3D Numerical Analysis of Seismic Performances of Dyke on Liquefiable Soils

2011 ◽  
Vol 243-249 ◽  
pp. 3824-3831
Author(s):  
Ming Wu Wang ◽  
Guang Yi Chen
Keyword(s):  
Pore Water Pressure ◽  
Numerical Models ◽  
Water Pressure ◽  
Silica Sand ◽  
Three Dimension ◽  
Seismic Safety ◽  
Mechanism Model ◽  
Centrifuge Tests ◽  
Field Investigations ◽  
Effective Stress Analysis

Many field investigations of earthquake disaster cases confirm that earthquake-induced liquefaction is a main factor resulting in large damages to dyke. Consequently to ensure seismic safety of dyke on the liquefiable foundation, the research on seismic performances of dyke is of great importance. Herein seismic responses of dyke on the liquefiable soils were discussed by means of three dimension effective stress analysis method using a multiple shear mechanism model and liquefaction front. Two numerical models, in which the liquefiable foundation both consisted of saturated fine silica sand of 30% relative density and scenario waves with peak amplitude of 0.8056 and 3.133 m/s2 were used input waves, were conducted to investigate the distribution principles and the changing rules of deformation, acceleration, express pore water pressure, and shear dilatancy behavior in the dyke and the liquefiable foundation. The computed results do good agreements with the measured results from centrifuge tests. And these results may be of theoretical and realistic significance for seismic design of dyke on liquefiable soils.

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.

scholarly journals Bench-Scale Experiments on Effects of Pipe Flow and Entrapped Air in Soil Layer on Hillslope Landslides

Geosciences ◽  
2019 ◽  
Vol 9 (3) ◽  
pp. 138 ◽  
Author(s):  
Yasutaka Tanaka ◽  
Taro Uchida ◽  
Hitoshi Nagai ◽  
Hikaru Todate
Keyword(s):  
Water Supply ◽  
Pore Water ◽  
Pore Water Pressure ◽  
Water Pressure ◽  
Soil Layer ◽  
Silica Sand ◽  
Bench Scale ◽  
Drainage Capacity ◽  
Entrapped Air ◽  
Model Slope

Soil pipes are commonly found in landslide scarps, and it has been suggested that build-up of pore water pressure due to clogged soil pipes influences landslide initiation. Several researchers have also suggested that entrapped air in the soil layer increases the pore water pressure. We carried out bench-scale model experiments to investigate the influence of soil pipes and entrapped air on the build-up of pore water pressure. We installed a water supply system consisting of an artificial rainfall simulator, and used a water supply tank to supply water to the model slope and artificial pipe. We used two types of artificial pipe: A straight pipe, and a confluence of three pipes. Furthermore, we placed a layer of silica sand on top of the model slope to investigate the effect of entrapped air in the soil layer on the build-up of pore water pressure. Silica sand is finer than the sand that we used for the bulk of the model slope. Our results indicate that, although artificial pipes decrease the pore water pressure when the amount of water supplied was smaller than the pipe drainage capacity, the pore water pressure increased when the water supply was too large for the artificial pipe to drain. In particular, the confluence of pipes increased the pore water pressure because the water supply exceeded the drainage capacity. The results also indicate that entrapped air increases the pore water pressure in the area with relatively low drainage capacity, too. Based on these results, we found that although soil pipes can drain a certain amount of water from a soil layer, they can also increase the pore water pressure, and destabilize slopes. Furthermore, entrapped air enhances the trend that the pore water pressure can increase in the area with relatively low drainage capacity, as pore water pressure increases when too much water is supplied, and the artificial pipe cannot drain all of it.

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.

Numerical Simulation of Storage Tank Foundation Treated by Water Filling Preloading Method

2012 ◽  
Vol 204-208 ◽  
pp. 250-254
Author(s):  
Yan Mei Zhang ◽  
Xu Dong Zhang
Keyword(s):  
Common Ground ◽  
Pore Water Pressure ◽  
Water Pressure ◽  
Treatment Method ◽  
Soil Parameters ◽  
Three Dimension ◽  
Time Curve ◽  
Constrained Modulus ◽  
Water Filling ◽  
Preloading Method

The water filling preloading method is the common ground treatment method adopted to reinforce soft tank foundation. The influence laws of load speed, soil parameters on the reinforced effect of soft tank foundation were analyzed by the three-dimension finite element numerical analysis procedure. The research shows that the fovea deformation of single tank bottom under preload is similar to the pan bottom shape; the influence of soil constrained modulus on settlement is remarkable and it also affects the settlement time curve shape; when the constrained modulus is constant, with the permeability coefficient decreasing, the surface doming phenomenon around the tank foundation increases, and the range of upheaval is related to constrained modulus; the influence of loading function on the final settlement is very small, but the influence on pore water pressure is remarkable.

scholarly journals Implications of the principle of effective stress

2020 ◽  
Author(s):  
Gerd Gudehus
Keyword(s):  
Critical Phenomena ◽  
Pore Water ◽  
Effective Stress ◽  
Critical Points ◽  
Pore Water Pressure ◽  
Numerical Models ◽  
Water Pressure ◽  
Shear Bands ◽  
Triaxial Tests ◽  
Water Saturated

