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Upstream from the weir, up to thc uppcr end of the river section utilized, both banks are raised and reinforced by linings of gravelly sand materials, which havc becn filled in Iaycrs of approximativcIy 0.35 m; the core section has been compacted by means of sheepsfoot rollers. The embankments rest throughout on the solid gravelly subsoil, the top layers of silt having been removed previously. Concrete slabs provide a seal against seepage on the upstream slope; the joints of these slabs are closed with a bituminous sealing compound. Steel sheet pile walis below the foot of the concrete slabs pro-tect the embankment against piping. Immediately upstream from thc weir these Steel sheet piles were driven down to the rock surface, while farther upstream, their length graduałly decreascs as the height of the max. water Ievel above the sur-rounding land dccreases; in the uppcr parts there are no sheet piles. Seepage water is drained off through a ditch along the downstream foot of the embankments (Fig. 13). The embankments along both sides of the head race are built up in the same way as those along the river. The inside of the channel is entirely lined with concrete slabs whose joints are sealed with a bituminous compound.

The power station rests on compact tertiary sandstones and marls which outerop at a depth of 20-23 m underneath the water-bearing gravel deposits. The bearing capacity of this marł has been established as being about 12 kg/cm², whilst the maximum loading does not cxceed 7 kg/cm². The open ex-cavation for the foundation was surrounded by a ring of filter-wells by means of which the groundwater table could be lowered about 8.5 m. After foundation thc excavation pit had reached this level, a closed Steel sheet pile wali was driven down to the rock surface and a second drainage system installed inside this enclosed area after which the remaining excavation work was carried out down to the rock (Fig. 13). The construction of the taił race near its outlet into the river necessitatcd somc rock excavations; these were carried out in artificially drained open pits, partly enclosed by Steel sheet pile walls. In the entire upper part of this canal only gravel had to be excavated. The dcepening out of the bed of the river Aar below the outlet of thc canal called for some large-scale rock excavation under water.

In order to protect the thermal springs of Schinznach-Bad a bear-trap weir has been constructed across thc bed of the river for the purpose of maintaining a constant groundwater level in the vicinity of the springs.

After refreshments kindly provided by the Power Company of North-East Switzerland, the coaches will take the Conference Mcmbers back to Zurich via Brugg and Baden.

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Fig. 13 Cross scctions Wildegg-Brugg (sec Ićgcnde Fig. II)

Profils Wildegg-Brugg (legende Fig. 11)

revetus de dalles en beton dont les joints ont ete impermeabi-lises avec du mastic.

La centrale repose sur des mames et gres tertiaires compacts k 20-23 m au-dessous des graviers. La capacite portante des mames a ete estimee k 12 kg/cm² environ; cependant en aucun point la surcharge du batiment ne depasse 7 kg/cm². Pour permettre la fondation en fouille ouverte on a eu recours a une serie de puits filtrants disposes sur le pourtour de la fouille ce qui a permis d’abaisscr le niveau phreatiąue de 8,5 m cnviron. Lorsquc I’excavation eut atteint cette profondeur on battit des palplanches metalliques jusqu’au rocher et, ainsi protege, on proceda k l’excavation du materiau jusqu’au rocher.

La construction du canal de fuite a exige quelques excavations en rocher qui furent partiellement executees en fouilles entou-rees de palplanches. Dans le secteur superieur du canal on a eu k excaver des graviers seulement. L’abaissement du lit de l’Aar, en aval de la restitution, a exige l’excavation du rocher immerge sur une plus large echeile (Fig. 13).

Dans le but de proteger les thermes de Schinznach-Bad on construisit sur 1’Aar un barrage-toit dont lc remous attenue les variations du niveau phreatique dans le voisinage des thermes et en garantit ainsi le debit et la qualite.

Des rafraichissements seront offerts par les Forces Motrices du Nord-Est de la Suisse apres quoi les cxcursionnistes re-gagneront Zurich par Brugg et Baden.

Friday 21st August 1953 Seventh Session 09.00-09.45

Lecture by Dr. W. Eggenberger (Electro-Watt, Electrical and Industrial Management Co. Ltd., Zurich) on:

The Góschenenalp Dam project, Switzerland

Vendredi 21 aout 1953 Septi&me Session 09.00 a 09.45

Conference de M. D^r W. Eggenberger (Electro-Watt, Entre-prises Electriques et Industrielles, S. A., Zurich) sur:

The Góschenenalp Dam project, Switzerland (Le projet du barrage en terre de Góschenenalp, Suisse).

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