Прочностные характеристики грунта при проектировании объектов лесной инфраструктуры

Soil shear resistance is one of the key characteristics of soil that affect its bearing capacity. Errors in its definition can lead to significant economic damage. Overestimation of experimentally determined values of shear indicators leads to the fragility of foundations and the destruction of structures, and underestimation leads to additional construction costs.

The article discusses the validity of the application of various methods used to determine the shear strength of soil, the accuracy of measurements obtained through these methods, and the interpretation of the results. The analysis focuses on the determination of the indicators of adhesion and the angle of internal friction using the method of consolidated-drained cut and unconsolidated (fast) cut is carried out. The comparative results of laboratory determination of strength properties using different methods (each regulated by GOST standards) show that the adhesion of the same samples differs several times, and also does not always correlate with field values. Additionaly, it is worth noting that replicating the "undisturbed" soil structure, which is akin to natural conditions (i.e. reproducibility of conditions of natural occurrence), is nearly impossible in laboratory settings., The difference in density and humidity of laboratory and field samples in sandy soils is especially significant. At the same time, the difference in the measured adhesion indicators for field and "prepared" samples was in some cases thousands of percent, the angle of internal friction was tens of percent. The article also reveals inconsistencies in the dimensional aspects of the Coulomb equation used to determine the tangential stress, and shows errors in determining shear characteristics that arise due to the discrepancy between the sample dimensions (height and diameter) and natural conditions. The drawbacks of counducting field tests of soils for shear according to standard methods are analyzed.