scholarly journals Research on Ground Liquefaction and Structural Force Characteristics of Underground Utility Tunnels Under CLC Stratigraphic Model

2021 ◽  
Author(s):  
Tian Tian ◽  
aijun Yao ◽  
Yifei Gong ◽  
Yaozhen Guo
Keyword(s):  
Pore Water Pressure ◽  
Numerical Study ◽  
Water Pressure ◽  
Volumetric Strain ◽  
Sine Wave ◽  
Burial Depth ◽  
Underground Structures ◽  
Underground Engineering ◽  
Stratigraphic Model ◽  
Structure Height

Abstract Damages to underground structures due to liquefaction of the soils caused by cyclic loads such as earthquakes have always been an important issue in geotechnical underground engineering practices. This paper presents a numerical study of the utility tunnels at different burial depths in "Coh-Liq-Coh" horizontally layered liquefiable grounds using the finite-difference program FLAC3D. "Finn-Byrne" cyclic load volumetric strain increment model simulates the fluid-solid coupling of saturated sand and the increase in pore water pressure during vibration. The numerical model was loaded using an acceleration sine wave for dynamic calculations. The numerical results showed that the burial depths have a strong influence on the liquefaction of the soil beneath the utility tunnels and on the forces and deformations of the structures. Under the numerical simulation conditions in this paper, the greater the burial depth, the greater the liquefaction of the soil beneath the structure, the greater the shear stress on the side walls and the smaller the settlement difference between the structure and the surrounding soil. In the numerical simulations in this paper, a reasonable burial depth for utility tunnels was 0.8 to 1.1 times of the structure height.

scholarly journals Field Test of Excess Pore Water Pressure at Pile–Soil Interface Caused by PHC Pipe Pile Penetration Based on Silicon Piezoresistive Sensor

Sensors ◽  
2020 ◽  
Vol 20 (10) ◽  
pp. 2829
Author(s):  
Yonghong Wang ◽  
Xueying Liu ◽  
Mingyi Zhang ◽  
Suchun Yang ◽  
Songkui Sang
Keyword(s):  
Pore Water ◽  
Pore Water Pressure ◽  
Water Pressure ◽  
Field Tests ◽  
Burial Depth ◽  
Excess Pore Water Pressure ◽  
Pipe Pile ◽  
Test Pile ◽  
Soil Interface ◽  
Excess Pore

Prestressed high-strength concrete (PHC) pipe pile with the static press-in method has been widely used in recent years. The generation and dissipation of excess pore water pressure at the pile–soil interface during pile jacking have an important influence on the pile’s mechanical characteristics and bearing capacity. In addition, this can cause uncontrolled concrete damage. Monitoring the change in excess pore water pressure at the pile–soil interface during pile jacking is a plan that many researchers hope to implement. In this paper, field tests of two full-footjacked piles were carried out in a viscous soil foundation, the laws of generation and dissipation of excess pore water pressure at the pile–soil interface during pile jacking were monitored in real time, and the laws of variation in excess pore water pressure at the pile–soil interface with the burial depth and time were analyzed. As can be seen from the test results, the excess pore water pressure at the pile–soil interface increased to the peak and then began to decline, but the excess pore water pressure after the decline was still relatively large. Test pile S1 decreased from 201.4 to 86.3 kPa, while test pile S2 decreased from 374.1 to 114.3 kPa after pile jacking. The excess pore water pressure at the pile–soil interface rose first at the initial stage of consolidation and dissipated only after the hydraulic gradient between the pile–soil interface and the soil surrounding the pile disappeared. The dissipation degree of excess pore water pressure reached about 75–85%. The excess pore water pressure at the pile–soil interface increased with the increase in buried depth and finally tended to stabilize.

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.

ANISOTROPIC CONSOLIDATION OF LEDA CLAY

1969 ◽  
Vol 6 (3) ◽  
pp. 271-286 ◽  
Author(s):  
L. K. Walker ◽  
G. P. Raymond
Keyword(s):  
Stress Ratio ◽  
Pore Water Pressure ◽  
Water Pressure ◽  
Volumetric Strain ◽  
Soil Mass ◽  
Plastic Strain Increment ◽  
Anisotropic Consolidation ◽  
Leda Clay ◽  
Stress Ratios ◽  
Effective Principal

