scholarly journals Macroscopic stress-strain response and strain localization behavior of biopolymer-treated soil

2021 ◽  
Author(s):  
Antonio Soldo ◽  
Marta Miletic ◽  
Victor Aguilar
Keyword(s):  
Digital Image ◽  
Strain Localization ◽  
Engineering Properties ◽  
Triaxial Tests ◽  
Engineering Practice ◽  
Strain Response ◽  
Unconfined Compression ◽  
Stress Strain ◽  
Treated Soil ◽  
Macroscopic Stress

Abstract Enhancement of soil engineering properties with biopolymers has been shown recently as a viable and environmentally benign alternative to cement and chemical stabilization. Interest in biopolymer-treated soil is evident from the upsurge of related research activities in the last five years, most of which have been of experimental nature. However, biopolymers have not yet found their way into engineering practice. One of the reasons for this may be the absence of computational models that would allow engineers to incorporate biopolymer-treated soil into their designs. Therefore, the main goal of this study is to numerically capture a macroscopic stress-strain response and investigate the effect of biopolymers on the onset of strain localization. Several diagnostic strain localization analyses were conducted, thus providing strain and stress levels at the onset of strain localization, along with the orientations of the deformation band. Several unconfined compression and triaxial tests on the plain and biopolymer-treated soils were modeled. Results showed that biopolymers significantly improved the mechanical behavior of the soil and affected the onset of strain localization. The numerical results were confirmed by the digital image analysis of the unconfined compression tests. Digital image processing successfully captured high strain concentrations, which tend to occur close to the peak stress.

scholarly journals Strain localization and crack formation effects on stress-strain response of ductile iron

2017 ◽  
Vol 702 ◽  
pp. 265-271 ◽  
Author(s):  
Keivan A. Kasvayee ◽  
Ehsan Ghassemali ◽  
Kent Salomonsson ◽  
S. Sujakhu ◽  
S. Castagne ◽  
...  
Keyword(s):  
Strain Localization ◽  
Ductile Iron ◽  
Crack Formation ◽  
Strain Response ◽  
Stress Strain

Local Stress-Strain Response of an Axial X100 Girth Weld Under Tensile Loading Using Digital Image Correlation

2006 ◽  
Author(s):  
Samer Adeeb ◽  
Dave Horsley ◽  
Junhui Yan ◽  
Michael A. Sutton ◽  
Anthony P. Reynolds
Keyword(s):  
Digital Image Correlation ◽  
Digital Image ◽  
Thermal Cycle ◽  
Strain Aging ◽  
Welding Process ◽  
Tensile Tests ◽  
Image Correlation ◽  
Strain Response ◽  
Stress Strain ◽  
Dic Technique

An important design, construction and maintenance concern for pipelines is the integrity of flaws in the girth welds. Numerous fitness for purpose codes are available to assess weld flaws, many of which were calibrated with reference to wide plate test data. Often, wide plate tests are conducted on girth welded pipe in the as-received condition, i.e. without application of a pipeline coating. The area adjacent to the weld is thus subjected to a thermal cycle due to the heat generated from the welding process. In some pipe materials this thermal cycle might be sufficient to induce strain aging. It is not clear how the welding process changes the behaviour of the area next to the weld. The results of such wide plate experiments are very important in assessing the acceptable flaws in a girth weld under a strain-based design. Therefore, it was important to understand the extent of the aging, specifically the stress-strain behaviour on either side of the girth weld. This paper presents results of cross-weld tensile tests, which utilized a two-dimensional digital image correlation (DIC) technique to determine displacement, and thus infer strain. The local strains were mapped to global stress to obtain local constitutive properties every 12.5mm along the length of the specimen. The DIC test results were very consistent and were also similar to results obtained from standard circumferential tensile tests at corresponding locations. The strength of the specimens, as defined by the relative strength of their stress-strain curves, was found to be highest in the girth weld region, to drop in the HAZ, and then to reach a plateau in the base metal. It was also shown that strain localization in one of the HAZ regions was clearly visible during the loading process and the near-HAZ regions had a stress-strain response with a yield stress value higher than the base metal. This behaviour was observed at 12.5mm away from the girth-weld centerline in both the transverse and longitudinal directions. The reason for this slight change of behaviour can be attributed to the effect of heating supplied to this part during welding (strain aging). The described DIC technique is very promising in obtaining local strain fields within very small areas of the tested specimens.

Elastoplastic Simulation of Stress–Strain Response Considering the Cyclic Degradation of Saturated Clay

2018 ◽  
Vol 140 (4) ◽  
Author(s):  
Haihui Yao ◽  
Jianhua Wang
Keyword(s):  
Kinematic Hardening ◽  
Triaxial Tests ◽  
Surface Model ◽  
Strain Response ◽  
Bounding Surface ◽  
Stress Strain ◽  
Modified Model ◽  
Saturated Clay ◽  
Cyclic Degradation ◽  
Hardening Rules

A modified anisotropic bounding surface model is developed to simulate the stress–strain response of saturated clay under cyclic loading. In this study, kinematic hardening variables are introduced into the equation for a rotational bounding surface, and an anisotropic bounding surface equation is established by strict mathematical derivation from the isotropic and kinematic hardening rules. To characterize the cyclic degeneration behavior of soil stiffness, the accumulated deviatoric plastic strain is incorporated into the plastic modulus interpolation function. This modified model is then validated by comparison to results of undrained cyclic triaxial tests of isotropic and anisotropic consolidated clay samples from the literature. The results show that the performance of the modified model is an improvement over the original model for simulating the hysteresis, accumulation, and cyclic degeneration of stress–strain response.

