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Use of geotextiles in hydraulic works in Heilongjiang, China
Geotextiles and Geomembranes 6 (1987) 315-318
Technical Note Use of Geotextiles in Hydraulic Works in Heflongjiang, China
A BSTRA CT In this technical note, the authors discuss hydraulic division work in the Heilongfiang Province in China. In the erosion prevention, outstanding results were obtained with the geotextile DS450-2a.
The Southern Division Work in Heilongjiang Province, People's Republic of China, is located in the west of Heilongjiang, on the left bank of the Nen River. A filling reservoir is made up of 33 dikes, with a total length of 50 km. Water is divided from the Nen River, at a maximum flow rate of 120 m3/s. The division work consists of seven parts, namely: --division intake ---division cut ---division gate ---canal --filling reservoir ---discharge channel ---discharge gate The division works, begun in 1977 and completed in 1987, involved 107 m 3 of earth works, 16 × 104 m 3 rockfill and 60 × 103 m 3 of concrete. The completed project irrigates an area of 2.104 km 2, provides a fishing area of 2.104 km 2 and a reed area of 3.7 × 104 km 2. The dikes of the filling reservoir are located in a region of highly dispersive soil. However, some earth dikes (Nos 2, 16, 17, 18, 19 and 21) were built using dispersive soil and early in construction discovery was made of several hundred erosion pockets caused by rainwater. 315
Geotextiles and Geomembranes 0266-1144/87/$03.50 O 1987 Elsevier Applied Science Publishers Ltd, England. Printed in Great Britain
316
Hong You- Wei, Sheng Shou- Tian
In order to prevent dispersive clay erosion, many tests have been carried out on soil samples taken from the field. This research has included the use of the pinhole test, lime-stabilised tests, filter tests and geotextile pinhole tests. These tests confirmed that dispersive clay has poor erosion resistance, owing to a high natrium content which reduces the attractive forces between soil particles. On wetting-up, or immersion in water, these weak attractive forces are destroyed and the soil particles separate. Even in still water, clay particles will go into suspension. The properties of the dispersive soil, which has a CL classification, are shown in Table 1. Pinhole dispersion tests were carried out under a 5 cm head and these showed the flow clouding after a few seconds with suspended particles. The pinhole eroded to a diameter of 3-5 cm with much loss of soil. The degree of dispersion was found to be 49% and the natrium content 85.7%. To prevent erosion, a series of geotextiles was evaluated using the geotextile pinhole test. Excellent results were obtained using DS450-2a (code
TABLE 1 Properties of the Dispersive Soil
Grain size (ram)
>0.05 % Finer
Grain classification
0-05-4).005 <0.005 <0.002
37
28
35
27
w~
w~
i~
SG
(%)
(%)
(%)
2.69
31
17
14
TABLE 2 Geotextile Properties of DS450-2a
Description Mass per unit area (g/m 2) Thickness (mm) Grab tensile strength (kg/5 cm) Elongation (%) Puncture resistance (kg/2 cm) Grab tensile strength after freezing and thawing Permeability Kv (m/s) Pore size (mm)
Vahw 450 3-4 M/D 39-7 X/M 36-4 M/D 67-8 X/M 67-8 120 M/D 37.0 X/M 35-2 6.2 x 10-5 4_3-1 10
Use of geotextiles in hydraulic works in Heilongjiang, China
I
/~1~-~ ~ 1
I j'~T~Ik,,~ v 136.5
317
v135-5(0.2"/.)
Fine $a
Fig. 1. Typical section of Red Soil Mountain Dike.
1
3
~ I .~._t___~ 2 ~---
v
4.0
~:¢b
Fig. 2. Typical section ofdik e No. 16.
no.) with no soil particle loss or enlargement of the pinhole. The geotextile is 100% polypropylene and needle-punched. Other properties of the geotextile are summarised in Table 2. Details of typical dikes are given in Figs 2 and 3 where geotextiles were used to prevent erosion under wave action and soil dispersion. Figure 1 shows the 'Red Soil Mountain Dike' which is 5.5 m high and 400 m long. The fill for this dike was fine sand with the properties shown in Table 3. This dike has faced severe floods over a three-year period and has performed well. Dikes constructed using dispersive clays are typified by Dike No. 16, shown in Fig. 2. This dike is 4.0 m high and 400 m long. TABLE 3 Red Soil Mountain Dike Typical Soil Properties
Grain size (mm) >0"25 0.25-0- l 0. l-0.05 0.05-0-005 <0-005 % Finer
10.0
71.0
9.0
6.5
3.5
D60
D10
(mm)
(ram)
Cu
(m/s)
0.21
0-052
4.04
8.10
Kv
318
Hong You-Wei,ShengShou-Tian TABLE 4 Comparative Costs
Method of treatment
Comparative cost (%)
Encapsulation using non-dispersive clay Dosing reservoir with lime Soil stabilisation using ALSO4 Lime stabilisation upstream with sand filters downstream Geotextile filters
368 802 538 174 100
Geotextiles h a v e been widely used in Heilongjiang Province with more than 300 000 m 2 employed in hydraulic works. On the Southern Division project, some 7000 m 2 of geotextile have been used in association with fine sand fill to act as a filter layer under concrete slabs. Similarly, 16 000 m 2 have been used with dispersive clays as filters and antidispersion layers. Geotextiles have fulfilled their design requirements and have proved economical. This is reflected in Table 4, which shows comparative costs of various solutions considered for treating dispersive soils in dike construction. Hong You-Wei & Sheng Shou-Tian
Heilongjiang Provincial Research Institute of Water Conservancy, 18 Qing-Bin Road, Harbin, Peop&'s Republic of China (Received 4 January 1988; accepted 8 February 1988)
Technical Note Use of Geotextiles in Hydraulic Works in Heflongjiang, China
A BSTRA CT In this technical note, the authors discuss hydraulic division work in the Heilongfiang Province in China. In the erosion prevention, outstanding results were obtained with the geotextile DS450-2a.
