Challenges to modelling heave in expansive soils

2006 ◽  
Vol 43 (12) ◽  
pp. 1249-1272 ◽  
Author(s):  
Hung Q Vu ◽  
Delwyn G Fredlund
Keyword(s):  
Numerical Modelling ◽  
Volume Change ◽  
Void Ratio ◽  
Expansive Soils ◽  
Ground Surface ◽  
Expansive Soil ◽  
Coupled Analysis ◽  
Coupled Equations ◽  
Mathematical Equations ◽  
Unsaturated Expansive Soils

There are challenges associated with the numerical modelling of unsaturated expansive soils. The challenges are primarily related to the quantification of the void ratio constitutive surface, the characterization of the void ratio constitutive surface at low stresses and (or) suction, and the solution of coupled equations with several nonlinear unsaturated soil property functions. This study suggests that the void ratio constitutive surface of an expansive soil subject to a monotonic wetting path can be estimated from volume change indices obtained from conventional laboratory tests. The constitutive surfaces for both the soil structure and the water phase can be described using mathematical equations that allow net normal stress and suction to be reduced to zero. The solutions for two typical volume change problems are presented using both a coupled approach and an uncoupled approach. The first example problem simulates water leakage from a pipe under a flexible cover. The second example problem simulates the infiltration of water at ground surface. The results of the analyses are in accordance with anticipated behaviour. The results also show that the answers from an uncoupled analysis compared well with those from a coupled analysis. It is suggested that an uncoupled analysis may be adequate for most prediction of heave problems involving unsaturated expansive soils.Key words: heave prediction, numerical modelling, expansive soil, constitutive surface, uncoupled analysis, matric suction.

scholarly journals Stabilization of Expansive Soil with Polyvinyl Alcohol and Potassium Carbonate

2019 ◽  
Vol 2019 ◽  
pp. 1-11 ◽  
Author(s):  
Fuhai Zhang ◽  
Lei Zhang ◽  
Wangxi Hong
Keyword(s):  
Polyvinyl Alcohol ◽  
Volume Change ◽  
Expansive Soils ◽  
Soil Column ◽  
Ground Surface ◽  
Expansive Soil ◽  
Thick Layer ◽  
Soil Surface ◽  
Compression Tests ◽  
Dense Microstructure

Expansive soils have great volume change potentials with water content changes, which is problematic to facilities. Great efforts have been spent on finding proper methods to stabilize expansive soils, but these stabilizers all had limitations. The Polyvinyl alcohol (PVA) and K2CO3 combination was proposed in this paper. Free swell tests, oedometric tests, unconfined compression tests, and direct shear tests were performed to investigate the effectiveness of the PVA and K2CO3 combination to control the volume change and increase the soil strength. Microstructures of the natural expansive soil and the stabilized soil were also studied with SEM photos. SEM photos showed a homogenous and dense microstructure after stabilization. In addition, a laboratory soil column model was built to study the ability of this stabilizer combination to stabilize expansive soils by directly spraying the solution on the ground surface. All these test results show that the combination of PVA and K2CO3 is able to effectively stabilize the natural expansive soil and increase the shear strength. It is possible to directly spray the stabilizer solution on the soil surface to form a relatively thick layer of the stabilized expansive soil.

scholarly journals The mechanical behavior of an expansive soil due to long-term seasonal rainfalls

2020 ◽  
Vol 195 ◽  
pp. 02019
Author(s):  
Kai LI ◽  
Liang Kong ◽  
Hossein Nowamooz ◽  
Cyrille Chazallon
Keyword(s):  
Mechanical Behavior ◽  
Expansive Soils ◽  
Expansive Soil ◽  
Direct Determination ◽  
Model Parameters ◽  
Continuous Change ◽  
Step Method ◽  
Steady Solutions ◽  
Unsaturated Expansive Soils

