Slope Stability Analysis & Design
Atlas Engineering & Technology Group (AETG) offers comprehensive slope stability analysis and design solutions tailored to your needs. Slope stability analysis and design are crucial aspects of geotechnical engineering, particularly in the construction of infrastructure like roads, embankments, dams, and buildings on or near slopes or hillsides. The goal of slope stability analysis is to assess whether a slope is stable or prone to failure and to design measures that ensure long-term safety and stability. A thorough understanding of these factors allows our engineers to design and implement effective stabilisation measures in accordance with Australian Standards (AS1726, AS3798) and Australian Geomechanics Society (AGS) related documents. At AETG, our geotechnical engineers can provide effective solutions for your project needs.
Slope Stability Analysis refers to the capacity of a slope to withstand movement or failure caused by gravity, erosion, or other forces. It is a key consideration in geotechnical engineering, especially for projects involving embankment stability, excavations, natural slopes, and hillside developments.
Factors Affecting Slope Stability
- Groundwater Conditions: Presence of water in the slope mass can reduce friction and cohesion, increasing the likelihood of failure.
- Vegetation: Roots can provide some stability by reinforcing the soil, though the loss of vegetation (due to fire, construction, etc.) can make the slope more susceptible to failure.
- Seismic Activity: Earthquakes can induce forces that destabilize slopes.
- Soil/Rock Properties: Shear strength, cohesion, angle of internal friction, and type of soil/rock.
- Human Activity: Excavations, construction, and other activities can alter slope stability.
Slope Geometry: Gradient of the slope, height, and shape of the slope.
Why is Slope Stability Analysis Important
- Design: Slope stability analysis helps engineers design safe and cost-effective slopes for various projects.
- Risk Assessment: It helps identify areas at risk of landslides or slope failures, allowing for proactive measures to be taken.
Safety: Ensuring the stability of slopes is crucial for public safety and the integrity of infrastructure.
Our Methods of Slope Stability Analysis and Design
Finite Element Methods (FEM): Finite Element Methods involve constructing a detailed numerical representation of the slope, which is then subjected to various applied loads. FEM enables engineers to evaluate the stress-strain responses within the slope, providing comprehensive insights into its behaviour under different conditions. This approach is particularly advantageous for complex slope geometries and scenarios that require in-depth analysis.
Limit Equilibrium Methods (LEM): A widely employed technique that divides the slope into vertical segments, with each slice analysed to assess the forces acting on it and determine the overall factor of safety. Common approaches within this method include Bishop’s simplified method, Janbu’s method, and Spencer’s method. These techniques offer a simplified yet effective means of evaluating slope stability, applicable to a range of geotechnical conditions.
Risk Assessment: Probabilistic methods assess the likelihood of slope failure by incorporating uncertainties such as variations in soil properties, environmental factors, and other influencing variables. By quantifying the probability of failure, these methods allow engineers to make informed decisions regarding risk management and design, ensuring slopes are constructed with adequate safety factors to mitigate potential hazards.
Slope Stabilisation Methods
- Grading and Reshaping: Adjusting the slope angle and geometry to reduce the driving forces acting on the slope. This may involve cutting and filling operations to achieve a more stable configuration.
- Drainage Control: Installing proper drainage systems to manage surface and subsurface water flow, thereby reducing pore water pressure and increasing stability.
Vegetation and Erosion Control: Planting vegetation can help stabilise slopes by reinforcing the soil and reducing surface erosion.
Reinforcement Techniques
- Soil Nailing: Installing steel bars or nails into the slope to reinforce and stabilise the soil mass.
- Retaining Structures: Constructing retaining walls, such as gravity walls, cantilever walls, or anchored walls, to provide lateral support to slopes.
Geosynthetics: Using geotextiles, geogrids, and other geosynthetic materials to improve soil strength and stability.
Monitoring and Maintenance
- Instrumentation: Installing instruments like inclinometers, piezometers, and strain gauges to monitor slope movements and pore water pressures over time.
Regular Inspections: Conducting routine inspections to identify any signs of slope movement or distress and taking corrective actions as needed
Why Choose AETG for Slope Stabilisation
AETG understands that choosing the right slope stabilisation technique depends on several factors such as soil type, slope geometry, the degree of slope failure risk, environmental conditions and project costs. Often, multiple techniques are combined to achieve the desired level of stability and safety. It is essential to conduct thorough site investigations and stability analyses before implementing any stabilisation method to ensure the chosen solution is effective and sustainable.
Successfully Completed Jobs by AETG to Date
✔ Proposed Residential Development - Noorong Ave, Frenchs Forest NSW
AETG was engaged to conduct a geotechnical investigation at a private residence as part of Northern Beaches Council Development Application (DA) approval process. The proposed residential development plan is to construct a second-story extension of the existing dwelling located on a steep slope. The proposed development was identified by council to be located in an area found to have landslip potential, and a slope stability risk assessment was required to assess the global stability of the property to ensure adequate designing and safety measures were met and that the proposed development didn't pose a risk to the global stability of the property in question or surrounding residencies and utilities. The geotechnical investigation was performed with mechanical and manual drilling operations to assess the subsurface ground conditions, including groundwater, soil profile, bearing capacity and plasticity parameters of the in-situ soils to help with design requirements and council concerns. A detailed risk assessment was undertaken to indicate the risk level for potential damage to property and life found within the immediate vicinity of the subject site. The project was successfully completed in a timely manner to satisfy the client's needs and in accordance with relevant Australian Standards and guidelines.
✔ Proposed Landslip Remediation - Guy Place, Emu Plains NSW
A comprehensive geotechnical investigation was conducted by AETG to evaluate the global stability of a landslide observed on a previously backfilled building pad, located on a slope near the subject site. The investigation revealed that the subsidence event had occurred directly beneath the pre-existing concrete driveway, posing a risk of destabilising the adjacent dwelling, which is an occupied residence. Drilling operations were performed to determine the cause and extent of the subsidence, assess potential contributing factors, and develop remediation solutions to address and mitigate the issue. Subsurface soil profiles, soil strength parameters, material properties (including plasticity, Emerson classification, particle size distribution, and foreign material content), groundwater conditions, and bearing capacity were all assessed during the site visit. A 2D finite element analysis was employed to model the subsidence event and to design an appropriate remediation strategy. The investigation concluded that the subsidence was caused by poorly compacted fill material, which was classified as general waste and deemed unsuitable for the intended application.
✔ 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.