The measurements of soil parameters relevant to tunnelling in clays

1985 ◽  
Vol 22 (3) ◽  
pp. 375-391 ◽  
Author(s):  
Robert M. C. Ng ◽  
K. Y. Lo
Keyword(s):  
Shear Modulus ◽  
Deformation Modulus ◽  
Stress Path ◽  
Triaxial Tests ◽  
Soil Parameters ◽  
Silty Clay ◽  
Elastic Parameters ◽  
Soft Clays ◽  
Anisotropic Elastic ◽  
Stress States

A comprehensive laboratory program was carried out on specimens trimmed from 152 mm diameter piston samples of a soft silty clay and a varved clay at a tunnel site in Thunder Bay. Results of conventional triaxial tests as well as special tests for the determination of anisotropic elastic parameters, simple shear tests, and stress path tests are presented.Results indicate that the unloading moduli are about twice the loading moduli, the Poisson's ratios in unloading are about three times those in loading, but the independent shear modulus is relatively unaffected. While the modulus is sensitive to mode of consolidation, drainage, and direction of stress path, the stress states at failure of all the different types of tests fall close to a single envelope for compression and extension. The choice of soil parameters for the analysis of deformation in tunnelling in soft clays is discussed. Key words: clay, tunnelling, stress path, deformation modulus, shear modulus, anisotropic elastic parameters, failure envelope.

Effects of Stress Path and Stress History on the Stiffness of Reconstituted London Clay

1986 ◽  
Vol 2 (1) ◽  
pp. 139-144 ◽  
Author(s):  
J. H. Atkinson ◽  
J. S. Evans ◽  
D. Richardson
Keyword(s):  
Stress Path ◽  
Triaxial Tests ◽  
Soil Parameters ◽  
Stress History ◽  
Strain Behaviour ◽  
Reconstituted Soil ◽  
Path Dependent ◽  
London Clay ◽  
Soil Behaviour

AbstractSoil behaviour is stress history dependent and stress path dependent and soil parameters, particularly those for stress-strain behaviour, measured in conventional triaxial tests may not represent the behaviour of soil in many civil engineering works.To obtain more realistic parameters it may be necessary to conduct laboratory tests which more closely represent in situ conditions before and during construction.The paper describes equipment developed at The City University to carry out stress path tests simply and economically. A series of CU triaxial tests and stress path tests on reconstituted soil illustrate the dependence of measured soil parameters on stress history and stress path.

Unbound Aggregate Rutting Models for Stress Rotations and Effects of Moving Wheel Loads

2005 ◽  
Vol 1913 (1) ◽  
pp. 41-49 ◽  
Author(s):  
In Tai Kim ◽  
Erol Tutumluer
Keyword(s):  
Test Data ◽  
Permanent Deformation ◽  
Confining Pressure ◽  
Stress Path ◽  
In Situ Stress ◽  
Triaxial Tests ◽  
Wheel Loading ◽  
Stress States ◽  
Granular Layers ◽  
Unbound Aggregate

The latest research findings on stress rotations caused by moving wheel loads and their effects on permanent deformation or rut accumulation in pavement granular layers are presented. Realistic pavement stresses induced by moving wheel loads were examined in the unbound aggregate base and subbase layers, and the significant effects of rotation of principal stress axes were indicated for a proper characterization of the permanent deformation behavior. To account for the rutting performances of especially thick granular layers, a comprehensive set of repeated load triaxial tests was conducted in the laboratory. Triaxial test data were obtained and analyzed from testing aggregates under various realistic in situ stress paths caused by moving wheel loading. Permanent deformation characterization models were then developed on the basis of the experimental test data to include the static and dynamic stress states and the slope of stress path loading. The models that also considered the stress path slope variations predicted the stress path dependency of permanent deformation accumulation best. In addition, multiple stress path tests conducted to simulate the extension–compression–extension type of rotating stress states under a wheel pass gave much higher permanent strains than those of the compression-only single path tests. The findings indicated actual traffic loading simulated by the multiple path tests could cause greater permanent deformations or rutting damage, especially in the loose base or subbase, when compared with deformations measured from a dynamic plate loading or a constant confining pressure type laboratory test.

Effects of Complex Initial Stress State Parameters on Dynamic Shear Modulus of Loess

2011 ◽  
Vol 243-249 ◽  
pp. 2601-2606 ◽  
Author(s):  
Zhi Jie Wang ◽  
Ya Sheng Luo ◽  
Hong Guo
Keyword(s):  
Stress State ◽  
Shear Modulus ◽  
Principal Stress ◽  
Initial Stress ◽  
Triaxial Tests ◽  
Dynamic Shear Modulus ◽  
Dynamic Shear ◽  
Initial Stress State ◽  
Foundation Soil ◽  
Stress States

The foundation soil of the buildings and structures is often in complex initial stress states. The dynamic torsional shear triaxial tests are carried out on undisturbed and remodeling loess under different complex initial stress states by using the remolded DTC-199 torsional cyclic load triaxial apparatus, and the effects of each complex initial stress state parameter on dynamic shear modulus of loess are discussed. Results show that, other conditions being the same, the influence of angles of initial principal stressα0on dynamic shear modulusGdof loess show a trend of the biggerα0is, the smallerGdis. The effect laws of efficient of initial intermediate principal stressb0onGdof loess are not obvious. When the dynamic shear strain is larger, the bigger initial deviator stress ratioη0is, the smallerGdof loess is. The influence of initial average principal stresspm0on loess is significant. The biggerpm0is, the biggerGdof loess is.Gdof undisturbed loess is greater than that of remodeling loess under the complex initial stress states.

