Experimental Study of Point Load Based on Close-Range Photogrammetry

At present, the area of the fracture surface is mostly obtained by equivalent approximation method in point load tests. However, the area obtained by this method is not accurate enough in current point load tests. To solve this problem, a method based on close-range photogrammetry technology was developed. Point load test and uniaxial unconfined compressive strength test of cement mortar test block were carried out. The area measurement method based on close-range photogrammetry technology and the traditional approximate formula method were used to obtain the point load test strength values of test blocks, the unconfined compressive strength values. The two unconfined compressive strength values were compared with the unconfined compressive strength value of the real test block. The results show that the point load strength and uniaxial compressive strength obtained by close-range photogrammetry are slightly higher than those measured by traditional point load test. The statistical test results from the SPSS software shows that there are significant differences between them. Compared with the unconfined compressive strength value of the real test block, the difference coefficient analysis showed that the difference coefficient of the traditional point load test is 41%, and that of the close-range photogrammetry method is 30 %. The close-range photogrammetry method produced values closer to the measured uniaxial compressive strength results. The research showed that the new method has higher accuracy in calculating the point load strength, and the method based on close-range photogrammetry is easy to implement in practice.