CN204788744U - Measure high sensitivity borehole deformeter of crustal stress - Google Patents

Abstract

The utility model discloses a high-sensitivity drilling deformation gauge for measuring ground stress. Four sets of ring sensors are arranged in the shell of the deformation gauge, and each set of ring sensors consists of two thick arc steel sheets and two thin arc steel sheets. The steel sheets are connected end-to-end; each thin arc-shaped steel sheet is respectively pasted with a sensing resistor on the inner and outer sides of the arc center; each thick arc-shaped steel sheet is provided with an induction contact on the top center of the outer arc head. The eight sensing contacts on the four sets of ring sensors respectively pass through the eight detection holes on the outer circumference of the deformation gauge shell, so as to detect the strain in the rock body to be measured. The stress relief method is used to measure the deformation of the rock mass; through the calibrated strain and deformation relationship, the deformation of the measuring hole diameter is calculated and obtained, and the in-situ stress is calculated according to the deformation.

Description

A High Sensitivity Borehole Deformometer for Measuring Ground Stress

technical field

The utility model relates to the geostress measurement mainly used in rock mass, belongs to the technical field of geotechnical engineering, and specifically refers to a high-sensitivity drilling deformation gauge for measuring geostress.

Background technique

In-situ stress is a kind of stress existing in rock mass. It is not only the main factor in the evaluation of geological environment and crustal stability, but also one of the important data for geological engineering design and construction. At present, the most widely used stress measurement methods in engineering are hydraulic fracturing method and casing stress relief method. Since the hydraulic fracturing method has the limitation that it must be assumed in advance that a main direction of the stress tensor is consistent with the borehole axis, the casing stress relief method is considered to be an ideal method for obtaining three-dimensional stress due to its reliability and stability. Test Methods. The deformation method and the strain gauge method are widely used in the casing release method, and there are mainly the following two methods:

(1) Assembly technology and field application of 36-2 drilling deformation gauge in rock and soil mechanics (1983, volume 4, phase 1);

(2) Rock and Soil Mechanics (1987, Volume 8, Issue 3) Hollow inclusion type hole wall strain gauge.

In the casing stress relief method, there are generally two methods: the deformation method and the strain gauge method. The accuracy and reliability of the strain gauge method are not high, and the operation is troublesome; while the operation of the deformation method is relatively convenient, and the accuracy and reliability are high. Therefore, the most commonly used method is the casing stress relief method of the deformation method.

The 36-2 borehole deformation gauge is the most widely used casing relief method in engineering, and its sensor is a steel ring sensor. During the casing stress relief process, the borehole deformation caused by stress release is converted into the deformation of the steel ring. However, for weak rocks, the sensor of the 36-2 borehole deformation gauge has a relatively high rigidity, and the contact head will exert a large pressure on the borehole wall and crush the rock at the contact point. The measured deformation is greater than the actual borehole deformation, resulting in relatively large big error. Under normal circumstances, the hard rock subjected to the stress relief method has small borehole deformation, and the sensitivity of the 36-2 borehole deformation gauge is low, which makes the measurement accuracy not high. At the same time, the sensor of the 36-2 drilling deformation gauge is not easy to paste the strain gauge, and the recovery rate is low.

How to effectively measure various rock masses, especially those with small aperture deformation, to ensure that the detection results are credible and highly sensitive, has always been a difficult problem recognized by those skilled in the art and the direction of hard work, but so far there is no satisfactory solution. Technical solutions come out.

Contents of the invention

The purpose of this utility model is to provide a high-sensitivity drilling deformation gauge for measuring ground stress. The inside of the deformation gauge housing described above is arranged in turn: a cylindrical lock seat bolt is arranged along the central axis, and four sets of ring sensors and three sensor seats are sequentially arranged on the lock seat bolts at intervals; each set of ring type The sensor is provided with two inductive resistors; each of the inductive resistors is respectively connected to the wires in the data cable; the data cable passes through the terminal board at the bottom of the lock seat bolt and is placed on the tapered card via the cable compression ring. Lead out from the tail of the tensioner;

Each group of ring sensors is composed of two thick arc-shaped steel sheets and two thin arc-shaped steel sheets connected end-to-end; A piece of sensing resistor; the normal central axis of each group of sensing resistors coincides and passes through the center O of the outer circumference of the ring sensor; each piece of thick arc-shaped steel sheet is provided with a sensing contact on the top center of the outer arc of the arc; all The central axis of the above-mentioned sensing contact passes through the center O of the outer circumference of the ring sensor;

On each ring sensor, the central axes of the two sensing contacts and the normal central axes of the two sensing resistors are perpendicular to each other and intersect at the center O of the outer circumference of the ring sensor;

The eight sensing contacts on the four sets of ring sensors respectively pass through the eight detection holes on the outer circumference of the deformation gauge shell.

