scholarly journals Application of Effective Stress Model to Analysis of Liquefaction and Seismic Performance of an Earth Dam in China

2015 ◽  
Vol 2015 ◽  
pp. 1-7 ◽  
Author(s):  
Changqing Qi ◽  
Wei Lu ◽  
Jimin Wu ◽  
Xing Liu
Keyword(s):  
Pore Pressure ◽  
Seismic Performance ◽  
Effective Stress ◽  
Earth Dam ◽  
Dam Failure ◽  
Excess Pore Pressure ◽  
Stress Model ◽  
Gravelly Soil ◽  
Excess Pore

Earthquake-induced liquefaction is one of the major causes of catastrophic earth dam failure. In order to assess the liquefaction potential and analyze the seismic performance of an earth dam in Fujian, Southeastern China, the in situ shear wave velocity test was firstly carried out. Results indicate that the gravelly filling is a type of liquefiable soil at present seismic setting. Then the effective stress model was adopted to thoroughly simulate the response of the soil to a proposed earthquake. Numerical result generally coincides with that of the empirical judgment based on in situ test. Negative excess pore pressure developed in the upper part of the saturated gravelly filling and positive excess pore pressure developed in the lower part. The excess pore pressure ratio increases with depth until it reaches a maximum value of 0.45. The displacement of the saturated gravelly soil is relatively small and tolerable. Results show that the saturated gravelly filling cannot reach a fully liquefied state. The dam is overall stable under the proposed earthquake.

Seismic monitoring short-duration events: liquefaction in 1g models

2007 ◽  
Vol 44 (6) ◽  
pp. 659-672 ◽  
Author(s):  
Jong-Sub Lee ◽  
J Carlos Santamarina
Keyword(s):  
Pore Pressure ◽  
Effective Stress ◽  
Time Scale ◽  
Stress Condition ◽  
High Repetition Rate ◽  
Excess Pore Pressure ◽  
S Wave ◽  
Additional Time ◽  
Small Models ◽  
Excess Pore

The duration of liquefaction in small models is very short, therefore special monitoring systems are required. In an exploratory sequence of liquefaction tests, S-wave transillumination is implemented with a high repetition rate to provide detailed information on the evolution of shear stiffness during liquefaction. These data are complemented with measurements of acceleration, time-varying settlement, excess pore pressure, and resistivity profiles. Measurements show that excess pore pressure migration from liquefied deep layers may cause or sustain a zero effective stress condition in shallow layers, that multiple liquefaction events may take place in a given formation for a given excitation level, and that unsaturated layers may also reach a zero effective stress condition. The time scale for excess pore pressure dissipation in fully submerged specimens is related to particle resedimentation and pressure diffusion; downward drainage from unsaturated shallow layers may contribute an additional time scale. High resolution resistivity profiling reveals the gradual homogenization of the soil bed that takes place during subsequent liquefaction events. The S-wave transillumination technique can be extended to field applications and implemented with tomographic coverage to gain a comprehensive understanding of the spatial and temporal evolution of liquefaction.Key words: densification, electrical resistivity, multiple liquefaction, pore pressure, shear wave, spatial variability.

Liquefaction potential of silts from CPTu

2007 ◽  
Vol 44 (1) ◽  
pp. 1-19 ◽  
Author(s):  
Dawn A Shuttle ◽  
John Cunning
Keyword(s):  
Finite Element ◽  
Pore Pressure ◽  
Earthquake Engineering ◽  
Critical State ◽  
Pressure Ratio ◽  
Excess Pore Pressure ◽  
Liquefaction Potential ◽  
Triaxial Cell ◽  
Excess Pore

Silt tailings (slimes) are difficult materials to test in that, like sands, it is extremely difficult to obtain undisturbed samples and subsequently re-establish them in a triaxial cell for element testing in a laboratory in anything approaching their in situ condition. Evaluation of silt tailing behaviour has to depend on in situ tests, and the piezocone (CPTu) in particular. However, CPTs in silt generate substantial excess pore pressure and there is no established methodology to evaluate the measured responses in terms of soil properties, as drained sand-based CPT interpretation is inapplicable. A case history of particularly loose silt tailings is reported in which the National Center for Earthquake Engineering Research (NCEER) liquefaction assessment method would lead to uncertainty in the liquefaction potential. However, the extremely high CPTu excess pore pressure ratio, Bq, and low dimensionless CPT resistance, Qp, at this site indicates liquefaction is likely occurring during pushing of the CPT. Detailed finite element simulations of the CPT using a critical state model provided an effective stress framework to evaluate the in situ state parameter of the silt from the measured CPT data. This framework shows that the group of dimensionless CPT variables Q(1 – Bq) + 1 is fundamental for the evaluation of undrained response during CPT sounding. And, despite the high silt content, the interpretation indicates that the tailings are indeed liquefiable.Key words: liquefaction, CPT, silt, finite element, critical state.

