Effects of an impermeable layer on pore pressure response to tsunami-like inundation

Tsunami hazards have been observed to cause soil instability resulting in substantial damage to coastal infrastructure. Studying this problem is difficult owing to tsunamis’ transient, non-uniform and large loading characteristics. To create realistic tsunami conditions in a laboratory environment, we control the body force using a centrifuge facility. With an apparatus specifically designed to mimic tsunami inundation in a scaled-down model, we examine the effects of an embedded impermeable layer on soil instability: the impermeable layer represents a man-made pavement, a building foundation, a clay layer and alike. The results reveal that the effective vertical soil stress is substantially reduced at the underside of the impermeable layer. During the sudden runup flow, this instability is caused by a combination of temporal dislocation of soil grains and an increase in pore pressure under the impermeable layer. The instability during the drawdown phase is caused by the development of excess pore-pressure gradients, and the presence of the impermeable layer substantially enhances the pressure gradients leading to greater soil instability. The laboratory results demonstrate that the presence of an impermeable layer plays an important role in weakening the soil resistance under tsunami-like rapid runup and drawdown processes.

Ice Lenses May Cause Many Arctic Landslides

When permafrost thaw reaches concentrations of ice underneath the surface, it may trigger local soil instability.

Large-scale physical modelling of static liquefaction in gentle submarine slopes

Planning a monitoring campaign for a natural submarine slope prone to static liquefaction is a challenging task due to the sudden nature of flow slides. Therefore, gaining a better insight by monitoring the changes in pore pressure and acceleration of the soil mass, prior to and at the onset of static liquefaction, of submerged model slopes in the laboratory, helps in quantifying the minimum required triggering levels and ultimately the development of effective margins of safety for this specific failure mechanism. This study presents a set of physical model tests of submarine flow slides in the large-scale GeoTank (GT) of Delft University of Technology, in which a tilting mechanism was employed to trigger static liquefaction in loosely packed sand layers. Novel sensors were developed to locally monitor the hydro-mechanical soil responses acting as precursors of the onset of instability. The measurements indicated that soil instability can initiate at overly gentle slope angles (6–10°) and generate significant excess pore water pressures that intensify the deformations to form a flow slide. Moreover, it was observed that the onset of instability and its propagation are highly dependent on the rate of shear stress change and the state of the soil. The obtained data can be used for the future validation of numerical models for submarine flow slides.

A proposal for modifying coppicing geometry in order to reduce soil erosion in the forest areas

A key factor to reduce soil erosion and soil instability is the conservation of forest areas. In the last years, in all Europe, forest logging has increased. The Italian situation is paradigmatic because more than 70% of the broadleaved forests are managed as coppices and new exploitations concerning biomass for energy production have tripled since 2001. The common coppicing method leaves standards uniformly distributed on the ground, but this geometry has proven to not play an effective role in soil erosion control. In this paper, we propose a different method for coppicing geometry, aimed to decrease the soil erosion risk. In particular, the theoretical framework of the model is presented here, employing the USLE framework and discussing a real case study, while the results of the experimental tests, which are in progress, will be discussed in future papers. The theoretical results seem to demonstrate the method’s validity, which is expected to reduce soil erosion amount in the range 29-42%.

A Geospatial Approach for Mapping the Earthquake-Induced Liquefaction Risk at the European Scale

This paper presents a geospatial methodology for zoning the earthquake-induced soil liquefaction risk at a continental scale and set-up in a Geographic Information System (GIS) environment by coupling data-driven and knowledge-driven approaches. It is worth mentioning that liquefaction is a phenomenon of soil instability occurring at a very local spatial scale; thus, the mega-zonation of liquefaction risk at a continental scale is a hard facing challenge. Since the risk from natural disasters is the convolution of hazard, vulnerability, and exposure, the liquefaction risk mapping is based on the combination of geospatial explanatory variables, available at the continental scale, of the previously listed three assumed independent random variables. First, by applying a prediction model calibrated for Europe, the probability of liquefaction is mapped for the whole continent. Then, the Analytical Hierarchy Process (AHP) is adopted to identify areas that have a high risk of liquefaction, taking into account proxy data for exposure. The maps are computed for different levels of severity of ground shaking specified by three return periods (i.e., 475, 975, and 2475 years). A broad variety of stakeholders would benefit from the outcomes of this study, such as civil protection organizations, insurance and re-insurance companies, and infrastructure operators.

