scholarly journals Tunnel Behaviour Caused by Basement Excavation in Clay

Geofluids ◽  
2021 ◽  
Vol 2021 ◽  
pp. 1-11
Author(s):  
Huasheng Sun ◽  
Jihua Zhang ◽  
Guodong Zhao ◽  
Hao Wang
Keyword(s):  
Permeability Coefficient ◽  
Pore Water Pressure ◽  
Water Pressure ◽  
Three Dimensional ◽  
Soil Permeability ◽  
Foundation Pit ◽  
Nonlinear Constitutive Model ◽  
Tunnel Diameter ◽  
Consolidation Time ◽  
Diameter Change

Many researchers have investigated the effect of basement excavation on tunnel deformation. However, the influence of consolidation on the interaction of basement-tunnel-soil is rarely considered or systematically studied in clay. In this study, three-dimensional coupled-consolidation finite element analyses were conducted to investigate the effect of consolidation on the tunnel response to excavation. An advanced nonlinear constitutive model was adopted, and numerical parametric investigations were conducted to study the effect of the excavation depth, tunnel stiffness, soil permeability coefficient, and consolidation time on the tunnel response. The results revealed that the basement excavation led to stress release, which caused tunnel heave. Owing to the dissipation of excess negative pore water pressure, the tunnel heave further increased to become approximately twice as large compared with that observed when the foundation pit excavation had just been completed. As the consolidation time increased, the longitudinal tunnel heave and tunnel diameter change caused by the foundation pit excavation gradually increased, but the growth rate was slower down. When the consolidation time changed from 50 days to 150 days, the maximum tunnel heave at the crown and the maximum tunnel diameter change increased by 1.18 and 1.48 times, respectively. The soil’s permeability coefficient did not have a significant effect on the tunnel heave at the crown nor on the tunnel diameter change. The results obtained by this study are expected to be useful as an engineering reference for the analysis of soil structure problems in clay.

Numerical Simulation of Post-Construction Deformation Characteristics of Storage Oil Tank Ground

2013 ◽  
Vol 353-356 ◽  
pp. 593-596 ◽  
Author(s):  
Yan Mei Zhang ◽  
Xu Dong Zhang
Keyword(s):  
Permeability Coefficient ◽  
Pore Water Pressure ◽  
Ground Deformation ◽  
Water Pressure ◽  
Three Dimensional ◽  
Element Model ◽  
Additional Stress ◽  
Soil Parameters ◽  
Ground Settlement ◽  
Constrained Modulus

Ground soil was looked as porous medium, a three-dimensional finite element model of shell-liquid-foundation-ground was built, and the influence of soil parameters, filling liquid mode, and liquid height on the tank ground deformation was discussed. The research shows that the subsidence range caused by additional stress is the 0.3D range of the tank bottom edge outer; the influence of soil constrained modulus on settlement is remarkable, with constrained modulus decreasing, the tank ground settlement increases; with soil permeability coefficient decreasing, the tank ground settlement decreases; the ground settlement curve shape is decided by soil constrained modulus and permeability coefficient; the influence of filling liquid mode on the ground final settlement is very small ,but on the pore water pressure peak is remarkable.

Influence Analysis of Pit Foundation Precipitation to Adjoining Raft Foundation

2011 ◽  
Vol 261-263 ◽  
pp. 1206-1209
Author(s):  
Zong Jun Sun ◽  
Xiao Bin Liu ◽  
Yan Kai Wu ◽  
Qian Chao Luan
Keyword(s):  
Pore Water Pressure ◽  
Water Pressure ◽  
Three Dimensional ◽  
Foundation Settlement ◽  
Soil Deformation ◽  
Foundation Pit ◽  
Maximum Value ◽  
Raft Foundation ◽  
Building Foundation ◽  
Analysis Mode

Pit foundation excavation leads both settlement and uneven settlement in the building foundation. It has settlement cracks in masonry and concrete structure; these damages lie on the basis of the instability in neighboring buildings. In this paper, by the use of FLAC3D, it establish three-dimensional numerical analysis mode of interaction between foundation pit excavation and raft foundation, the change patterns of the soil deformation, pore water pressure and the uneven settlements of raft foundation are analyzed. The results indicate that the maximum value of the raft foundation settlement appears on the maximum pit free surface on the foundation pit, and the lesser value of the raft foundation settlement is away from the foundation pit, these indicate that the laws of the uneven settlement.

