The Basal Friction Coefficient of Granular Flows With and Without Excess Pore Pressure: Implications for Pyroclastic Density Currents, Water‐Rich Debris Flows, and Rock and Submarine Avalanches

2020 ◽  
Vol 125 (12) ◽  
Author(s):  
Eric C. P. Breard ◽  
Josef Dufek ◽  
Luke Fullard ◽  
Alexandre Carrara
Keyword(s):  
Friction Coefficient ◽  
Pore Pressure ◽  
Debris Flows ◽  
Granular Flows ◽  
Excess Pore Pressure ◽  
Pyroclastic Density Currents ◽  
Density Currents ◽  
Basal Friction ◽  
Excess Pore

Effect of excess pore pressure on the long runout of debris flows over low gradient channels: A case study of the Dongyuege debris flow in Nu River, China

Geomorphology ◽  
2018 ◽  
Vol 308 ◽  
pp. 40-53 ◽  
Author(s):  
Zhen-Hua Zhou ◽  
Zhe Ren ◽  
Kun Wang ◽  
Kui Yang ◽  
Yong-Jun Tang ◽  
...  
Keyword(s):  
Debris Flow ◽  
Pore Pressure ◽  
Debris Flows ◽  
Excess Pore Pressure ◽  
Long Runout ◽  
Nu River ◽  
Excess Pore

Vibro-Stone Column Reinforcement Mechanism and Numerical Analysis

2012 ◽  
Vol 446-449 ◽  
pp. 1940-1943
Author(s):  
Yang Liu ◽  
Hong Xiang Yan
Keyword(s):  
Numerical Simulation ◽  
Numerical Analysis ◽  
Pore Pressure ◽  
Numerical Procedure ◽  
Numerical Results ◽  
Excess Pore Pressure ◽  
Stone Column ◽  
Reinforcement Mechanism ◽  
Consolidation Theory ◽  
Excess Pore

Numerical simulation of vibro-stone column is taken to simulate the installation of vibro-stone column. A relationship based on test is adopted to calculate the excess pore pressure induced by vibratory energy during the installation of vibro-stone column. A numerical procedure is developed based on the formula and Terzaghi-Renduric consolidation theory. Finally numerical results of composite stone column are compared single stone column.

scholarly journals The consolidation of soils under stochastic initial excess pore pressure

1993 ◽  
Vol 17 (11) ◽  
pp. 609-612 ◽  
Author(s):  
A.A. Darrag ◽  
M.A. El Tawil
Keyword(s):  
Pore Pressure ◽  
Excess Pore Pressure ◽  
Excess Pore

The numerical reconstruction of three past eruptions at Gede volcano (Indonesia)

2021 ◽  
Author(s):  
Eleanor Tennant ◽  
Susanna Jenkins ◽  
Annie Winson ◽  
Christina Widiwijayanti ◽  
Hendra Gunawan ◽  
...  
Keyword(s):  
Epistemic Uncertainty ◽  
Source Parameters ◽  
Frictional Resistance ◽  
Collapse Mechanism ◽  
Eruption Dynamics ◽  
Pyroclastic Density Currents ◽  
Density Currents ◽  
Basal Friction ◽  
Column Collapse ◽  
Hazard And Risk

<p>Understanding past eruption dynamics at a volcano is crucial for forecasting the range of possible future eruptions and their associated hazards and risk. In this work we reconstructed pyroclastic density currents and tephra fall from three eruptions at Gede volcano, Indonesia with the aim of gaining further insight into past eruptions and identifying suitable eruption source parameters for future hazard and risk assessment. Gede has the largest number of people living within 100 km of any volcano worldwide, and has exhibited recent unrest activity, yet little is known about its eruption history. For pyroclastic density currents, we used Titan2D to reconstruct geological deposits dated at 1200 and c. 1000 years BP. An objective and quantitative multi-criteria method was developed to evaluate the fit of over 300 pyroclastic density current (PDC) model simulations to field observations. We found that the 1200 years BP geological deposits could be reproduced with either a dome collapse or column collapse as the generation mechanism although a relatively low basal friction of 6 degrees would suggest that the PDCs were markedly mobile. Lower basal frictions may reflect the occurrence of previous PDCs that smoothed the path, reducing frictional resistance and enabling greater runout for the reconstructed unit. For the 1,000 years BP PDC, a column collapse mechanism and higher basal friction was required to fit the geological deposits. In agreement with previous studies, we found that Titan2D simulations were most sensitive to the basal friction; however, we also found that the internal friction – often fixed and considered of low influence on outputs - can have a moderate effect on the simulated average deposit thickness. We used Tephra2 to reconstruct historic observations of tephra dispersed to Jakarta and other towns during the last known magmatic eruption of Gede in 1948. In the absence of observable field deposits, or detailed information from the published literature, we stochastically sampled eruption source parameters from wide ranges informed by analogous volcanic systems. Our modelling suggests that the deposition of tephra in Jakarta during the November 1948 eruption was a very low probability event, with approximately a 0.03 % chance of occurrence. Through this work, we exemplify the reconstruction of past eruptions when faced with epistemic uncertainty, and improve our understanding of past eruption dynamics at Gede volcano, providing a crucial step towards the reduction of risk to nearby populations through volcanic hazard assessment.</p>

scholarly journals How deep does sand deposits in the Alentejo basin (Gulf of Cadiz) reach? Evaluating slope stability from bottom-current activities through time

