Soil Investigations: August 4-14, 2010

As part of site selections for TEREP, we did some preliminary soil investigations on three sites. Since hiring a geotech company to come out and do these investigations would cost a lot of time and money, we did them ourselves, with equipment from Andalas and UNP.

August 4, 2010 – UNP
UNP (Padang State University) is one of the most promising sites for the TEREP project so far. So we borrowed a hand auger and a lab technician from Andalas University to go do the investigations. But Andalas is really far and the equipment is heavy. We really needed either a car or at least two motorbikes. We had a car for the morning and only one motorbike for the rest of the time.

There were only three of us but the lab technician really knew what he was doing so we started pretty fast after we got to the site. But less than a meter into the ground, we hit a lot of gravel. The hand auger cannot penetrate the layer of rocks. We were then told that most of the university sits on a layer of fill about a meter deep. We had only hoped to go down about 2 meters deep in the first place. We poked around some more after lunch but got no success. I took a sample of the fill and we're hoping do grain size analysis on all the samples very soon.

August 5, 2010 – Seismic CPT
We had heard from Adrin Tohari at LIPI that UNP has a Seismic CPT machine at their campus. This CPT machine looks like all the other ones in this region. It is a Sondir-type machine that has a hydraulic (I think) motor attached to it. There is no truck involved. The reaction for the machine seems to be just the motor. The special thing about this machine is that it has the capability of doing seismic wave tests.

We were able to verify its existance. But it is currently sitting in storage at UNP because no one knows how to use it. It's such a shame because it is probably the only machines in all of Sumatra that can do both CPT and seismic waves. I contacted the company (Geomil) in the Netherlands and they sent me some instructions. The representative said that the machine is very similar to other Sondir machines so that someone experienced with those machines can operate this one with no problems. They also gave me a contact for a company in Singapore. It would be nice to get this machine up before we leave.

We also got permission to borrow (rent) UNP's hand auger for more soil exploration. The equipment at Andalas turned out to be unavailable and really far from where we want to do investigations. So we managed to borrow the equipment along with three undergraduate students and two motorbikes for the next two days.


August 6, 2010 – Terminal Lubuk Buaya
This site is a very swampy field with some overgrown vegetation and lots of children running around. The watertable is very high, at around 40cm from the surface. Because we did not have a GPS or surveying equipment, we paced out the field using the neighborhood houses as our references.



August 7, 2010 – Basko River Site
This is the site that the ESW Spring 2010 TEREP Design Team (aka Lil Bermie) did the conceptual design project on. This site is across the river from the Basko Hotel, a major landmark in the city.

The investigations went a lot more smoothly because everyone knew what they were doing. We hit a lot of obstructions, mostly large gravel. We managed to finish by lunchtime. We went out to lunch together afterwards. The short day and food was much appreciated by everyone since it was Saturday!



August 13 and 14, 2010 – Grain Size Analysis at Andalas
We collected 13 soil samples total. We dried them in the tiny oven in the soils labortaory at Andalas. This lab seems to be heavily used by students working on projects even though it is summer vacation. After drying, we put them through a sieve shaker and weighed each sieve to determine the grading of each sample.



The Report
I have organized my notes into a report on this preliminary site investigation. This can be found here:
http://www.stanford.edu/~lucywu/TEREP/PDFs/

Preliminary Mosque Survey

One of the main objectives of this internship, following the work done in the class last Spring, is to investigate a number of mosques for their adequacy as vertical evacuation structures. As you can see in the booklet (link) created by the retrofit team, mosques are great options for evacuation, but they are certainly not guaranteed to be safe during the earthquake and tsunami without further investigation and possibly retrofit, both structural and non-structural.

The first step was to identify about 10 mosques from Google Earth that looked decent for evacuation based on their distance from the coast, the flow depth at the site based on the Last Mile inundation map (link), the population density in the region, and Andi’s knowledge of the mosque’s height, quality, and any other useful information (the benefits of working with a local). After compiling this information during a long afternoon in the Construction Clinic, we chose 8 mosques to visit.

