Issue34

X. Zhengbing et alii, Frattura ed Integrità Strutturale, 34 (2015) 574-579; DOI: 10.3221/IGF-ESIS.34.63 577 (a2) (b2) (c2) (d2) (e2) Figure 2: Damage form of sandstone samples Result analysis It can be seen from Fig. 3 described based on Tab. 3 and 4 that, dynamic mechanical performance of two materials is closely correlated to strain rate. To be specific, dynamic compressive strength of two materials increases linearly with strain rate; dynamic compressive strength of concrete is lower than sandstone. Through linear regression, we can conclude a formula of the relationship of dynamic compressive strength and strain rate of two materials (C stands for concrete, S stands for sandstone and R 2 stands for correlation coefficient). 2 , 2 , ( ) 46.40 0.64 0.95067 ( ) 94.56 0.79 0.87914 c d c d f C R f S R               (1) Comparing the formula, we can conclude that, dynamic compressive strength of rock varies more obvious as strain rate changes. 240 220 180 140 100 60 40 60 80 100 120 140 160 180 Concrete Rock Strain rate/s -1 80 120 160 200 Figure 3: Correlation between dynamic compressive strength and strain rate. Fig. 4 shows the correlation between peak strain and strain rate of concrete and sandstone under the effect of impact load. It can be observed from the figure that, peak strain of two materials tends to be higher as strain rate increases and moreover, this corresponding relationship is quadratic. Formula regarding to the correlation between strain rate and peak strain of two materials can be obtained after linear regression, as follows (C stands for concrete, S stands for sandstone and R 2 stands for correlation coefficient). 4 2 2 4 2 2 ( ) 6.60 0.019 2.76 10 0.99756 ( ) 23.37 0.108 5.87 10 0.96554 p p C R S R                           (2) It can be known that, under the effect of impact load, both concrete and rock changes their forms, and the variation degree is positively correlated to strain rate, i.e., peak value increases with the increase of strain rate.