lines, including a micro-wave wireless link to the Tsengwen Reservoir De- velopment Commission at Taipei, have been installed to connect with the dial system at Tainan City.
Surveying. Prior to the various engineering works, a system of trian- gulation surveying and bench marks was established. Topographic survey- ing for damsite, rivers, spillway, diver- sion tunnels and housing area, aerial survey for prospecting of construction materials in the nearby region and a location survey for access roads were also conducted.
Geological exploration. Holes have been drilled and pilot tunnels dug at the damsite, spillway, diversion tun- nels, powerhouse and afterbay weir. Underground strata have been detected by seismographic methods and rock samples chemically analysed.
To date more than 165 holes have been drilled a total length of 9,942 metres, and 27 pilot tunnels have been dug to a total length of 3,094 metres.
Material testing. Samples of earth and rock for building the dam have been collected and their triaxial com- pression and consolidation properties will be tested by the U.S. Reclamation Bureau. Studies, including crushing and rolling tests, have been made for possi- ble use of materials from the diversion tunnels as fill for the dam.
Tests on the physical and chemical properties of the aggregates for con- crete mixing, the relation between strengths and water to cement ratio, and the effects of additives and fly ash in concrete and their economic analysis aimed at an optimum formula- tion, have been made by the Cheng Kung University at Tainan. A field survey of the quantity and kinds of filling material available is also in hand. Hydraulic model tests. The overall model tests are to be made by Koei Company of Japan. The aim of these tests is to ascertain the net flow of water from the spillway and diversion tunnels and to devise the stabilizing measures. The exact location of the powerhouse will be determined to achieve the best efficiency.
Hydraulic model tests for the in- dividual structures, including the spill- way, diversion tunnels, afterbay weir and Tungkow intake, have been carried out by the Water Resources Planning Commission of MOEA, and the result- ing report has been checked by Ameri- can advisers, and experts from Koei.
Aggregate preparation and concrete mixing plant. This began operation at the end of 1968. It stands at a point near the outlet of the No. 1 diversion
tunnel and includes equipment for crushing and sizing concrete aggregates and a 4.5 cu. metre automatic concrete mixer. The plant has a capacity of 200 metric tons an hour of aggregates and 100 cu. metres an hour of concrete.
Other important works now being pursued by the Engineering Bureau in- clude land purchasing, migration from villages to be submerged, contracting for water sale, procurement of con- struction machinery and materials, soil conservation, hydrological data record- ing and rural economy improvement.
Tunnel construction
Work on the diversion tunnels was started in October 1967 at four stations the intakes and outlets. In the first stage the upper semicircle of the tun- nels is being excavated.
The No. 2 tunnel was bored through on October 27, 1968, one year after commencement. The errors in survey for centre line of the No. 2 tunnel were found to be 6 mm vertical, 8 mm lateral and 56 mm for the station mark. According to schedule the No. 2 tunnel will be completed by October 1969 when the foundation for the dam will be started. No. 1 tunnel will be completed by May 1970
The design data of the tunnels is: Maximum flood – 7,980 c.m.s. Maximum discharge rate 4,430 c.m.s. at an upper stream water level of 160.2 metres.
Thickness of concrete lining - 2.70 metres at the openings and generally 1.00 to 0.80 metres according to the the strata strength.
Tunnel supports standard 10 in. H-beams are used to support the upper part of the tunnels at a spacing of 0.75 to 1.5 metres.
Access road
were used per cu. metre of rock. Average daily progress of the excava- tion is 2.85 metres.
After the blasting there is a settling period. Then the waste rock is re- moved with loaders and dump trucks to a disposal area. The bare rock over the tunnel is immediately supported with 10 in. H-beams, preformed in shops on a roller bending machine. The gap between the steel support and rock is cushioned with timber wedges and steel purlins are set at the supports so prevent rock falling. A concrete beam is poured at the footing to con- nect the steel supports.
The time for a working cycle from hole drilling to support setting requires 480 minutes. Therefore, three cycles are arranged in two 12-hour shifts, though five cycles of 288 minutes each have been achieved. Time distribution for the 480-minute cycle is 100 minutes for drilling, 90 minutes for dynamite Underground excavation – 400,000 filling and wiring, 30 minutes for air freshening, 130 minutes for rock re-
Open excavation 450,000 cu.
metres.
cu. metres.
metres.
L
Concrete to be cast - 160,000 cu. moving, 80 minutes for support setting
and 50 minutes for waiting time.
Construction machinery
Temporary cofferdam at the intakes of the tunnels - 1,200,000 cu. metres.
The main contractor for the con- struction work is Retired Servicemen Engineering Agency. A work force of 1,200 is presently engaged.
Blasting of the upper half of the tunnel in a cross section area of about 81 sq. metres is done with 130 drilled holes. The holes have a depth of 1.20 to 1.50 metres and are filled with a total of 80 to 90 kg of dynamite. Each blasting may loose 210 to 260 cu. metres of rock.
In October 1968 an average of 0.62 kg of dynamite and 1.44 fuses
For construction of the diversion tunnels the following construction ma- chinery is at present in use:
Air compressors of 150 h.p. and 200 h.p. 10 sets; blowers of 125 h.p.
3 sets; various pumps with 2 in. to 6 in. discharge openings - 41 sets; air hoists 10 sets; leg drills with 36 mm to 40 mm bits 86 sets; rocker shovels 4 sets; pay loaders - 3 sets; dump trucks 21 sets; pneumatic concrete placers 3 sets; vibrators
16 sets; agitator trucks 6 sets; and centipede
―
-
―
conveyors for concrete - 2 sets.
Far East BUILDER, May 1969
39