In the above technical solution, the eight detection holes outside the deformation gauge casing are divided into four groups, corresponding to four groups of ring sensors; with the central axis of the deformation gauge casing as the axis, a group of detection holes adjacent to each other in the deformation gauge casing Rotate successively on the circumference with a difference of 45°.

In the above technical solution, the two thick arc-shaped steel sheets in the ring sensor are circular arc sheets of the same size, and the arc angle is between 90° and 180°.

In the above technical solution, the two thin arc-shaped steel sheets in the ring sensor are circular arc sheets of the same size, and the arc angle is between 90° and 180°.

In the above technical scheme, the two ends of each thick arc-shaped steel sheet are provided with thick arc-shaped steel sheet screw holes, and the central axis of the thick arc-shaped steel sheet screw holes passes through the center O of the outer circle of the ring sensor; each thin arc-shaped steel sheet Both ends of the shaped steel sheet are provided with thin arc-shaped steel sheet screw holes, and the central axis of the thin arc-shaped steel sheet screw hole passes through the center O of the outer circle of the ring sensor; the thick arc-shaped steel sheet on each thick arc-shaped steel sheet There is a stepped groove at the screw hole, the thickness and width of the stepped groove are the same as those of the thin arc-shaped steel sheet; two thin arc-shaped steel sheets and two thick arc-shaped steel sheets are connected end to end , the thin arc-shaped steel sheet is inserted into the stepped groove of the rear arc-shaped steel sheet screw hole of the thick arc-shaped steel sheet, when the thin arc-shaped steel sheet screw hole and the thick arc-shaped steel sheet screw hole are aligned, The central axis of the thin arc-shaped steel sheet screw hole and the thick arc-shaped steel sheet screw hole in the corresponding position coincide and pass through the outer circle center O of the outer ring sensor, and the corresponding thin arc-shaped steel sheet screw hole and thick arc-shaped steel sheet screw hole The holes are fixed with screws to form a ring sensor.

The high-sensitivity drilling deformation gauge designed by the utility model changes the structural form of the existing sensor, and uses a combined ring sensor to replace the steel ring sensor in the 36-2 drilling deformation gauge. The ring type sensor adopted by the utility model is composed of thin and thick arc-shaped steel sheets. The design of the thin and thick arc-shaped steel sheets adopts an appropriate thickness, so as to ensure that when the stress is relieved, the thick arc-shaped steel sheet only undergoes rigid body translation, and the thin arc-shaped steel sheet only undergoes bending deformation. Therefore, the sensing resistance sheet on the thin arc-shaped steel sheet can effectively measure the degree of bending deformation of the thin arc-shaped steel sheet, thereby measuring the ground stress.

When the inductive contact has the same displacement, the strain gauge pasted on the ring sensor adopted by the utility model measures much more than the strain gauge measured by the 36-2 drilling deformation gauge strain gauge. Since the thickness of the thin curved steel sheet is significantly smaller than the thickness of the steel ring of the sensor of the 36-2 drilling deformation gauge, the stiffness of the ring sensor designed by the utility model is smaller than that of the original 36-2 drilling deformation gauge. Rigidity of the steel ring; less stress at the contact point of the sensing contact with the borehole wall, easier to measure.

The ring sensor adopts a combined structure, and the thin and thick curved steel sheets of each part are detachable. It is more convenient to paste the sensing resistor on the thin curved steel sheet, and the thick curved steel sheet can be recycled repeatedly. The structure of each ring sensor is stable, and it is not easily affected by the rotational vibration of the casing drill during the stress relief process.

The indoor sensitivity calibration of the ring sensor and the use of the field directional device ensure the rationality of the test results. After obtaining the strain data of the deformation gauge, the ground stress value and orientation of the measurement plane can be quickly calculated on site.

The utility model has the advantages of reasonable design, simple structure, high sensitivity and good stability, and is suitable for ground stress measurement of the casing stress relief method of soft and hard rocks.

Description of drawings

Fig. 1 is the structural representation of the borehole deformation meter designed by the utility model.

Figure 2 is a distribution diagram of the contact positions of the drilling deformation gauge.

Figure 3 is a schematic diagram of the installation structure of the steel sheet sensor in the drilling deformation gauge.

Fig. 4 is a schematic diagram of the equipment structure when the borehole deformation gauge measures the rock mass.

Fig. 5 is a schematic diagram of drilling casing holes on the rock mass to be measured.

Fig. 6 is a schematic diagram of a detection hole drilled on a rock mass to be measured.

Fig. 7 is a schematic diagram of the installation of the borehole deformation gauge in the detection hole on the rock mass to be measured.

Fig. 8 is a schematic diagram of the measurement of the borehole deformation gauge on the rock mass to be measured.

