SU825945A1 - Device for measuring strain in solid rock - Google Patents

Description

I

The invention relates to voltage measuring instruments in a rock mass array.

Photoelastic stress sensors are known that were mounted in a vice glass zipingr with an axial bore, installed in the well and glued to its walls flj.

However, well known aators allow measuring stresses only in the plane of the normal axis of the well, and do not provide for carrying out remote measurements.

It is also known a device for measuring stresses in hard rocks, including a metal cylinder and strain gauges fastened to the inner surface of cylinder 2.

The disadvantages of this device are the low accuracy of voltage measurement and reliability of the device, the complexity of the design of the device, as well as its high cost.

2

The purpose of the invention is to improve the measurement accuracy and reliability of the device.

The goal is achieved by the fact that the cylinder is made of thick-walled high modulus material.

FIG. 1 shows the proposed device, a general view; FIG. 2 is a section A-A in FIG. one..

The device consists of a tosteostea tube 1 with two sealing nuts 2 and 3. Inside the tube 1 there are placed measuring strain gauges 4, oriented in the plane perpendicular to the longitudinal axis of the device, measuring strain gauges 5, oriented in the direction of the longitudinal axis of the device, and a shepherd 6 with a compensation. 7. A compartment with strain gauges is sealed by a board 8 of insulating material in which pins are installed 9. Wires 10 from strain gauges (attached to pins 9. On the other side of the board 8, to pins 9 are fastened

cables from cable 11, which is sealed in nut 3.

Three strain gauges 4 are installed around the circumference of the tube 1 at an angle of 45 circles to a friend, and two strain gauges 5 are placed under a 90 ° angle of circles to a friend.

In order to prevent the modulus of elasticity of the rock from penetrating the instrument, the tube 1, which serves as a sensitive element of the device, is made of material, the modulus of elasticity of which is greater than the modulus of elasticity of the rock at least 4 times, for example, steel or brass. The length of the tube is determined by calculation.

When measuring, the device is installed in a well drilled in the rock and glued to its walls. When the stress-strain state of the rock around the well changes, the tube 1 is deformed together with the walls of the well. The deformations of the inner surface of the walls of the tube 1 are recorded by strain gauges 4 and 5, while strain gauges 4 respond to tube deformations in a plane perpendicular to the device and well axis, and strain gauges 5 respond to deformation of the tube in the direction of the tool and the well axis. Using the readings of three strain gauges 4, the value and

the direction of two main stresses in a plane perpendicular to the axis of the well. Based on the readings of strain gauges 5, the stress is determined in a plane parallel to the axis of the well.

To take readings from strain gauges, both in the process of calibrating the instrument and in measurements, a measuring instrument is used, for example, an IID-3 type, made according to a bridge circuit. The strain gauges 4 and 5 together with the compensation strain gauge 7 are alternately connected to the measuring arm of the IID-3 device. The measurements are performed in the following sequence. After installation of the device in the well and complete curing of the adhesive, initial readings are taken on all measuring strain gauges. Then, after a change in the stress state of the rock, repeated readings are performed. By the difference of repeated and initial readings, the magnitude of stresses in the rock is judged.

The proposed device allows to obtain a larger amount of information when measuring stresses in strong rocks, taken from a single instrument.

In addition, due to the use of a thick-walled cylinder, the design of the device is simplified (the use of liquid, a pump is excluded), which leads to a decrease in the cost of the proposed device as compared to the known by 20-50 p. The advantages of the proposed device are especially advantageous when it is installed for a long time (half a year, a year or more), since it is almost impossible to exclude liquid leaks in a known device, and upon prolonged installation they become noticeable.

The use of the proposed device for measuring stresses in hard rocks makes it possible to more correctly determine the actual loads on the support, as well as more reasonably make calculations on the strength of pillars and other elements of development systems.

Claims (2)

1. USSR author's certificate No. 342049, cl. E 21 C 39/00, 1970. 2. USSR author's certificate for application number 2083443 / 22-03, cl. E 21 C 39/00, 1974.