Rock glacier sediment, kinematics and geomorphometry: a study case from the Eastern Italian Alps

<p>Rock glaciers are important geomorphological structures of high mountain environments and fundamental indicators for permafrost. They consist of unconsolidated rock debris – generally derived from talus or till - held together by ice, moving slowly downslope due to the gravitation in combination with uncountable freeze-thaw-cycles in the active layer. The downslope movement of rock glaciers leads to lobate structures with depressed areas as well as ridges where the sediments tend to accumulate, creating a typical surface morphology defined as "ridges and furrows". This study focuses on the analysis of one rock glacier system located in the Pfitsch/Vizze valley (South Tyrol), in the Eastern Italian Alps.  The debris in this area comprises exclusively the granitic Central Gneiss of the Tauern window. Rock glacier sediment derives from talus, consisting essentially of more or less foliated to planar angular material, which was essentially formed by frost weathering. The size and shape of sediments present at the surface of the rock glacier system were analyzed in correlation with displacement and geomorphometry, with the hypothesis that sediments shape and size at different sites across the rock glacier might relate to its past and present dynamics. The displacement analyses were carried out to quantify rock glaciers movements during the last 20 years, and the geomorphometrical characteristics were investigated to identify specific geometrical attributes that may be linked to internal ice changes.<br>Clasts analysis showed how rock glacier sediments are very heterogeneous, with dimensions being mainly determined by transport distance, and sphericity and roundness by lithology. A role of sediments characteristics on displacement rate did not turn out evident. Convexities and concavities observed on the study site are apparently created respectively by the accumulation of sediments and the collapse of the structure due to the internal ice melting. Indeed, the recent, marked increase in air temperature observed in the last decades in the Alps has likely caused an accelerated ice melting in the less protected – in terms of solar radiation – rock glaciers, as is the case for our study area. Sediments here are no longer bound by ice and have become rather unstable. Therefore, the monitoring of rock glaciers is fundamental to anticipate future changes in the type and magnitude of natural hazards originating at high elevations, as thicker layers of sediments are becoming increasingly unstable.</p>

Pemanfaatan Bambu Tabadiku sebagai Agregat Kasar Pada Pengujian Kuat Tekan Beton

The use of bamboo as building materials has occurred for a long period, especially in a simple construction system. Bamboo can be utilized as a building material due to its advantages. One of the advantages is that bamboo has a significantly low density so it can reduce the density of concrete whose main material is gravel. Gravel is a natural building material is formed from unconsolidated rock fragments, such as rock pieces or small rocks. Gravel is commonly found in Indonesia because there is a lot of availability. This research aims to utilize local bamboo resources as building materials. Bamboo is used as an alternative substitute for gravel aggregate in the concrete mixing. The research method was experimental laboratory work. The results showed that the use of bamboo as an aggregate can only be used in non-structures, this is because the rate of absorption of bamboo against water is quite high. While the compressive strength of the concrete produced by mixing 100 % bamboo aggregate has an average value of 3.09 MPa and mixing 50 % of bamboo has an average value of 6.01 MPa. Therefore, the quality of the concrete cannot be used for building structures, but only be used in non-structural buildings.

THM Experiment for the Investigation of Freeze-Thaw Processes in Soils and Grouting Materials

<p>Freeze-thaw processes induced in the vicinity of borehole heat exchangers (BHE) as a result of operating temperatures below 0 °C can significantly affect the compound structure consisting of the BHE pipes, the cement-based grouting material as well as the surrounding soil. The hydraulic integrity of such systems is not ensured anymore and its thermal efficiency could be impaired. However, the knowledge on freezing and thawing processes in porous media, such as the grout and unconsolidated rock materials, is still incomplete. The content of unfrozen water has a strong impact on material properties influencing the overall heat and mass transfer processes. Moreover, freezing strongly depends on various boundary conditions such as soil type or pore water chemistry. Accordingly, it is essential to have adequate information about the freezing interval for different boundary conditions, which describe the transition from pure liquid water to the ice phase and vice versa.</p><p>Therefore, a thermo-hydraulic-mechanical (THM) experiment has been developed and is used to gain a more detailed insight into freezing processes in artificial grouts and unconsolidated rock materials. It consists of a modified triaxial test system, which can carry cylindrical samples with a diameter of up to 100 mm and a height of up to 200 mm. A confining pressure of up to 16 bar can be gained by a plunger system. The confining pressure liquid (water-glycol-mixture) can be tempered down to -25 °C and is used to induce freezing conditions on the lateral surface of the sample. Mechanical parameters such as the freeze pressure are recorded by an axial load sensor and a displacement sensor. Besides, the radial deformation can be observed by the volume displacement of the confining liquid. Moreover, the hydraulic conductivity of the sample is determined according to DIN EN ISO 17892 (2019). The fluid temperatures during the flow-through experiment can be varied between 5 °C and 25 °C to represent natural groundwater temperatures. In addition to that, the freeze-thaw experiment is equipped with an ultrasonic measurement device: In the observed temperature range, the wave velocity in solid particles is constant and not affected by temperature changes. However, with descending temperature, the ice content increases, which leads to an improved cross-linking of the solid soil particles. As a consequence, the bulk P-wave velocity increases with decreasing unfrozen water content. Hence, this relationship can be used to determine the content of unfrozen water during a freeze-thaw cycle.</p><p>At this time, the first experiments are conducted with this novel device. Consequently, initial results will be presented at the conference. Moreover, the results of the THM experiments will be implemented in numerical models, which allow for an upscaling of the experimental findings to real scale applications.</p>

The Role of Case Hardening in the Preservation of the Cavates and Petroglyphs of Bandelier

ABSTRACTBandelier National Monument (BNM) was created to protect an extraordinary inventory of archaeological resources carved in the Tshirege Member of the Bandelier Tuff. These include more than one thousand excavated chambers, called cavates, used for dwelling, storage, and textile production. The glass-rich tuffs at the base of the Tshirege Member are poorly consolidated and susceptible to erosion by wind, rain, and mechanical abrasion, with resultant loss of cultural material. However, rock surfaces develop protective weathering rinds that are resistant to erosion. Using optical microscopy, SEM-EDS, XRD, and electron microprobe analysis, we determined that this rind consists of clay and silt sediments colonized by lichens and other surface biota, accompanied by the precipitation of secondary minerals in the near-surface pore space. Scoping experiments focused on glass-organic acid interactions indicate that oxalic acid excreted by microbial crust constituents catalyzes biogeochemical reactions that lead to the preferential dissolution of Si, Al, and Fe components of the volcanic glass; these cations become available for precipitation of opal, and smectite and sepiolite clays. Enzyme assays that quantify biological activity at outcrop surfaces indicate that microbial populations initially thrive as they derive nutrients from the dissolution reactions of the glass, but activity starts to decline as precipitation of secondary minerals limits access to new sources of nutrients, so that alteration processes are self-limiting. As case hardening progresses, imbibition rates at the surface decrease, and the erosion resistance of the altered surfaces is substantially improved. This article presents summary results of research conducted over a period of five years to characterize the roles of lichens and other microflora in rind formation, and the resulting contributions to tuff stability. The interaction of lichens and other microflora with rock surfaces in archaeological sites and monuments is usually explored in terms of biodeterioration and consequent damage. However, this study shows that, under some circumstances, lichens and microflora provide a level of erosion protection to relatively porous and unconsolidated rock strata that outweighs their biodeteriorative effects.