An improved 3D DDA method considering the unloading effect of tunnel excavation and its application

A Large-Scale Three-Dimensional Apparatus to Study Failure Mechanisms of Rockfalls in Underground Engineering Contexts

“…The FLIRA615 Infrared imager is used to monitor the temperature response of unstable blocks and adjacen during the collapse of dangerous rocks and reveal the response law of the rock m perature field during tunnel construction. The PCI-EXPRESS-8 acoustic emission The steps of loading the test body under confining pressure are as follows: 1 ⃝ Hoist the blocky rock mass and the prefabricated frame onto the positioning sub-system to ensure that the bottom of the prefabricated frame is close to the anti-fall fixing frame, and then realize the horizontal positioning adjustment of the test body; 2 ⃝ start the sliding plate pushing device to accurately deliver the test frame to the test position; 3 ⃝ start No.1 and No.22 oil cylinders to make them rise synchronously, so as to lift the test frame; 4 ⃝ start the oil cylinder of the upper loading plate, so that the upper loading plate descends and stops after making contact with the upper edge of the prefabricated frame; 5 ⃝ start No.2-No.21 oil cylinders of the lower loading plate, and stop after reaching the same height as No.1 and No.22 oil cylinders, so as to realize the up-and-down clamping of the prefabricated frame; 6 ⃝ drive the left and right loading plates to contact the left and right edges of the test frame and then stop, so as to realize the left and right clamping of the test frame, and then solve the fixing problem of the prefabricated frame; 7 ⃝ remove the prefabricated frame connecting square pipe, connecting channel steel, and loading plate connecting bolts in turn; 8 ⃝ start the upper loading plate, load it to 0.3 Mpa, stop loading it, start the left and right loading plates, and stop loading it to 0.3 Mpa, thereby completing the loading operation of the test body.…”

“…During the experiment, the excavation simulation is divided into two directions: 1 ⃝ left to right and 2 ⃝ right to left.…”

“…A natural rock mass always splits into different types of blocks of varying sizes along numerous discontinuities [1][2][3][4]. When the blocks satisfy certain conditions, they are apt to fall and incur instability [5,6].…”

“…Such devices provide a foundation for the development of rockfall simulation experiments. However, these devices suffer from several shortcomings: (1) the structure and stress of rock mass cannot be simulated accurately; (2) the process of excavation cannot be simulated in detail; and (3) limited information is obtained during the experiment. Thus, the experimental process does not fully reflect all failure stages.…”

“…Monitoring instrument and monitoring design scheme. 1⃝ The laser scanner 2. ⃝ The infrared thermal imager 3.…”