Features of design of foundations on sandy soils

In engineering Geology rocks are divided into 3 major groups: sedimentary, igneous and metamorphic. A more detailed division into subspecies can solve various tasks for the design and construction of buildings and structures. Sandy soils are non-cohesive rocks. The particle size of 0.05-2mm, clay component up to five percent.

Foundation Design for sandy soil is carried out taking into account all its properties. Physico-mechanical properties of sandy rocks are determined by their origin. The widespread are alluvial Sands with different textural and structural features. The particle sizes of the sand facies are saying about their affiliation. Deposited near the shores of the largest particles and the farther and deeper in the sea the finer particles are deposited and sorted better. Such regularity of nature for sand accumulated in the riverbed. They have a low dispersity, are well sorted and rounded, with good permeability.

Sands of ancient floodplains and finely grained, with horizontal and oblique layering, with an admixture of organic matter and clay content. Because of increasing clay and reducing the particle size of the Sands decreases permeability and increase compressibility.

Sands left after the melt waters of glaciers granular and dispersed with different properties, often with fragments of pebbles, gravel, boulders. The higher porosity Sands in a more finely, grained. The permeability of these Sands is not large, it increases with increasing particle size.

Sandy rocks of diverse mineral composition and particle size distribution under pressure can move into floaters. Floaters have a high water-holding capacity, which is associated with negligible permeability of these rocks. When the humidity increases in such species can occur dangerous deformation. Geotechnical properties of sandy soils depends on the availability of the coarse-grained and fine-grained particles, the presence of a dusty component.

Sands of alluvial Genesis was formed at the expense connected mainly with secondary waters more ancient sediments. Usually they are more sorted, more homogeneous composition, more dispersed. This is typical of most coastal Sands of the seas.

Granulometric composition of Sands is investigated by sieve analysis. According to sieving on  the particle size determines the soil name.

the Design of buildings and structures on sandy soils is based on the results of the engineering and hydrogeological studies. Take into account the experience of building in similar conditions, physico-mechanical properties of overlying rocks. Select the Foundation type, the Foundation to meet the expected changes of soil properties and water level over time. Provided the necessary engineering activities.

Density of sand determined in the laboratory on selected monoliths or on field results of probing the Sands. Under special conditions you can use the density obtained by calculation, by comparing soils in various States. It is impossible to apply the method of dynamic sensing when water-saturated Sands and silt.

For engineering facilities is necessary to determine the bearing capacity and deformations (deflections, precipitation, etc.). Therefore, on the basis of laboratory data calculate the following parameters: the inner angle. friction, UD clutch, the modulus of deformation. Modulus of deformation is usually determined by test or dies with prisionera. For buildings and structures 2-4 class allowed determination of the deformation modulus of Sands in the laboratory using the compression test. For structures 1 and 2 of the class you want to map sensing data with test stamps.

In the lab counting beats grip and angle EXT. friction. Strength characteristics of Sands can be determined by triaxial compression or can be determined in the field by shifting soil, caving, lifting.

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