The Research On Rock Point Load Test

With the development of the infrastructure construction, the significance of rock strength test becomes more and more important. Point load test is the relatively popular way to measure the rock strength in field experiment, and it is based on the experimental data and dimensional principle, but its physical meaning is not clear. Current research mainly focuses on the relationship between point load index and uniaxial compressive strength, ignoring the test analysis. The analysis of the point load test is of very important practical significance.This article take rocks point load test for research object, mainly on the follow:1. Simplify the point load test condition, we take the finite element method to establish the linear elastic material model, which under uniformly pressure,Specimens are destroyed because of tension. Along the loading direction, compressive stress decrease gradually from loading point, perpendicular to loading direction, stress shows a bell shape distribution. The maximum tensile stress appears at loading point below. Tensile stress is relevant to the load radius and Poisson's ratio.2. Based on Hertz contact theory, combined with finite element method, the stress distribution in loading direction are discussed according to the size and magnitude of loading stress. Take an Analysis of stress istribution changes in loading direction under uniformly pressure and Hertz pressure。3. Taking the Three Gorges granite as the research object, using particle flow software PFC2D, we establish virtual specimens to research point load specimen damage. We successfully simulate the whole process of loading destruction in point load test,and draw the stress distribution in failure process. At last, we got an important feature of brittle materials:the internal stress was zero before specimen destroyed,but specimens still own the ability of bearing external force.