scholarly journals Work input analysis for soils with double porosity and application to the hydromechanical modeling of unsaturated expansive clays

2017 ◽  
Vol 54 (2) ◽  
pp. 173-187 ◽  
Author(s):  
Jian Li ◽  
Zhen-Yu Yin ◽  
Yujun Cui ◽  
Pierre-Yves Hicher
Keyword(s):  
Mechanical Behavior ◽  
Expansive Soils ◽  
Volumetric Strain ◽  
Double Porosity ◽  
Strain Increment ◽  
Degree Of Saturation ◽  
Triaxial Tests ◽  
Expansive Clay ◽  
Expansive Clays ◽  
Boom Clay

A mechanical approach for unsaturated expansive soils considering double porosity has been developed based on the porous media theory. In this approach, the adsorbed and the capillary water, as well as the micropores and macropores, are two distinct phases. An interaggregate stress considered as the work-conjugate of the macrostructural strain increment has been defined. Both physicochemical and capillary effects of the pore water have been introduced at the macroscopic level. Other work-conjugate variables relevant for the constitutive modeling of double-porosity unsaturated media have also been identified, consisting of the modified suction as conjugate of the increment of the macrostructural degree of saturation and the microstructural effective stress as conjugate of the microstructural volumetric strain increment. A hydromechanical model for unsaturated expansive clays taking into account the interaction between the micro- and the macrostructures in expansive clays can thus be built. Based on the bounding surface concept, an anisotropic loading – collapse yield surface has been introduced to reproduce the three-dimensional mechanical behavior. To analyze the model capabilities, two series of laboratory tests consisting of multiple wetting and drying cycle tests on Boom clay and triaxial tests on Zaoyang (ZY) expansive clay were simulated. The comparisons between numerical and experimental results show that the model can reproduce with reasonable accuracy the mechanical behavior and the water retention characteristic of unsaturated expansive clays.

scholarly journals Experimental Study on Mechanical Behavior of Lean Cemented Sand and Gravel Material in Unloading and Reloading Paths

2021 ◽  
Vol 2021 ◽  
pp. 1-12
Author(s):  
Jie Yang ◽  
An-yu Yang ◽  
Yan-gong Shan ◽  
Miao-miao Yang ◽  
Jin-lei Zhao ◽  
...  
Keyword(s):  
Mechanical Behavior ◽  
Hysteresis Loop ◽  
Triaxial Test ◽  
Volumetric Strain ◽  
Rate Of Change ◽  
Coarse Grained ◽  
Triaxial Tests ◽  
Water Drainage ◽  
Cemented Sand ◽  
Sand And Gravel

Lean cemented sand and gravel (LCSG) materials are subjected to unloading-loading when an LCSG dam is opened for water drainage and then refilled or a roadbed base is subjected to repeated wheel loads. To investigate the behavior of the LCSG materials under loading-unloading, previous studies utilized the complete loading triaxial test. In contrast, in this study, the consolidated drained triaxial tests in the unloading and reloading paths for materials with cementing agent contents of 60 and 100 kg/m3 under different confining pressures, for which each curve generates three loading-unloading cycles, were applied to investigate the unloading and reloading mechanical behavior. Experimental results indicated that the unloading and reloading behavior of the LCSG materials produced stress-strain curves exhibiting a crescent-shaped hysteresis loop, which differs from that exhibited by coarse-grained soil. Although the shape of the crescent-like hysteresis loop was preserved as stress levels increasing, it gradually expanded. Compared with that of the typical triaxial test, the cohesive force and the increasing internal friction angle increased. Further, as the confining pressure increased, the crescent-like hysteresis loops tapered, shear strength increased linearly, and the modulus of resilience increased nonlinearly; the latter’s rate of change, however, decreased. The change in volumetric strain was small during unloading as the stress level changed.

