Abstract
In order to study the influence of pillar stopping blasting on the stability of cemented backfill, the dynamic impact test under low strain rate (61.1∼86.8 s−1) was conducted on cemented backfill with two kinds of strength using three-dimensional coupled static-dynamic SHPB equipment. At the same time, the strain rate effect of failure mode, dynamic strength factor, and energy transfer of backfill were analyzed. The results show that when the cemented backfill was loaded under different strain rates in the initial three-dimensional static pressure environment, the pore compaction process was no longer obvious but directly entered the elastic deformation stage. Within the range of strain rates, the extreme value of dynamic intensity factor (DIF) of CTB230 was 6.8, while the extreme value of dynamic intensity factor of CTB310 specimen did not appear within the range of strain rates due to the improvement of the internal cementation force between particles. The fracture surfaces of specimens were perpendicular to the direction of load, and the failure mode was mainly the axial tensile failure, and the fracture surfaces were mostly close to the loading end. According to energy calculation, reflected energy accounts for 80.4%∼86.6% of incident energy; dissipated energy, 5.5%∼14.3%; transmitted energy, 5.3%∼7.9%.
Highlights
Materials under different strain rates and showed that there was an extreme value of dynamic strength and obtained the S criterion of dynamic uniaxial compressive strength through theoretical deduction and experimental verification. e theoretical formula is as follows: dynamic intensity factor (DIF)
Yu et al [3] analyzed the response of concrete-like materials under different strain rates. e results showed that the concretelike material is not sensitive to the strain rate at low and medium strain rates, but its dynamic strength or yield stress is very sensitive at high strain rates. e S criterion of dynamic strength is used to modify the strain rate effect function of the classic Johnson-Cook constitutive
In order to reflect the force of cemented backfill in the mine more truly, three-dimensional dynamic and static combination SHPB impact tests under different strain rates were conducted to study the dynamic mechanical properties, failure modes, and energy laws of cemented backfill with two kinds of strength, and the following conclusions can be drawn
Summary
In the actual backfill project, the cement content of the cemented backfill body ranged from 210 kg/m3 to 280 kg/m3. In this research, cemented backfill bodies with two different strengths, 230 kg/m3 (represented by CTB230 in the following) and 310 kg/m3 (represented by CTB310 in the following) were selected. E impact test under four different loading strain rates was carried out, while coaxial confining pressure was kept the same. In order to ensure the uniform distribution of internal stress and strain when the specimen is impacted, the experiment requires a high smoothness on both ends of the specimen, and the parallelism is generally required to be within the range of 0.02 mm. In order to ensure the uniform distribution of internal stress and strain when the specimen is impacted, the experiment requires a high smoothness on both ends of the specimen, and the parallelism is generally required to be within the range of 0.02 mm. e test piece was polished twice with a grinding machine, and the final length error of the test piece was controlled to be ±0.02 mm, and its roughness was about 0.02 mm (Figure 2)
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