Home – Home – Jornals – Advanced Search

Soil moisture determines water and thermal regimes of the soil and the surface boundary layer of the atmosphere. It is an important factor in hydrology, ecology, climatology, meteorology, and agriculture. Nowadays, soil moisture is mostly measured with satellite remote sensing systems. The data measured by a satellite during the warm period of 2011-2012 years has been compared with data direct measured at 5 networks of weather stations in the USA. The aim of this study is evaluation of the soil moisture satellite data, finding regularities, anomalies and their causes, and development of satellite data quality control procedure for data assimilation system. Satisfactory agreement between two kinds of data observed has been shown. Areas with good and poor dependence were identified. These results can be used in other regions with similar underlying surfaces and orography. Criteria for satellite data quality control procedures are proposed.

The approach to normalization of the vegetation index calculated from measurements of the spectroradiometer MODIS is discusses in the paper. To do this, the normalization involves additional spectral channels of a spectroradiometer, based on the calculated cloud and snow indices allowing one to build a cloud mask and to allocate time periods of the presence of clouds. The built model for vegetation index dependency on the temperature allows further improvement of the form of time series of the vegetation index. The results of the application of the proposed approach to the real measurements are discussed in the paper.

The article reports data of a lab test of directional hydraulic fracturing carried out on a block made of organic glass. A fracture across a hole is created by means of additional shearing stress applied to the hole walls within the interval of the fracture. It is found that seismic emission under hydraulic fracturing has no bearing on destruction of the model material but appears after the fracture completion.

The theoretically evaluated multi-disciplinary approach enables determination of stress state of a coal-rock mass in the area of coal cutting using a package of geomechanical and geophysical information. The approach is based on successive solutions of two inverse problems in the framework of a geomechanical model: coal-bed tomography and assessment of horizontal components of external stress field. The numerical experiments demonstrate resolvability of the inverse problems given appropriate monitoring system ensures sufficient seismic coverage of a coal-bed in the domain of steep spatial gradients of elastic waves and the presence of regular composition in the frequency range of the order of hundreds of hertz in the sounding signal generated by a cutter-loader and/or other coal-face work machinery.

The approach to numerical modeling of physical specimen loading considered by the authors using the discrete element method enables describing ability of rocks to accumulate and release elastic energy. The model specimen is a package of particles characterized by viscoelastic interaction with dry friction. The outer layer particles are connected by elastic springs. On the whole, the model specimen is an element of a medium capable of accumulating a part of energy of deformation in the form of internal self-balanced stresses. Numerical modeling of the specimen compression is performed, and the accumulated energy is assessed. It is shown that clusters form in the medium, and sliding along the boundaries of these clusters causes discontinuities in deformation curve. Also, the discontinuities are possible under stress relaxation after unitary dynamic effect on the specimen. There is a good agreement between the numerical and experimental results.

The scope of the studies embraces statistical and mechanical properties of surface of different kind crystals of salt rocks. Fractal dimension, hardness and elasticity moduli of such crystals are determined. The article gives estimates of fracture toughness and wettability of salt rock crystals as function of fractal dimension of the crystal surface microrelief.

Under computational investigation is the process of sequential growth of hydrofractures under conditions of plane strain. The working fluid is perfect and viscous. The authors analyze influence exerted on parameters and trajectories of growing fractures by spacing of the fractures, external compression field, fluid flow rate, fluid viscosity and leakage flow rate.

The process of crack propagation in coal face area is considered as an informative sign of coal and gas outburst hazard. In the known condition of crack growth at a certain distance from coal face, it is suggested to replace mechanical parameters by geophysical data through application of different evaluation approaches: actual stresses-by spectral-acoustic method relative to amplitudes of high-frequency and low-frequency components of acoustic signal generated by mining machines in coal face area; formation pressure-by analysis of methane concentration in mine air in coal face area; strength of the most folded coal bed-by measuring strength based on penetration depth of a steel cone. The author analyzes the influence of acoustic, strength and permeability and porosity properties of coal face area on limit value of geophysical pre-outburst crack propagation criterion.

Loading causes stress concentration around defects in rocks, which induces initiation and propagation of cracks. Physically, external loading shows itself in rocks as acoustic and electromagnetic emission, included infrared radiation. Experimentally, it is found that in specimens of geomaterials under uniaxial tension, temperature is minimum; under uniaxial compression, temperature grows; under triaxial stress, temperature is maximum. It has been succeeded to derive equations for temperature prediction in a material in the zone of main crack as function of failure load. The method to estimate stress state based on the data on infrared radiation in materials is developed.

Based on the experimental data on separation of stone blocks from rock mass, the author has developed an approximate analytical model to find energy input required to initiate main crack depending on mechanical properties of rocks, geometry of bench, diameter of drillholes and meterage drilled.