Hydromechanical behaviour of expansive soils with different suctions and suction histories

2016 ◽  
Vol 53 (1) ◽  
pp. 1-13 ◽  
Author(s):  
Junran Zhang ◽  
De’an Sun ◽  
Annan Zhou ◽  
Tong Jiang
Keyword(s):  
Expansive Soils ◽  
Volumetric Strain ◽  
Expansive Soil ◽  
Experimental Results ◽  
Triaxial Tests ◽  
Test Results ◽  
Soil Water Retention ◽  
Suction Control ◽  
Vapor Equilibrium ◽  
High Suction

This paper presents a number of experimental results of suction-controlled triaxial tests on a compacted weakly expansive soil with different suctions and suction histories. In terms of suction control methods, the high suction level (from 3.29 to 38 MPa) was realized by the vapor equilibrium technique and the low suction level (from 0 to 800 kPa) was controlled by the axis translation technique. Results of the triaxial tests indicate that the specimen with higher suction shows higher strength and lower contractive and higher dilative volumetric strains, and the average skeleton stress ratio (q/p′) at failure decreases with increasing suction in the high suction range (3.29∼38 MPa). Given that suction during shearing is constant (e.g., 200 kPa), the specimen dried to a higher suction and the history shows higher strength and lower contractive volumetric strain. Experimental results also show that high pre-applied suction (i.e., the maximum suction in the history) can lead to peak strength, post-peak softening, and shear dilation. Three different methods (pressure plate, filter paper, and vapor equilibrium) were employed to study the soil-water retention behaviour of the unsaturated expansive soil. Test results indicate that by combining these three different methods, it is possible to determine the SWCC in the entire suction range (0∼367 MPa). Test results of the expansive soil also show that the void ratio keeps decreasing with increasing suction in the entire suction range.

scholarly journals A water retention model accounting for void ratio changes in double porosity clays

2021 ◽  
Author(s):  
Gema De la Morena ◽  
Vicente Navarro ◽  
Laura Asensio ◽  
Domenico Gallipoli
Keyword(s):  
Water Retention ◽  
Double Porosity ◽  
Degree Of Saturation ◽  
Retention Model ◽  
Boom Clay ◽  
Retention Behaviour ◽  
Pore Size Distributions ◽  
New Formulation ◽  
Clay Aggregates ◽  
Porosity Model

AbstractThis paper presents a constitutive model that predicts the water retention behaviour of compacted clays with evolving bimodal pore size distributions. In line with previous research, the model differentiates between the water present inside the saturated pores of the clay aggregates (the microstructure) and the water present inside the pores between clay aggregates (the macrostructure). A new formulation is then introduced to account for the effect of the macrostructural porosity changes on the retention behaviour of the soil, which results in a consistent evolution of the air-entry value of suction with volumetric deformations. Data from wetting tests on three different active clays (i.e. MX-80 bentonite, FEBEX bentonite, and Boom clay), subjected to distinct mechanical restraints, were used to formulate, calibrate, and validate the proposed model. Results from free swelling tests were also modelled by using both the proposed double porosity model and a published single porosity model, which confirmed the improvement in the predictions of degree of saturation by the present approach. The proposed retention model might be applied, for example, to the simulation of the hydromechanical behaviour of engineered bentonite barriers in underground nuclear waste repositories, where compacted active clays are subjected to changes of both suction and porosity structure under restrained volume conditions.

scholarly journals Effect of Iron Chloride on the Strength Behaviour of the Expansive Clay

2018 ◽  
Vol 9 (1) ◽  
pp. 6730-6733
Keyword(s):  
Calcium Chloride ◽  
Civil Engineering ◽  
Expansive Soils ◽  
Expansive Soil ◽  
Iron Chloride ◽  
Black Cotton Soil ◽  
Expansive Clay ◽  
Expansive Clays ◽  
Shrinkage And Swelling ◽  
Strong Electrolytes

From the fast few decades, several techniques were introduced inorder to modify the behaviour of expansive clays. The use of strong electrolytes like calcium chloride (CaCl2 ), aluminum trichloride (AlCl3 ) and iron chloride (FeCl3 ) were extensively used in various civil engineering applications. Expansive soils possesses alternate shrinkage and swelling with the removal and addition of water from it. Iron chloride was effectively used to alter the swelling and shrinkage and also improve the engineering behaviour of expansive clays. Therefore, in the current work an effort is made for study the influence of iron chloride (FeCl3 ) on the strength behaviour of the expansive soil. The outcomes from the laboratory investigation proved that the usage of iron chloride (FeCl3 ) produce reduction in swelling and improvement in the strength. It was found that 1% FeCl3 be the optimum for both the UCS and CBR. Hence, from the investigation it was showed that iron chloride is a valuable stabilizer to enhance the properties of black cotton soil and to create it apt for various applications of Civil Engineering.

scholarly journals Creep Properties of Expansive Soils under Triaxial Drained Conditions and its Nonlinear Constitutive Model

