Rock Slope Stability Evaluation on The Construction of New Road Shortcut 4 Border City of Singaraja – Mangwitani, Bali

Shortcut 4 new national road development project on Singaraja - Mangwitani section Bali found a potential rock slide slope problem. An outcrop of igneous rock with an intensive joint was not expected to be encountered previously. The excavation work in road construction had to pay attention to the stability of the resulting rock slope considering that apart from the potential for slope failure, rock slope could also threaten the bridge abutment building in front of it. The location of the rock slope was on the edge of Lake Bratan which is geologically part of the early Holocene volcanic rocks, namely mountain rocks composed of tuff, lava and volcanic breccia. Anisotropic andesite slope was controlled by a discontinuous plane with a certain pattern. Rock Quality Assessment was carried out by the Rock Mass Rating (RMR) method and Slope Mass Rating (SMR) for slope stability evaluation. The planar, tople and wedge potensial slope failure were evaluated. The potential for planar slope failure has a value of SMR 30.18 (Unstable), 57.6 (Partialy Stable) for wedge slope failure potential and 47.6 (Partialy Stable) for tople slope failure potential. The SMR value indicated that the rock slope requires engineering threatment to become stable.

Mitigation of post-fire erosion from terraced micro-catchments using timber barriers

<p>Recently burnt areas across the world have been documented to produce strong to extreme erosion responses but these responses are much better quantified for (micro-)plots and planar hillslopes than for convergent hillslopes and catchments. The same applies, mutatis mutandis, for the effectiveness of so-called emergency stabilization measures to reduce the risks of such strong to extreme responses. The only prior study in Portugal on the mitigation of post-fire erosion beyond the planar slope scale (i.e. swales of 500-800 m2) tested mulching with eucalypt logging residues. It found the treatment to be highly effective during the first two post-fire hydrological years in the sense that soil losses were, average, 88 and 77% smaller at the three mulched swales than at the 3 untreated swales. This in spite the mulch had been applied at reduced rate (2.4 Mg ha-1) compared to preceding, plot-scale studies in the region (>8 Mg ha-1). Against this background, the present study decided to test the effectiveness of log barriers to reduce post-fire erosion beyond the planar slope scale, in particular to provide evidence supporting the post-fire land management strategy that is being developed by the INTERREG-SUDOE project EPyRIS (SOE2/P5/E0811). The study area is located in the Aveiro District of central Portugal and burnt during early  September 2020. In the part of the burnt area that is being managed by the Portuguese Nature Conservation and Forests Institute (ICNF), three pairs of neighbouring micro-catchments of 0.3-0.8 ha and, in one exceptional case (due to run-on from a forest track), 2.7 ha were instrumented with sediment fences at their outlets before the occurrence of the first significant rainfall event after the wildfire. The barriers, however, could not be installed until after the subtropical storm ALPHA that hit continental Portugal on 18-19 September, also due to some delay in the contracting of a company that would have prior experience in implementing post-fire emergency stabilization measures. The sediment yields produced by this first post-fire rainfall event were used to select which of each pair of micro-catchments to be treated, i.e. the one producing most erosion. Furthermore, the initial sediment yields of the three to-be-treated micro-catchments were used to decide the number of barriers per catchment, ranging from one to three. Both these aspects of the experimental design imply that the quantification of (cost-)effectiveness will less straightforward than in case of a randomized design. In compensation, the upslope part of each barrier was covered with geotextile immediately after construction to estimate the barrier’s capacity to induce sediment deposition and, at the scale of the entire micro-catchment, its effectiveness to reduce post-fire sediment yields, even if sediment deposition will only be measured at the end of each hydrological. This envisaged poster will present the differences in sediment yields between the paired, treated and untreated micro-catchments during the first post-fire autumn-winter period, and discuss them in function of terrain characteristics of the micro-catchments, RS-based fire severity, rainfall regime and changes in surface cover as derived from RGB imagery acquired with a low-cost drone.</p>

Actuated Dual-Slip Model of Planar Slope Walking

The planar dual spring-loaded inverted pendulum (dual-SLIP) model is a well-established passive template of human walking on flat ground. This paper applies an actuated extension of the model to walking on inclines and declines to evaluate how well it captures the behavior observed in human slope walking. The motivation is to apply the template to improve control of humanoid robot walking and/or intent detection in exoskeleton-assisted walking. Gaits of the actuated planar dual-SLIP model are found via the solution of a constrained nonlinear optimization problem in ten parameters. The majority of those parameters define the actuation scheme that injects energy for incline walking and absorbs energy for decline walking to achieve periodic, nonconservative gaits. Solution gaits across the speed range of 1.0 to 1.6 ms and slope range of −10 to 10 degrees exhibit some of the characteristics of human walking, such as the effect of slope on stance duration, step frequency, and step length. Efforts to reduce the number of parameters optimized by enforcing relationships observed in the solution gaits proved unsuccessful, suggesting that future work must trade off model complexity with fidelity of representation of human behavior.

Steady turbulent density currents on a slope in a rotating fluid

We consider the dynamics of actively entraining turbulent density currents on a conical sloping surface in a rotating fluid. A theoretical plume model is developed to describe both axisymmetric flow and single-stream currents of finite angular extent. An analytical solution is derived for flow dominated by the initial buoyancy flux and with a constant entrainment ratio, which serves as an attractor for solutions with alternative initial conditions where the initial fluxes of mass and momentum are non-negligible. The solutions indicate that the downslope propagation of the current halts at a critical level where there is purely azimuthal flow, and the boundary layer approximation breaks down. Observations from a set of laboratory experiments are consistent with the dynamics predicted by the model, with the flow approaching a critical level. Interpretation in terms of the theory yields an entrainment coefficient $E\propto 1/\Omega $ where the rotation rate is $\Omega $. We also derive a corresponding theory for density currents from a line source of buoyancy on a planar slope. Our theoretical models provide a framework for designing and interpreting laboratory studies of turbulent entrainment in rotating dense flows on slopes and understanding their implications in geophysical flows.