levee structures resting atop soft organic peat. The model configurations using a non-liquefiable levee focused on the seismic deformation potential of peat during primary consolidation and secondary compression. The tests performed with a sandy levee studied the liquefaction potential of saturated loose sand fill overlying soft peat as well as the levee-peat-interaction under different loading conditions. The models were subjected to scaled ground motions representative of the Sacramento/San Joaquin Delta. System instrumentation consisted of linear potentiometers, pore pressure sensors and accelerometers. Slow data recorded at 1 Hz document the settlements during spin up, application of ground motions, and spin down. Fast data sampled at 4,167 Hz measured the dynamic response of the system, the excess pore pressure increase and immediate settlements. The project is archived at the NEES data repository under nees.org/warehouse/project/1161 .

scholarly journals Sustainable Measures for Protection of Structures Against Earthquake Induced Liquefaction

2021 ◽  
Author(s):  
Gopal S. P. Madabhushi ◽  
Samy Garcia-Torres
Keyword(s):  
Soil Liquefaction ◽  
Excess Pore Pressure ◽  
Economic Losses ◽  
Element Analysis ◽  
Centrifuge Testing ◽  
Centrifuge Tests ◽  
Liquefiable Soil ◽  
Recent Earthquakes ◽  
Excess Pore Pressures ◽  
Excess Pore

AbstractSoil liquefaction can cause excessive damage to structures as witnessed in many recent earthquakes. The damage to small/medium-sized buildings can lead to excessive death toll and economic losses due to the sheer number of such buildings. Economic and sustainable methods to mitigate liquefaction damage to such buildings are therefore required. In this paper, the use of rubble brick as a material to construct earthquake drains is proposed. The efficacy of these drains to mitigate liquefaction effects was investigated, for the first time to include the effects of the foundations of a structure by using dynamic centrifuge testing. It will be shown that performance of the foundation in terms of its settlement was improved by the rubble brick drains by directly comparing them to the foundation on unimproved, liquefiable ground. The dynamic response in terms of horizontal accelerations and rotations will be compared. The dynamic centrifuge tests also yielded valuable information with regard to the excess pore pressure variation below the foundations both spatially and temporally. Differences of excess pore pressures between the improved and unimproved ground will be compared. Finally, a simplified 3D finite element analysis will be introduced that will be shown to satisfactorily capture the settlement characteristics of the foundation located on liquefiable soil with earthquake drains.

A numerical investigation of excess pore pressures and continental slope stability in response to ice-sheet dynamics

2019 ◽  
Vol 500 (1) ◽  
pp. 255-266 ◽  
Author(s):  
Morelia Urlaub ◽  
Isabel Kratzke ◽  
Berit Oline Hjelstuen
Keyword(s):  
Pore Pressure ◽  
Continental Slope ◽  
Large Scale ◽  
Ice Sheets ◽  
Ice Sheet ◽  
Excess Pore Pressure ◽  
Submarine Landslides ◽  
Pore Pressures ◽  
Ice Sheet Dynamics ◽  
Excess Pore

AbstractSubmarine landslides are common at glaciated continental margins. The onset of large-scale landslides coincides with the initiation of Northern Hemisphere glaciations in the Quaternary. This implies that processes related to glacial cycling provide favourable conditions for submarine landslides at high-latitude margins. Potential processes include glacial deposition patterns and enhanced seismicity. It is also possible that advances and retreats of ice sheets, a highly dynamic process in geological terms, makes slopes discernible to failure by modifying the stress regime. Here, we quantify this effect using 2D finite element modelling of a glaciated continental margin. Different model runs investigate the pore-pressure development in homogeneous, as well as layered, slopes during glaciation when loaded by an ice stream with one or more ice advances. Ice streams cause significant variations in excess pore pressure in the very shallow sediment sequences at the continental shelf. However, lateral fluid flow is not efficient enough to increase pore pressures significantly at the slope, where large-scale submarine slides are observed. Hence, while ice-sheet dynamics appear to favour the occurrence of shallow slides close to the shelf edge, ice sheets seem to be irrelevant for the generation of large-scale submarine landslides at the continental slope.

Excess Pore Pressures Around Underground Structures Following Earthquake Induced Liquefaction

2012 ◽  
Vol 3 (2) ◽  
pp. 25-41 ◽  
Author(s):  
Siau Chen Chian ◽  
Santana Phani Gopal Madabhushi
Keyword(s):  
Pore Pressure ◽  
Underground Structure ◽  
Unit Weight ◽  
Excess Pore Pressure ◽  
Earthquake Loading ◽  
Underground Structures ◽  
Floating Structure ◽  
Centrifuge Tests ◽  
Liquefiable Soil ◽  
Excess Pore

Underground structures located in liquefiable soil deposits are susceptible to floatation following an earthquake event due to their lower unit weight relative to the surrounding saturated soil. This inherent buoyancy may cause lightweight structures to float when the soil liquefies. Centrifuge tests have been carried out to study the excess pore pressure generation and dissipation in liquefiable soils. In these tests, near full liquefaction conditions were attained within a few cycles of the earthquake loading. In the case of high hydraulic conductivity sands, significant dissipation could take place even during the earthquake loading which inhibits full liquefaction from occurring. In the case of excess pore pressure generation and dissipation around a floating structure, the cyclic response of the structure may lead to the reduction in excess pore pressure near the face of the structure as compared to the far field. This reduction in excess pore pressure is due to shear-induced dilation and suction pressures arising from extensile stresses at the soil-structure interface. Given the lower excess pore pressure around the structure; the soil around the structure retains a portion of this shear strength which in turn can discourage significant uplift of the underground structure.

