scholarly journals Numerical study on stress paths in grounds reinforced with long and short CFG piles during adjacent rigid retaining wall movement

2022 ◽  
Vol 0 (0) ◽  
Author(s):  
Bantayehu Uba Uge ◽  
Yuancheng Guo ◽  
Yunlong Liu
Keyword(s):  
Principal Stress ◽  
Numerical Study ◽  
Retaining Wall ◽  
Stress Path ◽  
Composite Foundation ◽  
Practical Implementation ◽  
Foundation Pit ◽  
Monitoring Point ◽  
Wall Movement ◽  
Stress Components

Abstract Ensuring the safety of existing structures is an important issue when planning and executing adjacent new foundation pit excavations. Hence, understanding the stress state conditions experienced by the soil element behind a retaining wall at a given location during different excavation stages has been a key observational modelling aspect of the performance of excavations. By establishing and carrying out sophisticated soil–structure interaction analyses, stress paths render clarity on soil deformation mechanism. On the other hand, column-type soft ground treatment has recently got exceeding attention and practical implementation. So, the soil stress–strain response to excavation-induced disturbances needs to be known as well. To this end, this paper discusses the stress change and redistribution phenomena in a treated ground based on 3D numerical analyses. The simulation was verified against results from a 1 g indoor experimental test conducted on composite foundation reinforced with long and short cement–fly ash–gravel (CFG) pile adjacent to a moving rigid retaining wall. It was observed that the stress path for each monitoring point in the shallow depth undergoes a process of stress unloading at various dropping amounts of principal stress components in a complex manner. The closer the soil element is to the wall, the more it experiences a change in principal stress components as the wall movement progresses; also, the induced stress disturbance weakens significantly as the observation point becomes farther away from the wall. Accordingly, the overall vertical load-sharing percentage of the upper soil reduces proportionally.

scholarly journals Experimental study on load sharing characteristics of long-short CFG pile composite foundation adjacent to rigid retaining wall rotating about its base

2021 ◽  
Author(s):  
Bantayehu Uba Uge ◽  
◽  
Yuan-Cheng Guo ◽  
Keyword(s):  
Large Scale ◽  
Retaining Wall ◽  
Back Analysis ◽  
Load Sharing ◽  
Composite Foundation ◽  
Wall Movement ◽  
Great Insight ◽  
Cfg Pile Composite Foundation ◽  
Sharing Behavior ◽  
Cfg Pile

Practicing geoengineers and researchers generally consider the load sharing behavior in multi-type pile composite foundation as an important design aspect. On the other hand, due to urbanization, such foundation system in cities will inevitably appear next to supported excavation. This paper discusses the result from relatively large-scale indoor experiment conducted to investigate the load sharing behavior of loaded long-short CFG pile composite foundation behind a neighboring rigid retaining wall undergoing rotation around the bottom. It was found that with progression of wall movement, the hidden load from soil displacement was borne by the piles with marked reduction in soil load sharing. At the end of wall rotation, the percentage of long piles’ head load increment needed to arrive at a new static equilibrium was about 12.57~32.22% while the end bearing increased by more than 97%. The consequences on the short piles, however, were manifested with an increasing pile head (13.42%) and toe (28.9%) load for the pile far from the wall whereas the closest one experienced a certain increment up to 15×10-4rad wall rotation and finally the head load and end bearing decreased to 8.28% and 12.63%, respectively. The 3D numerical back analysis conducted using FE software ABAQUS yielded the pile – soil stress ratio lower than the value obtained from the experiment but provided great insight into pile settlement characteristics during wall rotation.

scholarly journals CFG Pile Composite Foundation: Its Engineering Applications and Research Advances

2020 ◽  
Vol 2020 ◽  
pp. 1-26
Author(s):  
Bantayehu Uba Uge ◽  
Yuan-Cheng Guo
Keyword(s):  
Load Transfer ◽  
Retaining Wall ◽  
Interaction Mechanism ◽  
Composite Foundation ◽  
Future Research ◽  
Engineering Applications ◽  
Foundation Pit ◽  
Almost Everywhere ◽  
Cfg Pile Composite Foundation ◽  
Cfg Pile

Problematic soils exist almost everywhere on the globe. State-of-the-art solutions to make civil engineering infrastructures built on them are still highly sought. The CFG (cement-fly ash-gravel) pile composite foundation system has been widely used in buildings, highways, railways, and bridge transition sections owing to its proven engineering characteristics in soft ground treatment. This paper discusses about the development and achievements of its engineering applications, along with possible future research directions. The remarkable evolution took place in the past to address projects’ strict differential and postconstruction settlement control requirements including embedding the geosynthetic layer into the load transfer platform and combining it with rigid slabs, as seen implemented in few CFG pile-supported embankments. It was also observed that the interaction of the existing CFG pile composite foundation with an adjacent new foundation pit excavation inevitably presents a complex soil-structure interaction mechanism among the fundamental components—the retaining wall, mat, piles, cushion, and soil.

scholarly journals 3-D Numerical Study of Mechanical Behaviors of Pile-Anchor System

2014 ◽  
Vol 580-583 ◽  
pp. 238-242
Author(s):  
Ri Cheng Liu ◽  
Bang Shu Xu ◽  
Bo Li ◽  
Yu Jing Jiang
Keyword(s):  
Simulation Analysis ◽  
Numerical Study ◽  
Bending Moments ◽  
Mechanical Behaviors ◽  
Foundation Pit ◽  
Anchor System ◽  
Anchor Cable ◽  
Axial Forces ◽  
Toppling Failure ◽  
Potential Failure

Mechanical behaviors of pile-soil effect and anchor-soil effect are significantly important in supporting engineering activities of foundation pit. In this paper, finite difference method (FDM) was utilized to perform the numerical simulation of pile-anchor system, composed of supporting piles and pre-stressed anchor cables. Numerical simulations were on the basis of the foundation pit of Jinan’s West Railway Station, and 3D simulation analysis of foundation pit has been prepared during the whole processes of excavation, supporting and construction. The paper also analyzed the changes of bending moments of piles and axial forces of cables, and discussed mechanical behaviors of pile-anchor system, through comparisons with field monitoring. The results show that the parameters concluding vertical gridding’s number, cohesion of pile and soil, and pile stiffness have robust influences on supporting elements’ behaviors. Mechanical behaviors of supporting pile and axial forces of anchor cable changed dramatically, indicating that the potential failure form was converted from toppling failure to sliding failure.

