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SOIL MECHANICS - CHAPTER 2

Phân loại 2,1 Kích thước hạt Đất thường được phân loại thành các loại khác nhau. Trong nhiều trường hợp các loại khác nhau cũng có các tính chất cơ học khác nhau. Một phân khu đơn giản của đất trên cơ sở kích thước hạt của các hạt tạo thành đất. Vật liệu hạt thô là thường ký hiệu là sỏi và vật liệu tốt hơn là cát. Để có sỏi áp dụng thống nhất thuật ngữ đã được thỏa thuận quốc tế để xem xét các hạt lớn hơn 2 mm, nhưng nhỏ hơn 63 mm. Các hạt lớn. | Chapter 2 CLASSIFICATION 2.1 Grain size Soils are usually classified into various types. In many cases these various types also have different mechanical properties. A simple subdivision of soils is on the basis of the grain size of the particles that constitute the soil. Coarse granular material is often denoted as gravel and finer material as sand. In order to have a uniformly applicable terminology it has been agreed internationally to consider particles larger than 2 mm but smaller than 63 mm as gravel. Larger particles are denoted as stones. Sand is the material consisting of particles smaller than 2 mm but larger than 0.063 mm. Particles smaller than 0.063 mm and larger than 0.002 mm are denoted as silt. Soil consisting of even smaller particles smaller than 0.002 mm is denoted as clay or luthum see Table 2.1. In some countries such as the Netherlands the soil may also contain Soil type min. max. clay 0.002 mm silt 0.002 mm 0.063 mm sand 0.063 mm 2 mm gravel 2 mm 63 mm Table 2.1 Grain sizes. layers of peat consisting of organic material such as decayed plants. Particles of peat usually are rather small but it may also contain pieces of wood. It is then not so much the grain size that is characteristic but rather the chemical composition with large amounts of carbon. The amount of carbon in a soil can easily be determined by measuring how much is lost when burning the material. The mechanical behavior of the main types of soil sand clay and peat is rather different. Clay usually is much less permeable for water than sand but it usually is also much softer. Peat is usually is very light some times hardly heavier than water and strongly anisotropic because of the presence of fibers of organic material. Peat usually is also very compressible. Sand is rather permeable and rather stiff especially under a certain preloading. It is also very characteristic of granular soils such as sand and gravel that they can not transfer tensile stresses. The particles can only .