Incipient motion of Armorflex articulating concrete blocks on steep slopes

Armorflex is an articulating concrete block erosion protection measure that has been used as an alternative to riprap for many years. Even though extensive research and hydraulic testing have been conducted on Armorflex, the principal constraint on the use of concrete blocks has been the lack of information on prototype performance. Furthermore, there are no standards for Armorflex or articulating concrete block revetments in the South African National Standards, and design guidelines from Armorflex manufacturers are insufficient. The aim of this study was to improve the understanding of the critical flow conditions under which Armorflex blocks are lifted and removed by flowing water in open channel flow applications. Scaled laboratory tests were conducted on Armorflex 140 and Armorflex 180 blocks. Liu's theory of 1957 is applied in an attempt to define the point where block movement is initiated.

Oblique convergence causes both thrust and strike-slip ruptures during the 2021 M 7.2 Haiti earthquake

A devastating magnitude 7.2 earthquake struck Southern Haiti on 14 August 2021. The earthquake caused severe damages and over 2000 casualties. Resolving the earthquake rupture process can provide critical insights into hazard mitigation. Here we use integrated seismological analyses to obtain the rupture history of the 2021 earthquake. We find the earthquake first broke a blind thrust fault and then jumped to a disconnected strike-slip fault. Neither of the fault configurations aligns with the left-lateral tectonic boundary between the Caribbean and North American plates. The complex multi-fault rupture may result from the oblique plate convergence in the region that the initial thrust rupture is due to the boundary-normal compression and the following strike-slip faulting originates from the Gonâve microplate block movement, orienting towards the SW-NE direction. The complex rupture development of the earthquake suggests that the regional deformation is accommodated by a network of segmented faults with diverse faulting conditions.

Disrupting cortico-cerebellar communication impairs dexterity

To control reaching, the nervous system must generate large changes in muscle activation to drive the limb toward the target, and must also make smaller adjustments for precise and accurate behavior. Motor cortex controls the arm through projections to diverse targets across the central nervous system, but it has been challenging to identify the roles of cortical projections to specific targets. Here, we selectively disrupt cortico-cerebellar communication in the mouse by optogenetically stimulating the pontine nuclei in a cued reaching task. This perturbation did not typically block movement initiation, but degraded the precision, accuracy, duration, or success rate of the movement. Correspondingly, cerebellar and cortical activity during movement were largely preserved, but differences in hand velocity between control and stimulation conditions predicted from neural activity were correlated with observed velocity differences. These results suggest that while the total output of motor cortex drives reaching, the cortico-cerebellar loop makes small adjustments that contribute to the successful execution of this dexterous movement.

Preliminary Modeling of Rockfall Runout: Definition of the Input Parameters for the QGIS Plugin QPROTO

The identification of the most rockfall-prone areas is the first step of the risk assessment procedure. In the case of land and urban planning, hazard and risk analyses involve large portions of territory, and thus, preliminary methods are preferred to define specific zones where more detailed computations are needed. To reach this goal, the QGIS-based plugin QPROTO was developed, able to quantitatively compute rockfall time-independent hazard over a three-dimensional topography on the basis of the Cone Method. This is obtained by combining kinetic energy, passing frequency and detachment propensity of each rockfall source. QPROTO requires the definition of few angles (i.e., the energy angle ϕp and the lateral angle α) that should take into account all the phenomena occurring during the complex block movement along the slope. The outputs of the plugin are a series of raster maps reporting the invasion zones and the quantification of both the susceptibility and the hazard. In this paper, a method to relate these angles to some characteristics of the block (volume and shape) and the slope (inclination, forest density) is proposed, to provide QPROTO users with a tool for estimating the input parameters. The results are validated on a series of case studies belonging to the north-western Italian Alps.

Preliminary Modeling of Rockfall Runout: Definition of the Input Parameters for the Plugin QPROTO

The identification of the most rockfall-prone areas is the first step of the risk assessment procedure. In the case of land and urban planning, hazard and risk analyses involve large portions of territory and thus preliminary methods are preferred to define specific zones where more detailed computations are needed. To reach this goal, we developed the QGIS-based plugin QPROTO, able to quantitatively compute rockfall time-independent hazard over a three-dimensional topography on the basis of the Cone Method. This is obtained by combining kinetic energy, passing frequency and detachment propensity of each rockfall source. QPROTO requires the definition of few angles (i.e., the energy angle ϕ_p and the lateral angle α) that should take into account all the phenomena occurring during the complex block movement along the slope. The outputs of the plugin are a series of raster maps reporting the invasion zones and the quantification of both the susceptibility and the hazard. In this paper, we propose a method to relate these angles to some characteristics of the block (volume and shape) and the slope (inclination, forest density), to provide QPROTO users with a tool for estimating the input parameters. The results are validated on a series of case studies belonging to the North Western Italian Alps.

