Effect of Colluvial Soil Slope Fracture’s Anisotropy Characteristics on Rainwater Infiltration Process

The SEEP/W module of finite element software GEO-slope is used to analyze the effects of fracture depth, permeability coefficient ratio, fracture angle, and fracture number on the rainwater infiltration process. Moreover, the effect of fracture seepage anisotropy on slope stability is discussed combining with unsaturated seepage theory. The results show that the pore water pressure in the fracture increases rapidly with the rainfall until it changes from negative pressure to positive pressure. The greater the fracture depth is, the greater the pore water pressure in the fracture is, and the greater the infiltration depth at the time of rainfall stopping is. When the permeability coefficient is greater than the rainfall intensity, the permeability coefficient ratio has a great influence on the infiltration process of rainwater. The smaller the fracture angle is, the greater the maximum pore water pressure is in the fracture depth range, and the greater the depth of the positive pore water pressure is. However, with the increase of fracture angle, the infiltration depth decreases, and the range of the surface saturation area of slope increases obviously. With the increase of fracture density, the saturated positive pressure region is connected to each other in the slope. The influence range and the degree of the rainwater on the seepage field are larger and larger. There is a power relation between the saturation area and the fracture number, and also the concentration distribution of long fractures directly forms the large-connected saturated zone and raises groundwater. The range of the saturated zone and variation law of the pore water pressure under fracture seepage are obtained, which provide a reference for the parameter partition assignment of slope stability analysis under fracture seepage.

Download Full-text

Numerical Analysis of Characteristics of Moisture Migration in Soil Slope under Rainfall

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.501-504.1927 ◽

2014 ◽

Vol 501-504 ◽

pp. 1927-1931

Author(s):

Guang Ju Wen ◽

Wen Jie Deng ◽

Feng Wen

Keyword(s):

Pore Water ◽

Permeability Coefficient ◽

Slope Failure ◽

Pore Water Pressure ◽

Soil Mechanics ◽

Water Pressure ◽

Point Of View ◽

Moisture Migration ◽

Unsaturated Soil Mechanics ◽

Nonlinear Distribution

Based on the characteristics of slope failure induced by rainfall, from the point of view of moisture migration and combining unsaturated soil mechanics, the characteristics of moisture migration in slope under different rainfall intensities were analyzed by finite element method. The results reveal that under rainfall, the pore water pressure in slope is in layered distribution, and at the bottom of slope, the pore water pressure is the highest, the top is lower and the middle is the lowest. The volumetric water content is in nonlinear distribution and the degree of nonlinear in unsaturated area is higher than that of the saturated area. The permeability coefficient of soil rises with the increase of rainfall intensity, and when the soil is saturated, its permeability coefficient is saturate permeability coefficient.

Download Full-text

Influence of Layer Transition Zone on Rainfall-Induced Instability of Multilayered Slope

Lithosphere ◽

10.2113/2021/2277284 ◽

2021 ◽

Vol 2021 (Special 4) ◽

Author(s):

Zhi Dou ◽

Yimin Liu ◽

Xueyi Zhang ◽

Yashan Wang ◽

Zhou Chen ◽

...

Keyword(s):

