A 10-story apartment complex on Hamilton Street recently required settlement predictions we couldn't trust from SPT alone. The glacial till beneath Allentown varies in stiffness within meters. We deployed the Flat Dilatometer Test (DMT) to measure lateral stress index and horizontal modulus directly. That data fed into the foundation design and saved the structural engineer from over-designing piles. Before finalizing the bearing layer, we also ran a resistivity survey to map sand lenses that could trigger differential settlements. The DMT gave us continuous profiles without soil removal. That speed matters when you are working on a tight urban site with busy traffic above.
DMT in Allentown's glacial till delivers lateral stress and stiffness data that SPT cannot match, reducing foundation cost and risk.
Method and coverage
The DMT blade is a stainless steel wedge 95 mm wide, 15 mm thick, and 220 mm long. We push it into the ground with a hydraulic penetrometer truck. Every 20 cm we stop and inflate a steel membrane to measure the lift-off pressure (p0) and the expansion pressure (p1). The test takes about 15 seconds per reading. From these two numbers we calculate the material index (ID), the horizontal stress index (KD), and the dilatometer modulus (ED). In Allentown, where glacial deposits contain cobbles and dense sands, the DMT performs better than a cone penetrometer because the blade can penetrate stiff layers without damaging the membrane. We follow ASTM D6635-15 for every reading.
Technical reference image — Allentown
Regional considerations
Allentown sits in the Lehigh Valley, a region with deep glacial till and alluvial deposits. The water table fluctuates with the seasons, and the soils range from loose silty sands to dense tills. If you rely only on SPT blow counts, you miss the lateral stress state. That is critical for retaining walls and basement excavations. A contractor on a recent downtown project underestimated the lateral earth pressure and faced a wall displacement of 5 cm. The DMT caught the high KD values that warned us about locked-in stresses. We now include the DMT in every deep excavation design in Allentown to avoid similar surprises.
Continuous profiling every 20 cm to 40 m depth. We provide ID, KD, ED, K0, and OCR profiles. Ideal for deep foundations and slope stability analysis. Includes a field report within 48 hours.
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DMT with Seismic Module
Combines the dilatometer blade with a geophone to measure shear wave velocity (Vs). We correlate KD with Vs to estimate small-strain shear modulus (G0). Suitable for seismic site classification per ASCE 7 and liquefaction triggering analysis.
Standards that apply
ASTM D6635-15 (Standard Test Method for Performing the Flat Plate Dilatometer), IBC 2021 (Section 1803 – Geotechnical Investigations), FHWA-NHI-10-034 (Drilled Shafts Manual, lateral stress evaluation)
Quick answers
What is the difference between DMT and CPT?
CPT measures cone tip resistance and sleeve friction continuously. DMT measures lateral stress and stiffness at discrete depths. DMT is better for estimating K0 and OCR, while CPT is faster for soil classification. In Allentown's dense tills, DMT often penetrates layers where CPT refuses.
How deep can the DMT reach in Allentown?
We typically reach 30 to 40 m in the Lehigh Valley. In areas with cobble-rich glacial till, depth reduces to 20 m. We pre-drill through the upper 3 m of fill to protect the blade.
How much does the Flat Dilatometer Test cost?
The typical cost for a DMT sounding in Allentown ranges from US$770 to US$1,060. The final price depends on depth, number of readings, and access conditions. We provide a fixed quote after site visit.
Can DMT detect liquefaction potential?
Indirectly. DMT provides KD and ED which correlate to relative density and cyclic resistance ratio (CRR). We apply the method by Marchetti (1980) and Robertson (2009) to estimate liquefaction triggering. For a direct measure, combine DMT with shear wave velocity from the seismic module.
What is the turnaround time for results?
We deliver a preliminary profile within 24 hours of the field test. The final report with interpreted parameters and profiles follows within 5 business days. For rush projects we can expedite to 48 hours.
Location and service area
We serve projects across Allentown and its metropolitan area.