Fig. 9 is a schematic diagram of the installation of the borehole deformation gauge when measuring the rock mass.

Fig. 10 is a schematic diagram of the horizontal included angle of the marking points on the probe of the deformation gauge when measuring the rock mass.

Fig. 11 is a graph showing the relationship between the relief distance of the casing drill and the strain corresponding to each ring sensor in the embodiment.

In the figure: ring sensor 1, sensor seat 2, sensor contact 3, sensor seat cover 4, lock seat bolt 5, wiring board 6, cable compression ring 7, compression nut 8, deformation gauge head 9, deformation Meter housing 10, tapered clamp 11, data cable 12, thick arc-shaped steel sheet 13, thin arc-shaped steel sheet 14, sensing resistor sheet 15, detection hole 16, ring sensor outer circumference 17, ring sensor outer circumference Center of circle O, measuring hole 18, set hole 19, deformation gauge probe 20, static strain gauge 21, marking point 22.

Detailed ways

The device and detection method of the present invention will be further described in detail below in conjunction with the accompanying drawings and specific embodiments.

Structure of High Sensitivity Borehole Deformometer

The high-sensitivity drilling deformation gauge shown in Figures 1 to 3 includes the following parts: the head is the deformation gauge head 9, the outermost layer in the middle is the deformation gauge shell 10, the tail is a tapered clamp 11, and finally connected with data cable12. The deformation gauge head 9 to the tail of the tapered clamp 11 , excluding the rear data cable 12 is the deformation gauge probe 20 .

The deformation gauge head 9 is hemispherical, with a hemispherical protrusion at the center of the top end. The bottom of the deformation gauge head 9 is installed on the deformation gauge housing 10 . The deformation gauge housing 10 is a hollow cylinder with the same diameter as the deformation gauge head 9 . A tapered clamp 11 is installed at the rear of the deformation gauge housing 10 through a compression nut 8 .

There are eight detection holes 16 on the outer circumference of the deformation gauge housing 10 , which are divided into four groups of detection holes 16 . The two detection holes 16 on the same outer circumference of the deformation gauge housing 10 form a group; the central axes of the two detection holes 16 of each group coincide and pass through the center of the outer circumference of the deformation gauge housing 10 . The centers of the outer circumferences of the deformation gauge housing 10 are all on the central axis of the deformation gauge housing 10 . On the outer circumference of the deformation gauge housing 10 , a group of adjacent detection holes 16 are sequentially different from each other by 45° on the circumference relative to the central axis of the deformation gauge housing 10 .

The inside of the deformation gauge housing 10 is a cylindrical cavity, and the following components are arranged in sequence: a cylindrical lock seat bolt 5 is arranged along the central axis, and four sets of ring sensors 1 and three ring sensors 1 are sequentially set on the lock seat bolt 5. A sensor seat 2; the bottom of the lock seat bolt 5 is equipped with an annular terminal block 6. Between two adjacent groups of ring sensors 1 is a sensor seat 2 , behind the last group of ring sensors 1 is a sensor seat cover 4 . The ring sensor 1 , the sensor seat 2 , the sensor seat cover 4 and the wiring board 6 are all ring structures, and are set on the locking seat bolt 5 in an orderly fashion.

Each group of ring sensors 1 is a ring-shaped structure of the same size, and the outermost circle of the ring sensor 1 is a circle, that is, the outer circumference of the ring sensor 17, except for the two sensing contacts 3, and its center is the center O of the outer circumference of the ring sensor. The center O of the outer circumference of the ring sensor is on the central axis of the ring sensor 1 . After the ring sensor 1 is installed in the deformation gauge housing 10, the central axis of the ring sensor 1 coincides with the central axis of the deformation gauge housing 10, and the outer circle center O of the ring sensor and the outer circumference circle center of the deformation gauge housing 10 coincide.

Each group of ring sensors 1 is composed of two thick arc-shaped steel sheets 13 and two thin arc-shaped steel sheets 14 connected end-to-end alternately, and connected with each other by four screws. The outermost circular arc of each thick curved steel sheet 13 and each thin curved steel sheet 14 is on the outer peripheral circle 17 of the ring sensor, and the center of the circle is the center O of the outer peripheral circle of the ring sensor.

The thickness of each thick arc-shaped steel sheet 13 is 1.2 mm, and the thickness of each thin arc-shaped steel sheet 14 is 0.3-0.5 mm. The thickness of the thin arc-shaped steel sheet 14 can be based on actual measurement needs, a thicker thin arc-shaped steel sheet 14 is used for a harder rock mass, and a thinner thin arc-shaped steel sheet 14 is selected for a softer rock mass.

