Issue34

X. Zhengbing et alii, Frattura ed Integrità Strutturale, 34 (2015) 574-579; DOI: 10.3221/IGF-ESIS.34.63 575 exploitation. Thus to meet the demand of engineering more effectively, the key point lies on the comparative study of mechanical performance of concrete and rock [4]. But scholars tend to focus more on static characteristics of concrete and rock [5, 6] rather than dynamic mechanical performance of them. Furthermore, literatures about comparison of mechanical performance of them together are seldom reported though many scholars have carried out related researches. Through comparing mechanical performance of concrete and rock under impact load, this study further analyzed their damage mechanism, aiming to offer more theoretical reference for dynamic load carrying of practical structural engineering. O VERVIEW OF MECHANICAL CHARACTERISTICS OF ROCK MATERIALS tudy of dynamic mechanical characteristics of rock materials mainly includes three aspects, i.e., dynamic input, analysis of dynamic mechanical characteristics of materials and dynamic respond analysis of structure of rocks [7]. Study of structural dynamics has acquired substantial breakthrough, because only one experiment is enough to effectively stimulate all influence factors to reflect actual situation of structure, benefiting from the innovation of experimental instruments and test technology, enhancement of dynamic theory and remarkable results of structural mechanical model experiment. Relatively speaking, analysis dynamic input and dynamic mechanical characteristics is weak, as related research is not deep enough and many basic issues are still being explored. An important research direction exists in study of dynamic mechanical performance of rock materials, i.e., correlation rule of strain rate of dynamic performance of materials. A large amount of previous comparative analysis of dynamic and static experimental results of rock materials [8] suggest that, strain rate is closely correlated with performance of materials, and the correlation has recognized by most experts and scholars. However, issues concerning how strain rate impacts performance of materials and what is the rule have not been unified in academic field, and moreover, related research is still remained at impact of material strength, such as impact on dynamic fracture character and deformation characteristics and sensitivity of micro-structure dynamic characteristics of different materials to strain rate. C OMPARATIVE EXPERIMENT OF DYNAMIC MECHANICAL PERFORMANCE OF CONCRETE AND ROCK Experimental materials oncrete used is ordinary silicate concrete composing of water, ordinary Portland cement, coal ash, silica fume, macadam, sand and water reducing agent. Detailed proportion is shown in Tab. 1. Water Cement Coal ash Silica fume Macadam Sand Water reducing agent 180 375 125 25 690 1030 5 Table 1 : Proportion of different components of ordinary silicate concrete (kg/m 3 ). Rock used is unweathered natural sandstone taken from Qinling Mountains with field sampling method. It is mainly composed of quartz and calcite and shows up white color. Detailed components are presented in Tab. 2. Components Quartz Calcite Plagioclase Potassium feldspar Montmorillonite Chlorite Illite Dolomite Content (%) 52 27 8 6 1 2 3 1 Table 2: Component of sandstone. Experimental equipment and method Split Hopkinson pressure bar (SHPB) (diameter 100 mm) made up of three parts, main equipment, energy system and test system is the main equipment for dynamic compression test [9]. Sample of concrete and rock is obtained through several professional procedures. First, samples are taken using ZS-100 upright core drilling machine, then cut by DQ-1 cutting machine. (The machine can be applied in fields like petroleum, geology, metallurgy, coal and exploration; diameter of blade: 450 mm or 500 mm; cutting scope: single blade (diameter 500 mm) can cut cylindrical rock core with a diameter of S C