A) Measure the direction of rocks with a geological compass.
When measuring the strike of rock strata, put one side of the long side of the compass (the side marked parallel to N-S on the compass) close to the horizon, and then slowly rotate the compass (note: during the rotation, no point near the horizon of the compass can leave the horizon), so that the bubble of the circular level is centered and the magnetic needle stops swinging. At this time, the reading pointed by the magnetic needle is the direction of the rock stratum. You can read the magnetic north needle or the magnetic south needle, because the strike of rock strata extends in two directions, with a difference of 180. For example, the strike of the rock stratum is 60 or 240.
B) measure the inclination of rock with geological compass.
When measuring the inclination, point the northern end of the compass to the inclined direction of the plane, so that the short side of the compass (that is, the S side) is close to the plane and is flat, and rotate the compass. The rotation method and principle are the same as above, and the reading pointed by the compass is the desired inclination. The inclination angle has only one direction and can only be expressed by a numerical value. If the dip angle of rock stratum is 150.
If it is difficult to measure at the top or bottom of the rock stratum, it can also be measured at the bottom of the rock stratum. Or use a long observation mark to point to the inclined direction of the rock stratum, and the northern end of the compass is close to the bottom. Just read the north pointer. If it is difficult to read the north needle when measuring the bottom surface, the southern end of the compass can be close to the bottom surface of the rock, and the S needle can also be read.
C) Measure the dip angle of rocks with geological compass.
When measuring the inclination angle, erect the compass so that its long side is close to the plane and perpendicular to the strike line, and move the compass with the middle finger so that the bubble of the level (long level) is located in the center of the inclinometer. At this time, the reading of the semi-circular dial pointed by the cursor on the inclinometer is the inclination angle. The dip angle varies from 0 to 90, for example, the dip angle of a rock stratum is 35.
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Detailed usage of compass
Measure the occurrence factors of rock strata
(1) measuring tool-geological compass
General geological survey, such as measuring the orientation of objects, the spatial position of rock strata, the slope of mountains, etc. , all with geological compass. This is a tool that geologists must master. There are many kinds of geological compasses, but their principles and structures are basically the same.
① Basic structure of geological compass
Generally, it consists of a magnetic needle, a magnetic needle brake, a dial, an inclinometer, a level and a sight. , and installed on the non-magnetic chassis (as shown in Figure 5- 1).
Figure 5- 1 Geological Compass Structure Diagram
1- reflector; 2- aiming plate 3- magnetic needle; 4- Horizontal dial; 5— Vertical dial; 6— Inclinometer needle (or hanging hammer);
7— Rectangular level; 8- circular level; 9— Magnetic needle brake; 10-thimble; 1 1 pole; 12- glass cover; 13-compass chassis
The magnetic needle is a magnetic steel needle with two sharp ends, and its center is placed on the thimble of the central shaft of the chassis for flexible swing. Because China is located in the northern hemisphere, the magnetic attraction at both ends of the needle is not equal, which leads to magnetic tilt. In order to make the magnetic needle in a balanced state, several turns of copper wire are wound at the southern end of the magnetic needle to adjust the center of gravity of the magnetic needle, which can also be used to distinguish the guide from the compass.
The magnetic needle brake is a free ring sleeved at the lower end of the shaft supporting the magnetic needle. This ring is connected with the brake knob through a lever, which can make the magnetic needle leave the thimble of the rotating shaft and be consolidated, thus protecting the thimble and the rotating shaft from abrasion, maintaining the sensitivity of the instrument and prolonging the service life of the compass.
The dial is divided into two circles: the inner (lower) circle and the outer (upper) circle. The inner ring is a vertical dial, which is specially used to measure inclination and inclination angle. The center position is 0, and it is recorded to both sides every 10 until 90. The outer ring is a horizontal dial, and there are two calibration methods, namely azimuth angle and quadrant angle, which vary with different compasses. The azimuth dial starts from 0 and records counterclockwise every10 until 360. Mark n and s at 0 and 180 respectively (indicating north and south); As shown in the figure, e and w (indicating east and west) are marked at 90 and 270 respectively. Quadrant angle dial is different from it in that both ends of S and N are marked as 0, and both ends of E and W are marked as 90, that is, the dial is divided into four quadrants: 0-90.
