A Numerical Study of Rockslide-Structure Interactions in a Dip Slope Disaster by 3D Discrete Element Modeling

<p>The past decade has witnessed increasing case studies on the application of 3D discrete element modeling to assess potential rockslide disasters. The assessment is usually based only on the influence area related to kinematic process and final deposition by the simulation. Currently, the hazard of the rockslide-structure interaction is not well defined, and only a few studies have quantality this behavior with a parametric analysis. A dip slope disaster case history on 18 August 1997 in Taiwan was simulated in this study using discrete element method (DEM). The landslide intensely damaged a five-floor building complex of the Lincoln community and caused 28 death. This study first gathered historical aerial images, geology maps of 1:50,000 scale, post-disaster investigation reports, and in-situ photos to clarify the geological and geometry conditions of the dip slope and its spatial relationship to the Lincoln community. Most importantly, a 3D geomechanical model was developed for the numerical study. With the advantage of DEM analysis on large deformation problems, the entire impact process of the dip slope failure was simulated, starting from rock mass sliding to collision and breaking during movement, impacting on the structural buildings and progressive failure of the structures. The simulated results agree well with the field observation after the incident in 1997. The parametric results show that the configuration of the geological discontinuity dominates the magnitude of the potential sliding block, and the rockslide-structure interactions are affected by the relative location between rock slope and buildings and the strengths of rock mass and structure elements. Overall, the 3D DEM-based simulation provides qualitative information on the impact process of the rockslide and the damage states of the building complex. This validated numerical approach can be a valuable tool for assessing the building vulnerability to rockslide with scenario study.</p>

Real-time monitoring and FEMLIP simulation of a rainfall-induced rockslide

Rockslides are a common and devastating problem affecting mining and other engineering activities all over the world; consequently, there have been many studies into their prediction and prevention. This study focused on a recent rockslide in an open-pit mine in Liaoning Province, China. The stability of the rock slope under excavation and rainfall conditions was monitored using an efficient real-time monitoring system. A further numerical analysis was performed using the finite element method with Lagrangian integration points (FEMLIP), and two forms of the normalized global second-order work were calculated to analyze the stability of the rock slope. In fact for the future it would be very interesting to compare measurements and simulations in real time, and not only to develop back computations after failure. The numerical results indicate that the rock slope remained stable during excavation, yet lost stability after subsequent rainfall. Water infiltration, along with a major geological discontinuity, degraded the strength of the weak zone and induced the rockslide. The monitoring approach presented its robustness and generality, and was worth being generalized. The numerical approach proposed the evolution of the safety factor, the monitoring data were compared, and the mechanism of the rockslide was determined. It could be used as an assistant tool for disaster prediction.

Real-time monitoring and FEMLIP simulation of a rainfall-induced rockslide

Rockslides are a common and devastating problem affecting mining and other engineering activities all over the world; consequently, there have been many studies into their prediction and prevention. This study focused on a recent rockslide in an open pit mine in Liaoning province, China. The stability of the rock slope under excavation and rainfall conditions was monitored using an efficient real-time monitoring system. A further numerical analysis was performed using the Finite Element Method with Lagrangian Integration Points (FEMLIP), and the normalized global second order work was implanted to assess the structure instability as a safety factor. In fact for the future it would be very interesting to compare in real time measurements and simulations, and not only to develop back computations after failure. The numerical results indicate that the rock slope remained stable during excavation, yet lost stability after subsequent rainfall. Water infiltration, along with a major geological discontinuity, degraded the strength of the weak zone and induced the rockslide. The monitoring approach presented its robustness and generality, and was worth being generalized. The numerical approach proposed the evolution of the safety factor, comparing the monitoring data, and the mechanism of the rockslide was determined. It could be used as an assistant tool for the disaster predictions.

Geoelectric prospecting in University Campus region for detection of possible geological discontinuities, Rio, Patra, Greece.

Geophysical prospecting is a non catastrophic technique, applicable on a wide range of problems, including archaeological, environmental and geological problems. At Campus University of Patras, a detailed geophysical investigation applied for detection of possible existing geological discontinuities, which produced serious problems at buildings and main roads of Campus. As main technique used the electric mapping and electric imaging. These were applied on already prepared geophysical grids by measuring parallel profiles along and perpendicular to the geomagnetic north. The two geophysical grids were separated 100 meters away each other. Firstly, an electric mapping procedure took place by using twin-probe array with four electrodes in distance between 0.5-3 meters. As result was the recording of soil resistance on horizontal layer with constant depth. By processing the data through Geosoft Oasis Montaj software, the distribution of this physical property was illustrated on color scale maps. Secondly, electric imaging technique applied with twenty-five equal space electrodes along straight lines, with one meter space byusing the hybrid arrangement Wenner-Schlumberger (Stephanopoulos, 2002). As result was the recording of distribution of soil apparent resistivity on a vertical layer in eight separated depths. Resistivity calculated by processing imaging data through 2D mathematical algorithm based on least squares inversion (Res2Dinv). Furtherprocessing by Oasis Montaj, had as a result the production of horizontal slices (Stephanopoulos 2002) and 3D maps, where the resistivity distribution was illustrated on separated depths, in color and grey schedule format. The combined geophysical investigation with the contribution of the HVSR (Horizontal to Vertical Spectral Ratio) technique confirmed the existence of geological discontinuity.

EFFECT OF GEOLOGICAL STRUCTURE AND BLASTING PRACTICE IN FLY ROCK ACCIDENT AT JOHOR, MALAYSIA

Blasting operation is common method in hard rock excavation at civil engineering and mining sites. Rock blasting results in the fragmentation along with environmental hazards such as fly rock, ground vibration, air-blast, dust and fumes. Most of the common accidents associated with blasting are due to fly rock. A fly rock accident had occurred on 15 July 2015 at a construction site at Johor, Malaysia. Due to this accident, nearby factory worker was killed while two other workers were seriously injured after being hit by rock debris from an explosion at construction site, 200 m away from the factory. The main purpose of this study is to investigate the causes of fly rock accident based on geological structures and blasting practice such as blast design, pre inspection on geological structures, identifying danger zone due to blasting and communication and evacuation of personnel before blast. It can be concluded that fly rock could have been controlled in three stages; initial drilling of holes based on blast design, ensure limiting charge for holes having less burden or having geological discontinuity, and selecting proper sequence of initiation of holes.