Dimensional analysis of pore-water pressure response in a vegetated infinite slope

2019 ◽  
Vol 56 (8) ◽  
pp. 1119-1133 ◽  
Author(s):  
S. Feng ◽  
H.W. Liu ◽  
C.W.W. Ng
Keyword(s):  
Dimensional Analysis ◽  
Pore Water ◽  
Water Uptake ◽  
Pore Water Pressure ◽  
Water Pressure ◽  
Root Water Uptake ◽  
Water Transfer ◽  
Dimensionless Numbers ◽  
Influence Zone ◽  
Centrifuge Tests

Pore-water pressure (PWP) induced by root water uptake has usually been investigated by individual physical quantities. Limited dimensional analysis has been available for investigating PWP response in a vegetated slope. In this study, dimensional analysis was conducted to explore dimensionless numbers controlling PWP distributions in a vegetated slope. Three dimensionless numbers governing unsaturated seepage were proposed, including capillary effect number (CN, describing the relative importance of water flow driven by PWP gradient over that driven by gravity), root water uptake number (RN, representing the effects of root water uptake), and water transfer–storage ratio (WR, ratio of water transfer to water storage rate). Dimensionless relationships were further proposed to estimate PWP and root influence zone in a vegetated slope. Then analytical parametric studies were conducted to study effects of RN, CN, and WR on PWP distributions. Thereafter, the proposed relationships were validated by published field and centrifuge tests. During the drying period, the effects of root water uptake on PWP and the root influence zone become more significant as CN decreases or RN increases. During the wetting period, the larger the WR, the deeper the wetting front moves and more reduction of negative PWP occurs. The proposed dimensionless relationships can determine PWP and the root influence zone in a vegetated soil reasonably well.

Analytical solutions for calculating pore-water pressure in an infinite unsaturated slope with different root architectures

2015 ◽  
Vol 52 (12) ◽  
pp. 1981-1992 ◽  
Author(s):  
C.W.W. Ng ◽  
H.W. Liu ◽  
S. Feng
Keyword(s):  
Pore Water ◽  
Water Uptake ◽  
Analytical Solutions ◽  
Root Architecture ◽  
Pore Water Pressure ◽  
Water Pressure ◽  
Root Water Uptake ◽  
Silty Sand ◽  
Wet Season ◽  
Pressure Distributions

Vegetation can reduce pore-water pressure in soil by root water uptake. The reduction of pore-water pressure results in higher shear strength, but lower soil water permeability, affecting slope stability and rainfall infiltration, respectively. Effects of different root architectures on root water uptake and hence pore-water pressure distributions are not well understood. In this study, new analytical solutions for calculating pore-water pressure in an infinite unsaturated vegetated slope are derived for different root architectures, namely, uniform, triangular, exponential, and parabolic root architectures. Using the newly developed solutions, four series of analytical parametric analyses are carried out to improve understanding of the factors affecting root water uptake and hence influencing pore-water pressure distributions. In the dry season, different root architectures can lead to large variations in pore-water pressure distributions. It is found that the exponential root architecture induces the highest negative pore-water pressure in the soil, followed by the triangular, uniform, and parabolic root architectures. The maximum negative pore-water pressure induced by the parabolic root architecture is about 77% of that induced by the exponential root architecture in the steady state. For a given root architecture, vegetation in completely decomposed granite (CDG, classified as silty sand) induces higher negative pore-water pressure than in either fine sand or silt. The zone influenced by vegetation can be about three to six times the root depth. In the wet season, after a 10 year return period rainfall with a duration of 24 h, different root architectures show similar pore-water pressure distributions.

