Vol 53, No 5 (2016)

This article considers the successful implementation of a deep foundation pit next to existing buildings, which experiences settlement and damage to load-bearing structure during the course of its excavation. An analysis is presented of the causes of building settlement and deformation. Steps are described to stabilize settlement and to reinforce foundation beds in damaged buildings. Additional settlements in adjacent buildings, calculated using the finite-element method, are compared to monitoring results upon final completion of the foundation pit.

The development of a Gersevanov Institute procedure is given for analyzing bed settlement under a slab foundation, with consideration of the foundation shape, uneven load, and bed nonuniformity. In the proposed procedure alternative, which has been adapted for the analysis of foundation slabs on a nonuniform rock bed, the load distribution under the slab bottom is taken from the results of a finite-element analysis of a building structure on a base assumed to be absolutely inelastic. Implementation of the analytical procedure is shown using the example of calculating the settlement and deformation of a high-rise building slab, for which a "weakened" area was identified in the bed during surveys. Stochastic simulation of additional "columns" of geological engineering boreholes is carried out to estimate the impact of insufficiently complete information on the properties of the rock mass. The impact of bed nonuniformity on the results of analyzing settlement, slab tilt, and forces within the slab are analyzed.

A closed-form solution for the limit pressure of undrained cylindrical cavity expansion in anisotropic clay is provided. The solution considers the effect of anisotropic strength and initial in-situ stress. The cavity-wall limit pressure under an isotropic initial stress (K = 1) was larger than the anisotropic initial stress (K ≠ 1) and holds true for all anisotropic strength ratios. The cavity-wall limit pressure increased linearly with increasing anisotropic strength ratio. The cavity-wall limit pressure was a minimum for a polar angle θ = π/2.

The results are presented of integrated strength and stability tests of fortress structures at the Moscow Kremlin and adjacent structures in the section from the Troitskaya tower to the Spasskaya tower. Results of geotechnical simulation are analyzed and geodetic observation archive materials are presented. A need is demonstrated for activities to protect beds and foundations.

Microtremor array measurement surveys were performed in three locations to determine the shear wave velocity profile down to a depth of 30 m. The shear wave velocity results from the data acquisition of the multichannel surface wave method were compared with the microtremor array measurement in terms of the shear wave velocity profile as a function of depth. The correlation indicated that the shear wave velocity values range from 200 to 300 m/s and showed a significant velocity contrast at a shallow depth.

The factor of safety is one of the major aspects for designing specific structures like embankment, landslide, and artificial slopes. In this context, some huge damages are particularly reported due to the effect of earthquakes. In this paper, 700 slopes were designed based on the limit equilibrium method, and relevant factor of safety values were obtained. In the modelling process, the parameters with the greatest effect (slope height, slope degree, soil cohesion, and internal angle of friction with peak ground acceleration), were considered as predictors or model inputs. As a result, the factor of safety under the impact of seismic motion is significantly reduced when the peak ground acceleration increases. A multiple regression model was developed. Coefficients of determination for the training and testing datasets indicate the excellent ability of the proposed model to estimate the seismic factor of safety. Peak ground acceleration and soil cohesion were obtained as the parameters with the most and least effect on the factor of safety, respectively.

Methods of determining the total deformation modulus of frozen ground are analyzed. Published data and the results of more than 800 compression tests, conducted by the authors in the course of engineering research in different regions of the cryolithozone of Russia, are colligated. It is shown that GOST 25100-2011 and SP 25.13330.2012 specifications are inconsistent and there is no justification for subdividing frozen fine-disperse soils into plasto- and solid-frozen. Soils are given for including in the revised SP 'Foundation beds and foundations on permafrost' the requirement that foundation beds on frozen fine-disperse soils be reckoned in terms of both groups of limiting states — deformations and carrying capacity. Suggestions are given for determining the deformation modulus by means of compression tests.