Coal is the basis of Ukraine's energy independence. Also, Ukraine has ferrous metals, construction and building materials groundwater resources. Because the extraction of mineral resources is not standing still, the depth of mining increases steadily. .The deeper we descend, the more is exposed to stress and all sorts of dangerous events (rock bumps, coal and gas outbursts, reduction of the stability of the workings, etc.). These phenomena reduce safety and exposes miners to risks.
In order to avoid unpleasant situations need to learn to predict the stress state of the array. The most reliable is to measure the stress components directly in situ in the mine.
There are many methods for measuring stress (kinematic[ 7 ], the method of break-out fracture[ 6 ], perturbation method [ 1 ], parallel wells, the method of pressure difference, etc.). Their abundance denionstrates that there is no ideal technique to measure the stress in the rock mass. The overcoring method is a stendad one in geomebhanics to measure the stress[ 4 ]. The main drawback of this method is the small base dimensions. In this paper we want to increase the base dimensions thereby increasing their accuracy, without additional significant cost.
IntroductionOn a very large area of the globe upper crust have increased horizontal stresses which are caused by past and modern advances of tectonic plates. [ 3 ]
Figure 1 [ 2 ] shows an example map of the distribution of horizontal stresses within Europe.
Figure 1 - example map of the distribution of horizontal stresses within Europe.[ 2 ]
It is seen that in general there is a trend of compressive stresses from the southeast to northwest. As a result of these stresses in the design of underground deposits of having negative manifestations of rock pressure, which is particularly intense in those areas where the horizontal component values, voltages have abnormal values. In this study, developed the device and method for measuring the strain relief by means of which reduced the stress state of rock. The method of unloading is a standard method for determining the components of stresses in the intact-array. The disadvantage of existing methods is that measurements carried out at a depth of a well or borehole (borehole length), which must be drilled within the zone of influence of the excavation is drilled measuring trace. Distance gluing strain gauges and removal oburivaniya end face leads to the fact that there are measurement errors and these errors increase due to the fact that the base measurement vesmamalenkaya (diameter of the trace is no more than 30-50 millimeters).
Survey of researchIn this paper, improved method for measuring the discharge-voltage components.[ 5 ] The main idea of the modified method is that the measurement of strain unloading is carried out on a large database, the length of which is the order of meters or more and carried on the plane, cleaning or preparatory slaughter. At the bottom of the preparatory generation establishes two of the frame, between which is secured a special transportable device for surveying pretenzetsionnoy registration of deformations, then the executive body of the combine exercise stope a meter and a half, forming a cavity. As a result of deformation of a cavity by unloading the remainder of the rock volume in the preparatory slaughter and this site razuplotnyaetsya toward the cavity. The purpose of this technique is to record the strain relief.
Animation 1 - Chart of work of device. Animation is executed in the program of gif-animation, containing 4 shots, time-lagged 1 second.
Figure 2 - designed surveying device.
To implement this technique is designed specifically surveying device shown in Figure 3, which consists of a telescopic sliding tube sostoyaschey2 from an external (1) and internal (2) rack.These racks are interconnected with a micrometer, which has a movable probe, which gives the possibility to move along the telescoping tube. Micrometer is fixed at one end to the rack (1) and with the help of a micrometer screw it is possible to simulate the stress-strain razdvizheniya this post. The measuring stand is fixed between the frames that are reinforced in the recess. One end of the rack is attached to the frame, set in the plane of the preparation of a lava and the other end stands rigidly attached to the lever (6). Lever (6) rigidly attached to the second frame, which is installed in the plane of the preparatory lava. Due to elastic deformation lever and stand a deviation of the movable arm by a small angle, this deviation is measured with a laser pointer (7), which is fixed on a movable head (8). With this head and a micrometer screw vystanavlyaetsya position of the pointer so that the beam spot from him falling on a screen located at some distance. The distance is taken of a few (3-5) meters. Due to this distance is the geometric enhancement of the movement of the lever by which high accuracy measurement of stretching the measuring bar.
Figure 3 shows a snapshot of moving the light spot from a laser pointer in his torirovke in stand conditions.
Figure 3 - a snapshot of moving light spot.
For example, to measure the strain relief on the plane of lava, the meter is installed on the plane, lava, and to the site on which the strain gauge is suitable Shearer, which forms the screw stope at 0.8 meters. When approaching this harvester to install the meter having tensile strain in the plane of the lava is running a couple of frames. This meter is precisely captures this tension. Once the measured strain, used a special technique for the restoration of stress, which is implemented by the method of determining three-dimensional finite element formulation.
ConclusionDeveloped a device and method for measuring stress in a component-intact array of great importance to improve the reliability prediction of negative manifestations of high rock pressure and reduced risk of work in underground conditions.
Important noteNow my master's degree work is not finally written, because final verification is required in the real terms, simpler speaking is lowering in a mine and direct measuring.
References