Hydrological characteristics of some volcanic materials as affected by particle size distribution and internal porosity

Figures & data

Table I. Particle size distribution, Mid Particle Diameter (D₅₀) and Gradation Index (D₉₀/D₁₀) of volcanic raw materials and a silica sand meeting the USGA specifications for texture.

		Lapillus	Pumice	Zeolite	Sand
	mm	^_______________________________________ g kg^−1 ^_______________________________________
Gravel	>4	8	12	49	0
	2–4	168	150	340	0
Very coarse sand	1.0–2.0	114	241	254	8
Coarse sand	0.5–1.0	105	218	94	183
Medium sand	0.25–0.5	129	148	71	690
Fine sand	0.15–0.25	115	55	37	99
Very fine sand	0.106–0.15	76	29	32	12
	0.053–0.106	132	41	41	5
Silt + Clay	<0.053	153	106	82	3
Mid Particle Diameter (D50)		0.3	0.8	1.6	0.4
Gradation Index (D90/D10)		75.7	47.2	49.3	2.5

Table

a. Lapillus	raw material	Lp-Raw
b. Pumice	raw material	Pu-Raw
c. Zeolite	raw material	Ze-Raw
d. Silica sand	graded sand	Ss-Graded
e. Lapillus	graded sand	Lp-Graded
f. Pumice	graded sand	Pu-Graded
g. Zeolite	graded sand	Ze-Graded
h. Silica sand	coarse sand fraction (0.5–1.0 mm)	Ss-Coarse
i. Lapillus	coarse sand fraction (0.5–1.0 mm)	Lp-Coarse
j. Pumice	coarse sand fraction (0.5–1.0 mm)	Pu-Coarse
k. Zeolite	coarse sand fraction (0.5–1.0 mm)	Ze-Coarse
l. Silica sand	medium sand fraction (0.25–0.5 mm)	Ss-Medium
m. Lapillus	medium sand fraction (0.25–0.5 mm)	Lp-Medium
n. Pumice	medium sand fraction (0.25–0.5 mm)	Pu-Medium
o. Zeolite	medium sand fraction (0.25–0.5 mm)	Ze- Medium

Figure 1.  Water retention curves (volumetric moisture content in m³ m⁻³) of silica sand (Ss) meeting USGA specifications for texture and volcanic materials: lapillus (Lp), pumice (Pu) and zeolite (Ze). Volcanic materials are reported as Raw (texture of the materials as available on production site) or Graded (obtained by reassembling the fractions in the same proportions of the reference Ss).

Figure 2.  Available water (m³ m⁻³) of lapillus, pumice, zeolite and silica sand. For each volcanic material four bars are displayed corresponding (left to right) to raw material (texture as available on production site), graded material (obtained by reassembling the fractions in the same proportions of the reference silica sand used in the trial), coarse sand fraction (0.5–1.0 mm particle size) and medium sand fraction (0.25–0.5 mm particle size). For the silica sand data bars refer respectively to USGA-compliant material for texture and coarse and medium sand fractions as defined above.