2 inch Automatic Trip Hammer SPT Sampler for Lithological Description
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 the British Standard BS EN ISO 22476-3, ASTM D1586 and Australian Standards AS 1289.6.3.1. A detailed description of SPT test and procedure can be found on the geotechnical data
Procedure
The test uses a thick-walled sample tube, with an outside diameter of 50 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 weight 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.
Detailed Product Description:
SPT Auto Trip Hammer is produced complying with the Standard Penetration Test (SPT) to BS 1377: Part 9: 1990.
The Automatic Trip Hammer is manufactured for complying with the Standard Penetration Test (SPT) to BS 1377: Part 9: 1990. SPT Drive Rods and a Split Tube Sampler are connected to base of the anvil, and driven into the ground by the falling weight.
The Automatic Trip Hammer comprises a weight of 63.5 kg complete with pick-up and self-tripping mechanism that ensures that the weight has a free-fall of exactly 760 mm. The inner shaft acts as a guide that permits the weight to drop with minimal resistance and ensures that the weight strikes the anvil squarely.
The SPT anvil thread usually is processed with a 1.1/2" B.S. whitworth to fit our standard SPT rods. Adaptors to other types of drill rod can be supplied on request. The overall length of the hammer is 2.6 m extended and 1.8 m when unextended. The total weight of the hammer is 110 kg.
Automatic Trip Hammer:
The Automatic Trip Hammer is designed for driving the Split Tube Sampler and conforms to the requirements of BS 1377: Part 9: 1990 for carrying out the Standard Penetration Test (SPT) or Super Heavy Dynamic Probing (DPSH).
The hammer consists of a weight of 63.5 kg complete with pick-up and self-tripping mechanism that ensures that the weight has a free-fall of exactly 760 mm.
The inner shaft acts as a guide that permits the weight to drop with minimal resistance and ensures that the weight strikes the anvil squarely.
The drive rods screw securely into the base of the anvil, which is supplied with either a 1.1/2" B.S. whitworth or BW rod box connection.
The hammer is supplied with a safety cross bolt which secures the sliding outer sleeve to the inner guide rod when the hammer is not in use or during transport.
The overall length of the hammer is 1.8 m unextended and 2.6 m when fully extended. The total weight of the hammer is 105 kg
The following spare parts are available:
Anvil
Weight
Pawls, Springs & Axles
Guide Rod
Outer Tube Assembly
Safety Cross Bolt
Seloc Pin (to secure anvil to guide rod)