Effective-Stress Finite Element Analysis of Spudcan Penetration

2012 ◽  
Author(s):  
Jiang Tao Yi ◽  
Fook Hou Lee ◽  
Siang Huat Goh ◽  
Yu Ping Li ◽  
Xi Ying Zhang
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Stress Analysis ◽  
Pore Pressure ◽  
Effective Stress ◽  
Excess Pore Pressure ◽  
Element Analysis ◽  
Pore Pressures ◽  
Excess Pore Pressures ◽  
Excess Pore

The numerical modeling of spudcan penetration involves technical challenges posed by large soil deformation coupled with significant material non-linearity. The Lagrangian approach commonly used for solid stress analysis often does not work well with large deformations, resulting in premature termination of the analysis. Recently, the Arbitrary Langrangian Eulerian (ALE) and the Eulerian methods have been used in spudcan analysis to overcome problems caused by the soil flow and large deformation. However, most of the reported studies are based on total stress analysis and therefore shed no light on the excess pore pressures generated during spudcan installation. As a result, much remains unknown about the long-term behaviour of spudcans in the ground, which is affected by the dissipation of excess pore pressures. This paper reports an effective-stress finite element analysis of spudcan installation in an over-consolidated (OC) soft clay. The Eulerian analysis was conducted using ABAQUS/ Explicit, with the effective stress constitutive models coded via the material subroutine VUMAT. The results demonstrated the feasibility of conducting effective-stress finite element analysis for undrained spudcan penetration in OC clays. The paper discusses the flow mechanism, stable cavity depths and bearing capacity factors when spudcan installation occurs in various OC soils. It was found that the pore pressure build-up concentrates in a bulb-shaped zone surrounding the spudcan. The size of the pore pressure bulb increases with increasing penetration. The maximum excess pore pressure, which is generated near the spudcan tip, is predominantly controlled by the undrained shear strength at the tip level.

scholarly journals PENGARUH MUKA AIR TANAH TERHADAP TEGANGAN EFEKTIF TANAH DASAR CANDI PRAMBANAN BERDASAR METODE ELEMEN HINGGA

2019 ◽  
Vol 18 (1) ◽  
Author(s):  
Tri Wahyu Kuningsih ◽  
Dwi Novi Wulansari
Keyword(s):  
Ground Water ◽  
Water Level ◽  
Pore Pressure ◽  
Effective Stress ◽  
Ground Water Level ◽  
Excess Pore Pressure ◽  
Physical Damage ◽  
World Cultural Heritage ◽  
Excess Pore

