Wardell Armstrong – HoleBASE SI & Extension for AutoCAD Civil 3D

Integrated 3D landform modelling was at the heart of successful collaboration between Wardell Armstrong and site owner Lands Improvement on a residential development in Staffordshire.

When consultant Wardell Armstrong was brought in to provide geotechnical expertise as part of the team designing the landform for a new development of 250 homes at Apedale Road, Newcastle-under-Lyme, it was confronted with a number of challenges.

“The site, which includes a former quarry, has a variable topography with steep and unrestored slopes in the quarry area, variable ground conditions, contamination, ground gas risk, areas of potential archaeological interest and Great Crested Newts,” confirms Wardell Armstrong Technical Director Chris Smith. “The landform design had to address these constraints, while delivering a solution that could be built cost-effectively.”

Wardell Armstrong carried out a desk study and site investigation, inputting borehole and laboratory data, along with historical borehole information, to HoleBASE SI for analysis and interpretation. Data was then exported to AutoCAD Civils 3D, using the HoleBASE SI Extension, to create a data-rich ground model.

“Using HoleBASE SI with AutoCAD Civils 3D greatly improved our efficiency to analyse data quickly and thoroughly,” Smith says. “The ability to import third party AGS data was also a big help because it allowed us to build geological models rapidly. These models could then be incorporated with those developed by other members of the design team.”

Wardell Armstrong, which also acted as landscape architect and ecological consultant, worked with the design team’s infrastructure engineers to design site reclamation and earthworks, along with working and development platforms.

Modelling identified pockets of buried topsoil, which, when plotted against ground gas concentrations over the site, were found to be responsible for the areas of elevated ground gas levels.

“The model enabled us to mitigate the risk of differential settlement in the variable fill materials and the effects of the steep and high quarry walls, while maximising the area of development land,” Smith explains.

“We were also able to predict the volumes of various materials and then to optimise the final landform design to balance the earthworks, so there was no need to import material or dispose of it off-site,” he says. “For instance, we could ensure there was enough topsoil for gardens and soft landscaping, which could have been very expensive to import.”

An added complication was the risk of Roman remains being uncovered during earthworks. “This risk was mapped and overlaid in the 3D model, so that we could modify the earthworks design and minimise the impact on the archaeology for sourcing materials, in respect to various development options,” Smith says.

He adds that it was also easy to generate cross sections, calculate volumes and for the project quantity surveyor to cost different design options, resulting in a well thought out final design that could be delivered much faster than with a conventional approach.

The landform design was presented to the client using rendered images and fly-throughs of the model.

“This was a real bonus, as the client could visualise the design and could have far more input in the design process,” Smith says. “We held collaborative workshops using video conferencing, making real-time changes to the model to explore different options. For example, we could change road alignments and see how this would affect the landform design and the construction cost.”

Images, cross sections and fly-throughs of the design were also used in the planning process to help key stakeholders understand the client’s vision for the project.

“Using HoleBASE SI and AutoCAD Civils 3D brought immediate and obvious benefits to this project. Collaboration was improved, as the software enabled team members working in different offices to input in real time and gave them remote access to all the project data,” Smith says. “From our point of view, we were able to produce a ‘BIM compliant’ output, allowing our geological data to be combined with models of other designers in one model.

“Ultimately, the client had a viable landform design that could be demonstrated to comply with the project requirements, including protecting sensitive ecological areas and archaeology, as well as meeting drainage, highways adoption and geotechnical and contaminated land issues.  The 3D model also enabled various landforms and development options to be evaluated as part of a cost benefit assessment”.

“This resulted in a more resilient final landform that we, the client and wider design team could have confidence in being deliverable. The workflows also reduced our risk, as we were able to ensure that the designed output would work.”