Highway Subsidence, Teesside

1st November 2019

Initial Inspection

From the initial geotechnical survey, significant deformation cracking in the highway was visible. Northpoint’s initial evaluation considered the potential causes of the subsidence. Observations included:

• No highway drainage
• No supporting kerb-lines
• The presence of established woodland
• The presence of a large sewer beneath the highway

To be conclusive, the geotechnical survey included intrusive ground investigation works to assess conditions within and beneath the highway.

Data Records

Following the initial inspection, a number of data sources were assessed. Geological records show that the line of the highway follows a geological boundary, with sand to the north and clay to the south.

Historical records showed that the T-junction in the road where deformation is most obvious was created in the 1980’s.

Formal Investigation

The geotechnical survey works included a series of road cores to assess the ‘make-up’ of construction layers within the highway. The road cores were followed by a series of insitu tests to determine the strength/nature of materials supporting the construction layers. Finally, deep boreholes were sunk to assess how the underlying soils are behaving.

Northpoint concluded that when the T-junction was created in the 1980’s, this was of substandard construction (when compared to Design Guide Standards).

With no formal highway drainage or supporting kerb-lines and no stone sub-base, continued deformation will occur unless long-term remedial works are completed.

The upper road construction layers are placed directly onto clay soils which are influenced by surrounding trees (that take moisture out of the ground and cause heave).

If you require a geotechnical survey or need support with subsidence problems (whether a road, building structure, slope etc.), the team at Northpoint will happily talk you through the various options available to investigate.