Laboratory investigation of stress waves in young shotcrete on rock

Abstract

To study the behaviour of shotcrete under dynamic load, a non-destructive laboratory experiment was set up with P-wave propagation along a concrete bar, with properties similar to rock. Cement-based mortar with properties that resemble shotcrete was applied to one end of the bar with a hammer impacting the other. The shape of the stress waves travelling towards the shotcrete was registered using accelerometers positioned along the bar. Finite-element modelling was used to verify the test results, which showed that the laboratory model with an impacting hammer could be used to initiate the same type of stress waves that result from blasting in good-quality rock. Previously recommended maximum allowed peak particle vibration velocities were verified.

Exploring Dynamic Spalling Behavior in Rock–Shotcrete Combinations: A Theoretical and Numerical Investigation

“…support means to maintain the stability of underground structures, the spalling behavior around the structures with shotcrete has shifted from the response problem of one medium to the coupled response problem of a rock-shotcrete combination or multiple media (as shown in Figure 2), which has been a subject of considerable interest. For example, Ahmed and Ansell [27] conducted a laboratory experiment on a concrete bar with cementbased mortar applied to it and partly verified the previously recommended maximum allowed peak particle vibration velocities in their numerical simulation investigation [28]. Luo et al [29] investigated the dynamic tensile behavior of rock-shotcrete interface geometry exposed to vibrations and found that the bearing capacity of rock-shotcrete interfaces varies with the height of the micro sawtooth.…”

Safety Distance of Shotcrete Subjected to Blasting Vibration in Large‐Span High‐Speed Railway Tunnels

“…Shock and Vibration 5 results [4][5][6][7]. Analysis of monitoring data (Table 3 and Figure 9) showed that PPV-Z values at blasting vibration monitoring points were about 1.5-2 times higher than PPV-X and PPV-Y.…”

“…ese advantages allow shotcrete to be widely used as a construction technique in tunnels excavated by the drill and blast method [1][2][3]. Usually shotcrete and blasting operations are performed alternately, and the main function of shotcrete is to provide a safe working environment for workers and facilitate subsequent operations of support construction such as installing metal meshes and bolts [4,5]. erefore, high capability of projecting shotcrete on rock surfaces is vital to the safety of workers and the function of tunnels [6].…”

“…Some researchers have investigated the effect of vibration caused by blasting on shotcrete through in situ tests [4][5][6][14][15][16]. Blast vibration responses (especially PPV) of rock and shotcrete are measured with accelerometers and velocimeters placed on rock surfaces and at the floor or arch waist of tunnel.…”

“…is paper aims to determine the safety distance of shotcrete based on the bond failure of shotcrete-rock interface subjected to blasting in tunnel excavations. In this paper, an analysis method based on both in situ tests and theoretical solutions has been used, an approach similar to that in [5][6][7]22] but here applied for different geological conditions and tunnel geometries. e monitoring scheme with symmetry testing points inside the rock has been carried out for blast vibration monitoring in the large-span tunnel.…”