scholarly journals Model Test Study on Deformation Characteristics of a Fissured Expansive Soil Slope Subjected to Loading and Irrigation

2021 ◽  
Vol 11 (22) ◽  
pp. 10891
Author(s):  
Zhiqing Li ◽  
Youxing Kong ◽  
Le Fu ◽  
Yingxin Zhou ◽  
Zhengfu Qian ◽  
...  
Keyword(s):  
Expansive Soils ◽  
Compressive Strain ◽  
Expansive Soil ◽  
Image Correlation ◽  
Water Infiltration ◽  
Mutual Transformation ◽  
Soil Slope ◽  
Strain Data ◽  
The Impact ◽  
The Relationship

Expansive soils are characterized by repeated swelling and shrinkage. They cause great damage to engineering projects because of their expansiveness, over-consolidation and propensity to crack. However, the impact of cracks on the stability of an expansive soil slope during loading and irrigation is not yet fully understood. This study aimed to investigate the relationship between slope state and crack development in fissured expansive soils. A series of physical model tests with different types of cracks were conducted, in which the fissured expansive soil slopes were subjected to different loadings (1.6, 3.2, 4.8, 6.4, 16 MPa), and irrigated at a flow rate of 25 mL/min. The VIC-2d software, which utilizes the digital image correlation principle, was used to quantitatively obtain the horizontal and vertical strain data of the slope model. The closure and opening of cracks, and the slope state after loading and irrigation were monitored by strain data analysis using VIC-2d software. The results indicate that the excessive overlying stress revives the existing cracks and produces sliding along the crack interface. The sliding surface of the fissured expansive soil slope became shallower due to the water infiltration. It was demonstrated that the middle and foot of the fissured expansive soil slope were the key positions for reinforcement from the perspective of the mutual transformation of tensile strain and compressive strain on the surface of the slope. It is of great importance to study the relationship between the crack strain state and deformation trend of a slope subjected to loading and infiltration to understand the progressive surface- or shallow-layer sliding mechanisms, and reinforce key areas of the slopes in areas containing moderately or strongly expansive soils with abundant cracks.

scholarly journals Performance estimation of a shallow foundation on an unsaturated expansive soil slope subjected to rainfall infiltration

2021 ◽  
Vol 337 ◽  
pp. 03009
Author(s):  
Mengxi Tan ◽  
Sai K. Vanapalli
Keyword(s):  
Slope Stability ◽  
Limit Equilibrium ◽  
Expansive Soil ◽  
Rainfall Infiltration ◽  
Performance Estimation ◽  
Shallow Foundation ◽  
Water Infiltration ◽  
Rational Approach ◽  
Soil Slope ◽  
Unsaturated Expansive Soil

In the last two decades, there has been a significant increase in infrastructure development on slopes of hilly regions of the world, due to population growth. There are many infrastructures on unsaturated expansive slopes, especially in semi-arid and arid regions. Rainfall infiltration is one of the major factors that contributes to the slope and infrastructure foundations failures on hilly slopes with unsaturated expansive soils. In the current study, a rational approach is proposed considering the combined influence of the foundation-slope behavior based on the principles of unsaturated soil mechanics. This is achieved by a novel numerical modelling approach using the commercial software Geo-studio to investigate the performance of strip foundation located on the top of the unsaturated expansive soil slope subjected to various rainfall infiltration conditions. Hydro-mechanical coupling analysis is conducted to evaluate the rainfall water infiltration influence combined with slope stability analysis using limit equilibrium method. Comparisons are made between both the foundation bearing capacity, slope stability before and after rainfall water infiltration. Different failure mechanisms of the foundation and slope system are presented with and without foundation loading for various rainfall scenarios. Results summarized in this paper are helpful for the geotechnical engineers for understanding the performance of shallow foundations on unsaturated expansive soil slopes considering the influence of rainfall infiltration conditions.

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.

Strain concentration during the compression of a carbon/epoxy composite after impact

2015 ◽  
Vol 6 (2) ◽  
pp. 279-289
Author(s):  
Martin Kadlec ◽  
Václav Kafka
Keyword(s):  
Composite Laminates ◽  
Numerical Models ◽  
Compressive Strain ◽  
Composite Plates ◽  
Image Correlation ◽  
Resin Matrix ◽  
Full Field ◽  
Content Type ◽  
Strain Concentration ◽  
The Impact

Purpose – Polymer composite panels are widely used in aeronautic and aerospace structures due to the high strength-to-weight ratios of these structures. The purpose of this paper is to determine the strain fields and failure mechanisms during the failure of the impacted composite laminates when subjected to compression. Design/methodology/approach – A series of compression-after-impact (CAI) tests was performed on composite plates 150×100×4 mm3 made of a carbon-fibre-reinforced epoxy resin matrix. A digital image correlation and fractographic analysis by means of optical and electron microscopy are used for this purpose. Findings – The full-field strain measurements indicate a concentrated band of compressive strain near the impact, where buckling occurs. The results indicate that the strain concentration factor can be considered to be a failure criterion. The shear strain visualisation around the impact reveals an area of heterogeneous deformation that is comparable to the detected delamination area acquired by an ultrasonic technique. Fibre and inter-fibre fractures are described for the particular impact site regions. Originality/value – These experiments could improve numerical models for the CAI analyses and help to build a new criterion for this severe failure mode.

