Observed and calculated pore pressures and deformations induced by an earth balance shield

1993 ◽  
Vol 30 (3) ◽  
pp. 476-490 ◽  
Author(s):  
X. Yi ◽  
R. Kerry Rowe ◽  
K.M. Lee
Keyword(s):  
Finite Element ◽  
Numerical Technique ◽  
Field Measurements ◽  
Time Dependent ◽  
Creep Tests ◽  
Viscoplastic Model ◽  
Pore Pressures ◽  
Triaxial Creep ◽  
Consolidation Analysis ◽  
Triaxial Creep Tests

The observed pore pressures and deformations induced by an earth balance shield used to construct the Furongjiang sewer tunnel in soft saturated ground in Shanghai, China, are briefly described. A numerical technique for predicting these pore pressures and deformations is outlined. This approach adopts a coupled viscoplastic-consolidation analysis to describe the time-dependent deformations and strain-hardening behaviour of the soil using parameters obtained from triaxial creep tests. A comparison is then made between numerical results and the results of field measurements, and it is shown that there is encouraging agreement between the calculated and observed response. Key words : tunnelling, finite element, settlements, viscoplastic model, consolidation, field measurement.

A NONLINEAR VISCOELASTIC-PLASTIC RHEOLOGICAL MODEL FOR ROCKS BASED ON FRACTIONAL DERIVATIVE THEORY

2013 ◽  
Vol 27 (25) ◽  
pp. 1350149 ◽  
Author(s):  
HONGJIE CHEN ◽  
WEIYA XU ◽  
WEI WANG ◽  
RUBIN WANG ◽  
CHONG SHI
Keyword(s):  
Rheological Model ◽  
Soft Matter ◽  
Fractional Derivatives ◽  
High Stress ◽  
Creep Tests ◽  
Creep Stage ◽  
Accelerated Creep ◽  
Triaxial Creep ◽  
Triaxial Creep Tests ◽  
The Ideal

The soft-matter element between the ideal solid and the ideal liquid is established and is described based on the definition of the fractional derivatives. By replacing a component in the generalized Kelvin model with the soft-matter component and connecting it in series with a nonlinear visco-plastic body, a nonlinear viscoelasto-plastic rheological model is proposed based on the fractional derivatives in order to describe the rheological behaviors of rocks. The data obtained from the triaxial creep tests of a typical rock are simulated with this model and the fitting result is good. The model can describe well three rheological stages of the rock during the triaxial creep tests. The validity of this model is then discussed. In this model, the fractional order β controls creep strain rate in the stable creep stage under the condition of low stress; while the creep index n controls creep rate of the accelerated rheological stage under the condition of high stress. Few parameters and good simulation results manifest the outstanding performance of the model. The model also adopts the damage theory to describe the progressive deterioration of rock viscous coefficient of the accelerated creep stage. The model can also give an excellent description of the three rheological stages of rocks, especially the accelerated creep stage.

Viscoelastic Finite Element Modeling of Bimodal High Density Polyethylene (HDPE) Piping Materials for Nuclear Safety-Related Applications

2010 ◽  
Author(s):  
Do-Jun Shim ◽  
Prabhat Krishnaswamy ◽  
Yunior Hioe ◽  
Sureshkumar Kalyanam
Keyword(s):  
Finite Element ◽  
Service Life ◽  
High Density Polyethylene ◽  
Viscoelastic Behavior ◽  
Time Dependent ◽  
Tensile Creep ◽  
Uniaxial Tensile ◽  
Fe Model ◽  
Creep Tests ◽  
Uniaxial Tensile Creep

