Becker Penetration Test
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发布时间：2022-04-23 21:06
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时间：2023-10-09 16:39
Soils that contain a large percentage of gravel and those that contain cobbles or boulders create problems for most in-situ test methods. Often，the in-situ test device is not able to penetrate through such soils ( it meets refusal) or the results are not representative because the particles are about the same size as the test device. Frequently，even conventional drilling equipment cannot penetrate through these soils.
One method of penetrating through these very large-grained soils is to use a Becker hammer drill. This device， developed in Canada， uses a small diesel pile-driving hammer and percussion action to drive a 135 to 230 mm ( 5. 3 － 9. 1 in) diameter double-wall steel casing into the ground. The cuttings are sent to the top by blowing air through the casing. This technique has been used successfully on very dense and coarse soils.
The Becker hammer drill also can be used to assess the penetration resistance of these soils using the Becker penetration test，which is monitoring the hammer blow-count. The number of blows required to advance the casing 300 mm ( 1 ft) is the Becker blowcount，NB. Several correlations are available to convert it to an equivalent SPT N value. One of these correlation methods also considers the bounce chamber pressure in the diesel hammer.
