Vol 52, No 6 (2016)

It is experimentally found that shut-in pressure conforms with the fracture initiation pressure if the fracture surfaces are uniformly loaded by fluid. The article shows that equaling minimal stress and shut-in pressure in local fractures results in overestimates. The error depends on the length of a hydrofracturing facility and is high under low compression in rocks (5–10 MPa). The authors put forward decisions aimed at improvement of accuracy and enhancement of information content of hydraulic fracturing in the in situ stress measurement.

The article describes physical simulation and mathematical modeling of influence exerted by injection of thermogel on configuration of water flow in water flood recovery. Recovery of oil, especially viscous oil, with such method features unstable displacement front and formation of water fingers that eventually turn into a net of water channels directed toward the lowest flow coefficient between wells. Most of oil remains immobile and is in dynamic equilibrium with the displacement water flow. The authors show that injection of thermogel in a reservoir between wells expands displacement front at the late stage of mining, which allows enhancement of oil recovery factor.

Internal pressure tunnels and wells that are mainly used to transfer water from dam reservoirs to electrical power plants in rivers downstream are considered among the power plant’s permanent facilities. In order to design reinforced concrete structures in these tunnels, recognizing the concrete lining behavior and interaction between rock mass and concrete and also the effect of internal pressure on the concrete shell and rock mass is of great significance. One of the important and effective issues in inner lining forces is their filler type. In this paper, using the finite difference method by the FLAC software, the analysis of Sardasht dam water tunnel which has been filled with mineral pumice in falling zones has been carried out. Results indicate that by increasing the falling zone thickness while the lining is porous or non-porous, the inner forces are decreased.

Considering features of wave prefracturing (microfailure) of rocks under blasting, the authors put forward a new investigation approach with the use of relations of dynamic elastic stress distribution in rocks and theory of cracks. The obtained relation to estimate prefracturing zone size in relatively solid rocks under confined explosion involves pressure of gases in explosion chamber, rock pressure, crack resistance of rocks, characteristic dimension of natural jointing (presence of defects) and deformation characteristics of rocks. It is shown that dimension of prefracturing zone in rocks depends both on natural and production factors and can differ by a few times.

The factors that have significant influence on efficiency of rotary–percussion rock drilling with downhole machines are discussed. The results obtained in physical simulation of dynamic driving of rock-breaking indenters in rocks are reported. The results are analyzed from the standpoint of the phenomenon of alternating response of rocks to dynamic impacts.

The authors review key approaches to designing small-size air drill hammers. The approach to increasing impact capacity of air drill hammers by means of buildup of blow frequency is substantiated. The experimentally obtained and compared characteristics of air drill hammers equipped with the heads made of steel and titanium prove feasibility of increasing impact capacity by means of using low density materials. The technology of thermal treatment of a titanium-alloy hammer head is described, and its laboratory testing results are reported.

The analysis of methods to account for stripping time difference at the stage of determination of limits in deep open pit mining reveals advantages and shortcomings of the methods and provides a principled approach to determination of a discount ultimate strip ratio for the most representative geological and geotechnical conditions of diamond-bearing ore bodies in the form of single pipes. Discounting of marginal strip ratios is based on adding the common formula with an average mean discount coefficient represented by a correlation of mining rate decrease, stripping zone height and highwall slope angle. It is shown that target variation of the factors included in the discount marginal strip ratio allows considerable influence on depth and efficiency of open pit mining.

The article describes the applied research findings on selecting a resource-saving technology to ensure drastic reduction in loss of high-grade Kyshtym quartz. The economical–mathematical modeling yields relationships between mine efficiency, ground conditions, mine design and technology factors, and the optimal variant of a combination mining technology is determined using the maximum profit criterion. Full-scale physical simulation of closed-spaced charge blasting effect on reduction in overgrinding of quartz is discussed. Drilling and blasting pattern for experimental breaking of quartz by explosions is determined.

Using Hammett indicators, X-ray fluorescence spectroscopy and atomic force microscopy, the authors analyze influence of high-voltage nanosecond impulses on structure and chemistry of surface and on process properties of calcium-bearing minerals. As a result of impulse energy inputs for t ≤ 30 s, the change in the structure and functions of mineral surface includes: enhancement of electron–donor capacity and formation of structural defects on the surface of fluorite, and enhancement of acceptor capacity of the surface of calcite and scheelite. Pre-treatment of mono-mineral samples by electrical impulses increases flotation ability of calcium-bearing minerals: increment in froth recovery makes 10–12% for scheelite, 5–6% for fluorite and 7–8% for calcite.

The article presents data of experimental studies into magnetic properties of iron-bearing sulfide and nonsulfide minerals under radiation and heating. It is found that bulk magnetic susceptibility has increased more than 100 times in pyrite and 6 times in bauxite ore. Usefulness of radiation-and-heating magnetization in modification and processing of bauxite and tin-bearing minerals is demonstrated.

The discussed challenge and its prospects in mining geoinformation science are connected with Big Data concept—flows of large sets of various data on mining. The authors describe Big Data technology and its general implementation on mini-clusters using Hadoop and MapReduce with case studies presented.

The presented system is intended for multistage hydraulic fracturing in long open holes of any orientation to create transversal fractures with a radius to 5 m in soft and medium-hard rocks. The downhole system has an inbuilt transport unit. This fracking equipment uses chemically active fluids generated in the fractured interval by mixture of two components injected in individual high-pressure hoses.

In the published version there is an error in the title. The present form in this erratum is the correct: Optimal Cutoff Grades Modeling for Open Pit Mining Operations during Mining Sequences.