Heavy-Duty Dynamic Penetration Test

1. The heavy-duty dynamic penetration test equipment is mainly composed of three parts: the probe, the penetration rod and the penetration hammer. The penetration rod is generally 35 mm diameter thickened drill rod, and the penetration hammer weighs 63.5 kg.
2. Test procedure

(1) Before penetration, the probe frame should be installed stably, keeping the probe hole vertical.

(2) When penetrating, the penetrating hammer should be allowed to fall freely with a drop distance of 76 cm. The penetration depth, the penetration weight of a burst and the corresponding number of hammers should be recorded in time (usually 5 strokes are a burst) and each The measured number of hits N penetrated 10 cm.

(3) When the length of the probe rod is greater than 2 meters, the number of hammer strokes should be corrected by the following formula.

N63.5=d·N

In the formula, N63.5 is the number of hammers in the heavy dynamic penetration test.

d-The correction coefficient of the probe rod length, determined according to the table (0-20).

(Table 0-20) The correction coefficient d for the length of the penetration probe in the heavy dynamic penetration test

The number of medium, coarse, gravel, sand and round gravel, pebbles, and hammers below the groundwater level should be corrected by the following formula. N63.5=1.1N63.5+1.0

Where: N63.5 is the number of hammer strokes after the length of the probe rod is corrected.

3. Application of indicators

Determine the allowable bearing capacity of medium, coarse, gravel and sand according to the number of hammers of heavy dynamic penetration test according to Table 0-30.

Determine the allowable bearing capacity of the gravel soil according to the number of heavy-duty dynamic penetration hammers according to Table 0-40.

Table 0-30 The relationship between the number of hammers in the heavy dynamic penetration test and the allowable bearing capacity of medium, coarse, gravel and sand.

Note: 1L is the length of the probe rod in m, and the value of 2d is measured by automatic drop hammer.

Table 0-40 The relationship between the number of hammers in the heavy dynamic penetration test and the allowable bearing capacity of medium, coarse, gravel and sand.

Note: This table is generally applicable to alluvial and alluvial gravel soils. The d60 is not more than 30 mm, the unevenness coefficient is not more than 120, and the density is mainly slightly dense to medium dense.