Pore Water Pressure Contribution to Debris Flow Mobility

2009 ◽  
Vol 5 (4) ◽  
pp. 486-492 ◽  
Author(s):  
Chiara Deangeli
Keyword(s):  
Debris Flow ◽  
Pore Water ◽  
Pore Water Pressure ◽  
Water Pressure ◽  
Flow Mobility

Magnetic and pebble fabrics and origin of the Sunnybrook Till, Scarborough, Ontario, Canada

1987 ◽  
Vol 24 (10) ◽  
pp. 2038-2046 ◽  
Author(s):  
C. P. Gravenor ◽  
T. Wong
Keyword(s):  
Debris Flow ◽  
Pore Water ◽  
Pore Water Pressure ◽  
Water Pressure

The early Wisconsinan Sunnybrook Till is a mud-rich, pebble-poor, dark gray to gray–brown massive diamicton that is exposed in the Scarborough Bluffs, Ontario. It is interpreted here to be till.Previous separate, magnetic, and pebble fabric studies made on the till suggest a westward ice movement ranging from west of south to northwest. In this study, two dominant directions are found, northwest by west and northeast by north. Of these two directions, the northwest by west direction is the most common and this combined with the direction of shear in the underlying sediments and lithology of the till suggests that the glacier moved in a westerly direction.However, the fabrics are not typical of a lodgement till and to some extent resemble fabrics found in subaquatic debris-flow deposits. It is suggested that the glacier that deposited the Sunnybrook Till was buoyed up by high pore water pressure in the accumulating sediment at the sole of the glacier. Under these conditions, the till either flowed away from the zone of release at the base of the glacier and (or) was being lightly smeared by a partially grounded glacier.

Mechanism Study on Transformation of Landslide into Debris Flow based on Coulomb Particle Flow Theory

2011 ◽  
Vol 261-263 ◽  
pp. 1589-1593
Author(s):  
Zhen Qiang Ni ◽  
Ji Ming Kong ◽  
A. Fayou
Keyword(s):  
Debris Flow ◽  
Pore Water ◽  
High Speed ◽  
Pore Water Pressure ◽  
Water Pressure ◽  
Flow Theory ◽  
Particle Flow ◽  
Excess Pore Water Pressure ◽  
Flow Study ◽  
Excess Pore

The initiation is the core issue in debris flow study, it’s the basis of debris flow disaster prevention, and the research on transformation of landslide into debris flow is fundamental in debris flow study. Transformation of landslide into debris flow was a new topic which proposed in recent years, although it contained the previous areas of landslide-debris flow, something developed, it was more emphasis on the transformation process of landslide to debris flow. This paper proposed an ideal model from practical disaster, based on Coulomb Particle Flow Theory, we used large-scale finite difference software FLAC3D to analyze. From soil mechanics, to study on excess pore water pressure and the instability mechanism of slope, we got several laws. The results showed that, (a) the maximum excess pore water pressure occurred in the lower part of gravel slope body, with the increase of external load increasing, here would be the first liquefaction area; (b) crushed gravel soil had been largely destroyed when the slope in critical state, and at the same time internal energy of particles increased, cement ability decreased. With the rock sheared, gravitation energy of rock was released, high-speed gravel slope spilled into debris.

scholarly journals Grain Configuration Effect on Pore Water Pressure in Debris Flow

2021 ◽  
Vol 9 ◽  
Author(s):  
Taiqiang Yang ◽  
Daochuan Liu ◽  
Yong Li ◽  
Xiaojun Guo ◽  
Jun Zhang ◽  
...  
Keyword(s):  
Debris Flow ◽  
Pore Water ◽  
Pore Water Pressure ◽  
Water Pressure ◽  
Excess Pore Water Pressure ◽  
Low Dissipation ◽  
Grain Interaction ◽  
Coarse Grains ◽  
Function Relationship ◽  
Excess Pore

