SUMO Engineering Geophysics Capability Statement

SUMO Geophysics for Engineering Capability Statement

No more guesswork above or below ground sumoservices.com Survey services you can rely on...

The SUMO Group is one of the leading, multi-disciplinary survey practices in the UK.

SUMO Group Accreditations

We are committed to maintaining the highest possible standards in all aspects of surveying. We pride ourselves on providing a survey solution individually tailored to your needs.

We also pride ourselves on maintaining industry leading professional accreditations and a high level of appropriate insurance cover.

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SUMO Group Insurance Cover Professional Indemnity Public Liability Employee Liability Drone Operator

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With over 35 years experience in near surface geophysics, SUMO utilise the latest non-invasive ground characterisation techniques for the geotechnical, civil engineering, water and environmental industries.

Geophysical surveys you can rely on...

Air Raid Shelters

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Badger Setts

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Burials

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Buried Foundations

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Buried Manholes

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Cellars & Basements

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Chimney Flues

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Earthing Installations

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Geological Applications

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Landfills

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Mineshafts

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Post Tension Cables

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Rebar

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Sinkholes

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Soil Thermal Resistivity

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Structural Investigations

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Tree Roots

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Underground Storage Tanks

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Voids

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Water Engineering

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SUMO applies a variety of geophysical techniques to investigate buried material and structures that could be relevant to engineering design.

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Air Raid Shelters Air raid shelters vary from large public shelters built with bricks and reinforced concrete through to small private shelters using corrugated steel panels.

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Many of these were removed after the war, however, others remain buried and are often encountered during construction works. Whether a small back garden or a large brown field site, SUMO can conduct a geophysical survey to locate these buried structures before any construction work takes place.

Rapid, cost-effective techniques like Magnetic Survey and Ground Conductivity are often used initially, and then targeted with higher resolution techniques such as Ground Penetrating Radar (GPR) which gives depth information to the top of the shelter.

Above: Example GPR radargram (section view). The planar feature at the end is representative of an air raid shelter.

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Above: GPR Timeslice showing an air raid shelter in the south east of the site at c. 0.75m depth. A pipe or service is also seen running through the site.

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Badger Setts In the UK, badgers are a protected species under the Protection of Badgers Act 1992, with substantial penalties payable where an offence is commited. Their presence can create major problems for development.

Badger Setts are not always evident by just spotting entrance holes. They are often a vast network of tunnels and chambers forming a complex underground territory extending from anything between 20 – 100 meters and may have one or several entrance points!

Mapping the entrances of the badger sett can provide a basic understanding of the area occupied by it, but to further understand its full extent, requires a geophysical survey. This will provide the information needed detailing the central nest, tunnel layout and the depth of the tunnels.

Above: Example Radargram (section view) of GPR showing voids relating to Badger Setts.

Above: Example GPR interpretation showing the extent of badger sett on site.

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Burials There are many reasons why burial sites may require investigation. These may include new developments in urban areas, extensions and remedial work to churches, or academic research.

The most suitable geophysical technique is Ground Penetrating Radar (GPR). This is a high-resolution technique which offers depth information, measuring to the top of the burial, and allows the data to be analysed in plan or section view.

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GPR can be conducted over a variety of surfaces, meaning that the same equipment can be used on a grassed graveyard or on a church floor. Individual burials, as well as vaults can be located with GPR.

Above: Timeslice plan view of GPR data in a Cathedral Cloisters showing numerous EastWest orientated burials (in red) at c.1.5m depth.

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Above: Section view of GPR, showing 6 coffin burials below 1m depth.

Buried foundations can create a costly obstacle when developing a brownfield site and can delay a project or even halt the works altogether.

Historic plans exist for many sites, but there is often no record of how much of the foundations remain, or indeed how much has been removed by a previous

Above: Ground Conductivity data in plan view, together with a basic Interpretation showing foundations of a former gas works.

contractor! Knowing about this risk at the design stage will improve both the

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Buried Foundations

profitability and delivery timescale of your project.

