Construction of building on clay soil is highly risky due to its poor strength. Clayey soil creates many problems to the Geotechnical Engineers primarily because of repeated change of moisture content. Normally, these soils increase in size and swell when they absorb water and reduce in size and shrink when they become dry. Volume change in soil leads to distortions in the form of settlement due to contraction as a result of dryness or in the form of expansion due to swelling as a result of the absorption of water. There may be the need for soil treatment to improve the engineering properties of such soil. Compacted bentonite is often used as a buffer materials and for radioactive waste disposal system. A good understanding of the hydro-mechanical behavior of clay soil is essential to ensure safe disposal.
The present study reports the results on the effects of temperature on swelling pressure and compressibility characteristics of soil. In this study, two different type of soils were used. One of them was a bentonite (liquid limit = 139%) procured from Bikaner, Rajasthan another one was Rourkela local soil (liquid limit = 35%). A new oedometer was designed and developed in-house to carry out consolidation and swelling pressure tests at a higher temperature. Swelling pressures tests on compacted bentonite specimens of targeted dry density of 1.6 Mg/m3 were conducted under constant volume condition for the temperature range between 25 to 90 0C. Compressibility tests at various temperatures for both soils were conducted using distilled water as the saturating fluid.
It observed that high temperature caused an increase in swelling pressure and compressibility index of bentonite soil. There is no effect of temperature on compressibility index of Rourkela local soil.
Table of Contents
1 Introduction
1.1 Background and motivation
1.2 Objective of the work
1.3 Book Overview
2 Literature Review
2.1 Introduction
2.2 Identification of expansive soil
2.3 Structure of clay mineral
2.3.1 Kaolinite
2.3.2 Illite
2.3.3 Montmorillonite
2.4 Structure of compacted bentonite
2.5 Forces and charges in clay system
2.6 Particle association in Clay
2.7 Swelling Mechanism in Clay
2.8 Swelling pressure
2.8.1 Swelling pressure testing in Laboratory
2.8.2 Swelling pressure measurement devices
2.9 Compressibility behavior of bentonite
2.10 Effect of higher temperature on swelling and compressibility
3 Material and Methods
3.1 Properties of Soil studied
3.1.1 XRD Analysis
3.1.2 SEM Analysis
3.2 Modified oedometer
3.3 Swelling Pressure Test
3.3.1 Experimental setup
3.3.2 Constant volume swelling pressure test
3.4 Consolidation Test
3.4.1 Experimental setup
3.4.2 Methodology to Measure Compressibility
4 Result and Discussion
4.1 Swelling Pressure Test Result
4.2 Compressibility Test Result
5 Conclusions and Scope for Further Study
5.1 Conclusions
5.2 Scope for Further Study
Objectives and Topics
This work investigates the effects of elevated temperatures on the swelling pressure and compressibility characteristics of compacted bentonite, which is commonly used as a buffer and backfilling material in nuclear waste disposal repositories.
- Experimental evaluation of swelling pressure at various temperatures (25°C to 90°C).
- Assessment of soil compressibility behavior under thermal and mechanical loading.
- Development of a modified oedometer for controlled-temperature testing.
- Microstructural and mineralogical analysis of bentonite and local soil samples.
Extract from the Book
1.1 Background and motivation
An expansive soil can be identified by the potential of the soil to swell independently of field conditions such as water content and surcharge pressure. Because of swelling behavior properties, these types of soil produces problems like settlement and foundation crack. Many times these problems become unfavorable. The plasticity index of soil is the main indicator whether the soil is expansive in nature or not. Excess shrink or swelling behavior of these soils make the ground slope unstable and cause the unfavorable problem to the building foundation. In this work, the temperature effect on the swelling and compressibility of the clay were investigated. Most designs of geological repositories constructed at a greater depth for nuclear wastes based on the concept of multi-barrier. The concept of multi-barrier includes the natural geological barrier, engineered barriers made from compacted bentonite and the metal canisters. The natural geological barrier is nothing but host rock. Compacted bentonite-based materials are relevant materials for the purpose of the barrier and backfilling material in the waste repository, because of their high swelling, high radionuclide reduction capacity and low value of permeability (Pusch, 1979; Yong et al., 1986; Villar and Lloret, 2008; Komine and Watanabe, 2010). Stability of high-level radioactive waste disposal repository mainly depends on the swelling pressure value of compacted bentonites (Tripathy et al., 2014).
Summary of Chapters
1 Introduction: Discusses the motivation for studying expansive soils in the context of nuclear waste repositories and outlines the research objectives.
2 Literature Review: Provides a detailed overview of clay mineral structure, swelling mechanisms, swelling pressure measurement techniques, and existing research on temperature effects.
3 Material and Methods: Details the laboratory procedures, physical properties of the soils, and the development of the modified oedometer used for elevated-temperature tests.
4 Result and Discussion: Presents the experimental findings regarding swelling pressure and compressibility, analyzing the influence of temperature on these properties.
5 Conclusions and Scope for Further Study: Summarizes the key findings of the investigation and suggests future directions for research in the field.
Keywords
Bentonite, Expansive soil, Swelling pressure, Compressibility, Nuclear waste repository, Temperature effect, Oedometer, Clay mineralogy, Consolidation, Moisture content, Degree of saturation, Thermal loading, Microstructure, Geotechnical engineering, Barrier material
Frequently Asked Questions
What is the primary focus of this work?
The research focuses on investigating the impact of elevated temperatures on the swelling pressure and compressibility behavior of compacted bentonite, which acts as a protective barrier in nuclear waste repositories.
What are the main thematic fields?
The work covers geotechnical engineering, specifically concerning expansive soil properties, thermal-hydraulic-mechanical behavior of clay minerals, and laboratory test method development.
What is the primary research objective?
The main objective is to determine how swelling pressure and compressibility of bentonite and local soil change when subjected to temperatures ranging from 25°C to 90°C.
Which scientific method is utilized?
The study employs experimental laboratory investigations using a specifically designed, modified oedometer for temperature-controlled swelling and consolidation tests.
What is addressed in the main chapters?
The main body covers the theoretical literature, detailed material characterization using XRD and SEM analysis, experimental test setups, and the analysis of results regarding swelling and settlement rates.
Which keywords best characterize the work?
Key terms include bentonite, swelling pressure, compressibility, nuclear waste, temperature effect, and geotechnical soil testing.
Why is the swelling pressure of bentonite important for nuclear repositories?
It is vital because bentonite serves as a barrier to structurally hold waste canisters in place and provides necessary water tightness to limit radionuclide migration.
How does temperature affect the compression index (Cc) of the bentonite used?
The study observed that the compressibility index of bentonite increases with temperature, likely due to a decrease in water viscosity, which in turn enhances the permeability of the clay.
What are the limitations of the current study?
The work is limited to specific temperature effects and dry densities; the author acknowledges that further studies on suction components and different electrolyte concentrations are required.
- Quote paper
- Ahsan Rabbani (Author), 2018, Effect of Temperature on Swelling Pressure and Compressibility of Soil, Munich, GRIN Verlag, https://www.grin.com/document/425569
