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.

Prediction of Trifluralin Diffusion Coefficients

Weed Science ◽  
1973 ◽  
Vol 21 (5) ◽  
pp. 485-489 ◽  
Author(s):  
L. E. Bode ◽  
C. L. Day ◽  
M. R. Gebhardt ◽  
C. E. Goering
Keyword(s):  
Soil Moisture ◽  
Moisture Content ◽  
Diffusion Coefficients ◽  
Moisture Diffusion ◽  
Soil Parameters ◽  
Void Space ◽  
Exponential Relationship ◽  
Maximum Value ◽  
Soil Temperatures ◽  
Dry Soil

In the range of 4.4 to 49 C, there is an exponential relationship between temperature and trifluralin (α,α,α-trifluoro-2,6-dinitro-N,N-dipropyl-p-toluidine) diffusion coefficients. Diffusion is low in air-dry soil for all temperatures. It increases to a maximum value when the soil has between 8 and 15% w/w soil moisture content and then decreases steadily as moisture content increases. When the air-filled fraction of soil void space is reduced below approximately 40% v/v by either compression or addition of moisture, diffusion begins to decrease. An equation was developed to predict trifluralin diffusion coefficients from a factorial experiment with seven soil moisture contents, five soil temperatures, and two bulk densities. Diffusion coefficients range from 3.8 X 10-11 cm2/sec to 2.8 X 10-6 cm2/sec. Fifteen terms are required in the prediction model to describe accurately the response surface of trifluralin diffusion coefficients. With the equation it is possible to predict trifluralin diffusion coefficients for any combination of measured soil parameters as long as they are represented by the range of the variables used in the experiment.

scholarly journals Assessment of Geotechnical Parameters of Lateritic Soil of Jos and Environs, for Civil Engineering Constructions North Central part of Nigeria

2020 ◽  
Vol 3 (3b) ◽  
pp. 222-239
Author(s):  
E Vincent ◽  
P Dominic ◽  
MM Kure
Keyword(s):  
Moisture Content ◽  
Civil Engineering ◽  
Biotite Granite ◽  
Engineering Properties ◽  
Dry Density ◽  
Sieve Analysis ◽  
Base Line ◽  
Silty Clay ◽  
Geotechnical Parameters ◽  
Engineering Construction

Due to failures of Civil Engineering structures in Jos and its Environs, Geotechnical parameters of Lateritic soils were carried out in order to determine its engineering properties for civil engineering construction. The methods involved are; reconnaissance survey, site works, laboratory tests based on British Standard (BS) methods and interpretation of the results. The laboratory test of the soils revealed that the Atterberg limit; Liquid limit (LL) ranged from 33.0% to 45.0%, Plastic limit (PL) from 16.23% to 26.37%, and Plasticity index (PI) from 8.63% to 22.67%. The percentage passing from the Sieve analysis ranges from 31.62% to 67.66%. The cohesive strength (c) and angle of internal friction (ø) from direct shear test ranged from 13KN/m2 to 24KN/m2 and 9° to 26°. The values of the Total settlement (Pc) from the Consolidation test ranged from 0.0005m to 0.0019m, Soil pH from 5.2 to 7.8, Specific gravity (SG) from 2.57 to 2.73 and Natural Moisture Content (NMC) from 8.18% to 46.36%. From the compaction test; the Optimum Moisture Content (OMC) ranged from 15.22% to 20.60% and Maximum Dry Density (MDD) from 1.62g/cm3 to 1.84g/cm3. The California Bearing Ratio (CBR) test for the soaked soils ranged from 21.0% to 93.0% and Un-soaked values from 50.75% to 96.61%. The findings reveal that; the geology of the area can be largely classified into granites (Biotite-microgranite, N’gell biotite-granite, Jos-biotite-granite and Aplo-pegmatitic granite-gneiss) and laterites. The geotechnical parameters of the soil are characteristically fair to poor, the strength and deformation of the soil reveals that it can mostly be used as a sub-base materials. The soil is classified as silty-clay, and the area need to be stabilized with cement, sand and gravel before carry civil engineering constructions. The results obtained will serve as base-line information for civil engineering construction in the study area in other to avoid structural damage.

scholarly journals Experimental and Numerical Research on Utilizing Modified Silty Clay and Extruded Polystyrene (XPS) Board as the Subgrade Thermal Insulation Layer in a Seasonally Frozen Region, Northeast China

