Derby sits on a varied geological sequence of Triassic sandstones, Mercia Mudstone, and glacial till, with ground conditions that shift notably between the city centre and the southern industrial estates near the River Derwent. Our team has completed over forty DMT soundings in Derby since 2019, using the Marchetti flat dilatometer to record lateral stress and modulus values at 20 cm increments. The test is particularly useful where conventional SPT blow counts do not correlate well with observed stiffness, especially in the stiff clays that underlie much of the suburban housing stock. We routinely combine the DMT with clasificación de suelos to validate stratigraphic boundaries, and with CBR vial when the data feeds into pavement design for access roads. Each sounding follows BS EN 1997-2 execution rules and the equipment is calibrated annually against a UKAS-certified reference cell, so results are traceable to national standards.
Lateral stress index Kd from the DMT correlates directly with overconsolidation ratio in Derby's Mercia Mudstone, reducing reliance on expensive oedometer tests.
Process overview
Local context
We worked on a warehouse extension off Sinfin Lane where the structural engineer assumed a bearing capacity of 200 kPa based on SPT values from a single borehole. The DMT revealed Kd values below 2.0 in the top 3 metres, indicating only moderate overconsolidation in what was actually reworked glacial till, not intact marl. The foundation design had to be revised to a raft on improved ground, adding two weeks to the programme. That is the kind of risk that a flat dilatometer test in Derby catches early: the city's superficial deposits are heterogeneous, and one borehole alone cannot capture the lateral variability. We always recommend at least three DMT soundings per hectare for commercial plots, spaced to cover the main geomorphic units.
Reference standards
BS EN 1997-2:2007 (Eurocode 7 – Ground investigation and testing), BS 5930:2015 (Code of practice for ground investigations), BS EN ISO 22476-11 (Standard test method for performing the flat plate dilatometer), ISSMGE TC16 DMT recommended procedure (Marchetti, 2001)
Additional services
Single-point DMT sounding (0–20 m)
One vertical profile with readings every 20 cm. Suitable for small residential extensions or preliminary site assessments. Includes a field log, M and Kd plots, and a summary of interpreted parameters.
Multi-sounding site characterisation
Three to six soundings across a site, correlated with existing borehole logs. Delivered as a combined DMT report with stratigraphic cross-sections and design parameters for foundations or retaining walls.
DMT for pavement and slope design
Shallow soundings (0–8 m) focused on subgrade stiffness and lateral stress. Ideal for road widening, embankment stability, or MSE wall design. Includes K0 and modulus profiles for finite element analysis input.
Typical parameters
Common questions
How does the DMT compare with a CPT in Derby's Mercia Mudstone?
The DMT measures lateral stress and stiffness directly, while the CPT gives cone resistance and sleeve friction. In Mercia Mudstone, which is often fissured and overconsolidated, the DMT's Kd index correlates better with OCR than CPT tip resistance. We often run both tests on the same site: CPT for stratigraphic profiling, DMT for modulus and stress state.
What is the typical cost range for a DMT in Derby?
The cost for a single 20 m DMT sounding in Derby ranges from £730 to £940, including mobilisation within 15 miles of the city centre. Multi-point discounts apply for three or more soundings on the same site. Prices exclude VAT and any additional laboratory testing.
Can the DMT be used to assess liquefaction potential in the floodplain areas?
Yes, but with caution. The DMT does not measure cyclic resistance directly. We use the Id–Kd chart from Marchetti (2001) to estimate cyclic stress ratio thresholds. For Derby's floodplain deposits near the Derwent, where fines content is high, we typically combine DMT with SPT-based liquefaction assessment (Youd-Idriss 2001) for a more solid evaluation.