For the final portion of our geohazards course, we will be focusing on engineering geology, specifically related to landslide hazard mitigation.
There are two main projects we have to tackle, in the first we assess and measure different landslides in the field as we drive around near Pokhara. Overall, Nepal has a very high landslide hazard due to its steep topography. Furthermore, while lots of new roads are being built, many use a cut-and-fill technique wherein half the road is cut out of the hill slope and the removed material is placed downhill to create the other half of the road and then no civil or bio-engineering is used, making the road-cut extremely vulnerable to landslides. We visited four sites in total and worked through mapping, assessing, and making suggestions for better mitigation techniques.
For the second part of the project, we visited one site in Chobhar, Nepal. The location was an old limestone quarry and was actually quite beautiful with short cliffs and a wide pond. We were working on the opposite slope which would be the location of our imaginary future road-cut. The overall goal was for each person to design a safe road-cut for the area.
Designing the road-cut involved a number of different steps. In order to use kinematic analysis to make decisions on cut slopes, we needed to measure the dip and dip direction of all the discontinuities on the rock face. To create a comparative study we did this both by hand and using technology. By hand, I measured 35 discontinuities with my compass and pooled data with others to get 105 total measurements. The other method was a bit more complicated. First we used Metashape to create a structure from motion 3D version of the outcrop. The data from this was then inputted into SplitFX which created a mesh and mapped flat surfaces of different angles to give us dip and dip direction information. Then finally using DipAnalyst we created stereonets and got values for the probability of topple failure, wedge failure, and plane failure. From this data we designed a potential road cut trying to maximize safety while still keeping costs low and proposing additional civil and bio-engineering techniques.
We had one last write-up day to finish up the first two courses of the summer. Compared to previous write ups, this one was actually not super stressful and crammed! I was able to finish in time easily while relaxing in the peaceful garden of Yantra House (with some slightly loud chickens).
I am happy to report that the cat is slowly starting to warm up to us! She comes out much more often now so I’m hoping to make friends soon….
Next week we leave the group either alone or with a partner to start our independent field study project, so I’m getting excited to research water quality in Kathmandu Valley!
Be well, be joyful,