Determination of Elastic and Plastic Subgrade Soil Parameters for Asphalt Cracking and Rutting Prediction

1996 ◽  
Vol 1540 (1) ◽  
pp. 97-104 ◽  
Author(s):  
G. Behzadi ◽  
W. O. Yandell
Keyword(s):  
Moisture Content ◽  
Constitutive Model ◽  
Permanent Deformation ◽  
Triaxial Tests ◽  
Deformation Analysis ◽  
Soil Parameters ◽  
Dry Density ◽  
Silty Clay ◽  
Exponential Relationship ◽  
Deviator Stress

A preliminary step in the prediction of rutting and cracking in a number of accelerated loading facility trials in Australia is presented. The results of laboratory repeated load triaxial tests were used to characterize the residual and resilient deformation of a silty clay subgrade material. The analysis of permanent deformation indicated that the well-known model ∈p = INS can be used to estimate the accumulated strain at any number of loading cycles. The parameter S (the slope of the line in a plot of log ∈p –log N) was found to be independent of stress and density, but very small increases were observed as moisture content increased. The parameter I (the intercept in a plot of log ∈p –log N) was found to be most sensitive to deviator stress. The test results also indicated that I increased with increasing moisture content and decreased as dry density increased. The analysis revealed that an exponential relationship existed between I and deviator stress. This relationship was used to develop a constitutive model for silty clay based on the previously mentioned well-known model. The constitutive model obtained would be able to predict the plastic strain under any number of loads at any specified stress level. Resilient deformation analysis has shown that resilient modulus initially decreased rapidly with increasing deviator stress and then increased slightly or was nearly constant. The elastic and plastic parameters will be used as input for performance predictors such as VESYS and Mechano-Lattice.

UNDRAINED SHEAR STRENGTH OF K0 CONSOLIDATED SOFT CLAYS UNDER TRIAXIAL AND PLANE STRAIN CONDITIONS

2014 ◽  
Vol 06 (03) ◽  
pp. 1450032 ◽  
Author(s):  
QIUSHENG WANG ◽  
XIULI DU ◽  
QIUMING GONG
Keyword(s):  
Shear Strength ◽  
Plane Strain ◽  
Yield Surface ◽  
Critical State ◽  
Volumetric Strain ◽  
Stress Path ◽  
Undrained Shear Strength ◽  
Triaxial Tests ◽  
Soft Clays ◽  
Undrained Shear

Theoretical formulas for predicting the undrained shear strength of K0 consolidated soft clays under the stress path related to triaxial and plane strain tests are presented within the framework of critical state soil mechanics. An inclined elliptical yield surface is adopted to take account of the initial anisotropic stress state. The undrained strength is determined by combining the undrained stress path in the volumetric stress–strain space and the initial yield surface in the deviator-mean stress space. The derived mathematical expressions are functions of the critical state frictional angle, the plastic volumetric strain ratio and the overconsolidation ratio, which can be simplified into the solutions for isotropically consolidated clays under triaxial tests or under plane strain tests. The results calculated by using the theoretical formulas obtained in this paper are in good agreement with the available collected test results. It indicates that these new formulas are applicable to triaxial and plane strain tests on normally and lightly to moderately overconsolidated soft clays.

A deep retaining structure in till and sand. Part I: Stress path effects

1983 ◽  
Vol 20 (1) ◽  
pp. 120-130 ◽  
Author(s):  
L. V. Medeiros ◽  
Z. Eisenstein
Keyword(s):  
Plane Strain ◽  
Principal Stress ◽  
Stress Path ◽  
Triaxial Tests ◽  
Silty Clay ◽  
Stress Strain ◽  
Retaining Structure ◽  
Major Principal Stress ◽  
Minor Principal Stress ◽  
Passive Compression