Rotational waves in fragmented and blocky geomaterials

<p>An important mechanism of oscillation and wave propagation in fragmented and blocky geomaterials such as rock masses and the Earth’s crust is the movement and rotation of the fragments/blocks as rigid bodies with deformation mainly residing at the interfaces. There are cases when the gouge in the interfaces is very weak and soft such that the resistance to parting the fragments is provided by the ambient compression which prevents the fragments/blocks from parting but allows their mutual rotation.</p><p> </p><p>In order to investigate this type of block movement we performed a series of vibration tests on blocky beams of different heights under horizontal vibrations of the base. The fragmented/blocky geomaterial was modelled using osteomorphic blocks. The osteomorphic blocks have a special shape that ensures topological interlocking. The assembly is an engineered material with internal architecture which captures the fragmented and blocky nature of geomaterials [1]. The observations using the DIC technique confirm that the blocks undergo relative rotational movement. The associated rotational waves travel within the assembly transferring the energy within the blocks. This is an extension of our previous analysis that established the formation of stationary points in fragmented bodies [2]. There is energy exchange between the assembly and the loading device. The energy calculations show that the energy fluctuates around a constant value. The spectrum of block oscillations exhibits the main peak corresponding to the driving frequency as well as secondary peaks that correspond to the multiples of the driving frequency. This is in line with our previous results on bilinear oscillators [3]. The results contribute to the understanding of wave propagation in blocky/fragmented rock mass and the Earth’s crust.</p><p> </p><ol><li>Pasternak, E., A.V. Dyskin and Y. Estrin, 2006. Deformations in transform faults with rotating crustal blocks. PAGEOPH, 163, 2011-2030.</li> <li>Dyskin, A.V., E. Pasternak and I. Shufrin, 2014. Structure of resonances and formation of stationary points in symmetrical chains of bilinear oscillators. Journal of Sound and Vibration 333, 6590–6606.</li> <li>Dyskin, A.V., E. Pasternak and E. Pelinovsky, 2012. Periodic motions and resonances of impact oscillators. Journal of Sound and Vibration 331(12) 2856-2873. ISBN/ISSN 0022-460X, 04/06/2012.</li> </ol><p> </p><p><strong>Acknowledgements</strong>. The authors acknowledge support from the Australian Research Council through project DP190103260. The authors acknowledge the UWA workshop in developing and manufacturing the experimental setup. In the experiments some setup fixtures previously developed by M. Khudyakov were used. AVD acknowledges the support from the School of Civil and Transportation, Faculty of Engineering, Beijing University of Civil Engineering and Architecture.</p>

Salt anomalies in potash beds of the Esterhazy Member, Devonian Prairie Evaporite Formation, Saskatchewan, Canada

The Esterhazy Member of the western Canada Prairie Evaporite has been mined underground for sylvite (KCl) since the early 1960s. Although the geology of the Esterhazy Member ore body is largely considered a regional flat lying continuous series of thin potash hosting beds, there are numerous occurrences where the ore has been either replaced or removed leaving behind uneconomical halite-rich sections. An explanation of the underlying controls on the formation of these salt anomalies has been somewhat elusive although the overwhelming assumption remains that these features developed in lows on a salina. This paper proposes that salt anomalies formed because of two processes, early compaction of carbonate shoals of the Winnipegosis Formation and tectonics that resulted in multiple stages of block movement during the deposition of the upper Prairie Evaporite. Since these two processes can result in a significantly different size to a salt anomaly, encountering one or the other type can have a significant effect on the economics of the ore body. This paper looks at some of the geological methods that might provide geologists with means to predicting salt anomalies.

Mechanism specifics of the landslide-hazardous massif limit state formation and landslide block displacement

In the landslide cycle of deep block movement development, the landslide process starts with the separation of the new landslide block from the bedrock massif, and it ends with the block displacement until the steady landslide head is formed in the hotbed (on the landslide slope). The initial stressed state in the bedrock massif with horizontal earth surface (before the landslide block forms) is controlled by the Mohr-Coulomb criterion. The landslide hotbed forming as well as the sliding basis appearing cause the change in the initial stress state and the formation of horizontally oriented dissipative blocks-structures. The principal stresses are concentrated on the boundary surfaces of these structures (which are of a circular cylindrical shape). The limit state forms along these boundary surfaces of the appropriate block in the local massif zone on the contact with the landslide hotbed. The displacement occurs along the same surfaces, provided the equilibrium is disturbed. In forming the limit state of the head scarp massif, the adjacent part of the landslide massif (within the boundaries of the earlier separated landslide block) acts as an additional load (creates an active vertical pressure from the landslide mass weight) to the horizon of the landslide basis. The bedrock massif interacts with the slope at the stage of preparing block displacement. The block limit state is achieved in case the head scarp height reaches its critical value (the slope edge is higher than the landslide head). Under the soil masses weight in the new landslide block, separated from the bedrock massif, as it subsides, the soil crushes in a lower part of the block, which has lost its balance, in the slide basis zone. The paper considers the conditions of the new landslide block formation, the beginning of block displacement process, the mechanism of interaction between blocks, the bedrock massif and the landslide body, which consists of earlier displaced landslide blocks. The paper also provides the rationale for the soil strength changes in the process of displacement and its significance in the landslide cycle completing, with comparing the results of theoretical and experimental studies.