Expansive soils, susceptible to be affected by the environmental conditions, expand when water is added and shrink when they dry out. This continuous change in soil volume is able to cause structures built on them to move unevenly and crack. To investigate the hydro-mechanical behavior of unsaturated expansive soils, many laboratory tests on these materials have been carried on and numerous models have also been proposed with a relatively large number of parameters. In this study, a simplified model based on Zarka method has been developed for unsaturated expansive soils. The direct determination of the steady solutions in Zarka analysis is able to replace classic step-by-step method and needs less model parameters. In this context, this paper presents a Zarka-based model to predict the volume change in unsaturated expansive soils under seasonal drought and rainfall cycles and the proposed model is implemented in the finite element code to simulate long-term behavior of a 2D structure consisting of expansive soils and subjected to successive drought and rainfall cycles. Finally, the numerical calculation defines the plastic strain field and the inelastic displacement field of the studied structure.

scholarly journals Development of Some Novel Suction-Based Correlations for Swell Behavior of Expansive Soils

2021 ◽  
Vol 2021 ◽  
pp. 1-13
Author(s):  
Bakht Zamin ◽  
Hassan Nasir ◽  
Khalid Mehmood ◽  
Qaiser Iqbal ◽  
M. Tariq Bashir ◽  
...  
Keyword(s):  
Pore Water Pressure ◽  
Expansive Soils ◽  
Water Pressure ◽  
Expansive Soil ◽  
Field Testing ◽  
Published Data ◽  
The Novel ◽  
Field Instrumentation ◽  
Swell Potential ◽  
Unsaturated Expansive Soils

Swelling and shrinkage are the two distinctive characteristics of expansive soils, and due to this behavior, these soils are considered a natural hazard for infrastructure. Many structures in different regions have been impaired due to the swell/shrink behavior of the expansive soil. Most of the severe distress is impeded because of the inherent suction (negative pore water pressure) present in expansive soils. Both suction and swelling parameters are greatly affected by the surrounding moisture content. Due to this feature of expansive soil, geotechnical engineers are interested in utilizing the suction-based correlations for the assessment of unsaturated expansive soils. The current investigation was carried out to develop novel correlations incorporating lab testing and field instrumentation. To fulfill the objectives, eight sites of the local expansive soil in Pakistan were selected for samples collection and field testing. Conventional odometer testing was conducted to measure the swell pressure (Sp) and swell potential (S) of the fabricated/remolded specimens. Gypsum block (G-block) sensors were additionally utilized for estimating the matric suction in the field. To expand the database, the previously published data of the same nature was also incorporated. Based on the results, the power form of the novel correlations (suction-based) is highly significant for estimating (Sp), while for swell potential, the logarithmic correlation with R2 = 0.6551 is more significant than other forms of correlations. The proposed suction-based correlation can be equally utilized for the estimation of field suction as well as for swell behavior of expansive soil having a plasticity index (PI) ≥ 22%.

scholarly journals Field-Obtained Soil-Water Characteristic Curves of KPK Expansive Soil and Their Prediction Correlations

2020 ◽  
Vol 2020 ◽  
pp. 1-13
Author(s):  
Bakht Zamin ◽  
Hassan Nasir ◽  
Khalid Mehmood ◽  
Qaiser Iqbal
Keyword(s):  
Moisture Content ◽  
Soil Water ◽  
Expansive Soils ◽  
Characteristic Curve ◽  
Ground Surface ◽  
Expansive Soil ◽  
Absorption Capacity ◽  
Water Retention Curve ◽  
Swell Index ◽  
Testing Field