Stress Path Tests with Controlled Rotation of Principal Stress Directions

2009 ◽  
pp. 516-516-25 ◽  
Author(s):  
JRF Arthur ◽  
S Bekenstein ◽  
JT Germaine ◽  
CC Ladd
Keyword(s):  
Principal Stress ◽  
Stress Path ◽  
Stress Directions

Analysis of the Effects on Optimization Design about Double-Row Piles Retaining Structure

2012 ◽  
Vol 204-208 ◽  
pp. 72-78
Author(s):  
Yu Wang ◽  
Yan Ting Yang ◽  
Feng Yu ◽  
Guang Lei Hu
Keyword(s):  
Optimization Design ◽  
Internal Force ◽  
Composite Foundation ◽  
Foundation Pit ◽  
Double Row ◽  
Retaining Structure ◽  
Supporting Structure ◽  
Arch Effect ◽  
Space Effect ◽  
Foundation Pile

Double-row piles retaining structure has been widely used in the project now, but the stress mechanism of double-row pile is more complex; Its internal force and deformation are affected by many factors. Understanding and mastering its effects has an important significance for the design and the optimization of double-row pile supporting structure. According to the comparison of the measured data and theoretical calculation about original support scheme and optimized support plan and combined with the soil test data, this paper takes the Jinan Cultural Arts Center(Theatre) stage bin foundation pit as an example to analyse the main effects of optimization design about double-pile supporting structure. The results show that soil shear strength, soil arch effect, influence of CFG composite foundation, pile-beam synergy effect and space effect of foundation pit play an important role for optimization design about double-pile supporting structure.

Influence of Initial Anisotropy, Stress Path and Principal Stress Rotation on Monotonic Behavior of Clean and Mixed Sands

2020 ◽  
Vol 857 ◽  
pp. 417-430
Author(s):  
Kazem Fakharian ◽  
Farzad Kaviani Hamedani
Keyword(s):  
Principal Stress ◽  
Stress Path ◽  
Silica Sand ◽  
Large Strains ◽  
Principal Stress Rotation ◽  
Soil Behavior ◽  
Stress Rotation ◽  
Fabric Evolution ◽  
Initial Anisotropy

It is widely accepted that soil behavior is complicated taking into account soil anisotropy owing to the fact that this phenomenon arises from oriented soil fabric or structure forged in the deposition stage. In this study, a review of major findings of authors’ previous studies are presented with the main focus on soil anisotropy using extensive experimental results incuding Triaxial (TXT), Simple Shear (SSA), and Hollow Cylinder (HCA) apparatus. Effects of initial anisotropy, fabric evolution, stress path, principal stress rotation and intermediate stress state are evaluated for a crushed silica sand. In addition, the effects of Portland cement content and granulated rubber contents on anisotropic behavior of the sand are investigated. Bender elments are mounted on triaxial specimens both in vertical and horizontal directions to measure the shear wave velocity and hence maximum shear modulus at the end of consolidation as well as during shearing up to large strains at critical state condition, as an index of evaluating the fabric evolution. The effects of principal stress rotation and stress paths reveals the crucial role of soil anisotropy on the behavior of clean sand. However, adding either cement or granulated rubber to the sand has considerably decreased anisotropy.

scholarly journals Numerical Analysis on the Performance of the Underwater Excavation

2020 ◽  
Vol 2020 ◽  
pp. 1-14
Author(s):  
Bo Li ◽  
Cangqin Jia ◽  
Guihe Wang ◽  
Jun Ren ◽  
Gaofeng Lu ◽  
...  
Keyword(s):  
Numerical Analysis ◽  
Retaining Wall ◽  
Lateral Wall ◽  
Surface Settlement ◽  
Design Parameters ◽  
Analysis Model ◽  
Deep Foundation ◽  
Foundation Pit ◽  
Wall Deflection ◽  
Total Settlement

Based on the Yongdingmen Station of Beijing Metro, the underwater excavation method for deep foundation pit was introduced. This study constructed a numerical analysis model to analyze the performance of surface settlement and lateral wall deflection in the process of underwater excavation. Results showed that this method was better to control the surface settlement and lateral wall deflection compared with other dewatering excavations. In detail, most of the surface settlement was caused during the dry excavation stage and dewatering excavation stage while the deflection caused by underwater excavation only accounted for about 10% of the total settlement. Besides, the maximum settlement occurred 0.25∼0.5 H e behind the retaining wall and the value was 0.04% H e . Similar to the result of the surface settlement, most of the lateral wall deflection had been completed before the underwater excavation, which only caused about 7% of the total deflection. The maximum wall deflection and its location were approximately 0.06% H e and 0.5 H e , respectively. Moreover, a series of 3D numerical analyses were studied on the design parameters of the underwater excavation method. This study can be used as a reference for general performance and structural design of foundation pits with underwater excavation.

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