Rock mass deformation modulus can be estimated via several methods that include both direct in-situ testing and empirical techniques that incorporate properties of the rock mass including fracture and intact rock characteristics. Each technique has merit but also inherent limitations. Large - scale techniques such as plate loading test offers scale advantages by testing at a more reasonable rock mass scale. Based on above philosophy a number of plate loading tests has recently been conducted by Khak and Sang co. at the Karun-4 dam site in Chaharmahal province to the south west of Iran. In this paper, findings of these tests as well as other approaches under taken for the determination of rock mass modulus will be discussed. According to geotechnical findings the rock masses of the site are divided in three classes. The results of plate loading tests in three classes of rock show that there is a good correlation between two sets of results.
Karun-4 dam site on Karun River in Chaharmahal province to the south west of Iran has been approved to build a 205m high double curve concrete hydropower dam capable of running a Power station with 1000MW/h capacity. In addition to the dam body with volume of 1.6million 3 m concrete, spillway, power station and intake and outlet tunnels are permanent structures of project. Feasibility study of the project started in 1990 and the geotechnical site investigation has been carried out in three phases since 1993. To find out the geomechanical properties of rock mass an extensive rock mechanics testing program has been performed. The in situ tests including flexible dilatometer test (FDT), Plate loading test (PLT) and direct shear test (DST) conducted in various galleries at both side of the river in different levels. Determination of rock mass modulus, a parameter of significance to the Karun-4 project is calculated using data gathered from 17 PLT tests. The successful conduct of PL T tests has allowed the designer to undertake a comprehensive evaluation of the mechanical behaviour of the various formations of the site, including determination of rock mass modulus, as well as providing data against which other methods can be compared.
Rock mass deformation modulus can be determined via several methods that include both direct in-situ testing and empirical techniques that incorporate properties of the rock mass including fracture and intact rock characteristics. Each technique has merit but also inherent limitations. These techniques include large-scale in-situ tests such as plate loading test, rock mass block test, pressurized gallery test, flat jack test in slot, borehole tests such as the Goodman jack, and dilatometers, geophysical techniques such as cross hole ultrasonics, and estimations from rock quality field surveys (George et al. 1998). Each of these techniques has some advantages but also basic limitations. Borehole tests are relatively easy to conduct but the limitations in size of equipment could not load a large volume of rock, therefore the local heterogeneities can influence the results a lot.
