Point Load Test of Half-Cylinder Core Using the Numerical Model and Laboratory Tests: Size Suggestion and Correlation with Cylinder Core

Fengyu Ren,Rongxing He,Guanghui Li,Yang Liu,Huan Liu

doi:10.1155/2018/3870583

Abstract

The point load test (PLT) is intended as an index test for rock strength classification or estimations of other strength parameters because it is economical and simple to conduct in the laboratory and in field tests. In the literature, calculation procedures for cylinder cores, blocks, or irregular lumps can be found, but no study has researched such procedures for half-cylinder cores. This paper presents the numerical model and laboratory tests for half-cylinder and cylinder specimens. The results for half-cylinder and cylinder specimens are then presented, analysed, and discussed. A correlation of failure load between half-cylinder and cylinder specimens is established with a suitable size suggestion and correction factor. It is found that the failure load becomes stable when half-cylinder specimens have a length/diameter ratio higher than 0.9. In addition, the results show that the point load strength index (PLSI) of half-cylinder cores can be calculated using the calculation procedures for diametral testing on cylinder cores, and it is necessary to satisfy the conditions that the length/diameter ratio be higher than 0.9 and the failure load be multiplied by 0.8.

Highlights

Rock specimens of point load test (PLT) can be applied to cores, spheres, blocks, and irregular lumps. e rock specimens come in different shapes
Several researchers reported the PLT of irregular lumps, but the results were very different for different rock types, and the data of tests were scattered
Diametral and axial tests of cores are generally preferred for results compared to the PLT of irregular lumps. us, the shapes of rock specimens can be different, but calculation procedures of PLSI are different for different shapes

Summary

Half-Cylinder Cores

In the design phase of the mining method, it was necessary to take several factors into consideration. e mechanical parameters of the rock were the basis index for evaluating the stability and caveability and determining the management method of stope ground pressure and the structural parameters of stope. erefore, we obtained the detailed rock mechanics parameters in the mining design phase, which were significant in making the choice in the design of mining methods. Erefore, we obtained the detailed rock mechanics parameters in the mining design phase, which were significant in making the choice in the design of mining methods. There was no mining excavation engineering in the mining design phase, and a large number of rock specimens could not be obtained. E Luoboling Copper-Molybdenum mine was used in the design phase, and block caving was determined initially. One major problem for the mine was determining how to get more detailed rock mechanics parameters and their distribution to guide the mining engineering design. Erefore, half-cylinder cores were kept (Figure 1). 18 granodiorite specimens of the half-cylinder core were taken in the same borehole. According to the size requirements of ISRM, the loading direction of PLT was along the radial direction of the half-cylinder core specimens. E loading direction of half-cylinder specimens was along the radial direction, and the shape was not a cylinder

Numerical Model

Laboratory Tests

Conclusions and Discussion