scholarly journals Estimating the rock mass modulus of Missouri shale using pressuremeter tests

2017 ◽  
Author(s):  
◽  
Cassidy Mathews
Keyword(s):  
Rock Mass ◽  
Field Tests ◽  
In Situ Stress ◽  
Triaxial Tests ◽  
Strain Response ◽  
Stress Strain ◽  
Intact Specimen ◽  
Laboratory Test Results ◽  
Rock Mass Modulus

Rock mass modulus can be a useful property in the design of foundations. Rock mass modulus is defined as the stress strain response of a rock mass in-situ. The stress strain response of the rock mass can be estimated by directly measuring the stress strain relationship via in-situ field tests, such as the pressuremeter, or it can be estimated from the results of laboratory intact specimen tests. Intact laboratory test results are often reduced to account for imperfections or discontinuities and other properties of the rock mass that may be present in the entire system, but are not easily replicated in the lab. The rock mass modulus can be used to design piles, drilled shafts and shallow foundations that are typically employed on Missouri Department of Transportation projects. Most current methods of estimating this modulus requires coring and sampling the material, transporting samples back to a lab with appropriate equipment, extruding and preparing samples and finally performing triaxial tests and estimating the modulus from the resulting stress strain curves. Shale formations found in Missouri are typically sensitive to changes in moisture content and disturbance from sampling and sample preparation. Generally lab tests are only performed on samples that can withstand the disturbances associated with sampling and preparation. Therefore lab tests generally yield values of intact modulus and the insitu rock mass modulus must be estimated or implied from these results. The pressuremeter test (PMT) offers a potentially better method to assess the in-situ rock mass modulus. The PMT allows testing of difficult to sample materials, e.g., shale, under in-situ stress and structure conditions resulting in a modulus more representative of the shale mass. Pressuremeter tests were performed at five sites in Missouri and the results were reduced to yield rock mass modulus. Intact samples of shale recovered from each site and returned to the laboratory for unconsolidated undrained and unconfined triaxial tests to yield intact modulus values. In general, the modulii from the intact specimens were equal to or less than the in-situ modulii measured using the pressuremeter. In these practical cases, the modulii from the intact specimens did not require any reduction to provide rock mass modulus. Rather, the modulii from the intact specimens could be used directly as the rock mass modulii. This result is surprising, but not unheard of.

scholarly journals Effect of Calcium Chloride on Geotechnical Properties of Black Cotton Soil Ramya

2018 ◽  
Vol 2 (1) ◽  
Keyword(s):  
Calcium Chloride ◽  
Liquid Limit ◽  
Geotechnical Properties ◽  
Engineering Properties ◽  
Black Cotton Soil ◽  
Dry Density ◽  
Unconfined Compression ◽  
Maximum Dry Density ◽  
Treated Soil ◽  
Curing Period

The objective of the present study was to understand the effect of calcium chloride on geotechnical properties of black cotton soil. Black cotton soil collected from Siraguppa taluk, Bellary. It was subjected to various concentrations of calcium chloride viz. 0.1 N, 0.5 N, 1.0 N, 2.0 N and 4.0 N. Attempt was made to understand the effect of calcium chloride on index properties and engineering properties of black cotton soil. It was observed that the values of liquid limit, plastic limit and plasticity index of the soil treated with calcium chloride was decreasing with increase in concentration. Further the treated soil was investigated for compaction test. It was observed that the maximum dry density of the soil was increasing at higher concentrations. However, no remarkable changes were observed in the values of optimum moisture content with increase in concentration of calcium chloride. The laboratory investigation was made to obtain the unconfined compression strength (UCS) of treated soil. The soil was cured for 1 day, 7, 14 and 28 days. It was observed that the values of UCS were increasing with increase in concentration at any curing period. The soil was further tested to obtain the effect of calcium chloride on permeability of treated soil. It was observed that the permeability is increasing with increase in concentrations of 0 N, 0.5 N, and 4.0 N.

Engineering Behavior of Lime-Treated Louisiana Subgrade Soil

1996 ◽  
Vol 1546 (1) ◽  
pp. 24-31 ◽  
Author(s):  
Anand J. Puppala ◽  
Louay N. Mohammad ◽  
Aaron Allen
Keyword(s):  
Moisture Content ◽  
Compression Strength ◽  
Resilient Modulus ◽  
Engineering Properties ◽  
Dry Density ◽  
Unconfined Compression Strength ◽  
Unconfined Compression ◽  
Lime Treatment ◽  
Treated Soil ◽  
Subgrade Soil

Lime stabilization is often used to treat subgrade soils when they are soft and cohesive in nature. A study was conducted to investigate the engineering behavior, including the resilient and strength behaviors, of a lime-treated subgrade soil. The lime treatment procedure was adapted from the specifications of the Louisiana Department of Transportation and Development. Silty clay, a soil often found in Louisiana subgrades, is used as a base soil. A summary of various engineering properties of a lime-treated soil from resilient modulus, unconfined compression strength, and California bearing ratio (CBR) tests conducted at five moisture content and dry density levels is provided. Tests were also performed on the raw soil without lime treatment, and these results were compared with those of tests with the lime-treated soil. The comparisons indicate that the present lime treatment method results in an increase in strength and resilient modulus properties and a decrease in plasticity characteristics and plastic strains. A regression model with three constants was used to analyze the resilient modulus test results. The model constants are presented as functions of soil properties. Resilient modulus correlations that use either CBR or unconfined compression strength, moisture content, dry density, degree of compaction, and stresses as dependent attributes are developed.

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