scholarly journals Volume Changes and Mechanical Properties of Expansive Mudstone below Canals under Wet-Dry/Wet-Dry-Freeze-Thaw Cycles

2021 ◽  
Vol 2021 ◽  
pp. 1-11
Author(s):  
Rui Zhu ◽  
Ying-hao Huang ◽  
Zhu Song ◽  
Feng Zhou
Keyword(s):  
Volume Change ◽  
Northern China ◽  
Volume Measurement ◽  
Experimental Program ◽  
Failure Strength ◽  
Test Results ◽  
Compression Tests ◽  
Volume Changes ◽  
Stress Strain ◽  
Freeze Thaw

The complex environment in northern China is the main reason for degradation of expansive mudstone below the canals, which resulted in instability and damage of canal slopes. In this study, a serial of laboratory tests was conducted to explore the volume changes and mechanical behaviors of expansive mudstone below the canals in Xinjiang. The experimental program includes wet-dry (WD) and wet-dry-freeze-thaw (WDFT) tests, volume measurement, and unconfined compression tests. The test results show that during the WD cycles, the volume changes of expansive mudstones with a higher dry range would be more significant. The freeze-thaw process in the WDFT cycles resulted in a decrease of volume change ranges when the expansive mudstones had a relatively smaller dry range and a slight increase of volume change ranges when the expansive mudstones had a relatively larger dry range. In the meantime, the stress-strain relationships of expansive mudstones with different dry ranges all presented strain softening under the cycles of WD or WDFT. The first cycle resulted in a significant decrease of failure strength. After seven WD/WDFT cycles, the failure strength of expansive mudstones with different dry ranges decreased by 37.2%∼59.1%. In addition, the freeze-thaw process in the WDFT cycles promoted the softening of the stress-strain relationships and aggravated the failure strength attenuation of expansive mudstones. Through this study, we expect to provide a preliminary basis for the construction and maintenance of expansive mudstone canals in Xinjiang.

scholarly journals Triaxial Testing of Geosynthetics Reinforced Tailings with Different Reinforced Layers

Materials ◽  
2020 ◽  
Vol 13 (8) ◽  
pp. 1943
Author(s):  
Fu Yi ◽  
Changbo Du
Keyword(s):  
Triaxial Compression ◽  
Friction Angle ◽  
Confining Pressure ◽  
Test Results ◽  
Compression Tests ◽  
Strength Index ◽  
Stress Strain ◽  
High Confining Pressure ◽  
Zhang Model ◽  
Triaxial Compression Tests

To evaluate the shear properties of geotextile-reinforced tailings, triaxial compression tests were performed on geogrids and geotextiles with zero, one, two, and four reinforced layers. The stress–strain characteristics and reinforcement effects of the reinforced tailings with different layers were analyzed. According to the test results, the geogrid stress–strain curves show hardening characteristics, whereas the geotextile stress–strain curves have strain-softening properties. With more reinforced layers, the hardening or softening characteristics become more prominent. We demonstrate that the stress–strain curves of geogrids and geotextile reinforced tailings under different reinforced layers can be fitted by the Duncan–Zhang model, which indicates that the pseudo-cohesion of shear strength index increases linearly whereas the friction angle remains primarily unchanged with the increase in reinforced layers. In addition, we observed that, although the strength of the reinforced tailings increases substantially, the reinforcement effect is more significant at a low confining pressure than at a high confining pressure. On the contrary, the triaxial specimen strength decreases with the increase in the number of reinforced layers. Our findings can provide valuable input toward the design and application of reinforced engineering.

scholarly journals Equation for the Degradation of Uniaxial Compression Stress of Concrete due to Freeze-Thaw Damage

2019 ◽  
Vol 2019 ◽  
pp. 1-8 ◽  
Author(s):  
Xiaolin Yang ◽  
Genhui Wang ◽  
Shiwu Gao ◽  
Min Song ◽  
Anqi Wang
Keyword(s):  
Concrete Strength ◽  
Damage Variable ◽  
Curved Surface ◽  
Large Temperature ◽  
Test Results ◽  
Stress Strain ◽  
Cycle Number ◽  
Freeze Thaw ◽  
Thaw Cycle ◽  
Freeze Thaw Cycle

