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.

Characteristics of Liquefaction Resistance for the Saturated Silty Soil Ground Treated by Compacted Gravel Pile Composite Foundation

2012 ◽  
Vol 446-449 ◽  
pp. 2573-2576
Author(s):  
Yong Xiang Zhan ◽  
Hai Lin Yao ◽  
Guan Lu Jiang
Keyword(s):  
Pore Water ◽  
High Speed ◽  
Pore Water Pressure ◽  
Water Pressure ◽  
Composite Foundation ◽  
Excess Pore Water Pressure ◽  
Silty Soil ◽  
Input Acceleration ◽  
Gravel Pile ◽  
Excess Pore

Based on Beijing-Shanghai high speed railway, the numerical simulation mainly researched on the seismic behavior for the saturated silty soil ground, which was treated by compacted gravel pile composite foundation. It has been analyzed that the region of liquefaction distribution and the transferring rule of excess pore water pressure under a series of input acceleration seismic loads in the treated and untreated foundation. The research results indicate that the untreated saturated silty soil ground is almost whole liquefaction when the amplitude of input acceleration is more than 0.15 g. While for compacted gravel pile composite foundation, out of treated region is less liquefaction when the amplitude of input acceleration is 0.15 g, with the increasing of input acceleration, liquefaction region is further more and gradually expands to the inner soil between piles, and compacted gravel pile composite foundation is only partial liquefaction when the amplitude of input acceleration is 0.25g. Excess pore water pressure is increased with the increasing of input acceleration seismic load, and the increasing of excess pore water pressure can be restrained effectively by compacted gravel pile composite foundation, and the quality of liquefaction resistance is improved. The design of compacted gravel pile composite foundation can satisfy the seismic requirements of Beijing-Shanghai high speed railway under the condition of 7 degree seismic fortification.

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.

Stress–strain pattern–based criterion to assess cyclic shear resistance of soil from laboratory element tests

2016 ◽  
Vol 53 (9) ◽  
pp. 1460-1473 ◽  
Author(s):  
Dharma Wijewickreme ◽  
Achala Soysa
Keyword(s):  
Pore Water ◽  
Pore Water Pressure ◽  
Water Pressure ◽  
Shear Stiffness ◽  
Large Strains ◽  
Fundamental Parameter ◽  
Stress Strain ◽  
Cyclic Shear ◽  
Excess Pore Water Pressure ◽  
Excess Pore

The cyclic shear response of soils is commonly examined using undrained (or constant-volume) laboratory element tests conducted using triaxial and direct simple shear (DSS) devices. The cyclic resistance ratio (CRR) from these tests is expressed in terms of the number of cycles of loading to reach unacceptable performance that is defined in terms of the attainment of a certain excess pore-water pressure and (or) strain level. While strain accumulation is generally commensurate with excess pore-water pressure, the definition of unacceptable performance in laboratory tests based purely on cyclic strain criteria is not robust. The shear stiffness is a more fundamental parameter in describing engineering performance than the excess pore-water pressure alone or shear strain alone; so far, no criterion has considered shear stiffness to determine CRR. Data from cyclic DSS tests indicate consistent differences inherent in the patterns between the stress–strain loops at initial and later stages of cyclic loading; instead of relatively “smooth” stress–strain loops in the initial parts of loading, nonsmooth changes in incremental stiffness showing “kinks” are notable in the stress–strain loops at large strains. The point of pattern change in a stress–strain loop provides a meaningful basis to determine the CRR (based on unacceptable performance) in cyclic shear tests.

Consolidation Theory for Composite Ground with Granular Columns Based on Different Calculation Models

2011 ◽  
Vol 261-263 ◽  
pp. 1534-1538
Author(s):  
Yu Guo Zhang ◽  
Ya Dong Bian ◽  
Kang He Xie
Keyword(s):  
Pore Water ◽  
Analytical Solutions ◽  
Pore Water Pressure ◽  
Water Pressure ◽  
Vertical Flow ◽  
Excess Pore Water Pressure ◽  
Consolidation Theory ◽  
Composite Ground ◽  
Granular Column ◽  
Excess Pore

The consolidation of the composite ground under non-uniformly distributed initial excess pore water pressure along depth was studied in two models which respectively considering both the radial and vertical flows in granular column and the vertical flow only in granular column, and the corresponding analytical solutions of the two models were presented and compared with each other. It shows that the distribution of initial excess pore water pressure has obvious influence on the consolidation of the composite ground with single drainage boundary, and the rate of consolidation considering the radial-vertical flow in granular column is faster than that considering the vertical flow only in granular column.

The Test Study to the Changes of Excess Pore Water Pressure during Precast Pile Construction

2012 ◽  
Vol 193-194 ◽  
pp. 1010-1013
Author(s):  
Shu Qing Zhao
Keyword(s):  
Pore Water ◽  
Clayey Soil ◽  
Pore Water Pressure ◽  
Water Pressure ◽  
Excess Pore Pressure ◽  
Soil Pressure ◽  
Excess Pore Water Pressure ◽  
Test Study ◽  
Excess Pore

The construct to precast pile in thick clayey soil can cause the accumulation of excess pore water pressure. The high excess pore pressure can make soil, buildings and pipes surrounded have large deflection, even make them injured. Combining with actual projects, this paper presents an in-situ model test on the changes of excess pore water pressure caused by precast pile construct. It is found that the radius of influence range for single pile driven is about 15m，the excess pore water pressure can reach or even exceed the above effective soil pressure, and there are two relatively stable stages.

A Practical Saturated Sand Elastic-Plastic Dynamic Constitutive Model and Application

2012 ◽  
Vol 446-449 ◽  
pp. 1621-1626 ◽  
Author(s):  
Yan Mei Zhang ◽  
Dong Hua Ruan
Keyword(s):  
Constitutive Model ◽  
Pore Water ◽  
Pore Water Pressure ◽  
Water Pressure ◽  
Stone Columns ◽  
Saturated Sand ◽  
Multidimensional Model ◽  
Excess Pore Water Pressure ◽  
Elastic Plastic ◽  
Excess Pore

A practical saturated sand elastic-plastic dynamic constitutive model was developed on the base of Handin-Drnevich class nonlinear lag model and multidimensional model. In this model, during the calculation of loading before soil reaches yielding, unloading and inverse loading, corrected Handin-Drnevich equivalent nonlinear model was adopted; after soil yielding, based on the idea of multidimensional model, the composite hardening law which combines isotropy hardening and follow-up hardening, corrected Mohr-Coulomb yielding criterion and correlation flow principle were adopted. A fully coupled three dimension effective stress dynamic analysis procedure was developed on the base of this model. The seismic response of liquefaction foundation reinforced by stone columns was analyzed by the developed procedure. The research shows that with the diameter of stone columns increasing, the excess pore water pressure in soil between piles decreases; with the spacing of columns increasing, the excess pore water pressure increases. The influence of both is major in middle and lower level of composite foundation.

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