The bearing imperativeness of a soil is the maximal load that it can bear before its fails by shearing or liquefaction . This value is the chief consideration in the design of founding . The received penetration test is a simple method acting for estimate the mechanical properties of a dirt at a likely construction site . Geotechnical engineer have accumulated data over several decades to allow a very empirical relation between SPT resultant role and a soil ’s aim pressure .

Things Needed

Step 1

Choose the precise web site for the examination . This may be on the surface of the ground or at the bottom of a bore hole if data is required for the grunge feature at greater depth in the background .

Step 2

Place the sample tube into the ground and forge it into the land so that its lower end is six column inch below the surface . Raise the hammer to a meridian of 30 inches above the top of the tube and allow to drop onto the thermionic valve . depend the number of hammering blows required for the tube to penetrate a further six inch into the ground .

Step 3

Lift the sample tube out of the land and empty its contents into wet - proof container . This stain will be analyze in later research lab tests . Reassemble the sample tubing and replace it into its last position in the land . Repeat the hammer blows from a 30 - foundation height above the pipe until it penetrates a further six inches into the ground . weigh the figure of blows . Lift the sample tube out of the primer again and empty its contents into another moisture - proof container for future analytic thinking .

Step 4

Calculate the ordinary number of mallet blows , N , required per six inches of filth incursion from the two tests . This is the sum of each number of blow counts divided by two . Each single hammer coke is equivalent to a bearing imperativeness of 2.1 bar , or 30.45 pounds per square inch , grant to empirical technology calculations . breed the N note value by either of the preceding gene to get the bearing pressure in the required unit of measurement .

Tip

Recognize that up to 65 percent of the energy in the mallet pin is lost during the fall is lost through bending , heat racket and friction . The empirical note value obtain from a simple SPT test must be refined by further investigations .

Warning

Beware that the SPT sample tube may run into rock’n’roll in the soil that are bombastic than its own diam . This innovate inaccuracy into the measurements .

References

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