Jessica Yu

Graduate Geotechnical Engineer

I graduated with a BE in Civil Engineering from the University of NSW and joined SMEC as a graduate in February 2002. I have previously completed 3 summers of Industrial Training at SMEC. During my time here as a student I was involved in concept designs, tender designs and detailed designs for various projects. I realised that working with SMEC would give me plenty of opportunities to work on large scale projects both in Australia and overseas. The work was intense and challenging, and the other engineers were always happy to help me out. I decided that I want to work as a geotechnical engineer, and when SMEC offered me a position with the geotechnical group in the Sydney, I gladly accepted.

Since joining SMEC as a graduate I have been involved in numerous projects, notably tender design for Lane Cove Tunnel and detailed design for Kallang Expressway in Singapore. I have spent most of my time here on the Kallang project, and below is a brief description of my main responsibilities.

The project consisted of the design and construction of 1.5 km of cut and cover tunnel and 4 slip roads in Singapore. I was on the temporary works team which was responsible for designing the retaining wall system to allow excavation to take place. Initially, I was working on the geological long sections, then I assisted in the preparation of the geotechnical interpretative report, which involved interpreting field testing and lab testing data to come up with the soil parameters to be used in design. One of the most interesting and challenging part was when I was given the responsibility to coordinate the design of temporary works for a 120 m section of the cut and cover tunnel along with a section of the slip road which was to be constructed concurrently with the main tunnel. This involved designing the braced sheetpile wall system and producing a design report for submission to the client.

Initially I had to determine the critical soil models for design, and this was done by reviewing the geological long section and site investigation information. The tunnel cross sections corresponding to these critical soil models were obtained from the Structural engineer. Together, appropriate construction sequences were discussed, bearing in mind the constructability of the sequence, the spacing of the struts for a safe design, and ensuring the sequences were compatible with adjacent tunnel sections.

Based on the systems we used for other tunnel sections, I came up with a preliminary retaining wall system for this section, and got approval from the client to proceed with detailed design. Base heave checks were an important component in coming up with the preliminary design because the toe levels of the sheetpile wall as well as the necessity of using a jet grout layer below the base of excavation were governed mainly by base heave stability. It was our responsibility to perform these checks before detailed design could proceed.

Detailed design involved me delegating different sections for other engineers on the team to analyse, so that the design submission deadline could be met. We used a finite element analysis program to calculate the forces acting on the walls and struts and the deflection of the system. During this process there was frequent interaction with structural engineers to optimise wall and strut sizes and spacing. The final design was achieved after numerous iterations.

On completion of the design, a design report outlining design methodology and analyses results was produced and sent to the client in Singapore.

Detailed design of this project is nearing completion and it has definitely provided me with a lot of challenges since I joined the company. I was exposed to different areas of geotechnical work and have gained valuable experience as a result.