It must be noted that the azimuth dial is marked counterclockwise. The east and west directions marked by the two dials are opposite to the magnetic field direction, and their purpose is to directly read out the magnetic azimuth angle and magnetic quadrant angle during measurement. Because the magnetic needle is relatively static when measuring, it moves the compass chassis. When the chassis moves eastward, it is equivalent to the magnetic needle moving westward, so it is necessary to read the counterclockwise mark on the dial (the east-west direction is opposite to the magnetic field direction). In specific work, in order to distinguish whether the reading value is azimuth or quadrant angle, the following methods can be used: As shown in Figures A and B, the measuring lines are at the same position, which is read as 285 on the azimuth dial, recorded as NW285 or 285 on the quadrant dial and recorded as N 75 W on the quadrant dial. If both are in the first quadrant, such as 50, the latter is recorded as N50 E to show the difference (Figure 5-2 A, B, Table 5- 1).
Inclinometer pointer (or hanging hammer) is an important part of inclinometer, which is placed on the chassis. When measuring, the degree of the vertical plate pointed by the pointer (or hanging hammer tip) is the value of inclination or inclination angle.
There are usually two levels on the compass: the circular one is fixed on the chassis and the tubular one is fixed on the inclinometer. When the bubble is in the center, it means that the compass chassis and the long-side compass surface are in a horizontal state. But if the inclinometer is a swinging hanging cone, there is no tubular level.
The sight includes an eye-catching catching board, a filament in the reflector and a transparent hole below it, which is used to aim at the measurement target (terrain and ground objects).
(2) the use of geological compass
It is necessary to correct the magnetic declination before use, because the positions of the geomagnetic north and south poles are not exactly the same as those of the geographical north and south poles, that is, the magnetic meridian does not coincide with the geographical meridian, and the included angle between them is called the magnetic declination. Regularly calculate the magnetic declination of each point on the earth and publish it for future reference. When the magnetic north of a point on the earth deviates to the east of the true north direction, it is called eastward deviation (recorded as+); When it leans to the west, it is called westward deviation (recorded as-). If the magnetic declination (δ) of a point is known, the relationship between the magnetic azimuth (A magnetic) and the true north azimuth (A) of the survey line is A=A magnetic δ. As shown in Figure 5-3 A, when δ is 30 east and the angle measured by the survey line is NE30, then A = 30+30 = Ne60；; Fig. 5-3 B shows that the delta is 20 to the west, and the angle measured by the survey line is se110, so a =110-20 = 90. In order to work conveniently, the magnetic declination can be corrected according to the above principle. When the magnetic declination is eastward, turn the scale screw on the outer wall of the compass to make the horizontal dial rotate clockwise by a magnetic declination value (or counterclockwise if it is westward). After the compass is corrected, the measured reading is the correct orientation.
When measuring the direction of the target object, the azimuth of the straight line connecting the target object and the tester is determined. Azimuth refers to the angle from the meridian clockwise to the survey line (as shown in Figure 5-3 C). First, loosen the magnetic needle brake knob, and open the object board to point to the measured object, that is, the north (N) end of the compass points to the object, and the south (S) end is aimed close to itself. Make the target object, the small hole of the object tray and the filament on the cover glass into a straight line, and at the same time make the bubble in the center of the circular level meter. When the magnetic needle is at rest, the degree pointed by the compass is the azimuth of the measured target.
Fig. 5-3A schematic diagram of the eastern magnetic declination; Fig. 5-3B Schematic diagram of the western magnetic declination; Figure 5- 3C compass for measuring the orientation of the target object.
⑵ Determination of rock occurrence factors
The spatial position of rock stratum is determined by its occurrence factors, including the strike, dip and dip angle of rock stratum (see Figure 5-4).
