Analysis and Examination of the Effect of Overhead on Susceptible Soils to Liquefaction, Modified with Stone Column System under Dynamic Loads
The phenomenon of changing the behavior of sand from solid to liquid has been recognized as the first step in the development of soil mechanics. For the first time in 1936, Casa Grande recognized the phenomenon of sand liquefaction and its effects. The instantaneous liquefaction was used by Terzaghi and Peck in 1948 to demonstrate a change in loose sand sediment and their flow which was similar to a viscous fluid that arose as a result of a slight disturbance. A substantial research has been conducted on both the implementation method and the design of the stone column.
This method is based on the replacement of 15 to 35 percent of the inferior soil by digging wells with a certain diameter and depth and distance from each other and filling the wells with sand, gravel or pebbles and compressing it into vertical columns. The granular materials are poured into the drilled well in a stratified manner, compressed and vibrated by special machines. In this research, after identifying the phenomenon of liquefaction, soil behavior, stone column method, seismic waves and etc., the problem was defined and physical and boundary specifications and parameters were determined. Data was calibrated with valid references and then modeled on the FLAC finite-element software.
This modeling is important for simulating the natural phenomenon of liquefaction under seismic load (earthquake). In general, the simulation model of stone column is modeled on a susceptible to liquefaction sandy soil under the effect of overhead with seismic loading.
Numerical methods based on the model of equations used to have several types which in the following several of the most commonly used ones are presented:
1. Finite-Element Method
2. Finite Difference Method
3. Distanced Element Method
4. Boundary Element Method
FLAC 2D or the Fast Lagrangian Analysis of Continua is one of the most popular software for geotechnical engineers and researchers and is one of the products of the American company, Itasca. The company offers software such as UDEC, 3DEC, FLAC 2D, FLAC 3D, PFC, etc., which is nowadays professionally used in many soil mechanics and rock mechanics designs.
The logical phases of simulation and analysis in the FLAC 2D software are as follows:
1. Making geometry of the environment
2. Determination of boundary conditions
3. Introduction of mechanical and resistance characteristics of the environment
4. Applying forces of gravity and external forces
5. Creating an initial balance
6. Applying the operating conditions (e.g. tunnel drilling, pit, etc.)
7. Solving the model for the second time to extract results
Since from the start, this software has been developed for geotechnical modeling, it has several capabilities, such as:
• Instructional and graphical modeling
• Modeling problem solving in elastic, elastoplastic, creep, dynamic, hydrodynamic and two-phase modes
• Defining different behavioral models in the software or even defining a new behavioral model
• Modeling Surface and Underground Structures
• Stepwise and repeatable modeling to study effective parameters
• The ability to model all types of retaining structures (mesh and shotcrete, concrete, steel, retaining wall, bolt and etc.)
• Containing on FISH language for specific tasks in modeling
• Graphical display and presentation of wide quantitative output results
- Display of pore water pressure ratio under dynamic load in all operating conditions
- Demonstration of the settlement under the influence of overhead and other conditions of the problem
- Demonstration of horizontal displacement under overhead effect and other conditions
What you will learn in this documentation
1. Introduction to the phenomenon of liquefaction and stone column method (optimization method).
2. In all cases, the pore pressure of the soil around the stone column significantly decreases with respect to the diameter and permeability of the stone column relative to the free environment.
3. The stone column significantly reduces the settlement, but has a negligible effect on reducing horizontal deformations, thus it cannot function properly under the influence of simultaneous horizontal and vertical displacement.
4. The results indicate that the increase in the number of stone columns has a negligible effect in reducing horizontal displacement, although it can reduce the excessive pore water pressure.
5. The stone column performs well in the depths of the surface, and with the increase of depth, this effect becomes negligible. Additionally, the stone column prevents heterogeneous settlements and structural overturns.
6. In general, the use of stone columns per se, is not suitable for the improvement of liquefaction substrates, and it is recommended that the combination of stone columns and piles be used to improve such substrates.
7. Although the increase in weight of the structures increases the effective stress and decreases the ratio of extra pore water pressure (ru), the simultaneous effect of increasing the vertical and horizontal displacement of the substructures and their significant difference in the non-columnar state caused by the increase in weight of the structure is causing significant overturning that can lead to significant damage to adjacent structures.
Tips and Requirements
1. Introduction to FISH language and elementary programming concepts
2. The software file of this software is available in PRJ format
3. Introduction to the basic concepts of problem conditions such as defining parameters, physical conditions, boundary conditions, material behavior and related equations
4. Understanding the concept of explicit and implicit equations
5. Introduction to soil behavior in different environmental conditions
Objectives of the site in presenting this project
This project has been designed to analyze and examine the effect of overhead on susceptible soils to liquefaction, modified with stone column system under dynamic loads. This project could be helpful for university students, researchers and etc. Also it could be proved useful in scientific and industrial projects, and MSc and PhD theses. In some cases, university students require investigation and research for their MSc and PhD theses. Since the present project consists of a complete project and includes all university flowcharts, it could prove useful.