Each thick arc-shaped steel sheet 13 is an annular arc sheet of the same size, and the arc angle is between 90° and 180°. Both ends of each thick arc-shaped steel sheet 13 are provided with thick arc-shaped steel sheet screw holes 13a, and the central axis of the thick arc-shaped steel sheet screw holes 13a passes through the center O of the outer circumference of the ring sensor. An induction contact 3 is arranged on the top center of the outer arc of each thick arc-shaped steel sheet 13 . The sensing contact 3 is in the shape of a cylinder, and the top is a hemisphere with the same diameter as the cylinder. The central axis of the sensing contact 3 passes through the center O of the outer circumference of the ring sensor.

Each thin arc-shaped steel sheet 14 is an annular arc sheet of the same size, and the arc angle is between 90° and 180°. Both ends of each thin arc-shaped steel sheet 14 are provided with a thin arc-shaped steel sheet screw hole 14a, and the central axis of the thin arc-shaped steel sheet screw hole 14a passes through the center O of the outer circumference of the ring sensor. A group of sensing resistance sheets 15 is arranged at the center of the arc of each thin arc-shaped steel sheet 14 . Each group of sensing resistors 15 includes two arc-shaped sensing resistors 15 of the same size. A sensing resistance sheet 15 is pasted on the inner and outer sides of the arc center position of each thin arc-shaped steel sheet 14 correspondingly. The central axes in the normal direction of each group of sensing resistors 15 coincide and pass through the center O of the outer circumference of the ring sensor.

The screw hole 13a of each thick curved steel sheet 13 is provided with a stepped groove whose thickness and width are the same as those of the thin curved steel sheet 14 . Two thin curved steel sheets 14 and two thick curved steel sheets 13 are connected end-to-end alternately, and the thin curved steel sheets 13 are inserted into the rear curved steel sheet screw holes 13a of the thick curved steel sheets 13 On the stepped groove, when the thin arc-shaped steel sheet screw hole 14a and the thick arc-shaped steel sheet screw hole 13a are aligned, the central axes of the thin arc-shaped steel sheet screw hole 14a and the thick arc-shaped steel sheet screw hole 13a at the corresponding positions are heavy. Combine and pass through the center O of the outer circumference of the outer ring sensor, and fix the corresponding thin arc-shaped steel sheet screw holes 14a and thick arc-shaped steel sheet screw holes 13a with screws to form a ring sensor 1 .

At this time, on the ring sensor outer circumference 17 on the outer circumference of each ring sensor 1: the central axes of the two sensing contacts 3 coincide and pass through the center O of the ring sensor outer circumference; the same group of sensing resistors on different thin arc steel sheets 14 The normal central axis of the sheet 15 coincides and passes through the center O of the outer circumference of the ring sensor; the central axes of the two sensing contacts 3 and the central axes of the same group of sensing resistance sheets 15 on different thin arc-shaped steel sheets 14 are mutually perpendicular to the ring The center O of the outer circumference of the sensor.

In the deformation gauge housing 10, when using the lock seat bolt 5 to install the four ring-type sensors 1: the four ring-type sensors 1 are connected in series front and back, and have a phase difference of 45° in sequence; each group of ring-type sensors The central axes of the two sensing contacts 3 on the sensor 1 rotate sequentially on the outer circumference 17 of the ring sensor with a difference of 45°; Protruding from the middle, used to measure rock mass.

After the four ring sensors 1 are installed in the above manner, the two sensing resistors 1 on each group of ring sensors 1 are respectively connected to the wires in the data cable 12 for data signal transmission. The data cable 12 is drawn out through the tapered clamp 11 after passing through the cable compression ring 7 . The deformation gauge casing 10 is connected with the tapered clamp 11 through a compression nut 8 .

Working Principle of High Sensitivity Borehole Deformometer

The purpose of the utility model is to measure the ground stress in the rock body. In-situ stress measurement is divided into three-dimensional stress measurement in space and plane stress measurement. Plane stress measures the two-dimensional stress on a plane perpendicular to the measurement hole.

The plane ground stress measured by the utility model is the ground stress on the cross section perpendicular to the measuring hole.

The working principle of the high-sensitivity drilling deformation gauge designed by the utility model is: to measure the displacement during the drilling deformation process of the rock mass, and transmit it.

Specifically, the following method is adopted: firstly drill a section of casing drilling in the area to be tested, and then drill a probe hole coaxially at the bottom of the casing drilling hole, put the annular drill bit in the exploration hole and drill coaxially with the casing drilling to reduce the strain The stress constraint of the surrounding rock mass is relieved, so it is called the stress relief method. After the stress constraint is released, the rock mass around the strain gauge deforms, and the strain gauge generates strain. Through the calibrated strain and deformation relationship, the deformation of the measuring hole diameter is calculated and obtained, and the in-situ stress is calculated according to the deformation.

