What is meant by n value of soil?

The number or blows required for 12 inches penetration resistance of the soil. It is generally referred as the ‘N’ value and measured in blows/unit penetration. The Standard penetration test ( SPT ) is widely used to get the bearing capacity of soil directly at a certain depth.

How do you find the n value in SPT?

SPT N value for cohesive soils with r 2 as 0.998 is represented by following equation.

1. C = – 2.2049 + 6.484N (r^{2} = 0.998) (1)
2. C = – 16.5 + 2.15N (r^{2} = 0.998) (2)
3. \varphi = 7N\, \left( {r^{2} = 0.998}\, \right);for\, N \le 4. (3)
4. \varphi = 27.12 + 0.2857N\, \left( {r^{2} = 0.998} \right);\,for \,N = 4 to 50. (4)

What is the N value of SPT explain the corrections to be applied to the observed value of N?

This leads to higher value of N-value which is unsafe. Therefore when SPT is performed in saturated silts and fine sands and if the observed N-value is more than 15, a correction has to be applied to reduce the observed values. This correction is applied on the N-value corrected for over burden pressure (N’).

What is the purpose of SPT?

The standard penetration test, commonly known as ‘SPT’, was developed to provide geotechnical engineering properties for foundation design purposes. The test is carried out within a borehole. The results can be used to determine the relative density, bearing capacity, and settlement of granular soil.

What is N value in civil engineering?

The sum of the number of blows required for the second and third 6 inches of penetration is termed the “standard penetration resistance” or the “N-value”. In cases where 50 blows are insufficient to advance it through a 150 mm (6 in) interval the penetration after 50 blows is recorded.

What is N value in pile foundation?

Context 1. to it, since N-value is an indirect measure of relative density hence angle of internal friction for cohesionless soil and cohesion for cohesive soil, hence, N-value can be used to determine the skin friction and end bearing for pile.

What is N value in geotechnical engineering?

The N-value provides an indication of the relative density of the subsurface soil, and it is used in empirical geotechnical correlation to estimate the approximate shear strength properties of the soils.

What is N value SPT?

The SPT (N) value provides information regarding the soil strength. SPT (N) value in sandy soils indicates the friction angle in sandy soils and in clay soils indicates the stiffness of the clay stratum.

What is N value correction?

With the increase in the depth of the soil, the confining pressure also increases. Hence, to account this the value of ‘N’ obtained from the test are corrected to a standard effective overburden pressure. The corrected value of ‘N’ is. Nc = CN N. Here CN is the correction factor for the overburden pressure.

Which of the following n factor has the widest range of values?

Nγ factor
4. Which of the following N factors has the widest range of values? Explanation: The Nγ factor has the widest suggested range of any value of N factors.

How do you calculate bearing capacity from n value?

This results in a bearing pressure of n = na = 270 kN/m2, and a base area of The general route for establishing the allowable bearing pres- sure is as follows. (1) Divide the ultimate bearing capacity by a factor of safety (typically 3.0), to obtain the safe bearing capacity.