From small private sites, to operational car parks and active construction sites, SUMO has an approach that can help.

Using combined methodologies such as Ground Conductivity, Ground Penetrating Radar (GPR) or a Detailed Magnetic Survey, a survey programme can be designed to give you the best information about your site in the most cost-effective way.

Above: Section view of GPR data, showing a large anomaly which is likely to be the remains of a substantial foundation at 1m depth.

Above: Timeslice (plan view) of a Roman Villa collected with High Density GPR.

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Buried Manholes With resurfacing works, inherited brownfield sites and poor or no utility infrastructure records, difficulty in locating a manhole cover has sadly become a relatively common problem.

Above: A buried manhole cover located by GPR and marked out using temporary paint.

SUMO uses one of two methods of Ground Penetrating Radar (GPR) to help locate lost manholes; High Density Ground Penetrating Radar (GPR), which records readings every 8cm, to produce a high resolution and comprehensive plan of the site. In the example below the survey revealed an anomaly which did not correlate with the visible manholes on the ground, and this was plotted on the drawing for use by the client.

Dual Frequency (DF) GPR systems, consisting of two different frequency antennas (300MHz and 800MHz). The added benefit is that this can be interpreted on site, to show the location of a buried manhole instantly, meaning that there are no site delays whilst waiting for the data to be processed and interpreted.

Above: Timeslice plot (plan view) of High density GPR showing the location of a buried manhole.

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Above: Photograph taken on a site by one of our clients after a buried manhole was exposed through excavation a day after our survey on site.

Cellars & Basements

Typically, cellars are designed as storage spaces, whereas basements are often finished off as living spaces.

Either way, both can prove a problem on development sites, particularly if they are not known about prior to starting site works.

GPR is the most suitable technique to locate hidden cellars and basements. It has the capacity to work through a wide variety of surface materials, from soft landscaping, through to hard surfaces such as tarmac and concrete, both inside and outside buildings.

GPR also provides all important depth information.

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The contrast between the roof of a basement or cellar and the space beneath produces a large electrical contrast which is detected by the GPR. If a cellar is full of stock or is disused and has collapsed internally the reflections characteristics become more complex.

Above: Section view of GPR, showing two probable basements/cellars with flat roofs and the same data in plan view (Timeslice) showing three possible cellars at c. 0.7m depth (red responses).

Above: Section view of GPR, showing probable vaulted basement/cellar (probably boiler rooms) at c. 0.5m depth.

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Chimney Flues During building renovations, it can be essential to know where your chimneys and flues are, and what condition the stacks are in.

Above: Chimney survey showing the route of the chimney within a wall plotted in AutoCAD.

Routes of chimneys and flues are not always obvious, may deviate widely, and can be hidden within unexpected walls. So, if you are trying to reinstate period fireplace features within an older building, or just trying to avoid the chimneys and flues all together, it is important to accurately trace them.

SUMO uses a high frequency GPR system to locate the voids created by the flue. These voids show as areas of strong reflectors, often with characteristic ringing, making the routes of these features identifiable compared to the background readings. Depending on what is required, SUMO can mark these features out on-site, or bring the data back to the office to produce a building plan.

We can also create a photogramatic record of the entire roof of the building, using a drone (UAS), from which we can create 2D plans or 3D models, all while never having a person leave the ground.

Above: Drone photograph showing the detail of mesh covers on chimneys. One is compromised allowing bird ingress, additionally the fact that there are only mesh covers means that there is the potential for water and damp issues.

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Above: A SUMO surveyor using a compact 2GHz handheld GPR antennae, to ascertain the route of a chimney. Above Right : Example Radargram showing anomaly caused by a chimney flue.

In order to ensure people’s safety, proper earthing is crucial in preventing electric shocks, especially in the design of new Battery Energy Storage Systems (BESS) or infrastructure.

