CN108871509B - Device and method for measuring underground water level by closed method - Google Patents
Device and method for measuring underground water level by closed method Download PDFInfo
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- CN108871509B CN108871509B CN201810642870.7A CN201810642870A CN108871509B CN 108871509 B CN108871509 B CN 108871509B CN 201810642870 A CN201810642870 A CN 201810642870A CN 108871509 B CN108871509 B CN 108871509B
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- 238000000034 method Methods 0.000 title claims abstract description 47
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 title claims abstract description 37
- 238000007789 sealing Methods 0.000 claims abstract description 34
- 229910000831 Steel Inorganic materials 0.000 claims abstract description 29
- 239000010959 steel Substances 0.000 claims abstract description 29
- 239000002689 soil Substances 0.000 claims abstract description 25
- 239000003673 groundwater Substances 0.000 claims description 39
- 238000005259 measurement Methods 0.000 claims description 37
- 239000004576 sand Substances 0.000 claims description 8
- 238000012937 correction Methods 0.000 claims description 7
- 239000006260 foam Substances 0.000 claims description 3
- 239000004746 geotextile Substances 0.000 claims description 3
- 238000013102 re-test Methods 0.000 claims description 3
- 238000007596 consolidation process Methods 0.000 abstract description 12
- 230000003014 reinforcing effect Effects 0.000 abstract description 7
- 239000010410 layer Substances 0.000 description 7
- 230000000694 effects Effects 0.000 description 5
- 230000002787 reinforcement Effects 0.000 description 4
- 230000008878 coupling Effects 0.000 description 2
- 238000010168 coupling process Methods 0.000 description 2
- 238000005859 coupling reaction Methods 0.000 description 2
- 238000010586 diagram Methods 0.000 description 2
- 238000005728 strengthening Methods 0.000 description 2
- 239000002344 surface layer Substances 0.000 description 2
- 239000004568 cement Substances 0.000 description 1
- 238000005056 compaction Methods 0.000 description 1
- 238000005553 drilling Methods 0.000 description 1
- 238000011010 flushing procedure Methods 0.000 description 1
- 239000011521 glass Substances 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 238000012544 monitoring process Methods 0.000 description 1
- 239000012466 permeate Substances 0.000 description 1
- 238000004062 sedimentation Methods 0.000 description 1
- 238000012360 testing method Methods 0.000 description 1
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01F—MEASURING VOLUME, VOLUME FLOW, MASS FLOW OR LIQUID LEVEL; METERING BY VOLUME
- G01F23/00—Indicating or measuring liquid level or level of fluent solid material, e.g. indicating in terms of volume or indicating by means of an alarm
- G01F23/30—Indicating or measuring liquid level or level of fluent solid material, e.g. indicating in terms of volume or indicating by means of an alarm by floats
- G01F23/64—Indicating or measuring liquid level or level of fluent solid material, e.g. indicating in terms of volume or indicating by means of an alarm by floats of the free float type without mechanical transmission elements
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Abstract
The invention discloses a closed-method underground water level measuring device, which comprises an outer pipe, an inner pipe and a steel ruler settlement gauge which are vertically arranged, wherein a closed annular space is formed between the outer pipe and the inner pipe, a magnetic float is arranged in the annular space, the outer pipe is a corrugated telescopic pipe with steel wires, the inner pipe consists of an upper main pipe and a lower limit guide pipe, and a measuring top cover is arranged at the upper end of the lower limit guide pipe; the upper main pipe is inserted in the lower limiting guide pipe, the lower end is sealed, the upper end of the outer pipe is in sealing connection with the sealing film, water seepage holes are formed in the side wall, the upper end of the outer pipe is connected with the sealing top cover, and the measuring head of the steel ruler settlement gauge is arranged in the upper main pipe. The invention also discloses a method for measuring the underground water level by using the device. The invention can simply and conveniently obtain the relatively accurate underground water level elevation of the soft soil foundation in the reinforcing process under the condition that the soil layer consolidation influence is considered and the water level pipe is not communicated with the atmosphere.
Description
Technical Field
The invention belongs to the field of engineering monitoring, and relates to a closed-end method underground water level measuring device and method in the process of reinforcing a soft soil foundation by a vacuum preloading method (or a vacuum preloading combined preloading method).
