Description
ABSTRACT
It has been discovered long time ago that organic matter influences physical and mechanical properties of soils. Samples collected from a long-term agriculture experiment involving different treatments, have been subjected to differential thermal analysis (DTA) to deduce the organic matter content and its composition. Water release characteristics and soil strength have been measured with the suction plate method and indirect tension method, respectively. Impedance tube measurements made on sand samples with various water content show that soil surface absorption decreases with increasing water content. Changes in absorption coefficient spectra deduced from impedance tube measurements on soil samples extracted from the long-term agriculture experiment involving different organic matter content but similar water content are consistent with predictions of the effects of changes in porosity and permeability in rigid-porous air-filled media.
TABLE OF CONTENTS
COVER PAGE
TITLE PAGE
APPROVAL PAGE
DEDICATION
ACKNOWELDGEMENT
ABSTRACT
CHAPTER ONE
- INTRODUCTION
- BACKGROUND OF THE STUDY
- PROBLEM STATEMENT
- AIM AND OBJECTIVE OF THE STUDY
- SIGNIFICANCE OF THE STUDY
- SCOPE OF THE STUDY
- METHODOLOGY
- PROJECT ORGANISATION
CHAPTER TWO
LITERATURE REVIEW
- OVERVIEW OF SOIL
- MECHANICAL PROPERTIES OF SOIL
- SOIL ORGANIC MATTER
CHAPTER THREE
- MATERIAL AND METHODS
CHAPTER FOUR
- RESULT
- DISCUSSION
CHAPTER FIVE
- CONCLUSION
- REFERENCES
CHAPTER ONE
1.0 INTRODUCTION
1.1 BACKGROUND OF THE STUDY
Soil is a complex porous elastic medium. Structural properties of soil (porosity, pore size distribution, tortuosity, air permeability etc.) can be regulated by different factors (both biotic and abiotic). It has been observed that organic matter had a strong interaction with physical properties of soil such as porosity and resistance, mechanical stresses (1). Poor structural condition of soil (compaction, degradation) can restrict plant growth and affect crop yield. So, it is very important in agricultural research to have reliable information and knowledge regarding physical properties and structural stability of soil (2). In this study, we are observing the physical behavior of long-term agricultural soil including pore-related properties, water retention, mechanical properties etc. and trying to identify the impact of organic matter and nitrogen applications on soil structure-related properties. To achieve our research goal, we adopted different measurement techniques, commonly used in soil physics and engineering. Acoustical excitation provides a non-invasive alternative to the classical methods used in soil physics and can be utilized to determine properties of soil (2, 3, 4, 5, 6). Sound wave propagation through soils is a mechanical phenomenon that causes a small perturbation without altering the fabric of soils (7). Attenborough and colleagues (4) found that sound can penetrate through soil due to surface porosity and associated air permeability and thus to be absorbed and undergo phase change through friction and thermal exchanges between the pore fluid and the surrounding solid. Sound propagation in soil or any porous media is influenced by its texture, structure, roughness, degree of compaction and the moisture content (3, 5, 7, 8, 9). Acoustical techniques have been used to study the formation of surface crusts (10).
Classical Biot theory for a porous and elastic medium (11, 12) predicts the existence of three wave types in the porous medium: two types of dilatational or compressional waves (1st and 2nd kind) and one rotational or shear wave. In a soil consisting of a dense solid frame with a low-density fluid, such as air saturating the pores, the first kind of dilatational wave, often called the ‘fast’ wave which is characterized by particle motion in phase with fluid motion, has a velocity very similar to the 2 nd dilatational wave (or “P” wave in geophysics) travelling in the drained frame. However, the attenuation of the first dilatational wave type is higher than that of the P wave in the drained frame. The extra attenuation comes from the viscous forces in the pore fluid acting on the pore walls. This first dilatational wave has negligible dispersion and its attenuation is proportional to the square of the frequency, as is the case also for the rotational wave. If fast waves are excited predominantly, viscous coupling at pore walls means that some of their energy is carried in the pore fluid as the second type of dilatational wave or ‘slow’ wave. In air-saturated soils, the second dilatational wave, often called the ‘slow’ wave, has a much lower velocity than the first. The attenuation of the ‘slow’ wave stems not only from viscous forces at the pore walls but from thermal exchange with the pore walls. In the rigid-frame limit, theory predicts a single ‘slow’ wave which governs the acoustical properties of rigid-framed porous solids and is the wave type responsible for the acoustical properties of sound absorbing materials (13). Models for the acoustical properties of rigid-porous media introduce several parameters such as the tortuosity of the pore space, porosity, viscous characteristic length, thermal characteristic length, flow resistivity and dynamic shape factors (14, 15).
1.2 PROBLEM STATEMENT
It has been observed that organic matter had a strong interaction with acoustical properties of soil such as porosity and resistance, mechanical stresses and it is very difficult to determine. Acoustical excitation provides a non-invasive alternative to the classical methods used in soil physics and can be utilized to determine properties of soil
1.3 AIM AND OBJECTIVES OF THE STUDY
The main aim of this work is to study the influence of organic matter on acoustical properties of soil. The objectives are:
- To carry out an experiment on how organic matter influences the acoustical properties of soil.
- To study the properties of soil
- To study how sound penetrates the soil
1.4 SIGNIFICANCE OF THE STUDY
This study will throw light on the knowledge regarding physical properties and structural stability of soil. In this study, physical behavior of long-term agricultural soil including pore-related properties, water retention, mechanical properties.
1.5 SCOPE OF THE STUDY
In this study we are going to find out how sound can penetrate through soil due to surface porosity and associated air permeability and thus to be absorbed and undergo phase change through friction and thermal exchanges between the pore fluid and the surrounding solid. And also how sound propagation in soil or any porous media is influenced by its texture, structure, roughness, degree of compaction and the moisture content.
1.6 LIMITATION OF STUDY
As we all know that no human effort to achieve a set of goals goes without difficulties, certain constraints were encountered in the course of carrying out this project and they are as follows:-
- Difficulty in information collection: I found it too difficult in laying hands of useful information regarding this work and this course me to visit different libraries and internet for solution.
- Financial Constraint: Insufficient fund tends to impede the efficiency of the researcher in sourcing for the relevant materials, literature or information and in the process of data collection (internet).
Time Constraint: The researcher will simultaneously engage in this study with other academic work. This consequently will cut down on the time devoted for the research work.
1.7 RESEARCH METHODOLOGY
In the course of carrying this study, numerous sources were used which most of them are by visiting libraries, consulting journal and news papers and online research which Google was the major source that was used.
1.8 PROJECT ORGANISATION
The work is organized as follows: chapter one discuses the introductory part of the work, chapter two presents the literature review of the study, chapter three describes the methods applied, chapter four discusses the results of the work, chapter five summarizes the research outcomes and the recommendations.
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