To study the freeze-thaw damage characteristics of concrete, the uniaxial compressive tests of concrete under different number of freeze-thaw cycles were conducted, and the damage variable of freeze-thaw was obtained. The test results showed that the stress was a function of strain and freeze-thaw damage variable, and it can describe the degradation of concrete strength. Meanwhile, the equation for the stress-strain curved surface about strain and freeze-thaw damage variable was also proposed in this paper. The derivative function of the stress-strain curved surface equation with respect to strain presented the change of elastic modulus with the increase of freeze-thaw cycle number. Equation proposed in this paper can be used for predicting the concrete lifetime effectively in cold and large temperature difference regions.

scholarly journals A Stress-Strain Model for Brick Prism under Uniaxial Compression

2019 ◽  
Vol 2019 ◽  
pp. 1-10 ◽  
Author(s):  
Keun-Hyeok Yang ◽  
Yongjei Lee ◽  
Yong-Ha Hwang
Keyword(s):  
Strain Curve ◽  
Peak Stress ◽  
Test Results ◽  
Compression Tests ◽  
Stress Strain Curve ◽  
Stress Strain ◽  
Proposed Model ◽  
Relationship Model ◽  
Strain Relationship ◽  
Strain Model

This study proposes a simple and rational stress-strain relationship model applicable to brick masonry under compression. The brick prism compression tests were conducted with different mortar strengths and with constant brick strength. From the observation of the test results, shape of the stress-strain curve is assumed to be parabola. In developing the stress-strain model, the modulus of elasticity, the strain at peak stress, and the strain at 50% of the peak stress on the descending branch were formulated from regression analysis using test data. Numerical and statistical analyses were then performed to derive equations for the key parameter to determine the slopes at the ascending and descending branches of the stress-strain curve shape. The reliability of the proposed model was examined by comparisons with actual stress-strain curves obtained from the tests and the existing model. The proposed model in this study turned out to be more accurate and easier to handle than previous models so that it is expected to contribute towards the mathematical simplicity of analytical modeling.

Effect of Column Parameters on Axial Compression Behavior of Concrete-Filled FRP Tubes

2005 ◽  
Vol 8 (4) ◽  
pp. 443-449 ◽  
Author(s):  
Zhenyu Zhu ◽  
Iftekhar Ahmad ◽  
Amir Mirmiran
Keyword(s):  
Axial Compression ◽  
Experimental Program ◽  
Test Results ◽  
Compression Tests ◽  
Concrete Core ◽  
Compression Behavior ◽  
Reinforced Polymer ◽  
Dowel Action ◽  
Frp Tubes ◽  
Glass Frp

Axial compression tests have shown fiber reinforced polymer (FRP) tubes to significantly enhance both strength and ductility of concrete columns. However, most experiments and associated models typically do not account for the internal reinforcement, size effect of the column, and the end load-bearing conditions of the tube. An experimental program was undertaken to evaluate the effect of these parameters on the performance of CFFT columns. Glass FRP tubes filled with plain, steel-reinforced, and glass FRP-reinforced concrete were tested with and without end grooves, which would prevent the tube from directly bearing of the axial load. The experiments showed the dowel action of the internal reinforcement to improve the ductility of the columns by restraining the lateral dilation of concrete core. Anempirically derived confinement model, augmented with the stress-strain response of the internal reinforcement, showed close agreement with test results.

