Four strain gauges, with specification given below, are available to measure the torque on a cylindrical shaft 4 cm in diameter connecting a motor and load. (a) Draw clearly labelled….
Evaluate the undrained performance of a foundation via Strand7 a
Evaluate the undrained performance of a foundation via Strand7 and present a report on the
work. Assessment criterion for the project and requirements for the project report are also given
in the document.
The geotechnical structure is made of concrete. In the computation it is assumed that the
concrete behaves linearly elastically with the Young’s modulus being 12.5×103 MPa and
Poisson’s ratio being 0.13.
The ground soil is soft clay. FEM analyses of the foundation performance in undrained situation
are suggested. It is suggested the undrained behaviour of the soil be modelled by the linear
elastic perfect plastic model. Soil is assumed to be homogenous and uniform. For the soft clay,
the following values of model parameters are assumed: cu =20 k Pa, and Eu = 1000 kPa. The
Poisson’s ratio of the soil under undrained condition can be assumed to be 0.489.
For other information, assumptions may be made based on further research and with
Two types of foundations are given for selection. The types and geometries of them are shown
in Fig. 2. Foundation 1 is a rigid and smooth surface footing. Foundation 2 is a rigid footing
embedded into soil with 0.5 m depth.
Select only one of the foundations and work out the following questions:
(1) Evaluate the performance of the foundation, particularly the load displacement response
curve. The simulation may stop at the settlement = 0.1B (D: the width of the pile) if an
ultimate failure load is not found.
(2) Soft clays are usually treated for better strength and stiffness. One method is by
introducing cementation materials. The strength and stiffness of the cemented clays
general increases with cement amount Aw by weight. Suppose for the given soft clay,
its strength cu and Young’s modulus Eu increase by the following equations:
20 1 150
(a) determine the values of model parameters for Aw= 5 %, and Aw= 25 %.; (b) plot the
calculated stress and strain curves (mainly the shear stress and shear strain curve, mean
effective stress and volumetric strain curve) for the soil simulated by the selected soil
model; (c) also plot the calculated stress and strain curves (mainly the shear stress and
shear strain curve, mean stress and volumetric strain curve) for the concrete material of
(3) Investigate the influence on the performance of a shallow foundation by cementation.
FEM simulations of two or more cases may be made, such as with Aw= %, and Aw= %.
The project report takes the weight of 30% of the course. The project report is evaluated based on the knowledge and capability demonstrated in achieving the following requirements.
(A) The stress strain relationship of the soil and for the concrete material of the foundation (8%);
(B) FEM solution of the problem (10%);
(C) Influence of the width of footing (6%);
(D) Discussions on FEM analyses and results obtained (3%);
(E) Professionalism (3%).
Contents of the Report
It is suggested that a project report contain the following contents.
A title page should include your name, student ID, date and title of the project.
This is a brief summary of your project. Briefly describe the problem, your approach, and the results.
Describe the problem to be solved, the methods used, and features to be investigated.
Finite element method
Describe, based on your understanding not copying textbooks or lecture notes, basic theory, concepts and features of finite element method for the solution of the practical problem.
Constitutive models for soil
Describe the soil models that you will use to solve the problem and present the calculated stress and strain curve. Based on the experimental data provided, (1) determine the values of model parameters for the soil model you will employ for the FEM analysis; (2) plot the calculated stress and strain curves (mainly the shear stress and shear strain curve, the shear strain and volumetric strain curve) for the soil simulated by the selected soil model; (3) also plot the calculated stress and strain curves (mainly the shear stress and shear strain curve, the shear strain and volumetric strain curve) for the concrete material of the foundation.
Description of formulation of the FEM analysis Model
Describe the details of the FEM analysis model you have constructed. Give clear explanations/justifications and present the results, when appropriate, of the main steps in finding an FEM solution. Some of the main steps are: the determination of the boundary and boundary conditions, element discretisation, selection of constitutive models and the values of model parameters; solution of the global equations.
The results should be presented in graphical forms or in simple short lists. Do not submit any numerical computer printouts from Strand7. They are a waste of paper and they will be ignored.
Summarise your results in graphical forms. The summary results need to directly address the purpose of the analysis. Some of the results are load P and settlement curve (essential); vertical settlement of the ground surface; horizontal settlement of the ground surface; stress of soil underneath the footing.
Discussion and analysis of the results
(1) Compare FEM results with those from conventional methods when possible;
(2) Discuss and analysis the results quantitatively and qualitatively;
(3) . Discuss and analysis the influence of footing width on footing performance.