INFLUENCE OF CHANGES IN THE HUMIDITY CONDITIONS OF THE SOIL MASS AND PRESSURE TRANSMITTED ON IT FOR THE IMPLEMENTATION OF THE COLLAPSING PROPERTY OF THE LOESS COLLAPSING SOILS AND FORMATION OF NEGATIVE FRICTION FORCES PN

It is executed the materials analysis on forming of collapsing properties of eolian sedimentations (Obrychev, Abelian, Krytov, Mustafaev and other). On the executed analysis is set, that physical properties of loess collapsing soils, their regional features (εse, Pse, Wse, Sse,g, Sse,p) depend on genesis of these basic sedimentations. In present literary sources (Abelian U., Krytov V… DBN) all regional descriptions of loess collapsing soils are accepted from data of experiments results over of which are brought in materials of engineer-geological researches or executed directly by authors. In this article is given a shot to express basic and regional descriptions of collapsing soils analytical dependence of εse=f(Wt), where Wt – is time-history of humidity of loess collapsing soil in the process of infiltration of water in loess soil; determined with a concept durability of cementation connections – «Ц» and dependences of this durability of humidity of Ц= f(W); to show dependence of change of natural pressure of «Рg» on the change of soil humidity: to give interpretation or renew the existent utterances of leading specialists to this direction about critical humidity of Wкр (Wпр) and about initial sagging pressure of Рse=Ркр; to offer analytical dependence of forming of negative friction forces – Рп on the side of barrel of piles depending on the humidity change of collapsing soil – Рп= f(W). It is given suggestions on calculation of intermediate values of strength and deformation indexes (∁, ????,Ε) of collapsing soil being in the range of humidity 0≤W≤Wsat. On the calculated intermediate values ∁_W,φ_W,Ε_W determine the soil friction forces on the side surface of the pile shaft. Whereas, at determination of bearing strength of piles in loess collapsing soils of soil friction forces that is transmissible on a pile shaft of «f» are determined at the complete soakage of the loess soil cut through by a pile and negative friction forces of soil on the side of pile shaft are too determined on descriptions of moistened soil, i.e. in first case f=f_sat (under I_L=(W_sat-W_p)/I_p ), in second case (τ=σ_(sat,zg)⋅tg⁡〖φ_sat 〗+∁_sat). Because the process of transmission of soil friction forces on the side of pile shaft differs in this case only by the transmit-direction of these forces, then offered authors: at calculation of bearing strength of pile in loess collapsing soils of soil friction force within the limits of the cut through loess collapsing layer not to take ????=into account 0, that goes to reserve of bearing strength of pile, and soil friction forces on the side of pile shaft at collapsing of layer to equate Рп=0, because ????=0, and ????=????. Then spores about operating of negative friction forces on the side of pile shaft – Рп – and the methods of its calculation (Р_п=U∑▒τ_i h_i) do not arise up, in fact existent formula does not reflect the physical process of display of negative friction forces – Рп. It is suggested to calculate (if «necessary») forces of negative friction authors at the incomplete soakage of layer depending on intermediate humidity (????????) calculating preliminary intermediate values ∁_W и φ_W.