scholarly journals The Hydromechanical Interplay in the Simplified Three-Dimensional Limit Equilibrium Analyses of Unsaturated Slope Stability

Geosciences ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 73
Author(s):  
Panagiotis Sitarenios ◽  
Francesca Casini
Keyword(s):  
Analytical Solution ◽  
Slope Stability ◽  
Slope Failure ◽  
Failure Modes ◽  
Pore Water Pressure ◽  
Limit Equilibrium ◽  
Water Pressure ◽  
Three Dimensional ◽  
Stability Limit ◽  
Smooth Transition

This paper presents a three-dimensional slope stability limit equilibrium solution for translational planar failure modes. The proposed solution uses Bishop’s average skeleton stress combined with the Mohr–Coulomb failure criterion to describe soil strength evolution under unsaturated conditions while its formulation ensures a natural and smooth transition from the unsaturated to the saturated regime and vice versa. The proposed analytical solution is evaluated by comparing its predictions with the results of the Ruedlingen slope failure experiment. The comparison suggests that, despite its relative simplicity, the analytical solution can capture the experimentally observed behaviour well and highlights the importance of considering lateral resistance together with a realistic interplay between mechanical parameters (cohesion) and hydraulic (pore water pressure) conditions.

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

Analyses of groundwater flow and plant evapotranspiration in a vegetated soil slope

2013 ◽  
Vol 50 (12) ◽  
pp. 1204-1218 ◽  
Author(s):  
A.K. Leung ◽  
C.W.W. Ng
Keyword(s):  
Groundwater Flow ◽  
Pore Water Pressure ◽  
Water Pressure ◽  
Three Dimensional ◽  
Root Water Uptake ◽  
Dry Season ◽  
Climatic Data ◽  
Wet Season ◽  
Soil Slopes ◽  
Transient Seepage

Understanding seasonal hydrogeological responses of vegetated soil slopes is vital to slope stability because pore-water pressure (PWP) varies from positive values upon rainfall in wet seasons to negative values upon plant evapotranspiration (ET) in dry seasons. There are, however, few case histories that report seasonal performance of vegetated soil slopes. In this study, a vegetated slope situated in Hong Kong was instrumented to analyse (i) groundwater flow during rainfall in the wet season and (ii) effects of plant ET on PWP in the dry season. Two- and three-dimensional anisotropic transient seepage analyses are conducted to identify groundwater flow mechanism(s) during a heavy rainstorm. Through water and energy balance calculations, measured plant-induced suction is interpreted with plant characteristic and climatic data. During the rainstorm, substantial recharge of the groundwater table was recorded, likely due to preferential water flow along relict joints and three-dimensional cross-slope groundwater flow. During the dry season, the peak suction induced by plant ET is up to 200 kPa and the depth of influence is shallower than 200% of the root depth. For the range of suctions monitored, root-water uptake is revealed to have been restricted by suction not very significantly and was driven mainly by the climatic variation.

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

2018 ◽  
Vol 2018 ◽  
pp. 1-11 ◽  
Author(s):  
Ling Zeng ◽  
Jie Liu ◽  
Jun-hui Zhang ◽  
Han-bing Bian ◽  
Wei-hua Lu
Keyword(s):  
Pore Water ◽  
Permeability Coefficient ◽  
Pore Water Pressure ◽  
Water Pressure ◽  
Positive Pressure ◽  
Saturated Zone ◽  
Infiltration Depth ◽  
Infiltration Process ◽  
Fracture Angle ◽  
Rainwater Infiltration

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.

scholarly journals Stability Improvement Method for Embankment Dam with Respect to Conduit Cracks

2022 ◽  
Vol 12 (2) ◽  
pp. 567
Author(s):  
Young-Hak Lee ◽  
Jung-Hyun Ryu ◽  
Joon Heo ◽  
Jae-Woong Shim ◽  
Dal-Won Lee
Keyword(s):  
Large Scale ◽  
Pore Water Pressure ◽  
Water Pressure ◽  
Three Dimensional ◽  
Internal Erosion ◽  
Scale Model ◽  
Seepage Analysis ◽  
Large Scale Model ◽  
Proposed Model ◽  
Improvement Method

