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