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Five test methods for porosity of completely decomposed granite in Hong Kong
ARTICLE IN PRESS
International Journal of Rock Mechanics & Mining Sciences 41 (2004) 393–394
SINOROCK2004 Paper 1B 03
Five test methods for porosity of completely decomposed granite in Hong Kong Z.Q. Yuea,*, Y.J. Shangb, R.L. Hub, X.B. Tub b
a Department of Civil Engineering, The University of Hong Kong, Hong Kong, China Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029, China
Abstract Porosity is one of the basic soil parameters. Its value can be obtained from either a conventional physical test method or with other non-conventional methods, including the helium instrument, mercury injection, thin section measurement and scanning electronic microscopy (SEM) with digital plates for automatic processing. This paper attempts to examine the differences in porosity values due to the test methods. Taking Hong Kong completely decomposed granite (CDG) as an example, the results of the porosity values that are determined from the five methods are presented. The results reveal that the porosity values for one soil sample from the five methods are different. The porosity values can be ranked with the following large to small sequence: (a) (b) (c) (d) (e)
the the the the the
porosity porosity porosity porosity porosity
from from from from from
the conventional physical test method is ranked the largest; helium instrument the second; SEM measurement the third; mercury injection the fourth; and thin section measurement the smallest.
Furthermore, the porosity from the conventional physical test method is an absolute porosity with the largest value. The porosity from the helium instrument is an opening porosity. The porosity from mercury injection is an effective porosity. The above three porosity values represent the voids in a three-dimensional state. The thin section gives the voids on a two-dimensional plane section; while the SEM estimates the voids on a SEM image. The finding that the porosity from the thin section measurement is the smallest could be due to the fact that its identification is on the millimetre scale and the voids are observed among grains or crystals. More importantly, the porosity values from SEM are between the porosity values from the helium instrument and mercury injection methods. This finding has shown that the SEM method can be used to estimate the three-dimensional porosity values in meso and/or micro scales. Keywords: Porosity; Completely decomposed granite; SEM; Thin section; Mercury injection; Helium instrument
*Corresponding author. Tel.: +852-2859-1967; fax: +852-2559-5337. E-mail address: [email protected] (Z.Q. Yue). For full length paper see CD-ROM attached. doi:10.1016/j.ijrmms.2003.12.051
ARTICLE IN PRESS Z.Q. Yue et al. / International Journal of Rock Mechanics & Mining Sciences 41 (2004) 393–394
394 55 50 45
Porosity (%)
40 35 30 25 20
Physical Test Helium Instrument SEM Mercury Injection Thin Section
15 10 5 0 0
5
10
15
20
25
30
35 Sample No.
40
45
50
55
60
Fig. 1. Variations of porosity values from five test methods for completely decomposed granite soil samples.
65
70
International Journal of Rock Mechanics & Mining Sciences 41 (2004) 393–394
SINOROCK2004 Paper 1B 03
Five test methods for porosity of completely decomposed granite in Hong Kong Z.Q. Yuea,*, Y.J. Shangb, R.L. Hub, X.B. Tub b
a Department of Civil Engineering, The University of Hong Kong, Hong Kong, China Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029, China
Abstract Porosity is one of the basic soil parameters. Its value can be obtained from either a conventional physical test method or with other non-conventional methods, including the helium instrument, mercury injection, thin section measurement and scanning electronic microscopy (SEM) with digital plates for automatic processing. This paper attempts to examine the differences in porosity values due to the test methods. Taking Hong Kong completely decomposed granite (CDG) as an example, the results of the porosity values that are determined from the five methods are presented. The results reveal that the porosity values for one soil sample from the five methods are different. The porosity values can be ranked with the following large to small sequence: (a) (b) (c) (d) (e)
the the the the the
porosity porosity porosity porosity porosity
from from from from from
the conventional physical test method is ranked the largest; helium instrument the second; SEM measurement the third; mercury injection the fourth; and thin section measurement the smallest.
Furthermore, the porosity from the conventional physical test method is an absolute porosity with the largest value. The porosity from the helium instrument is an opening porosity. The porosity from mercury injection is an effective porosity. The above three porosity values represent the voids in a three-dimensional state. The thin section gives the voids on a two-dimensional plane section; while the SEM estimates the voids on a SEM image. The finding that the porosity from the thin section measurement is the smallest could be due to the fact that its identification is on the millimetre scale and the voids are observed among grains or crystals. More importantly, the porosity values from SEM are between the porosity values from the helium instrument and mercury injection methods. This finding has shown that the SEM method can be used to estimate the three-dimensional porosity values in meso and/or micro scales. Keywords: Porosity; Completely decomposed granite; SEM; Thin section; Mercury injection; Helium instrument
*Corresponding author. Tel.: +852-2859-1967; fax: +852-2559-5337. E-mail address: [email protected] (Z.Q. Yue). For full length paper see CD-ROM attached. doi:10.1016/j.ijrmms.2003.12.051
ARTICLE IN PRESS Z.Q. Yue et al. / International Journal of Rock Mechanics & Mining Sciences 41 (2004) 393–394
394 55 50 45
Porosity (%)
40 35 30 25 20
Physical Test Helium Instrument SEM Mercury Injection Thin Section
15 10 5 0 0
5
10
15
20
25
30
35 Sample No.
40
45
50
55
60
Fig. 1. Variations of porosity values from five test methods for completely decomposed granite soil samples.
65
70