1. Evaluation of undisturbed sampling techniques for pumiceous soils
M. Stringer, R. Orense, M. Cubrinovski, M. Pender, M.Asadi

2. Pumice Soils: a need to know!
Pumice is found in many areas of the North Island
Often encountered as an alluvial deposit, mixed with hard-grained materials.
Pumice grains are:
Lightweight
Highly crushable
Vesicular
Normal rules do not apply!
Wesley, L., et al. (1999)
Liu, et al. (2015)

3. Undisturbed Sampling
Choice of sampler is highly dependent on material type and state
Very difficult to obtain undisturbed samples of sandy (cohesionless) materials due to sidewall friction.
Three soil samplers trialled in Christchurch on silts, silty sands and clean sands.
Can these samplers be used to obtain high quality samples of soils containing pumice?
Frozen
samples
Piston/Core
samples
Yoshimi et al. (1994)

4. Finding the right site To examine performance of samplers requires:
Samples from each device taken at similar depths
Relatively thick deposits of target material
Target soils are within the capability of the sampler
Ideal site for available samplers
Shallow layers of silty sand material
No gravel
Modest penetration resistances
Very little spatial variation
Logged boreholes used as a screening
method to find most promising site for
sampling

5. What comes next Sampling to take place in next 4-6 weeks
Limited number of samples will be visually inspected on site for quality
Remaining samples sent to the Auckland and Christchurch for closer inspection & testing
Comparison against in-situ shear wave profiles from complimentary QuakeCORE project
Silty Sand

6. Opening Doors Develop expertise on sampling pumice soils
Understanding which tool is appropriate for use on geotechnical projects to define soil parameters.
Starting point for estimating properties using simple tools
Provide the basis for in-depth studies on similar volcanic materials.