Laboratory investigation of the stress–strain behaviour of glacial till (stiff silty clay) and dense preglacial sand have been carried out. Special attention has been devoted to investigation of the influence of different stress paths on the stress–strain response of these materials. Since these tests were performed primarily for an analytical study of the behaviour of a deep retaining structure, the stress paths chosen for testing were typical of stress conditions for this field situation. Triaxial and plane strain drained tests on till were run in passive compression (with increasing major principal stress and constant minor principal stress) and in active compression (with constant major principal stress and decreasing minor principal stress). On the sand, only triaxial tests were carried out. These experiments were in passive compression and in active extension (with decreasing major principal stress and constant minor principal stress).The results of different tests were compared at corresponding stress and strain levels. They indicated an appreciably decreased stiffness along the passive compression stress path compared with that in the active compression and active extension tests. Also, a comparison between the triaxial and plane strain tests for the till showed a marked influence of the intermediate principal stress. Although the results were intended for use in a stress path dependent, nonlinear elastic analysis they are discussed and explained in terms of a more general elastoplastic model of soil behaviour. Keywords: stress–strain relationship, stress path, laboratory testing, stiff clay, dense sand.

scholarly journals Stiffness of lightly cemented sand under multiaxial loading

2019 ◽  
Vol 92 ◽  
pp. 11008
Author(s):  
Marina Bellaver Corte ◽  
Erdin Ibraim ◽  
Lucas Festugato ◽  
Andrea Diambra ◽  
Nilo Cesar Consoli
Keyword(s):  
Shear Modulus ◽  
Young’S Modulus ◽  
Young's Modulus ◽  
Stress Path ◽  
Silica Sand ◽  
Triaxial Tests ◽  
Cemented Sand ◽  
Content Ratio ◽  
Hollow Cylinder Torsional Apparatus ◽  
Set Up

This paper presents experimental triaxial tests conducted on two lightly cemented sand samples on the set-up conditions of a Hollow Cylinder Torsional Apparatus (HCTA). The laboratory study has been carried out on an angular to sub-angular silica sand reinforced with Portland cement of high early strength. The samples have identical porosity/volumetric cement content ratio, η/Civ, values. The Young's modulus and shear modulus were measured by the application of a series of small unload-reload cycles at different investigation points along the triaxial stress path up to about 50% of the maximum deviatoric stress. At these investigation points, additional series of unload-reload cycles of higher amplitudes were also applied and the stiffness moduli assessed using local instrumentation. While the peak strength seems to be controlled by the density of the sand matrix, as extensive bond cementation damages occur at peak and pre-peak stages, the Young's modulus and shear modulus normalised by the void ratio function show the effect of the cementation ratio with higher values for the sample with higher cementation ratio.

An analysis of three-dimensional ground movements: the Thunder Bay tunnel

1991 ◽  
Vol 28 (1) ◽  
pp. 25-41 ◽  
Author(s):  
K. M. Lee ◽  
R. K. Rowe
Keyword(s):  
Finite Element ◽  
Three Dimensional ◽  
Triaxial Tests ◽  
Soil Parameters ◽  
Tunnel Face ◽  
Element Analysis ◽  
Soft Clays ◽  
Ground Deformations ◽  
Thunder Bay ◽  
Stress Dependent

A three-dimensional (3D) elastoplastic finite-element analysis, which is capable of simulating the advance of a tunnelling shield and the associated ground losses resulting from the tunnelling process, is used to calculate the deformations caused by the excavation of the Thunder Bay sewer tunnel. The soil parameters adopted in the analysis were based on the results determined from stress-dependent triaxial tests. The results of this analysis are compared with the measured soil displacements. Reasonable agreement between the calculated and observed 3D settlement distribution and horizontal displacements at different distances from the tunnel face is reported. This overall agreement for displacements under 3D conditions suggests that the method of analysis may be applicable to design problems involving tunnelling in soft clays similar to that at the Thunder Bay sewer tunnel provided that the soil parameters are reliably determined. Key words: tunnelling, three-dimensional analysis, finite element, elastoplastic displacements, ground deformations, Thunder Bay tunnel.

A Shearing Strain Model for Cylindrical Stress States

2019 ◽  
Vol 62 (1) ◽  
pp. 225-230
Author(s):  
Clarence E. Johnson ◽  
Alvin C. Bailey ◽  
Thomas R. Way
Keyword(s):  
Shear Stress ◽  
Principal Stress ◽  
Maximum Shear Stress ◽  
Volumetric Strain ◽  
Triaxial Tests ◽  
Soil Parameters ◽  
Shear Stresses ◽  
Stress States ◽  
Shearing Strain ◽  
Strain Model

Abstract. A shearing strain model for soil was developed that includes soil behavior under compressive normal and shear stresses great enough to attain maximum compaction. The model was developed for a clay and a clay loam from triaxial data with various stress loading paths. This model relates the ratio of maximum shear stress acting on the cylindrical sample (tmax) to major principal stress (s1), to the ratio of maximum natural shearing strain to natural volumetric strain occurring after shear stress is initiated. The model accurately describes the shearing distortion of triaxial soil samples under cylindrical stress loading prior to yielding by plastic flow. This model predicts soil shearing strain for input stress states that realistically represent field conditions. Keywords: Principal stress and strain, Shearing strain, Shear stress, Soil compaction, Soil parameters, Triaxial tests.

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