Two Mechanisms of Tufa Formation in the Cement Grouting. Tunnels at æ'ujiangdu Hydropower Station of Guizhou*. LlU Zai-Hua (ååå) and HE Dian-Bin ...
CHINESE SCIENCE BULLETIN
Vo l. 39 No. 17
September
1 佣4
Two Mechanisms of Tufa Formation in the Cement Grouting Tunnels
at 明'ujiangdu
Hydropower Station of Guizhou*
Ll U Zai-Hua
(刘再华)
(lnstilute uf Karst
Gω'logy ，
Re∞ ived
Keywords: tufa
formati吨 karst
and HE Dian-Bin MGMR , Guilin
(贺殿彬)
541()(风‘ PRC)
March 18. 1994
processes, agíug of concrete , Wujiangdu
Hy曲。 power Stati锢， Guizh 皿
Wujiangdu Hydropower Station of Guizhou is one of the biggest hydroelectric pr叮 ects bui1t in karst areas of China. It has a dam 165 m high. with a capacity of 630 , 000 kW. lts electric energy production i.s 3.34 billion kW. h坷. Since its launching in 1979, the statìon has contributed a lot to the economy in Southwest China. ln the ∞Uïse of the station' s establishl l1ent , huge cUïtains ‘ lûcated in the dalll base and on both banks of the Wujiang River , were built by means of high pressure cement grouting to prevent seriou5 leakage. Practice shows that they are leakproof on the whole. But in the tunnels for curtain grouting formed many tufa deposits that resembled soda straw (F ig. 1) and stalagmite (Fig. 2). Th is raises the question: are these secondary deposits related to the aging of grouting curtain or a normal phenomenon in karst areas? U nderstanding this question is important and helpful in predicting the trend of leakage-preventing of curtains and in taking effective measures. In addition , it may provide a new field for karst study.
Eig
,.
l SOda
si川("COrabsorbing"
type)
Fi g_ 2. Slalagmite ("COradsorbing" type)
Project supported by the National Natural Science Foundation of China
No. 17
口丑NESE
SCIENCE BULLETIN
1469
1 Studv Method Study methods are as follows: (i) Temperature , conductivity , pH value ，也气 HC0 3 ， CO~- and OH - of water were measured in situ[l]. 。i)K+ ， Na\Ca气 Mg2 十 ， Cl一， HC0 3, SO~- ， CO~- and OH 一 of water samples
were analyzed in laboratory according to standard procedures. (iìì) The composition (ð 13C) of carbon isotope of tufa , limestone and water samples were measured in laboratory. (iv) Saturation index (SI) of minerals and partial pressure (Pco z) of CO 2 in water were calcu1ated by computer software SOLMINEQ. 88[勾. 2 Major Study Results Tables 1- 3 show the major 'res u1ts in the study. Table 1
Hydr∞:hemistry
and Carbon Isotope of
Surfa臼 Water
and Groundwater at
Na+
Ca2 +
SO~-
HCO;
cot
(吨(1)
(吨(1)
(吨 (1)
(吨(1)
(吨 (1)
1. 45
4.52
ω .42
67. ∞
159.96
o.∞
o. ∞
1. 49
2.54
117.23
101. 58
272.87
pH
K+
Surface water
8.30
Groundwater
7.70 ∞nductivity
hydrochemi也l
type HC0 3 • S04.Ca
SIca )
SIpb)
Surface water
(J.ls /cm) 353
+0.ω
一 10.07
Groundwater
596
HC0 3 • S04.Ca
+0.30
一 1 1.1 1
纱，
tYI览
b), T:he saturation index
of 臼lαte
7.57 12.56
L. W._A 8 )
B. W. 刹时 B. W._A b)
7.17 12.02
川 -刊uANA
LLBB
m一
可
mwwwwωnductivity WIcm) 499 5797 到6
1587
U四 M川川州附
L. W._Nal
pH
•
o. ∞
ðl3C
PCOt 10- 6)
(%0 ) 一 8.67
694 9810
一 13.42
and Carbon Isotope of Water From Leakage and Borehole in the
Tunnels at Wujiangdu Hydropower Station Water type
o. ∞
(X
hydrochemical
Ca2+ (mg(l) 99.34 399. ∞
91.1 7 135.32 SIc
什川 -叫 UNωm
Hydrω:hemistry
.
OH
and portlandite respectively.
rω-mMMM
Table 2
Site
(吨 (1)
Wãter type
Water
Wujiangdu 凶m
SIp
coj-
OH(mgjl)
HC0 3 (mgjl)
(吨11)
290.02
o. ∞
。ω
38 1. 74
o. ∞
39.68
282.46
o. ∞
o.ω
o. ∞
34.72
11 3. 19
PC02 ( x 10")
Fτ一
type HCOrCa OH-Ca HC0 3-Ca
+0.44 +3.17
一 10.82
7α泪
(%0 ) 12.74
一1. 05
。
一 2 1. 14
+0. ∞
11.57
173∞
一 1 1. 34
OH-Ca
+ 1. 77
1. 82
。
23.01
a) L. W.-N-- leakage wa也r with "N" type issues from limestone fissures or from iron-made pipe through ∞nαete wall , whereas L. W. 喃A-一一 leakage water with "A" type 1S mainly related to ωncrete. b) B. W.-A ←一- borehole water with "A" type 臼 re1ated to ærnent groutingαIItain， whereas B. W-N 一 borehole water with "N" type does not ωntact with curtain aα:o rding to drilling data.
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Vol. 39
TabJ.e 3 Carbon Isotope and Deposition Rate of Tufa in the Tunnels at Wuiiandu Hvdropower Station Deposit type (jI3C
