CN102162357B - An in-situ test method for the existing stress on shaft wall - Google Patents

Abstract

An in-situ test method for the existing stress of the shaft wall. Double holes are opened on the inner surface of the shaft wall to test the strain change in the middle part of the double holes, and the existing stress of the shaft wall is calculated according to the strain change before and after the hole is opened. Determine the position of the hole on the surface of the well wall to be measured and mark it; paste the horizontal and vertical strain gauges in the middle of the double hole position, connect the data lines, and test their initial strain values; make a hole at the mark and test The strain increment of the strain gauge; the existing stress of the borehole wall is calculated according to the strain change before and after drilling. That is to drill two holes on the surface of the inner wall of the well wall, test the strain change in the middle of the two holes, and calculate the stress according to the change in the strain of the well wall concrete before and after drilling. The method is simple to operate, does not damage the integrity of the shaft wall, and has high testing accuracy, which lays a foundation for the safety diagnosis of the shaft wall.

Description

An in-situ test method for the existing stress on shaft wall

Technical field:

The invention relates to an in-situ test method for the existing stress of the well wall of a shaft, which is particularly suitable for testing the current stress of the well wall with thick topsoil, and is also suitable for testing other similar concrete well walls (structures).

Background technique:

Most of the vertical shafts in the thick topsoil have been in operation for many years, and the stress state and stress magnitude of the shaft wall are not clear, which brings difficulties to the prediction of shaft fracture disasters and the implementation of shaft fracture prevention and control projects. Obtaining the existing stress of the well wall and judging its safety is necessary, especially for well walls that have been built for a long time. At present, the in-situ testing methods for testing the existing stress of wellbore walls mainly include stress relief method and hydraulic fracturing method, etc., but these testing methods are complicated to operate, take a long time in the wellbore, and are relatively destructive to the wellbore wall. Therefore, it is necessary to invent an ideal in-situ test method for the existing stress of the borehole wall, which will become an important means for judging the safety of the borehole wall.

Invention content:

The purpose of the present invention is to overcome the problems existing in the prior art, and provide an in-situ testing method for the existing stress of the shaft wall with simple and convenient operation, little damage to the shaft wall and high measurement accuracy.

The in-situ testing method of the existing stress of shaft wall of the present invention comprises the following steps:

a. Calibrate the positions of the two boreholes to be tested at intervals of 10-20m on the same axis within the vertical depth of the wellbore within the range of 50-200m;

b. Clean the surface of the two boreholes to be measured at the wellbore interval calibration;

c. Afterwards, paste two horizontal and vertical strain gauges arranged at right angles on the well wall between the two borehole positions to be tested at the interval calibration, and connect the test data wires connecting the two horizontal and vertical strain gauges to the strain tester. connected to the instrument;

； d. Turn on the strain testing instrument, start data acquisition, and record the initial strain value

;

e. Drill holes one by one at the positions of the two holes to be measured at the interval calibration, stop for 5 minutes after drilling the first hole, and then drill the second hole;

； f. After drilling, continue to collect strain data until the data is stable, and record the final stable strain value

;

； g. Obtain the strain change value according to the two strain values before and after the drilling of the two holes to be tested

;

与既有应力

的函数关系式：

计算得出待测井壁的既有应力值。 h. Change value according to strain

with existing stress

The functional relation of :

Calculate the existing stress value of the borehole wall to be measured.

The center-to-center distance of the boreholes to be tested is 8-16 cm, and the diameter of the boreholes is 4-8 cm; the borehole depth of the boreholes to be tested is controlled at 4-6 cm.

