scholarly journals Numerical Evaluation of The Nonlinear Behavior of Soil-Pile Interaction Under The Effect of Coupled Static-Dynamic Loads

2021 ◽  
Author(s):  
Duaa Al-Jeznawi ◽  
ISMACAHYADI Mohamed Jais ◽  
Bushra S. Albusoda
Keyword(s):  
Pore Water ◽  
Pore Water Pressure ◽  
Water Pressure ◽  
Three Dimensional ◽  
Ground Surface ◽  
Frictional Resistance ◽  
Saturated Soil ◽  
Shaking Table ◽  
Physical Models ◽  
Soil Layers

Abstract Liquefaction of saturated soil layers is one of the most common causes of structural failure during earthquakes. Liquefaction occurs as a result of increasing pore water pressure, whereby the rise in water pressure occurs due to unexpected change in stress state under short-term loading, i.e., shaking during an earthquake. Thus, general failure occurs when the soil softens and eliminates its stiffness against the uplift pressure from the stability of the subsurface structure. In this case, the condition of soil strata is considered undrained because there is not enough time for the excess pore water pressure to dissipate when a sudden load is applied. To represent the non-linear characteristics of saturated sand under seismic motions in Kobe and Ali Algharbi earthquakes, the computational model was simulated using the UBCSAND model. The current study was carried out by adopting three-dimensional-based finite element models that were evaluated by shaking table tests of a single pile model erected in the saturated soil layers. The experimental data were utilized to estimate the liquefaction and seismicity of soil deposits. According to the results obtained from the physical models and simulations, this proposed model accurately simulates the liquefaction phenomenon and soil-pile response. However, there are some differences between the experiment and the computational analyses. Nonetheless, the results showed good agreement with the general trend in terms of deformation, acceleration, and liquefaction ratio. Moreover, the displacement of liquefied soil around the pile was captured by the directions of vectors generated by numerical analysis, which resembled a worldwide circular flow pattern. The results revealed that during the dynamic excitation, increased pore water pressure and subsequent liquefaction caused a significant reduction in pile frictional resistance. Despite this, positive frictional resistance was noticed through the loose sand layer (near the ground surface) until the soil softened completely. It is worth mentioning that the pile exhibited excessive settlement which may attribute to the considerable reduction, in the end, bearing forces which in turn mobilizing extra end resistance.

Three-dimensional numerical investigations of groundwater responses in an unsaturated slope subjected to various rainfall patterns

2001 ◽  
Vol 38 (5) ◽  
pp. 1049-1062 ◽  
Author(s):  
C WW Ng ◽  
B Wang ◽  
Y K Tung
Keyword(s):  
Pore Water ◽  
Short Duration ◽  
Pore Water Pressure ◽  
Water Pressure ◽  
Three Dimensional ◽  
Ground Surface ◽  
Rainfall Pattern ◽  
Initial Water ◽  
Pore Water Pressures ◽  
Rainfall Patterns

Three-dimensional (3D) numerical analyses were conducted to investigate groundwater responses in an initially unsaturated cut slope at Lai Ping Road in Hong Kong subjected to rainfalls with various patterns, durations, and return periods. Initial and boundary conditions were established from field monitoring data. The computed results show that rainfall pattern has a significant influence on pore-water pressures in soil layers near the ground surface but its influence gradually diminishes with depth. Rainfall with an advanced storm pattern of 24 h duration was found to be the most critical because it results in the highest pore-water pressure in the slope. At a given depth, the influence of rainfall pattern on pore-water pressures depends on the initial groundwater conditions: the higher the initial water table, the smaller the influence of rainfall pattern on pore-water pressures. Under a given rainfall duration, the rise of pore-water pressure at the study site is significant only when the return period increases from 10 years to 100 years, but not from 100 years to 1000 years. Short-duration, intense rainfall causes larger variations in pore-water pressure at shallow depths, whereas long-duration rainfall has a greater influence on groundwater in deep soils because of the generally greater amount of rainfall. For prolonged rainfalls, the difference in pore-water pressure distribution resulting from different rainfall patterns is less significant than that from short-duration, intense rainfalls.Key words: Lai Ping Road, rainfall patterns, pore-water pressure distributions, suction, unsaturated slope.