Analysis of Fissured Expansive Soil Slope Stability and its Reinforcement with Anti-Slippery Piles

2013 ◽  
Vol 275-277 ◽  
pp. 1489-1492 ◽  
Author(s):  
Hui Sun ◽  
Bo Hu ◽  
Guo Qiang Zhang
Keyword(s):  
Slope Stability ◽  
Expansive Soils ◽  
Limit Equilibrium ◽  
Expansive Soil ◽  
Water Diversion ◽  
Soil Slope ◽  
Water Diversion Project ◽  
North Water ◽  
Channel Slope ◽  
The Stability

Fissure is one of the most important characteristics in expansive soil. It’s an important factor affecting slope stability in the expansive soil area. With the study of expansive soils typical channel slope fissured characters in the South-to-North Water Diversion Project, different impaction on slope stability such as location and inclination of the fissure are analyzed. By using the limit equilibrium method, the stability of expansive soil slope is analyzed; the most adverse condition of expansive soil slope is concluded. Then anti-slippery pile reinforcement in expansive soil channel slope is studied by using finite difference method. The research is of great significance to the construction and reinforcement of expansive soil slopes in South-to-North Water Diversion Project.

scholarly journals Quantification of the influence of different Mini Disk Infiltrometer (MDI) suction settings when measuring infiltration across various soil types

2021 ◽  
Author(s):  
Nathaniel Revell ◽  
Craig Lashford ◽  
Matthew Blackett ◽  
Matteo Rubinato
Keyword(s):  
Soil Compaction ◽  
Soil Health ◽  
Water Infiltration ◽  
Water Volume ◽  
Double Ring ◽  
Single Ring ◽  
The Uk ◽  
The Impact ◽  
First Time ◽  
The Relationship

Defining the infiltration characteristics of an area is beneficial for understanding soil compaction, determining soil health, and measuring the rate of surface water infiltration, which is needed for hydrological modelling. Single and double ring infiltrometers (SRI, DRI) are commonly used to determine infiltration characteristics in the field, however these are frequently impractical due to the required water volume, the weight and the intrusiveness of measurement, hindering the ease of replication. The Mini Disk Infiltrometer (MDI) offers a lightweight, portable and non-intrusive method of measuring infiltration, however no previous research has explained the influence of changing the tension settings on the collected infiltration data. To address this gap, this novel study tested the relationship between infiltration data collected using all tension settings of the Mini Disk Infiltrometer (MDI), against infiltration data collected using a 100mm Single Ring Infiltrometer (SRI). Three soil textures (sand, silt and clay) were collected from different geographical areas of the UK and deposited within the experimental facility designed for this study. Controlled infiltration measurements were taken with both the MDI and the SRI for each soil type, to further define the impact of MDI tension settings on derived infiltration, in comparison to the SRI. For the first time, the results show that the MDI tension setting of 0cm most closely replicated the findings of the SRI across all soils, which was supported through applying the Nash and Sutcliffe Efficiency (NSE) analysis. The accuracy with which the MDI replicated the infiltration of the SRI reduced as tension increased. Consequently, the previously assumed ideal tension setting of 2 cm, as defined by the MDI handbook and used in previous research, does not offer an accurate representation of derived infiltration.

scholarly journals Improvement of the Geotechnical Properties of Expansive Soils Using Fly Ash

2021 ◽  
Vol 56 (1) ◽  
Author(s):  
Nahla M. Salim
Keyword(s):  
Fly Ash ◽  
Specific Gravity ◽  
Expansive Soils ◽  
Expansive Soil ◽  
Swelling Pressure ◽  
Geotechnical Properties ◽  
Plasticity Index ◽  
Dry Density ◽  
The Impact ◽  
Swell Pressure

This test program studies the impact of using fly ash on prepared soil by adding different percentages of fly ash (5%, 10% and 15%) by dry soil weight. The expansive soil was prepared in the laboratory by mixing natural soil (Al-Nahrawan clayey soil) with different percentages of bentonite (30%, 50% and 70%). The experimental study focuses on the effects of the fly ash content on the free swell index, swell potential, swelling pressure, plasticity and compaction characteristics of expansive soil. The influence of these admixtures was compared with those of untreated soils. The results show that the plasticity index, the optimum moisture content, swelling percent and swell pressure increase with an increase in the bentonite percentage, and the maximum dry density and specific gravity decrease with increases in the bentonite percentage. The plasticity index, specific gravity, swelling and swelling pressure decrease with increases in the fly ash percentage. The optimum percentage of fly ash was 5%, where the swell and swell pressure decreased by a large amount. The results showed that the addition of fly ash to expansive soils has a positive effect on the soil's geotechnical properties.

