IS 2131 is the correct Indian standard code that provides the procedure to carry out the Standard Penetration Test (SPT). The Standard Penetration Test is a widely used in-situ testing method in geotechnical engineering to determine the subsurface soil properties.

IS 2131 - Procedure for Standard Penetration Test (SPT):
The Indian Standard Code IS 2131 titled "Method of standard penetration test for soils" provides the guidelines for carrying out the SPT. The test involves driving a split-spoon sampler into the ground using a standard weight and drop height, and recording the number of blows required for each increment of penetration.

The code includes the following key points and procedures for conducting the SPT:

1. Apparatus and equipment: The standard penetration test apparatus consists of a split-spoon sampler, a driving hammer, a drill rod, and a tripod assembly to support the equipment during testing. The code specifies the dimensions and specifications of each component.

2. Preparation of borehole: Before conducting the test, a borehole is prepared at the desired location using drilling methods such as rotary drilling or percussion drilling. The code provides guidelines for the preparation of the borehole, including the required diameter and depth.

3. Driving of split-spoon sampler: The split-spoon sampler is driven into the borehole using a driving hammer. The code specifies the weight of the hammer and the drop height, which should be consistent throughout the test.

4. Blow count: The number of blows required to drive the split-spoon sampler a certain depth into the soil is recorded. The code provides guidelines for determining the blow count for each increment of penetration, considering factors such as the energy delivered and the resistance encountered.

5. Sampling and sample recovery: After completing the test, the split-spoon sampler is carefully removed from the borehole, and the soil sample inside it is collected for further laboratory testing. The code provides guidelines for the sampling and recovery of the soil sample.

Overall, IS 2131 serves as a comprehensive guide for conducting the Standard Penetration Test, ensuring standardized procedures and accurate results. It is essential for geotechnical engineers and professionals involved in soil investigation and foundation design.