Figure 5-4 Rock Occurrence Elements and Their Measurement Methods
The measurement of strata strike is the direction of intersection between strata and horizontal plane. When measuring, the bottom of the long side of the compass is close to the rock stratum. When the bubble of the circular level is in the center, the degree indicated by the north or compass can be read, that is, it can be required (because the trend line is a straight line, its direction can extend to both sides, so the north and south needles can be read).
The measurement of stratum dip angle refers to the orientation of the downward maximum dip line (true dip line) of stratum projected on the horizontal plane. When measuring, point the northern end of the compass to the downward inclined direction of the rock stratum, and the short side of the southern end leans against the rock stratum. When the bubble of the circular level is in the center, read the degree indicated by the compass.
The measurement of rock dip angle refers to the maximum angle between bedding plane and imaginary horizontal plane, which is called true dip angle. The true dip angle can be measured along the true dip line of the layer. If the dip angle measured along other dip lines is less than the true dip angle, it is called apparent dip angle. When measuring, stand the compass sideways so that the long side of the compass is close to the stratum. Move the adjustable wrench outside the chassis with the middle finger of the right hand and move the compass along the stratum at the same time. When the bubble of the tubular level is centered, the maximum degree pointed by the inclinometer pointer is the true dip angle of the stratum. If the inclinometer is a hanging hammer compass, the method is basically the same as above, except that the middle finger of the right hand presses the button outside the cabinet, and the hanging hammer swings freely. When it reaches the maximum value, loosen the middle finger and hang a hammer to fix the indicating reading, that is, the true dip angle of the rock stratum.
If the azimuth compass is used to record the occurrence of rock strata, and it is found that the strike, dip and dip of a certain stratum are 330, 240 and 50 respectively, it is recorded as 330/SW ∠ 50 or 240 ∠ 50 (that is, only dip and dip can be recorded). If the azimuth compass is used to measure but the quadrant angle is used to record, the azimuth angle should be converted into quadrant angle and then recorded. As for the occurrence of the above strata, the strike should be γ = 360-330 = 30, and the dip angle β = 240- 180 = 60. Its appearance can be recorded as N30 W/SW ∠ 50 or directly as S60W∠50. When the occurrence elements are marked on the geological map or plan, they need to be represented by symbols and dip angles. First, find out the location of the measuring point on the map, draw a short straight line (4mm) at this point according to the measured stratum strike, then draw a short vertical line (2mm) at the middle point of the line segment according to the strike of stratum dip, and then mark the dip value at the lower right of the symbol.
Measure the occurrence factors of rock strata
(1) measuring tool-geological compass
General geological survey, such as measuring the orientation of objects, the spatial position of rock strata, the slope of mountains, etc. , all with geological compass. This is a tool that geologists must master. There are many kinds of geological compasses, but their principles and structures are basically the same.
① Basic structure of geological compass
Generally, it consists of a magnetic needle, a magnetic needle brake, a dial, an inclinometer, a level and a sight. , and installed on the non-magnetic chassis (as shown in Figure 5- 1).
Figure 5- 1 Geological Compass Structure Diagram
1- reflector; 2- aiming plate 3- magnetic needle; 4- Horizontal dial; 5— Vertical dial; 6— Inclinometer needle (or hanging hammer);
7— Rectangular level; 8- circular level; 9— Magnetic needle brake; 10-thimble; 1 1 pole; 12- glass cover; 13-compass chassis
The magnetic needle is a magnetic steel needle with two sharp ends, and its center is placed on the thimble of the central shaft of the chassis for flexible swing. Because China is located in the northern hemisphere, the magnetic attraction at both ends of the needle is not equal, which leads to magnetic tilt. In order to make the magnetic needle in a balanced state, several turns of copper wire are wound at the southern end of the magnetic needle to adjust the center of gravity of the magnetic needle, which can also be used to distinguish the guide from the compass.
