Standard Penetration Test (SPT) Procedure Aim To perform standard penetration to obtain the penetration resistance (N-value) along the depth at a given site. Equipment & Apparatus Tripod (to give a clear height of about 4 m; one of the legs of the tripod should have ladder to facilitate a person to reach tripod head.) Tripod … Read more
Strength and Modulus of Weathered Rock from SPT Values In the weathered rock it is difficult to drive the split sampler to the full specified depth as in soil. Hence we may estimate the strength and elastic modulus values of weathered rock by driving the spt apparatus for a fixed number of blows and find … Read more
Pile Load Capacity Calculation Using Standard Penetration Resistance This method of calculating pile load capacity in cohesion less soil (i.e. in sand) was suggested by Meyerhof. Meyerhof suggested the following equation, to calculate the ultimate pile load capacity in saturated sand, using standard penetration resistance (N). In the formula given below the 1st term gives … Read more
Step-by-Step Procedure for Calculation of Bearing Capacity from Standard Penetration Test Values or N-values Step-1 Perform standard penetration test on the location for which you want to calculate bearing capacity. This is done as per standard procedure given in IS-2131. Standard penetration test must be done at every 75 cm in vertical direction. Step-2 Decide … Read more
Blow counts are affected by operational procedures, by the presence of gravel, or cementation. They do not reflect fractures or slickensides in clay, which may be very important to strength characteristics. The standard penetration test results (N values) are influenced by operational procedures as given in the following table. No. Procedure Its Affect 1. Inadequate … Read more
There are many pitfalls associated with the standard penetration test. If these are not carefully avoided, the N-values collected from SPT are mere numbers rather than being useful indicators of soil parameters. Some of the precautions to be taken are: Results of standard penetration test are not reproducible in cohesion less soil below water level … Read more
The N-value observed during testing is not utilized directly in assessing soil properties. These values are corrected to account for The overburden pressure Dilatancy in saturated fine sands and silts Correction for overburden pressure The penetration resistance of soil depends on the over burden pressure. At deeper depth in-situ soil will have higher overburden pressure … Read more
This test involves the measurement of the resistance to penetration of a sampling spoon under dynamic loading The resistance is empirically correlated with some of the engineering properties of soil such as density index, consistency, angle of internal friction, bearing capacity etc. This test is useful for general exploration of erratic soil profile for finding … Read more