In Rockhampton, the shallow geology is dominated by Quaternary alluvial deposits from the Fitzroy River floodplain, often overlying weathered Tertiary basalt and sedimentary rock. These conditions make the Ménard pressuremeter test (PMT) particularly useful for measuring in-situ deformation modulus and limit pressure. Unlike SPT or CPT, the PMT applies a radial load directly to the borehole wall, giving engineers a direct reading of soil stiffness and bearing capacity. This is critical when designing foundations for the soft clays and loose sands common near the city centre. The equipment is lowered into a pre-drilled hole and expanded in controlled increments, recording pressure and volume changes. Results are interpreted using the Ménard formula to derive Em (pressuremeter modulus) and Pl (limit pressure). For deeper profiles, combining PMT with a veleta de campo helps assess undrained shear strength in cohesive layers.
The PMT delivers direct measurement of soil stiffness at depth, essential for foundation design in Rockhampton's variable alluvial deposits.
Scope of work
Area-specific notes
A recent commercial development on Quay Street encountered soft estuarine clay more than 8 m thick. Without a Ménard pressuremeter test (PMT), the design assumed higher stiffness from SPT correlations alone. The PMT revealed Em values below 3 MPa in the upper 6 m, prompting a redesign from shallow footings to driven piles. Ignoring the PMT data would have led to excessive differential settlement. In Rockhampton, where the water table sits within 2 m of the surface near the river, the PMT gives realistic creep behaviour under sustained load. For sites on the Bruce Highway corridor, the test helps verify bearing layers for bridge abutments and retaining walls.
Standards used
AS 1726:2017 Geotechnical site investigations, AS 1289 Standard test method for prebored pressuremeter testing in soils, BS 1377-9:1990 Methods for in-situ tests (pressuremeter)
Linked services
Standard PMT for Shallow Foundations
Boreholes to 15 m depth with PMT measurements every 1.5 m. Suitable for residential slabs, light commercial buildings, and road embankments on Rockhampton's alluvial soils. Reporting includes Em and Pl profiles plus estimated bearing capacity per AS 4678.
Deep PMT for Pile Design
Boreholes to 25 m depth with PMT every 1.0 m. Designed for driven piles, bored piles, and secant pile walls. Results provide lateral modulus and end-bearing parameters for axial load capacity. Includes comparison with SPT and CPT data where available.
Typical parameters
FAQ
What is the main advantage of the Ménard pressuremeter test over SPT in Rockhampton?
The PMT measures soil stiffness (Em) and limit pressure (Pl) directly in the ground, unlike SPT which gives only a blow count. In Rockhampton's soft alluvial clays, the PMT provides a more reliable deformation modulus for settlement analysis, reducing the uncertainty from SPT correlations. It also works well in gravelly layers where SPT may give erratic results.
How much does a Ménard pressuremeter test cost in Rockhampton?
The typical cost for a complete PMT borehole (10 test levels, including mobilisation within Rockhampton) ranges between AU$1.660 and AU$1.790. This includes borehole drilling, probe calibration, data reduction, and a summary report. Additional test levels or deeper holes will increase the price.
Can the PMT be used in the basalt bedrock found west of Rockhampton?
Yes, but with limitations. In weathered basalt or fractured rock, the PMT can measure deformability (Em up to 200 MPa) if the rock is not too hard. For fresh basalt, the pressure required exceeds the probe capacity, and other methods like plate load tests or geophysical surveys are preferred. The PMT works best in soils and soft rock.