Under field loading conditions, the consolidation of a clay layer is likely to take place under effective principal stress ratios (σ1′/σ3′), which vary from point to point throughout the soil mass. From a consideration of idealized stress paths, an estimate is made of the effect of stress ratio on rates of volumetric strain and excess pore water pressure dissipation. These predictions are partly supported by data obtained from anisotropic consolidation tests on Leda clay, the major disagreements being due to the significant influence of structural cementation on the rate process.The experimentally observed rates of shear strain have been analyzed in terms of stress-dilatancy concepts. The plastic strain-increment ratio was shown to be a unique function of effective stress ratio, thus confirming the validity of previous work on remoulded clays. A theoretical prediction of this relationship postulated by Burland (1965) did not approximate to the experimental data, due probably to the influence of secondary deformations. The data did, however, show a relationship similar in form to that derived by Walker (1969) for the secondary deformation of remoulded kaolin.

scholarly journals FEM Optimisation of Seepage Control System Used for Base Stability of Excavation

2020 ◽  
Vol 6 (9) ◽  
pp. 1739-1751
Author(s):  
Ilyes Ouzaid ◽  
Naïma Benmebarek ◽  
Sadok Benmebarek
Keyword(s):  
Failure Mechanism ◽  
Pore Water Pressure ◽  
Numerical Study ◽  
Water Pressure ◽  
Drainage System ◽  
Fem Analysis ◽  
Critical Distance ◽  
Base Surface ◽  
Ruhr Area ◽  
Base Stability

With the existence of a high groundwater level, the head difference between the inside and outside of an excavation may lead to the loss of stability of the excavation’s surface. Hence, a fundamental understanding of this occurrence is important for the design and construction of water-retaining structures. In some cases, the failure mechanism cannot be predicted exactly because of its mechanical complexity as well as a major lack of protection systems and not adopting effective countermeasures against this phenomenon. The article took a tranche from an 80 km long open sewer located in the Ruhr area, Germany as an example to establish a hydro-geological model and analyse the instability of the excavation base surface caused by the groundwater flow at 45m deep and to present the effectivity of an adopted drainage system inside the excavation pit as 39 columns of sand to relax the pore water pressure. By using the Finite Element Method (FEM) analysis, the failure mechanism was investigated before applying any countermeasures, and the total length of the adopted countermeasure system was minimised. Also, various position tests were performed on the adopted drainage system to confirm the optimised position. The results of this numerical study allowed the deduction of the importance of the used drainage system by achieving 44% more in the excavating process. After achieving the required excavation depth, a further increase of the sand columns’ penetration may be considered non-economic because, after adding extra depth, all the situations have the same safety factor. In addition, this can provide a reference for the optimised position of the sand columns where they must be applied right by the wall and limited by a critical distance, D/2, half of the embedded depth of the wall.

scholarly journals Experimental and numerical study of upstream slope stability in an earth dam reservoir under rapid drawdown conditions

2020 ◽  
Vol 8 (1) ◽  
pp. 1-15
Author(s):  
Seyed Habib Mousavi Jahromi ◽  
Mansour Pakmanesh ◽  
Amir Khosrojerdi ◽  
Hossein Hassanpour Darvishi ◽  
Hossein Babazadeh
Keyword(s):  
Water Level ◽  
Pore Water Pressure ◽  
Numerical Study ◽  
Water Pressure ◽  
Earth Dam ◽  
Dam Reservoir ◽  
Reservoir Water ◽  
Reservoir Water Level ◽  
Seepage Analysis ◽  
Upstream Slope

The rapid ‎drawdown of the dam reservoir is one of the most common situations occurring in the lifetime of a dam. For this reason, one of the main factors in the design of the upstream slope is the rapid drainage of the reservoir. In this case, the upstream slope is in a critical condition and the slope may be unstable. When the water surface in the reservoir is drawdown suddenly, the water level in the dam body does not decrease at the same time as the reservoir water level. The analysis of seepage from the earth dam body and calculation of the water loss play an important role in calculating the amount of pore water pressure, and, consequently, the stability analysis of the dam body. In addition, any seepage analysis is dependent on the hydraulic properties of the dam materials. In order to investigate the effect of hydraulic conductivity on the rapid drawdown of water level and the seepage, an experimental model was constructed of an earth dam. By accurate measurement of hydraulic parameters of the materials in saturated and unsaturated media, the flow through this model was modeled using a disk penetrometer by seep/w software. The results were then compared with the observed data.

