Vol 56, No 5 (2019)

The possibility of numerical modeling for determining the parameters of karst deformations depending on the confining bed thickness over karst rocks is considered. A method for estimating the parameters of karst manifestations according to the modeling results using verified calculation complexes is presented. The proposals are formulated for the definition of constructive measures of anti-karst protection.

Patterns of soil consolidation with significant filtration and viscous resistance to volumetric deformation are considered. Joint models were characterized, issues identified and practical calculations of the consolidation of water-saturated boggy soils were presented. The conceptual contradictions for the viscous-elastic-plastic model were analyzed using the Bingham nonlinear water-saturated body model of the KONSO program and the Plaxis Soft soil creep model. The method of the correct determination of creep and nonlinear viscosity parameters during the compression-consolidation testing was presented.

As a remedial measure against slope failure, an anchored micropile structure (AMS) was proposed comprising a conventional micropile structure (CMS) and anchor tieback. Numerical investigations of performance of the AMS and CMS were performed. Improvement was observed in the displacement field of slope reinforced by AMS. The rotation deformation of CMS is replaced by flexure deformation in AMS. Displacement of AMS is less than CMS. The tieback acts in both deformation control and stress optimization. The reduction in extreme value of bending moment is equal to 35%. At axial force, the sharing ratio was decreased from 2.43:1 to 1.25:1.

Cement kiln dust (0%-27%) was used to stabilize collapsible loess. Compaction, compressive, collapsibility, and strength tests of stabilized collapsible loess were conducted. X-ray diffraction and mercury intrusion porosimetry tests were also carried out to study the characteristics of microstructural and mineral composition for loess before and after modification. Results indicate that compression and collapsible coefficients decreased with increase in cement kiln dust (CKD) content. The unconfined compressed strength is also enhanced by CKD, showing an exponential function, and curing time has a significant impact on later strength. The mineral composition of loess is changed by adding CKD, and a better packing and more stable soil structure are formed.

Based on the experimental and theoretical studies, as well as observational generalizations, a procedure for assigning a soil deformation modulus of the various-area foundation bases is proposed. The field soil test data obtained using stamps of various sizes and their comparison with the settlements of high-rise buildings erected on slab and conditionally continuous slab-pile foundations with an area of up to 2,000 m² allow predicting the actual settlements of the large-area foundations by using a layer-by-layer summation method.

An engineering method of calculating the ultimate settlement of a single hanging injection pile of length from 3 to 5 m in clayey soils, including weak soils, is proposed. The method takes into account the linear and nonlinear dependences of the settlement on the external load and is based on taking into account the operation of the bottom end and the lateral surface of the injection pile. The obtained results can be used to solve the complex problem of evaluating the deformations of individual and strip foundations after they are strengthened by injection piles in the reconstruction of buildings as well as new construction.

Profile zoning is a precondition for stability analysis of tailings embankments. As a consequence of technology progress in the beneficiation field, the size of tailings grains is getting smaller in recent years. Accordingly, traditional methods of profile zoning, which suit medium-coarse grained tailings, are no longer applicable for fine grained tailings. The results showed that drainage consolidation was difficult in the embankment. The embankment, composed of tailings, had a poor stability without the protection of incrustation, which consisted of medium-coarse grained tailings. A new profile zoning method is presented. In this method, degree of consolidation is regarded as the only basis for profile zoning and it shows that the adjacent boundary lines between dam sections intersected the slope surface of the embankment.

We present the results of experimental investigation of the temperature dependences of the stress-strain properties of freshwater ice and pykrete. It is shown that, as the temperature of freshwater ice decreases from −1.0 down to −6.0 °C, the ultimate conditionally instant and long-term strengths of freshwater ice increase according to a linear law, whereas the temperature dependence of the viscosity coefficient is nonlinear. For a fixed temperature, the viscosity coefficient of the natural underground ice increases with its density and strongly decreases as the load increases.