The area of possible use of blast energy for moving earth masses is expanding with the development of canal construction. This is being promoted also by the development and investigation of the progressive blasting method using linear crater charges, which consist of a continuous mass of explosives placed in charge trenches.In comparison with the previously used rows of chamber charges the linear form offers the following important advantages: a) the possibility of complete mechanization of work with a considerable decrease in labor intensity; the charge trenches are dug by excavators, the explosives are fed into the trench by a truck-mounted crane or along chutes, tamping is done by a bulldozer covering the explosives with the soil excavated earlier; b) acceleration of work, their concentration in space and time during operation of mechanized columns (excavator, equipment for charging explosives, bulldozer) successively performing all technological operations in a confined and rapidly advancing section of the route; c) possibility of obtaining an even bottom in the cuts (without projections between charges), and also uniformity of compression of the bases of the cuts upon blasting, which lessens the seepage of water during operation of the canal.In comparison with the use of excavating equipment, the use of linear charges provides a high rate of earth-moving with considerably smaller capital investments and labor expenses.Under favorable conditions the cost of moving earth by explosives approaches the cost of removal by excavators.Linear crater charges were used in the construction of the Irtysh-Karaganda, Volga-Ural, Nura-Sarysu, and other canals.They are promising for the planned diversion of part of the runoff of Siberian rivers to Central Asia and Kazakhstan.The Institute of Specialized Operations of the All-I~ion Planning, Surveying, and Scientific-Research Institute (Gidrospetsproekt) has carried out a program of experimental investigations of the characteristics of the action of linear charges in soft soils. It included modeling, blasting at testing-grounds on a scale approximating to that necessary for the construction of canals, and an analysis of the data from industrial explosions. The testing-ground explosions were carried out by the Kazakh branch of the State All-Union Trust for the Stabilization of Foundations and Structures (Gidrospetsstroi) in different varieties of foams and loamy sands with a density from 1.5 to 2 g/cm 3 and water content from 4 to 18%.The main results of these tests are given below, which permit a substantiated design of the detonation of linear charges.The mass of 1 m of linear crater charge can be calculated by the equationwhere Ql is the weight of 1 m of linear charge, kg; K is the calculated specific consumption of explosives, kg/m3; this coefficient depends on the s0il in which blasting is carried out; it is taken from the recommendations in technical guides (e.g., [i]) and refined by test shots; e is the conversion coefficient of the consumption of explosives relative to...

Linear ejection charges in trenches or tunnels in the form of a continuous extended mass of explosives are used in the construction of canals, in opening up mineral deposits, and for other purposes. In many cases the planned dimensions of the excavation require two or three charges. An effective method of controlling the action of a system of charges is short-delay blasting. However, this has not been thoroughly studied in connection with linear charges.From the theory of similarity it is clear that the principal parameters governing the development of the explosion of a linear ejection charge are the scale of the blast, which is usually assessed b~he length W of the line of least resistance (LLR), and the so-called reduced depth of the charge, W'= W/VQ/, where Ql is the mass per meter of charge. The quantity W, like the often-used index of action of the blast n, indicates the degree of loading of the charge.Rodionov and Adushkin [1] have demonstrated that for charges with ordinary LLR (up to 20-25-m) we can neglect the effect of gravity. In such cases, other conditions being constant, the time of development of the blast should be proportional to W, and its dependence on ~ is determined experimentally.We have studied how the times of development of explosions of linear charges depend on the blasting parameters in loams with a density of 1.5 g/cm 3 and a moisture content of 8-10%; we used high-speed cinematography. The camera was an SKS-1M operating at 400-800 frames per second. The frame frequency was calibrated using time marks printed on the film every 10 msee.Charges of ammonite No. 6-ZhV weighing 6.5-26 kg per meter were laid in trenches with LLR of 1.0 or 1.4 m. The depth of the charges was varied between 0~20 and 0.45 m -kg-~ the blast action index ranged between 1.5 and 4.8.From the motion-picture film data we plotted profiles of the development of the ejected burst and the time dependence of the upward velocity of the soil. Figures 1 and 2 show sample profiles and graphs. We can distinguish several stages in the motion of the burst. In the first stage, which lasts up to 10 msec, the soil was accelerated to velocities of hundreds of meters per second -much higher than those from blasts of concentrated charges with action indices of up to 1.5 [1].In the second stage of the motion of the burst the velocity gradually decreased, though remaining high (up to 100 m/sec), while the cross section of the burst was rounded in shape, with no marked projections. At this stage the height of the burst reached 10 m for a development time of the order of 100 msec.In the third stage the soil velocity continued to fall, and the motions of different parts of the burst became nonuniform -separate rock jets could be distinguished, and are clearly visible on the profiles. Between the jets the soil moved more slowly, and spaces appeared, i.e., the dome broke up at the transition between the second and third stages. Finally, in the fourth and last stage of development of the burst, the gas currents overtook the soil, while the u...