Hydraulic Conductivity ◽

Transition Zone ◽

Pore Water ◽

Pore Water Pressure ◽

Water Pressure ◽

Layer Transition ◽

Infiltration Process ◽

Local Factor ◽

The Stability ◽

Different Thickness

Abstract Although numerous studies have been paid much attention to rainfall-induced instability of multilayered slopes, the interface between layers is generally considered to be “zero thickness”, and the layer transition zone between layers is neglected. In this study, the influence of the layer transition zone on the rainfall-induced instability of multilayered slope was investigated. A model was developed to simulate the rainfall infiltration process, the distribution of pore water pressure, and the stability of multilayered slope by coupling the unsaturated seepage model and the slope stability analysis method. Based on the analysis of the multilayered slopes with the different thickness ratios of the layer transition zone, a method for determining the critical thickness of the layer transition zone was proposed. The results showed that the layer transition zone had a significant influence on the stability of multilayered slope. It was found that the presence of the layer transition zone in the multilayered slope reduced the hydraulic conductivity of the slope and increased the rate of formation of transient saturated zone, which contributed to excess pore water pressure at the toe of the slope. The analysis of the local factor of safety (LFS) showed that when the thickness ratios of the layer transition zone were between 2.5% and 5%, the corresponding hydraulic conductivity of the slope decreased by 1%-2.5% and the maximum failure area of the slope during the rainfall was 25% of the slope. Our study highlighted the importance of the layer transition zone for the rainfall-induced instability of the multilayered slope.

Download Full-text

Experimental and Numerical Studies on Permeability Properties of Thermal Damaged Red Sandstone under Different Confining Pressures

Geofluids ◽

10.1155/2021/6693768 ◽

2021 ◽

Vol 2021 ◽

pp. 1-13

Author(s):

Zhenlong Zhao ◽

Hongwen Jing ◽

Guangping Fu ◽

Qian Yin ◽

Xinshuai Shi ◽

...

Keyword(s):

Numerical Modeling ◽

High Temperature ◽

Pore Water ◽

Permeability Coefficient ◽

Pore Water Pressure ◽

Water Pressure ◽

Darcy's Law ◽

Equivalent Permeability ◽

Red Sandstone ◽

Confining Pressures

The stability and safety of underground rock mass engineering are closely related to the permeability process of fluids and permeability properties of rocks. To reveal the flow behavior of fluid in thermal damaged rock, first, a rock seepage testing system was applied to study the permeability properties of red sandstone specimens after different high-temperature treatments from 200 to 800°C under different confining pressures of 10 to 30 MPa. Meanwhile, the microstructures of the red sandstone specimens were characterized by the mercury intrusion porosimetry (MIP) and scanning electron microscopy (SEM). Then, the permeability process of pore water pressure and the flow form of fluid also were investigated by the numerical modeling method. The results show that the permeability properties of red sandstone specimens after high-temperature exposure follow linear Darcy’s law, and the relation between confining pressures and equivalent permeability coefficient ( K 0 ) can be described by a power function. Besides, the phenomenon that microscopic structural deterioration is intensified with increasing temperature and the average pore size and porosity of the red sandstone specimens are both power functions is related to the equivalent permeability coefficient. Furthermore, the results of numerical modeling indicated that the flow field within the range affected by confining pressures gradually becomes stable and orderly from disorder, and flow lines of the fluid become smooth and straight, and perpendicular to the isosurface of pore water pressure as time goes by. Moreover, the nonlinear correlation between pore water pressure and seepage path length changes to a linear correlation, which is consistent with linear Darcy’s law.

Download Full-text

Influence of Water Saturation on Dynamic Responses of a Partially Sealed Tunnel

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.204-208.1510 ◽

2012 ◽

Vol 204-208 ◽

pp. 1510-1513

Author(s):

Min Jie Wen ◽

Zi Ping Su

Keyword(s):

Pore Water ◽

Permeability Coefficient ◽

Water Saturation ◽

Pore Water Pressure ◽

Water Pressure ◽

Great Influence ◽

Dynamic Responses ◽

Harmonic Load ◽

Homogeneous Fluid ◽

Influence Of Water

The mixture of water and gas is treated as a homogeneous fluid. Based on Boit’s theory, the influences of water saturation on the dynamic responses of a partially sealed tunnel are investigated in the frequency domain. By utilizing the continuous condition, the analytical solutions of the displacement, stress and pore water pressure of a partially sealed tunnel in the nearly saturated soil are derived subject to the harmonic load. On this basis, the influences of water saturation and permeability coefficient on the system responses are discussed by the numerical example. It is shown that the water saturation has a great influence on the stress and pore water pressure amplitudes. In addition, the permeability in the boundary of the tunnel is reasonably described by the permeability coefficient.