In the utility model, the deformation gauge is located in the borehole. When deformation occurs, the sensing contact 3 will be displaced accordingly, and at the same time, it will drive the thick arc-shaped steel sheet 13 to undergo a synchronous rigid body translation, prompting the thin arc-shaped steel sheet 14 to undergo synchronous motion. Bending deformation; at this time, a great strain change will be produced at the position of the sensing resistor 15; thus, the deformation of the drilled hole is reflected at the position of the sensing resistor 15, and is converted from the deformation amount by the sensing resistor 15 to electric signal.

Theoretically, the angle of the measuring hole can be arbitrary, but in actual operation, the most widely used ones are horizontal and nearly horizontal.

Detection steps of high-sensitivity drilling deformation gauge

As shown in Figures 4 to 11, when the high-sensitivity drilling deformation gauge designed by the utility model is used, the one that is put into the measuring hole 18 is called the deformation gauge probe 20, and the data cable 12 at its tail is connected to the static strain gauge 21 and then connected to the indoor computer to read and store data and calculate results.

Utilize the method that the high-sensitivity borehole deformation gauge designed by the utility model detects rock mass, comprise the following steps:

Step 1) Calibrate the sensitivity K of the high-sensitivity borehole deformation gauge on the indoor calibration table, and determine the corresponding relationship between the variation of the strain gauge reading and the ground stress;

δ=Δε/K (Formula 1)

Among them, K is the sensitivity of the strain gauge obtained after calibration (με/10 ^-3 mm);

Δε (unit: με) is the difference in readings of the deformation gauge when the casing drill is released initially and when the casing drill reaches 30cm;

Taking steel ring No. 1 in Table 1 as an example, when the casing drill penetrates 0cm, the strain reading is 0, and when the casing drill reaches 30cm, the strain reading is 266, then Δε=266με at this time.

δ (mm) represents the amount of aperture deformation of the measurement hole 18 .

$\left.\begin{array}{c}{\mathrm{\σ}}_1\\ {\mathrm{\σ}}_2\end{array}\right\}=\frac{\mathrm{E.}}{4\mathrm{D.}(1-v^2)}\[({\mathrm{\δ}}_0+{\mathrm{\δ}}_{90})\±\frac{1}{\sqrt{2}}\sqrt{{({\mathrm{\δ}}_0-{\mathrm{\δ}}_{45})}^2+{({\mathrm{\δ}}_{45}-{\mathrm{\δ}}_{90})}^2}$ (Formula 2)

$ta\mathrm{no}2\mathrm{\α}=\frac{2{\mathrm{\δ}}_{45}-({\mathrm{\δ}}_0+{\mathrm{\δ}}_{90})}{{\mathrm{\δ}}_0-{\mathrm{\δ}}_{90}}$ (Formula 3)

σ ₁ and σ ₂ (Mpa) are plane principal stresses, and α is the angle between σ ₁ and δ ₀ . E (GPa) is the elastic modulus of the rock mass to be tested, and ν (dimensionless) is the Poisson's ratio of the rock mass to be tested. D (mm) is the diameter of the measuring hole 18 .

The four ring sensors 1 in the deformation gauge are sequentially numbered No. 1, No. 2, No. 3, and No. 4 from the head 9 of the deformation gauge, respectively corresponding to the strain in one direction; by the strain amount on each ring sensor 1, The aperture deformations of the measuring holes corresponding to the four ring sensors 1 can be inversely deduced and calculated; if three of the aperture deformations are selected, the corresponding ground stresses can be inversely deduced and calculated. The subscripts 0, 45, and 90 of δ ₀ indicate the phase sequence of the ring sensor 1 corresponding to the three selected aperture deformations, that is, the selected three ring sensors 1 have a phase difference of 45° in sequence (the three ring sensors The central axis of 1 rotates 45° sequentially on the central axis of the deformation gauge housing 10) respectively [No. 1, No. 2, No. 3], [No. 2, No. 3, No. 4], [No. 3, No. 4, No. 1] Number], [No. 4, No. 1, No. 2] four ways.

Step 2) At the test site, connect the high-sensitivity drilling deformation gauge to the static strain gauge 21, and correct the acquisition parameters;

The static strain gauge 21 is a YJ-H4 type static resistance strain gauge. There are two sensing resistors 15 on each group of ring sensors 1, which are connected by a half-bridge. Before the ring sensor 1 attached with the sensing resistor 15 is not deformed, the strain reading of each sensing resistor 15 measured by a static strain gauge is 0, indicating that the voltage of the half-bridge is balanced; the corrected reading is 8888, indicating that the static strain gauge Internal capacitance balancing. Before the on-site measurement starts, strain calibration of the sensing resistor 15 is required. Calibrate the specific parameters: the strain reading is 0, and the calibration reading is 8888.