It is known that drilling and blasting operations near the lower contour of the foundation pits of important hydraulic structures should be performed so that the necessary preservation of the rock foundations is provided.In connection with this, the standards [i, 2] specify measures to limit the intensity of action of blasts on a rock foundation. They include leaving a protective layer between the working bench and design contour of the foundation, which is then loosened by firing shothole (diameter < 42 mm) charges, limitation of the diameter of blasthole (diameter > 42 mm) charges on the working bench above the protective layer to ii0 mm, preclusion of overbreaking of blastholes in the protective layer~ and certain others. The requirement about loosening the protective layer by shothole charges leads to a substantial increase of labor intensity and time of excavating the pit, and also to a large amount of manual labor under harmful conditions~ Special investigations by the State All-Union Trust for Stabilization of Foundations and Structures (Gidrospetsstroi) and the experience of constructing a number of hydrostations showed that a more progressive technology of drilling and blasting operations (DBOs) near the foundation of important hydraulic structures is possible, which provides both a decrease of labor intensity and time of works and sufficient preservation of foundations.In this case the layer of rock directly above the foundation contour is loosened not by shothole but by reduced blasthole charges~ The State Special Design Institute (Gidrospetsproekt) has developed a method of determining the parameters of such blasting [3, 4] and jointly with the All-Union Planning, Surveying, and Scientific-Research Institute (Gidroproekt) is preparing a new edition of the subsection "Drilling and Blasting Operations" of construction specifications and regulations SNiP III-45-76, not containing the requirement of mandatory shothole loosening of protective layers.By now there is favorable experience in preparing rock foundations of the Sayano-Shushenskoe, Dnestr, and Kurpsai hydrostations without shothole loosening of the protective layers [5,6].The purpose of the experimental drilling and blasting operations in preparing the rock foundation of the Krapivinskii hydrostation was to test under specific conditions the parameters of blasting near the lower contour of the pit with reduced blasthole charges calculated by method [4]. On the basis of the data on preservation of the foundation at the sites of the blasts, obtained recommendations are given on the further conduction of DBOs near the lower contour of the pit.The main structures of the Krapivinskii hydrostation under construction are located on the floodplain and slope of the left bank of the Tom River. The rock foundation of the concrete dam and powerhouse is composed of diabase-porphyries withthe following physical and mechanical properties (in a sample): density 2.7 x 103 kg/m3, compressive strength in a dry state 110-120 MPa, propagation velocity of longitudina...

The question concerning the relationship between the lumpiness of a blasted mass and the diameter of bore charges is one of the basic questions raised during the development of a method for computing lumpiness.There is no single opinion concerning the character of the effect of the charge diameter on lumpiness in the technical literature.Some specialists consider that the lumpiness of a blasted rock mass remains constant when the same specific explosive consumption and geometric similitude between the diameter of the charges and the dimensions of the grid in which they are arranged is observed in a specific rock mass.This position is reflected, for example, in "Technical rules for conducting blasting operations in power construction" [I], where the lumpiness computation is based on studies by V. K. Rubtsov.In other publications, which are comparatively small in number, it is stated that an increase in the diameter of the charges is accompanied by an improvement in the size reduction of the blasted mass due to an increase in the reaction time of the stress waves with increasing scale of the blast.Finally, it is indicated in the majority of studies conducted in recent years that an increase in the diameter of the charge will lead to degradation and size reduction; in this case, it is usually associated with an increase in the number of natural cracks between charges as their diameter increases, and, consequently, the distance between them, i.e., with the factor of the independence between the natural fissured state of the rock masses and the scale of blasting.Thus, Kutuzov and Rubtsov [2] and Kutuzov [3] describe the relation between the required specific consumption of explosives and the diameter of the charge by the equation q ~(0,6 + 3.3d.x),where d is the diameter of the bore charge in m, and x is the average dimension of the cleavage in the mass in m.The possibility of reducing the scale effect of the variation in the coarseness of material size reduction to the effect of the natural jointing of the rock mass alone raises doubts, since then it should not be observed in a solid or slightly cracked medium; this contradicts most practical observations. The purpose of the present study was to evaluate experimentally the effect of variation in charge diameter on the lumpiness of a blasted mass under conditions of geometric similitude between the dimensions (diameter and length) of the charges and concrete blocks (solid and cracked) in which the blasting was carried out.The blocks were cylinders of a ceanent--sand mix with a through axial channel for placement of the charge.The compressive strength of 4 x 4 x 4 cm control cubes formed from this material was 42 MPa.Some of the blocks were prepared as solid blocks, and others as sectional blocks formed from concentrically placed tubular elements between which inserts of a thin perforated paper were placed to simulate cracking.The number of elements in the composite blocks numbered two or three, depending on the block diameter.The distance between "cracks" was 5-6 cm.S...

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