Background
When the vacuum preloading method is used for reinforcing the soft soil foundation, if the groundwater level is lowered, the vacuum preloading and the dewatering preloading have double reinforcing effects; if the groundwater level rises, the effect of the difference between the two is obtained; if the groundwater level is unchanged, the groundwater level is only a vacuum preloading strengthening effect, so that the groundwater level is accurately measured to relate to the strengthening effect of vacuum preloading, and the understanding of the vacuum preloading mechanism is directly influenced. The common method for measuring the underground water level by the closed method comprises the following steps: the device is composed of two PVC inner and outer tubes with different diameters, a magnetic ring buoy, a limiter, an electric sensor and the like, groundwater permeates between the inner and outer tubes isolated from the atmosphere through water seepage holes on the outer tube wall, and the water level is the groundwater level under the negative pressure condition. The magnetic ring buoys are arranged between the inner pipe and the outer pipe with different diameters and fixed relative positions, float on the water surface, and float freely up and down along the inner pipe along with the groundwater level, namely the position of the magnetic ring buoys is the position of the groundwater surface, and the positions of the magnetic ring buoys can be determined by a steel rule settlement gauge. The method can basically solve the problem that the water level pipe is communicated with the atmosphere, but the device is difficult to ensure that the vacuum degree inside and outside the water level pipe is consistent, and the water level pipe is difficult to ensure not to be communicated with the atmosphere all the time in the reinforcement process of the foundation (particularly in a vacuum preloading combined preloading method) because the influence of soil layer consolidation on the test result is not considered; meanwhile, when the underground water level is measured each time, the upper end Gao Chengcai of the inner pipe is required to be measured, so that the accurate underground water level elevation can be obtained, and the method is relatively complicated. Therefore, it is necessary to study a groundwater level measuring device which considers the effect of soil layer consolidation, can ensure that a water level pipe is not communicated with the atmosphere, and is relatively easy to operate, and provides accurate data support for evaluating the vacuum preloading reinforcement effect.
Disclosure of Invention
The invention provides a device and a method for measuring the groundwater level by a closed-end method, which are used for solving the technical problems in the prior art, so that the relatively accurate groundwater level of a soft soil foundation in the reinforcement process of a vacuum preloading method (or a vacuum preloading combined preloading method) can be obtained simply under the condition that the soil layer consolidation influence is considered and the water level pipe is not communicated with the atmosphere.
The invention adopts a technical scheme for solving the technical problems in the prior art that: the utility model provides a closed method groundwater level measuring device, includes pre-buried 6m long outer tube of vertical setting in soft soil foundation, coaxial cartridge is in inner tube and steel ruler settlement gauge in the outer tube be formed with confined annular space between outer tube and the inner tube be equipped with magnetic force float in the annular space, the outer tube is the ripple flexible pipe that has the steel wire, the inner tube comprises upper portion person in charge and the spacing stand pipe of lower part, the lower part of the spacing stand pipe of lower part with the lower extreme rigid coupling of outer tube is equipped with sealed rubber circle between the two the lower extreme of the spacing stand pipe of lower part is equipped with sealed bottom, sealed bottom exposes in the below of outer tube the upper end of the spacing stand pipe of lower part is equipped with the measurement top cap is equipped with high-strength magnetic path I in the measurement top cap be equipped with spacing hole on the measurement top cap be equipped with the drainage exhaust hole of the spacing stand pipe of lower part on the lateral wall with annular space intercommunication; the upper main pipe passes through a limiting hole in the measuring top cover and is inserted into the lower limiting guide pipe, the upper main pipe is connected with the lower limiting guide pipe through a sliding spline structure, the lower end of the upper main pipe is sealed, the magnetic float is sleeved on the upper main pipe, the upper end of the outer pipe extends out of the upper surface of the soft soil foundation sand cushion and is in sealing connection with a sealing film on the soft soil foundation sand cushion, water seepage holes are formed in the side wall of the outer pipe below the sealing film, geotextile is wrapped outside the outer pipe, the upper end of the outer pipe is connected with a sealing top cover, the upper main pipe passes through the sealing top cover and is in sealing fixed connection with the sealing top cover, and a measuring head of the steel ruler sedimentation instrument is arranged in the upper main pipe.
