Investigatory Project “ Kaymito Leaves Decoction as Antiseptic Mouthwash ”
Introduction
1.1 Problem Statement
Fractures are prevalent in natural and synthetic structural media, even in the best engineered materials. We find fractures in bedrock, in sandstone aquifers and oil reservoirs, in clay layers and even in unconsolidated materials (Figures 1.1 to 1.4).
Fractures are also common in concrete, used either as a structural material or as a liner for storage tanks (Figure 1.5). Clay liners used in landfills, sludge and brine disposal pits or for underground storage tanks can fracture, releasing their liquid contents to the subsurface (Figure 1.6). Even “flexible” materials such as asphalt fracture with time
(Figure 1.7). The fact that fractures are inevitable has led to spending billions of research dollars to construct “safe” long-term (10,000 years or more) storage for high-level nuclear waste (Savage, 1995; IAEA, 1995), both to determine which construction techniques are least likely to result in failure and what are the implications of a failure, in terms of release to the environment and potential contamination of ground water sources or exposure of humans to high levels of radioactivity.
Why do materials fail? In most cases, the material is flawed from its genesis. In crystalline materials, it may be the inclusion of one different atom or molecule in the structure of the growing crystal, or simply the juncture of two crystal planes. In depositional materials, different grain types and sizes may be laid down, resulting in layering which then becomes the initiation plane for the fracture. Most materials fail because of mechanical stresses, for example the weight of the overburden, or heaving
(Atkinson, 1989; Heard et al., 1972). Some mechanical stresses are applied constantly2 until the material fails, others are delivered in a sudden event. Other causes of failure are thermal stresses, drying and wetting cycles and chemical dissolution.
After a material fractures, the two faces of the fracture may be subject
1.1 Problem Statement
Fractures are prevalent in natural and synthetic structural media, even in the best engineered materials. We find fractures in bedrock, in sandstone aquifers and oil reservoirs, in clay layers and even in unconsolidated materials (Figures 1.1 to 1.4).
Fractures are also common in concrete, used either as a structural material or as a liner for storage tanks (Figure 1.5). Clay liners used in landfills, sludge and brine disposal pits or for underground storage tanks can fracture, releasing their liquid contents to the subsurface (Figure 1.6). Even “flexible” materials such as asphalt fracture with time
(Figure 1.7). The fact that fractures are inevitable has led to spending billions of research dollars to construct “safe” long-term (10,000 years or more) storage for high-level nuclear waste (Savage, 1995; IAEA, 1995), both to determine which construction techniques are least likely to result in failure and what are the implications of a failure, in terms of release to the environment and potential contamination of ground water sources or exposure of humans to high levels of radioactivity.
Why do materials fail? In most cases, the material is flawed from its genesis. In crystalline materials, it may be the inclusion of one different atom or molecule in the structure of the growing crystal, or simply the juncture of two crystal planes. In depositional materials, different grain types and sizes may be laid down, resulting in layering which then becomes the initiation plane for the fracture. Most materials fail because of mechanical stresses, for example the weight of the overburden, or heaving
(Atkinson, 1989; Heard et al., 1972). Some mechanical stresses are applied constantly2 until the material fails, others are delivered in a sudden event. Other causes of failure are thermal stresses, drying and wetting cycles and chemical dissolution.
After a material fractures, the two faces of the fracture may be subject
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