doi:10.16186/j.cnki.1673-9787.2018010026

Received:2018/10/26

Revised:2020/01/08

Published:2021/07/15

Research on the loading rate and size effect of limestone fracturetoughness based on NSCB specimens

ZHANG Sheng1,2, WANG Dongkun1, WANG Longfei1, WANG Xiaoliang1, QIAO Yang1

1.School of Energy Science and Engineering, Henan Polytechnic University, Jiaozuo  454000 , Henan, China;2.Henan Province Collaborative Innovation Center of Coal Work Safety, Jiaozuo  454000 , Henan, China

Abstract:In order to investigate the influence of different size of specimen and loading rate on the test value of rock mode I fracture toughness, five sizes of geometrically similar central straight crack half disk specimens of diameter 30,50,75,100,150 mm were made by limestone （ notched semi-circular bend , NSCB ） .The three- point bending test of the NSCB specimens under five levels of loading rates （ 0.002,0.02,0.2,2,10 kN/s） were carried out on the RMT-150B rock mechanics test system.The results showed that as the sample sizes were certain, the test values of the fracture toughness of the specimen increased logarithmically with the increase of the loading rate.As the loading rate was certain, there was a critical size, which disk diameter was 50 mm.When it was less than this critical size, the fracture toughness test value increases greatly.However, when it greater than this critical size, the test value increased by a small amount and basically increased linearly.The reasons causing the loading rate and size effect were discussed, which was helpful to deeply analyze the fracture characteristics of rock and to determine the fracture toughness accurately.

Key words:limestone;fracture toughness;loading rate;size effect;NSCB specimen

 基于NSCB石灰岩试样的加载速率和尺寸效应对其断裂韧度的影响研究_张盛.pdf