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Soil boring test is important for foundation is designed

เริ่มโดย denichammy, กันยายน 19, 2013, 10:44:13 am

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denichammy

กันยายน 19, 2013, 10:44:13 am Last Edit: กันยายน 19, 2013, 11:16:24 am by denichammy
 :-\ Soil boring test are performed to discover the qualification of the soil test at the specific location. There are different procedures of soil boring test. After the soil samples are analyzed, a report is prepared recommending the type of foundation to be used. Before a foundation is decided, it is essential to assign the properties of the soil at the site of construction. This is done by conducting soil boring test.

In this  procedure, bore holes are made in the ground and the soil samples kept. Boring helps in obtaining  1) extent of each strata of soil/rock  2) nature of each layer and the engineering properties of the soils  3) location of ground water table. The depth and number of boreholes will depend upon the type of the structure and nature of the soil as obtained from preliminary examination. The depth of boreholes is commanded by the depth of the soil affected by the loading. As a rough estimate, it is recommendable to investigate the subsoil to a depth of at least twice the width of the forecasted largest size of the foundation. In case of a pile foundation, the depth of boring should extend into the bearing stratum.

Methods of Soil Boring Test

Auger Boring

The examination of the soil for ordinary buildings can be done by a post hole auger. The auger is held vertically and is driven into the ground by rotating its handle. At every 30 cm of depth, the auger is taken out and the soil samples collected.

Wash Boring

Wash boring is commonly used for boring in difficult soil. The hole is advanced by an auger and then a casing pipe is pushed to prevent the sides from caving in. A stream of water under pressure is forced through the rod into the hole. The loosened soil in suspension in water is collected in a tub.

Percussion Boring

In this method, the substrata is broken by repeated blows by a bit or chisel. Water is circulated in the hole and then the slurry is bailed out of the hole.

Core Drilling

When rocks are to be penetrated for examination, core drilling is resorted to. In this process, a hole is made by rotating a hollow steel tube having a cutting bit at its end.

Bearing Capacity

The bearing capacity of a soil is defined as the capacity of the subsoil to support the load of the structure without yielding. The bearing capacity of the soil depends upon the characteristics such as cohesion, friction, and unit weight. The bearing capacity can be determined in the field and also from the results of tests conducted in the laboratory on the soil samples.

The foundation is that part of the building which serves as a base and transmits the load to the soil. Before a foundation is designed, it is necessary to investigate the characteristics of the underlying soil. There are different methods to assess these characteristics.  :-[

resource : www.brighthubengineering.com