Pacific Highway Underpass - Gold Coast - City of Gold Coast

Project Summary

Queensland’s Gold Coast City Council (GCCC) is reaping the rewards of its investment in 4D Model (later renamed 12d Model) software.

The GCCC has put the program to work as a civil design and survey tool, taking in a range of projects including the detailed design of intersections and large earthwork projects such as refuse sites.

The Challenge

The latest road project to be undertaken by the GCCC was an underpass interchange designed as part of the redevelopment of the Pacific Highway. The extensive task was facilitated by the use of 4D Model and the template modifiers which are a standard part of the roads module.

The Solution

Template modifiers provide control over each point of a traditional template and form a simple bridge between traditional template methods and the string design techniques that are essential for detailed road design and reconstruction work.

"The design, which involved lowering the intersection by a depth of four to five metres, was competed using template modifiers in 4D Model," said Phillip Weightman, Design Drafter, Gold Coast City Council. The design called for a bridge underpass, a large intersection and two roundabouts in place of a notorious at-grade intersection. This work involved multi-lane roads with median strips, right and left turn lanes, and acceleration and deceleration lanes.

"The majority of the roundabout and intersection design was achieved using 4D’s template modifiers, with little or no adjustments required for the final design strings," said Mr Weightman.

4D reduces the number of steps that a designer would normally take to complete an aspect of the design. Design adjustments can be easily made graphically and volumes recalculated instantaneously.

Kerb Return
GCCC designers also found 4D Model’s kerb return very useful. "For example, we used 4D to create three centred return strings between two straights on each of the four corners of the intersection," said Mr Taynton.

"4D profiled the kerb string in relation to both incoming grades."

4D Model allowed operators to then easily alter the kerb design to allow for real-world scenarios such as services or driveways.

"The design advantage of 4D Model is that you can link all facets of design such as gradings of cross streets and kerb returns with the main peg line design," said Mr Taynton. "Instead of having to regrade kerb returns manually, they are updated automatically because everything is dynamically linked. The package is ideal because it provides that versatility." Both men believe that 4D Model offers road designers considerable time-saving as operators can graphically see any changes they make.

"I can complete a grading or an alignment alteration, invoke a quick re-calculation and see the design contours update on-screen," said Mr Taynton. "That allows me to quickly see the results of my work and decide if that is what I wanted to achieve."

"From a designer’s, engineer’s and planner’s aspect 4D has proven itself to be the ideal package for preliminary to final detailed designs," said Mr Taynton.

Flood Modelling and Future Planning
The speed and flexibility of 4D Model also allowed the Council to quickly and easily check a range of "what if" scenarios for road design and flood modelling. "It will allow us to experiment with various flood scenarios using rainfall and water resources data along with photogrammetry, imported into 4D Model," said Mr Weightman.

“We then add various Z heights for different flood events at known cross sections; these are put into 4D Model and a surface created. This gives us a surface model of the flooded areas for a certain flood event.

The Result

"4D Model can also drape property boundaries on to the terrain to show property owners if a project will encroach into boundaries. They get a much better idea seeing a plot of a perspective view, rather than a cross section."

Another project carried out using 4D Model was the Coomera Charrett where a group of consultants, town planners and engineers from civil and environmental backgrounds spent an intense week looking at planning for the rapid growth of the area. "We produced slope analysis plans which allowed the planners to immediately look at an area and decide if it was suitable for a subdivision or a road," said Mr Weightman.

"We produced about 40 proposed alignments in about a week using two operators."