Micropiles used in A-frame to stabilise landslide damaged roads in Queensland, Australia

This paper details the investigation, design, construction, and monitoring processes performed in the employment of micropile to restore failed sections of roads within the jurisdiction of the state and councils in Queensland, Australia using micropiles in an A-frame arrangement. Some of the roads that have been restored include the Gatton-Cliffton Road, in Southern Queensland, the Kin-Kin Road, on the Sunshine Coast Hinterland, and Dalrymple Road, at Eungella, near Mackay. The restored site on Dalrymple Road comprised a 140 m long section where unstable upper soils of colluvial origin was up to 7 m thick. The affected and restored sections of Gatton-Cliffton and Kin-Kin Roads were 30 and 40 m, respectively. For managing the type of failures encountered in these road assets, Queensland Transport and Main Roads usually adopt large diameter piles with or without tieback as a default solution. Concerns regarding the inability of micropiles to resist large forces and the risk posed to the piles in the event of loss of soil material downslope on the passive side have mitigated on their use for addressing such failures. These drawbacks have been overcome through rigorous investigation, design, and construction processes on these projects, thereby making micropiles potential remedial option for consideration in the future.