SU1425327A1 - Method of determining strain in rock mass - Google Patents

Abstract

The invention relates to mining. The purpose of the invention is to increase the accuracy of stress determination. The rock sample extracted from the massif is subjected to stepwise aging compression with an exposure at each step of the load until the linear-creep deformations develop in the sample. From the deformations measured in time, the magnitude of the steady-state creep rate is determined. Build a graph of the steady-state creep rate versus stress in a sample,. The magnitude of the stress acting in the array is taken as the stress corresponding to the initial moment of the decrease in the rate of steady-state creep. 2 Il.

Description

one

to

Oi

with y

H

:. 1H

The invention relates to mining, in particular, to methods for determining stresses in a rock mass at the operational and geological exploration stages.

The purpose of the invention is to improve accuracy.

 Fig. 1 shows a diagram of a device for determining the stresses in a rock mass in Fig „2 - a graph of the dependence of the steady-state strength on voltage, applied by jsaeMoro to a rock sample. ; The device contains a press 1 for | loading a rock sample 2, a dynamometer 3 for measuring the load on sample 2, and a block 4 of deformometers | dp for measuring the strain of sample 2.

j The method is carried out as follows.

i With the help of press 1, sample 3 of rock extracted from the massif, 1 is subjected to stepwise increasing compression with holding at each step of the load until development of linear creep in the sample 2 | The load level is measured with a dynamometer | 3. The unit 4 deformers serves to measure the deformed and sample 2 in the step-loading process. According to the results of strain measurements for: each step of loading, the graphs of the dependence of relative strains on time are plotted and the magnitude of the rate of steady-state fouling is determined. The graph of the dependence of the steady-state creep rate () on stress (G) is plotted in coordinates. On the graph, the inflection point of the curve 1p, - {5, is found and the voltage corresponding to this point is taken as acting in the array.

0

five

The creep increases at a constant rate of deformation of the sample during 3-5 min intervals 30–40 min after the start of loading at each step. After that, the load is increased and the creep tests are carried out at a higher stress level. When the initial level of stresses is exceeded, a sharp decrease in the rate of steady-state creep is observed compared to its value at the previous load step.

Experiments also show that the memory of rocks for action. Voltages are maintained for many tens of hours after the load is removed (removed from the mass).

Figure 2 shows a characteristic change in the linear creep deformation rate 6 with increasing stress G. The curve of values observed shows a sharp change in the region (5–20 MPa, corresponding to the level of the preceding stress (stress in the array).

For the absolute majority of laboratory experiments (tens of experiments), the accuracy of determining the preload (modeling-stresses in the array) is 1-10%.

Claims (1)

Invention Formula The method of determining stresses in the rock massif, which consists in increasing stepwise loading of the rock sample extracted from the massif, measures creep deformations that correspond to each load level and An example, Samples of different ma- Materials and rocks (polymethyl methacrylate, limestone, marble) are kept under load P for several hours (ten hours), and then unloaded, withstanding unloaded from ten hours to several days. Next, the samples are subjected to stepwise loading. At each stage, the specimen is kept under load until the development of linear creep deformations. Measurement of sample strain is performed with an accuracy of lz 50 55 ten mm, at the same time, in order to improve the accuracy, at each step of loading, the sample is kept under load until the development of linear creep deformations in it, the creep deformations are measured in time, determined the steady-state creep rate, and the gain of the steady-state creep rate is used as the deformation parameter. 0 five the stress corresponding to the initial moment of decreasing the sample deformation parameter, characterized in that, in order to improve the accuracy, at each load stage the sample is kept under load until it develops linear creep deformations, creep deformations are measured in time, the established creep rate is determined, and the gain of the steady-state creep rate is used as the deformation parameter. B, 1 / fiUM yuu 1.0 -Y r6 ; In ///// 777 FIG. one