Description
| Sydney Metro City & Southwest – Geotechnical Data Report for TSE Stage 2 investigations – March 2017 |
This report presents the factual results of the investigation for the proposed Sydney Metro City and Southwest Metro Corridor.
The purpose of the geotechnical investigation was to infill data gaps between Chatswood and Sydenham to supplement the 2015
geotechnical investigations by Golder-Douglas and a new phase of investigation for the proposed upgrade of
the Bankstown Line between Sydenham and Bankstown.
This Geotechnical Data Report presents the factual results of the infill investigations for the proposed Tunnel
and Station Excavation (TSE) Works package between Chatswood and Sydenham. The investigations in this
report were carried out along the tunnel alignment with a focus on the proposed dive structures at Chatswood
and Sydenham, the proposed stations at Crows Nest, Victoria Cross, Barangaroo, Martin Place, Pitt Street,
Central Station and Waterloo, and proposed shafts in Artarmon and at Blues Point. The investigation was
carried out during the design development stage of the project. As the investigation progressed, changes to
the scope were made to respond to the ground conditions encountered and to respond to the design changes,
including adjustments to the proposed station box and track levels.
This revision of the report includes laboratory testing previously not reported. The investigations comprised
boreholes, cone penetration tests and excavations by non-destructive techniques. A total of forty five
boreholes were drilled to depths below the existing ground surface of between 0.3 m and about 48 m. Eight
boreholes were drilled at inclination with the intention of intersecting expected dykes or faults, with drilled
lengths up to 100 m. Six shallow (3 m deep) large diameter boreholes were completed at the dive structures
to obtain samples for laboratory earthworks testing.
In situ testing was carried out in boreholes including packer (water pressure) tests at twenty locations, in situ
stress measurements at ten locations and downhole imaging of the borehole walls at twenty five locations.
Typically two or three packer tests were carried out in each designated borehole. In two boreholes at Central
Station, magnetic gradiometer testing was carried out to assess the depth of reinforced concrete piles below
the platform that support the roof canopy.
Soil and rock samples recovered from boreholes were dispatched to laboratories for testing designed to
classify the materials, and to assess their strength, durability and deformation characteristics. The testing
included index tests, clay mineralogy determination and various triaxial tests on soils and unconfined
compressive strength tests with modulus assessment, shear box and petrographic analyses on rocks.
Standpipes (monitoring wells) were installed in twenty boreholes as well as multi-level vibrating wire
piezometer (VWP) for the purpose of groundwater level monitoring, sampling and testing in three boreholes.
Cone penetration tests were carried out at the proposed location of Waterloo station and at Alexandria, to
develop a profile of the soil conditions and assess the depth to rock. A total of thirteen tests were performed
to depths of up to about 20 m.
Excavations were made using non-destructive digging techniques with the intention of exposing the footings
of designated platform retaining walls and the roof of tunnels at Central Station and at Waterloo Church.
Similar excavations are planned to expose the footings of a building at Waterloo.
Concurrent with the geotechnical investigation, samples were recovered for contamination testing. The results
of the contamination testing are presented separately in a Contamination Assessment Report (CAR).
