CEGE0031 ADVANCED SOIL MECHANICS

COURSEWORK 1 (30%):

Comparing  the  mechanical  behaviour  of  the  reconstituted  and natural (intact) soils of a Quarternary clay (Bothkennar clay)

This is an in-depth study of reconstituted and natural soil behaviour of the Bothkennar clay,  from  the  UK,  which  has  been  extensively  studied  in  the  90’s.   See  excel spreadsheet and reference papers from Moodle, and make additional references.

Each group is required to make an oral presentation of data analyses (detail provided in section B). The final Powerpoint Slides should be uploaded to Moodle by 12 Nov Tuesday by  12:00 noon. Group presentation plus Q&A will be carried out in my office GM08 the next day on 13 Nov Wednesday. (each student needs to do a part of presentation; timeslot will be allocated later). This is 10% module mark.

The final written group report should strictly follow the structure below (as shown in  section A). The word limit is 2,500 words (please state word count at the end of  conclusion). Reference list, figures, tables, and appendices should be attached at the  end of the report; they excluded from word count. The submission deadline of the  final report is Monday 25 Nov by 12:00 noon via Moodle. This is 20% module mark.

Only one member is required to submit the presentation slides and final report, file name should clearly indicate your group number.

A. STRUCTURE OF REPORT

1 Background, around 600 words

Background should include basic information of the Bothkennar clay:

•   Site location: a brief description of the sites where the soil was found.

•   Geological  history:  the  formation  process  of  Bothkennar  clay,  i.e.  the geological   history   of   the   soil:   how   and   when   they   were    deposited (sedimentation),   and   what   happened   post-deposition   (post-sedimentation processes and whether there was diagenesis process).

•   Site investigation: information such as composition, index properties, water content, sensitivity, and how they were obtained.

[20 marks]

2 Laboratory test results of the reconstituted soil, around 600 words

•   Reconstituting process: This section will include a first paragraph describing the reconstituting process of the natural clay in the laboratory.

•   Data  analyses:  You  will  analyse  and  describe  both  the  compression  and shearing laboratory tests of the reconstituted specimens of the clay. The data from triaxial tests on  four  specimens  of reconstituted  Bothkennar  clay  are available to you: B21, B22, B46 and B71. The following graphs that should be included: (a) v-lnp′, (b) q′-p′ (during both consolidation and shearing), (c) q′-εs, and q′/p’-εs  (for all the shearing tests), (d) u- εs  (for undrained shearing) or εv-  εs (for drained shearing), and (e) secant shear stiffness vs shear strain G- εs  (with εs plotted in semi-log scale).

•   Discussion:  You  will  fit  your  data  within  the  Critical   State  framework, calculate and list in a table all Critical State parameters for compression and shearing.  Make  discussion  of the  calculated  parameters  of these  tests  and compared  with  published  data  found  in  the  literature.  Also  discuss  what limitations of the Critical state framework were observed.

[20 marks]

3 Test results of natural (intact) soil and comparison, around 600 words

•   Sherbrooke Sampler: The data from triaxial tests on two specimens of intact Bothkennar clay are available to you: SH5 and SH13. They were recovered using  a  Sherbrooke  sampler.  You  will  provide  a  brief  description  of this particular method of sampling used to recover undisturbed (intact) samples, and how this sampler method is compared to the Laval sampler?

•   Data  analyses:  You  will  present  your  analyses  of  the  compression  and shearing laboratory tests on the undisturbed specimens of the clay. The same set of graphs that should be included here are: (a) v-lnp′, (b) q′-p′, (c) q′-εs, q′/p’-εs, (d) u- εs  or εv-εs  (either for drained or undrained), and (e) secant shear stiffness vs shear strain G- εs  (in semi-log scale).

•   Discussion:  Finally,  you  will  compare  your  data  with  the  corresponding specimens of the reconstituted soil presented in the previous section. Also discuss what limitations of the Critical state framework were observed.

[20 marks]

4 Effects of structure on soil behaviour, around 600 words

•   Effects of natural clay structure: Briefly summarise the effects of structure during compression and shearing, and the various frameworks used to analyse clay structures.

•   Data  analyses:  This  section  should  include  an  analysis  of  the  effects  of structure on the behaviour of the natural clay and the reconstituted clay, and calculate the sensitivity of each intact sample. You will use normalised stress path plots to support your argument (graphs showing q′/pe ′-p′/pe ′ and Iv-lnp′ of both the intact and reconstituted samples  should be included when making comparison).

