Study on the evolution of mechanical properties of

Research on the evolution of mechanical properties of rock mass under explosion impact load

1 introduction

in the construction process of many civil engineering projects such as mining, road and hydropower construction, blasting method is needed to excavate a large amount of earth and rock in many cases. A large number of explosives will release great energy during explosion. Such impact load will not only destroy the rock and soil medium in a certain range, but also produce strong disturbance to the adjacent rock mass. This strong impact disturbance will have a certain degree of impact on the surrounding rocks at different locations. The study of these problems has important theoretical and practical guiding significance for the reasonable design of blasting parameters, the effective reinforcement of surrounding rocks and the stable support design of high slope engineering

2. Model test research

has laid a solid foundation for the further improvement of the company's technology. In order to study from the experiment and obtain the influence of explosion impact load on the mechanical properties of rock mass, the experiment is carried out by means of explosion loading of prefabricated cement mortar test block model, and the specific size of cement mortar test block is 600 × mm × 500mm × 300mm electronic universal experimental machine is powered by electromechanical. In the experiment, a 20mm diameter blast hole is reserved at the upper part of each test block, and the blast hole is 100mm away from the front free surface. The charge structure used in the experiment is a coupling charge with a charge of 5g, which is detonated by an 8# detonator. In the experiment, the pre explosion and explosion distance of the model test block are used at 100mm, 250mm, 400mm and Ф 50mm coring machine for coring. Figure 1 shows typical examples of test models, such as the size and blast hole layout of Beijing Fengji and Beijing University of chemical technology

Figure 1. The design size of steel production and blast hole layout can be optimized by model test

2.1 evolution of ultrasonic propagation velocity

the change of weak wave velocity in rock mass can reflect the change of physical and mechanical properties and dynamic mechanical properties of rock mass. The change of wave velocity value is widely used to determine the damage or defects generated in rock mass. In this experiment, the core samples taken before and after explosion were tested by ultrasonic

(1) the change of axial wave velocity along the core. The typical results of ultrasonic testing of core samples with flat head transducers for the testing of No. 1~4 specimens are shown in Table 1

Table 1 strength and ultrasonic test results of No. 2 and No. 4 specimens

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