Download Full-text

The Analysis of Soil Slope Transient Seepage Consider the Change of Permeability Coefficient in Rainfall Condition

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.446-449.1888 ◽

2012 ◽

Vol 446-449 ◽

pp. 1888-1892

Author(s):

Zhong Ming He ◽

Yan Qi Qin ◽

Zhong Xin Cai

Keyword(s):

Pore Water ◽

Permeability Coefficient ◽

Pore Water Pressure ◽

Water Pressure ◽

Rainfall Infiltration ◽

Water Infiltration ◽

Soil Slope ◽

Seepage Field ◽

Finite Element Software ◽

Transient Seepage

In order to study the transient seepage field of soil slope when the saturated permeability coefficient changes under rainfall infiltration condition, the finite element software is used to build the numerical analysis model, the influence of slope seepage field and pore water pressure caused by the change of saturated permeability coefficient are emphatically discussed. The results show, under the condition of the certain sustained rainfall strength and rainfall duration, the rain water infiltration rate and infiltration depth are proportional to slope soil saturation permeability coefficient; Pore water pressure along the elevation direction shows the characteristic of “two big heads, among small” under the influence of rainfall infiltration.

Download Full-text

A model of landslide triggering by transient pressure waves

Hydrology and Earth System Sciences Discussions ◽

10.5194/hessd-11-2355-2014 ◽

2014 ◽

Vol 11 (2) ◽

pp. 2355-2390

Author(s):

G. W. Waswa ◽

S. A. Lorentz

Keyword(s):

Diffusion Model ◽

Pore Water ◽

Pore Water Pressure ◽

Water Pressure ◽

Ground Surface ◽

Shallow Landslides ◽

Diffusivity Coefficient ◽

Saturated Zone ◽

Transient Pressure ◽

Additional Energy

Abstract. Previous studies indicate that most rainfall-triggered shallow landslides are initiated by a spike in rainfall intensity, which does not usually occur at the beginning of a critical storm, within which the slide is triggered, but after several minutes (or hours) of the storm. The critical storm is also usually not positioned at the beginning of a rainfall season, but after several days of antecedent period. Rainfall triggers landslides via rapid increase in pore water pressure, commonly associated with the change in water content. Consequently, many hydrologic pressure wave models assume that rapid pore water pressure responses are as a result of rapid infiltration of rainwater. On the contrary, this paper argues that, based on the above timings of landslide occurrences and the knowledge that infiltration rate decays with the soil wetness, the rapid increase in pore water pressure that triggers shallow landslides is as a result of rapid introduction of additional energy into the tension saturated (or nearly saturated) zone by the intense rainfall at the ground surface, without infiltration. Antecedent and critical precipitations are significant in creating a tension saturated zone, necessary for rapid transmission of the introduced energy from the ground surface to the lower soil horizons during the critical storm. These arguments are supported by a newly proposed one-dimensional diffusion mathematical model, which, when solved for the appropriate boundary conditions, can yield pore water pressure at any time and depth of a tension-saturated soil profile, without infiltration. The newly proposed diffusion model is mathematically similar to Iverson's model (Iverson, 2000), except that the hydraulic diffusivity parameter in the latter is substituted with a newly proposed energy diffusivity coefficient in the former. A combination of the new diffusion model and the infinite slope model can predict the stability of a shallow slope as a result of transient pore water pressure.

Download Full-text

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

HUE UNIVERSITY JOURNAL OF SCIENCE TECHNIQUES AND TECHNOLOGY ◽

10.26459/hueuni-jtt.v128i2b.5424 ◽

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.

Download Full-text

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

Journal of Glaciology ◽

10.3189/s0022143000011552 ◽

1981 ◽

Vol 27 (97) ◽

pp. 503-505 ◽

Cited By ~ 1

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.

Download Full-text