Specialist Geotechnical Assessments
Specialised geotechnical assessments involve detailed investigations and analyses conducted by our geotechnical engineers to evaluate specific subsurface conditions for particular projects, ensuring the safety and effectiveness of construction, design, and excavation activities. These assessments are typically required for complex or sensitive projects where conventional soil testing may not be sufficient. Atlas Engineering and Technology Group (AETG) aims to assess factors such as soil behaviour under various conditions, stability of slopes, foundation design, groundwater conditions, and the effects of seismic activity.
What Specialised Assessments Does AETG Provide?
Site-Specific Geotechnical Investigations: Involves detailed soil testing and geophysical surveys to assess the unique properties of a site. This includes determining soil composition, strength, settlement characteristics, and bearing capacity. Common tests include borehole drilling, Cone Penetration Tests (CPT), Standard Penetration Tests (SPT), Dynamic Cone Penetrometer (DCP) and various laboratory soil testing in our NATA accredited laboratory for parameters like shear strength, consolidation, and permeability.
Seismic Site Classification and Analysis: This assessment evaluates the site's susceptibility to seismic hazards, including ground shaking, liquefaction potential, and fault displacement. Our geotechnical engineers analyse soil stiffness, shear wave velocity, and other parameters to determine the site’s seismic classification. This helps in designing foundations and structures that are resilient to seismic activity.
Slope Stability Analysis: Slope stability assessments are performed to evaluate the safety of embankments, hillsides, and natural slopes under the influence of external factors such as rainfall, seismic forces, and construction activities. Common tools used in these assessments include the Limit Equilibrium Method (LEM), Finite Element Analysis (FEM), and probabilistic methods to determine the Factor of Safety (FoS) and evaluate potential failure mechanisms such as rotational failure, translational failure, or toppling.
Foundation Design and Settlement Analysis: Specialised assessments of the type, depth, and design of foundations are crucial for sites with variable or problematic soil conditions (e.g., expansive clays, loose sands, or weak bedrock). The assessment evaluates settlement potential (both immediate and consolidation settlements), bearing capacity, and the appropriateness of different foundation types (shallow or deep foundations). Techniques like pile load testing, pressure meter testing, and plate load testing are commonly used to assess the behaviour of the soil under load.
Geotechnical Aspects of Groundwater and Dewatering: Groundwater conditions, including the depth of the water table and potential for seepage, are assessed to determine their impact on construction. This is particularly important for deep excavations, tunnels, or underwater foundations. Dewatering systems may be designed based on this assessment to control groundwater levels during construction, ensuring the stability of excavations and minimising the risk of soil erosion or liquefaction.
Geohazard Assessments: Geohazard risk assessments involve the study of potential natural hazards such as landslides, soil erosion, flooding, and volcanic activity that could impact a site. These assessments help identify potential geotechnical hazards in the area, allowing engineers to incorporate risk mitigation strategies such as slope stabilisation, flood control, or earth-retaining structures.
Expansive Soil and Swelling Clay Analysis: Expansive soils, especially clays, can shrink when dry and swell when wet, leading to significant foundation movement. This type of assessment evaluates the potential for soil swelling, shrinkage, and cracking. Special tests like the Atterberg limits test, free swell index, and plasticity index help identify the shrink-swell characteristics of the soil.
Contaminated Land and Environmental Geotechnical Assessments: For sites with potential contamination (e.g., from industrial activities, landfills, or hazardous materials), geotechnical investigations are carried out to evaluate the impact of contaminants on soil behaviour and the suitability for construction. Soil sampling, chemical analysis, and groundwater testing are conducted to assess potential risks and inform remediation strategies.
Pavement Design and Soil-Structure Interaction: In road and pavement design, specialized geotechnical assessments focus on soil stiffness, traffic load, and the interaction between soil and pavement materials. Tests like the Dynamic Cone Penetrometer (DCP) and Californian Bearing Ratio (CBR) are used to evaluate the strength and resilience of the subgrade for local carriageways, highway or airport runway design.
Rock Strength Investigations: Rock strength is critical in geotechnical engineering to assess the strength properties of rock materials, which are essential for designing stable structures like foundations, tunnels, dams, and slopes. The strength of rock plays a key role in determining how well it can withstand applied loads, weathering, and other forces without failing. These investigations involve laboratory testing, in-situ testing, and the evaluation of rock properties to ensure the safe and effective design of structures. Methods used to determine rock strength include Uniaxial Compressive Strength (UCS) tests, point load testing and triaxial shear strength testing to obtain strength characteristics.
Why Choose AETG for Specialist Geotechnical Assessments?
Special geotechnical investigations are essential for understanding complex subsurface conditions and ensuring the safe and efficient design of foundations, slopes, pavements, and structures. AETG uses advanced testing methods, numerical analysis, and site-specific evaluations so our engineers can mitigate risks, prevent failures, and implement design solutions that are tailored to the unique challenges posed by the soil and environmental conditions of a site. Testing methods are performed in our NATA accredited laboratory and in accordance with Australian Standards (AS1289, AS1726 and AS4648) procedures.