Step 3) push the high-sensitivity drilling deformation gauge into the measuring hole 18, and record the readings of the static strain gauge 21;

Step 3.1) As shown in Figure 6, at the test site, drill a section of casing 19 in the rock mass area to be measured to reach the target range, and record the azimuth and depth of the casing. Actually, the angle of the measuring hole 18 is consistent with the angle of the trepan. Recording the azimuth of the casing drill has exactly recorded the azimuth of the measuring hole 18.

In the on-site measurement of this embodiment, the boreholes are horizontal boreholes and perpendicular to the direction of the tunnel,

In ground stress tests, the boreholes are generally drilled horizontally and perpendicular to the direction of the tunnel.

Step 3.2) Drilling a measuring hole 18 under the casing hole 19 drilled above; the measuring hole 18 and the casing hole 19 are coaxial but smaller in diameter.

Specifically, the drilling measurement hole 18 is a drill bit with a solid diameter of 36 mm; the drilling casing hole 19 is a drill bit similar to a ring: the inner diameter is 110 mm, and the outer diameter is 120 mm. During drilling, the casing hole 19 and the measuring hole 18 are coaxial concentric circles.

Generally, the depth of the measuring hole 18 in the middle is about 30cm.

Step 3.3) Send the deformation gauge probe 20 into the measurement hole 18 with a push rod, record the orientation of the deformation gauge probe 20 in the measurement hole 18, and record the initial reading of the acquisition host

When the deformation gauge probe 20 of the high-sensitivity drilling deformation gauge is pushed into the measuring hole 18 with a push rod, since the total length of the deformation gauge probe 20 is 22.5 cm, the deformation gauge probe 20 can completely go deep into the measuring hole 18.

At this time, the rear of the deformation gauge probe 20 is followed by an orienter and a push rod, and the push rod sends the deformation gauge probe 20 into the detection controller 18 .

Step 3.4) The casing drill is drilled into the casing hole 19, the rock mass around the measurement hole 18 is stress relieved, and the current reading of the static strain gauge 21 is recorded.

Step 4) Start the orienter, rotate the push rod to adjust the high-sensitivity drilling deformation gauge, measure and record the deep azimuth of the high-sensitivity drilling deformation gauge, the orientation of the drilling hole and the inclination angle of the drilling hole, and then pull out the push rod;

After the deformation gauge is placed in the measuring hole, the deformation gauge will generally rotate the angle, and the angle of change can be measured with the orienter. Before the deformation gauge probe 20 is put into the measuring hole 18, the direction corresponding to the marking point 22 at its tail is vertically upward; at this time, the reading of the orientator is 90°. During the propelling process of the deformation gauge probe 20 into the measurement hole 18, the deformation gauge probe 20 will deflect as a whole.

After the strain gauge probe 20 is put into the measuring hole 18, the orienter is activated to measure the deflection angle of the strain gauge probe 20. Subsequently, the push rod and the orienter are taken out, and the final deflection angle of the deformation gauge probe 20 is read. The original angle is 90°, if there is a clockwise deflection, the angle is considered to decrease; if it is deflected counterclockwise, the angle is considered to increase. In the following actual measurement embodiments, the angle between the marking point 22 on the strain gauge probe 20 and the horizontal direction on the right side is α=-29°, which means that when the strain gauge probe 20 is put into the detection hole 18, it is relatively The horizontal direction is rotated 29° counterclockwise.

When the strain gauge probe 20 is assembled, the connection line corresponding to the marking point 22 at its tail and a contact of No. 3 steel ring (the third from the head) is parallel to the central axis of the strain gauge probe 20; at the same time, the marking point 22 corresponds to the 90° point of the orientator. Therefore, the direction corresponding to the measurement of the eight sensing contacts 3 on the four ring sensors 1 on the high-sensitivity drilling deformation gauge can be determined through the orientator.

Detected drilling position parameters: 1. Drilling depth; 2. Drilling angle. For example, when the borehole is a horizontal borehole (that is, the borehole is on the horizontal plane), it can be at any angle with the side wall of the tunnel (the wall of the underground tunnel); generally, the angle of the borehole is perpendicular to the wall, or at 45° to the wall. ° angle, which is convenient for calculation and analysis.

The specific data is obtained from the actual test.

Step 5) wait for the reading of the static strain gauge 21 to be stable, record it as the initial strain value, then correct the data and zero as in step 2);

When the strain gauge probe 20 is just put into the measuring hole 18, the four ring sensors 1 are deformed due to the contact between the sensing contact 3 and the wall of the measuring hole 18, and the sensing resistor 15 on the ring sensor 1 will generate Change and fluctuate, the reading of static strain gauge 21 also fluctuates, wait for a period of time, reading will stabilize, and at this moment the reading of static strain gauge 21 is the strain value of packing into measuring hole 18.

