School: Virginia Tech University Major: Mechanical Engineering Company: Traylor Bros., Inc. Internship from 05/18/2015 — 08/21/2015
During the summer of 2015 I interned with Traylor Bros., Inc. The project I was assigned to was the construction of the Blue Plains Tunnel which originates under the Advanced Wastewater Treatment Plant in Washington DC. When I began my training, the project was in its final stages of completing the 26 ft. diameter, 4.5 mile tunnel. This particular tunnel is one piece of a 3 tunnel system being constructed for the DC Clean Rivers Project. The DC Clean Rivers Project is estimated to be completed by 2025 and will cost approximately $2.6 billion. The Purpose of this project is to reduce the amount of combined sewage overflow into the Potomac and Anacostia rivers by 96 percent! The Blue Plains tunnel will perform by redirecting the sewage overflow to the DC Advanced Wastewater Treatment Plant. Here, the overflow will be treated before being released into the Potomac River.
The machine used to accomplish this task was a Tunnel Boring Machine (TBM) called “Lady Bird”. Lady Bird was an Earth Pressure Balance Shield machine (EPB) and weighed over 1300 tons. She measured 440 ft. in length and had a 27 ft. diameter cutter head. Lady Bird was manufactured by Herrenknecht and cost $30 million. By the end of the project Lady Bird had excavated over 13.5 million cubic feet of soil and achieved a top speed of 125 feet per day. She arrived at her destination on time and with-in millimeters of her desired final coordinates.
What results did you achieve on the project(s), and what impact did they have on the company?
I was trained to be a field engineer or the ‘Heading Engineer’ on Lady Bird. The Heading is where the tunnel lining is assembled. In particular, I was trained to oversee and facilitate the operations in the Heading. This included the Grout Control System (GCS). This system controlled the amount of grout injected into the annular void created by the difference in the size of the cutter-head diameter and the diameter of the tunnel lining. The volume of grout injected into this void is critical in preventing settlement on the surface. If the deviation between the annular void volume and the volume grouted reached a certain value, a safety measure would temporarily shut down the TBM. As the speed of the TBM changed, the flow rates of the grout pumps had to be consistently modified in order to maintain desired pressures via the GCS. Additionally, I was responsible for measuring the clearance between the Tail Skin Shield and the tunnel lining. These measurements were taken mid-way of every advancement phase. I immediately reported these measurements to the TBM operator in order to avoid Iron bound conditions with the Thrust cylinders. These measurements were important because it allowed the TBM operator to visualize a snap shot of the location of the articulation cylinders relative to the previous ring-build and, if need be, the operator could adjust the direction of the TBM drive.
As the Heading Engineer, I was also in charge of facilitating quality control of the Tunnel Segments. The Tunnel Segments are the precast concrete slabs that make up the tunnel lining. I inspected each segment and ensured that the gaskets were installed adequately to prevent tunnel leakage. If a stone was found to be damaged to the point of risking gasket functionality, the stone would be sent back to the drop shaft and replaced. When the VMT Navigational System selected a new ring-build I was responsible for double checking the Ring Build Matrix to ensure that the chosen ring build was allowed. Certain sequences of ring-builds are prohibited due to the possibility of aligning longitudinal joints, creating locations of stress concentration. At the end of each shift, I was also responsible for creating a daily production report which was sent to all the senior personal at Traylor Bros., Inc.
My performance, while fulfilling my responsibilities, had a positive effect on Traylor Bros., Inc. I minimized down time by inspecting the tunnel segments before it was time to build the next ring, allotting us time to replace the stone if needed. I also maintained attention to the Grout Control System in order to avoid a deviation shut down of the TBM. I referred to the Ring Build Matrix before each ring-build and caught two prohibited ring-builds. I then notified the TBM operator and we collaborated on choosing a similar but allowable ring-build. The daily reports I produced informed the senior staff details on productivity on a day to day basis and informed the other engineers of potential problems. Overall, my results contributed to smooth mining operations and to the timely construction of the Blue Plains Tunnel.
What real-life technical or business skills did you learn during the internship?
During my internship I learned several technical/business skills. My first objective as an intern I was required to learn the basics of the Grout Control System used on the TBM. The control screen I was responsible for monitoring contained several sensor outputs and I was responsible for learning the meaning of each one. I was expected to be able to change the flowrates of the Grout and Accelerator pumps in order to compensate for the change in mining speed of the TBM. Additionally, I was accountable for achieving minimum grout pressure and volume requirements at the end of each advancement phase.
Another technical skill I mastered during my internship was proficient reading of the Ring build Matrix and Ring Build Diagrams. The Ring Build Diagram provided visualization of the general direction any particular ring-build would drive the tunnel in. The Ring Build Matrix was a collection of all the possible ring builds. It was dependent on the previous ring build and the anticipated ring build. As the Heading Engineer I was responsible for checking the Ring Build Matrix before each subsequent ring was built and double checking for possible cross joints. If a certain ring build was selected by the VMT system that was designated as prohibited by the Ring Build Matrix I was responsible for notifying the TBM operator. I would then refer to the Ring Build Diagram and collaborate with the TBM operator to choose a similar ring build that was allowed by the Ring Build Matrix.
What did you learn in this internship that will affect your life in a positive way?
While working on the Blue Plains Tunnel, I learned several life impacting lessons. Foremost, I learned the importance of teamwork. Teamwork had such a great influence on the completion of this project. The TBM crew exhibited teamwork by assigning specific tasks to each other and always looking out for one another. If a teammate did not show up to work, the team leaders would step in and share the workloads in order to get the job done safely.
I also learned the importance of effective communication. Communication was very crucial in reducing potential dangers on this job site. During mining operations on the TBM, we would have large mechanical components and hydraulic cylinders operating in the Heading. These hydraulic and pneumatic systems were operated by personnel so there had to exist effective communication between team members in order to eliminate avoidable injuries.
Additionally, I learned of the importance of mutual respect. When working long hours on projects a crew easily becomes like a family unit. Depending on the urgency of dead-lines, occasionally we spend more time at work than we do with our families and this could place a heavy mental burden on us. By maintaining respect for one another we can minimize unnecessary disputes and arguments. These types of confrontations distract us from the job at hand and could potentially lead us to having an accident at work.
Where do you think technology will make the biggest impact in construction in the next few years, and how will it do that?
With the advancement of technology, I believe in the next few years we will see an increase in Sustainable Construction. For example, ‘Smart’ Buildings will be strategically equipped with hundreds or even thousands of sensors. These sensors will provide designers data throughout the buildings’ life cycle. These sensors will increase knowledge and awareness of the external and internal dynamic loads experienced by the structure. Aspects that will benefit from this collection of data could include; structural health, vibrational effects and energy management.
By equipping accelerometers on a structure, we will be able to analyze the vibrational effects due to occupant motion, seismic activity or external forces such as wind. We will gain a better understanding on how to mitigate these effects in order to increase the structural life span. By placing energy measuring sensors we will also be able to see how certain structural designs perform in energy retention and waste. This will allow us to make considerable changes to future structural designs. This concept will increase the overall performance of the structure, increase the life cycles and potentially save us a lot of money all while keeping the environmental effects in mind.