Том 54, № 6 (2018)

The existing methods of calculating pile foundations from the standpoint of degree of detail, accessibility, and computing speed are discussed. The basic mutual influence functions of piles for performing calculations by the method of mutual influence coefficients are examined. An improved influence function is proposed and practical recommendations are made for performing calculations by this method. Calculations and a comparison of the results are presented for pile groups ranging in size from 4 to 1296 piles in the elastic half-space model by the method of mutual influence coefficients and the method of finite elements.

A method is developed for calculating the settlement of single double-bladed metallic screw piles in clayey soils for the foundations of temporary buildings. The method is based on the use of a patented design of a screw double-bladed pile and takes account of the nonlinear load dependence of its settlement. It is established that for clayey soils with semi-solid consistency the discrepancy obtained between the experimental final settlements of double-bladed screw piles and the computational data obtained by the proposed method does not exceed 20-30%.

The methods of calculating and designing pile-raft foundations are analyzed. Certain inconsistencies resulting in inefficient designs of foundations for multistory buildings are shown to arise in using the normative provisions. Engineering methods of determining foundation parameters in calculations based on the maximum admissible deformations and a method of evaluating the effectiveness of these methods are proposed.

An artificial crust layer formed by in-situ stabilization combined with pre-stressed pipe piles over soft ground has been proposed to reduce foundation settlement in road construction. To analyze the effects of the artificial crust layer, the field measurements from a road project, including the strength of field stabilized soil, settlement and the load distribution between soils and piles were investigated. The results showed that the ratio of 28-day field unconfined compressive strength to laboratory strength ranged from 0.28 to 0.45 at the same stabilized agent. Additionally, the artificial crust layer had a greater compression modulus and strength compared with soft clay, so that the deformation of stabilized soil only accounted for about 5% of the total settlement. The foundation consolidation speed was slower because of the impervious properties of the artificial crust layer.

The modeling of the "reservoir with oil – system "GET" – soil massif" system for 1392 random trajectories of air temperature, wind speed and snow cover thickness changes for two years is carried out. It is shown that the result temperature distribution in the soil massif has the form of normal distribution.

Soil's electrical properties are the parameters of natural and artificially created electrical fields in soil and are influenced by distribution of mobile electrical charges, mostly inorganic ions. We aim to determine practically-applicable relations with which to determine soil moisture content and void ratio based on electrical resistivity measurements taken from two different sites in Penang Island. In this study, analysis was conducted to determine the relationship between soil electrical resistivity, moisture content, and void ratio. Moreover, an initial analysis was conducted to determine the variation between the coefficient of gradation with moisture content and void ratio for all data. The developed empirical correlation found in this study can be used as an initial guideline for the further study of tropical soil.

Despite all efforts made to study and deal with errors induced during pressure cell measurements in soils, there is still a vast uncertainty remaining in this field. One of these errors results from the grading of the surrounding media in which the pressure cell is installed. In this study, the grain size of the cell installation media and its effects on the measurements and the results fluctuations are evaluated. For this purpose, PFC-2D software was used to numerically simulate the laboratory models and compare their resultant outcomes as well as studying the accuracy of the numerical modeling. Applying a trial and error procedure and considering simulation restrictions, an appropriate conformity was achieved between numerical simulation and laboratory results. Results of the numerical modeling of fine- and coarse-grained materials showed an average error of 25% and 50%, respectively. The results indicated that in smaller particle sizes, a more uniform pressure is developed in the pressure cell.