This paper briefly describes the excavation procedure of a powerhouse, comprising of its incremental excavation, reinforcement measures, and the installed monitoring system. During the first phase of excavation, the data obtained from monitoring of the behavior of Mudstone layers were used to recommend extra support measures. These data are also used to design the support of the powerhouse during its extension phase.

In diesen bericht wird die bohrmcthode von kraftwerk ecavation in stupenweise dargestelt, und in die richtung d.sicherung, Mit hilfe von monitoring systeme. Die monitoring in (mudstone) schichten ist an schutz in bohrung entworfen und montiert in diese methode in K.W. fase 1 schutzung das K.W. in erweiterung der K.W. das berte auserwelt worden ist Cet article decrit brièvement le procede d'excavation d'une centrale electrique, comportant de son excavation incremental, de mesures de renfort, et du système de surveillance installe. Pendant la première phase de l'excavation, les donnees obtenues à partir de la surveillance du comportement des couches de schiste ont ete utilisees pour recommander des mesures supplementaires de soutien. Ces donnees sont egalement utilisees pour la conception de la soutènement de la centrale electrique pendant sa phase d'extension.

Introduction

The Masjed -E-Soleiman Hydroelectric Power plant (170 high rock fill dam with capacity of 2000 MW) under construction is located at the Karun River close to the village Godar-E-Landar in the province to khuzestan/Iran. The first step of powerhouse cavern with supply 1000 MW electricity has been completed recently. The extension of this powerhouse cavern is under construction.

Powerhouse cavern phase one is a space with dimension of 150 lengths, 30 widths and 50 heights. Over burden of powerhouse is 250–320 meter.

The contractors had been involved in this project was DEALIM -SATO (Korean) and TABLIA company (Iranian), with consulting engineer's association team consisting of Lahmeyer International (German), Nippon Koei (Japanese), and Moshanir (Iranian).

Regarding excavation works, such this powerhouse can analyse from different points. In this paper we explain briefly about geology and we concentrate about method of excavation, result of instrumentation, mudstone behaviour and extra rock supports for phase one and extension project.

Geology

The hydroelectric power plant is located in the foothills of the Zagros Mountains. The rock sequences of the upper Aghajari and the overlying Bakhtyari formation are exposed in the area of the excavated underground structures. Underground structures powerhouse is located in Bakhtyari formation. Bakhtyari formation in Godar has been divided into more than ten units. Powerhouse cavern is located in unit IV and unit V. These units contain of siltstone, calystone, sandstone and conglomerate.

Slickensided planes occur more often than in siltstone[4].

In the vicinity of the underground power station complex, the mudstone appears in three clearly distinguished layers dipping at approximately 25° to the east. The upper layer intersects the roof of the PHC and intersects the transformer hall walls. The lower layer intersects the draft tube level at 190 to 205 m. The intermediate mudstone layer intersects the upstream and downstream walls of the PHC.

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