Numerical study of the effect of soil–atmosphere interaction on the stability and serviceability of cut slopes in London clay

2017 ◽  
Vol 54 (3) ◽  
pp. 405-418 ◽  
Author(s):  
A. Tsiampousi ◽  
L. Zdravkovic ◽  
D.M. Potts
Keyword(s):  
Pore Water Pressure ◽  
Numerical Study ◽  
Water Pressure ◽  
Soil Atmosphere ◽  
Highly Nonlinear ◽  
Atmosphere Interaction ◽  
London Clay ◽  
The Stability ◽  
Cut Slopes ◽  
Whole Life Cycle

The stability of cut slopes is greatly influenced by seasonal pore-water pressure variations under the combined effect of rainfall and vegetation. However, predicting soil–atmosphere interaction is not straightforward, due to the complexity of both the boundary conditions involved and the hydromechanical behaviour of soils, which is coupled and highly nonlinear, rendering the use of numerical tools, such as finite element analysis, necessary. This paper discusses the numerical modelling of soil–atmosphere interaction and presents the analysis of a slope cut in London clay in a highly vegetated area. The whole life cycle of the slope is considered with phases of low and high water demand vegetation and vegetation clearance. The analysis results indicate that dense vegetation is associated with high factors of safety, but may induce large differential displacements, which are likely to affect the serviceability of the slope. Vegetation clearance, however, may initiate instability, highlighting the need for effective vegetation management to achieve a balance between serviceability and ultimate limit states. Although the case considered is representative of southeast England, it introduces the necessary tools for realistic numerical analysis of soil–atmosphere interaction.

Numerical Study of Unsaturated Expansive Soil Canal Slope Covered by Geo-Membrane

2015 ◽  
Vol 744-746 ◽  
pp. 551-554
Author(s):  
Wen Qing Wu ◽  
Jiang Hu Chen ◽  
Hong Yu Zhang ◽  
Jun Hua Wu
Keyword(s):  
Water Content ◽  
Water Level ◽  
Soil Water ◽  
Soil Water Content ◽  
Pore Water Pressure ◽  
Numerical Study ◽  
Water Pressure ◽  
Expansive Soil ◽  
Seepage Field ◽  
Unsaturated Expansive Soil

In view of the holes appearing in different areas of geo-membrane when the geo-membrane technology is applied to the unsaturated expansive soil canal slope, the VADOSE/W is used to analyze the pore-water pressure of the internal canal slope by changing the falling water level. The results show that the hole is nearer to the toe of slope, its effect on the whole seepage field is greater. The greater the rate is, the soil water content is greater.

On the “elastic” stiffness in a high-cycle accumulation model for sand: a comparison of drained and undrained cyclic triaxial tests

2010 ◽  
Vol 47 (7) ◽  
pp. 791-805 ◽  
Author(s):  
Torsten Wichtmann ◽  
Andrzej Niemunis ◽  
Theodor Triantafyllidis
Keyword(s):  
Bulk Modulus ◽  
Pore Water Pressure ◽  
Water Pressure ◽  
Volumetric Strain ◽  
Elastic Stiffness ◽  
Plastic Strain Rate ◽  
Triaxial Tests ◽  
Strain Accumulation ◽  
Cyclic Triaxial ◽  
Cyclic Triaxial Tests

High-cycle accumulation (HCA) models may be used for the prediction of settlements or stress relaxation in soils due to a large number of cycles (N > 103) with a relatively small-strain amplitude (εampl < 10−3). This paper presents a discussion of the elastic stiffness, [Formula: see text], used in the basic constitutive equation of an HCA model, [Formula: see text], where [Formula: see text] is the trend of effective stress, [Formula: see text] is the trend of strain, [Formula: see text] is the rate of strain accumulation, and [Formula: see text] is the plastic strain rate. [Formula: see text] interrelates the “trends” of stress and strain evolution. For the experimental assessment of the bulk modulus, [Formula: see text], the rate of pore-water pressure accumulation, [Formula: see text], in undrained cyclic triaxial tests and the rate of volumetric strain accumulation, [Formula: see text], in drained cyclic tests have been compared. The pressure-dependent bulk modulus, K, was quantified from 15 pairs of drained and undrained tests with different consolidation pressures and stress amplitudes. It is demonstrated that both the curves [Formula: see text] in the drained tests and u(N) in the undrained tests are well predicted by the authors’ HCA model if the elastic stiffness is determined using the method described in the present paper. A simplified determination of K from the unloading and reloading curve in an oedometric compression test is discussed.

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