RU2008699C1 - Rock massif linear deformation recording method - Google Patents

Abstract

FIELD: mining technology. SUBSTANCE: quartz glass bar which length is 1-4 m is placed in bore hole and it is fixed tightly by one end. Restoring suspension bracket is made like plug in bore hole mouth with separation with respect to other quartz glass bar end. Separation can be filled by oil grease. Deformation is measuring by electric capacitance metering device installed out of bore hole. Distance between bore hole orifice and plug is choosing taking into account natural rock arch forming in roadway entry. EFFECT: better operating in productive mine conditions with background vibrating presence. 2 cl, 1 dwg

Description

 The invention relates to mining geophysics with a predominant use for recording geophysical processes in the conditions of existing mining enterprises in the presence of a background of technogenic interference.

There is a method of detecting deformations of a rock mass using a rod strain gauge containing a quartz glass rod, one end of which is rigidly fixed, and the free end, equipped with a metal tip with a polished surface, is in contact with a dial-type indicator, on the axis of which a flat mirror is mounted. In the deformograph, due to the use of the optical lever, the strain sensitivity is reached up to 1˙10 ^-7 -5˙10 ^-8 , which is an order of magnitude higher than the sensitivity of dial gauges, which are the most accurate of the widespread instruments for detecting linear deformations.

The disadvantage of this method is the relatively low sensitivity, not exceeding almost 1˙10 ^-7 , which is not enough for recording microdeformations of rocks in rock masses.

 Another disadvantage is the photographic recording of processes, which necessitates the creation of special darkened rooms or isolated mine workings with a special mode in which the deformographs are installed.

 The disadvantages also include the inoperability of obtaining information in connection with the development of photo paper, etc.

 Other methods are known for measuring the distances between two points in mine workings (indicator posts, measuring tape, converters, etc.), which are less sensitive to deformations.

The closest technical solution, selected as a prototype, is a method for recording deformations using a rod strain gauge used in geophysical surveys. Deformograph has a sensitivity of 10 ^-9 -10 ^-10 and high long-term stability of instrumental parameters.

 The main element of the deformograph is a quartz glass rod (a pipe with a diameter of 10 to 100 mm, length up to 100 m, and a wall thickness of several millimeters), one end of which is fixed to the rock using a concrete pedestal, and the other end is free and moves relative to the rock (or pedestal ) when it is stretched or compressed. The bar of the device is supported in horizontal position by wire suspensions, located after 1-2 m along its length. Instead of pipes, quartz rods with a diameter of 8-20 mm can be used. A small displacement sensor, mounted on the free end of a pipe or rod, connected with a communication line recorder, serves as a recording system.

 To carry out measurements using deformographs, which are usually installed in groups of 2-3 pieces, it is necessary to drill expensive special mine workings isolated from the external atmosphere (usually 2-3 adits), each 20-100 mm long and more, buried no less than 20 m from the surface.

 The use of long rod strain gauges to record array deformations does not ensure stable operation of the equipment in conditions of increased shock and vibration interference at existing mines when installed at distances less than 100-500 m from places of intensive mining associated with drilling and blasting, transport and other technological processes. At the same time, when installing deformographs at distances of more than 0.5-1.0 km from the mineral extraction zones, the most interesting information on the most active deformation processes in the massif practically disappears from the observational data. The dynamic effects of technological processes adversely affect the system of wire suspensions of rod deformographs, which ultimately complicates not only the interpretation of the obtained data, but also the operation of devices, and even casts doubt on the possibility of using this method in mines.

 The aim of the invention is to increase the accuracy of registration of linear deformations of the rock mass. The method consists in placing a quartz glass rod with a capacitive transducer at its free end in the mine, characterized in that the rod is placed in the borehole, has a shortened length of 1-4 m, its second end is rigidly fixed to the bottom of the well, and the elastic suspension carried out at only one point.

 The goal is achieved by the fact that in the highly sensitive geophysical deformograph with a capacitive sensor taken as the basis, the structure is changed and the dimensions are reduced: the length standard is reduced to 1-4 m, it is placed in a borehole drilled from an existing production, the standard is fixed at the bottom of the well, and elastic suspension is placed at the wellhead.

 In this case, the location of the borehole is selected in the wall or in the bottom of an existing mine so that the area of disturbed rocks near the contour is minimal or completely absent. The length of the well should be equal to 1-4 m and significantly (not less than 5 times) exceed the depth of the zone of disturbed rocks from the output circuit.

 The length standard is fixed only at two points - the bottom and the wellhead.

 The use of a well to accommodate a length standard requires significantly lower production costs than sinking. In addition, in a small volume of a borehole, it is easier to create thermostating conditions than in a mine. The advantage of the proposed method of placement and fixing the standard length is also the possibility of its placement in the vertical direction (vertical well).