2019 ◽  
Vol 11 (13) ◽  
pp. 3495 ◽  
Author(s):  
Qinglin Li ◽  
Haibin Wei ◽  
Peilei Zhou ◽  
Yangpeng Zhang ◽  
Leilei Han ◽  
...  
Keyword(s):  
Moisture Content ◽  
Thermal Insulation ◽  
Composite Layer ◽  
Solid Particles ◽  
Dry Density ◽  
Silty Clay ◽  
Insulation Property ◽  
Frost Depth ◽  
The Stability ◽  
Thermal Insulation Property

For strengthening sustainability of subgrade life-cycle service performance and storing industry solid wastes in seasonally frozen regions, compared to previous research of modified silty clay (MC) which consisted of oil shale ash (OSA), fly ash (FA), and silty clay (SC), we identified for the first time, the variations in the thermal insulation capability of MC with different levels of dry density and moisture content. Taking into consideration the effects of 0–20 freeze-thaw (F-T) cycles by a laboratory test, and by the numerical simulation of coupling moisture-temperature, while considering the effects of F-T cycles, the thermal insulation capability of the MC board and the XPS board were studied quantitatively. The testing results show that the thermal conductivity of MC and SC gradually decreases as the number of F-T cycles increases, and that of the XPS board increases with the increased number of F-T cycles, and tend to be of a constant value of 0.061 W/m/K after 17 F-T cycles. The specific heat capacity of the solid particles of the MC, SC, and XPS board does not change regularly as their moisture content, and the number of F-T cycles change, and their variations are in the range of the test error (2%). Simulation results show that MC has the advantage of the thermal insulation property to reduce the frost-depth of 0.21 m, and the thermal insulation property of the composite layer consisting of the MC and XPS board is greater to reduce the frost-depth of 0.55 m, so that it can protect both the SC and sand gravel of the experimental road from the frost heave damage. The research methods and results are very significant in accurately evaluating the thermal insulation capacity and the sustainability of MC and the composite layer consisting of the MC and XPS board, strengthening the stability of the subgrade and increasing the availability of industrial waste.

Nonlinear Constitutive Model of Soil-bentonite Based on Triaxial Tests along Different Stress Paths

2020 ◽  
Author(s):  
Pengcheng Ma ◽  
Han Ke ◽  
Xing Tong ◽  
Yun Min Chen
Keyword(s):  
Constitutive Model ◽  
Test Data ◽  
Nonlinear Model ◽  
Large Scale ◽  
Triaxial Tests ◽  
Silty Clay ◽  
Cutoff Wall ◽  
Model Framework ◽  
Nonlinear Constitutive Model ◽  
Modified Cam Clay

To investigate the constitutive behavior of soil-bentonite, which is commonly used as the backfill of cutoff walls, a series of triaxial tests were conducted along different stress paths. The tested soil-bentonite comprises 5% Wyoming bentonite and 95% silty clay excavated from a landfill site located in Jiangsu Province, China. Some mechanical properties of the soil-bentonite, including the compression characteristic, shearing characteristic, and coupled deformation of mean and deviatoric stress, were discussed based on the test data. Then, a nonlinear constitutive model was developed under the axisymmetric condition based on a modified hypoelastic model framework. All six independent parameters included in the model were calibrated according to the test data. The mechanical behaviors that the triaxial tests revealed can be fully reflected by the nonlinear model; therefore, it can reasonably describe the stress-strain behaviors of the soil-bentonite in triaxial tests of this study and another literature. Compared with the Modified Cam-Clay model, the prediction effect for the shear strain of the nonlinear model is better. According to a large-scale in-situ test employing a soil-bentonite cutoff wall, the actual stress paths of soil-bentonite are basically included in the application scope of the nonlinear model, preliminarily indicating its applicability for practical engineering projects.

scholarly journals Critical Dynamic Stress and Accumulative Deformation Evolution of Embankment Silty Clay Subjected to Cyclic Freeze-Thaw

2021 ◽  
Vol 2021 ◽  
pp. 1-9
Author(s):  
Lina Wang ◽  
Zhiyu Weng ◽  
Tianliang Wang ◽  
Qiang Liu ◽  
Guoyu Li ◽  
...  
Keyword(s):  
Plastic Strain ◽  
Dynamic Stress ◽  
Permanent Deformation ◽  
Triaxial Tests ◽  
Silty Clay ◽  
Cold Regions ◽  
Freeze Thaw ◽  
Critical Dynamic ◽  
Permanent Settlement ◽  
Embankment Stability