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The planning and installation of new generators, substations, solar & wind farms and the associated electrical grid infrastructure requires a full understanding of a site’s electrical properties. This can then be used to design an appropriate earthing

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Earthing Installations

system that may include earthing plates, rods, or pits, depending upon the exact requirements and site conditions.

Soil resistivity measures the capacity of the ground to pass an electrical current and is a critical factor in the planning and installation of an electrical earth, with soil layer models forming the basis of all grounding designs. The models are produced from

Above: A typical model displays a progressive increase in resistivity with depth.

Above: Soil resistivity testing in progress on a new solar farm development.

Above: Tabulated soil resistivity testing results at standard electrode spacings.

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Geological Applications Prior to starting a construction and infrastructure project, it can be worthwhile characterising the site’s subsurface as part of a wider geotechnical investigation, to avoid any unexpected problems and associated costs.

This can include anything from the depth of drift cover to bedrock to the extent of sinkhole formation.

SUMO’s Geophysics for Engineering Team utilise a combination of the latest survey techniques, including Ground Conductivity, Magnetic Survey, Electrical Resistivity Tomography (ERT) and Ground Penetrating Radar (GPR) to understand more about the natural features below the ground, including.

Alluvial channels/paleochannels

Mineralised veins

Bedrock depth

Mineshafts (in mineralised areas)

Large discontinuities i.e. faults, major joints/fractures

Sinkholes/solution features

Above: Solution feature in weathered chalk.

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Above: A GPR Section view showing areas of granite at approximately 2m depth.

Above: Ground Conductivity data showing potential sinkholes.

According to recent reports there are over 21,000 landfills across England and Wales. Of these over 1,200 are categorised as containing hazardous waste and a further 7,000+ contain industrial waste.

SUMO’s specialist engineering department uses a wide array of geophysical equipment to obtain the best information about your site, whilst working to your

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Landfills

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budget.

For large sites, SUMO would use an Electromagnetic Ground Conductivity system to survey sites to a depth of 4m. Survey collection is quick and efficient, meaning large sites can be investigated swiftly and cost effectively.

A Ground conductivity survey can be followed up with more targeted techniques such as Ground Penetrating Radar (GPR) or Electrical Resistivity Tomography (ERT)/Resistivity Imaging in order to obtain depth profiles across the site.

Above: Identifying a concealed landfill on a ground conductivity contour plan.

Above: GPR data showing depth of landfill which has been capped.

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Mineshafts There are estimated to be around 405,000 abandoned mine entries in the UK, of which only 150,000 are recorded.

Approximately 15 mineshafts collapse each year and with so many unrecorded shafts, mines can have a huge and unexpected impact on future development projects.

A range of geophysics techniques can be used to find abandoned mineshafts, which rely on the different physical

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properties of the cap (if present) and the shaft. These include Ground Conductivity Survey, Detailed Magnetic Survey and a Ground Penetrating Radar Survey (GPR).

The selection of the appropriate Geophysical technique is often dependent upon the size of the survey area and the ground conditions present, as well as any information that is available about the shafts themselves. The more techniques that can be deployed the better, as several targets found at the same location by different techniques will reinforce the confidence of the interpretation made.

Above: Recorded location of a shaft, but where is it?

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Above: GPR Radargram (section) showing possible mineshaft at c. 1m depth.

Post-tensioning is a method of reinforcing concrete, used extensively in the construction of buildings and bridges.

When drilling into a concrete slab for the purpose of installing machinery, office furniture, pipework, air conditioning etc., there is always a risk that a post tension steel cable may be accidentally cut or damaged.

This can weaken the slab structurally or the cable (which is under tremendous

Above: 2GHz GPR Antenna with SIR 4000 controller. ​

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Post Tension Cables

pressure) may rip out of the slab, causing severe injury to anyone in the vicinity.

The cost to repair a single post tension cable alone is £1000+ and it can affect the entire stability of the building.

SUMO uses non-destructive and non-invasive high-frequency Ground Penetrating Radar (GPR) to locate the position and depth of post tension cables.

