ABSTRACT

This paper reports the experiment of compressive process for siliceous-lime marble containing NaCl solution. Two electrodes of copper powder gelatin were fixed on the surface of siliceous- lime marble sample and by means of electric conductivity character of crack or pore water in rock, the experimental data of electrical resistance were measured with stress or strain changing. The electrical resistance of siliceous-lime marble increases continuously with compressive stress from the initial loading to the greatest stress, but the increasing rate of electrical resistance decreases gradually. In the loading process, there isn't the phenomenon of rock crack closing, but consistent expanding. However, with regard to the relatively high-strength rocks [3–4], their electrical resistance decreases with strain from the initial value and after going through the cracking point, turns to increasing. The experimental results indicate that the law of stress change with strain and that of electrical resistance change with strain are in line with the quadratic fitting equations. Under the axial compressive stress acting, the deflection increasing correlates closely with micro-crack expanding for siliceous-lime marble.

1 INTRODUCTION

W.F. Brace et al. conducted early the experiment of electrical resistance changing with stress of rock and owed the variation to the dilation of bulk [1–2]. On what has already been achieved, the basic law of electrical conduction of rock containing NaCl solution and the measuring method of pulse non-polarization electrical current were studied. The experimental facility was established and the complete experimental data of stress-strain-electrical resistance of rocks were gained[3–4]. Some researchers explore also the physical effects of rock stress by other methods. M. Setol et al. investigated the possibility of acoustic emission (AE) technique to measure in situ rock stress using the Kaiser effect. The characterization AE increase in an increasing stress exceeds the previous stress [5]. Through the use of a high-speed multi-channel waveform recording system, the detailed time-space distribution of AE activity was examined during the fracture of rock samples containing faults of widely differing strength distribution under triaxial compression [6]. Ge Xiurun, Feng X.T., et al. engaged in a real-time CT scan testing study of meso-damage evolution in rock compressive process. The failure mechanism of rocks is explored and preliminary law of damage expansion is obtained [7–8]. The computerized tomography images and CT values for the process of unloading, micro-cracking, and dilation up to the failure of limestone specimens under different unloading levels were acquired, by using the real-time CT technique. A damage model based on CT value and a new failure criterion are established [9]. In order to make clear the relation between thermal conductivity and compressive stress of rock, Demirci et al. developed a new device of experiment and obtained the law of experiment data variation for the rock specimens representing sandstone, conglomerate, gypsum and marble. The thermal conductivity coefficient increases compared with uniaxial stress application [10].

In this paper, in connection with the characteristic of relatively low-strength for siliceous-lime marble, the regularity of electrical resistance changing with stress was explored through experiment measuring.

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