Three‐Dimensional Numerical Investigation of Pore Water Pressure and Deformation of Pumped Aquifer Systems

Ground Water ◽  
2019 ◽  
Vol 58 (2) ◽  
pp. 278-290 ◽  
Author(s):  
Yun Zhang ◽  
Xuexin Yan ◽  
Tianliang Yang ◽  
Jichun Wu ◽  
Jianzhong Wu
Keyword(s):  
Numerical Investigation ◽  
Pore Water ◽  
Pore Water Pressure ◽  
Water Pressure ◽  
Three Dimensional ◽  
Aquifer Systems

scholarly journals Effect of Seismic Loading on Variation of Pore Water Pressure During Pile Pull-Out Tests in Sandy Soils

2021 ◽  
Vol 27 (12) ◽  
pp. 1-12
Author(s):  
Haider N. Abdul Hussein ◽  
Qassun S. Mohammed Shafiqu ◽  
Zeyad S. M. Khaled
Keyword(s):  
Pore Water ◽  
Pore Water Pressure ◽  
Water Pressure ◽  
Seismic Loading ◽  
Shaking Table ◽  
Dense Sand ◽  
Pressure Transducers ◽  
Pull Out ◽  
Pullout Tests ◽  
Pile Model

Experimental model was done for pile model of L / D = 25 installed into a laminar shear box contains different saturation soil densities (loose and dense sand) to evaluate the variation of pore water pressure before and after apply seismic loading. Two pore water pressure transducers placed at position near the middle and bottom of pile model to evaluate the pore water pressure during pullout tests. Seismic loading applied by uniaxial shaking table device, while the pullout tests were conducted through pullout device. The results of changing pore water pressure showed that the variation of pore water pressure near the bottom of pile is more than variation near the middle of pile in all tests. The variation of pore water pressure after apply seismic loading is more than the variation before apply seismic loading near the middle of pile and near the bottom of pile and in loose and dense sand. Variation of pore water pressure after apply seismic loading and uplift force is less than the variation after apply seismic loading in loose sand at middle and bottom of pile.

Downslope movements at shallow depths related to cyclic pore-pressure changes

1993 ◽  
Vol 30 (3) ◽  
pp. 464-475 ◽  
Author(s):  
K.D. Eigenbrod
Keyword(s):  
Pore Water ◽  
Slip Surface ◽  
Pore Water Pressure ◽  
Limit Equilibrium ◽  
Water Pressure ◽  
Ground Surface ◽  
Soil Mass ◽  
Passive Resistance ◽  
Pressure Changes ◽  
Timber Piles

Slow, shallow ground movements in a slope near Yellowknife caused excessive tilting of timber piles that supported an engineering structure. To avoid damage to the structure, the pile foundations had to be replaced by rigid concrete piers that were designed to resist the forces of the moving soil mass. Downhill movements were rather slow and, during an initial inspection, were indicated only by soil that was pushed up against a series of piles on their uphill sides, while gaps had formed on their downhill sides. No open cracks or bulging was observed on the slope. A stability analysis indicated that the slope was not in a state of limit equilibrium. To obtain a better understanding of the creep movements in the slope and their effect on the rigid concrete piers, extensive instrumentation was carried out after the construction of the piers. This included slope indicators, piezometers, thermistors, and total-pressure cells against one of the concrete piers. In addition, a triaxial testing program was undertaken in which the effect of cyclic pore-water pressure changes on the long-term deformations of the shallow clay layer was investigated. From the data collected in the field and laboratory, it could be concluded that (i) tilting of the original timber piles was caused by downslope movements related to cyclic pore-water increases; (ii) the lateral soil movements increased almost linearly with depth from 2 m below the ground surface, with no indication of a slip surface; and (iii) the pressures exerted by the moving soil mass against the rigid concrete piers within the soil mass were equal to the passive resistance activated within the moving soil mass. Key words : soil creep, slope movements, soil pressures, pore-water pressures, freezing pressures, permafrost, cyclic loading.

scholarly journals Numerical Study on Effects of the Embedded Monopile Foundation on Local Wave-Induced Porous Seabed Response

2015 ◽  
Vol 2015 ◽  
pp. 1-13 ◽  
Author(s):  
Chi Zhang ◽  
Qingyang Zhang ◽  
Zaitian Wu ◽  
Jisheng Zhang ◽  
Titi Sui ◽  
...  
Keyword(s):  
Pore Water ◽  
Pore Water Pressure ◽  
Numerical Study ◽  
Water Pressure ◽  
Three Dimensional ◽  
Navier Stokes ◽  
Stokes Wave ◽  
Local Concentration ◽  
Soil Stress ◽  
Local Wave

Effects of the embedded monopile foundation on the local distributions of pore water pressure, soil stresses, and liquefaction are investigated in this study using a three-dimensional integrated numerical model. The model is based on a Reynolds-Averaged Navier-Stokes wave module and a fully dynamic poroelastic seabed module and has been validated with the analytical solution and experimental data. Results show that, compared to the situation without an embedded foundation, the embedded monopile foundation increases and decreases the maximum pore water pressure in the seabed around and below the foundation, respectively. The embedded monopile foundation also significantly modifies the distributions of the maximum effective soil stress around the foundation and causes a local concentration of soil stress below the two lower corners of foundation. A parametric study reveals that the effects of embedded monopile foundation on pore water pressure increase as the degrees of saturation and soil permeability decrease. The embedded monopile foundation tends to decrease the liquefaction depth around the structure, and this effect is relatively more obvious for greater degrees of saturation, greater soil permeabilities, and smaller wave heights.