The U.S. Nuclear Regulatory Commission (USNRC) has recently approved Relief Requests for the use of high density polyethylene (HDPE) piping in safety-related applications. The ASME Boiler and Pressure Vessel Code, meanwhile, has developed Code Case N-755 that defines the design and service life requirements for PE piping in nuclear plants though it has not as yet been approved by the USNRC. One of the issues of concern is premature failure of PE piping due to slow crack growth (SCG) that can initiate due to a combination of sustained loads, elevated temperatures, and a pre-existing defect. Understanding and predicting the SCG behavior is an essential step in developing a methodology for predicting the service life of PE piping. The first step in studying the failure process in a polymer under a constant sustained load is the selection of a suitable constitutive model to represent the time-dependent behavior of the material. In this paper, uniaxial tensile creep tests were performed for a bimodal HDPE (PE4710) piping material. This creep data was used to determine the viscoelastic material constants for this bimodal HDPE using a power-law creep model. These material constants were used in finite element (FE) analyses to study the viscoelastic behavior of the bimodal HDPE. As a first step, the FE model was verified by comparing the results from numerical simulations and experiments for a set of uniaxial tensile creep tests. The FE model was then applied to study the viscoelastic behavior of a SCG specimen. The time dependent stress and strain fields were investigated.

Undrained behavior of embankments on New Liskeard varved clay

1977 ◽  
Vol 14 (3) ◽  
pp. 367-388 ◽  
Author(s):  
Suzanne M. Lacasse ◽  
Charles C. Ladd ◽  
Alex K. Barsvary
Keyword(s):  
Finite Element ◽  
Effective Stress ◽  
Field Measurements ◽  
Excess Pore Pressure ◽  
Strength Parameters ◽  
Finite Element Program ◽  
Pore Pressures ◽  
Element Program ◽  
Varved Clay ◽  
Excess Pore

The performance, including a failure, of two embankments in New Liskeard, Ontario is analysed. The underlying medium-to-soft varved clay foundation is studied with respect to stability, undrained deformations, and excess pore pressure distribution.Total stress stability analyses were performed with undrained strengths based on measured and corrected field vane strengths, the average unconfined compression and unconsolidated undrained strength, and SHANSEP strength parameters with and without anisotropy. Several approaches yielded satisfactory factors of safety and reasonable critical arcs. Effective stress analyses using pore pressures predicted from finite element analyses showed that either the effective stress strength parameters were much lower than those measured in the laboratory or the predicted pore pressures at failure were much too low.Undrained deformations and excess pore pressures at end-of-construction were predicted with the finite element program FEECON. The values were generally consistent with field measurements for an embankment located 60 m from the failure area.

scholarly journals Triaxial creep tests of glacitectonically disturbed stiff clay – structural, strength, and slope stability aspects

2021 ◽  
Vol 13 (1) ◽  
pp. 1118-1138
Author(s):  
Łukasz Kaczmarek ◽  
Paweł Dobak ◽  
Tomasz Szczepański ◽  
Kamil Kiełbasiński
Keyword(s):  
Soil Structure ◽  
Creep Process ◽  
Triaxial Tests ◽  
Strength Parameters ◽  
Creep Tests ◽  
Geological Time Scale ◽  
Creep Stage ◽  
Strength Tests ◽  
Triaxial Creep ◽  
Triaxial Creep Tests

Abstract This study concerns the creep impact on strength parameters of the selected very cohesive soils (PI = 30–70%). The analysis refers to Neogene clays characterized by a complex structure, resulting directly from a complicated load history in the geological time scale and identified glacitectonic deformations. In the process of samples’ preparation for strength tests as well as during the interpretation of the post-failure state, particular attention was paid to the soil structure. The imaging methods (X-ray densitometry and computer microtomography) enabled the comparison of the soil structure and the selection of samples with similar characteristics. The completed program of strength tests consisted of two series of tests in the triaxial stress state, differentiated by the occurrence of the initial creep stage, preceding the typical strength test scheme under undrained conditions. This study allowed to obtain a quantitative assessment of the influence of the creep process on the strength parameters of tested soils. Constant stress lower than 60% of the shear stress deviator leads to the deceleration creep course (m parameter 0.64–0.89). As a result, higher values of internal friction angle (20% increase comparing to triaxial tests without creep stage) and cohesion reduction are obtained from triaxial creep tests. Creep parameter m is found to be a valuable indicator for differentiation of landslide activity trend. The tests proved low values of axial strains (1–5%) at failure, which was associated with lithogenesis. By the implementation of obtained strength parameters into the 3D finite element model of the slope, the potential influence of the creep process on the stability of an exemplary cross section of the Warsaw slope could be determined.

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