scholarly journals Performance Assessment of Composite Skirted Ground Reinforcement System in Liquefiable Ground Under Repeated Dynamic Loading Conditions

2021 ◽  
Author(s):  
Vijay Kumar S P ◽  
Ganesh Kumar Shanmugam ◽  
Saurabh Dutta Gupta
Keyword(s):  
Pore Water ◽  
Pore Water Pressure ◽  
Ground Motions ◽  
Water Pressure ◽  
Soil Liquefaction ◽  
Stone Columns ◽  
Loading Conditions ◽  
Reinforcement System ◽  
Soil Densification ◽  
Composite Reinforcement

Abstract Occurrence of earthquake generates both horizontal and vertical ground motions. In saturated sands, combination of generated ground motions and pore water pressures induces soil liquefaction. In this study, a composite skirted ground reinforcement system was developed to mitigate generation of pore water pressure in liquefiable soils and also to attenuate incoming ground motions to the foundation. The composite system contains Poly Urethane foam as an isolation barrier for ground motion attenuation with stone columns for improving both soil densification and drainage. The performance of this composite reinforcement system was evaluated under repeated acceleration loading conditions to estimate its efficiency. For testing, saturated ground model having 40% and 60% relative density was prepared and investigated with and without the composite reinforcement system. Test results showed that, the developed skirted ground reinforcement system effectively mitigates the interaction of incoming ground motions with the foundation and also improves the re-liquefaction resistance of soil compared to that of unreinforced ground.

A Practical Saturated Sand Elastic-Plastic Dynamic Constitutive Model and Application

2012 ◽  
Vol 446-449 ◽  
pp. 1621-1626 ◽  
Author(s):  
Yan Mei Zhang ◽  
Dong Hua Ruan
Keyword(s):  
Constitutive Model ◽  
Pore Water ◽  
Pore Water Pressure ◽  
Water Pressure ◽  
Stone Columns ◽  
Saturated Sand ◽  
Multidimensional Model ◽  
Excess Pore Water Pressure ◽  
Elastic Plastic ◽  
Excess Pore

A practical saturated sand elastic-plastic dynamic constitutive model was developed on the base of Handin-Drnevich class nonlinear lag model and multidimensional model. In this model, during the calculation of loading before soil reaches yielding, unloading and inverse loading, corrected Handin-Drnevich equivalent nonlinear model was adopted; after soil yielding, based on the idea of multidimensional model, the composite hardening law which combines isotropy hardening and follow-up hardening, corrected Mohr-Coulomb yielding criterion and correlation flow principle were adopted. A fully coupled three dimension effective stress dynamic analysis procedure was developed on the base of this model. The seismic response of liquefaction foundation reinforced by stone columns was analyzed by the developed procedure. The research shows that with the diameter of stone columns increasing, the excess pore water pressure in soil between piles decreases; with the spacing of columns increasing, the excess pore water pressure increases. The influence of both is major in middle and lower level of composite foundation.

Prediction of liquefaction potential and pore water pressure beneath machine foundations

2014 ◽  
Vol 4 (3) ◽  
Author(s):  
Mohammed Fattah ◽  
Mohammed Al-Neami ◽  
Nora Jajjawi
Keyword(s):  
Pore Water ◽  
Sandy Soil ◽  
Pore Water Pressure ◽  
Water Pressure ◽  
Soil Liquefaction ◽  
Elastic Model ◽  
Liquefaction Resistance ◽  
Overburden Pressure ◽  
Liquefaction Potential ◽  
Frequency Changes

AbstractThe present research is concerned with predicting liquefaction potential and pore water pressure under the dynamic loading on fully saturated sandy soil using the finite element method by QUAKE/W computer program. As a case study, machine foundations on fully saturated sandy soil in different cases of soil densification (loose, medium and dense sand) are analyzed. Harmonic loading is used in a parametric study to investigate the effect of several parameters including: the amplitude frequency of the dynamic load. The equivalent linear elastic model is adopted to model the soil behaviour and eight node isoparametric elements are used to model the soil. Emphasis was made on zones at which liquefaction takes place, the pore water pressure and vertical displacements develop during liquefaction. The results showed that liquefaction and deformation develop fast with the increase of loading amplitude and frequency. Liquefaction zones increase with the increase of load frequency and amplitude. Tracing the propagation of liquefaction zones, one can notice that, liquefaction occurs first near the loading end and then develops faraway. The soil overburden pressure affects the soil liquefaction resistance at large depths. The liquefaction resistance and time for initial liquefaction increase with increasing depths. When the frequency changes from 5 to 10 rad/sec. (approximately from static to dynamic), the response in displacement and pore water pressure is very pronounced. This can be attributed to inertia effects. Further increase of frequency leads to smaller effect on displacement and pore water pressure. When the frequency is low; 5, 10 and 25 rad/sec., the oscillation of the displacement ends within the period of load application 60 sec., while when ω = 50 rad/sec., oscillation continues after this period.

scholarly journals Soil liquefaction as an identification test

2019 ◽  
Vol 92 ◽  
pp. 08008
Author(s):  
Bozana Bacic ◽  
Ivo Herle
Keyword(s):  
Pore Water ◽  
Laboratory Testing ◽  
Pore Water Pressure ◽  
Water Pressure ◽  
Initial Density ◽  
Soil Liquefaction ◽  
Triaxial Tests ◽  
Cyclic Triaxial ◽  
Cyclic Triaxial Tests ◽  
Identification Test

