Soil Structure | What is Soil structure?
Soil formation is the most common term, which applies to all types of soils. It includes particle stratification, density, geometric and skeletal systems, inter-particle forces, and binding agents.
The term clay cloth is clearly used for the formation of soil-sized particles.
Formation of granular soils
In granular soils, the ratio of volume to surface area is large, so the mass-product energies are strong and the surface-derived electric forces are negligible.
Single-grain structures are formed when soil grains settle independently due to mass origin. Forces.
The individual particle is strong enough to withstand the usual stresses encountered experimentally.
Thus, the total physical properties of coarse-grained soils are a function of relative density and particle shape.
Packing is the term used for the synthesis of individual clay particles in granular soils. But the degree and shape of the particle affect packing.
For an idealized spherical particle, the minimum and maximum zero ratios * are 0.35 and 0.91, respectively.
But such a situation does not arise. However, ideal particle size distributions never exist in real soil. Potential packings are shown representing the upper (better-graded) and lower thresholds (poor-grade) Figure 1.10.
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Optimum packing leads to more particle contacts, more shear strength, less disposition, and more stability.
Formation of composite soils
The structure of the fine-grained composite soil can be fully described with an understanding of the inter-particle forces and the geometric arrangement of the particles or the fabric.
In cohesive soil deposits, the structural arrangement of individual particles or a group of particles at a microscopic scale is defined as the microstructure or micro fabric of the deposit.
The microstructure is fundamentally important in the general understanding of soil behavior. Large, often visible, structural features of composite deposits such as joints, cracks, rootlets, valves, silt and sandstones, and other breakdowns define the macrostructure or micro fabric of the deposit.
The macrostructure of cohesive deposits has a major empirical engineering influence on the behavior of whole soils.
The concepts of clay formation were previously proposed by Terzaghi (1925) and Casagrande (1932b).
In the process of sedimentation, the adsorbed water around the clay particles is squeezed, so that the particles gain more attractive forces, Terzaghey asserts.
The application of external pressure breaks the connections between the solid water shells, leading to the displacement and complete collapse of the structure.
The concept of Casagrande’s clay structure is that the coarse-grained skeleton is cemented together by a more compact “bond clay.” Intervals are partially filled with consolidated high-water-content “matrix clay.”
Remolding causes a mixture of matrix and bond clay and, thus, destroys the primary load-carrying structure.
Lambe (1953, 1958) essentially described structures as two extreme groups – flocculated and scattered. They are discussed below.
If two clay particles approach each other in suspension, repulsive forces are exerted by the van der Waals forces due to attractive forces and positively ionized adsorbed layers.
At low separation, the van der Waals forces dominate, and therefore the particles stick. However, there is a decrease in van der Waals forces with an increase in segregation.
If the adsorption layer is thin, the repulsive force is absent or insignificant, and the random motion of the particles makes them in contact. Moreover, the net repulsive force is larger when the particle is Faces come closer.
As a result, flocculating particles form the edge-to-face system. The group of such particles settles together rapidly. This process is called flocculation, and the structure formed is called flocculated structure.
Clays deposited under seawater have a higher cation density than thin suction water, resulting in a flocculated structure.
On the other hand, if the clay particles have a dense adsorption layer, repulsion is high and the particles slowly settle into free space, which then scatters.
This process is called dispersion, and it causes a particle-to-face orientation, called a scattered structure.
The smallest clay-particle-forming structure is called the flocculated or dispersed, first-order fabric unit. These small particles are usually assembled.
Van Olfen (1963) classified such particle clusters as primarily aggregated and eventually classified as flocculated or deflocculated, e.g.
The ideal soil structures of interest to civil engineers are shown in Figure 1.11.
The structural system in nature is more complicated due to the presence of massive particles. In addition to soil particles.
Interactions between single soil mineral particles are rare. Submit called domains separate clay particles aggregate or flocculate to form cryoscopic fabric components (Figure 1.12).
Domains cluster together to form submicroscopic groups called clusters. These submicroscopic groups are responsible for the inter-particle forces acting on small fundamental components.
Clusters combine to form peds that are macroscopic. Soil deposits that show no visible difference in macrostructure are said to be homogeneous or intact. Many clays are layered or hierarchical
Prime bedding flights.
The clay deposits formed in glacial melting-water lakes exhibit thin layers of silt, fine sand, and clay, and such deposits are known as weathered clay.
Hard clay exists in thin natural conditions with a network of hair cracks, joints, or cracks; Such as soil deposits They are called cracks. Cracks are formed by the release of high-pressure clay stress, previous earth movements, or volume changes caused by dehydration.
Well-defined macrostructure can significantly influence the engineering behavior of soil deposits.
The presence of cracks in the clay indicates weak planes and therefore low strength throughout the planes, Compared to intact soil deposits.
Apart from its low strength, fissured clays or laminated clays show greater leakage than intact clays, because of the preferred drainage line formed along the sludge cracks or bed planes.
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