Evaluation of a simplified soil constitutive model considering implied strength and pore-water pressure generation for one-dimensional (1D) seismic site response

2020 ◽  
Vol 57 (7) ◽  
pp. 974-991 ◽  
Author(s):  
Xuan Mei ◽  
Scott M. Olson ◽  
Youssef M.A. Hashash
Keyword(s):  
Constitutive Model ◽  
Shear Strain ◽  
Pore Water ◽  
Pore Water Pressure ◽  
Site Response ◽  
Water Pressure ◽  
Generation Model ◽  
Cyclic Shear ◽  
Centrifuge Tests ◽  
Spectral Accelerations

Pore-water pressure (PWP) generation can lead to soil softening and liquefaction of sandy soils during earthquakes, with potential influence on site response and seismic design. The authors evaluated the generalized quadratic/hyperbolic (GQ/H) constitutive model, which captures small-strain stiffness, large-strain shear strength, and is coupled with a widely used cyclic strain–based PWP generation model (termed GQ/H+u). A suite of cyclic direct simple shear tests with a range of relative densities (∼30%–80%) and effective vertical stresses (∼25–200 kPa) and dynamic centrifuge tests with liquefiable sands were used to evaluate the ability of the GQ/H+u model to simulate cyclic soil behavior. Results indicate that GQ/H+u provides reasonable estimates of PWP increase during cyclic shear, with differences between measured and computed excess PWP ratios (ru) for both element and centrifuge tests generally smaller than 0.1. Computed spectral accelerations are comparable to centrifuge test measurements, with almost no bias at medium to long periods (T > 0.4 s) when the computed maximum shear strain (γmax) was smaller than the limit shear strain (γlimit). When computed ru > 0.8 and computed γmax > γlimit, spectral accelerations may be underestimated at both short and long periods as dilative behavior is not captured by GQ/H+u.

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.

The temperature and pore water pressure in soil subjected to dynamic load

2018 ◽  
Vol 35 (2) ◽  
pp. 111
Author(s):  
Kun ZHANG ◽  
Ze ZHANG ◽  
Xiangyang SHI ◽  
Sihai LI ◽  
Donghui XIAO
Keyword(s):  
Pore Water ◽  
Dynamic Load ◽  
Pore Water Pressure ◽  
Water Pressure

Development of Experimental P-Y Curves from Centrifuge Tests for Piles Subjected to Static Loading and Liquefaction-Induced Lateral Spreading

2020 ◽  
Vol 14 (1) ◽  
Author(s):  
Milad Souri
Keyword(s):  
Static Loading ◽  
Pore Water Pressure ◽  
Water Pressure ◽  
Pressure Ratio ◽  
Lateral Spreading ◽  
American Petroleum Institute ◽  
Unique Contribution ◽  
Pile Groups ◽  
Centrifuge Tests ◽  
Centrifuge Models

The results of five centrifuge models were used to evaluate the response of pile-supported wharves subjected to inertial and liquefaction-induced lateral spreading loads. The centrifuge models contained pile groups that were embedded in rockfill dikes over layers of loose to dense sand and were shaken by a series of ground motions. The p-y curves were back-calculated for both dynamic and static loading from centrifuge data and were compared against commonly used American Petroleum Institute p-y relationships. It was found that liquefaction in loose sand resulted in a significant reduction in ultimate soil resistance. It was also found that incorporating p-multipliers that are proportional to the pore water pressure ratio in granular materials is adequate for estimating pile demands in pseudo-static analysis. The unique contribution of this study is that the piles in these tests were subjected to combined effects of inertial loads from the superstructure and kinematic loads from liquefaction-induced lateral spreading.

Prediction of pore-water pressure response to rainfall using support vector regression

2016 ◽  
Vol 24 (7) ◽  
pp. 1821-1833 ◽  
Author(s):  
Nuraddeen Muhammad Babangida ◽  
Muhammad Raza Ul Mustafa ◽  
Khamaruzaman Wan Yusuf ◽  
Mohamed Hasnain Isa
Keyword(s):  
Support Vector Regression ◽  
Pore Water ◽  
Pore Water Pressure ◽  
Water Pressure ◽  
Pressure Response ◽  
Support Vector
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