The magnetic force floater adopts a ring-shaped structure, round corners are arranged at the upper end and the lower end of the inner circle, the magnetic force floater is made of high-pressure rigid foam, and a high-strength magnetic block II is arranged in the magnetic force floater.
The closed bottom cover adopts an inverted cone structure.
The invention adopts another technical scheme for solving the technical problems in the prior art: the method for measuring the groundwater level by using the groundwater level measuring device adopting the closed method comprises the following steps:
first) the elevation H of the upper end of the upper main pipe is guided by a level gauge through a known elevation point during the first measurement S0 The distance L from the magnetic float to the upper end of the upper main pipe is measured by the steel ruler settlement gauge F The distance L from the measuring top cover to the upper end of the upper main pipe is measured through the steel ruler settlement gauge C0 The initial value of the groundwater level elevation is: h A0 ＝H S0 –L F ；
Secondly), after the foundation is solidified and subsided, the distance from the magnetic float to the upper end of the upper main pipe is measured by the steel ruler subsider, and the j-th measured value is L Fj The distance from the measuring top cover to the upper end of the upper main pipe is measured through the steel ruler settlement gauge, and the j-th measured value is L Cj Assume that the measured value (L C0 –L Cj ) For the lowering value of the upper end elevation of the upper main pipe in the jth measurement, the measured value H of the groundwater level elevation is A0,j ＝H S0 -(L C0 -L Cj )-L Fj ；
Wherein:
H A0,j is the measurement of the jth groundwater level elevation (m) (j=1, 2,3, 4..n); h S0 An actual measurement initial value (m) of the upper end elevation of the upper main pipe after the device is embedded; l (L) C0 Measuring an initial value (m) of the distance between the top cover and the upper end of the upper main pipe after the device is embedded; l (L) Cj Measuring the distance (m) from the top cover to the upper end of the upper main pipe for the jth measurement; l (L) Fj The distance (m) between the magnetic float and the upper end of the upper main pipe is the j-th measurement.
Using the following formula to obtain the groundwater level Gao Chengce obtained in the step two)Magnitude H A0,j And (3) correcting:
H Bi,j ＝H Ai,j +[H S0 +L C0 –(1+j/n i )H Si +(j/n i )H S(i+1) –L Ci,j ]
wherein:
H Bi,j a correction value (m) of the jth ground water level elevation measurement value after the ith retest upper main pipe upper end elevation; (i=0, 1,2,3,4., j=1, 2,3,4.,. N.);
H Ai,j the measurement value of the jth ground water level elevation after the ith retest upper end elevation of the upper main pipe is H when i=0 A0,j (m)；
H Si The upper end elevation actual measurement value (m) of the upper main pipe in the ith repetition;
n i the total number of times of measuring the underground water level elevation in the interval time from the ith to the (i+1) th repeated measurement is the number of times of measuring the underground water level elevation in the interval time from the ith to the (i+1) th repeated measurement;
L Ci,j and (3) measuring the distance measurement value (m) from the top cover to the upper end of the upper main pipe for the j-th measurement after the upper end elevation of the upper main pipe is retested for the i-th measurement.
The invention has the advantages and positive effects that:
1) The outer tube adopts the ripple flexible pipe that has the steel wire, and sealing film sealing connection on the soft soil foundation sand bed course and can be along with the consolidation subsidence of soil body and compress, has eliminated the influence of consolidation subsidence to the test, and then guaranteed effectively that the outer tube is airtight not with the atmosphere intercommunication all the time in the foundation reinforcement process.
2) The underground water level is directly measured, and the influence of fluctuation caused by unstable vacuum and hole pressure measuring heads and coupling superposition of the fluctuation is eliminated.
3) When the vacuum preloading method (or the vacuum preloading combined preloading method) is used for reinforcing the soft soil foundation, the surface layer settlement of the foundation mainly comes from the consolidation settlement of soil mass within the depth range of about 6m below the ground, and the consolidation settlement of soil layer within the buried depth range of the device can be measured while the groundwater level is measured, so that the measurement frequency of the upper end elevation of the upper main pipe can be effectively reduced.
4) The correction formula can obtain more accurate underground water level elevation values, and the more times of retesting the elevation of the upper end of the upper main pipe, the higher the precision.
