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Rockfall in-situ tests

There are many variables that affect the fragmentation of a rock mass, doing complex their modeling. The most important are the rock strength and joints in detached mass, terrain and the characteristics of the impact (for instance, energy and angle of incidence), which vary from one point to another. There is rarely a chance to get these variables from retrospective analysis of cases inventoried, by lack of the necessary information. Therefore, there have done three tests of blocks launch in quarry to estimate the speed of the blocks and trajectory prediction and impact energies. These experiments are going to use to calibrate the propagation models.

Just before the test, rods surveying staffs and targets were placed spread over the scene. These items will be used as Ground Control Points (GCP) and/or as metrical scales in order to georeference all the photographic and video images. to An aerial photogrammetric campaign were done from a drone, capturing the full scene prior to any damage. During the test, these two systems were used punctually to position some important features (final position of blocks or fragments, impact points, etc). For instance, the drone flies once each 5 drops, in order to capture the block and fragments position. In addition to the oblique views and rockfall videos, if the drone covers the whole area, orthophotomaps have been produced. Apart from standard picture or video digital cameras (including two GOPRO Hero4), the propagation of each block was recorded by means of three high-speed video cameras (Sony NEX FS700R) that were set-up in convergent lines-of-sight.

 

A set of tests carried out in a limestone quarry located at Vallirana (Barcelona, Spain) the 17th and 18th of June, 2015. They will be used to calibrate and support the rock fall propagation models.

A total of 56 blocks ranging between 0.2 and 4.8 m3 were dropped from two slope profiles with different morphology and falling height (16.5 and 27.5m total fall). Trajectories of the blocks and velocities were tracked with three high-speed video cameras.

Some 43% of the blocks fragmented upon the impact on the ground. Most of the blocks were massive limestone although a small percentage of blocks displayed a variable amount of finite fissures. The characteristics of the blocks, in particular, the size, and the Schmidt L hammer rebound were measured before the tests.

Example of a video recorded at high resolution and 400fps corresponding to block 19

A set of tests carried out in a quarry located at Riudecols (Tarragona, Spain) the 8th of June, 2016.

A total of 38 blocks of dacites and 6 blocks of granite ranging between 0.2 and 5.8 m3 were dropped from an slope with 24 m falling height. Trajectories of the blocks and velocities were tracked with three high-speed video cameras.

Some 20% of the blocks fragmented upon the impact on the ground. Most of the blocks were massive although a small percentage of blocks displayed a variable amount of finite fissures. The characteristics of the blocks, in particular, the size, and the Schmidt L hammer rebound were measured before the tests.



Example of a video recorded from drone.

 

A fourth test was quarry out in a limestone quarry located at Vallirana (Barcelona, Spain) the 27th of Setember, 2017.

They will be used to calibrate and support the rock fall propagation models.

A total of 24 blocks ranging between 0.5 and 2.5 m3 were dropped from two slope profiles with different morphology and falling height (19m total fall).

Some 85% of the blocks fragmented upon the impact on the slope.

Ejemplo de video en alta definición registrado desde UAV