The three aspects with respect to micro-properties of the completely decomposed granite (CDG) as the distribution of pore radius

particle diameters and mineral content play a major role in determining the engineering geological features of the CDG. In theoretical study and engineering practice the following parameters are used to describe the characteristics in the three aspects: large

middle and small

micro-pores

gravel

sand

silt and clay particles

three major mineral components (quartz

feldspar and clay minerals)

etc. How large of the variation range of these indices in one certain size of trial pits and blocks? How about the correlation of the indices in the three parts? As factors of soil structure

how large of their weight ratios once the soil structure is to be under considerations? In this paper

a total of 51 nos. specimens from 18 nos. blocks from three trial pits of two slopes in Kowloon

Hong Kong

were taken as examples. The test is carried out by means of the mercury injection

particle size distribution and X-ray diffraction. After preliminary analysis

it is found that the CDG with coarse particle portions is very different from that with fine particle portions. The former belongs to gravel soil and sandy gravel soil

and some of it is gravel-bearing soil

with more big pores

more quartz and clay minerals. The latter belongs to gravel-bearing soil

some is fine sandy soil and sub-sandy soil

with more micropores

more feldspars. Variations of feldspar and clay mineral contents are inverse to each other. Furthermore

the interaction matrix is applied for analysis of the correlation of the 9 indices. As a result

it is found that the correlation coefficient varies to a great extent. According to the value of the correlation coefficient

those indices with larger ones are: gravel and sand particles (0.948)

big pores and middle-small pores (0.846)

quartz and feldspar (0.827)

feldspar and clay minerals (0.747). If the soil structure factors are under considerations

the 9 indices are in sequence of weight ratio from large to small: micro-pores

feldspar

clay minerals

sandy particles

gravel

large pores

middle-small pores

silt and clay particles

quartz. These indices

quantified after their correlations and weight ratios

provide bases for the study of micro-features in detail and classifications of the CDG

and perhaps act as one of the basement for the constitution equations of microstructure mechanics of soils to be built.