Wurrungwuri - Engineering

Underpinning the visual and cultural aspects of the sculpture, the design and construction of the Wurrungwuri Sculptures required an extensive engineering exercise, in close collaboration with both the artist and the construction team, which pushed the boundaries of 3D modelling and documentation, the accuracy in fabrication of large stone elements and the skill and ingenuity required for installation.

The 'Wave' sculpture

This is the largest part of the work and comprises three 'waves', formed from closely fitting sandstone blocks. Wave A2, sits on and is supported by the larger wave A1, and a smaller wave, designated A4 sits on the ground further down the slope. The visual impression of these forms is that they have been thrust out of the natural landscape, but a closer look reveals how they have been made and assembled by humans.

The concept for this sculpture was presented by the artist in the form of a 1:50 scale clay model. The engineering challenge was then to convert this to a system whereby such a shape could be fabricated at full scale, to the shape intended by the artist, and assembled in practice on site.

Conceptually, the sculpture is divided into a series of closely-fitting sandstone blocks meeting adjacent pieces on contact planes. The pieces are fixed to each other via dry joints, clamped together by bolts in tension. Each bolt clamps together two stones, and is perpendicular to the contact face, and anchored into recesses in the opposite faces. Hence all stones are bolted into a complete assembly, which is supported by concrete strip and slab foundations onto the rock beneath the site. Grout and anchor details restrain the ends of the stone assembly.

The geometry is irregular because there are folds and changes of surface direction throughout. No two stones are the same. Hence a special process was needed to analyse and document the geometry so it could be fabricated and assembled. This is summarised as follows:

What is seen when viewing the work are the naturally occurring or rough-worked surfaces of the top, sides and soffit, which belie the precise nature of the assembly geometry. While it was originally intended that visible bolts be concealed beneath the surface by matching grout, the artist decided to leave these mostly exposed, which provides a clue to the engineering within.

The 'Quartz' Sculpture

This is a smoothly curved form, created with a surface of more than 16,000 quartz pebbles, mostly about 100 mm diameter. The mounting of the pebbles uses a technique developed by the artist, in which each stone is drilled through, and threaded onto a stainless steel cable. The cable spirals around the form from bottom to top, and is tied back to a stainless steel frame at each stone.

As with the 'wave' structure, the quartz form was developed from a clay model by Booth, and scanned into a 3d file. The inner frame is derived from a series of vertical slices through the form at 300mm centres, each realized as a stainless steel tube. Horizontals and bracing members then completed the frame, which was covered by a stainless mesh onto which the pebble threading cables were tied. The model was used to make shop drawings for fabrication of each frame. There is a concrete foundation to which each frame member is bolted, with a pit for access if needed.

Inside, there are boxes in which small bats which enter the sculpture though a slot at high level can roost. There is already evidence that some have taken up residence.