Successfully Completed Jobs by AETG to Date
✔ Proposed Landslip Remediation - Guy Pl, Emu Plains NSW
The Geotechnical Investigation Report for Guy Place, Emu Heights NSW outlines a comprehensive assessment conducted by AETG in response to a significant slope subsidence event near a residential dwelling. The report identifies that the site is underlain primarily by silty clay soils with highly dispersive properties (Emerson Class 1), contributing to instability. Field investigations included borehole drilling, DCP testing, and laboratory analyses of soil properties such as plasticity and particle size distribution. The investigation confirmed that the slope, which failed, consists of unengineered fill with foreign debris, steep gradients (~66°), poor compaction, and inadequate drainage – factors exacerbated by extreme rainfall and a high groundwater table (~4.1m bgl). Finite element modelling revealed a critical factor of safety (FoS) of just 1.35, well below acceptable levels, indicating a high risk of further failure. AGS recommended a suite of remediation measures including staged excavation, sheet piling, retaining wall construction, use of non-dispersive backfill, geotextiles, soil anchors, and vegetation (e.g. Vetiver grass), with final modelling showing an improved FoS of 3.18. These findings and recommendations aim to ensure long-term slope stability and mitigate future risks to the adjacent property.
✔ Proposed Mixed-Use Development - Queen Street, Campbelltown NSW
Based on the Geotechnical Design Report for the Shoring System at Queen Street, Campbelltown, prepared by AETG. The slope stabilisation strategy centres around the careful design and modelling of shoring systems to control soil movement and maintain excavation safety during the construction of a deep double-basement and high-rise development.
The report addresses slope stabilisation through a combination of anchored and cantilevered soldier pile systems, reinforced with shotcrete walls and analysed using PLAXIS 2D finite element modelling. The aim was to control lateral soil movement, limit pile deflection, and ensure stability of adjacent infrastructure, including Sydney Water assets.
Each shoring section was tailored based on subsurface profiles which revealed shallow fill, residual silty clay, and weathered shale bedrock. Sections with higher risk, such as those near footings or utility lines incorporate ground anchors to reduce movement.
The PLAXIS modelling outputs indicated that while some sections exceeded the alert threshold for soil and pile movement (>12 mm), these movements were controlled after activating structural restraints like slabs and anchors. In the most stable section, final long-term deflections remained minimal, confirming effective slope and excavation face stability. Stress analyses on nearby water infrastructure showed negligible impact, affirming that the stabilisation measures also protected external assets.
✔ Proposed Warehouse Development - Picton Rd, Razorback NSW
The Geotechnical Investigation Report was prepared to determine geotechnical design parameters for the proposed warehouse development project at Picton Road, Razorback NSW. The report includes an overview of the site condition, description, fieldwork, drilling investigation, soil profiles, field dynamic cone penetrometer testing, laboratory testing, Atterberg Limits, Californian Bearing Ratio, recommendations, groundwater considerations, preliminary bearing pressure assessment, earthwork methodology, design CBR, and limitations. The report was prepared in conjunction with laboratory tests to determine the existing site conditions based on the investigation findings. The scope of work included reviewing existing geology maps and documentation, determining in-situ soil conditions via mechanical auger investigation, obtaining subsurface soil profile and geotechnical parameters, determining groundwater during investigation, determining in-situ consistency of shallow subgrade, determining design Californian Bearing Capacity (CBR) value, determining soil reactivity and site classification, determining bedrock level, and providing comments and recommendations on investigation findings. The report also includes a walkover observation of site conditions, drilling of four deep boreholes across the factory warehouse footprint, and five shallow boreholes across the proposed access road for bulk sampling.
✔ Proposed Under-bore Installation - New South Head Rd, Vaucluse NSW
The geotechnical investigation conducted by AETG at New South Head Road, Vaucluse NSW, was commissioned by Alliance Living Pty Ltd to assess subsurface conditions for a proposed under-bore installation of a high-pressure gas main beneath a public roadway. Fieldwork included two boreholes drilled to refusal depths (3.8 m and 4.3 m), Perth Sand Penetrometer testing, and laboratory soil aggressivity analysis. Subsurface profiling revealed fill overlying residual silty sand and highly weathered sandstone bedrock. The soil was found to be non-aggressive to steel and mildly aggressive to concrete, with a high pH (9.6) and low concentrations of chlorides and sulphates. No groundwater was encountered at the anticipated 1.5 m invert level. A safe allowable bearing pressure (ABP) of 50 kPa was established based on field PSP results. AETG recommended 2:1 (H:V) batter slopes for excavations and specified earthworks requirements including 98% SMDD compaction for backfill and appropriate material selection for pavement reinstatement. These recommendations aim to ensure geotechnical stability and compliance with local standards throughout the construction of the under-bore infrastructure.