卷 54, 编号 5 (2017)

The results of an investigation of practicable contours of horizontal underground mine workings and their safe laying depth are presented. The absence along the contour of points where the tangential normal stress exceeds the ultimate strength of the enclosing rock in tension and compression can serve as a criterion for determining the admissible depth.

Tunnel excavation causes stress changes in the ground, leading to soil movements that may affect the safety and serviceability of existing pipelines. Although the tunnel-soil-pipe interaction has attracted increasing research attention, previous studies primarily focused on the responses of existing pipelines due to tunneling in sand. In this study, an extensive numerical parametric study with 540 numerical runs is conducted to investigate the effects on existing pipelines due to tunneling in clay. Soil responses to uplift and downward pipe-soil relative movements are explicitly simulated. Parameters considered in the tunnel-soil-pipe interaction include ground settlement profile, pipe dimension, material properties, pipe burial depth, and undrained shear strength. A dimensionless plot of relative pipe-soil stiffness and the ratio of maximum pipe curvature to ground curvature are developed to directly estimate pipeline curvature due to tunnel excavation in clays. When the relative pipe-soil stiffness is less than 1×10^-4, the existing pipeline deforms with tunneling-induced ground settlement. The existing pipeline is relatively rigid when the pipe-soil stiffness is larger than 10.

The results of inspection as well as engineering-geologic and geodesic studies of the site of a deformed apartment building are presented. The results of computer modeling of the combined work of the soil base and the building resting on it are examined. The reasons for the deformation and failure of the structural units are determined.

This paper explores geological processes that explain the causes of differential settlements of building foundations on loess-like collapsible soil. Recommendations have been developed to eliminate differential settlements of multi-storey buildings on foothill areas, including measures to restore a building's vertical position, to reinforce the foundation soil to prevent settlement, and to eliminate foundation moistening. The proposed measures were approved upon the elimination of unacceptable deformations and the stabilization of settlements of existing 9-storey buildings of a residential complex in the Alatau district of Almaty, Kazakhstan.

A complex combination of permafrost rock masses with different forms of bedding and high seismic activity in regions of Northern Trans-Baikal is examined. The dependence of the geothermal processes in the cryolithozone on the character and activity of tectonic structures is described. The associations of the seismic properties of rock with the physical-mechanical properties and temperature are shown. Rock types with specific engineering-seismic-geocryological features are presented. A classification of magnitude changes compared with the initial values in regions with different types of permafrost rocks as well as a method of seismic microzoning in the cryolithozone taking account of defined predictive elements, obtained by studying the relations of the elastic characteristics of frozen rock to their physical state, temperature, and moisture content, are presented.

The potential for additional cooling of the frozen foundation of a building in view of global climate warming is considered. Alternative installations in the heat insulated basement and variations in the ventilation conditions of the cold basement are proposed. The calculations take into account the increase in the temperature of the air and soil in the zone of zero annual amplitudes since 1969, when the building was designed, to 2050.

Biopolymers, which are microbially induced polymers, can be used as an alternative material to improve engineering performance of soils. In this paper, a laboratory study of 0.075-1.0 mm size sand and biopolymer (i.e., xanthan gum) mixtures with various mix ratios (0%, 0.5%, 1.0%, and 1.5%) was performed. The materials, specimen preparation, and test methods are described, as are the results of a suite of permeability, odometer, unconfined compressive, and triaxial shear tests. The results suggests that specimen formation in the way used here could reduce permeability and increase compressibility, strength, and deformation characteristics in terms of stiffness.