Expansive clays are found worldwide in arid and semiarid regions. Such soils are considered a natural hazard for civil engineering infrastructures especially when they are lightly loaded. Expansive soils are often unsaturated due to the high absorption capacity of moisture. The damaging effect of expansive soils is intimately related to the distinctive soil-water characteristic in the surficial soil layers subjected to wetting-drying cycles. The soil-water characteristic curve (SWCC) also known as the water-retention curve shows the fluctuation of suction with the moisture content. It is one of the key parameters that have been developed and used by soil engineers for studying the properties of partially saturated soils. Currently, the SWCCs produced by most of the researchers are grounded on lab testing which is quite different from the field-obtained curves. In the current study, the SWCCs for Karak expansive soil have been obtained from in situ testing (field). For this purpose, three sites were selected at Amberi Village (Karak) for instrumentation. An open trench of six-foot depth was excavated in each site and instrumented. Electrical resistivity sensors (G-blocks) and tensiometers were used for matric suction measurements. The gravimetric moisture content was measured with the help of moisture sensors calibrated with a speedy moisture meter. To check the fluctuation of moisture and suction, these instruments were installed at three different depths, that is, 0–2, 2–4, and 4–6 feet. Based on results, the maximum suction of 705.79 kPa was observed in the site “A” in 0–2-foot depth (near the ground surface) with a moisture content of 15 percent. The variations in suction and moisture content follow the almost same trend at low suction; however, the trend was slightly different at the moderate suction range. The measured suction showed a strong correlation with the free swell index (FSI) and moisture content. It was found that the upper layers of expansive soil have high suction than lower layers due to more exposure to the environmental agencies and low density.

scholarly journals Modification of Mechanical Properties of Expansive Soil from North China by Using Rice Husk Ash

Materials ◽  
2021 ◽  
Vol 14 (11) ◽  
pp. 2789
Author(s):  
Mazahir M. M. Taha ◽  
Cheng-Pei Feng ◽  
Sara H. S. Ahmed
Keyword(s):  
Hydraulic Conductivity ◽  
Rice Husk ◽  
North China ◽  
Void Ratio ◽  
Rice Husk Ash ◽  
Clay Soil ◽  
Expansive Soils ◽  
Expansive Soil ◽  
Coefficient Of Consolidation ◽  
Consolidation Coefficient

The construction of buildings on expansive soils poses considerable risk of damage or collapse due to soil shrinkage or swelling made likely by the remarkable degree compressibility and weak shear resistance of such soils. In this research, rice husk ash (RHA) was added to expansive soil samples in different quantities of 0%, 4%, 8%, 12%, and 16% by weight of soil to determine their effects on the plasticity index, compaction parameters, consolidation performance, and California bearing ratio (CBR)of clay soil. The results show that the use of RHA increases the effective stress and decreases the void ratio and coefficient of consolidation. Adding 16% RHA resulted in the greatest reduction in the hydraulic conductivity, void ratio, and coefficient of consolidation. The void ratio decreased from 0.96 to 0.93, consolidation coefficient decreased from 2.52 to 2.33 cm2/s, and hydraulic conductivity decreased from 1.12 to 0.80 cm/s. The addition of RHA improved the soil properties and coefficient of consolidation due to the high density and cohesiveness of RHA. The results of this study can be used to provide a suitable basis for the treatment of expansive soil to provide improved conditions for infrastructure construction.

Model for the simulation of swelling-pressure measurements on expansive soils

1998 ◽  
Vol 35 (1) ◽  
pp. 96-114 ◽  
Author(s):  
Fangsheng Shuai ◽  
D G Fredlund
Keyword(s):  
Pore Water ◽  
Volume Change ◽  
Unsaturated Soil ◽  
Pore Water Pressure ◽  
Expansive Soils ◽  
Water Pressure ◽  
Expansive Soil ◽  
Swelling Pressure ◽  
Oedometer Test ◽  
Free Swell