In recent years, as the number of reservoir embankments constructed has increased, embankment failures due to cracks in aging conduits have also increased. In this study, a crack in a conduit was modeled based on the current conduit design model, and the risk of internal erosion was analyzed using a large-scale model test and three-dimensional deformation–seepage analysis. The results show that when cracks existed in the conduit, soil erosion and cavitation occurred near the crack area, which made the conduit extremely vulnerable to internal erosion. Herein, a model is proposed that can reduce internal erosion by applying a layer of sand and geotextiles on the upper part of the conduit located close to the downstream slope. In the proposed model, only partial erosion occurred inside the conduit, and no cavitation appeared near the crack in the conduit. The results suggest that internal erosion can be suppressed when the water pressure acting intensively on the crack in the conduit is dispersed by the drainage layer. To validate these results, the pore water pressure, seepage line, and hydraulic gradient were investigated to confirm the erosion phenomenon and reinforcement effect.

scholarly journals Effect of Reduced Zone on Time-Dependent Analysis of Tunnels

2011 ◽  
Vol 2011 ◽  
pp. 1-12
Author(s):  
Mohammed Y. Fattah ◽  
Kais T. Shlash ◽  
Nahla M. Salim
Keyword(s):  
Finite Element ◽  
Pore Water ◽  
Pore Water Pressure ◽  
Water Pressure ◽  
Outer Diameter ◽  
Transient Effects ◽  
Excess Pore Water Pressure ◽  
Modified Cam Clay ◽  
Tunnel Diameter ◽  
Excess Pore

The problem of the proposed “Baghdad metro line” which consists of two routes of 32 km long and 36 stations is analyzed. The tunnel is circular in cross-section with a 5.9 m outer diameter. The finite element analyses were carried out using elastic-plastic and modified Cam clay models for the soil. The excavation has been used together with transient effects through a fully coupled Biot formulation. All these models and the excavation technique together with Biot consolidation are implemented into finite-element computer program named “Modf-CRISP” developed for the purpose of these analyses. The results indicate that there is an inward movement at the crown and this movement is restricted to four and half tunnel diameters. A limited movement can be noticed at spring line which reaches 0.05% of tunnel diameter, while there is a heave at the region below the invert, which reaches its maximum value of about 0.14% of the diameter and is also restricted to a region extending to 1.5 diameters. The effect of using reduced zone on excess pore water pressure and surface settlement (vertical and horizontal) was also considered and it was found that the excess pore water pressure increases while the settlement trough becomes deeper and narrower using reduced .

scholarly journals Experimental Study on the Variation Law of Excess Pore Water Pressure at the Bottom of the Foundation Pit for Excavation

2020 ◽  
Vol 2020 ◽  
pp. 1-11
Author(s):  
Qizhi Hu ◽  
Qiang Zou ◽  
Zhigang Ding ◽  
Zhaodong Xu
Keyword(s):  
Pore Water ◽  
Pore Water Pressure ◽  
Water Pressure ◽  
Soft Soil ◽  
Confining Pressure ◽  
Deep Foundation ◽  
Foundation Pit ◽  
Excess Pore Water Pressure ◽  
Accurate Expression ◽  
Excess Pore

The excavation unloading of deep foundation pits in soft soil areas often produces negative excess pore water pressure. The rebound deformation of soil on the excavation surface of the foundation pit can be predicted reliably through the accurate expression of relevant variation laws. In combination with the principle of effective stress and the general equation of unidirectional seepage consolidation, an equation for calculating the rebound deformation from the bottom in the process of foundation pit excavation unloading was obtained. Additionally, a triaxial unloading test was adopted to simulate the excavation unloading processes for actual foundation pit engineering. After studying the variation law of the excess pore water pressure generated by excavation unloading, it was found that the negative excess pore water pressure increased with increasing unloading rate, while the corresponding peak value decreased with increasing confining pressure. The equation for rebound calculation was verified through a comparison with relevant measured data from actual engineering. Therefore, it is considered that the equation can reliably describe the rebound deformation law of the base. This paper aims to guide the design and construction of deep foundation pits in soft soil areas.

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.

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