Geotechnical Engineering 3 (Module Co-ordinator: Prof Ian Jefferson) Coursework brief for Computational Modelling*

2022 -2023 Academic Year

Please read the following instructions carefully

Instructions for submission: Please submit the following required files and documents; the deadline for submission is 23:59 Friday 16th December 2022 via Canvas. You will be penalised if you submit late (5% per working day). Each group needs to submit two files. You are advised to attempt the exercise as soon as possible and prepare your report well before the deadline. Peer assessment is available (see below) and will be used to adjust final marks by no more than plus/minus 10%, to reflect an assessment of contributions across the group. All peer assessments are subject to final moderation by the module delivery team. If you do not submit a peer assessment, every team member will be given the same mark.

The first file is a professional report of maximum 10 pages excluding title page, contents, list of figures, list of tables, nomenclature, and references/bibliography – NO appendices are allowed (you will lose 5% per page over the limit). Submit the report file in PDF format. It is recommended to type the report using a word processing software e.g., Microsoft Word, Latex. The report should be singled line, font Arial, minimum font size 11, and minimum margins of 2 cm from top, bottom, left and right. On the title page of your report, you must clearly add the name of the group members, your group number, and the following phrase followed by signatures from all members, “We are aware of and understand the University’s policy on plagiarism and we certify that this assignment is our own work, except where indicated by referencing, and that we have followed good academic practices”. Submissions without title page as set out will not be considered and any subsequent delays will be count to late penalty marks.

The second file of your submission is your ABAQUS files (*.cae and *.inp). Please note that in total there are four ABAQUS simulations (three for Question 1 and one for Question 2). Please zip the ABAQUS files for both questions into one file (use the standard zip available in Windows OS or iOS). Each file size cannot exceed 3 MB. Only one member of the group needs to submit the required files. Group numbers and members are allocated separately. The file names should only contain the group number and the ABAQUS files should contain both the group number and the question number separated by an underline. For example, group ‘23’ will submit two files of ‘23.zip’ and ‘23.pdf’. In the 23.zip, there should be eight files as follows, ‘23_Q1a.cae’, ‘23_Q1a.inp’, ‘23_Q1b.cae’, ‘23_Q1b.inp’, ‘23_Q1c.cae’, ‘23_Q1c.inp’ ‘23_Q2.cae’, and ‘23_Q2.inp’. Each group has a unique set of values for the parameters and so please make sure you choose the correct values otherwise you will lose marks. If you have any questions, please contact Dr Asaad Faramarzi (A.Faramarzi@bham.ac.uk).

Allocation of marks:

Quality of the report including overall writing, English, presentation, referencing: 15% Results, and discussions (including hand-calculations and choice of parameters): 50% Numerical modelling: 35%

* Note: This coursework is worth 30% of your final mark for Geotechnical Engineering 3

Question 1: You are required to carry out the simulation of triaxial experiments on samples of clay using the ABAQUS software package. There are two experiments to simulate (Parts a and b) and details of each are given below. The material constitutive model is Modified Cam Clay (MCC) which is available in ABAQUS. For both parts you need to compare the software outcomes with those from hand- calculations. It is important that you justify any selections, assumptions or choices made. Additionally, there is a further simulation (Part c), where you use Mohr-Coulomb plasticity material model to simulate the triaxial test in Part (a).

Part (a) – Simulate a consolidated drained (CD) triaxial test using the values provided in Table Q1 with ABAQUS. The geometry and meshing of the model are shown in Figure Q1 (please follow this exactly). Only model a quarter of the test as shown in Figure Q1. In addition, carry out the analysis for the above problem using hand-calculations for the shearing stage of the analysis. Present the hand calculations in a table where you should present the evolution of p’, q, and e over an appropriate number of increments. Present the full calculations for at least one line of the values in the table. Plot (p’-q), (ev

– e1), (Ln(p’) – e) and (q – e1) for both the numerical and analytical methods. Your group should compare the results of the FEM analysis and hand calculations and discuss any differences.

Part (b) – Repeat part (a) for a consolidated undrained (CU) triaxial test [note: instead of (ev – e1) plot (u– e1)]. In addition, compare the results from part (a) and part (b) and discuss.

Part (c) – Simulate the triaxial sample in Part (a) of this question using an elastic perfectly plastic material constitutive model with linear elasticity and Mohr-Coulomb yield criterion. As part of this simulation, you need to discuss and justify how you have derived the material model parameters. Furthermore, compare the results with those of Part (a) and discuss any differences in detail from both materials model behaviour and the results of numerical analysis. [note: you are not required to carry out hand-calculation for Part c]

Table Q1: Material and loading parameters

Figure Q1: Triaxial consolidation: geometry (H=50 mm, r=25 mm) and loading

Question 2:

Calculate the ultimate bearing capacity, and its corresponding settlement, for a 2-m wide, 0.5 m thick strip footing on the surface of a 10-m saturated layered soil using ABAQUS. Due to symmetry, only half of the foundation should be modelled. The plane strain finite element mesh employed in this analysis is shown in Figure Q2. Nodal points on the side boundaries are constrained to move vertically only, while those along the base are fixed in both the horizontal and vertical directions. The top 3m of the soil near the ground surface is formed of medium dense Leighton Buzzard Sand. The underlying layer is 7m thick of the same sand, but with a high density. The ground water table is 3m below the ground surface. Assume the foundation is made of concrete, has a linear elastic behaviour (E=40 GPa

and n =0.15) and has a unit weight of 25 kN/m³. Carry out the ABAQUS analysis and plot the results

of the ABAQUS analysis in the format of pressure vs. settlement and on the same graph compare the results with those from available classical methods to determine the ultimate bearing capacity and settlement of strip foundations (details available from any Soil Mechanics or Foundation Engineering text book) and discuss any differences. It is important that you justify and provide reference(s) for any selections, assumptions or choices made. Clearly show the full working-out for the hand- calculations.

Figure Q2: Geometry of the plane strain footing

Table A1: Parameter combinations for the coursework groups

Table A2: Coursework group numbers and members

PEER GROUP ASSESSMENT