The Newcastle Flat Rigid Dilatometer (NDMT) is a new in-situ soil testing device developed in 2001 for direct measurement of the in-situ characteristics of soils such as strength, stiffness, deformation etc. It is quite simple, robust and produces repeatable data with no hysteresis. The NDMT loads the soil with a relatively rigid piston of 3 mm thickness in lieu of only 0.2 mm thick membrane of Marchetti Dilatometer (MDMT), thus creating a loading environment closer to that of the real-life foundations. The NDMT is more sensitive than the Marchetti dilatometer in measuring pressure and the corresponding displacement because of the instrumented rigid plate and therefore has the potential to detect variations in soil strength or stiffness with depth more accurately.

This research paper is based on the NDMT testing at three locations in the cohesive soils of Lahore (near Thokar Niaz Beg) up to 8.0 m depth below the natural surface level. In order to correlate the NDMT test results with those of other conventional methods, SPTs were carried out and undisturbed soil samples (UDS) were recovered in thin walled Shelby tubes at locations close to the NDMT testing locations. The undisturbed soil samples were tested for grain size analysis, Atterberg limits and unconfined compression strength in the laboratory.

The NDMT indices viz. material index (I_D), dilatometer modulus (E_D), and horizontal stress index (K_D) have been evaluated from the corrected load – deformation curves of each NDMT test. Subsequently, new correlations have been developed between dilatometer indices and conventional soil characteristics such as classification, undrained shear strength and elastic modulus, for the Lahore clayey silts/silty clays.