1 Introduction

One of the main methods in hard rock quarry mining is the controlled fracture method that is carried out by the introduction of a slowly advancing crack by Non-Explosive Expansion Material (NEEM). The method of rock breakage is without noise and vibrations and its operation, compared to blasting method, is more controllable, very safe and easy and without extra undesirable cracks in the rock block (Hinze and Nelson, 1996; Gambatese 2003; Huynh, et al. 2009; Laefer, et al. 2010).

In this method, some circular holes are drilled closely with equal length, diameter and spacing (center- to-center distance) in a rock block. Subsequently, the holes are filled by the NEEM, which it can be expanded and generates an incremental static loading into the holes after about two to four hours. If the spacing of the holes to be adequate, it will create a crack between two neighboring holes and the rock will fracture along the high-stress concentration path between the holes. In this paper will be try to introduce a new numerical modelling approach for showing location and length of the first cracks around the holes and predicting of the crack growing path with the geometry.

2 Experimental data and a case study

A granite quarry mine was selected as a case study entitled "Ahrar Mine" which it has located near to Natanz in Iran (Fig. 1). Some laboratory tests have been done on the granite specimens for measuring of some rock mechanic's properties such as uniaxial compressive strength, Brazilian tensile strength, Young's modulus, Poisson's ratio, specific gravity and fracture toughness by ISRM standard methods (Fowell, 1995), (Tab. 1). Process of rock fracture in due time by the NEEM has been shown in Figs. 1 and 2. The drill holes were 38 mm with 1 to 3 meters depth and the average of the hole's spacing was 12 cm (10–14 cm) in the mine.

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