Thurber Engineering Ltd.

The assessment of subsurface conditions for placement of footings or pile foundations which will transfer load to the ground with limited settlement is termed Foundation Engineering. Where soil or rock do not have adequate capacity to support the structure under static or dynamic loads, it is necessary to provide ground improvement such as soil densification, grouting or reinforcement through anchorages or geosynthetics. Practicing in this field requires a multi-disciplinary knowledge of local geology, soil and rock mechanics, and the ability to use analytical and numerical methods. Limit States Design is used to account for load and resistance uncertainties, requiring a knowledge of probabilistic methods.

Thurber provides services related to:

• site investigation (drilling, coring, test pitting, field mapping, CPT)
• foundation design (piles, spread footings, rafts)
• LRFD and WSD
• bearing capacity and settlement analysis
• lateral earth pressures
• shoring and underpinning design
• seismic design and liquefaction assessment
• construction dewatering
• forensic assessments
• construction inspection (piles, footings, caissons)
• materials testing (soils, rock, concrete, asphalt)

Slope Stability Engineering encompasses the assessment of static and dynamic stability of natural and man-made slopes in soil and rock, and development of mitigation measures. It requires a multi-disciplinary knowledge of geology and geomorphology, soil and rock behaviour, and analytical methods such as limit equilibrium and numerical methods.  Thurber’s expertise includes identification of landslide triggering mechanisms, deterministic and probabilistic landslide hazard assessments, debris flows, and seismic related phenomena such as earthquake-induced slope movements and liquefaction.

This experience includes:

• terrain assessment and field mapping
• soil and rock investigation (drilling and test pitting)
• laboratory testing (index property testing, direct shear and triaxial testing)
• slope stability analysis
• slope instrumentation and monitoring
• coastal erosion studies
• design and inspection of remedial measures and stabilization works

Designing retaining structures to hold back soil or rock or to provide lateral support for vertical or near-vertical grade changes requires a thorough knowledge of subsurface conditions and of soil and rock behaviour under static and dynamic loads. Practicing in this field requires a multi-disciplinary knowledge of local geology, field and laboratory investigation methods, soil and rock mechanics, and ability to use analytical and numerical methods to examine soil-structure interaction problems.

Thurber’s experience includes:

• site investigations
• lateral earth pressures for static and seismic conditions
• design parameters for retaining walls (gravity, cantilever, modular block)
• mechanically stabilized earth wall and embankment design
• diaphram, H-pile, sheet pile, shotcrete and anchor shoring systems
• soil nailing
• field inspection and testing (field density, anchor and concrete testing)

Design and construction of earthworks requires continued involvement from geotechnical and materials engineers, from assessment of borrow quality and stability of cuts and fills through to construction quality assurance and quality control. Due to the significant amounts of soil and/or rock which normally have to be moved, geometric and other constraints, which are a function of the properties of these materials in their native and man-made states, have to be assessed in detail to achieve economic, yet safe designs. Typical earthworks include road cuts and fills, earth and rockfill dams, embankments on soft soils, canals and landfills.

Thurber provides services such as:

• terrain assessment and field mapping
• soil and rock drilling investigation
• laboratory testing
• slope stability and settlement analysis
• slope instrumentation and monitoring
• erosion and sediment control studies
• insitu permebility testing of liners (AEP)
• materials and construction QA/QC

Terrain Analysis is the process of identifying geological landforms and assessing their suitability for a specific end purpose. It is well suited for conceptual and preliminary planning for linear projects and the identification of borrow/aggregate material. Terrain Analysis typically involves indirect methods of assessment including traditional stereo airphoto interpretation and modern GIS processing and remote sensing techniques. Depending on the complexity of the project, verification and determination of engineering properties might include a field program involving geotechnical drilling, test pitting and geophysical surveys.

Thurber maintains a comprehensive geospatial database of published and in-house geotechnical/geological reports and maps to assist in these studies, which include:

• airphoto interpretation and landform mapping
• GIS and remote sensing
• terrain visualization using DEM and LiDAR
• route selection for pipelines, roads and power transmission lines
• slope stability and setback lines
• geohazard hazard mapping and risk analysis
• aggregate mapping and testing
• field investigation (drilling, test pitting, geophysics)

Studies related to dams and their reservoirs rank among the most prestigious geotechnical engineering assignments. Thurber has a long history of involvement with major dam projects in Western Canada, ranging from major hydroelectric projects built in British Columbia in the 1960’s and 1970’s, to the massive tailings impoundments associated with oil sand mines in Alberta. Several of our senior engineers also have international experience. We conduct dam safety reviews and audits on a regular basis, and maintain facilities capable of advanced laboratory testing.