The magnetic needle brake is a free ring sleeved at the lower end of the shaft supporting the magnetic needle. This ring is connected with the brake knob through a lever, which can make the magnetic needle leave the thimble of the rotating shaft and be consolidated, thus protecting the thimble and the rotating shaft from abrasion, maintaining the sensitivity of the instrument and prolonging the service life of the compass.
The dial is divided into two circles: the inner (lower) circle and the outer (upper) circle. The inner ring is a vertical dial, which is specially used to measure inclination and inclination angle. The center position is 0, and it is recorded to both sides every 10 until 90. The outer ring is a horizontal dial, and there are two calibration methods, namely azimuth angle and quadrant angle, which vary with different compasses. The azimuth dial starts from 0 and records counterclockwise every10 until 360. Mark n and s at 0 and 180 respectively (indicating north and south); As shown in the figure, e and w (indicating east and west) are marked at 90 and 270 respectively. Quadrant angle dial is different from it in that both ends of S and N are marked as 0, and both ends of E and W are marked as 90, that is, the dial is divided into four quadrants: 0-90.
It must be noted that the azimuth dial is marked counterclockwise. The east and west directions marked by the two dials are opposite to the magnetic field direction, and their purpose is to directly read out the magnetic azimuth angle and magnetic quadrant angle during measurement. Because the magnetic needle is relatively static when measuring, it moves the compass chassis. When the chassis moves eastward, it is equivalent to the magnetic needle moving westward, so it is necessary to read the counterclockwise mark on the dial (the east-west direction is opposite to the magnetic field direction). In specific work, in order to distinguish whether the reading value is azimuth or quadrant angle, the following methods can be used: As shown in Figures A and B, the measuring lines are at the same position, which is read as 285 on the azimuth dial, recorded as NW285 or 285 on the quadrant dial and recorded as N 75 W on the quadrant dial. If both are in the first quadrant, such as 50, the latter is recorded as N50 E to show the difference (Figure 5-2 A, B, Table 5- 1).
Inclinometer pointer (or hanging hammer) is an important part of inclinometer, which is placed on the chassis. When measuring, the degree of the vertical plate pointed by the pointer (or hanging hammer tip) is the value of inclination or inclination angle.
Figure 5-2A Orientation Dial Figure 5-2B Square Angle Dial
Table 5- 1 Conversion Table of Right Angle and Azimuth Angle
Quadrant Azimuth Degree Quadrant Angle (γ) and Azimuth (A) Relationship Quadrant Name
Ⅰ 0-90 γ = a ne quadrant
Ⅱ 90-180γ =180-Arthur quadrant
ⅲ180—270γ = a-180sw quadrant
ⅳ 270-360 γ = 360-A Northwest Quadrant
There are usually two levels on the compass: the circular one is fixed on the chassis and the tubular one is fixed on the inclinometer. When the bubble is in the center, it means that the compass chassis and the long-side compass surface are horizontal respectively. But if the inclinometer is a swinging hanging cone, there is no tubular level.
The sight includes an eye-catching catching board, a filament in the reflector and a transparent hole below it, which is used to aim at the measurement target (terrain and ground objects).
(2) the use of geological compass
It is necessary to correct the magnetic declination before use, because the positions of the geomagnetic north and south poles are not exactly the same as those of the geographical north and south poles, that is, the magnetic meridian does not coincide with the geographical meridian, and the included angle between them is called the magnetic declination. Regularly calculate the magnetic declination of each point on the earth and publish it for future reference. When the magnetic north of a point on the earth deviates to the east of the true north direction, it is called eastward deviation (recorded as+); When it leans to the west, it is called westward deviation (recorded as-). If the magnetic declination (δ) of a point is known, the relationship between the magnetic azimuth (A magnetic) and the true north azimuth (A) of the survey line is A=A magnetic δ. As shown in Figure 5-3 A, when δ is 30 east and the angle measured by the survey line is NE30, then A = 30+30 = Ne60；; Fig. 5-3 B shows that the delta is 20 to the west, and the angle measured by the survey line is se110, so a =110-20 = 90. In order to work conveniently, the magnetic declination can be corrected according to the above principle. When the magnetic declination is eastward, turn the scale screw on the outer wall of the compass to make the horizontal dial rotate clockwise by a magnetic declination value (or counterclockwise if it is westward). After the compass is corrected, the measured reading is the correct orientation.