Above: Basic report showing photos of post tension cables and their location.

Above: Radargram. Reinforcing bars and post tension cable.

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Rebar Concrete reinforcement (rebar) is located in both ground slabs and within the walls of many buildings.

When remedial work is to be carried out on these structures it is important to know where the rebars are located within the concrete slab.

Above: Mark out survey interpreted on site.​

SUMO uses high frequency Ground Penetrating (GPR) to locate these individual rebars, along with a cover meter which can estimate the diameter of the individual bars.

Data is either recorded and/or interpreted on site, depending on your requirement, budget and timescales, to produce 3 survey outputs: Mark out survey, Mark out survey with basic reporting and a Post processed Survey with full reporting.

Mark Out Survey - A basic mark out survey is where a GPR survey is interpreted on site and the location of the rebar is marked in situ.

Mark out survey with basic reporting - ​This option is employed where intrusive work is scheduled soon after the survey, but the site is too complex to warrant a simple mark out survey.

Post processed survey with full reporting - A full desk-based analysis of the data and production of a full report is useful at the design and planning

Above: GSSI 2Ghz Palm Antenna.​

phase and/or if the site is more complex.

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Above: Section View of GPR data showing rebar at 100mm depth. ​

Above: Mark out survey with basic reporting.

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Sinkholes If a sinkhole or unexplained depression suddenly appears on your site, you urgently need to know the extent of the problem, its likely cause and the risk of more incidents.

Some rock types are more susceptible to the formation of sink holes, with carbonate rocks including chalk and limestone being particularly sensitive, as they can be easily dissolved by groundwater.

Less dramatic sinkholes also occur where the overlying material is more porous and slowly ingresses into the underlying void resulting in a gradually deepening depression over time.

SUMO’s specialist geophysics department can complete a full geophysical survey of the area, using ground conductivity and/or ground penetrating radar.

Above: Example radar data showing area and depth of anomaly likely to be voiding below the ground.

Above: GPR timeslice plot showing the location of possible voids created by sinkholes.

Above: The results of the ground conductivity survey

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Soil Thermal Resistivity Testing Prior to the design and installation of underground electrical cables, it is important to understand the thermal properties of the soil or made ground.

You need to ensure the heat produced by current flowing through an underground power cable is properly dissipated and avoid

premature failures. Often estimations are made, but where conditions are uncertain or variable along a cable route, it is important that a proper quantitative assessment is made of the ground.

Soil thermal resistivity testing measures the capacity of the ground to conduct or dissipate heat.

The thermal resistivity of a soil will determine whether a buried power cable remains stable or overheats. A build-up of heat around the cable can reduce transmission efficiency, or in the worst case scenario cause it to melt and fail completely.

Potential problems can be identified by measuring the thermal resistivity of the in-situ soil.

Remedial measures that can be taken, including changing the capacity and insulation of the cables, or installing corrective thermal backfills in the cable trench.

Above: Cable route showing 5 locations where soil thermal properties need measuring.

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Reading No.

Thermal Resistivity (°C-m/W)

Temp

Error

Depth (m)

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1.007

17.09

0.0058

1.0

2

1.011

17.11

0.0053

1.0

3

1.011

17.12

0.0053

1.0

Above: Example results of thermal resistivity testing at 3 seperate locations.

Above: In-situ thermal resistivity testing with a needle probe.

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Structural Investigations Utilising the latest non-invasive survey techniques, SUMO’s engineering geophysics team have a solution to help you understand more about your concrete assets.

Ground Penetrating Radar (GPR), which is used predominantly in these investigations, can detect voids and delamination within the concrete, as well the thickness of the concrete slabs or walls themselves. Utilities within concrete can also be identified, along with steel elements such as beams, girders and metal plates.

