OR/14/052 Field tests

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Boon, D, Kirkham, M, and Scheib, A. 2014. Physical properties of till deposits from Anglesey, north west Wales. British Geological Survey Internal Report, OR/14/052.

Lightweight dynamic cone penetrometer

The undrained shear strength (Cu) of the soils was investigated by performing in situ strength tests using a variable energy dynamic penetrometer, Panda2 lightweight penetrometer.

The Panda2 dynamic cone penetrometer measures the in situ dynamic cone resistance (in MPa) of the soil through which it is passing and can be used for indirect estimation of in situ relative density and undrained shear strength (Cu) and for stratigraphic mapping of soils in the shallow subsurface. The test is undertaken by driving a 4 cm2 sacrificial steel cone on the end of a set of 0.5 m long threaded steel rods using a fixed weight (hand held) hammer through the target deposit. The Panda2 measures the velocity of the hammer impact on the head of the rods and the depth of cone penetration in order to determine the dynamic cone resistance (qd) using a modified form of the Dutch Formula (Langton, 1999)[1]. The Panda2 is capable of reaching depths of up to 6 m in soils with a resistance up to 20 MPa. It is relatively lightweight (20 kg) and readily portable thereby making it ideal for testing soils in situ, particularly where access is restricted, such as on coastal, river, landslide scarp and quarry exposures.

A more detailed explanation of the Panda Penetrometer testing methodology and correlations with other dynamic and static cone penetration tests can be found in Langton (1999)[1] and Amor et al (1999)[2]. One limitation of the technique in coarse-gravel and cobble/boulder rich tills is that the cone can become obstructed by coarse grained stronger particles (cobbles & boulders) and this can limit penetration depth, and effect interpretation of results.

Details of in situ strength testing (Panda2 soundings)

Full raw Panda2 data and cone resistance plots are proved in Appendix 2.

Table 3    Details of Panda penetrometer testing
Site Name Profile name Termination Depth (m) Unit Orientation
Cemlyn Bay P001 0.109 Sand lens — NB Invalid test due to brittle soil fracture Vertical
P002 0.122 Sand lens Vertical
P003 0.292 Sand lens Horizontal
P004 0.234 Sand lens Vertical
P005 0.049 Grey till Vertical
P006 0.330 Sand lens, grey till at base Vertical
P007 0.333 Grey till Vertical
Beaumaris P008 0.592 Grey till Vertical
P009 1.306 Grey till Vertical
Start height 5 cm lower than P008
P010 0.299 Red till Vertical
P011 0.321 Red till Vertical
P012 0.204 Red till Vertical
Port Nobla P014 0.294 Red till Vertical
P015 0.479 Red till Vertical

References

  1. ↑ 1.0 1.1 Langton, D D. 1999. The Panda lightweight penetrometer for soil investigation and monitoring material compaction. Ground Engineering, p.33–37.
  2. ↑ Amor, S J, Burtwell, M H, and Turner, A S. 1999. Panda dynamic cone penetrometer assessment. Transport Research Laboratory, Crowthorne.
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