Geotechnical instruments are integral part at power house cavern (PC) of Kiah Boshes project. Instrumentation data are collected during and after excavation and concreting period. Absolutely, extensometer is the main instrument in large underground spaces which install as soon as possible in excavation phase. Pressure cell, pedometer and linear displacement transducer are main instruments applied in concreting period. Two extensometer In order to achieve total displacement are installed before starting of PC excavation. We are analysis instrumentation data for powerhouse cavern of Kiah Boshes project to determine amount of omitted data which help to back analyzing and achieve actual rock mass properties. About 5 cm Styrofoam board in order to damping future rock mass displacement to concrete wall is installed between concrete and shotcrete surface. Also some opening anticipate for future ground anchor. According instruments data, stable condition achieve after concreting period.


Kiah Lishe pumped storage power plant is the first pumped storage project at Iran with capacity of 1000 MW. Power house cavern (PC) with 131m high, 24m width and 47m high is adjacent of guard gate and transformer caverns. PC is located in a sedimentary layers (Quartzite Sandstone and red Shale) and igneous masses (intrusive rock). Thickness of sedimentary layers is from some centimeter to about 1 meter. Some shear bands and two major joint set are affected rock mass [1].


PC has excavated and supported generally according to the New Austrian Tunneling Method (ATM). Vault admit exists on upstream side of PC which help to install two extensometer (E10 and E15) before starting of PC excavation. PC has excavated at two parts: top and benching. PC crown divided to three parts: upstream, center and downstream (figure 1). PC benching was started after installation of roof ground anchor (mono bar). PC invert lowering about 3 m in each sequence of benching, figure 2. PC's volume was 117700 cubic meters which excavated from Oct. 2004 until Feb. 2007 and concreting from July 2006 until July 2010.


PC monitoring system consists of six instrumentation sections (figure 3). Two extensometer (E10 and E15) are installed before starting PC excavations (figure 4) and other instruments (extensometer, load cells and convergence meters) are installed during the excavation period. Therefore, for more extensometer installation delay cause omits some of actual displacement which is related to PC excavation. Concrete instruments such as pedometer, pressure cell and linear displacement transducer are installed during concreting period.


According E15 date-displacement curve (figure 5) and sequence of PC excavation (figure 1 and 2): More than 15 percent of total movement wall occurred before that invert reach to elevation of extensometer. About 23 percent of total movement of PC wall occurred before that invert reaches to 1.3 m below of extensometer elevation.


Some geotechnical instruments such as Pressure cell(figure 6-a), Liner displacement transducer(figure 6-b), Pedometer and Strain gage are installed in concreting phase of PC in order to monitoring rock concrete interaction [2].

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