2021 ◽  
Author(s):  
Jingjing Li ◽  
Lingwei Kong
Keyword(s):  
Expansive Soils ◽  
Creep Property ◽  
Volumetric Strain ◽  
Failure Stress ◽  
Creep Model ◽  
Creep Process ◽  
Triaxial Tests ◽  
Nonlinear Creep ◽  
Deviator Stress ◽  
Accelerated Creep

The creep behaviors of expansive soils play an important role in landslide prediction and long-term stability analysis. In this paper, triaxial drained compression creep tests of expansive soils were conducted on the improved stress-controlled triaxial apparatus. The test results show that only transient deformation and attenuation creep occur with low deviator stress, and the increment of axial strain increases exponentially with deviator stress increasing; while deviator stress reaches a certain value, attenuation creep, steady creep and accelerated creep all occur in a creep curve. Meanwhile, the volumetric strain presents the shear shrinkage characteristic at the initial stage of loading, and the shear shrinkage is small. With the extension of loading time, the volumetric strain gradually varies from shear contraction to dilatancy. When entering the accelerated creep stage, the development rate of volumetric strain increases sharply. Besides, isochronous stress-strain curves of expansive soils indicate that their creep process possesses nonlinear characteristics, and the nonlinear degree is related to creep time and stress level. Imitating the empirical formula of cyclic cumulative deformation of clay, a new nonlinear creep model is presented, which may well describe the creep property of expansive soils. Furthermore, critical failure stress could be obtained based on the proposed creep model. The ratio of the critical failure stress to conventional shear failure stress ranges from 70% to 80%, with average of 75.56%, therefore, critical failure stress may be estimated by conventional triaxial tests with the margin of error 5.5% within.

scholarly journals An estimation of the soil water characteristics curves of Trinidad's expansive clays

2020 ◽  
Vol 195 ◽  
pp. 03009
Author(s):  
Damian V A Alexander ◽  
Kyung Ho Park ◽  
Derek Anthony Gay
Keyword(s):  
Water Content ◽  
Soil Water ◽  
Volume Change ◽  
Characteristic Curve ◽  
Degree Of Saturation ◽  
Expansive Clay ◽  
Contributing Factors ◽  
Wet Season ◽  
Potential Measurement ◽  
Expansive Clays

Volume change behaviour of expansive clays has been one of the leading causes of damage to civil infrastructures worldwide. Contributing factors that lead to failures relate to changes in water content within the soil. Variations of water content can vary significantly based on an area’s climate regime. Trinidad has two seasons, the dry season (January to June) and the wet season (July to December). This variation leads to volume changes of expansive clay, where they exist mainly within the central and south regions of Trinidad. These areas are densely populated by residential and commercial buildings, which can be susceptible to damages from unsaturated expansive clays. The Soil Water Characteristic Curve (SWCC) for expansive clays is critical to estimate their unsaturated properties for the analysis of water flow movement. This study investigates the SWCCs for two expansive clay soil types in Trinidad. A WP4-T (Water Potential Measurement) is used to measure soil suction. The shrinkage curve (SC) test is conducted to consider the volume change of soil. The Fredlund and Xing (1994) SWCC equation and Fredlund and Zhang (2013) SC equation are used to fit the measured data. The SWCCs in terms of gravimetric and volumetric water contents and degree of saturation are compared. It is found that the normalised degree of saturation SWCC can provide a better display of the SWCC and estimation of the air-entry value.

Hydromechanical behaviour of overconsolidated unsaturated soil in undrained conditions

2019 ◽  
Vol 56 (11) ◽  
pp. 1609-1621 ◽  
Author(s):  
Shengshen Wu ◽  
Annan Zhou ◽  
Jie Li ◽  
Jayantha Kodikara ◽  
Wen-Chieh Cheng
Keyword(s):  
Effective Stress ◽  
Unsaturated Soils ◽  
Axial Strain ◽  
Triaxial Compression ◽  
Volumetric Strain ◽  
Degree Of Saturation ◽  
Triaxial Tests ◽  
Conventional Triaxial Compression ◽  
Hydromechanical Behaviour ◽  
Undrained Conditions

Hydromechanical behaviour of an unsaturated silt with various suctions and different overconsolidated ratios (OCRs) was investigated through a series of undrained triaxial tests (constant water contents, CW). All the samples were prepared from the slurry state. Different OCRs (= 1, 2, 4, and 8 in net stress) were achieved by unloading the samples to 400, 200, 100, and 50 kPa from an initial confining net pressure of 400 kPa. Then the samples were dried to various suctions (0, 100, 200, 300, and 400 kPa). Unsaturated samples with different OCRs were then sheared at CW conditions following the conventional triaxial compression (CTC) paths. Full hydromechanical responses including the changes in deviator stress, stress ratio, volumetric strain, suction, and degree of saturation with axial strain were monitored and are presented in this paper. Some key findings include (i) the critical state for unsaturated soils with different OCRs can be well defined by Bishop’s effective stress; (ii) the peak strength in Bishop’s effective stress increases with increase of OCR, but decreases with increase of suction in the undrained condition; and (iii) the volume change of unsaturated soils in undrained conditions is related to OCRs and the volume of pore air.

