Shear strength of the permafrost soils salted during drilling piles construction

In some cases, when drilling piles are installed in permafrost soils, mixtures are made with chemical additives to ensure concrete hardening. During such piles installation heat and mass transfer between the concrete mixture and the soil occurs, which lead to artificial base salinization. Presently the regulator does not recommend to use such piles in the cryolithozone due to insufficient knowledge and lack of reliable calculation methods. The purpose of the work described in this article was to refine the methodology for the bearing capacity of drilling piles in artificially salted permafrost soils determining. Comparative analysis has shown the insufficient accuracy of the standard method for shear strenth determining. Proposals to refine the methodology for the determining bearing capacity of piles by introducing an operating conditions coefficient γsh,sal assumed to be equal to the ratio of the calculated frozen soil shear strenth in artificially salted and unsalted conditions are made. The maximum long-term artificially salted soil shear strenth is proposed to determine depending on the salinity degree, and the pore solution concentration to determine by calculation using a known model. The methodology was tested using data from static tests of full-scale piles by calculating a set of coefficient values for sandy soil and a concrete mixture including sodium methanoate as an antifreeze component and a multifunctional modifier. It is shown that the improved methodology makes it possible to increase the calculation reliability.