BTP-Presentation for 3rd year students.pptx

B Tech Project

1. Effect of Normal Load and Morphology of particles on interface shear response Supervisor- Dr. Prashanth Vangla Study By- Prateek Singh 2019CE10278

2. Introduction A plane where two different materials interact is called Interface. May be between continuum and continuum, particulate and continuum and particulate and particulate. Examples- Landfill liner, skin friction piles, in situ characterization devices and internally stabilized retaining walls. Based on soil particle and surface roughness of continuum surface- Dilative and Non- Dilative interfaces . Interface of Geotextile and sand vs Interface of smooth Geomembrane and sand Dilative vs Non-Dilative Interfaces

3. Landfill Liner Skin Friction Piles Internally Stabilized retaining Wall

4. Literature Review The interaction mechanisms involved in dilative and non-dilative interface shear are different . Several studies are available in the literature on the shear behaviour of sand geosynthetic interfaces, however, the studies specific to sand geomembrane interfaces are limited. Not many studies are available on the effect of particle morphology on sand geomembrane interfaces

5. Objective There are various factors which govern the interface response Investigate the effect of morphology on interface shear response, Investigate the effect of normal load on interface shear response. Other effects like packaging, void ratio, etc are outside the scope of this study .

6. Materials

7. Methodology Roughness of Geomembrane by a stylus profilometer . Angular sand and glass beads of size (4.5mm- 2.0 mm) were obtained through sieve analysis. Quantification of the Morphology of particulate materials was done through a 3D image analysis through AG- Metashape software. Interface Direct Shear Apparatus – Rectangular platform- 100mm x 100 mm , Shear box – 100mm x 100mm x 55mm has rounded edges Sample Preparation - Soil samples are prepared in three layers giving 30 blows in each layer to ensure uniform density and repeatability and to achieve a target relative density of 80%. The interface tests are done under four normal stresses: 25 kPa, 50 kPa, 100 kPa and 200 kPa. The tests are performed at a displacement rate of 1 mm/minute, and the samples are sheared in the pre-defined failure plane .

8. Interface Direct Shear Apparatus

9. 3D image of Angular Sand Particle stitched using AG- Metashape software

10. Results

11. Results

12. Conclusions Effect of Normal Stress – With an increase in the normal load, the value of peak shear stress increases and it is evident from the figures, that the value of interface friction angle decreases till a critical point around 50Kpa and then again increases. Effect of Particle Morphology- As the angularity of particles is increased, the peak value of shear stress is increased, which can be explained due to increased interlocking between particles and the surface asperities on the geomembrane. Pre-peak behaviour - Peak shear stress reaches a lower strain for lesser angularity particles Post Peak behaviour – More dip in the value of residual stress as compared to peak stress as the angularity of the particle is decreased .

13. Future Scope