AbstractWhile Terzaghi justified his principle of effective stress for water-saturated soil empirically, it can be derived by means of the neutrality of the mineral with respect to changes of the pore water pressure $$p_w$$ p w . This principle works also with dilating shear bands arising beyond critical points of saturated grain fabrics, and with patterns of shear bands as relics of critical phenomena. The shear strength of over-consolidated clay is explained without effective cohesion, which results also from swelling up to decay, while rapid shearing of water-saturated clay can lead to a cavitation of pore water. The $$p_w$$ p w -neutrality is also confirmed by triaxial tests with sandstone samples, while Biot’s relation with a reduction factor for $$p_w$$ p w is contestable. An effective stress tensor is heuristically legitimate also for soil and rock with relics of critical phenomena, particularly for critical points with a Mohr–Coulomb condition. Therein, the $$p_w$$ p w -neutrality of the solid mineral determines the interaction of solid fabric and pore water, but numerical models are questionable due to fractal features.

Slope Monitoring System at a Slope Behind an Important Cultural Asset

2011 ◽  
Vol 6 (1) ◽  
pp. 70-79 ◽  
Author(s):  
Kazunari Sako ◽  
◽  
Ryoichi Fukagawa ◽  
Tomoaki Satomi ◽  
◽  
...  
Keyword(s):  
Field Measurement ◽  
Slope Failure ◽  
Rainfall Intensity ◽  
Pore Water Pressure ◽  
Numerical Models ◽  
Water Pressure ◽  
Measurement Data ◽  
Warning System ◽  
Set Up ◽  
Relationship Of

Rainfall-induced slope failure has been responsible for great death and destruction in Japan. This is thus a primary consideration in preserving Japan’s many cultural important temples, palaces, and similar structures, especially in the ancient capital of Kyoto, where many important cultural assets are located on hillsides and near mountains. Our objective is to construct a slope-disaster warning system using real-time field measurement data, in-situ and laboratory testing, and numerical models. We set up field monitoring on a slope behind an important cultural asset in July 2004 to measure pore-water pressure, temperature, and rainfall intensity [1]. We firstly introduce our slope-disaster warning concept and field measurement results for the slope behind the important cultural asset in Kyoto. And then we discuss the relationship of rainfall intensity, seepage behavior, and slope failure based on monitoring data and model test results using a soil box apparatus.

Experimental technique for visualization of aquitard compaction over aquifer caused by excess pumping

2020 ◽  
Author(s):  
Kazunori Tabe ◽  
Masaatsu Aichi
Keyword(s):  
Pore Water ◽  
Pore Water Pressure ◽  
Water Pressure ◽  
Three Dimensional ◽  
Physical Modelling ◽  
Pumping Test ◽  
Silica Sand ◽  
Clay Layer ◽  
Synthetic Clay ◽  
Transparent Soils

<p> Transparent soils are developed as a physical modelling of macroscopic soil behaviors in geotechnical engineering aspect. Transparent surrogates with its index-matching fluid, called as transparent porous media or transparent soils, have been used for simulating geotechnical properties of natural soils. Visualization technique itself have been applied to microscopic level of soil deformation and soil flow problems such as X-ray, Computerized Tomography (CT), and Magnetic Resonance Imaging (MRI) cameras by very expensive apparatuses with highly operating skills. Geotechnical researches need rather understanding of macroscopic scale of larger test models with inexpensive experimental industrial substances. Transparent soils have been developed to achieve these needs with easy handling performance. <br> The authors demonstrated a pumping test in a glass tank of 30mm width by 80mm length by 70mm height filled with transparent hydrated superabsorbent polymer to represent aquitard (clay layer) over aquifer (saturated silica sand). The subsidence within the synthetic clay layer due to pumping of pore water from silica sand was constantly monitored by target racking method using four 8mm-diameter particles immersed in the synthetic clay layer. The test successfully visualized deformation due to vertical propagation of pore water pressure during subsidence event within the transparent synthetic clay layer. It was also found that this experiment result and the results from three-dimensional numerical simulation of poroelastic deformation were consistent with each other.</p>

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.

The theory of one-dimensional consolidation of saturated clays. II. Finite nonlinear consolidation of thick homogeneous layers

1981 ◽  
Vol 18 (2) ◽  
pp. 280-293 ◽  
Author(s):  
Robert E. Gibson ◽  
Robert L. Schiffman ◽  
Kenneth W. Cargill
Keyword(s):  
Pore Water Pressure ◽  
Water Pressure ◽  
Excess Pore Pressure ◽  
Conventional Theory ◽  
One Dimensional ◽  
Consolidation Settlement ◽  
Finite Strain Theory ◽  
Effective Stress Analysis ◽  
The One ◽  
Excess Pore

The one-dimensional consolidation of a thick clay layer, initially consolidated fully under its own weight, is considered. Account is taken of the variation of the coefficients of permeability and compressibility as consolidation proceeds. To render the theory consistent finite strains are permitted. Comparisons with conventional theory, in a practical example, show that nonlinear finite strain theory predicts the progress of consolidation settlement to be substantially swifter than indicated by conventional theory, although the dissipation of excess pore pressure may be slower. The consequences of this indicate that conventional consolidation theory has the potential to seriously underestimate the excess pore water pressure in a soft layer. As a result, the estimated shear strength would, if an effective stress analysis were used, be overestimated; a potentially unsafe design could emerge.

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