scholarly journals Utilization of Lime Sludge Activated by Salt in Egyptian Expansive Soil Improvement

2021 ◽  
Vol 9 (2) ◽  
Author(s):  
Carmen M. Sharaby ◽  
Mohie Eldin M. El mashad ◽  
Mona A. Fakhry ◽  
Marwa H. Salama
Keyword(s):  
Expansive Soils ◽  
Expansive Soil ◽  
Soil Improvement ◽  
Liquid Limit ◽  
Engineering Properties ◽  
Chloride Salt ◽  
Industrial Solid Waste ◽  
Positive Effects ◽  
Lime Sludge ◽  
The Impact

Expansive soils are active clays which cause engineering problems all over the world. This research deals with the impact of lime sludge (LS) as industrial solid waste from sugar-cane factory and sodium chloride salt (NaCl) on engineering properties of expansive soil. In this research, an analytical study of chemical and physical properties of Egyptian expansive soil in Sixth of October City was made as a case study. The laboratory results showed improvement of chemical, microstructural properties and thus the engineering properties of this soil. The results of chemical analysis showed the ability of soil to improve pH; soil alkalinity raise to the required level of stabilization. After soil treatment, Microstructure scanning electron with energy dispersive spectroscopy (SEM-EDX) analyses showed that new cementitious compounds are formed and soil was changed from a weak dispersed structure to strong flocculated structure. It was also observed by increasing LS and NaCl concentrations the plastic limit increased and the liquid limit decreased, hence decreased plasticity index; the rate of soil free swelling is decreased due to change of expansive soil texture. Therefore, lime sludge activated by NaCl has positive effects on engineering properties of soil. By this way we protect the environment from industrial solid wastes.  

scholarly journals Correlation between Swelling Pressure and Free Swell of Greater Cairo City Expansive Soils – A Case Study

2019 ◽  
pp. 1-6
Author(s):  
Nasser A. A. Radwan ◽  
Khaled M. M. Bahloul
Keyword(s):  
Expansive Soils ◽  
Expansive Soil ◽  
Swelling Pressure ◽  
Plasticity Index ◽  
Greater Cairo ◽  
Multiple Variable ◽  
Free Swell ◽  
Multiple Variable Regression ◽  
The Relationship

The aim of this research is to investigate experimentally the relationship between free swell, plasticity index of expansive soil found in greater Cairo City Suburbs, Egypt with swelling pressure of mentioned soil. Predicting Swelling Pressure of any soil is a time consuming and expensive test in comparison to determining plasticity index and free swell which are simple, fast and economic tests. In present research six samples of expansive soil were collected from different locations of study area. The method uses single variable and multiple variable regression analysis using Microsoft excel software.

scholarly journals Reducing Compressibility of the Expansive Soil by Microbiological-Induced Calcium Carbonate Precipitation

2021 ◽  
Vol 2021 ◽  
pp. 1-12
Author(s):  
Xiaobing Li ◽  
Chunshun Zhang ◽  
Hongbin Xiao ◽  
Weichang Jiang ◽  
Junfeng Qian ◽  
...  
Keyword(s):  
Calcium Carbonate ◽  
Expansive Soils ◽  
Expansive Soil ◽  
Hyperbolic Function ◽  
Carbonate Precipitation ◽  
Calcium Carbonate Precipitation ◽  
Compression Performance ◽  
Two Parameters ◽  
The Impact ◽  
Compression Characteristics

Most of the research studies on the improvement of expansive soils are focused on reducing their expansive properties; however, there are few studies on the impact of the soil compressibility after the improvement. In this paper, through indoor high-pressure consolidation tests, the recent microbial-induced calcium carbonate precipitation (MICP) technology is studied to improve the compression characteristics of the expansive soil. The significant effect of different microbial concentrations (achieved by different number of treatments) on the compression deformation is revealed with the hyperbolic function that involves two parameters with clear physical meanings. In particular, after 6 times of treatment with the microbial solution, the compression characteristics of the expansive soil reach the best improvement effect; continuing to increase the number of microbial treatments is, otherwise, not conducive to improving the soil compression performance. Also, a dramatical increase of the structural strength of the microbial-treated expansive soil is presented and investigated. Moreover, we performed a scanning electron microscope (SEM) experiment and confirmed the existence of crystals due to mineralization. This study shows that MICP is an effective and environmentally friendly means of reducing the compressibility of the expansive soil.

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