Analysis of soil structure interaction problems by the boundary element method

مقدم أطروحة جامعية

al-Suud, Midhat Shakir Midhat

الجامعة

الجامعة التكنولوجية

الكلية

-

القسم الأكاديمي

قسم هندسة البناء و الإنشاءات

دولة الجامعة

العراق

الدرجة العلمية

دكتوراه

تاريخ الدرجة العلمية

2008

الملخص الإنجليزي

The boundary element method (BEM) has become one of the most powerful numerical techniques which has already established itself within the scientific community.

The most striking feature of this technique is that, in principle, only the boundaries of the region being investigated have to be discretized, which therefore leads to many fewer discrete elements than any scheme requiring internal subdivision of the whole body.

This means that the number of unknowns is reduced dramatically, especially for 3D problems, as the unknowns occurred only on the boundary of the problem.

This thesis is devoted to make use of the boundary element method (BEM) as a practical problem solving tool to analyze the soil- structure interaction problems.

Two kinds of programs were adopted for the analysis process.

The first program is a computer package called P Group N which concerned mainly with the analysis of the pile group problems.

A non-linear soil model has been adopted with this program to asses the pile-soil interaction within the group.

Some parametric studies were carried out with this problem including the pile diameter, pile length, spacing to diameter ratio, soil type (sand or clay) and the thickness of stratum.

The second program called MRBEM is written by FORTKN-90 language.

It is a general purpose boundary element method program for solving elasticity and potential problems with multiple regions.

This program was developed during this study to solve a two dimensional problem represented by a tunnel with a concrete lining embedded in clay.

The effects of the variation of soil type (stiff, medium, soft) and depth of the tunnel were taken into account.

The results were compared with those findings in some experimental It was found that when using the BOM in the analysis, the stresses and displacements need only to be calculated where the details of interest occur on the boundary or are localized to a particular part of the domain, and hence an entire domain solution is not required.

Moreover, boundary conditions at infinity can be modeled exactly without the need to extend the region a long distance away or to apply artificial boundary conditions as a result to the arbitrary truncation of the outer region.

The main findings of the application of the BEM to the pile group problem are that for the group of 4 piles embedded in clay, the maximum load carried by the base does not exceed 8% of the load carried by each pile with different diameters.

This low percentage ascertains that the piles embedded in cohesive soils carry most of the load throughout its shaft, For the same group of piles, the distribution of the shear stress is approximately uniform along the interface which means that the unit shaft resistance is constant and independent of the effective overburden pressure * This feature as, as compared with other studies, is apparent when K=5000 (K= Epuc / EwM) where the pile is considered as incompressible.

For the lined tunnel problem, it was found that the ground surface settlement shows its maximum value at both sides of the tunnel and not above the center of the tunnel.

Besides, the maximum positive stresses at the lining interface occur at the crown and invert region.

These stresses tend to decrease gradually until they reach their minimum negative values at the springline region.

Among these three regions, the shoulder and the knee represent mid-side regions at which the stresses become close to minimum positive values.

التخصصات الرئيسية

الهندسة المدنية

الموضوعات

• النماذج الرياضية

• APA
• MLA
• AMA

لغة النص

الإنجليزية

نوع البيانات

رسائل جامعية

رقم السجل

BIM-305478