The generation and development of excess pore water pressure directly affects the grain interaction in debris flow, which can significantly reduce the friction strength and promote the movement of debris flow. It has been found that coarse grains favor the increase in excess pore water pressure, but the effect due to grain configuration is missing in studies. In order to study the influence of grain configuration, field investigations and laboratory tests were carried out for two typical cases, i.e., flow with coarse grains evenly mixed (case I) and flow with coarse grains floating on the surface (case II). The results show that case II generates much higher excess pore water pressure than case I. The variation of relative excess pore water pressure (Ur) with time (t) satisfies the power function relationship: Ur = mt–n. Case II often has a smaller n value, meaning a low dissipation rate of excess pore water pressure. This study is helpful for a better understanding of granular effects in debris flow.

scholarly journals Acceleration of Debris Flow Due to Granular Effect

2021 ◽  
Vol 9 ◽  
Author(s):  
Taiqiang Yang ◽  
Yong Li ◽  
Xiaojun Guo ◽  
Jun Zhang ◽  
Yu Jiang ◽  
...  
Keyword(s):  
Debris Flow ◽  
Pore Water ◽  
Slip Surface ◽  
Pore Water Pressure ◽  
Water Pressure ◽  
Coarse Grained ◽  
Flow Depth ◽  
Excess Pore Water Pressure ◽  
The Relationship ◽  
Excess Pore

Pore water pressure has been recognized as an important factor to enhance the mobility of debris flow moving in channel of very gentle slope. The creation and dissipation of pore water pressure are associated with interaction between grains. This study proposes a physical model for the pressure on mobility of flows with different granular configurations: the flow with overlying coarse-grained layer (i.e., inverse grading) and the flow with fully-mixed grains. The flow velocity is derived by the effective stress principle and the relationship between acceleration and pore water pressure is analyzed under different conditions. The results show that a high excess pore water pressure leads to high velocity of flow, and the pressure increases during the movement; and acceleration increases with time and flow depth under given pore water pressure. Moreover, compared with the flow with mixed grains, the flow with overlying coarse-grained layer is more effective to promote the excess pore water pressure and the liquefaction slip surface. Therefore, the internal drag reduction due to pore water pressure produces an acceleration effect on the flow.

TIME TO THE END OF PRIMARY CONSOLIDATION (EOP) OF SOFT CLAYEY SOILS: CONCERNING THE EFFECT OF ATTERBERG’S LIMIT AND CYCLIC LOADING HISTORY

2019 ◽  
Vol 128 (2B) ◽  
pp. 29-41
Author(s):  
Trần Thanh Nhàn
Keyword(s):  
Cyclic Loading ◽  
Pore Water ◽  
Pore Water Pressure ◽  
Water Pressure ◽  
Clayey Soils ◽  
Loading History ◽  
Cyclic Shear ◽  
Wide Range ◽  
Primary Consolidation ◽  
Time Required

In order to observe the end of primary consolidation (EOP) of cohesive soils with and without subjecting to cyclic loading, reconstituted specimens of clayey soils at various Atterberg’s limits were used for oedometer test at different loading increments and undrained cyclic shear test followed by drainage with various cyclic shear directions and a wide range of shear strain amplitudes. The pore water pressure and settlement of the soils were measured with time and the time to EOP was then determined by different methods. It is shown from observed results that the time to EOP determined by 3-t method agrees well with the time required for full dissipation of the pore water pressure and being considerably larger than those determined by Log Time method. These observations were then further evaluated in connection with effects of the Atterberg’s limit and the cyclic loading history.

Conjectures, Hypotheses, and Theories of Drumlin Formation (In memory of Stanislaw Baranowski)

1981 ◽  
Vol 27 (97) ◽  
pp. 503-505 ◽  
Author(s):  
Ian J. Smalley
Keyword(s):  
Shear Strength ◽  
Pore Water ◽  
Stress Level ◽  
Critical Stress ◽  
Pore Water Pressure ◽  
Water Pressure ◽  
Glacial Till ◽  
Forming Process ◽  
Stress Levels

AbstractRecent investigations have shown that various factors may affect the shear strength of glacial till and that these factors may be involved in the drumlin-forming process. The presence of frozen till in the deforming zone, variation in pore-water pressure in the till, and the occurrence of random patches of dense stony-till texture have been considered. The occurrence of dense stony till may relate to the dilatancy hypothesis and can be considered a likely drumlin-forming factor within the region of critical stress levels. The up-glacier stress level now appears to be the more important, and to provide a sharper division between drumlin-forming and non-drumlin-forming conditions.

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