In summary, the invention can accurately obtain the ground water level elevation data in the process of reinforcing the soft soil foundation by the vacuum preloading method (or the vacuum preloading combined preloading method), provides accurate data support for evaluating the reinforcing effect, and has clear principle, simple structure, low manufacturing cost, convenient burying and higher accuracy.
Drawings
FIG. 1 is a schematic diagram of the structure of the present invention;
FIG. 2 is a schematic diagram of the calculation of the corrected groundwater level elevation measurement according to the invention.
In the figure: 1. an outer tube; 2. a lower limit guide tube; 3. an upper main pipe; 4. a magnetic float; 5. measuring the top cover; 6. water seepage holes; 7. sealing the top cover; 8. sealing the rubber ring; 9. closing the bottom cover; 10. a steel ribbon; 11. a seal ring; 12. drainage and exhaust holes; 13. a steel rule settlement gauge; 14. a sealing film; 15. and a sand cushion layer.
Detailed Description
For a further understanding of the invention, its features and advantages, reference is now made to the following examples, which are illustrated in the accompanying drawings in which:
referring to fig. 1, a device for measuring groundwater level by a closed method comprises a vertically arranged 6m long outer pipe 1 pre-buried in a soft soil foundation, an inner pipe and a steel ruler settlement gauge 13 coaxially inserted in the outer pipe 1, wherein a closed annular space is formed between the outer pipe 1 and the inner pipe, a magnetic float 4 is arranged in the annular space, the outer pipe 1 is a corrugated telescopic pipe with steel wires, radial deformation does not occur under 120kPa pressure, the inner pipe consists of an upper main pipe 3 and a lower limit guide pipe 2, the lower part of the lower limit guide pipe 2 is fixedly connected with the lower end of the outer pipe 1, a closed rubber ring 8 is arranged between the lower part and the lower limit guide pipe, and a steel ribbon 9 is adopted for binding. A closed bottom cover 9 is arranged at the lower end of the lower limit guide pipe 2, the closed bottom cover 9 is exposed below the outer pipe 1, a measuring top cover 5 is arranged at the upper end of the lower limit guide pipe 2, a high-strength magnetic block I is arranged in the measuring top cover 5, a limit hole is arranged on the measuring top cover 5, and a water draining and air exhausting hole 12 communicated with the annular space is arranged on the side wall of the lower limit guide pipe 2; the upper main pipe 3 passes through a limiting hole in the measuring top cover 5 and is inserted into the lower limiting guide pipe 2, the upper main pipe 3 is connected with the lower limiting guide pipe 2 through a sliding spline structure, the lower end of the upper main pipe 3 is sealed, and the magnetic float 4 is sleeved on the upper main pipe 3 in an empty mode and can float freely up and down. The upper end of the outer tube 1 protrudes out of the upper surface of the soft foundation sand cushion 15 and is in sealing connection with the sealing film 14 on the soft foundation sand cushion 15, and as the outer tube 1 can deform along with the consolidation of the soft foundation, the sealing film 14 and the outer tube 1 are very reliable and cannot be torn due to the consolidation deformation of the soft foundation. The side wall of the outer pipe 1 below the sealing film 15 is provided with water seepage holes 6, geotextile is wrapped on the outer side of the outer pipe 1, and it is ensured that mud and sand cannot enter the pipe from the water seepage holes 6 on the outer pipe. The upper end of the outer tube 1 is connected with a seal top cover 7, the upper main tube 3 passes through the seal top cover 7, the upper main tube 3 and the seal top cover 7 are fixedly connected in a sealing way, a sealing ring 11 is arranged between the upper main tube 3 and the seal top cover 7, and a measuring head of the steel ruler settlement gauge 13 is arranged in the upper main tube 3.
In this embodiment, the magnetic float 4 adopts a ring structure, rounded corners are arranged at the upper and lower ends of the inner circle, and the magnetic float 4 is made of high-pressure rigid foam, and a high-strength magnetic block II is arranged in the magnetic float 4. The sealing bottom cover 9 adopts an inverted cone structure so as to facilitate the burying of the measuring device.
