ASTM D1586 Standard Test Method for Standard Penetration Test (SPT) and Split-Barrel Sampling of Soils

ASTM D1586 Introduction

ASTM D1586 sets up a standardized procedure for conducting the test in soil borings with the use of a split-barrel sampler, which is actuated through a drop hammer. The standard penetration test is perhaps the most popular in-situ geotechnical testing method. It generates both qualitative and quantitative data by integrating both blow count measurements with maximum disturbed soil sample retrievals. The straightforward nature, flexibility, and historical data record, along with the aids linked to SPT, qualify it as a beneficial instrument used in exploratory site testing, bearing capacity assessments, and the determination of any alterations in subsurface conditions.

ASTM D1586 Test Method

ASTM D1586 Equipment and Sample Preparation

ASTM D1586 Results and Interpretation

The N-value, based on the number of hammer blows needed to force any sampler 300 mm (12 in) into the ground after being seated, is the primary outcome of the SPT. The higher the N-values, the denser or more compacted the soils, and low N-values imply loose or soft ones. The values may be empirically correlated with soil category, bearing capacity, relative density, unconfined compressive strength, and liquefaction potential. The samples obtained through the test can also be categorized visually or through laboratory testing to further assist in soil profiling.

ASTM D1586 Related Test Methods

ASTM D2487 is used in the unified soil classification system, and ASTM D7263 is used for estimating moisture content and density. 

ASTM D1586 Applications and Industry Use

In the construction of projects such as buildings, bridges, dams, roads, and retaining structures, SPT forms a significant pillar in geotechnical site investigations. The engineers may utilize the SPT information to determine workable bearing pressures, settlement likelihood, the seismic site class, and the liquefaction danger.

ASTM D1586 Materials Commonly Tested

This method is very broad and may be applied to soils that are considered cohesive and non-cohesive, such as clay, silt, sand, gravel, and fill. The test is not suitable for very soft soils or highly compacted gravels; an alternative test may be needed.

ASTM D1586 Common Challenges and Troubleshooting

The accuracy of SPT is distorted by the rod length, effectiveness of hammer energy, and the disturbance in the boreholes or uneven driving. Standardization of results is often obtained through corrections (e.g., overburden pressure or energy ratio). Data reliability is enhanced by maintaining the level hammer drop height, clean equipment, and straight boreholes. It is also advisable to standardize energy transfer by using automatic hammers.

ASTM D1586 Safety and Best Practices

Drilling and testing underground are to be conducted with site safety. Staff should be equipped with personal protective devices and ensure that all tools and machines are properly maintained before use and used safely with sampling devices.

ASTM D1586 Importance

The wheeled probes by this method are still one of the fundamental instruments in the study of the subsurface. It is a uniform and field-oriented approach to soil behavior understanding and foundation and earthwork design. Its simple implementation, being associated with soil conditions, and universal acceptance establish it as the key instrument in day-to-day and even in critical geotechnical processes.