GEOINVENTIONS CASE STUDY Burnett Highway, Mt Morgan … · GEOINVENTIONS CASE STUDY Burnett...
Transcript of GEOINVENTIONS CASE STUDY Burnett Highway, Mt Morgan … · GEOINVENTIONS CASE STUDY Burnett...
INVENTIONSC O N S U L T I N G S E R V I C E S
G E O I N V E N T I O N S C A S E S T U D Y
B u r n e t t H i g h w a y , M t M o r g a n R a n g e R o a d F l o o d R e s t o r a t i o n Wo r k s
Project: Burnett Highway, Mt Morgan Range Road Flood Restoration Works
PROJECT DETAILS
Client: Department of Transport and Main Roads
Contractor: RoadTek
Location: Queensland, Australia
Design of Reinforced Earth Embankments
Design Completion Date: January/February 2014
Construction Commencement Date: February 2014
Construction Completion Date: May 2014
The Burnett Highway (Road 41F) is located approximately
20km south west of Rockhampton. The flood restoration
area is situated in the Mount Morgan Range and is
characterised by intervening ridges and valleys and the
highway winds through these with numerous hairpin bends.
The original Mt Morgan Range Road was constructed in
1934/35 to engineering standards current at the time. The
road was later widened to its current width using won
materials from the up-slope cut and placed on the down-
slope batters. Due to steep batters, the degree of
compaction of the placed fill was questionable.
There was a major bush fire on the range in December
2012, and vegetation had not re-established prior to the
heavy rains during Cyclone Oswald in late January 2013
where 810mm of rain fell within 3 days.
Following intense rainfall associated with Cyclone Oswald
which was assessed to be in the order of 200 to 300 ARI
event, numerous failures occurred on both the up-slope
and down-slope batters as well as on the carriageway. Of
the documented failures, eight (8) were significant and
were classified as major failures. As a means of managing
the risks associated with the observed failures and potential
further failures the range was closed to traffic to ensure
safety of road users and to enable repairs. Steep batters,
poor compaction and saturation of the questionable fill
were considered the major factors that contributed to the
failures. The observations during the removal of the failed
materials supported the unengineered (to current standards)
status of the materials on the down-slope shoulder/verge
and on parts of the carriageway.
Photo 1: Failure of Major Fill Area
Photo 2: Removal of Failed Materials
Photo 3: Site Investigations
Based on options analysis carried out by the Department of
Transport and Main Roads (DTMR) engineers, the reinforced
embankment remedial option was adopted as the optimal
solution for remediating the eight (8) major failed sites. Several
geosynthetic suppliers were requested by DTMR to submit
conforming designs using 60kN/m uniaxial strength geogrid
that would meet functional and long-term performance
criteria in line with the Departmental Geotechnical Design
Standard (GDS) as well as provide facing capable of
withstanding bushfires characteristic of the range.
Global Synthetics provided a preliminary design for the
supply of their proprietary Terralink® reinforced embankment
system and provided fire resistance testing of their product for
evaluation by Roadtek and DTMR. Based on the information
provided, this system was selected as the preferred solution.
Global Synthetics engaged Geoinventions Consulting Services
(GCS) to provide a full design report, drawings and RPEQ
certification for the eight reinforced earth embankments.
GCS was requested to design the Terralink® reinforced earth
embankments in line with the DTMR Geotechnical Design
Standard which refers to BS8006. Several sections had to be
analyzed using SLOPE/W. All structures were analyzed for
external, internal and global stability. A design load of 20kPa
was provided as the surcharge loading for the highway.
Furthermore, it was requested by Roadtek that locally sourced
crusher dust be adopted as the reinforced fill (see photo 5).
GCS requested samples of the crusher dust material which
were sent for shear box testing. The shear box test results
indicated friction angles in excess of 45 degrees.
Terralink® Panels are 540mm in height and come with
preformed brackets which allow a 65 degree face. Acegrid
GG80 and GG100 polyester geogrids were adopted in
the GCS design to provide embankment stability. Geogrid
reinforcement lengths were approximately the same length
as the height of the embankment. To prevent future bushfire
damage, the welded mesh facing was shotcreted as shown
in photo.
Photo 4: Placing Terralink® Panels & Geogrid
Photo 5: Placing Facing Rock & Crusher Dust
Photo 6: Completed Terralink® Facing
Minimal field investigations were carried out however
these investigations revealed that the failed materials
consisted of fill of variable consistency and thickness
overlying residual soil and variably weathered rock
which is predominantly basaltic. GCS requested that
further investigations be conducted on site in the form of
Dynamic Cone Penetrometer (DCP) tests and Test Pits (TP)
as a means of confirming the parameters adopted in the
foundation design.
GCS completed all the designs, reports and drawings within
the desired time frame and provided an experienced RPEQ
engineer onsite to witness the construction and sign off the
completed works.
The completed works have experienced one cycle of
intense rainfall associated with Cyclone Marcia. No adverse
performance concerns have been raised and the reinforced
embankments have been performing satisfactorily.
O F F I C E 0 7 3 1 8 8 9 0 3 8 | W W W . G E O I N V E N T I O N S . C O M . A U
d y n a m i c e n g i n e e r i n g t h r o u g h i n n o v a t i o n
Photo 7: Completed structure
Photo 8: Application of Shotcrete