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CVEN 9521: Slope Instability and Stabilisation

ASSIGNMENT THREE-2025

Notes: 1.This assignment is worth 40%of the marks for this subject.

2.The assignment must be done by students without collaboration with each other.The  penalty for plagiarism will be   failure in the subject as a minimum penalty.

3.The assignment is due no later than Sunday 3rd August 2025,and must be uploaded on to 'Turnitin'through Moodle.

THE ASSIGNMENT

The plan, section, and notes describe landsliding which has occurred affecting the railway line near Coalcliff, north of Wollongong. Also attached are some laboratory test results from that site, and a nearby site in similar geological conditions.There are two potential slide surfaces:

ABCDEF, the lower slide surface, of which BC is parallel to the claystone bedding (along a bedding surface shear); CD is across the claystone bedding; AB and DE are in talus; and EF is in ash fill.

ABDEF,in which BD is in claystone across the bedding in the claystone and AB, DE, EF are as for the other surface.

The landslide moves when the piezometric level reaches the peak groundwater  level surface“W”.

Based on this information:

PART1 (20 marks)

(a)     From the laboratory test data, determine the effective stress shear strength parameters you feel are appropriate for:

(i)     the  failure  surfaces  AB,DE(Talus)and  EF(ashfill)

(ii)    the failure surfaces BC

(iii)   the failure  surfaces BD and CD.

(b)     Analyse the factor of safety of ABCDEF and ABDEF using your parameters and the peak groundwater level.

(c)     Use back-analysis methods to refine your estimates of the shear strengths for the surface(ABCDEF or ABDEF) you consider to be the critical one. To do this assume the laboratory strengths are reliable for the Talus, Ash, and along BC (parallel to bedding). In other words, use the back-analysis to determine the strengths on either BD or CD,depending on which surface you deem to be critical.

PART 2 (15 marks)

Design,including carrying out stability analysis,a stabilization method for the landslide sufficient to give a factor of safety of at least  1.4 for each surface.Your design should incorporate sub-surface drainage AND cutting and filling.The railway cannot be moved, and must stay open for all the time remedial works are under construction.Include a plan and section (marked up on the plan and section provided)of your remedial design,along with  details  of the construction of the remedial works and difficulties you  expect to encounter.In planning your design,consider stability during construction of the remedial works.

PART 3 (5 marks)

Conduct an alternate analysis of the critical slip surface,either before or after stabilisation measures have been implemented,by hand using the two-wedge method.Compare and contrast your hand-calculated FOS with that obtained by computer analysis.

PARTS  1 and 2. Stability analysis should be done using SlopeW or similar or a program you use at work.You must include the results of the analysis with properties assumed shown on the diagrams showing the result.Include the results of the various trials used in the back-analysis.