Non-destructive and effective bridge monitoring through fast-falling weight deflectometer

<p>Recent collapses due to hydrogeological soil instability caused by extreme climate events recall the attention on a large-scale monitoring of the road infrastructures, particularly bridges and viaducts. Several studies focus the attention on both hydraulic and structural issues. In-depth systematic investigations do not suit this purpose because of time and cost investments usually carried out from local authorities. Increasing needs of available fast, low cost and reliable methods to investigate the performance of the road and bridges pushed towards new applications. The use of Fast-Falling Weight Deflectometer, conceived for airport pavements, is here applied as a non-destructive test to evaluate the stiffness of the deck and embankment of a bridge. The- Fast Falling Weight Deflectometer can produce a broadband, constant and replicable dynamic force, providing data in real time. An experimental campaign is here described on a case study of single span bridge.</p>

Landslide Failure Mechanisms of Dispersive Soil Slopes in Seasonally Frozen Regions

Hydraulic projects with dispersive soil in seasonally frozen regions are susceptible to landslide failures. The mechanism of such landslide failures has not been fully understood thus far; therefore, it was investigated in this study by using on-site surveys, laboratory tests, and theoretical calculations. The results showed that the landslides of dispersive soil in seasonally frozen regions could be categorized as shallow-seated landslides and deep-seated landslides. The preconditions for landslide occurrence were soil mass looseness and cracks, caused by freeze-thawing. The degradation of dispersive soil led to a rapid influx of water into the soil. The reason for shallow-seated landslides was that the numerous sodium ions present in the soil mass dissolved in water and damaged the soil structure, resulting in a substantial reduction in shear strength. The reason for deep-seated landslides, however, was the erosion due to rainfall infiltration after the shallow-seated landslides caused tensile cracks at the top of the slope, leading to soil instability. Landslide failures occurred when the dispersing soil slope underwent freeze-thawing and saturated soaking. The sliding surface was initiated at the top of the slope and gradually progressed to the bottom along the interface between the soil layers.

ANALISIS TIANG PANCANG SEBAGAI DINDING PENAHAN TANAH DENGAN MENGGUNAKAN PROGRAM METODE ELEMEN HINGGA

In recent years the number of infrastructure construction in Indonesia is surging. Sometimes soil excavation and filling at the construction site needed to be done. Disturbtion of soil may cause soil instability at the site so in order to prevent it from collapsing constructing a retaining wall is one possible solution like constructing a retaining wall from concrete piles on river flow area to replace the old soil retaining wall that broke down. Rainfall is simulated by staging the rise of both groundwater and river surface level. The concrete piles used have dimension of 400x400 mm and 0,8 m between each pile and topped of with capping beam 0,8 m wide and 0,5 m thick. Calculation is done by program for deflection and moment of pile with Mohr-Coulomb model. Deflection and moment of pile when groundwater level is at -6 meter is 2,376 cm and 115,40 kNm, then 4,245 cm and 199,95 kNm when groundwater level reaches ±0 meter. The results will then be compared agaisnt maximum deflection and moment allowed for the pile. After analysis is done it is found that both deflection and moment experienced a greater jump in value when groundwater level is nearing top of pile. AbstrakBeberapa tahun belakangan banyak pembangunan yang berjalan di Indonesia. Namun terkadang kontur tanah pada lokasi pembangunan kurang sesuai dengan kebutuhan desain sehingga dilakukan penggalian atau pengurugan. Pengubahan kontur tanah dapat menyebabkan ketidakstabilan pada tanah di lokasi sehingga salah satu solusi untuk mencegah terjadinya longsor pada tanah adalah dengan membuat dinding penahan tanah. Salah satu hal yang menarik adalah pembangunan dinding penahan tanah dari tiang pancang beton di daerah aliran sungai untuk menggantikan dinding penahan tanah lama yang rusak. Perhitungan akan mensimulasikan terjadinya hujan sehingga terjadi peningkatan muka air tanah dan permukaan sungai secara bertahap. Tiang yang digunakan pada pemodelan memiliki ukuran 400x400 mm dengan jarak antar tiang 0,8 meter yang dihubungkan oleh capping beam selebar 0,8 meter dan tebal 0,5 meter. Perhitungan dilakukan dengan program untuk mencari defleksi dan momen pada tiang pada pemodelan Mohr-Coulomb. Defleksi dan momen yang terjadi pada tiang saat muka air tanah -6 meter sebesar 2,376 cm dan 115,40 kNm, kemudian saat ±0 meter sebesar 4,245 cm dan 199,95 kNm. Hasil defleksi dan momen kemudian dibandingkan terhadap syarat batas yang sudah ditentukan sebelumnya. Setelah analisis dilakukan ditemukan bahwa kenaikan defleksi dan momen paling besar terjadi pada tahap dimana air naik mendekati puncak tiang.

Sensors applied in the detection of physical changes at heritage buildings

&lt;p&gt;Heritage buildings are susceptible to environmental impacts, and many of the stone structures show intense damage due to weathering, soil instability or improper use. The detection of changes has primary importance in the understanding of deterioration processes, and it provides essential information for the preservation of these structures. The application of destructive techniques to assess the condition of the materials of these heritage structures are not feasible and in most cases, not permitted. Consequently, monitoring of the health of the construction material and the structure require techniques that are not destructive and automatically collects data from the sites. The study provides an overview of sensors that could be applied in monitoring of the conditions of cultural heritage structures. From the methods of placing sensors at sites to available data collection system &amp;#8211; the entire process will be overviewed. Applications of spectroscopic sensors for in situ and real-time analysis of critical colorimetric parameters of building materials will be presented. Application of artificial intelligence-based data processing in the prediction of material degradation is also discussed. Optical detectors of remote sensing techniques applied in monitoring of heritage buildings are also addressed. The financial support of National Research, Development and Innovation (NKFI) Fund (K 116532) is appreciated.&lt;/p&gt;