In cold regions, the permanent settlement of embankment is mainly caused by the repeated freeze-thaw process and long-term repeated train loads. Meanwhile, the critical dynamic stress (σdcr) is an important parameter index for determining embankment stability. Therefore, the accumulative permanent deformation evolution and critical dynamic stress of embankment soil subjected to cyclic freeze-thaw were studied using dynamic triaxial tests. Firstly, a numerical model for calculating critical dynamic stress considering the repeated freeze-thaw process was proposed, which shows that the critical dynamic stress of embankment soil rapidly decreases in the first two repeated freeze-thaw cycles, whereas it tends to be stable after the subsequent freeze-thaw process. Next, based on the normalization of the critical dynamic stress, an explicit model for predicting accumulative plastic strain (εp) of embankment soil was established. The above model considers freeze-thaw times, repeated dynamic stress amplitude (σd), and loading times, in which all material parameters of Qinghai-Tibet silty clay were presented. Thus, the critical dynamic stress and accumulative plastic strain models established in this paper can be applied to judge the embankment stability and predict the embankment settlement induced by train loads in cold regions.

scholarly journals Effect of Reinforcement on Properties of Silty Sand

2021 ◽  
Vol 9 (12) ◽  
pp. 1934-1938
Author(s):  
Dr. G. Sireesha
Keyword(s):  
Moisture Content ◽  
Normal Stress ◽  
Axial Strain ◽  
Optimum Moisture Content ◽  
Silty Sand ◽  
Dry Density ◽  
Maximum Dry Density ◽  
Strain Behavior ◽  
Deviator Stress ◽  
Water Contents

Abstract: The variation of the stress-strain behavior and shear -parameters of reinforced silty sand is studied. The geotextiles were provided at different heights in the sample and tested in unconsolidated undrained condition. Two types of geotextiles, woven and nonwoven were used as reinforcement and the experiment was conducted at three water contents. Tests were performed on samples prepared at OMC, dry of OMC and wet of OMC in order to study the effect of water content. The results demonstrated that geotextile inclusion increases the peak strength, axial strain at failure. The sample was found to fail due to bulging between the layers. Keywords: Optimum Moisture Content, Maximum Dry Density, Unconsolidated Undrained, Deviator Stress, Normal Stress

Simulation on Strain Softening of over-Consolidated Clayey Soil by Binary Medium Model

2011 ◽  
Vol 90-93 ◽  
pp. 1322-1325
Author(s):  
Yong Hong
Keyword(s):  
Nonlinear Deformation ◽  
Strain Softening ◽  
Clayey Soil ◽  
Soil Mass ◽  
Triaxial Tests ◽  
Deformation Analysis ◽  
Silty Clay ◽  
Intensity Attenuation ◽  
Medium Model ◽  
Breakage Mechanics

This paper attempts to simulate the stress-strain relations of Pontida silty clay under triaxial tests in accordance with the latest theory of geotechnical nonlinear deformation analysis-breakage mechanics of geomaterials. The result proves that the binary medium model of over-consolidated clayey soil can effectively reflect the deformation mechanism of soil mass and the brittle break phenomenon, thus possessing good suitability and effectiveness. This also lays down the foundation and provides new ways for the further discussion of establishing the elastic-plastic constitutive model of clayey soil softening properties and intensity attenuation effects with the consideration of large shear displacement.

Soil parameters for deformation analysis of sand masses

1987 ◽  
Vol 24 (3) ◽  
pp. 366-376 ◽  
Author(s):  
P. M. Byrne ◽  
H. Cheung ◽  
L. Yan
Keyword(s):  
Relative Density ◽  
Back Analysis ◽  
Field Measurements ◽  
Monotonic Loading ◽  
Triaxial Tests ◽  
Deformation Analysis ◽  
Repeated Loading ◽  
Soil Parameters ◽  
Stress Strain ◽  
Tangent Stiffness

Meaningful stress and deformation analysis of soil structures requires an adequate stress–strain law. Herein are presented guidelines for selection of parameters for a simple incremental hyperbolic stress–strain law for sand based upon a tangent stiffness that varies with stress level. The parameters are obtained from an examination of laboratory and field measurements available in the literature, and are presented in terms of both penetration value and relative density. The laboratory results indicate the importance of first-time or primary loading versus repeated loading on modulus values. Back analysis of field observations for monotonic loading conditions indicates that primary loading modulus values obtained from triaxial tests are appropriate at low relative density, whereas perhaps higher values, in the repeated loading range, are appropriate at high relative densities. Key words: sand, deformation, analysis, hyperbolic, tangent stiffness, modulus, relative density, monotonic loading, repeated loading.

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.

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