Landslides occur extensively in all countries of the world. A landslide is a complex geologic body composed of a combination of layers having contrasting and gradational physical properties. In assessing the danger of landslides, it is of prime importance to investigate the structure of the landslide slope and its water saturation as well as the properties and status of the soils comprising the slope. The investigation and full evaluation of all these problems by traditional methods of engineering geology are sometimes impossible. Electrical and seismic methods are used to obtain the information needed to determine slope stability. Experience has been gained from longterm investigations carried out in various regions of the Soviet Union. Applications include evaluating geologic and hydrologic conditions related to the occurrence of landslides. Primary attention is devoted to the study of landslide slopes proper. The geologic structure of a landslide is considered in modeling it and determining the thickness of both the landslide body and the slip zone. The methods of self‐potential, resistivity, and temperature measurement are analyzed for characterization of the seepage flow through the landslide body. Self‐potential, resistivity, and temperature anomalies are associated with sites of increased landslide activity. Useful engineering properties of soils may be obtained from field and laboratory geophysical measurements. Measurement of changes of geophysical parameters with time are significant in assessing changes in the states of landslide soils. Observation of the direction and velocity of landslide movements is possible with magnetic and electrical methods. Examples of geophysical investigations of landslides in the Crimea, on the Black Sea coast of the Caucasus, and in the Volga River Valley are presented.
Considerable water leakages from reservoirs make it difficult to attain the planned storage capacity. In some cases water leakages give rise to suffusion followed by catastrophes. Until recently methods for locating water leakages were extremely imperfect. Geophysical methods offer good prospects in this direction. For solving these problems, it is effective to use streaming potential measurements, water flow rate observations and thermometry. Laboratory experiments were carried out in connection with the fact that water leakages from reservoirs are characterized by negative anomalies of natural currents; the more filtration discharge, the higher these anomalies are. As a result, the relationship governing the intensity of streaming potential and sand granulometric composition, electrolyte concentrations and other factors were revealed. To determine the velocity of water flowing to leakage sites, a special device, based on the relationship between the temperature of a heated body and its resistance, is applied. This device simultaneously makes it possible to measure the water medium temperature. Observations at reservoir sites were effected by moving along the reservoir non‐polarizable potential electrodes and water velocity devices. Recordings were carried out automatically by the recording device of the logging apparatus. Under the conditions of ice cover on water surfaces, measurements were made through separate points by digging holes in the ice cover. Practical field observations were carried out at reservoir sites located in regions where fissured massive rocks as well as loose sediments predominate. In the first case field experiments were carried out in alpine reservoirs, in Armenia. The major water leakages were found to be concentrated on the right bank of the reservoir. In this connection it was not only possible to locate water leakage sites, but also to evaluate their relative intensity. These data were used for planning antifiltration measures. In the second case water leakages from a reservoir located in Uzbekistan in the submontane part of the Pamirs were studied. Streaming potential anomalies and high benthonic flow rates made it possible to discover high filtrations in the base and walls of the dam. Further perfection of these methods should not only permit the determination of water leakage sites and their relative intensity, but also filtration discharges in absolute units.
BOGOSLOVSKY, V. V. and A. A. OGILYY, 1973. Deformations of Natural Electric Fields Near Drainage Structures, Geophysical Prospecting 2 I, 7 16-723, The paper deals with the electro-filtrational fields formed near the drainage structures. Main laws of deformation of these fields above vertical and horizontal drains are considered and practical examples supplied. Deformation of seepage flow by drainage structures increases the groundwater flow velocities and, consequently, intensifies the electric fields of filtrational origin. The values of anomalies (amounting to tens and some hundreds of millivolts) mainly depend on the pressure drop, lithological and granulometric composition of the rocks, and on the salinity and chemical composition of the ground water. Laboratory investigations show that at a given pressure drop maximum electro-filtrational fields are observed for particles ranging from 150 to 250 lo (Ogilvy, Ayed, and Bogoslovsky 1969). Water flow in open fissures is characterized by smaller values of streaming potentials decreasing with the opening of fissures. The presence of a sand filler in the fissures up to 40% brings about an increase in the SP values. Further increase in the amount of filler results in somewhat reduced SP values.The magnitude of the electric fields under observation is sharply reduced by the presence of clay fractions both in sandy grounds and fissure filling material On the one hand, the clay causes a decrease of the permeability of the medium, and on the other the appearance of potentials of adsorptional origin.Since the streaming potentials are directly proportional to the potential difference between the immobile part of the electric double layer and the free solution (E potential), they decrease with an increase of the electrolyte concentration.Therefore, maximum electro-filtrational fields are induced by the *
The method of induced potentials is applied in groundwater and certain types of engineering‐geologic investigations. Because of the complex nature of induced polarization in ion‐conducting media, the subject still has not been sufficiently studied. This phenomenon is evidently associated with the diffusion processes occurring between narrow and wide capillaries and affected by membrane potentials in the presence of clay fractions. The laboratory experiments have proved the dependence of induced potentials of sandy‐clayey media on their particle‐size distribution pattern, porosity, moisture content, interporous moisture, salinity degree, and temperature. Modeling accomplished with horizontally layered sections and lenses of fresh and saline waters has given data for analyzing polarizability behavior in heterogeneous media. Field investigations have been carried out in Central Kazakhstan, the Crimea, Mordovia, Armenia, and the Moscow area. The data obtained testify to the applicability of this method for determining the depth to groundwaters in sandy‐clayey deposits, detecting accumulations of fresh groundwaters, and specifying the position of the interfaces between fresh and saline waters. No less important is the possible utilization of a parameter for identifying rock types and characterizing the sandy‐clayey deposits. Using field examples, the authors consider the expediency of applying the IP method for investigating massive rocks and for prospecting for water in fractured and karst rocks. The IP method significantly supplements the information obtained by conventional methods and is employed in combination with them in borehole logging. In perspective, polarizability can be used as a parameter for establishing the correlative relations between geophysical, hydrological, and strength parameters of rocks.
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