One of the students who finished undergraduate study in Civil Engineering at Andalas University, and now attends Bandung Institute of Technology, Anggun, was able to accompany Andi, Lucy and I in the investigation. We drove (yes, not angkots this time) to four mosques in one afternoon to speak with many of the mosque managers and briefly survey the size and height of the mosque that seemed plausible from our Google viewing. Four days later, we went to three more mosques somewhat near the coast to accomplish the same tasks. We even stopped by an extra one because we ran into it on the way (shows the proliferation of mosques in the city).

Through our investigation (see some photos here, here, and here), we were able to identify 3 mosques that we will investigate further to be used as vertical evacuation structures based on their size and height. We will need to dig deeper in order to find out how much steel is in the members and the quality of the concrete to make our own structural drawings for analysis. Also, most need better access, especially to the roof, in order to be plausible and that is something we will discuss with the owners and mosque managers when we return.

We plan to analyze two mosques while still in Padang with the Andalas students, or at least get the process well-started so they can continue for their class in September and proceed with more mosques that we investigate. This can be a relatively quick, effective, and economical way to prepare some of the communities in Padang, and with more involvement, it can become scalable as well.

TEPO – Tsunami Evacuation Pedestrian Overpass

Thursday, July 22, 2010

One of the ideas for the next design class is looking into using pedestrian overpasses as evacuation structures. Pedestrian overpasses are very common in Indonesia in general and the ones in Padang performed well in the last earthquake. So we set out to do an initial assessment of the two that are currently in Padang.

From Padang Summer 2010

Tabing. There is one located in Tabing, right next to the train station. This one used to be outside of Basko Hotel but got moved to Tabing, probably because the government thought it would be used more. This one is made with steel.
Some concerns we have about this one:

• Floor panels – They were very thin and rusted. Maintenance is an issue.
  
  

  From Padang Summer 2010

  
  
  
• Connections to the ground – How deep do the bolts go? Are they bolted only to the concrete block?
• Usage – There are discarded cigaretts and graffti, therefore some people use it as a hangout.
• Dimensions:
• 24.24 m long (across the street)
• 2.20 m wide
• 6.3 m high (ground to deck)
• 2 m wide access (entrance)

From Padang Summer 2010

Andalas Plaza. The other one is located outside of Andalas Plaza. The stesp on the mall side of this one is heavily used by people hanging out. When we got there, a bunch of teenage girls were chatting on the steps. There is overhead covering for the stairs and bridge. This one has concrete supports and a metal deck.

• Stairs – Support for stairs looks thin: buckling issues. Flange for the column is only 6” wide. Some bolts are missing.
• Connection to the ground – Not sure how deep the concrete extends below ground.
• Connection to deck – Cannot see how the metal deck is connected with the concrete columns.
• Floor panels – Lots of rusted pieces everywhere. Pools of water. Floor has been patched with different panels. Very thin.
• Dimensions:
• 29 m long (across the street)
• 1.3 m wide
• 6 m high (ground to deck)
• 1.1 m wide access (entrance)

Comments about TEPO idea in general:
Everyday useage will be a big issue. If people don't use it regularly, then they will not think of using it during an emergency. Right now it is easier to walk across the street between traffic than to climb one of these things. The stairs are very steep (around 45 degrees?) and takes a lot of energy to get up. Perhaps escalators will help but they use electricity. At the Tabing overpass, we saw circuit boxes but they were empty.
Maintenance is another issue. In theory, the overpasses can hold a lot of people but the quality of the floor panels are questionable. It seems dangerous to pack a lot of people onto the structure and risk breaking the floor panels.

Capacity is an issue that was brought up at a KOGAMI meeting. They do not hold very much people and are not fully enclosed structure (like the inside of a building). So there is concern of people falling when more and more people try to cram into the space. But perhaps this issue can be solved by having bigger overpasses that straddle an entire intersection and having enough of them.

Not sure what the final solution for the TEPO idea will look like. A feasibility study will definitely be needed before the design of one. Perhaps a comparative study with another city where overpasses are heavily used and well maintained should be done. This could turn out to be a very interesting design project though.

At the time of this writing, we have not managed to get drawings from DTRTB.