scholarly journals Experimental Study on Cracking Behaviour and Strength Properties of an Expansive Soil under Cyclic Wetting and Drying

2021 ◽  
Vol 2021 ◽  
pp. 1-13
Author(s):  
Tao Li ◽  
Yanqing He ◽  
Guokun Liu ◽  
Binru Li ◽  
Rui Hou
Keyword(s):  
Shear Strength ◽  
Expansive Soils ◽  
Expansive Soil ◽  
Strength Properties ◽  
Rate Of Change ◽  
Crack Development ◽  
Structural Morphology ◽  
Limit Value ◽  
Strength Change ◽  
Length Direction

Expansive soil is characterized by its unique structural morphology and drastic volume change. With infrastructure increasingly constructed in expansive soil areas, engineering problems caused by the properties of expansive soils have attracted more attention. Cyclic wetting-drying and shear testing were accordingly conducted on an expansive soil from Chengdu area in China. Crack development and shear strength change were analyzed using the Mohr–Coulomb equation for shear strength by fitting the experimental data. The results show the following: (1) With the increase in wetting-drying cycles, the crack ratio increases, the shear strength decreases, and the shear strength parameters gradually decrease at the same rate of change. The applied vertical load reduces the weakening effect of the wetting-drying cycles on the soil structure and strength by restraining the expansion and contraction deformation. (2) By analyzing the number of wetting-drying cycles and the crack images, the crack development (length, direction, etc.) of the expansive soil can be predicted and described. (3) There is a specific linear correlation between the crack ratio and strength that approached a limit value with ongoing wetting-drying cycles. The strength of the expansive soil can therefore be obtained based on crack development, improving the ability of designers to account for the behaviour of expansive soils.

DETERMINATION OF EXPANSIVE SOIL STRENGTH USING A FRACTAL MODEL

Fractals ◽  
2001 ◽  
Vol 09 (01) ◽  
pp. 51-60 ◽  
Author(s):  
YONGFU XU ◽  
DE'AN SUN
Keyword(s):  
Shear Strength ◽  
Soil Sample ◽  
Expansive Soils ◽  
Triaxial Compression ◽  
Expansive Soil ◽  
Fractal Model ◽  
Dry Density ◽  
Compression Tests ◽  
Surface Fractal ◽  
Strength Formula

The micropore surface fractal model for expansive soils is proposed in this paper. Based on the results of the mercury intrusion tests, it is found that the micropore surface fractal dimension is 2.40 for the soil sample with the dry density of 1.50 g/cm 3, and is 2.47 for the soil sample with the dry density of 1.60 g/cm 3. By using the micropore surface fractal model, the shear strength formula for expansive soils is obtained. All the parameters in the proposed shear strength formula are constant, and are independent of matric suction. The validation of the proposed shear strength formula is proven by the results of the triaxial compression tests on an expansive soil taken from Ningxia, China.

scholarly journals Characterization of the Undrained Shear Strength of Expansive Soils of High Water Content

2018 ◽  
Vol 206 ◽  
pp. 01002
Author(s):  
Zheng Su ◽  
Daokun Qi ◽  
Xinju Guo ◽  
Xiaojuan Xi ◽  
Liang Zhang
Keyword(s):  
Shear Strength ◽  
Water Content ◽  
Expansive Soils ◽  
Expansive Soil ◽  
Friction Angle ◽  
High Water ◽  
Ease Of Use ◽  
Triaxial Tests ◽  
High Water Content

In recent years, engineering constructions increase rapidly in western and central areas of China, where expansive soil widely distributes. Since expansive soil is sensitive to water content, the characterization of its shear strength should be carefully conducted. For simplicity and ease of use, the Mohr-Coulomb criterion is often adopted to describe the shear strength of expansive soil. In this paper, the physical meaning of the cohesion and frictional strength of expansive soil are explained, and the variations of the strength parameters with water content are investigated. By fitting to the experimental results from direct shear test and triaxial tests, the changing characteristics of cohesion and friction angle with water content are obtained.

Expansive Soil Treatment with Liquid Ionic Soil Stabilizer

2018 ◽  
Vol 2672 (52) ◽  
pp. 185-194 ◽  
Author(s):  
Shi He ◽  
Xinbao Yu ◽  
Aritra Banerjee ◽  
Anand J. Puppala
Keyword(s):  
Expansive Soils ◽  
Expansive Soil ◽  
Linear Shrinkage ◽  
Strength Properties ◽  
Morphological Variations ◽  
Subgrade Soils ◽  
Soil Stabilizer ◽  
Before And After ◽  
Test Soil ◽  
Shrinkage Behavior

