Multiscale effects caused by the fracturing and fragmentation of rock blocks during rock mass movement: implications for rock avalanche propagation

Abstract

Abstract. The fracturing and fragmentation of rock blocks are important phenomena that occur ubiquitously during the propagation of rock avalanches. Here, the movement of a rectangular rock block characterized by different joint sets along an upper sloped and lower horizontal plane is simulated using discrete element method (DEM) models. The pattern of the joint set allows the block to break along weak joint planes at the onset of fragmentation. With this design, the fracturing and fragmentation of the sliding rock block and their influences on the conversion and transmission of energy within the system are investigated. The results show that rock fragmentation can significantly alter the horizontal velocities and kinetic energies of fragments in the block system, accelerating the front sub-block while decelerating the rear sub-block. Such energy conversion and transmission between the front and rear sub-blocks are attributed to the accumulation and release of elastic strain energy caused by fragmentation. The energy transfer induced by fragmentation is more efficient than that induced by collision. Furthermore, positive relationships between the kinetic energy increase in the front sub-block induced by joint fracturing and the joint strength can be reliably fitted with linear functions, indicating that a rock mass with a higher joint strength experiences more-energetic fragmentation effects.

Estimating Rockfall and Block Volume Scenarios Based on a Straightforward Rockfall Frequency Model

“…Two sites (Nax, Fläsch 1) have higher b values compared to the range (0.63-1.29) obtained by Lanfranconi et al (2020), who also found a different trend in the lithology dependence. The value of the parameter b depends mainly on the geology of the cliff, and fragmentation is often caused by fracturing along pre-existing weak joint planes (e.g., Lin et al, 2022). Additionally, the fall height of the blocks plays a role (De Blasio and Crosta, 2015;Ruiz Carulla et al, 2016).…”

Determining Digital Representation and Representative Elementary Volume Size of Broken Rock Mass Using the Discrete Fracture Network–Discrete Element Method Coupling Technique

“…In the past two decades, many scholars have conducted in-depth research on this technique and developed corresponding programs to reproduce the rock structural surface, such as the Fracman program, Blocks program, and Geofrac program [24]. These programs are generally based on the Monte Carlo method to generate rock mass fracture networks, and the basic process of Monte Carlo random simulation technology can be summarized as (1) conducting on-site joint geological surveys to obtain basic geological parameters of rock fracture samples, such as fracture density, attitude, spacing, and aperture ratio; (2) performing statistically analyses on the geological parameters of the fracture samples and fitting corresponding probability density and distribution functions; and (3) using the Monte Carlo method to generate random fracture networks that statistically match the actual distribution of the rock mass fractures based on specific distributions of random numbers. The implementation process of random fracture network simulation is shown in Figure 1.…”

“…Within various geological regions, the rock masses manifest diverse quantities and types of structural surfaces. For broken rock masses that are characterized by a high-dispersion structure due to extensive jointing, fissuring, and faulting, the discontinuity and anisotropy of the structure become more pronounced [1,2]. In engineering practices involving broken rock masses, such as tunnels at near-fault regions and side slopes in highly weathered rock formations, the randomness of discontinuities, the variability in rock mass parameters, and the uncertainty associated with surrounding rock loads pose potential risks to the safety of the construction projects [3,4].…”

The Champati Slide

“…As soon as the Champati slide impacts the horizontal plane, it behaves as if it was a fragmented rock particles. With this behaviour, one may even think if some kind of force, akin to the dispersive pressure in rock fragmentation(Davies and McSaveney, 2009;Dufresne et al, 2016;Lin et al, 2022), is involved that ultimately…”

“…For this reasons, Champatis are said to exhibit the hyperspreading during their motion, deformation and deposition. Such spreading may be useful to model and describe the super-spreading of the fragmented clasts in the natural rock-avalanches in the distal run-out fan(Davies and McSaveney, 2009;Dufresne et al, 2016;Lin et al, 2022). Once the bucket is lifted, the Champatis in the outer part of the moving/deforming heap roll and spin…”