The measuring device is embedded in the field:
after the vertical drainage channel of the soft soil foundation is completely drilled, the measuring device is buried, and holes of the drilling holes of the buried device are all formed by using the sleeve (high-pressure water flushing is forbidden). Before burying, the device is assembled, but the sealing top cover 7 is not fixed, when burying, firstly, the lower end of the upper main pipe 3 is placed at the bottom of the lower limit guide pipe 2, the burying of the outer pipe 1 in a telescopic state is ensured, after the burying of the device is completed, the sealing film 14 is in sealing connection with the outer pipe 1, then the lower end of the upper main pipe 3 is lifted to the position of the measuring top cover 5, the sealing ring 11 is sleeved on the contact position between the sealing top cover 7 and the upper main pipe 3, and glass cement sealing is arranged, so that the sealing top cover 7 and the upper main pipe 3 are ensured not to displace and leak in the measuring process.
The working principle of the measuring device is as follows:
groundwater is permeated into the annular space between the inner pipe and the outer pipe isolated from the atmosphere through the water seepage holes 6 on the outer pipe 1, and the water level is the groundwater level under the negative pressure condition. The outer pipe 1 can be compressed along with the consolidation settlement of soil body, so that the outer pipe 1 is always isolated from the atmosphere in the foundation reinforcement process, and the distance variation of the measuring top cover 5 to the upper end of the upper main pipe 3 is the consolidation settlement of soil layer within the buried depth range of the inner pipe and the outer pipe. The magnetic force floater 4 placed between the outer pipe 1 and the upper main pipe 3 floats on the water surface and can freely float up and down along the upper main pipe 3 along with the groundwater level, the position of the magnetic force floater 4 is the position of the groundwater surface, and the distance between the magnetic force floater 4 and the upper end of the upper main pipe 3 can be read out through the steel ruler settlement gauge 13.
The method for measuring the underground water level by using the closed-mouth method underground water level measuring device comprises the following steps:
first) the elevation H of the upper end of the upper main pipe is guided by a level gauge through a known elevation point during the first measurement S0 The distance L from the magnetic float to the upper end of the upper main pipe is measured by the steel ruler settlement gauge F The distance L from the measuring top cover to the upper end of the upper main pipe is measured through the steel ruler settlement gauge C0 The initial value of the groundwater level elevation is: h A0 ＝H S0 –L F 。
Secondly), after the foundation is solidified and subsided, the distance from the magnetic float to the upper end of the upper main pipe is measured by the steel ruler subsider, and the j-th measured value is L Fj The distance from the measuring top cover to the upper end of the upper main pipe is measured through the steel ruler settlement gauge, and the j-th measured value is L Cj . Assume a measurement value (L) C0 –L Cj ) Is the lower value of the upper end elevation of the upper main pipe in the j-th measurement, although the lower value of the upper end elevation of the upper main pipe 3 in the j-th measurementThe amount of consolidation settlement for all soil layers of the plant buried site should be measured, not just the measured value (L C0 –L Cj ) However, in actual engineering, the consolidation settlement amount when the soft soil foundation is consolidated by adopting a vacuum preloading method (or a vacuum preloading combined preloading method) generally mainly occurs in the depth range of 6 meters of the surface layer of the foundation soil, so that the measured value (L) C0 –L Cj ) Instead of the upper end elevation drop value of the upper main pipe 3, it is feasible to meet the engineering requirements, and the groundwater level elevation measurement value H A0,j ＝H S0 -(L C0 -L Cj )-L Fj The method comprises the steps of carrying out a first treatment on the surface of the Wherein: h A0,j Is the measurement of the jth groundwater level elevation (m) (j=1, 2,3, 4..n); h S0 An actual measurement initial value (m) of the upper end elevation of the upper main pipe after the device is embedded; l (L) C0 Measuring an initial value (m) of the distance between the top cover and the upper end of the upper main pipe after the device is embedded; l (L) Cj Measuring the distance (m) from the top cover to the upper end of the upper main pipe for the jth measurement; l (L) Fj And 3-bit significant figures are reserved after decimal points of the measured result for the distance (m) between the magnetic float and the upper end of the upper main pipe in the j-th measurement.