The purpose of re-zeroing is to ease the reading and calculation of measured data during the lifting process.

Step 6) Drill casing hole 19, carry out stress release to measuring hole 18, in the process of releasing stress, drill into every 2cm, record the readings of each measuring point, when casing drilling drills to 30cm, if the difference between two consecutive readings is the same When it is confirmed to be stable when it exceeds 5με, drilling can be stopped and data recording can be stopped at the same time;

In the ground stress test, the deformation gauge probe 20 is put into the measurement hole 18 first, and then drilled into the casing hole 19 . The drilling distance of the casing hole 19 has a certain relationship with the deformation of the measuring hole 18, because the deformation of the measuring hole 18 corresponds to the deformation of each ring sensor 1 on the strain gauge probe 20. When the casing hole 19 is drilled into 30cm, the influence of casing drilling on the deformation of each ring sensor 1 can be ignored. But at this time, the drill bit of the casing drill is still rotating, which will cause fluctuations in the readings of the sensing resistors 15 of several ring sensors 1 in the deformation gauge. As long as the last two readings fluctuate within 5με, the readings are considered to be stable. .

Step 7) breaking off the rock core, taking out the rock core with a highly sensitive drilling deformation gauge, and reclaiming the deformation gauge probe 20;

Step 8) Substitute the strain value measured on site into the formula (1), formula (2) and formula (3) in step 1), and calculate the in-situ stress of the measured rock mass.

The sensing resistors 15 on the four ring sensors 1 can all measure data, and the formula in step 1) shows that only the data of three ring sensors 1 can be used to calculate the ground stress. The general method is that three of the four ring sensors 1 are selected randomly, that is, there are four combinations, so as to calculate four sets of ground stress values and angles, and then obtain an average value as the detection result.

Field Test Example

The in-situ stress test was carried out in a diversion tunnel in Sichuan, and the relevant data are as follows:

The elastic modulus is E=41.1GPa, the Poisson's ratio is ν=0.22, and the diameter of the measuring hole is D=36mm;

The casing drilling is horizontal and perpendicular to the tunnel wall.

1) Before the strain gauge probe 20 is put into the measuring hole 18, the strain is calibrated first, the main purpose is to balance the half-bridge voltage.

2) 2.a. Push the deformation gauge probe 20 and the orienter behind it together into the measurement hole 18 with a push rod.

2.b. After advancing the strain gauge probe 20, exit the orienter. At this time, the reading displayed by the orientator is that the angle between the marking point 22 on the probe 20 on the deformation gauge and the horizontal direction on the right side is α=-29° (counterclockwise).

Because the relationship between each sensing contact 3 on the four-group ring sensor 1 and the marking point is definite, the angle of each sensing contact 3 on the four-group ring sensor 1 in the measuring hole 18 is calculated indirectly.

2.c. After the deformation gauge probe 20 is pushed into the measuring hole 18, read the reading after the reading on the static strain gauge 21 is stable.

2.d. Calibrate the strain again, the main purpose: when the stress is relieved, each reading is 0, which is convenient for future calculation.

3) Start the casing drill, and record the strain value of each channel every 2cm. When the casing drill reaches around 30cm, compare the difference between the last two data, and if the difference between the two consecutive readings does not exceed 5με, it is confirmed to be stable, and the drilling can be stopped.

4) Substitute the measured data into the calculation formula.

All the data are shown in the stress test measurement data table in Table 1 below.

Table 1 Stress test measurement data

After calculating the above measurement data, the relationship diagram of the relief distance of the casing drill and the strain corresponding to each ring sensor in Fig. 11 is obtained.

Correspondingly, K, Δε, δ measured by different ring sensors 1 are shown in Table 2:

Deformometer sensitivity K (με/10 ^-3 mm) obtained by calibration;

The deformation gauge reads Δε (ie με) from the time when the casing drill is released to the point where the drilling reaches 30cm;

Aperture deformation of the measuring hole δ(mm);

Table 2: K, Δε, δ measured by different ring sensors:

Ring Sensor Number Reading difference Δε (unit με) K(με/10 ^-3mm ) δ( ^10-3 mm) number 1 266 9.4 28.3 number 2 653 9.6 68 number 3 392 9.2 46.2 No 4 -7 8.7 -0.8

σ ₁ , σ ₂ measured by the corresponding ring sensor 1 with different phases δ ₀ , δ ₄₅ , δ ₉₀ and the formed angle, as shown in Table 3 below:

Table ₃ : The measured _{σ 1} , _{σ 2} and the formed horn:

The angle is the angle (°) formed by σ ₁ and the horizontal direction to the right:

n represents the number of the ring sensor 1 corresponding to δ ₀ (counting from the head), and 112° is the reading measured by the orientator in this test.