Our expertise includes:

• site investigation (mapping, drilling, exploration shafts, geophysics)
• dam safety reviews and audits
• seismic retrofit studies
• dam and canal rehabilitation
• earth dam design (embankment stability, material zoning, grouting)
• embankment and reservoir slope stability assessments
• numerical stress-strain-time and seepage analyses
• laboratory testing (strength, permeability, compressibility)
• construction inspection and field testing
• instrumentation installation and monitoring

The completion of new infrastructure in congested urban areas or near environmentally significant features often requires construction of underground facilities using trenchless techniques. Detailed investigation of soil, bedrock and groundwater conditions and assessment of relevant engineering properties are necessary for performance prediction and assessment of the trenchless construction impact on adjacent structures. Complex projects often require monitoring of instrumentation for confirmation of assumptions during design.

Services offered by Thurber include:

• site investigations in soil and rock
• feasibility studies
• groundwater characterization
• geotechnical design
• geotechnical baseline reports
• assessment of soil and groundwater disposal requirements
• instrumentation and monitoring during construction
• field services

Maintaining stability and limiting displacement to acceptable levels is an important part of geotechnical design. Geotechnical instrumentation to monitor performance of foundation pore pressures, deformations, anchor and strut loads, as well as tilt and vibrations at sensitive structures are often required to achieve the desired level of safety and efficiency during construction.

Services offered by Thurber associated with geotechnical instrumentation include installation, monitoring and interpretation of data for the following instruments:

• inclinometers
• tiltmeters
• shallow and deep settlement points
• vibrating wire settlement cells
• vibrating wire piezometers
• electro-level settlement profilers
• geophones
• load and pressure cells
• real time or datalogged acquisition systems
• web-based remote monitoring systems

Populated areas are often exposed to geological hazard events that must be assessed using risk-based engineering geological tools. Examples of such hazards are earthquakes, landslides, snow and rock avalanches, and debris flows.  Evaluating associated risks with respect to land usage requires sound knowledge of geological principles, airphoto interpretation and remote sensing techniques, and application of qualitative and quantitative analytical methods.

Thurber’s expertise includes:

• terrain assessment and field mapping
• soil and rock investigation (drilling and test pitting)
• laboratory testing (index property testing, direct shear and triaxialtesting)
• slope stability analysis
• design and inspection of remedial measures and stabilization works
• slope instrumentation and monitoring
• coastal erosion studies

The design of structures which are built on or in rock requires an in-depth knowledge of geology and rock mechanics, the discipline that deals with the mechanical behaviour of rock and rock masses. The principles of soil mechanics are also applied to designs associated with soft rocks. Typical applications in the Civil and Mining sectors include work related to dam foundations, tunnels and shafts, railway and road construction and open pit mine slopes.

Thurber has experience with:

• soil and bedrock mapping
• rock core logging
• in-situ permeability testing
• discontinuity mapping and rock slope stability analyses
• rock mass classification systems
• rock anchorage systems
• design of support for tunnels and slopes
• blast vibration monitoring
• stress-strain-time numerical modelling

A laboratory testing program is an integral part of every geotechnical investigation.  While index tests such as the determination of Atterberg Limits or Grain Size Distribution are performed for routine projects, the design of major structures such as dams, high-rise buildings, open pit mines and tunnels requires advanced testing to determine consolidation, permeability and strength properties. Thurber’s history includes the early development of an advanced soil-testing laboratory in Victoria, established to service several large dam projects underway in the 1960’s.

We have maintained and expanded our advanced laboratory in Victoria, and have added additional capacity in Edmonton and Toronto, to provide testing services such as:

• triaxial testing (consolidated or unconsolidated, drained and undrained)
• direct shear testing (soil or weak seams in rock)
• permeability testing (triaxial cell)
• consolidation and swell testing (soft soil, high plastic clay, peat)
• soil and rock durability testing