Most sites take no more than a day to survey and immediate initial results may

Above: GPR radargram showing the base of a concrete floor at 280mm depth, along with 3 post tension cables above the slab at 190mm depth and possible cables/structures below the slab at 300mm depth.

be presented on-site, with more detailed post-processed results, presented in AutoCAD, available shortly afterwards to suit your timescale.

Above: GPR Radargram showing voids beneath a dry dock floor at depths between 0.75m and 1m.

Above: Section view of GPR data showing a utility/service within the concrete below the rebar at 0.5m depth.

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Tree Roots The protection and preservation of trees has become a significant issue for many development projects in recent years and can create significant planning, design and construction problems.

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Historically, the radius of the root protection area has been estimated by measuring the diameter of a tree at a height of 1.5m above ground and multiplying this figure by a factor of 12. Thus, a 1m diameter tree would have a circular root protection area around it with a radius of 12m. However, this can often lead to large areas of a site being protected when in actual fact there are no tree roots present.

SUMO can complete a high-density ground penetrating radar survey, over the area surrounding the tree to not only identify the tree root distribution pattern, but the depth of the roots.

Above: SUMO created the above 2D CAD image from data collected by SUMO's highdensity multi-channel GPR. Note the diameter of the tree, the extent of the canopy and the irregular distribution pattern of the tree roots.

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Above: 3D image from data collected by SUMO's high density multi-channel GPR. It shows the exact location of the tree roots at 0.2m depth.

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Underground Storage Tanks Underground Storage Tanks are prevalent on sites throughout the UK including petrol filling stations (PFS), council depots, fire and ambulance stations, military bases and industrial sites.

The most suitable technique for detecting tanks is Ground Penetrating Radar (GPR). It works in a wide range of congested environments and will detect tanks made from both metallic and non-metallic materials.

Other techniques that can be used are Magnetic Survey and Ground

Above: 3D rendered image of the GPR survey results presented in CAD. The tanks are visualized along with a service running over their top.

Conductivity depending on the site conditions and the materials from which the tank has been made. These techniques are lower resolution, but more cost effective, enabling large areas to be surveyed and then targeted with GPR for improved accuracy and depth information.

All three techniques carried out on-site on the same day, with most sites taking no more than a day to survey.

Above: Example GPR radargram (section view). In the centre two broad crested anomalies can be seen showing the location of two fuel tanks.

Above: GPR Timeslice (plan view) showing 3 adjacent tanks. Above Right: Interpretation of GPR data in CAD showing the 3 tanks (A-C) at 0.5m depth.

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Voids From settlement to sinkholes, voids can cause a major problem on any site. Not only could they affect your design, budget and programme, but they could result in major injury.

Whether siting a crane, erecting scaffolding, or simply working on a site, if voids are present, it’s essential that you know about them before starting work or bringing any heavy equipment onto site.

Ground Penetrating Radar (GPR) is an ideal technique to locate voids. The large electrical contrast between solid materials and air generates a high amplitude response, which should stand out clearly against the background reflections.

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Above: Cicl radargrams (section views) showing voids at 1m depth caused by water ingress along a stretch of promenade.

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Water Engineering SUMO’s engineering geophysics team can provide invaluable information during the construction and management of water infrastructure.

Whether remedial work is taking place to replace harbour gates, restoration work is being done to re-open a disused canal, or settlement or cracks are appearing along promenade, SUMO’s engineering solutions can help identify the problem.

GPR can be used to search for evidence of hidden voids within harbour walls, beneath a canal towpath, behind a canal wall or before siting a crane during remedial operations on locks and weirs.

With a vast wealth of experience and a wide range of equipment applicable to many different scenarios, SUMO is here to help you to understand your water infrastructure, avoid any hidden dangers on your site and minimise unexpected costs.

SUMO MAINTAINS HIGH LEVELS OF APPROPRIATE INSURANCE COVER Above: A GPR survey in progress over the top and side of a harbour wall.

Above: A vertical GPR profile down the side of a harbour wall, showing evidence of voiding at 0.7-1.2m within the wall..

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