The range of values is -90°～90°, all values greater than 90° 180° needs to be subtracted. In Table 3, the third group δ ₀ is calculated The actual result is 151°, which is -29° after subtracting 180°; actually these two angles are on a straight line.

Calculate four sets of ground stress values and angles, and then get the average value as the test result:

Maximum principal stress = 29.7MPa;

Minimum principal stress = 9.65MPa;

Principal stress direction = -29° (with the horizontal right as the starting line, rotate 29° clockwise).

Other unspecified parts belong to the prior art.

Claims (6)

1. measure the high sensitivity borehole deformeter of terrestrial stress for one kind, head is deformation gauge head (9), middle part is the tubular deformation gauge shell (10) of cavity, afterbody is taper clamping device (11), it is characterized in that: described deformation gauge shell (10) inside is disposed with: centrally axis is provided with tubular lock bolt (5), spacedly successively on described lock bolt (5) be set with four groups of ring type sensors (1) and three sensor holders (2); Often organize on ring type sensor (1) and be provided with two inductive reactance sheets (15); Described each inductive reactance sheet (15) is connected to the electric wire in data cable (13) respectively; Described data cable (13) is drawn at taper clamping device (11) afterbody via cable compacting ring (7) by the terminal block (6) of the bottom of lock bolt (5);

Each described group ring type sensor (1) is connected to form by the thick arc steel plate of two panels (13), the thin arc steel plate of two panels (14) alternate head and the tail; A slice inductive reactance sheet (15) is pasted accordingly respectively in the inside and outside both sides of the center of arc position of the thin arc steel plate of every sheet (14); Often organize the central axes of the normal direction of inductive reactance sheet (15) and pass the center of circle O that (17) are justified in ring type sensor periphery; Induction contact (3) is provided with in the heart in the circular arc outside top of the thick arc steel plate of every sheet (13); The central axis of described induction contact (3) passes the center of circle O of ring type sensor periphery circle (17);

On each group of ring type sensor (1), the central axis of two induction contact (3) and the central axis of the normal direction of two inductive reactance sheets (15) are mutually vertical and intersect at the center of circle O that (17) are justified in ring type sensor periphery;

Four groups of upper eight induction contact (3) of ring type sensor (1) are each passed through eight detect aperture (16) on described deformation gauge shell (10) periphery.

2. a kind of high sensitivity borehole deformeter measuring terrestrial stress according to claim 1, it is characterized in that: described deformation gauge shell (10) eight detect aperture (16) are outward divided into four groups, corresponding four groups of ring type sensors (1); With the central axis of deformation gauge shell (10) for axle, one group of adjacent between two detect aperture (16) deformation gauge shell (10) circumferentially rotates difference 45 ° successively.

3. a kind of high sensitivity borehole deformeter measuring terrestrial stress according to claim 1, it is characterized in that: the arc plate that the thick arc steel plate of two panels (13) in described ring type sensor (1) is the annular of equal size, arc angle is between 90 ° ~ (18) 0 °.

4. a kind of high sensitivity borehole deformeter measuring terrestrial stress according to claim 1, it is characterized in that: the arc plate that the thin arc steel plate of two panels (14) in described ring type sensor (1) is the annular of equal size, arc angle is between 90 ° ~ 180 °.

5. a kind of high sensitivity borehole deformeter measuring terrestrial stress according to claim 1, it is characterized in that: the two ends of every thick arc steel plate of sheet (13) are provided with thick arc steel plate screw (13a), the central axis of this thick arc steel plate screw (13a) is through the round heart O in ring type sensor periphery, the two ends of the thin arc steel plate of every sheet (14) are provided with thin arc steel plate screw (14a), and the central axis of this thin arc steel plate screw (14a) is through the round heart O in ring type sensor periphery, thick arc steel plate screw (13a) position on the thick arc steel plate of every sheet (13) is provided with step-like recesses, and thickness and the width of the thickness of this step-like recesses and width and thin arc steel plate (14) are identical, thin for two panels arc steel plate (14) is connected with the thick arc steel plate of two panels (13) alternate head and the tail, described thin arc steel plate (13) inserts on the step-like recesses of the rear arc steel disc screw (13a) of described thick arc steel plate (13), when thin arc steel plate screw (14a) and thick arc steel plate screw (13a) align, the thin arc steel plate screw (14a) of correspondence position and the central axes of thick arc steel plate screw (13a) are also through the round heart O in outer ring sensor periphery, the thin arc steel plate screw (14a) of correspondence and thick arc steel plate screw (13a) are screwed, form a ring type sensor (1).

6. a kind of high sensitivity borehole deformeter measuring terrestrial stress according to claim 1, it is characterized in that: the thickness of the thick arc steel plate (13) in described ring type sensor (1) is 1.2mm, the thickness of thin arc steel plate (14) is 0.3 ~ 0.5mm.