Vol 55, No 4 (2018)

We study the influence of "pile-rocky massif" contact under the action of axial compressive loads on the basis of the experimental results and numerical simulations. It is shown that, in predicting the behaviors of bored piles in rocky grounds under the action of axial compressive loads, it is necessary to take into account the influence of "pilerocky massif" contact both on its load-carrying capacity and on its settlement. For the numerical analysis of pile settlements, it is proposed to use the shear contact stiffness.

The fully grouted bolt is a convenient, effective, and economic technology for slope reinforcement. A new nonlinear Hoek-Brown strength reduction method based on the characteristics of a jointed rock mass is proposed. By analyzing the change in slope failure mode, effects of the bolt head, spacing, inclination, and arrangement on the stability of the slope are investigated. Results show that the shear strength of the bolted structure is contributed by the axial force and transverse shear force. The transverse shear force of bolts increases the slope stability and improves the bolt bearing capacity; the bolt head is important in determining the failure mode and factor of safety of a bolted slope, while the size and material parameters of the bolt head are not important when the size of the bolt head is sufficiently large. The vertical bolt spacing has a nonlinear effect on the slope safety factor, and the failure mode of the slope changes from deep sliding to partial deformation along the joint surfaces with increase in the bolt horizontal spacing. With increase in the bolt inclination angle, the safety factor first increases and then decreases, and the maximum safety factor occurs when the bolts are placed horizontal or perpendicular to the slip surface. The slope safety factor decreases with decrease in the bolt length. An optimal design of longer bolts at the bottom and shorter bolts at the top is recommended. A shear zone forms from the intersection of two joints to the slope surface in the upper part of the slope.

We study the anisotropy of deformation properties of the pebble-gravel soils and reveal the influence of orientation of large fractions on the deformability. The experiments were performed according to two schemes: particles larger than 10 mm were placed either vertically or horizontally. It is shown that the pebble-gravel soils have anisotropic deformation properties. By taking into account the anisotropy of the properties, it is possible to make the numerical analyses of the stress-strain states of rock-fill and earth dams closer to the in-situ data on the deformability of dams in the course of their construction and operation.

We consider various approaches to the solution of the problem of computer processing of the results of geological engineering investigations aimed at the determination of the characteristics of soils at points of the massif lying outside the sections made according to the data of the wells. We develop an algorithm and a program for processing the accumulated geological engineering data based on their interpolation and averaging over a net of triangles with vertices at the points of location of the wells. The efficiency of the proposed procedure is illustrated by the "geometrization" of the results of karstological investigations in the area of construction of a hydroengineering structure with construction of the sections, containing, in particular, the data on the variations of thickness of the protective film preventing the dissolution of sulfate rocks.

A hollow cylinder apparatus was used to simulate the stress paths induced in traffic-affected ground. A series of undrained shear tests was carried out. The inflection points on generalized shear strain curves were used to establish a damage criterion, which distinguished different damage characteristics under different stress levels. Tests were carried out to elucidate the effect of different initial deviator stress on soil shear stiffness. The variation of shear modulus with vibration times under different dynamic stress ratios was analyzed. Stiffness degradation and plastic cumulative deformations of soil were analyzed for the case where the initial deviator stress was equal to zero. The prediction models models can be used to investigate stiffness degradation patterns and axial plastic cumulative deformation patterns.

The three-dimensional transmission of ground vibration subjected to a point load moving along a beam is investigated theoretically, where the beam is located inside a layer and parallel to both the ground surface and bottom of the layer. According to the specified boundary conditions along the beam and layer, analytical solutions of displacement are obtained in the wave number-frequency domain employing a Fourier transform, and the space-time domain response is obtained employing a fast inverse Fourier transform. Numerical results show that, for a constant moving load, the ground vibration has a typical low-frequency feature, and vibration in the horizontal direction should be considered when studying the effect of an underground moving load on environmental vibration.

The performance of a vertically-loaded floating piled raft foundation in very soft and deep layers of compressible subsoil, in terms of its ability to control key factors such as bending moment and pile-raft coefficient, was presented and discussed in previous research. The other critical factor that needs to be evaluated is the angular distortion of the foundation. This paper presents the effectiveness of the piled raft foundation system in controlling the angular distortion of the foundation. A comprehensive analysis of this proposed foundation system for various pile lengths in soft compressible subsoil was carried out. Different pile groups with 9 × 9 arrangement of piles were loaded vertically. A total combination of 45 pile group cases with different pile lengths, pile spacing, and raft thicknesses was analyzed. Results showed lower angular distortion for the proposed foundation system, which indicated that a piled raft with varying pile lengths is most efficient in controlling angular distortion as compared to piled rafts with equal pile lengths.

Numerical modeling of the thermal interaction of sandy fill and frozen base soils was performed in order to determine the role of natural and technogenic factors in the formation of the soil temperature regime for the Eastern-Messoyakh deposit. The heat-engineering calculations revealed a significant effect due to large snow accumulations and meltwater infiltration into the fill soil. The use of reference climatic indices in the calculations without taking account of the observed increase of air temperature causes the predictive models to deviate from the actual data.