ABSTRACTIndonesia which geographically has an area located at 6º LU up to 11º LS and 97º BT up to 141º BT is an area prone to earthquakes. Determination of the temple as a world cultural heritage has implications for the responsibilities and obligations of the Indonesian people in an effort to protect and maintain the building in accordance with the conventions set by UNESCO. The convention, among others, is maintaining the preservation of buildings from the dangers of war, physical damage due to age, and natural disasters. This research was conducted with the aim to determine the effect of groundwater depth and earthquake acceleration on the strength of Prambanan Temple subgrade based on finite element method. Simplification of Siwa Temple as a modeling in software input. The results of the study are the shallower depth of the ground water level, the effective stress of the soil will also be reduced. When effective stress decreases, the strength of the soil will also decrease. The deeper the depth of the water table, the effective stress of the soil increases. The depth of the ground water level affects the amount of excess pore pressure. The more shallow the depth of the ground water level, the amount of excess pore pressure will also increase even the value is positive. The deeper the depth of the ground water level, the greater the amount of excess pore pressure decreases even the value is negative.Key words : Prambanan Temple, effective stresses, excess pore pressureABSTRAKIndonesia yang secara geografis mempunyai wilayah yang terletak pada 6º LU sampai dengan 11 º LS serta 97º BT sampai dengan 141º BT merupakan daerah yang rawan terhadap gempa bumi. Penetapan candi sebagai warisan budaya dunia berimplikasi pada tanggung jawab dan kewajiban bangsa Indonesia dalam upaya melakukan pelindungan dan pemeliharaan bangunan tersebut sesuai dengan konvensi yang telah ditetapkan oleh UNESCO. Konvensi tersebut antara lain menjaga pelestarian bangunan dari bahaya perang, kerusakan fisik karena termakan usia, dan bencana alam. Penelitian ini dilakukan dengan tujuan untuk mengetahui pengaruh kedalaman muka air tanah dan percepatan gempa terhadap kekuatan tanah dasar Candi Prambanan berdasar metode elemen hingga. Ilustrasi penyederhanaan Candi Siwa sebagai pemodelan dalam input perangkat lunak. Hasil penelitian adalah semakin dangkal kedalaman muka air tanah, maka tegangan efektif tanah juga akan berkurang. Pada saat tegangan efektif berkurang maka kekuatan tanah juga akan berkurang. Semakin dalam kedalaman muka air tanah, tegangan efektif tanah semakin meningkat. Kedalaman muka air tanah mempengaruhi besarnya excess pore pressure. Semakin dangkal kedalaman muka air tanah, besarnya excess pore pressure juga akan meningkat bahkan nilainya positif. Semakin dalam kedalaman muka air tanah, besarnya excess pore pressure semakin menurun bahkan nilainya negatif.Kata kunci : candi prambanan, tegangan efektif, excess pore pressure.

scholarly journals Comparison of Coupled and Uncoupled Consolidation Equations Using Finite Element Method in Plane-Strain Condition

2016 ◽  
Vol 2 (8) ◽  
pp. 375-388 ◽  
Author(s):  
Mohamadtaqi Baqersad ◽  
Abbas Eslami Haghighat ◽  
Mohammadali Rowshanzamir ◽  
Hamid Mortazavi Bak
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Pore Pressure ◽  
Effective Stress ◽  
Excess Pore Pressure ◽  
Soil Deformation ◽  
Soil Consolidation ◽  
Time Step ◽  
Excess Pore ◽  
Element Method

In the current paper, the consolidation settlement of a strip footing over a finite layer of saturated soil has been studied using the finite element method. In Biot’s coupled consolidation equations, the soil deformation and excess pore pressure are determined simultaneously in every time step which refers to the hydro-mechanical coupling. By considering a constant total stress throughout the time and by assuming that volume strain is a function of isotropic effective stress, uncoupled consolidation equations can be obtained using coupled consolidation equations. In these uncoupled equations, excess pore pressure and deformation are determined separately. In this approach, the excess pore pressure can be identified in the first stage. Using the calculated excess pore pressure, the soil deformation is determined through effective stress-strain analyses. A computer code was developed based on coupled and uncoupled equations that are capable of performing consolidation analyses. To verify the accuracy of these analyses, the obtained results have been compared with the precise solution of Terzaghi’s one-dimensional consolidation theory. The capability of these two approaches in estimation of pore water pressure and settlement and to show Mandel-Crayer’s effect in soil consolidation is discussed. Then, the necessity of utilizing coupled analyses for evaluating soil consolidation analysis was investigated by comparing the coupled and uncoupled analyses results.

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.

The Test Study to the Changes of Excess Pore Water Pressure during Precast Pile Construction

2012 ◽  
Vol 193-194 ◽  
pp. 1010-1013
Author(s):  
Shu Qing Zhao
Keyword(s):  
Pore Water ◽  
Clayey Soil ◽  
Pore Water Pressure ◽  
Water Pressure ◽  
Excess Pore Pressure ◽  
Soil Pressure ◽  
Excess Pore Water Pressure ◽  
Test Study ◽  
Excess Pore

The construct to precast pile in thick clayey soil can cause the accumulation of excess pore water pressure. The high excess pore pressure can make soil, buildings and pipes surrounded have large deflection, even make them injured. Combining with actual projects, this paper presents an in-situ model test on the changes of excess pore water pressure caused by precast pile construct. It is found that the radius of influence range for single pile driven is about 15m，the excess pore water pressure can reach or even exceed the above effective soil pressure, and there are two relatively stable stages.

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