SPT Automatic Drop Hammer
SPT Automatic Drop Hammer Standard Test Method for Penetration Test and Split Barrel Sampling of soils
Standard penetration test
This article is about testing of geotechnical properties of soil. For testing of computer systems, see Penetration test.
The standard penetration test (SPT) is an in-situ dynamic penetration test designed to provide information on the geotechnical engineering properties of soil. The test procedure is described in ISO 22476-3, ASTM D1586[1] and Australian Standards AS 1289.6.3.1.
Standard penetration test N values from a surficial aquifer in south Florida.
Procedure
The test uses a thick-walled sample tube, with an outside diameter of 50.8 mm and an inside diameter of 35 mm, and a length of around 650 mm. This is driven into the ground at the bottom of a borehole by blows from a slide hammer with a mass of 63.5 kg (140 lb) falling through a distance of 760 mm (30 in). The sample tube is driven 150 mm into the ground and then the number of blows needed for the tube to penetrate each 150 mm (6 in) up to a depth of 450 mm (18 in) is recorded. The sum of the number of blows required for the second and third 6 in. 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. The blow count provides an indication of the density of the ground, and it is used in many empirical geotechnical engineering formulae.
Purpose
The main purpose of the test is to provide an indication of the relative density of granular deposits, such as sands and gravels from which it is virtually impossible to obtain undisturbed samples. The great merit of the test, and the main reason for its widespread use is that it is simple and inexpensive. The soil strength parameters which can be inferred are approximate, but may give a useful guide in ground conditions where it may not be possible to obtain borehole samples of adequate quality like gravels, sands, silts, clay containing sand or gravel and weak rock. In conditions where the quality of the undisturbed sample is suspect, e.g., very silty or very sandy clays, or hard clays, it is often advantageous to alternate the sampling with standard penetration tests to check the strength. If the samples are found to be unacceptably disturbed, it may be necessary to use a different method for measuring strength like the plate test. When the test is carried out in granular soils below groundwater level, the soil may become loosened. In certain circumstances, it can be useful to continue driving the sampler beyond the distance specified, adding further drilling rods as necessary. Although this is not a standard penetration test, and should not be regarded as such, it may at least give an indication as to whether the deposit is really as loose as the standard test may indicate.
The usefulness of SPT results depends on the soil type, with fine-grained sands giving the most useful results, with coarser sands and silty sands giving reasonably useful results, and clays and gravelly soils yielding results which may be very poorly representative of the true soil conditions. Soils in arid areas, such as the Western United States, may exhibit natural cementation. This condition will often increase the standard penetration value.
The SPT is used to provide results for empirical determination of a sand layer's susceptibility to soil liquefaction, based on research performed by Harry Seed, T. Leslie Youd, and others.
Correlation with soil mechanical properties
Despite its many flaws, it is usual practice to correlate SPT results with soil properties relevant for geotechnical engineering design. SPT results are in-situ field measurements, and not as subject to sample disturbance, and are often the only test results available, therefore the use of correlations has become common practice in many countries.
Problems with SPT
The Standard Penetration Test recovers a highly disturbed sample, which is generally not suitable for tests which measure properties of the in-situ soil structure, such as density, strength, and consolidation characteristics. To overcome this limitation, the test is often run with a larger sampler with a slightly different tip shape, so the disturbance of the sample is minimized, and testing of structural properties is meaningful for all but soft soils. However, this results in blow counts which are not easily converted to SPT N-values – many conversions have been proposed, some of which depend on the type of soil sampled, making reliance on blow counts with non-standard samplers problematic.
Standard Penetration Test blow counts do not represent a simple physical property of the soil, and thus must be correlated to soil properties of interest, such as strength or density. There exist multiple correlations, none of which are of very high quality.[2] Use of SPT data for direct prediction of liquefaction potential suffers from roughness of correlations and from the need to "normalize" SPT data to account for overburden pressure, sampling technique, and other factors.[3] Additionally, the method cannot collect accurate data for weak soil layers for several reasons:
The results are limited to whole numbers for a specific driving interval, but with very low blow counts, the granularity of the results, and the possibility of a zero result, makes handling the data cumbersome.