Improvement of Strength and Volume-Change Properties of Expansive Clays with Geopolymer Treatment

2021 ◽  
pp. 036119812110018
Author(s):  
Rinu Samuel ◽  
Anand J. Puppala ◽  
Aritra Banerjee ◽  
Oscar Huang ◽  
Miladin Radovic ◽  
...  
Keyword(s):  
Volume Change ◽  
Carbon Dioxide Emissions ◽  
Expansive Soils ◽  
Linear Shrinkage ◽  
Plasticity Index ◽  
Specimen Preparation ◽  
Expansive Clays ◽  
Change Behavior ◽  
Volume Change Behavior ◽  
Lower Carbon

Expansive soils are conventionally treated with chemical stabilizers manufactured by energy-intensive processes that significantly contribute to carbon dioxide emissions globally. Geopolymers, which are synthesized from industrial byproducts rich in aluminosilicates, are a viable alternative to conventional treatments, as they are eco-friendly and sustainable. In this study, a metakaolin-based geopolymer was synthesized, and its effects on the strength and volume-change behavior of two native expansive soils from Texas, with a plasticity index over 20 were investigated. This paper elaborates on the geopolymerization process, synthesis of the metakaolin-based geopolymer, specimen preparation, and geopolymer treatment of soils. Comprehensive material testing revealed two clays with a plasticity index over 20. They were each treated with three dosages of the metakaolin-based geopolymer and cured in 100% relative humidity for three different curing periods. The efficiency of geopolymer treatment was determined by testing the control and geopolymer-treated soils for unconfined compressive strength (UCS), one-dimensional swell, and linear shrinkage. Field emission scanning electron microscope (FESEM) imaging was performed on the synthesized geopolymer, as well as on the control and geopolymer-treated soils, to detect microstructural changes caused by geopolymerization. A significant increase in UCS and reduction in swelling and shrinkage were observed for both geopolymer-treated soils, within a curing period of only 7 days. The FESEM imaging provided new insights on the structure of geopolymers and evidence of geopolymer formation in treated soils. In conclusion, the metakaolin-based geopolymer has strong potential as a lower-carbon-footprint alternative to conventional stabilizers for expansive soils.

scholarly journals Research of the Behavior of Clay Materials with Double Porosity

2021 ◽  
Vol 13 (6) ◽  
pp. 3219
Author(s):  
Hynek Lahuta ◽  
Luis Andrade Pais
Keyword(s):  
Double Porosity ◽  
Strength Properties ◽  
Triaxial Tests ◽  
Building Structures ◽  
Foundation Soil ◽  
Problematic Use ◽  
The North ◽  
Static Liquefaction ◽  
Confinement Stress ◽  
Clay Materials

This contribution presents results from a series of compression and undrained triaxial tests to study the mechanical behavior of dump clay from the north of Bohemia. The use of these materials as a foundation for construction can’t be achieved without the adoption of some precautions. This comes from embankment, formed by digging the ground (altered claystone), up to the level of coal mining which is in a sub horizontal stratigraphic layer. A potential static liquefaction behavior was observed in undrained tests for high confinement stress. A structural collapse was noticed with the results obtained in the triaxial test. This collapse is characterized by an unexpected large decrease in deviator and mean effective stress. The soils formed have strength properties that are potentially dangerous. These concepts can improve the use of these kinds of soils in geotechnical engineering work. It continues and expands the results obtained in previous research, especially the future problematic use of these materials as the foundation soil for line or building structures.

Influence of drainage and root biomass on soil mechanical behavior in triaxial tests

2021 ◽  
Author(s):  
Mehtab Alam ◽  
Yuan-Jun Jiang ◽  
Muhammad Umar ◽  
Li-jun Su ◽  
Mahfuzur Rahman ◽  
...  
Keyword(s):  
Mechanical Behavior ◽  
Root Biomass ◽  
Triaxial Tests
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