Time-consuming and complicated investigations of soil liquefaction in cyclic triaxial tests are the most common way of laboratory analysis of this phenomenon. Moreover, the necessary equipment for the performance of cyclic triaxial tests is very expensive. Much simpler method for laboratory testing of the soil liquefaction has been developed at the Institute of Geotechnical Engineering at the TU Dresden. This method takes into account the pore water pressure build-up during cyclic shearing within a short time period. During the test, the soil sample is subjected to horizontal cyclic loading and the generated pore water pressure is measured. In the first series of these experiments, a dependence of the pore water pressure buildup on the initial density of soil could be observed, as expected. When comparing different soils, it is shown that the tendency to liquefaction depends also on the granulometric properties (e.g. grain size distribution) of the soil. The aim of the further development is to establish a simple identification test for laboratory testing of the soil liquefaction.

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.

Earthquake-induced deformation analyses of the Upper San Fernando Dam under the 1971 San Fernando Earthquake

2001 ◽  
Vol 38 (1) ◽  
pp. 1-15 ◽  
Author(s):  
Guoxi Wu
Keyword(s):  
Finite Element ◽  
Pore Water ◽  
Effective Stress ◽  
Pore Water Pressure ◽  
Ground Deformation ◽  
Water Pressure ◽  
Soil Liquefaction ◽  
Shear Stresses ◽  
Cyclic Shear ◽  
San Fernando

A nonlinear effective stress finite element approach for dynamic analysis of soil structure is described in the paper. Major features of this approach include the use of a third parameter in the two-parameter hyperbolic stress-strain model, a modified expression for unloading–reloading modulus in the Martin–Finn–Seed pore-water pressure model, and an additional pore-water pressure model based on cyclic shear stress. The additional pore-water pressure model uses the equivalent number of uniform cyclic shear stresses for the assessment of pore-water pressure. Dynamic analyses were then conducted to simulate the seismically induced soil liquefaction and ground deformation of the Upper San Fernando Dam under the 1971 San Fernando Earthquake. The analyses were conducted using the finite element computer program VERSAT. The computed zones of liquefaction and deformation are compared with the measured response and with results obtained by others.Key words: effective stress method, finite element analysis, Upper San Fernando Dam, earthquake deformation, VERSAT.

Soil Liquefaction Assessment by Anisotropic Cyclic Triaxial Test

2018 ◽  
pp. 631-664
Author(s):  
Koray Ulamis
Keyword(s):  
Pore Water ◽  
Pore Water Pressure ◽  
Axial Strain ◽  
Water Pressure ◽  
Sandy Soils ◽  
Soil Liquefaction ◽  
Cyclic Triaxial ◽  
Loading Case ◽  
Anisotropic Consolidation ◽  
Assessment Standard

Liquefaction of saturated sandy soils is one of the most significant aspects of earthquake triggered natural hazards. The main mechanism deals with the loss of effective stress due to rapid pore water pressure generation during earthquake shaking. This chapter involves with the fundamental mechanism and impacts of liquefaction. Liquefaction susceptibility of geological environments are briefly represented for preliminary assessment. Standard procedures of liquefaction are summarized. The dynamic response of sands are also reviewed. A case of anisotropic loading is considered, using three different particle sized sands below a shallow footing. Such sandy soils are subjected to anisotropic consolidation before performing undrained cyclic triaxial testing along limited cycles. Variation of axial strain, pore water pressure and related parameters are investigated. Main outcome of this study is to review the initial liquefaction state of sands by anisotropic loading case.

Pore-Water Pressure Changes during Soil Liquefaction

1976 ◽  
Vol 102 (4) ◽  
pp. 323-346 ◽  
Author(s):  
H. Bolton Seed ◽  
Philippe P. Martin ◽  
John Lysmer
Keyword(s):  
Pore Water ◽  
Pore Water Pressure ◽  
Water Pressure ◽  
Soil Liquefaction ◽  
Pressure Changes

Determination of the Cyclic Properties of Silty Sands

2018 ◽  
pp. 416-445
Author(s):  
Eyyüb Karakan ◽  
Selim Altun
Keyword(s):  
Cyclic Loading ◽  
Pore Water ◽  
Pore Water Pressure ◽  
Water Pressure ◽  
Triaxial Tests ◽  
Loading Conditions ◽  
Systematic Testing ◽  
Geotechnical Problems ◽  
Insight Into

Liquefaction may be triggered by cyclic loading on saturated silty sands, which is responsible of severe geotechnical problems. Development of excess pore water pressure in soil results in a liquid-like behavior and may be the reason of unavoidable superstructural damage. In this study, in order to investigate the behavior of saturated silty sands exposed to cyclic loading under undrained conditions, a systematic testing program of stress-controlled cyclic triaxial tests was performed on specimens of different silt contents, under different loading conditions and environment. The effect of parameters such as silt content on the liquefaction behavior of specimens was studied. Pore water pressure and shear strain curves were obtained for the silty sands. Furthermore, the boundaries existing in the literature on sands are compared with the results current research, on silty sands. Conclusively, the outcomes of this study were useful to develop insight into the behavior of clean and silty sands under seismic loading conditions.

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