In accordance with new regulatory documentation (ПНСТ 542-2021) for auto road engineering, the auto road earthwork should be constructed with non-frost-susceptible and/or stabilized soils. As most of the soils available in the Republic of Tatarstan are frost-susceptible and highly frost-susceptible, we are into experiments for unsuitable soils recovery. Soil bearing capacity as subgrade modulus of clay and loamy waterlogged soils does not exceed 15-20 mPa. Be adding inorganic binders to these types of soils we enhance subgrade modulus of constructional layers (Ev2) up to minimum 45 mPa, which meets the EN European Standards requirements.
The new trend for enhancement of soils from borrow pits and excavations is normalization of their grading curve. The photographs represent auto road dredged soil before and after addition of very coarse soil and 1% of inorganic binder.
After the enhancement of earth roadbed properties, Ev2 raised up to 80 mPa and above suggesting that future auto road constructions may be successfully altered.