Ground Motion Intensity Measures to Evaluate I: The Liquefaction Hazard in the Vicinity of Shallow-Founded Structures

2017 ◽  
Vol 33 (1) ◽  
pp. 241-276 ◽  
Author(s):  
Shideh Dashti ◽  
Zana Karimi
Keyword(s):  
Pore Pressure ◽  
Ground Motions ◽  
Pressure Ratio ◽  
Soil Surface ◽  
Excess Pore Pressure ◽  
Far Field ◽  
Ground Acceleration ◽  
Intensity Measures ◽  
Liquefaction Hazard ◽  
Simplified Procedures

When evaluating the liquefaction hazard within a performance-based framework, whether using simplified procedures or advanced numerical tools, the hazard and its effects on structures need to be evaluated under a range of ground motions. Choice of an optimum intensity measure (IM) in the selection and scaling of ground motions will reduce variability in the predicted response, dependence on source characteristics, and uncertainty in the prediction of the IM. This paper presents the results of a numerical parametric study, validated against centrifuge results, to evaluate the influence of different IMs on the liquefaction hazard in the far-field and near shallow-founded structures. Pore pressure redistribution and soil-structure interaction were considered in estimating the liquefaction hazard in terms of peak excess pore pressure ratio ( r u,peak). The IMs at the base rock, far-field soil surface, and foundation with the best combination of efficiency, sufficiency, and predictability were evaluated and identified as: (1) pseudo-spectral acceleration at the site's initial fundamental period ( PSA Base[ T So]) for predicting r u,peak in the far-field; (2) peak ground acceleration, ( PGA Base); and Arias intensity ( AI Base) for predicting r u,peak under the foundation.

scholarly journals Solid-Fluid Coupled Numerical Analysis of Suction Caisson Installation in Sand

2021 ◽  
Vol 9 (7) ◽  
pp. 704
Author(s):  
He Wang ◽  
Rui Wang ◽  
Jian-Min Zhang
Keyword(s):  
Pore Pressure ◽  
Excess Pore Pressure ◽  
Arbitrary Lagrangian Eulerian ◽  
Seepage Field ◽  
Suction Caisson ◽  
Model Soil ◽  
Centrifuge Tests ◽  
Offshore Engineering ◽  
The Difference ◽  
Excess Pore

Suction caissons are widely used foundations in offshore engineering. The change in excess pore pressure and seepage field caused by penetration and suction significantly affects the soil resistance around the caisson wall and tip, and also affects the deformation of the soil within and adjacent to the caisson. This study uses Arbitrary Lagrangian–Eulerian (ALE) large deformation solid-fluid coupled FEM to investigate the changes in suction pressure and the seepage field during the process of the suction caisson installation in sand. A nonlinear Drucker-Prager model is used to model soil, while Coulomb friction is applied at the soil-caisson interface. The ALE solid-fluid coupled FEM is shown to be able to successfully simulate both jacked penetration and suction penetration caisson installation processes in sand observed in centrifuge tests. The difference in penetration resistance for jacked and suction installation is found to be caused by the seepage and excess pore pressure generated during the suction caisson installation, highlighting the importance of using solid-fluid coupled effective stress-based analysis to consider seepage in the evaluation of suction caisson penetration.

Inclined Perimeter Drains Performance as Liquefaction Countermeasure Techniques Below Existing Buildings

2020 ◽  
Vol 14 (03) ◽  
pp. 2050015
Author(s):  
Samy Garcıáa-Torres ◽  
Gopal Santana Phani Madabhushi
Keyword(s):  
Pore Pressure ◽  
Structural Damage ◽  
Excess Pore Pressure ◽  
Existing Buildings ◽  
Ground Shaking ◽  
Vertical Drains ◽  
Centrifuge Tests ◽  
Pore Pressures ◽  
Excess Pore Pressures ◽  
Excess Pore

Reducing the risk of structural damage due to earthquake-induced liquefaction in new and existing buildings is a challenging problem in geotechnical engineering. Drainage countermeasure techniques against liquefaction have been studied over the last decades with an emphasis on the use of vertical drains. This technique aims to allow a rapid dissipation of excess pore pressures generated in the soil during the earthquake thereby limiting the peak excess pore pressures and consequently improve the structural response. Rapid drainage in the post-earthquake period in the presence of these drains helps quick recovery of the soil strength. Recent studies propose different variations in the vertical drains arrangement to improve the excess pore pressure redistribution in the soil around structures. However, conventional arrangements for existing buildings do not achieve an adequate proximity from the drains to the soil below the foundation. To address this, the performance of inclined and vertical perimeter drain arrangements are studied in this paper. Dynamic centrifuge tests were carried out for the different arrangements in order to evaluate the excess pore pressure generation due to ground shaking and the following dissipation together with the foundation settlement and dynamic response.

Vibro-Stone Column Reinforcement Mechanism and Numerical Analysis

2012 ◽  
Vol 446-449 ◽  
pp. 1940-1943
Author(s):  
Yang Liu ◽  
Hong Xiang Yan
Keyword(s):  
Numerical Simulation ◽  
Numerical Analysis ◽  
Pore Pressure ◽  
Numerical Procedure ◽  
Numerical Results ◽  
Excess Pore Pressure ◽  
Stone Column ◽  
Reinforcement Mechanism ◽  
Consolidation Theory ◽  
Excess Pore

Numerical simulation of vibro-stone column is taken to simulate the installation of vibro-stone column. A relationship based on test is adopted to calculate the excess pore pressure induced by vibratory energy during the installation of vibro-stone column. A numerical procedure is developed based on the formula and Terzaghi-Renduric consolidation theory. Finally numerical results of composite stone column are compared single stone column.

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