An algorithm is proposed for solving difference problems of subsurface hydromechanics by the alternating triangular method ( ATM ). For second, third, and mixed boundary-valued problems of subsurface moisture transport in the elastic regime, we use an improved ATM generalization scheme, which has been tested by the authors in application to the first boundary-value problem. The proposed algorithm can be applied to various problems of subsurface mass transport.The most efficient methods for solving problems of subsurface hydromechanics in nonhomogeneous anisotropic porous media are numerical, such as the finite-difference method. The application of this method replaces the original differential problem with a system of grid equations, which is solved by both direct and iteration methods.The alternating triangular iteration method (ATM) proposed by Samarskii [4] and developed in [1, 2, 6] has a fast rate of convergence for the solution of elliptical grid equations. It is also applicable to the solution of unsteady seepage problems with mixed boundary conditions on a nonuniform grid.

The paper presents a mathematical formulation of the problem of drainage of nonhomogeneous soil by a regular system of horizontal drains in the framework of hydrodynamic and hydraulic theories. Algorithms for approximate solution of the problem are described. Comparison of numerical and analytical solutions substantiates the theoretical depen&'nces.The paper analyzes numerical results obtained for moisture transport processes in a saturated/unsaturated porous medium with a regular system of horizontal drains under the action of pressure, gravity, and sorption.

We consider the problem of steady-state oscillations of a plane body with an inclusion. A solution algorithm is constructed. Computational experiments are described, which establish the applicability of the proposed procedure for analyzing the effect of defects inside the body on wave fields excited by ultrasonic sources.Problems of nondestructive ultrasonic testing involve analyzing the effect of various defects inside the body on the wave fields excited by special sources. In this paper, we consider the plane problem of steady-state oscillations of a rectangular body f~ = {x = (x 1, x2):0 _< x 1 -< 1, 0 _< x 2 _< d} (see Fig. 1) with a rectangular inclusion 91. The inclusion is an elastic body whose characteristics are different from those of the main body. The method of summation identities on a nonuniform grid is applied to construct a difference scheme for the problem. The system of grid equations is solved by the Seidel method.

The influence of the humic preparation and pesticides on dynamics of soil carbohydrates and the soil structure of ordinary chernozem during the cultivation of winter wheat and chickpeas was studied. A positive trend in the growth of the structural coefficient was observed in all variants. This dynamic was confirmed statistically when a humic preparation and pesticides were used together: the difference with the control after treatment was 1.54% (2019). A decrease in the number of water-resistant units from 87.4 to 56.6% was observed on the control during the entire field experiment. There was a statistically significant increase of water-resistant aggregates by 1.9-5.4% when pesticides are applied together with a humic preparation. The growth of the aggregate water resistance criterion (API) from 6.0% to 17.2% was observed in the variant with a humic preparation. The dynamics of soil carbohydrates in all variants in 2017-2018 was insignificantly expressed. The sharp increase in the content of carbohydrates in 2019 is probably associated with a change of culture in the crop rotation link from winter wheat to chickpea. The amount of carbohydrate compounds varies from 1.13 in the control to 1.26% in the variant with the combined use of pesticides and a humic preparation.

The results of many years of research on the individual and complex effects of biologically active substances on the structural state and enzymatic activity calcic chernozem – humic preparation Lignohumate and microbiological fertilizer “Baikal-EM” – are presented. It was found that biologically active substances contribute to an increase in enzymatic activity, humus content and an improvement in the state of the soil structure. When both preparations are applied directly to the soil, the maximum effect and statistical reliability of this effect on the structural characteristics of the soil are shown even under extremely unfavorable weather conditions. At the same time, the structural coefficient during the study period increases from 1.5 to 2-2.7 in comparison with the background variant, which makes it possible to assess the structural state of the soils as “excellent”. In general, the activity of enzymes during the research in the cultivation of winter crops tended to stable growth. The cessation of the application of liquid complex fertilizers and the transition to a spring crop led to a decrease in the activity of enzymes and their return to background values.