Numerous laboratory swelling tests have been reported for the measurement of swelling pressure and the amount of swell of an expansive soil. These test methods generally involve the use of a conventional one-dimensional oedometer apparatus. Few attempts, however, have been made to formulate a theoretical framework to simulate the testing procedures or to visualize the different stress paths followed when using the various methods. The simulation of the oedometer tests on expansive soils is required to fully understand the prediction of heave. The correct measurement of swelling pressure is required for an accurate prediction of heave. It is further anticipated that some information on unsaturated soils property functions may be approximated from the back-analysis of the data. A theoretical model is proposed to describe the pore-water pressures with time and depth in a specimen as well as the volume changes during various oedometer swell tests. The model is formulated based on equilibrium considerations, constitutive equations for an unsaturated soil, and the continuity requirement for the pore fluid phases. The transient water flow process is coupled with the soil volume change process. The model can be used to describe the volume-change behaviour, pore-water pressure, and vertical total stress development in an unsaturated soil during an oedometer test performed by any one of several test procedures. The model has been put into a finite element formulation using the Galerkin technique. All the parameters required to run the model can be obtained by performing independent, common laboratory tests. The proposed model was used to simulate the results from free-swell, constant-volume, constant water content, and loaded-swell oedometer tests. Computed values of volume change, vertical total stress, and pore-water pressure are in good agreement with measured values.Key words: unsaturated soil, expansive soil, swelling pressure, theoretical simulation, constant-volume oedometer test, free-swell oedometer test, loaded-swell oedometer test.

scholarly journals A Framework for Interpreting Lateral Swelling Pressure in Unsaturated Expansive Soils

2021 ◽  
Vol 2021 ◽  
pp. 1-15
Author(s):  
Mingyu Li ◽  
Yanqing Wei ◽  
Yunlong Liu ◽  
Junwei Jin
Keyword(s):  
Expansive Soils ◽  
Soil Mechanics ◽  
Expansive Soil ◽  
Swelling Pressure ◽  
Field Studies ◽  
Theoretical Framework ◽  
Water Infiltration ◽  
Civil Infrastructure ◽  
Unsaturated Soil Mechanics ◽  
Unsaturated Expansive Soils

Lateral swelling pressure (LSP) develops when expansive soil volume increment associated with water infiltration is restrained in a confined domain, for example, due to construction of civil infrastructure. In this paper, initially a flowchart is developed to highlight various key factors that influence the LSP mobilization according to lab and field studies collected from previous literature studies. Then extending unsaturated soil mechanics, a theoretical framework is proposed for illustrating the LSP mobilization in the field against retaining structures and pile foundations under different boundary conditions, respectively. An example problem for a basement wall and a pile foundation constructed in a typical expansive soil from Regina, Canada, is presented to illustrate the proposed theoretical framework. The framework and corresponding analysis presented in this paper can facilitate to provide rational designs of geotechnical infrastructures in expansive soils.

scholarly journals Sustainability Benefits Assessment of Metakaolin-Based Geopolymer Treatment of High Plasticity Clay

2020 ◽  
Vol 12 (24) ◽  
pp. 10495
Author(s):  
Rinu Samuel ◽  
Anand J. Puppala ◽  
Miladin Radovic
Keyword(s):  
Volume Change ◽  
Expansive Soils ◽  
Expansive Soil ◽  
High Plasticity ◽  
Lime Treatment ◽  
Chemical Additives ◽  
Ambient Temperatures ◽  
New Class ◽  
Stiffness Characteristics ◽  
Strength And Stiffness

Expansive soils are prevalent world over and cause significant hazards and monetary losses due to infrastructure damages caused by their swelling and shrinking behavior. Expansive soils have been conventionally treated using chemical additives such as lime and cement, which are known to significantly improve their strength and volume-change properties. The production of lime and cement is one of the highest contributors of greenhouse gas emissions worldwide, because of their energy-intensive manufacturing processes. Hence, there is a pressing need for sustainable alternative chemical binders. Geopolymers are a relatively new class of aluminosilicate polymers that can be synthesized from industrial by-products at ambient temperatures. Geopolymer-treated soils are known to have comparable strength and stiffness characteristics of lime and cement-treated soils. This study evaluates the sustainability benefits of a metakaolin-based geopolymer treatment for an expansive soil and compares its results with lime treatment. Test results have shown that geopolymers have significantly improved strength, stiffness, and volume-change properties of expansive soils. Increased dosages and curing periods have resulted in further property enhancements. Swell and shrinkage studies also indicated reductions in these strains when compared to control conditions. The sustainability benefits of both geopolymer and lime treatment methods are evaluated using a framework that incorporates resource consumption, environmental, and socio-economic concerns. This study demonstrates geopolymer treatment of expansive soils as a more sustainable alternative for expansive soil treatments, primarily due to metakaolin source material. Overall results indicated that geopolymers can be viable additives or co-additives for chemical stabilization of problematic expansive soils.

