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well as limestone. Thus the so-called south ramp resulted in a typical hill-side construction with many slopes, deep side cuttings and numerous tunnels, high walls and other structures.
Rock slides
The slope, with its rock strata striking nearly parallel to the slope, and to the direction of the railway linę, and falling at an angle of 40°-80° towards the Rhone valley, is exceptionally steep and has gradients varying between 1 : 2 and 4 : 5. Dur-ing the construction of the railway the numerous rock cuts caused frequent rock slides because the rock layers were deprived of their support, or because of the overburden on the rock. This necessitated considcrable additional excavation work. The debris from such slides had to be removcd and the strata striking parallel to the slope had to be excavated down to the sub-grade of the linę. Therefore in many places, where it was not possible to make cuttings, it was necessary to build big buttress pillars and retaining walls in order to hołd back the materiał that was in danger of sliding, and to support the overhanging rocks.
Because of this the temporary construction railway, which had becn built along the futurę railway track, was often not operated for days. As a consequence great difficulties arose regarding the supply of building materials to the many construction sites, and therefore the completion of the work was delayed. The greatest difficulties were encountered when excavating a large side cutting in the rock above the station of Hohtenn. A considerable rock slide oceurred there 6 months before the scheduled opening of the linę; 6-7000 m3 of rock fell down on to the track, some of which remained there and some fell nearly as far down as the village of Hohtenn. In this side cutting the limestone strata strikes nearly parallel to the centre linę of the track, and falls at an angle of 45° towards the valley. It had been planned to build a 4 m high revetment wali and above this to remove the slope materiał along the stratification. For reasons of economy, and also because it was feared that such a large amount of rock excavation could not be carried out in time, the project was changed and the construction of a 10 m high revetment wali reinforced by buttress pierś was started. The wali was complctcd with the exception of the last 7 metres, when suddenly a 80 m long rock-bank, about 4-6 m thick, started sliding and knocked down the already completed wali. On the surface of the hillside slope thus created, a thin layer of fat clay was found, upon which the entire mass had slid down. To safeguard the layers of rock above the sub-grade, which had not completely slid down, they were anchored to the underlying rock by means of Steel rods inserted at right angles to the slope, which had proved successful at many other places. Besides the safeguarding of the dangerous rock parts by under-pinning, retaining walls and buttress pillars, the railway linę had to be protected along its entire length against falling rocks and earth slides of the topsoil which partly covered the rock. Hundreds of baffles against falling rocks, either immediately above the track or in the region were the rocks were crumbling, had to be crected. These were constructed out of rails or cross-ties. Numerous terraces on the dangerous slopes, the clearing of loose boulders and also a number of dry walls further protect the linę against direct rock falls. Protected by the terraces and stone walls, a re-foresting scheme was started, which, with the aid of a new vegctation belt to be created, will in the course of time will effect a complete consolidation of t’ie dangerous regions.
Extensive drainage by means of gutters and channels provides for efficient dispersal of the water, thereby preventing the thin descend en pente extremement raide (40-80 %) vers la vallee du Rhone, offrant par places une denivellation de 1 : 2 a 4 : 5. Les nombreuses incisions dans le rocher, necessitees par la construction de la ligne, ont cause des glissements rocheux, dus au fait que les couches, privees de leur base, ont glisse. II en est resulte a plusieurs endroits des excedents de deblais. En outre, la ou il n’etait pas possible d’executer des talus, on a eu recours a de grands piliers et murs de soutenement afin de soutenir les materiaux menaęant de s’ecrouler.
II est arrive souvcnt que des glissements aient cntrave pour plusieurs jours les travaux sur toute la longueur de la ligne de service qui utilisait le tracć de la voie ferree, d’oCi des retards considerablcs dans l’cxecution des travaux.
On se heurta a des difficultes extrćmes lors de 1’incision du rocher au-dessus de la gare de Hohtenn ou, 6 mois avant la datę prevue pour 1’inauguration de la ligne, un glissement emporta 6-7000 m3 de roches dont une partie s’amassa sur la voie tandis que le reste devala jusqu’a proximite du village de Hohtenn. La direction des banes de calcaire sur ce tronęon est a peu pres parallele a l’axe de la ligne et le pendage est de 45° vers la vallee. Le projet prevoyait ici un mur de soutenement de 4 m de hauteur et, au-dessus, un talus suivant la stratification. Pour des raisons d’economie, et parce que Ton prevoyait qu’il ne serait plus possible d’excaver le rocher a temps, on modifia le projet initial et commenęa la construction d’un mur de revetement de 10 m, renforce par des contreforts. Le mur etait termine, a I’exception d’un tronęon de 7 m, lorsque, soudainement, un banc rocheux epais de 4-6 m glissa sur une longueur de 80 m environ et renversa le mur.
On constata sur la surface de glissement la presence d’une mince couche d’argile sur laquelle toute la masse s’etait de-placee.
Afin d’assurer la stabilite des couches situees au-dessus dc la cote de la voie, qui avaient tendance a glisser, celles-ci furent anerees au moyen defersronds introduits perpendiculairement a la pente, mesure qui avait fait ses preuves en beaucoup d’autrcs endroits.
Outre les travaux de protection des zones rocheuses, presentant certaihs dangers, au moyen de murs et de piliers de soutenement, il fallut encore proteger la ligne sur toute sa longueur contrę les dangers constitues par la chute des pierres et le glissement des couches d’humus recouvrant le rocher. On edifia des barrages contrę la chute des pierres a 1’aide de rails et de traverses, tant au-dessus de la ligne que dans la zonę de decrochage; on edifia egalement des terrassements reguliers sur les pentes dangereuses, on enleva les pierres et les blocs de rocher disperses sur le terrain et l’on construisit des murs de maęonnerie seche pour proteger la voie contrę les chutes de pierres directes.
Des amenagements etendus de drainage au moyen de cuvettes et de canaux assurent la bonne evacuation de l’eau et previen-nent le glissement des minces couches d’humus ou de deblais. La direction de la ligne du Lcetschberg assure la securite de Texploitation par des contróles pćriodiques de la region et procedc sans delai a la construction d’ouvrages de defense dans les secteurs reconnus dangereux. La surveillance des zones exposees aux chutes de pierres est assurec de jour et de nuit par des gardes spćcialement cntrainćs et la rćparation des defauts signales dans le systeme de defense est immediatement entre-prise.
Bień que la construction du tronęon Goppcnstein-Briguc ait rencontre des obstaclcs particulierement difficiles a surmonter, en raison du tracę defavorable a flanc de coteau et des con-ditions geologiques et tectoniques, la securite du trafie sur ce
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