The Southern Division Work in Heilongjiang Province, People's Republic of China, is located in the west of Heilongjiang, on the left bank of the Nen River. A filling reservoir is made up of 33 dikes, with a total length of 50 km. Water is divided from the Nen River, at a maximum flow rate of 120 m3/s. The division work consists of seven parts, namely: --division intake ---division cut ---division gate ---canal --filling reservoir ---discharge channel ---discharge gate The division works, begun in 1977 and completed in 1987, involved 107 m 3 of earth works, 16 × 104 m 3 rockfill and 60 × 103 m 3 of concrete. The completed project irrigates an area of 2.104 km 2, provides a fishing area of 2.104 km 2 and a reed area of 3.7 × 104 km 2. The dikes of the filling reservoir are located in a region of highly dispersive soil. However, some earth dikes (Nos 2, 16, 17, 18, 19 and 21) were built using dispersive soil and early in construction discovery was made of several hundred erosion pockets caused by rainwater. 315
Geotextiles and Geomembranes 0266-1144/87/$03.50 O 1987 Elsevier Applied Science Publishers Ltd, England. Printed in Great Britain
316
Hong You- Wei, Sheng Shou- Tian
In order to prevent dispersive clay erosion, many tests have been carried out on soil samples taken from the field. This research has included the use of the pinhole test, lime-stabilised tests, filter tests and geotextile pinhole tests. These tests confirmed that dispersive clay has poor erosion resistance, owing to a high natrium content which reduces the attractive forces between soil particles. On wetting-up, or immersion in water, these weak attractive forces are destroyed and the soil particles separate. Even in still water, clay particles will go into suspension. The properties of the dispersive soil, which has a CL classification, are shown in Table 1. Pinhole dispersion tests were carried out under a 5 cm head and these showed the flow clouding after a few seconds with suspended particles. The pinhole eroded to a diameter of 3-5 cm with much loss of soil. The degree of dispersion was found to be 49% and the natrium content 85.7%. To prevent erosion, a series of geotextiles was evaluated using the geotextile pinhole test. Excellent results were obtained using DS450-2a (code
TABLE 1 Properties of the Dispersive Soil
Grain size (ram)
>0.05 % Finer
Grain classification
0-05-4).005 <0.005 <0.002
37
28
35
27
w~
w~
i~
SG
(%)
(%)
(%)
2.69
31
17
14
TABLE 2 Geotextile Properties of DS450-2a
Description Mass per unit area (g/m 2) Thickness (mm) Grab tensile strength (kg/5 cm) Elongation (%) Puncture resistance (kg/2 cm) Grab tensile strength after freezing and thawing Permeability Kv (m/s) Pore size (mm)
Vahw 450 3-4 M/D 39-7 X/M 36-4 M/D 67-8 X/M 67-8 120 M/D 37.0 X/M 35-2 6.2 x 10-5 4_3-1 10
Use of geotextiles in hydraulic works in Heilongjiang, China
I
/~1~-~ ~ 1
I j'~T~Ik,,~ v 136.5
317
v135-5(0.2"/.)
Fine $a
Fig. 1. Typical section of Red Soil Mountain Dike.
1
3
~ I .~._t___~ 2 ~---
v
4.0
~:¢b
Fig. 2. Typical section ofdik e No. 16.
no.) with no soil particle loss or enlargement of the pinhole. The geotextile is 100% polypropylene and needle-punched. Other properties of the geotextile are summarised in Table 2. Details of typical dikes are given in Figs 2 and 3 where geotextiles were used to prevent erosion under wave action and soil dispersion. Figure 1 shows the 'Red Soil Mountain Dike' which is 5.5 m high and 400 m long. The fill for this dike was fine sand with the properties shown in Table 3. This dike has faced severe floods over a three-year period and has performed well. Dikes constructed using dispersive clays are typified by Dike No. 16, shown in Fig. 2. This dike is 4.0 m high and 400 m long. TABLE 3 Red Soil Mountain Dike Typical Soil Properties
Grain size (mm) >0"25 0.25-0- l 0. l-0.05 0.05-0-005 <0-005 % Finer
10.0
71.0
9.0
6.5
3.5
D60
D10
(mm)
(ram)
Cu
(m/s)
0.21
0-052
4.04
8.10
Kv
318
Hong You-Wei,ShengShou-Tian TABLE 4 Comparative Costs
Method of treatment
Comparative cost (%)
Encapsulation using non-dispersive clay Dosing reservoir with lime Soil stabilisation using ALSO4 Lime stabilisation upstream with sand filters downstream Geotextile filters
368 802 538 174 100
Geotextiles h a v e been widely used in Heilongjiang Province with more than 300 000 m 2 employed in hydraulic works. On the Southern Division project, some 7000 m 2 of geotextile have been used in association with fine sand fill to act as a filter layer under concrete slabs. Similarly, 16 000 m 2 have been used with dispersive clays as filters and antidispersion layers. Geotextiles have fulfilled their design requirements and have proved economical. This is reflected in Table 4, which shows comparative costs of various solutions considered for treating dispersive soils in dike construction. Hong You-Wei & Sheng Shou-Tian
Heilongjiang Provincial Research Institute of Water Conservancy, 18 Qing-Bin Road, Harbin, Peop&'s Republic of China (Received 4 January 1988; accepted 8 February 1988)