Effect of Freeze–Thaw Cycling on Stress–Strain Characteristics and Volume Change of a Till Subjected to Repetitive Loading

1971 ◽  
Vol 8 (3) ◽  
pp. 359-371 ◽  
Author(s):  
R. W. Culley
Keyword(s):  
Water Content ◽  
Volume Change ◽  
Closed System ◽  
Volume Changes ◽  
Freeze Thaw ◽  
Design Life ◽  
Repetitive Loading ◽  
Residual Strains ◽  
Lower Water Content ◽  
Water Contents

To assess benefits to be gained from increasing compaction specifications for subgrades, a laboratory program was performed to determine the effect of closed-system freeze–thaw cycling on resilient and residual strains, resilient moduli, and volume changes of till specimens that had been compacted to various densities and water contents and subjected to repetitive loading in a constant triaxial stress system.The study showed that if compaction of this soil was increased to a higher density at a lower water content, strains, modulus, and freeze–thaw effects would be improved to such an extent that a significant reduction in pavement structure would be possible. It also showed that the extent to which a reduction could be made was dependent on the ability of the subgrade to maintain the compaction density and water content throughout its design life.

scholarly journals Evaluation Effects of the Short- and Long-Term Freeze-Thaw Exposure on the Axial Behavior of Concrete-Filled Glass Fiber-Reinforced-Polymer Tubes

2013 ◽  
Vol 2013 ◽  
pp. 1-10 ◽  
Author(s):  
Hend El-Zefzafy ◽  
Hamdy M. Mohamed ◽  
Radhouane Masmoudi
Keyword(s):  
Environmental Effects ◽  
Salt Water ◽  
Fiber Reinforced Polymer ◽  
Test Results ◽  
Fiber Reinforced ◽  
Compression Tests ◽  
Freeze Thaw ◽  
Reinforced Polymer ◽  
Short And Long Term

Previous studies have demonstrated the high performance of the concrete-filled fiber-reinforced polymer (FRP) tubes (CFFTs) as a stay-in-place formwork and confining material for concrete structures. However, there are several concerns related to the behavior of CFFT as a protective jacket against harsh environmental effects. The environmental effects such as freeze-thaw cycles and deicing salt solutions may affect materials properties, which may affect the structural response of CFFT members as well. This paper presents the test results of experimental investigation on the durability of short- and long-term behaviors of CFFT members. Test variables included the effect of confining using GFRP tubes, freeze-thaw cycles exposure in salt water, and the number of freeze-thaw cycles. CFFT cylinders (150 × 300 mm) were prepared and exposed to 100 and 300 freeze-thaw cycles in salt water condition. Then, pure axial compression tests were conducted in order to evaluate the performance of specimens due to freeze-thaw exposure, by comparing the stress-strain behavior and their ultimate load capacities. Test results indicated that the confinement using CFFT technique significantly protected the concrete when subjected to freeze-thaw exposure.

Stress path effects on the strength behaviour of a layered soil

1980 ◽  
Vol 17 (4) ◽  
pp. 603-607 ◽  
Author(s):  
M. Krishna Murthy ◽  
T. S. Nagaraj ◽  
A. Sridharan
Keyword(s):  
Experimental Investigation ◽  
Effective Stress ◽  
Volume Change ◽  
Stress Path ◽  
Layered Soil ◽  
Shear Behaviour ◽  
Compression Tests ◽  
Stress Strain ◽  
Strain Behaviour ◽  
Stress Parameters

An experimental investigation dealing with the influence of stress path on the shear behaviour of a layered soil prepared in the laboratory is described. Specimens trimmed in vertical and horizontal directions have been sheared under three different stress paths in compression and extension tests. Either in compression or extension, the stress–strain behaviour of the specimens with both orientations was apparently the same, although the volume change behaviour was different. The effective stress parameters C′ and [Formula: see text]′ were found to be unique and independent of the stress path and two principal orientations. However, the values of [Formula: see text]′ in extension tests were 6–7° higher than those in compression tests.