Beneficial effects: by drilling double holes on the surface of the borehole wall, the strain change in the middle part of the borehole is tested, and the stress of the borehole wall is calculated according to the strain change before and after the borehole is opened. It is easy to operate, occupies a short time in the shaft, and basically does not affect the lifting of the mine; the space required for the operation is small, especially suitable for the small operating space of deep underground structures such as the shaft; it will not damage the integrity of the shaft wall. Its main advantages are:

1. Obtaining the existing stress of the shaft wall is an important factor for the safety evaluation of the shaft wall structure;

2. The proposed method to obtain the existing stress of the shaft wall is simple to operate, occupies a short time in the shaft, and basically does not affect the mine hoisting;

3. The method requires less space for operation, and is especially suitable for the characteristics of small operation space in deep underground structures such as shafts;

4. Without destroying the integrity of the well wall.

Description of drawings:

Figure 1 is a schematic diagram of the testing method of the present invention.

In the figure: drilling hole-1, data testing line-2, strain sensor-3, well wall-4.

Detailed ways:

As shown in Fig. 1, the in-situ test method of the existing stress of shaft wall of the present invention, by opening double holes, test the change amount of strain in the middle part of the double holes before and after opening, according to the difference between the change amount and the existing stress of the shaft wall According to the functional relational expression, the existing stress value of the borehole wall is calculated, and the specific steps are as follows:

a. Firstly, within the range of 50-200m vertical depth of the wellbore, calibrate the positions of the two boreholes 2 to be measured at intervals of 10-20m on the same axis;

b. Clean the surface of the two boreholes 2 to be measured at intervals on the borehole wall 1;

c. Afterwards, two horizontal and vertical strain gauges 3 arranged at right angles are pasted on the well wall 1 between the two positions of the boreholes 2 to be measured at interval calibration, and the test data of the two horizontal and vertical strain gauges 3 will be connected. The wire 4 is connected to the strain testing instrument;

d. Turn on the strain testing instrument, start data acquisition, and record the initial strain value ;

e. Drill holes one by one at the positions of the two holes 2 to be tested at the interval calibration. After drilling the first hole, stop for 5 minutes before drilling the second hole. The distance between the centers of the holes 2 to be tested is 8~16cm. The diameter is 4~8cm, and the drilling depth of the hole 2 to be tested is controlled at 4~6cm;

f. After drilling, continue to collect strain data until the data is stable, and record the final stable strain value ;

； g. Obtain the strain variation according to the two strain values before and after the opening of the two boreholes 2 to be measured

;

为测试得到的应变变化值。 h. Change value according to strain with existing stress The functional relation of : That is to say, the existing stress value of the borehole wall 1 to be measured can be calculated, where: is the existing stress value of borehole wall 4;

is the strain change value obtained from the test.

Claims (1)

1. the home position testing method of the existing stress of shaft wall, is characterized in that comprising the steps:

A. demarcate the position of two borings to be measured (2) every 10 ~ 20m recurrence interval on the same axis that is positioned at pit shaft vertical depth 50 ~ 200m scope;

B. surface clean is carried out in two borings to be measured (2) position of the borehole wall (1) interval being demarcated;

C. after, the borehole wall (1) between two borings to be measured (2) position of demarcating at the interval is upper paste at right angles arrange one laterally, a vertical foil gauge (3), will connect horizontal, vertical two test data wires (4) to foil gauge (3) and be connected with the strain testing instrument;

D. open the strain testing instrument, the beginning data acquisition, and record the strain initial value

The position of two borings to be measured (2) of e. demarcating at the interval is implemented boring one by one, bored first hole after pause 5min bore again second hole;

F. hole complete after, continue to gather strain data until data stabilization records final strain stable value

G. obtain the strain variation value according to two strain values before and after two borings to be measured (2) perforate

H. according to the strain variation value With existing stress Between functional relation: Calculate the existing stress value of the borehole wall to be measured (1).

2. the home position testing method of the existing stress of shaft wall according to claim 1 is characterized in that: the center to center distance distance of described boring to be measured (2) is 8 ~ 16cm, and bore diameter is 4 ~ 8cm.

3. the home position testing method of the existing stress of shaft wall according to claim 1 and 2, it is characterized in that: the drilling depth of described boring to be measured (2) is controlled at 4 ~ 6cm.

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