(Tổng hợp) BS 1377 – phương pháp phân loại và gọi tên đất

TCBS_grain_size

Very coarse
soils
BOULDERS > 200 mm
COBBLES 60 – 200 mm
  Coarse
soils
G
GRAVEL
coarse 20 – 60 mm
medium 6 – 20 mm
fine 2 – 6 mm
S
SAND
coarse 0.6 – 2.0 mm
medium 0.2 – 0.6 mm
fine 0.06 – 0.2 mm
Fine
soils
M
SILT
coarse 0.02 – 0.06 mm
medium 0.006 – 0.02 mm
fine 0.002 – 0.006 mm
C  CLAY < 0.002 mm
Sieve mesh
size (mm)
Mass
retained (g)
Percentage
retained
Percentage
finer (passing)
14.0 0 0 100.0
10.0 3.5 1.2 98.8
6.3 7.6 2.6 86.2
5.0 7.0 2.4 93.8
3.35 14.3 4.9 88.9
2.0 21.1 7.2 81.7
1.18 56.7 19.4 62.3
0.600 73.4 25.1 37.2
0.425 22.2 7.6 29.6
0.300 26.9 9.2 20.4
0.212 18.4 6.3 14.1
0.150 15.2 5.2 8.9
0.063 17.5 6.0 2.9
Pan 8.5 2.9
TOTAL 292.3 100.0

 

TCBS_particle_size

The soil comprises: 18% gravel, 45% coarse sand, 24% medium sand, 10% fine sand, 3% silt, and is classified therefore as: well-graded gravelly SAND

Low plasticity wL = < 35%
Intermediate plasticity wL = 35 – 50%
High plasticity wL = 50 – 70%
Very high plasticity wL = 70 – 90%
Extremely high plasticity wL = > 90%

 

[The range of Gs for common soils is 2.64 to 2.72]

BS description system

A recommended protocol for describing a soil deposit uses nine characteristics; these should be written in the following order:

compactness
loose, dense, slightly cemented
bedding structure
homogeneous or stratified; dip, orientation
discontinuities
spacing of beds, joints, fissures
weathered state
degree of weathering
colour
main body colour, mottling
grading or consistency
well-graded, poorly-graded; soft, firm, hard
SOIL NAME
GRAVEL, SAND, SILT, CLAY; (upper case letters) plus silty-, gravelly-, with-fines, etc. as appropriate
soil class
(BSCS) designation (for roads & airfields)  SW = well-graded sand
geological stratigraphic name
(when known)  London clay

Not all characteristics are necessarily applicable in every case.

Example:
(i) Loose homogeneous reddish-yellow poorly-graded medium SAND (SP), Flood plain alluvium
(ii) Dense fissured unweathered greyish-blue firm CLAY. Oxford clay.

British Soil Classification System

The recommended standard for soil classification is the British Soil Classification System, and this is detailed in BS 5930 Site Investigation. Its essential structure is as follows:

Soil group Symbol Recommended name
Coarse soils Fines %
GRAVEL G GW 0 – 5 Well-graded GRAVEL
GPu/GPg 0 – 5 Uniform/poorly-graded GRAVEL
G-F GWM/GWC 5 – 15 Well-graded silty/clayey GRAVEL
GPM/GPC 5 – 15 Poorly graded silty/clayey GRAVEL
GF GML, GMI… 15 – 35 Very silty GRAVEL [plasticity sub-group…]
GCL, GCI… 15 – 35 Very clayey GRAVEL [..symbols as below]
SAND S SW 0 – 5 Well-graded SAND
SPu/SPg 0 – 5 Uniform/poorly-graded SAND
S-F SWM/SWC 5 – 15 Well-graded silty/clayey SAND
GPM/GPC 5 – 15 Poorly graded silty/clayey SAND
SF SML, SMI… 15 – 35 Very silty SAND [plasticity sub-group…]
SCL, SCI… 15 – 35 Very clayey SAND [..symbols as below]
Fine soils >35% fines Liquid limit%
SILT M MG Gravelly SILT
MS Sandy SILT
ML, MI… [Plasticity subdivisions as for CLAY]
CLAY C CG Gravelly CLAY
CS Sandy CLAY
CL <35 CLAY of low plasticity
CI 35 – 50 CLAY of intermediate plasticity
CH 50 – 70 CLAY of high plasticity
CV 70 – 90 CLAY of very high plasticity
CE >90 CLAY of extremely high plasticity
Organic soils O [Add letter ‘O’ to group symbol]
Peat Pt [Soil predominantly fibrous and organic]

 

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