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APPENDIX C

SHOE <3ł

19 mm

(2)

SPLIT TUBĘ

t* *

RECOMMENDED STANDARD FOR THE SPT TEST 1. SCOPE

1.1 This method describes a procedurę for determining the resistance of soils to the penetration of a split-tube sampler and ob-taining disturbed samples of the soil in a borehole for Identification purposes. The test provides information on soil varia-bility and stiffness.

The test is madę by dropping a free falling hammer weighing 63*5 kg onto the drill rods from a height of 0.76 m. The number of blows N necessary to achieve a penetration of 0.30 m (below the seating drive) is regarded as the penetration resistance. (This test was developed in the USA and has been widely known as the "Standard Penetration Test".)

coupung

(1)    .4 VENTS 13mm

^J ^DIAMETER MIN |4| $35 mm

25 mm DlAMETER STEEL BALL

NOTES 11) THE SPLIT TUBĘ MAY CONTAIN A

UNER WITH AN INTEflNAl DIAMETER OF 35 mm

<2) THE CORNERS AT (2I MAY BE SLlGHTLY ROUNCEC

I3I IN CRAVELLY SOUS THE 0RIV'NG SHOE

MAY 0E REPIACEC BY A S0LI0 STEEL CONE OF 5* mm 0'AMETER AKO 60 OEGREE ANGLE

TOLERANCES:    U) * 1 mm

(5) t 1 mm

2. APPARATUS

2.1    Boring eąuipment

2.1.1    The boring eąuipment shall be capable of providing a reasonably clean hole to ensure that the penetration test is per-formed on relatively undisturbed soil.

2.1.2    When wash boring, a side-discharge drilling bit should be used but not a bottom-discharge drilling bit. Jetting through an open-tube sampler with water and then testing when the desired depth is reached shall not be permitted.

2.1.3    The process of jetting through an open-tube sampler with drilling mud and then testing when the desired depth is reached may be used, provided the flow and pressure of the drilling mud does not disturb the soil at the depth of the test drive (see clause 3.2.2).

2.1. When shell and auger boring, the drilling tool shall have a diameter which is not morę than 90# of the internal diameter of the casing or of the borehole if no casing is used.

2.1.5    When drilling in soil that will not allow a hole to stay open, casing or drilling mud shall be used.

2.1.6    The diameter of the borehole should be between 60 and 200 mm approximately.

2.2 Split-barrel sampler

2.2.1    The sampler shall have the dimen-sions shown in Fig. 1.

2.2.2    The drive shoe shall be of hardened Steel . It shall be replaced when it becomes significantly damaged or distorted. (See notę 1 clause 5 .)

Fig. 1 Cross section of the SPT sampler.

2.2.3 The central section of the sampler shall be of Steel and of split-tube construc-tion to allow examination and easy removal of the sample.

2.2 0 The sampler head shall have four 13 mm (minimum) diameter vent ports and shall contain a 25 mm Steel bali check valve seated in an orifice of not less than 22 mm diameter which is located below the vent ports to improve sample recovery when there is water in the borehole. The bali and its seat shall be constructed and maintained so as to give a watertight seal when the sampler is withdrawn. (See notę 2 clause 5.)

2.3 Sampler rods

2.3.1    The rods used for driving the sampler should have a stiffness eąual to or greater than type AW drill rods 03.7 mm O.D., 3^.1 mm I.D. and approximately 6 kg/m weight).

For holes deeper than 15 m steadies shall be used at intervals of 3 m, or alternatively rods with a stiffness eąual to or greater than type BW drill rods (5^.0 mm O.D., MO mm I.D. and approximately 8 kg/m weight).

(See notę 3 clause 5).

2.3.2    Tolerance on straightness: when measured over the whole length of the rod by rolling against a straightedge, the maximum deviation shall not be greater than 1 in 1000.

2.3-3 The rods should be tightly coupled.

20 Drive weight assembly

2 0.1 The drive weight assembly shall com-prise:

115