In order to obtain a more accurate ground level elevation value, the ground level elevation measurement value H can be obtained by re-measuring the upper end elevation of the upper main pipe 3 by using a level gauge at intervals (correction is recommended once a week in the first month of pre-compaction; and correction is performed once a month later) A0,j The specific method for correction is as follows:
the following formula is adopted to measure the underground water level elevation H obtained in the step two) A0,j And (3) correcting:
H Bi,j ＝H Ai,j +[H S0 +L C0 –(1+j/n i )H Si +(j/n i )H S(i+1) –L Ci,j ]
wherein:
H Bi,j a correction value (m) of the jth ground water level elevation measurement value after the ith retest upper main pipe upper end elevation; (i=0, 1,2,3,4., j=1, 2,3,4.,. N.);
H Ai,j for the measurement of the jth ground water level elevation after the ith retest of the elevation of the upper end of the upper main pipeThe value when i=0 is H A0,j (m)；
H Si The upper end elevation actual measurement value (m) of the upper main pipe in the ith repetition;
n i the total number of times of measuring the underground water level elevation in the interval time from the ith to the (i+1) th repeated measurement is the number of times of measuring the underground water level elevation in the interval time from the ith to the (i+1) th repeated measurement;
L Ci,j and (3) measuring the distance measurement value (m) from the top cover to the upper end of the upper main pipe for the j-th measurement after the upper end elevation of the upper main pipe is retested for the i-th measurement.
The basis of the correction method is as follows:
since the formula H is presented A0,j ＝H S0 -(L C0 -L Cj )-L Fj On the premise that a measured value (L C0 –L Cj ) Is the lowering value of the upper end elevation of the upper main pipe in the j-th measurement, but the actual lowering value of the upper end elevation of the upper main pipe is the consolidation settlement of all soil layers of the embedded part of the device and is larger than the measured value (L C0 –L Cj ). In order to obtain a more accurate ground level elevation, a retest is required to be performed on the elevation of the upper end of the upper main pipe to correct the measured value of the ground level elevation, and in a specific correction method, please refer to fig. 2, considering that in actual engineering, the measurement frequency of the ground level elevation is generally 1 time/day.
S1 in FIG. 2 shows the actual drop value and the measured value (L) of the upper end elevation of the upper main pipe before the upper end elevation of the upper main pipe is retested the ith time C0 –L Ci,0 ) Wherein L is Ci,0 For measuring the distance (m) between the top cover and the upper end of the upper main pipe when the upper end elevation of the upper main pipe is measured for the ith repetition, S1= [ (H) Si –H S0 )–(L C0 –L Ci,0 )]The method comprises the steps of carrying out a first treatment on the surface of the In the figure, S2 represents the actual decrease value and the measured value (L) of the upper end elevation of the upper main pipe in the period from the ith repeated measurement of the upper end elevation of the upper main pipe to the jth measurement of the groundwater level elevation Ci,0 –L Ci,j ) Wherein L is C(i+1),0 ＝L Ci,n 、H A(i+1),0 ＝H Ai,n ，S2＝[j(H Si –H S(i+1) )/n i –(L Ci,0 –L Ci,j )]Correction value H Bi,j ＝H Ai,j -S1-S2, namely: h Bi,j ＝H Ai,j +[H S0 +L C0 –(1+j/n i )H Si +(j/n i )H S(i+1) –L Ci,j ]。
Although the preferred embodiments of the present invention have been described above with reference to the accompanying drawings, the present invention is not limited to the above-described embodiments, which are merely illustrative and not restrictive, and many forms may be made by those having ordinary skill in the art without departing from the spirit of the present invention and the scope of the appended claims, which are within the scope of the present invention.