Calcium-based stabilizers such as lime and cement control swell and shrinkage behavior and enhance strength properties for expansive soils through the formation of pozzolanic components. However, sulfate-bearing subgrade soils stabilized with calcium-based stabilizers might cause excessive swelling and shrinkage due to the formation of highly expansive minerals like ettringite and thaumasite. In this paper, one liquid ionic soil stabilizer (LISS) was evaluated as an alternative stabilizer used to control swelling and shrinkage behavior of expansive soils. A comprehensive laboratory experiment program including a linear shrinkage test, a one-dimensional swell test, and an unconfined compressive strength test, was designed and carried out on soils from Dallas, Texas before and after treatment. Three dosage levels of stabilizer and four different curing periods were investigated. Test results indicate that LISS is an effective stabilizing agent, which not only reduces swelling and soil plasticity but also increases soil strength. Furthermore, a similar type of LISS is utilized to treat the soil in Dallas via deep injection using a hydraulic pump. Field emission scanning electron microscopy results on the test soil showed that the stabilizing program is likely to work through clay flocculation and morphological variations in the clay particles.

scholarly journals Shear Strength of Medium Plastic Expansive Soil Reinforced with Polyester Fibers

2018 ◽  
Vol 26 (2) ◽  
pp. 1-8
Author(s):  
Niraj Singh Parihar ◽  
Rajesh Prasad Shukla ◽  
Ashok Kumar Gupta
Keyword(s):  
Shear Strength ◽  
Aspect Ratio ◽  
Soil Stabilization ◽  
Expansive Soils ◽  
Expansive Soil ◽  
Reinforced Soil ◽  
Maximum Enhancement ◽  
Aspect Ratios ◽  
Polyester Fibers ◽  
Strain Relationship

AbstractThis Expansive soils are very problematic as they are prone to substantial settlements, heave, and possess low bearing capacity. These soils cover more than 20% of the land cover of India and cause obstructions in the development of road networks, railways, and various other construction activities. They make soil stabilization essential. An investigation was carried out to determine the effect of various proportions of randomly-oriented polyester fibers on the shear strength of expansive soil. The unconfined compressive strength of reinforced soil was determined by incorporating four fiber contents, i.e., 0.25%, 0.50%, 0.75%, and 1%, with varying aspect ratios. The effect of various aspect ratios of 20, 40, and 60 were studied in the present work. The stress-strain relationship for different aspect ratios and fiber contents is also presented in the study. The optimum quantity of fibers was found to be 0.75% of the total weight of the soil. A maximum enhancement in the strength of the soil was achieved with fibers with an aspect ratio of 40. The effect of the aspect ratio is significant with a fiber content of 0.50 to 0.75%. The peak strength of untreated soil is found at strain levels of 6-8%, whereas it increases to 10-12% in reinforced soil. A statistical analysis was also performed to develop a regression equation to predict the improvement in the strength of the medium plastic expansive soil used in the study.

scholarly journals Study on Mechanical Properties of the Expansive Soil Treated with Iron Tailings Sand

2021 ◽  
Vol 2021 ◽  
pp. 1-11
Author(s):  
Chengfu Chu ◽  
Fei Zhang ◽  
Daoxiang Wu ◽  
Meihuang Zhan ◽  
Yun Liu
Keyword(s):  
Shear Strength ◽  
Moisture Content ◽  
Expansive Soils ◽  
Expansive Soil ◽  
Friction Angle ◽  
Dry Density ◽  
Maximum Dry Density ◽  
Occlusal Force ◽  
Optimal Moisture Content ◽  
Tailings Sand

Aiming at researching shear strength parameters of expansive soil modified by industrial waste iron tailings sand, the enhancement of expansive soil is explored from macroscopic and microscopic aspects. After characterization and testing by various means, the results show that expansive soil modified by iron tailings sand will increase the maximum dry density of the improved soil and reduce its optimal moisture content, which is beneficial in tuning the moisture content at the construction site. In addition, iron tailings sand can improve the shear strength of expansive soils. The influence of iron tailings sand on cohesion increases first, then decreases, and reaches the peak value at 30%, while the effect on internal friction angle exhibits a continuously increasing trend. Furthermore, according to mercury intrusion tests and microangle analysis, the addition of iron tailings sand can reduce the tiny pores and enhance the occlusal force of the soil. Simultaneously, it increases the number of large pores, maximizing the macroscopic strengthening of iron tailings sand towards the expansive soil.

Surface Crack Development Rules and Shear Strength of Compacted Expansive Soil Due to Dry–Wet Cycles

2018 ◽  
Vol 37 (4) ◽  
pp. 2647-2657 ◽  
Author(s):  
Zhen Huang ◽  
Bingxu Wei ◽  
Lujun Zhang ◽  
Wei Chen ◽  
Zimao Peng
Keyword(s):  
Shear Strength ◽  
Surface Crack ◽  
Expansive Soil ◽  
Crack Development

Research on the Shear Strength Properties of Expansive Soils

2012 ◽  
Vol 256-259 ◽  
pp. 287-292
Author(s):  
Yi Chen ◽  
Jing Zhao ◽  
Xiao Hong Hu
Keyword(s):  
Shear Strength ◽  
Water Content ◽  
Expansive Soils ◽  
Friction Angle ◽  
Strength Properties ◽  
Water Diversion ◽  
Dry Density ◽  
Initial Water Content ◽  
Initial Water ◽  
North Water