 The wellhead is closed by an annular plug, which is installed near the mouth, outside the zone of disturbed rocks. A length standard with one end is rigidly fixed to the bottom of the well, and the free end is equipped with a capacitive displacement sensor. The annular plug can be made in the form of an elastic suspension.

 The drawing shows a diagram of a mine strainmeter installed at the Karnasurt mine of the Lovozersky GOK.

 From mine 1, a well 2 was drilled 3.2 m long and 76 mm in diameter, in which a length standard in the form of a quartz glass rod 3 is placed (a quartz glass pipe has a diameter of 40 mm and a wall thickness of 3 mm). One end of the length standard is cemented to the bottom of the well 4, and the other end is fixed at the wellhead using an elastic suspension 5 made of wire, which ensures the movement of the standard only along the axis of the well.

 One plate of the capacitive displacement sensor 6, two other plates of which are mounted on a concrete pedestal 7, is rigidly attached (welded through a quartz rod) to the free end of the length standard, protruding 0.3 m from the wellhead.

 For thermal insulation of the length standard, an annular plug 8 of heat-insulating material (for example, foam) with an inner diameter of 41 mm corresponding to the outer diameter of the length standard is installed at the wellhead. The thermal insulation plug is installed outside the zone of disturbed rocks 9 with a certain minimum clearance with a length standard so as not to impede its longitudinal movement.

 The length standard is equipped with a remote calibration device 10, creating the application of a known tensile force along the axis using calibration weights, or an electrical signal.

 The method of recording deformations is implemented as follows. When the array is stretched or compressed, the quartz rod fastened with the array in the bottom of the well, together with the sensor plate welded to its end, moves relative to the other two sensor plates mounted on the pedestal. A change in the distance between the moving and fixed plates causes a change in the electric capacitance of the converter and is recorded in the form of an electric signal by a recorder 11, to which the sensor is connected by communication lines. During measurements, changes in the base are recorded from the point of attachment of the length standard in the bottom of the well to the gap in the capacitive sensor caused by deformations of the rock mass.

The proposed method is most suitable for rocky mountain massifs with insignificant fragmentation, in which the elastic deformations caused by natural and man-made impacts are very small and are calculated in fractions of a millimeter. The maximum strain gauge sensitivity, which is necessary in mine measurements, is the level of force effects caused by natural lunar-solar tides. For the latitude of the Kola Peninsula, the relative values of tidal deformations are 1˙10 ^-7 -1˙10 ^-8 . The sensitivity of a mine borehole strain gauge with a base of 1-4 m is 1˙10 ^-8 -1˙10 ^-9 , which allows you to confidently register deformations caused by lunar-solar tides; besides, it is 1-2 orders of magnitude higher than the sensitivity of the above-described devices such as a converometer.

 In the conditions of rock massifs with insignificant fragmentation of rocks by cracks, the measurement of mass deformations using long-basal geophysical deformographs with a length of 10-100 m does not give advantages compared to the proposed method even in the absence of anthropogenic interference caused by lunisolar tides and anthropogenic factors.

 Tests of the proposed method using a deformograph with a base of 3.2 m during 1988-90 at the Karnasurt mine of the Lovozero GOK showed that it reliably records the same signals that are recorded by a deformograph with a base of 20 m located in close proximity (50 m) from the tested downhole strain gauge, not inferior to it in either sensitivity or stability of parameters. (56) 1. USSR author's certificate N 575595, cl. G 01 V 1/18, 1977.

 2. Starkov V.I., Lovchikov A.V., Kolomiyets A.S. Test procedure for quartz indicator strain gauges in mines, IGD SB RAS, Novosibirsk, 1980, p. 83-88.

 3. Technique for controlling stress and strain in rocks. L.: Nedra, LO, 1978, p. 229.

 4. Osika V.I., Osinskaya S.V., Chuvikov G. B. Quartz deformometer KD-Sh. In the book. : "Instruments and methods for processing gravitational measurements." Moscow, Institute of Physics of the Academy of Sciences of the USSR, 1984.

Claims (2)

 1. METHOD FOR REGISTRATION OF LINEAR DEFORMATIONS OF A MASSAGE OF ROCK ROCKS, including placing a quartz glass rod in the mine working on an elastic suspension with a capacitive transducer at its free end, as well as a calibration device, and determining linear deformations of the array by changing the electric capacitance of the converter, characterized in that a rod 1 to 4 m long is placed in the borehole, its second end is rigidly fixed to the bottom of the well, and the elastic suspension is made in the form of an annular tube installed with a gap to the rod, and p located at a distance from the wellhead, selected on the basis of the conditions for reducing temperature and vibration interference associated with the zone of natural arch formation.  2. The method according to p. 1, characterized in that the annular plug is installed in the well outside the zone of natural arch formation, and the gap is filled with grease.

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