•   Discussion: Compare unique features of the structure of Bothkennar Clay, and how they compares to other natural clays.

[20 marks]

5 Conclusions, around 100 words

•   You will summarise their similarities and differences of the soils within the Critical State framework.

•    Total word count = XXXX

•   Word count should be strictly followed: -10 marks if >2500 words, -20 marks if >10% but capped. But note reference list, tables and figures and appendices are excluded from word count, see below.

6 Reference list

7 Tables and Figures

•   You must put  all  Tables  and  Figures  at  the  end  of report,  figures  should clearly  label  how  you  obtain  each  critical  state  parameter,  and  any  other parameters that you discussed in the report.

•   At the bottom of each figure, please include a description about the calculation steps, formulae

•   And mark clearly on the figure the critical state parameters values obtained.

8 Appendices

•   You can put other supporting calculation steps, formulae and assumptions you made in your calculation in appendices.

•   Please submit your excel spreadsheets on a separate Tab. [20 marks]

B. PRESENTATIONS

The  presentation  should  include  some  background  about  Bothkennar  clay,  your objectives e.g. how to determine the parameters for the reconstituted and intact soil. You will present graphs you have managed to produce so far, if not, parameters you were able to derive and how. If applicable, you will comment on the differences between the intact and reconstituted soil. At the end of the session you should have clear directions for your final hand-in the following week.

The presentation time is 10 minutes maximum, followed by Q&A. It is suggested 8  core slides are used: 1 slides of background information, max 5 slides for graph (a)-(e) comparing the reconstituted and intact soil behaviour in each slide, and 2 slides can be  used to show the effects of soil structures on natural soil behaviour using sensitivity  and soil normalisations calculations. You can also add a conclusion & references slide.

Your powerpoint  slides  should  be  submitted  to  MOODLE  in  advance  (only  one person in each group should upload the Powerpoint file). You are reminded to make sure that each figure has a title, all the axes labels are legible and big enough font size with correct units and there is a legend with consistent line colours and markers.

You should upload your presentation file to moodle before deadline stated on page 1, showing the up-to-date data analyses of the project. The specific timeslot of your group presentation will be announced nearer the date. The oral presentation needed to be shared between students in the group.

Marks allocations:

-    25 marks: Background and knowledge of C.S. behaviour and parameters

-    25 marks: Clear comparison of reconsituted and intact soil behaviour

-    25 marks: Knowledge of soil structures & sensitivity framework

-    25 marks:, Accuracy of data analyses and performance during Q&A

[Please rehearse timing: -5 marks if exceeds 10 mins, -10 marks if exceeds 11 minutes]

CEGE0031 Advanced soil mechanics CW1 marking criteria:

For each section, the following marking criteria applies:

Exemplary (90%-100%): Fulfilled all the required tasks with an exceptional level of insight,  thoroughness,  and  originality.  Comprehensive  yet  clear  and  concise. Impeccable English and presentation.

Outstanding (80%-89.99%): Fulfilled all the required tasks to a very high standard with  no   significant  error  but  may  be  lacking   slightly   in  some  aspects  of secondary significance (e.g. conciseness or some minor presentation flaws).

Very  Good  (70%-79.99%):  Shows  an understanding  of the problem  and how to solve  it.  Got  everything  right  except  for  a  few  minor  errors,  inaccuracies  or presentation flaws.

Good (60%-69.99%): Good understanding of the problem and how to solve it. Got  most  of  the  results  right  but  made  a  few  mistakes  or  showed  some  slight  misunderstandings. Good overall presentation but maybe lacking in a few places.

Satisfactory (50%-59.99%): Shows a Satisfactory understanding of the problem and solves a significant fraction of it correctly but may contain some serious mistakes or misunderstanding. Presentation acceptable but can be poor in places.

Fair (40%-49.99%): Most requirements attempted but shows limited understanding of the problem or detailed knowledge. Contains mistakes, misunderstandings, or irrelevant material. Organisation and expression and presentation inadequately poor and standard or presentation.

Fail (0%-39.99%): Very limited understanding of the question asked and how to answer  it.  Some  marginally  relevant  material  and  limited  content  but  badly organised  with  frequent  errors  and  misconceptions.  Serious  weaknesses  in presentation. Also applies to  submissions that are most completely irrelevant, messy or missing altogether, or submissions showing clear plagiarism.