Ultra-High-Strength Concrete-Filled FRP Tubes: Compression Tests on Square and Rectangular Columns

2013 ◽  
Vol 575-576 ◽  
pp. 239-244 ◽  
Author(s):  
Togay Ozbakkloglu
Keyword(s):  
Aspect Ratio ◽  
High Strength Concrete ◽  
High Strength ◽  
Experimental Program ◽  
Test Results ◽  
Compression Tests ◽  
Cross Sectional ◽  
Strength Concrete ◽  
Corner Radius ◽  
Frp Tubes

This paper presents the partial results of an experimental program undertaken to investigate the behavior of square and rectangular ultra-high-strength concrete (UHSC)-filled fiber reinforced polymer (FRP) tubes (UHSCFFTs) under axial compression. The effects of the amount of confinement, cross-sectional aspect ratio and corner radius were investigated experimentally through the tests of 24 concrete-filled FRP tubes (CFFTs) that were manufactured using unidirectional carbon fiber sheets and UHSC with 108 MPa average compressive strength. Test results indicate that sufficiently confined square and rectangular UHSCFFTs can exhibit highly ductile behavior. The results also indicate that HSCFFTs having tubes of low confinement effectiveness may experience a significant strength loss at the point of transition on their stress-strain curves. Examination of the test results have led to a number of important observations on the influence of corner radius and sectional aspect ratio, which are presented and discussed in the paper.

Application of Image Processing for Volume Measurement in Multistage Triaxial Tests

2014 ◽  
Vol 931-932 ◽  
pp. 501-505 ◽  
Author(s):  
Dolrerdee Hormdee ◽  
Nicha Kaikeerati ◽  
Piyoros Jirawattana
Keyword(s):  
Image Processing ◽  
Volume Change ◽  
Volume Measurement ◽  
Triaxial Tests ◽  
Volume Changes ◽  
Change Measurement ◽  
Air Volume ◽  
Volume Change Measurement ◽  
Expansion Effect ◽  
Liquid Measurement

To investigate the unsaturated soil properties, the measurement of volume change is dealt with both water and air volume changes. It cannot be defined by using only the volume of water flown in out from the specimen as saturated soil. This paper presents the volume change measurement by using image processing (IP) from the series of consolidated undrained (CU) and constant water content (CW) tests for saturated and unsaturated conditions of soil, respectively. The results, obtained between IP and the cell liquid measurement considered movement of piston and the cell expansion effect with pressure including creep, are good corresponding except the specimen has an irregular deformation.

Stress–strain behaviour of weathered weak rock in middle-sized triaxial tests

2006 ◽  
Vol 43 (10) ◽  
pp. 1096-1104 ◽  
Author(s):  
De'an Sun ◽  
Tugen Feng ◽  
Hajime Matsuoka
Keyword(s):  
Triaxial Test ◽  
Confining Pressure ◽  
Triaxial Tests ◽  
Weak Rock ◽  
Test Results ◽  
Compression Tests ◽  
Stress Strain ◽  
Strain Behaviour ◽  
Undisturbed Samples ◽  
Strain Relationship

A middle-sized triaxial test apparatus for a specimen 20 cm in height and 10 cm in diameter was developed to measure the deformation and strength of weak rock or gravel. High-quality undisturbed samples of a weathered weak rock were taken from a dam site by a core drilling method. To avoid damage to the structure of the weak rock due to saturation of specimens as a result of measuring volume change through the water change in a burette, the lateral deformation of specimens was directly measured in the unsaturated condition using three rings mounted on the specimen. Using the developed triaxial test apparatus, isotropic compression tests and consolidated–drained triaxial compression tests were performed on unsaturated or saturated undisturbed samples under confining pressures of 49, 98, 196, 392, 539, and 683 kPa. The test results show that the stress–strain relationship of the weathered weak rock under both unsaturated and saturated conditions is strongly influenced by the confining pressure when the confining pressure is less than 392 kPa, and the stress–strain behaviour becomes similar to that of normally consolidated clay when the confining pressure is greater than 392 kPa. Comparison of results of triaxial tests on unsaturated and saturated specimens shows that the saturated samples become somewhat weak. The test results also show that the bonding and stress history largely influence the stress–strain relationship at small strain levels.Key words: weathered weak rock, microstructure, undisturbed sample, deformation, strength, triaxial test, unsaturated sample.

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