Khao Laem Dam ia a 90 m high concrete faced compacted rock filled dam. The damsite is in an area of cavernous limestone and treatment to prevent water loss through the right abutment involves the driving of six grouting galleries as the access to fill the concrete into the cavities and to execute the grouting work. Within the abutment close to the dam an area of ungroutable microfractured limestone was encountered. A concrete diaphragm cutoff wall was therefore required to be constructed between the galleries. Development of the design, construction precedures, costs and program of this wall are discussed.
Der Khao Laem Damm ist ein 90 m hoher Steinschuettdamm mit einer wasserseitigen Betonmembrane. Die Sperrstelle liegt in einem Gebiet karstigen Kalksteines. Um Wasserverluste durch das rechte Dammwiderlager zu vermeiden, ist der Ausbruch von 6 Galerien durch das Massiv vorgesehen, mit der Absicht, Kavernen zu finden und mit Beton auszufuellen, oder das Gebirge mit Zement zu injizieren. Im rechten Widerlager, unmittelbar am Anschluss des Dammes, steht eine Zone mit uninjizierbarem, zerbrochenem Kalkstein an. Eine Betonabdichtungswand (Schlitzwand) ist hier zwischen den Galerien vorgesehen. Im folgenden Artikel werden Entwicklung dieser Wand, Konstruktionsverfahren, Kostenanalyse sowie Bauprogramm beschrieben.
Le Barrage de Khao Laem est une digue en enrochement avec une couche amont impermeable en beton. Il est situe dans une region de calcaire karstique at afin d''eviter des pertes d'' eau a travers l''appui droit, on a decide l''execution de six galeries pour remplir des cavernes de beton et pour executer des injections. Une zone composee de calcaire fracture et non injectable se trouve dans l''appui droit en contact avec la digue. L''execution d''un diaphragme en beton y a ete choisie entre les galeries. Le developpement de l''etude, les procedes de construction, les couts et le programme de realisation de ce diaphragme sont discutes.
The Khao Laem Project is in central west Thailand on the Quae Noi River. The dam-site was selected after study of several alternative sites and was extensively investigated over a period of about six Years.
The general layout of the project is shown in Figure 1. The main features are:
A gated chute spillway at the left abutment with a capacity of 3 200 m3/s.
A concrete gravity intake structure next to the spillway with three power intakes and an irrigation outlet.
Three 6.3 m diameter, steel pressure conduits each 240 m long.
A 300 MW capacity surface power station.
A concrete faced rockfill embankment 90 m high with a total fill volume of about 8.0 ' 106 m3.
A temporary diversion channel requiring the excavation of approximately 4 ' 106m3.
A diversion tunnel of 7.0 m internal diameter and 470 m length.
A right abutment cut-off comprising over 22 km of grouting galleries.
The development of the project has been made very difficult by the widespread occurrence of karstic weathering in the mainly calcareous rocks of the Thung Song and Ratburi Groups which could give rise to reservoir leakage problems. In addition to conventional grouting, a 50 m deep concrete diaphragm wall is provided along part of the upstream toe of the dam.
(Figure in full paper)
The right abutment is composed of massive limestone of the Ratburi Group which is karstic. Treatment involves driving six grouting galleries each almost 4 km long, spaced vertically at 14 m. Between these galleries and below the bottom one, closely spaced holes are being drilled and water pressure tested to locate cavities and determine the extent of the required grouting. Cavities observed in the galleries and intersected by the drill holes will be cleaned out and filled with concrete.
The boundary between the Thung Song Group and the Ratburi Group is faulted and consists of an ungroutable microfractured limestone which includes areas of blocky material surrounded by clay filled joints. This paper discusses the treatment of this area.