scholarly journals A Comparative Laboratory Investigation into the Role of Geosynthetics in the Initial Swell Control of an Expansive Soil

2019 ◽  
Vol 29 (4) ◽  
pp. 18-40
Author(s):  
Jijo James ◽  
Sivapriya Vijayasimhan ◽  
Hemavathi Srinivasan ◽  
Jayasri Arulselvan ◽  
Sathya Purushothaman ◽  
...  
Keyword(s):  
Laboratory Investigation ◽  
Volume Change ◽  
Expansive Soils ◽  
Expansive Soil ◽  
Virgin Soil ◽  
Number Of Layers ◽  
Material Orientation ◽  
Effective Role

Abstract Volume change in expansive soils due to the intervention of water causes swell. A laboratory investigation using two different gbeosynthetic materials was designed to minimise the swell characteristics. The influence of three parameters, being geosynthetic material [Secutex (ST) and Combigrid (CG)], orientation (horizontal and vertical), and number of layers (1, 2, and 3) on the swell of an expansive soil was studied to better understand the potential for geosynthetics in swell control. The study on the immediate swell characteristics (limited to 24 hours) helps in gaining confidence in the use of geosynthetics in the swell control of expansive soils. From the investigation results, it was found that all three parameters, being type of material, orientation, and number of layers influenced the swell control of the soil. When two layers of ST and CG were placed both vertically and crossed, they reduced the swell of the virgin soil by almost 60% and 44%, respectively. It can, therefore, be concluded that geosynthetics can play an effective role in the swell control of expansive soils.

scholarly journals Swelling Potential of Clayey Soil Modified with Rice Husk Ash Activated by Calcination for Pavement Underlay by Plasticity Index Method (PIM)

2021 ◽  
Vol 2021 ◽  
pp. 1-10
Author(s):  
Kennedy C. Onyelowe ◽  
Michael E. Onyia ◽  
Diu Nguyen-Thi ◽  
Duc Bui Van ◽  
Eze Onukwugha ◽  
...  
Keyword(s):  
Rice Husk ◽  
Volume Change ◽  
Rice Husk Ash ◽  
Clayey Soil ◽  
Expansive Soils ◽  
Expansive Soil ◽  
Clay Content ◽  
Hydrated Lime ◽  
Plasticity Index ◽  
Index Method

Volume change in expansive soils is a problem encountered in earth work around the world. This is prominent with hydraulically bound structures or foundations subjected to prolonged moisture exposure. This behavior of clayey used as subgrade, foundation, landfill, or backfill materials causes undesirable structural functionality and failures. To prevent this happening, clayey soils are studied for possible volume change potential and degree of expansion. Consequently, the problematic soils are stabilized. In this work, the stabilization of clayey highly expansive soil classified as A-7-6 soil and highly plastic with high clay content was conducted under laboratory conditions. The treatment exercise was experimented using quicklime-activated rice husk ash (QARHA), hydrated lime-activated rice husk ash (HARHA), and calcite-activated rice husk ash (CARHA) at the rates of 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, and 10%. Upon treatment with the three calcium compounds to produce three sets of treated experimental specimens, the plasticity index was observed and recorded and swelling potentials were evaluated using the plasticity index method (PIM). The results showed a consistent improvement on the properties of the treated soil with the addition of the different activated admixtures. While the utilization of CARHA and HARHA improved the clayey soil to medium expansive soil, the treated clayey soil substantially improved from highly expansive soil with a potential of 23.35% to less expansive with a final potential of 0.59% upon the addition of 10% QARHA. Finally, QARHA was adjudged as the best binding composite due to the highest rate of reduction recorded with its utilization.

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