In loose sands and very soft clays, the act of driving the sampler will significantly disturb the soil, including by soil liquefaction of loose sands, giving results based on the disturbed soil properties rather than the intact soil properties.
A variety of techniques have been proposed to compensate for the deficiencies of the standard penetration test, including the Cone penetration test, in-situ vane shear tests, and shear wave velocity measurements.
Cone penetration test
Geotechnical investigation
Soil mechanics
Geotechnical engineering
Exploration Investigation
On-site
Cone penetration test Standard penetration test Monitoring well piezometer Borehole Crosshole sonic logging Nuclear densometer test Static load testing
Testing
Laboratory
Atterberg limits California bearing ratio Direct shear test Hydrometer Proctor compaction test R-value Sieve analysis Triaxial shear test Hydraulic conductivity tests Water content tests
Soil
Materials
Clay Silt Sand Gravel Peat Permafrost Loam Loess
Properties
Soil classification Hydraulic conductivity Water content Void ratio Bulk density Thixotropy Reynolds' dilatancy Angle of repose Cohesion Porosity Permeability Specific storage
Mechanics
Effective stress Pore water pressure Shear strength Overburden pressure Consolidation Compaction Shear wave Lateral earth pressure
Foundations
Shallow Deep Bearing capacity Dynamic load testing Pile integrity test Wave equation analysis Statnamic load test
Retaining walls
Gabion Ground freezing Mechanically stabilized earth Pressure grouting Slurry wall Soil nailing Tieback
Stability
Slope analysis mass wasting landslide Deformation monitoring automated
Earthquakes
Soil liquefaction Response spectrum Seismic hazard Ground–structure interaction
Geosynthetics
Geotextile Geomembrane Geosynthetic clay liner Cellular confinement
Numerical analysis
Plaxis GEO5 SEEP2D STABL SVFlux SVSlope UTEXAS
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Standard penetration test
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SPT Energy Measurements: Manual vs. Automatic Hammer
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SPT Automatic Drop Hammer: Environmental, Geophysical
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Energy Efficiency and Rod Length Effect in SPT Drilling
Evaluation of SPT Hammer Energy Variability
NOTES on the STANDARD PENETRATION TEST
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Soil Sampling Tools - Drilling World
SPT Hammer Energy Ratio versus Drop Height
Spt Hammer - Spt Hammer Manufacturers, Suppliers
1.8m - 2.6m Automatic SPT Hammer Standard Penetration
Effect of SPT Hammer Energy Efficiency in the Bearing
Spt Hammer Complete
Evaluation of SPT energy for Donut and Safety hammers
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Mobile Drill Tooling Catalog UPDATED 2015 Reduced
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STANDARD PENETRATION TEST
Subsurface Exploration Using the Standard Penetration Test and the Cone Penetrometer Test
Subsurface Exploration Using the Standard Penetration Test
Site Exploration, Site Characterization, Subsurface Exploration, Drilling, Standard Penetration Test, Cone Penetrometer
The Standard Penetration Test (SPT) and Cone Penetrometer Test (CPT) have become industry standards for subsurface geotechnical investigations using small diameter (<8-in. [20-cm]) borings and soundings. Both procedures have evolved over a period of 100 and 70 years, respectively, and have been adopted as ASTM standards. Each procedure has certain advantages over the other, but both can elicit incorrect data under particular subsurface conditions that are often overlooked, depending on the experience of field personnel operating or logging the tests. This paper seeks to explain the operative assumptions employed in both procedures, highlight the various corrections that are commonly employed, and warn the reader of common errors in interpretation.
The article concludes by stating that, under most conditions, the joint employment of SPT and CPT together has the greatest potential for characterizing sites correctly.
ASTM D1586 - 11
Standard Test Method for Standard Penetration Test (SPT) and Split-Barrel Sampling of Soils
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