Second Canadian Geotechnical Colloquium: Appropriate concepts and technology for unsaturated soils

1979 ◽  
Vol 16 (1) ◽  
pp. 121-139 ◽  
Author(s):  
D. G. Fredlund
Keyword(s):  
Unsaturated Soil ◽  
Unsaturated Soils ◽  
Pore Water Pressure ◽  
Water Pressure ◽  
Three Dimensional ◽  
Earth Pressure ◽  
Saturated Soil ◽  
Engineering Practice ◽  
The Matrix ◽  
Matrix Suction

A practical science has not been fully developed for unsaturated soils for two main reasons. First, there has been the lack of an appropriate science with a theoretical base. Second, there has been the lack of an appropriate technology to render engineering practice financially viable.This paper presents concepts that can be used to develop an appropriate engineering practice for unsaturated soils. The nature of an unsaturated soil is first described along with the accompanying stress conditions. The basic equations related to mechanical properties are then proposed. These are applied to practical problems such as earth pressure, limiting equilibrium, and volume change.An attempt is made to demonstrate the manner in which saturated soil mechanics must be extended when a soil is unsaturated. Two variables are required to describe the stress state of an unsaturated soil (e.g., (σ – ua) and (ua – uW). There is a smooth transition from the unsaturated case to the saturated case since the pore-air pressure becomes equal to the pore-water pressure as the degree of saturation approaches 100%. Therefore, the matrix suction (i.e., (ua – uW) goes to 0 and the pore-water pressure can be substituted for the pore-air pressure (i.e., (σ – uW)).The complete volumetric deformation of an unsaturated soil requires two three-dimensional constitutive surfaces. These converge to one two-dimensional relationship for a saturated soil. The shear strength for an unsaturated soil is a three-dimensional surface that reduces to the conventional Mohr–Coulomb envelope for a saturated soil.The manner of applying the volumetric deformation equations and the shear strength equation to practical problems is demonstrated. For earth pressure and limiting equilibrium problems, the unsaturated soil can be viewed as a saturated soil with an increased cohesion. The increase in cohesion is proportional to the matrix suction of the soil. For volume change problems it is necessary to have an indication of the relationship between the various soil moduli.There is a need for further experimental studies and case histories to substantiate the proposed concepts and theories.

scholarly journals The Evolution of Pore Water Pressure in a Saturated Soil Layer between Two Draining Zones by Analytical and Numerical Methods

2015 ◽  
Vol 05 (04) ◽  
pp. 390-398
Author(s):  
Abib Tall ◽  
Cheikh Mbow ◽  
Daouda Sangaré ◽  
Mapathé Ndiaye ◽  
Papa Sanou Faye
Keyword(s):  
Numerical Methods ◽  
Pore Water ◽  
Pore Water Pressure ◽  
Water Pressure ◽  
Soil Layer ◽  
Saturated Soil

scholarly journals An Analytical Continuous Upper Bound Limit Analysis of Pore Water Effect on the Tail Stability of Underwater Shield Tunnels during Construction

2020 ◽  
Vol 143 ◽  
pp. 01015
Author(s):  
Wenjie Song ◽  
Yanyong Xiang
Keyword(s):  
Pore Water ◽  
Upper Bound ◽  
Limit Analysis ◽  
Pore Water Pressure ◽  
Water Pressure ◽  
Ground Surface ◽  
Support Pressure ◽  
Tunnel Support ◽  
Transverse Stability ◽  
Upper Bound Limit Analysis

An analytical continuous upper bound limit analysis is developed to analyse the effects of seepage on the transverse stability of underwater shield tunnels. The approach is based on an analytical continuous upper bound limit analysis method for cohesive-frictional soils. It employs the complex variables solution of the displacement field due to tunnel deformation and movement, and the analytical solution of the pore water pressure field for steady state seepage due to pore water influx at the tunnel perimeter. The most critical slip line position and the minimum required tunnel support pressure are determined by using a particle swarm optimization scheme for various generic situations. The method is verified via finite element simulation and comparison with the solution from using rigid block upper bound limit analysis. The parametric analysis revealed among other things that both the infimum of the necessary tunnel support pressure and the most critical plastic zone increase when the hydraulic head at the ground surface increases, but decrease when the tunnel influx increases due to the fact that pore water pressure at the tunnel perimeter decreases with the tunnel influx.

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