The shear strength of expansive soils is now a key geotechnical problem. The water content and dry density of expansive soils have deep effect on its shear strength. For analyzing the detail relationship of the water content, dry density and shear strength of this special soil, direct shear test was carried out with the samples from Xinxiang in middle line of South to North water diversion project. The results indicate that both of the cohesion and friction angle grow with dry density and decrease with initial water content. Applying the linear regression calculation, we obtained mathematical expressions which reveal the variation of shear strength with the dry density and initial water content of Xinxiang expansive soils.

scholarly journals Comparative Analysis of Shear Strength Parallel to Fiber of Different Local Bamboo Species in the Philippines

2021 ◽  
Vol 13 (15) ◽  
pp. 8164
Author(s):  
Brian E. Bautista ◽  
Lessandro E. O. Garciano ◽  
Luis F. Lopez
Keyword(s):  
Mechanical Properties ◽  
Shear Strength ◽  
Comparative Analysis ◽  
Strength Properties ◽  
The Philippines ◽  
Bamboo Species ◽  
Test Protocol ◽  
Future Design ◽  
Average Shear Strength ◽  
Bambusa Vulgaris

There are limited published studies related to the mechanical properties of bamboo species in the Philippines. In this study, the shear strength properties of some economically viable bamboo species in the Philippines were properly characterized based on 220 shear test results. The rationales of selecting this mechanical property are the following: (1) Shear strength, parallel to the fiber, has the highest variability among the mechanical properties; and (2) Shear is one of the governing forces on joint connections, and such connections are the points of failure on bamboo structures when subjected to extreme loading conditions. ISO 22157-1 (2017) test protocol for shear was used for all tests. The results showed that Bambusa blumeana has the highest average shear strength, followed by Gigantochloa apus, Dendrocalamus asper, Bambusa philippinensis, and Bambusa vulgaris. However, comparative analysis, using One-way ANOVA, showed that shear strength values among these bamboo species have significant differences statistically. A linear regression model is also established to estimate the shear strength of bamboo from the physical properties. Characteristic shear strength is also determined using ISO 12122-1 (2014) for future design reference.

scholarly journals Improved strength properties of LVL glued using PVAc adhesives with physical treatment-based Rubberwood (Hevea brasiliensis)

2020 ◽  
Vol 5 (1) ◽  
pp. 711-725
Author(s):  
Sutrisno ◽  
Eka Mulya Alamsyah ◽  
Ginanjar Gumilar ◽  
Takashi Tanaka ◽  
Masaaki Yamada
Keyword(s):  
Shear Strength ◽  
Hevea Brasiliensis ◽  
Formaldehyde Emission ◽  
Strength Properties ◽  
Modulus Of Rupture ◽  
Horizontal Shear ◽  
Physical Treatment ◽  
Cold Pressing ◽  
Laminated Veneer Lumber ◽  
Pressing Time

AbstractThe properties of the laminated veneer lumber (LVL) composed of the boiled veneer of Rubberwood (Hevea brasiliensis) using polyvinyl acetate (PVAc) adhesives in various cold-pressing time and various conditioned time with loaded and unloaded were studied. Five-ply LVL was produced by boiling veneer at 100°C for 90 min as pretreatment and cold-pressing time at 12 kgf cm−2 for 1.5, 6, 18, and 24 h then conditioned at 20°C and 65% relative humidity (RH) with loaded (12 kgf cm−2) and unloaded for 7 days as physical treatment. Especially for the delamination test, the specimens were immersed at 70 ± 3°C for 2 h and dried in the oven at 60 ± 3°C for 24 h; then, the specimens were solidified at room temperature (20°C and 65% RH) with loaded (12 kgf cm−2) and unloaded for 7, 10, 12, and 14 days. To determine the performance of LVL, the density, moisture content (MC), delamination, modulus of elasticity (MOE), modulus of rupture (MOR), horizontal shear strength, and formaldehyde emission tests were conducted according to the Japanese Agricultural Standard (JAS 2008) for structural LVL. The MOE and MOR values were significantly influenced by the physical treatment, however, neither to horizontal shear strength nor to formaldehyde emission. The best performance of LVL has resulted from unloaded LVL with cold-pressed time for 18 h; the MOE and MOR values were 9,345.05 ± 141.61 N mm−2 and 80.67 ± 1.77 N mm−2, respectively. The best value of the horizontal shear strength was obtained from the LVL with 18 h cold-pressing time and conditioned with loaded (13.10 ± 1.47 N mm−2) and unloaded (12.23 ± 1.36 N mm−2). The percentage of delamination values decreased with an increase in the cold-pressing time and conditioning time. The lowest value of delamination (19.06%) was obtained from the LVL with 24 h cold-pressing time and conditioned with loaded for 14 days. Except the delamination test, all other properties fulfilled the JAS.

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