Many of Iran's engineering structures such as dams are located on Asmary Formation, southwest of Iran; therefore investigation of the in situ deformation modulus of this formation is very important for optimizing the engineering design of similar projects. Deformability parameters indicate deformation of rock mass in response to any loading or unloading. The dilatometer test is one of the most common methods for in situ measurement of these parameters. In this paper, more than 700 dilatometer test data from five dam sites located on Asmary Formation were analyzed. According to the results, at confidence level of 95%, the range of deformation modulus of Asmary rock mass is calculated between 3.92 to 9.31 GPa. Additionally, local changes of deformation modulus in different dam sites were investigated. The engineering classification indexes for rock masses (especially GSI) and laboratorial elastic modulus were found to be the main tools that affect the deformability modulus in the studied dams. Moreover, an appropriate nonlinear multi-variation equation was developed by using the GSI index and the laboratorial modulus (Ei) to estimate the deformabili.


Generally, deformability is defined by a modulus describing the relationship between the applied stress and the corresponding strain. Since existence of discontinuities and joints in rock mass results in a non-elastic behavior, it is usually preferred to use the deformation modulus instead of elastic modulus or Young's modulus [1,2,3]. Researchers and scientific societies utilize various methods for determining the deformation modulus. Among them are

  • Direct measurement using in situ tests

  • Indirect estimations based on rock mass classification methods

  • laboratorial result generalization for rock mass

The results obtained by all these methods are not of the same reliability. For example the direct measurement method by use of in situ test is ranked as the most reliable [3]. Dilatometer test is known as one of the most important, economical and simple in situ tests for measuring the deformation modulus of rock mass and is widely used in a great number of major engineering projects. Since many of Iranian engineering structures such as dams are located on Asmary Formation, which is also one of the most prolific oil producing sequences in the world, studying the range of deformabilities in this formation is critical for optimizing the design of the under construction projects or those that will be started in near future. In this paper, more than 700 dilatometer test data obtained from 5 dam sites located on Asmary Formation were analyzed. All of the dilatometer tests were performed by the same operator, and by use of the identical device under the supervision of "Khako Sang" Co. The used device was an IF096 dilatometer made by Interfels Company. This paper contains a short description of this device. Also, a general geological description of the Asmary Formation will be presented.ty modulus of Asmary Formation in different sites.

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