Claims (3)
1. The device for measuring the underground water level by a closed method comprises a vertically arranged 6m long outer pipe pre-buried in a soft soil foundation, an inner pipe coaxially inserted in the outer pipe and a steel ruler settlement gauge, and is characterized in that,
a closed annular space is formed between the outer tube and the inner tube, a magnetic float is arranged in the annular space,
the outer tube is a corrugated telescopic tube with steel wires,
the inner pipe consists of an upper main pipe and a lower limit guide pipe,
the lower part of the lower limit guide pipe is fixedly connected with the lower end of the outer pipe, a closed rubber ring is arranged between the lower part of the lower limit guide pipe and the lower end of the outer pipe, a closed bottom cover is arranged at the lower end of the lower limit guide pipe and is exposed below the outer pipe, a measuring top cover is arranged at the upper end of the lower limit guide pipe, a high-strength magnetic block I is arranged in the measuring top cover, a limit hole is formed in the measuring top cover, and a drainage exhaust hole communicated with the annular space is formed in the side wall of the lower limit guide pipe;
the upper main pipe passes through the limit hole on the measuring top cover and is inserted into the lower limit guide pipe, the upper main pipe is connected with the lower limit guide pipe through a sliding spline structure, the lower end of the upper main pipe is sealed,
the magnetic force floater is sleeved on the upper main pipe in an empty way,
the upper end of the outer pipe protrudes out of the upper surface of the soft soil foundation sand cushion and is in sealing connection with a sealing film on the soft soil foundation sand cushion, water seepage holes are arranged on the side wall of the outer pipe below the sealing film, geotextile is wrapped on the outer side of the outer pipe, a sealing top cover is connected with the upper end of the outer pipe,
the upper main pipe passes through the sealing top cover and is fixedly connected with the sealing top cover in a sealing way,
the measuring head of the steel ruler settlement gauge is arranged in the upper main pipe;
the magnetic force floater adopts a ring-shaped structure, round corners are arranged at the upper end and the lower end of the inner circle, the magnetic force floater is made of high-pressure rigid foam, and a high-strength magnetic block II is arranged in the magnetic force floater;
the closed bottom cover adopts an inverted cone structure.
2. A method for measuring groundwater level using the closed-mouth groundwater level measuring device according to claim 1, characterized in that the following steps are adopted:
first) the elevation H of the upper end of the upper main pipe is guided by a level gauge through a known elevation point during the first measurement S0 The distance L from the magnetic float to the upper end of the upper main pipe is measured by the steel ruler settlement gauge F The distance L from the measuring top cover to the upper end of the upper main pipe is measured through the steel ruler settlement gauge C0 The initial value of the groundwater level elevation is: h A0 ＝H S0 –L F ；
Secondly), after the foundation is solidified and subsided, the distance from the magnetic float to the upper end of the upper main pipe is measured by the steel ruler subsider, and the j-th measured value is L Fj The distance from the measuring top cover to the upper end of the upper main pipe is measured through the steel ruler settlement gauge, and the j-th measured value is L Cj Assume that the measured value (L C0 –L Cj ) For the lowering value of the upper end elevation of the upper main pipe in the jth measurement, the measured value H of the groundwater level elevation is A0,j ＝H S0 -(L C0 -L Cj )-L Fj ；
Wherein:
H A0,j j=1, 2,3, 4..n; h S0 The actual measurement initial value of the upper end elevation of the upper main pipe after the device is embedded; l (L) C0 Measuring an initial value of the distance from the top cover to the upper end of the upper main pipe after the device is embedded; l (L) Cj Measuring the distance from the top cover to the upper end of the upper main pipe for the jth measurement; l (L) Fj The distance between the magnetic float and the upper end of the upper main pipe is the j-th measurement; the length units measured and calculated during the implementation of the method are meters.
3. The method for measuring the groundwater level according to claim 2, wherein the groundwater level elevation measurement value H obtained in the second step is obtained by adopting the following formula A0,j And (3) correcting:
H Bi,j ＝H Ai,j +[H S0 +L C0 –(1+j/n i )H Si +(j/n i )H S(i+1) –L Ci,j ]
wherein:
H Bi,j is the correction value of the jth ground water level elevation measurement value after the ith retest upper end elevation of the upper main pipe, i=0, 1,2,3, 4..j=1, 2,3, 4..n;
H Ai,j the measurement value of the jth ground water level elevation after the ith retest upper end elevation of the upper main pipe is H when i=0 A0,j ；
H Si The upper end elevation actual measurement value of the upper main pipe in the ith repetition;
n i the total number of times of measuring the underground water level elevation in the interval time from the ith to the (i+1) th repeated measurement is the number of times of measuring the underground water level elevation in the interval time from the ith to the (i+1) th repeated measurement;
L Ci,j and (3) measuring the distance measurement value from the top cover to the upper end of the upper main pipe for the j-th measurement after the upper end elevation of the upper main pipe is retested for the i-th measurement.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201810642870.7A CN108871509B (en) | 2018-06-21 | 2018-06-21 | Device and method for measuring underground water level by closed method |
Applications Claiming Priority (1)
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