PROJECT SUMMARY | OCTOBER 10, 2016
Low-pressure penstock for a river power plant in the Swiss Alps
The given location and geometry of the water intake at the river as well as the power house and water outlet at an existing channel determined the tangents of both ends of the pen-stock. Due to the maximum overburden of 14,3 m / 47 ft, the geology and groundwater conditions as well as the existing terrain (forest, creek), closed-shield microtunneling was the only applicable construction method.Due to hydraulic conditions and sensitive structures above and below ground, the optimal alignment for the penstock turned out to be an S-shaped curve in the situation with a steep vertical curve at the end to minimize the depth of the receiving pit and therefore the dewatering systems resulting in significant cost savings.Crossing the railway line in a depth as small as 2 x OD re-quired a real-time settlement monitoring, which was suc-cessfully conducted and operated by VMT GmbH.The tight radius at the end of the alignment and the large pipe diameter led to joint deflection angles with a minimum gap with on the inside of the curve of only 15 mm / 0,59 in and a maximum on the outside of the curve of up to 75 mm / 2,95 in.
AT A GLANCE
Project name Kraftwerk Rufi
Project location Hätzingen GL Switzerland
Purpose Penstock
Completed 2016
Specialties – Old arch channel crossing– Railway crossing /
settlement monitoring– Small overburden
Total length 534 m / 1752 ft
ID 3200 mm / 126,0 in
OD 3800 mm / 149,6 in
Alignment 3-D compound S-curve
Min. radius of curvature
260 m / 853 ft
Pipe material reinforced concrete
Pipe length 3 m & 4 m / 9,8 ft & 13,1 ft
Min. overburden below arch channel
0,6 m / 2 ft
Min. overburden below railway
7,45 m / 24,4 ft
Geology & groundwater
Saturated debris; highly perme-able, lose sandy / silty gravel with cobbles and boulders. Ground-water level 4 m / 13 ft above crown.
Hydraulic Joint JC250 / double loop. Admissible jacking force 22 000 kN / 2472 t
Guidance system VMT SLS Microtunneling LT
TBM Herrenknecht AVND3000
Owner Hefti-Hätzingen AG, Switzerland
Consultant / Designer Jackcontrol AG, Switzerland
Contractor K-Boringen, Belgium
Pipe manufacturer Berding Beton GmbH, Germany Gollwitzer GmbH, Germany
SITUATION: POWER HOUSE AND DRIVE PIT (BOTTOM RIGHT),
WATER INTAKE AND RECEIVING PIT (TOP LEFT)
Jackcontrol AG Buchholzstrasse 50 | 8750 Glarus | Switzerland Phone +41 (0)55 650 20 20 | Fax +41 (0)55 650 20 30info @ jackcontrol.com | www.jackcontrol.com