CAPLab Terms & Conditions

Intended use

CAPLab is intended to assist a pavement designer with selecting the appropriate geogrid, geotextile, and pavement section thickness, based on the referenced engineering standards, testing, and research. The suggested pavement layouts generated by CAPLab are intended as a guide only. You must use appropriate judgement in applying the CAPLab results to the specific project, and the CAPLab results must be checked and approved by a suitably qualified pavement engineer before construction.

CAPLab is intended for use in the New Zealand environment only. CAPLab must not be used for projects located outside of New Zealand.

CAPLab is for the sole use of the person who registered with Cirtex Industries Limited (‘Cirtex’) and to whom CAPLab was directly supplied by Cirtex. Every user of CAPLab must be registered with Cirtex. Use of CAPLab by anyone who has not registered with Cirtex is not authorised.


Design methodologies

The following is an overview of the two design methodologies used by CAPLab; for further information and copies of the research papers and source data relating to the design methodologies, please contact Cirtex on 0800 247 839.

SIL & Fig 8.4 Method. This method uses a subgrade improvement layer generated from empirical data from the manufacturer Naue GmbH &Co (‘Naue’) based on the proven performance of the Secugrid and Combigrid range of geogrids to improve the modulus of the subgrade from the input figure to E = 80 MPA. From this improved figure the pavement depth is calculated using the formula from AustRoads Figure 8.4 chart (or Fig 8.5 from Austroads AP-T36/06 for ESA ≤ 105) to give the appropriate pavement depth. A conversion of E = 10*CBR is used. A customised version of CAPLab is available with other conversion formula if required.

Perkins 2014 Fig 7.4 Method. This method is based on the work of Dr Steve Perkins as outlined in his paper “Modification of Austroads Empirical Design Charts for Paved Roads Reinforced with a NAUE Geogrid.” It is based on extensive finite element modelling and is calibrated to the performance properties of Secugrid and Combigrid, and the modified AustRoads charts as presented in the abovementioned paper.



CAPLab applies methodologies that are intended to provide a sufficient reinforced pavement depth to limit surface rutting to an acceptable level over the design life of the pavement. However, CAPLab is a tool and is not a substitute for professional judgement. Many factors on site and during construction will impact the final result of the project.

To the maximum extent permitted by law, Cirtex, Naue, and their associated persons do not warrant that CAPLab will meet your requirements and do not provide any warranties of any kind, including as to fitness for a particular purpose, in respect of either CAPLab or any finished pavement surface. To the maximum extent permitted by law, Cirtex, Naue, and their associated persons disclaim all liability, whether in contract or tort, for any loss or damage of any kind arising directly or indirectly from your use of CAPLab. Cirtex, Naue, and their associated persons are not responsible for any consequence arising out of the unauthorised use of CAPLab, including any loss or damage arising from that unauthorised use.

Pavement design methodologies and practices and relevant codes and regulations may change over time. Cirtex is under no obligation to update or re-issue CAPLab to reflect any such changes or to inform you of any such changes.