2020 ◽  
Author(s):  
Davide Mencaroni ◽  
Roger Urgeles ◽  
Jonathan Ford ◽  
Jaume Llopart ◽  
Cristina Sànchez Serra ◽  
...  
Keyword(s):  
Pore Pressure ◽  
Sediment Supply ◽  
Excess Pore Pressure ◽  
Bottom Current ◽  
Gulf Of Cadiz ◽  
Strait Of Gibraltar ◽  
Gulf Of Cádiz ◽  
The Stability ◽  
Iberian Margin ◽  
Excess Pore

<p>Contourite deposits are generated by the interplay between deepwater bottom-currents, sediment supply and seafloor topography. The Gulf of Cadiz, in the Southwest Iberian margin, is a famous example of extensive contourite deposition driven by the Mediterranean Outflow Water (MOW), which exits the Strait of Gibraltar, flows northward following the coastline and distributes the sediments coming from the Guadalquivir and Guadiana rivers. The MOW and related contourite deposits affect the stability of the SW Iberian margin in several ways: on one hand it increases the sedimentation rate, favoring the development of excess pore pressure, while on the other hand, by depositing sand it allows pore water pressure to dissipate, potentially increasing the stability of the slope.</p><p>In the Gulf of Cadiz, grain size distribution of contourite deposits is influenced by the seafloor morphology, which splits the MOW in different branches, and by the alternation of glacial and interglacial periods that affected the MOW hydrodynamic regimes. Fine clay packages alternates with clean sand formations according to the capacity of transport of the bottom-current in a specific area. Generally speaking, coarser deposits are found in the areas of higher MOW flow energy, such as in the shallower part of the slope or in the area closer to the Strait of Gibraltar, while at higher water depths the sedimentation shifts to progressively finer grain sizes as the MOW gets weaker. Previous works show that at present-day the MOW flows at a maximum depth of 1400 m, while during glacial periods the bottom-current could have reached higher depths.</p><p>In this study we derived the different maximum depths at which the MOW flowed by analyzing the distribution of sands at different depths along the Alentejo basin slope, in the Northern sector of the Gulf of Cadiz.</p><p>Here we show how changes in sand distribution along slope, within the stratigraphic units deposited between the Neogene and the present day, are driven by glacial – interglacial period alternation that influenced the hydrodynamic regime of the MOW.</p><p>By deriving the depositional history of sand in the Alentejo basin, we are able to correlate directly the influence that climatic cycles had on the MOW activity. Furthermore, by interpreting new multi-channel seismic profiles we have been able to derive a detailed facies characterization of the uppermost part of the Gulf of Cadiz.</p><p>An accurate definition of sand distribution along slope plays an important role in evaluating the stability of the slope itself, e.g. to understand if the sediments may be subjected to excess pore pressure generation. As sand distribution is a direct function of the bottom-current transport capacity, the ultimate goal of this study is to understand how climate variations can affect the stability of submarine slope by depositing contourite-related sand.</p>

scholarly journals Consolidated and Undrained Ring Shear Tests on the Sliding Surface of the Hsien-du-shan Landslide in Taiwan

Geofluids ◽  
2018 ◽  
Vol 2018 ◽  
pp. 1-12 ◽  
Author(s):  
Hung-Ming Lin ◽  
Jian-Hong Wu ◽  
Erik Sunarya
Keyword(s):  
Pore Pressure ◽  
Rock Avalanche ◽  
Excess Pore Pressure ◽  
High Water Content ◽  
Sliding Surface ◽  
Shear Tests ◽  
Typhoon Morakot ◽  
Ring Shear ◽  
Ring Shear Tests ◽  
Excess Pore

A new consolidated undrained ring shear test capable of measuring the pore pressures is presented to investigate the initiation mechanism of the Hsien-du-shan rock avalanche, triggered by Typhoon Morakot, in southern Taiwan. The postpeak state of the landslide surface between the Tangenshan sandstone and the remolded landslide gouge is discussed to address the unstable geomorphological precursors observed before the landslide occurred. Experimental results show that the internal friction angle of the high water content sliding surface in the total stress state, between 25.3 and 26.1°, clarifies the reason of the stable slope prior to Typhoon Morakot. In addition, during the ring shear tests, it is observed that the excess pore pressure is generated by the shear contractions of the sliding surface. The remolded landslide gouge, sheared under the high normal stress, rendered results associated with high shear strength, small shear contraction, low hydraulic conductivity, and continuous excess pore pressure. The excess pore pressure feedback at the sliding surface may have accelerated the landslide.

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