When measuring the direction of the target object, the azimuth of the straight line connecting the target object and the tester is determined. Azimuth refers to the angle from the meridian clockwise to the survey line (as shown in Figure 5-3 C). First, loosen the magnetic needle brake knob, and open the object board to point to the measured object, that is, the north (N) end of the compass points to the object, and the south (S) end is aimed close to itself. Make the target object, the small hole of the object tray and the filament on the cover glass into a straight line, and at the same time make the bubble in the center of the circular level meter. When the magnetic needle is at rest, the degree pointed by the compass is the azimuth of the measured target.
Fig. 5-3A schematic diagram of the eastern magnetic declination; Fig. 5-3B Schematic diagram of the western magnetic declination; Figure 5- 3C compass for measuring the orientation of the target object.
⑵ Determination of rock occurrence factors
The spatial position of rock stratum is determined by its occurrence factors, including the strike, dip and dip angle of rock stratum (see Figure 5-4).
Figure 5-4 Rock Occurrence Elements and Their Measurement Methods
The measurement of strata strike is the direction of intersection between strata and horizontal plane. When measuring, the bottom of the long side of the compass is close to the rock stratum. When the bubble of the circular level is in the center, the degree indicated by the north or compass can be read, that is, it can be required (because the trend line is a straight line, its direction can extend to both sides, so the north and south needles can be read).
The measurement of stratum dip angle refers to the orientation of the downward maximum dip line (true dip line) of stratum projected on the horizontal plane. When measuring, point the northern end of the compass to the downward inclined direction of the rock stratum, and the short side of the southern end leans against the rock stratum. When the bubble of the circular level is in the center, read the degree indicated by the compass.
The measurement of rock dip angle refers to the maximum angle between bedding plane and imaginary horizontal plane, which is called true dip angle. The true dip angle can be measured along the true dip line of the layer. If the dip angle measured along other dip lines is less than the true dip angle, it is called apparent dip angle. When measuring, stand the compass sideways so that the long side of the compass is close to the stratum. Move the adjustable wrench outside the chassis with the middle finger of the right hand and move the compass along the stratum at the same time. When the bubble of the tubular level is centered, the maximum degree pointed by the inclinometer pointer is the true dip angle of the stratum. If the inclinometer is a hanging hammer compass, the method is basically the same as above, except that the middle finger of the right hand presses the button outside the cabinet, and the hanging hammer swings freely. When it reaches the maximum value, loosen the middle finger and hang a hammer to fix the indicating reading, that is, the true dip angle of the rock stratum.
If the azimuth compass is used to record the occurrence of rock strata, and it is found that the strike, dip and dip of a certain stratum are 330, 240 and 50 respectively, it is recorded as 330/SW ∠ 50 or 240 ∠ 50 (that is, only dip and dip can be recorded). If the azimuth compass is used to measure but the quadrant angle is used to record, the azimuth angle should be converted into quadrant angle and then recorded. As for the occurrence of the above strata, the strike should be γ = 360-330 = 30, and the dip angle β = 240- 180 = 60. Its appearance can be recorded as N30 W/SW ∠ 50 or directly as S60W∠50. When the occurrence elements are marked on the geological map or plan, they need to be represented by symbols and dip angles. First, find out the location of the measuring point on the map, draw a short straight line (4mm) at this point according to the measured stratum strike, then draw a short vertical line (2mm) at the middle point of the line segment according to the strike of stratum dip, and then mark the dip value at the lower right of the symbol.
Quoted from: /read.php? Tid= 10234 1 Please refer to the map.