CN108978696A - A kind of bottom sealing antiseepage and displacement monitor - Google Patents

Abstract

The invention discloses a kind of bottom sealing antiseepage and displacement monitors, including water proof thin plate, displacement monitor；The displacement monitor includes sequentially connected first bar, first pressure sensor, distribution type fiber-optic, second pressure sensor and the second bar, the water proof thin plate is horizontal positioned, the distribution type fiber-optic is placed horizontally in water proof thin plate upper surface, first bar and the second bar are placed vertically, and the distribution type fiber-optic can monitor the strain of water proof thin plate upper surface.It the beneficial effects of the invention are as follows the problem of artesian water causes bottom sealing to leak is slowed down, in addition can monitor whether bottom sealing has leakage, while monitor in bottom sealing the displacement of water proof thin plate and stress to artesian pressure excessive below early warning bottom sealing.

Description

A caisson bottom sealing anti-seepage and displacement monitoring device

technical field

The invention belongs to the field of geotechnical engineering research, in particular to a caisson bottom sealing anti-seepage and displacement monitoring device.

Background technique

The caisson foundation is a form of underground structure, which is characterized by first making a shaft-shaped caisson on the surface, and then continuously digging in the well to make the caisson gradually sink to the specified elevation under the action of its own weight, and then seal the bottom. The back cover prevents groundwater from flowing into the caisson. When caisson foundations are used in areas with abundant groundwater, in order to balance the influence of underground confined water, concrete is usually poured by the conduit method for bottom sealing. Deformation and cracking.

Contents of the invention

In order to alleviate the problem of leakage and cracking of caisson bottom seal caused by pressurized water, and to detect the displacement and stress of caisson bottom seal so as to warn of excessive pressurized water pressure, the present invention provides a caisson bottom seal anti-seepage and displacement monitoring device.

The technical scheme of the present invention: a caisson bottom sealing anti-seepage and displacement monitoring device, including a water-proof sheet and a displacement monitoring device; the displacement monitoring device includes a data acquisition and analysis system, an optical fiber demodulator, and a first rod connected in sequence, The first pressure sensor, the distributed optical fiber, the second pressure sensor and the second rod, the data acquisition and analysis system, the optical fiber demodulator and the distributed optical fiber are connected in sequence, and the data acquisition and analysis system is connected with the first pressure sensor and the second pressure sensor respectively. Two pressure sensors are connected, the water-proof thin plate is placed horizontally, the distributed optical fiber is placed horizontally on the surface of the water-proof thin plate, and the first rod and the second rod are vertically placed. The distributed optical fiber can monitor the strain on the upper surface of the waterproof sheet.

Preferably, the water-proof thin plate is circular, the optical fiber passes through the center of the water-proof thin plate, and the midpoint of the optical fiber coincides with the center of the water-proof thin plate.

Preferably, the first pressure sensor and the first pressure sensor are made of piezoelectric ceramics.

Preferably, the caisson bottom seal anti-seepage and displacement monitoring device is equipped with a DC power supply and an ammeter, and the positive pole access point and the negative pole access point for measuring resistance are set on the edge of the water-proof sheet, and the positive pole access point and the positive pole of the DC power supply Connection, the negative pole of the DC power supply, the ammeter and the negative pole access point are connected in sequence, and the resistance R is calculated by the voltage U of the DC power supply and the current I measured by the ammeter, and there is By monitoring the change of resistance R, it is judged whether there is leakage in the caisson bottom cover, for example, a sudden decrease in resistance R indicates that there is leakage.

An anti-seepage and displacement monitoring method of a caisson bottom sealing anti-seepage and displacement monitoring device, comprising the following steps:

Step 1: The cross-section of the caisson is circular, and the water-proof sheet is circular; there is a bottom reinforcement layer at the lower end of the caisson. The bottom reinforcement layer can be poured with concrete or mixed with cement and soil. The bottom reinforcement layer has resistance The water pressure at the bottom of the caisson and the anti-seepage effect. A water-proof thin plate is placed horizontally in the bottom reinforcement layer. The water-proof thin plate can enhance the anti-seepage ability of the bottom of the caisson. The first pressure sensor and the second pressure sensor are respectively located at two ends of the distributed optical fiber. One end of the first rod is connected to the first pressure sensor and the other end is connected to the bottom of the caisson, one end of the second rod is connected to the second pressure sensor and the other end is connected to the bottom of the caisson. Pressurized water infiltrates along the cracks in the reinforcement layer of the back cover;

Step 2: Displacement monitoring: first measure the compression of the first rod and the second rod, set the length of the first rod as L ₁ , the length of the second rod as L ₂ , set the Young’s modulus of the first rod as E ₁ , and set The Young's modulus of the second rod is E ₂ , let the stress measured by the first pressure sensor be σ ₁ , let the stress measured by the second pressure sensor be σ ₂ , let the compression of the first rod be Δs ₁ , let the first The compression amount of the second rod is Δs ₂ , then the compression amount of the first rod is The compression of the second rod is Then measure the relative vertical displacement w ₁ of the midpoint of the distributed optical fiber relative to the first pressure sensor, measure the relative vertical displacement w ₂ of the midpoint of the distributed optical fiber relative to the second pressure sensor, then the average of the midpoint of the distributed optical fiber relative to its two ends The relative vertical displacement is w _o =(w ₁ +w ₂ )/2, and finally the absolute vertical displacement of the center of the waterproof sheet is calculated as w=w _o +(Δs ₁ +Δs ₂ )/2;

Step 3: Check whether the stress of the waterproof sheet exceeds the strength of the waterproof sheet: set the radius of the circular waterproof sheet as R, set the thickness of the circular waterproof sheet as h, and set the Young's modulus of the circular waterproof sheet is E, set the Poisson's ratio of the circular water-proof thin plate as v, take the displacement at the center of the circular water-proof thin plate as the measured average relative displacement w _o between the middle point of the distributed optical fiber and the two ends of the distributed optical fiber, and then set The maximum stress in the water thin plate is σ _max and the calculation formula is Assuming the strength of the waterproof sheet is [σ], when σ _max ≥ [σ], it indicates that the stress in the waterproof sheet exceeds its own strength, that is, the underground confined water causes the deformation of the bottom reinforcement layer and the waterproof sheet to be too large and the water-resistant sheet The thin plate has been damaged, which can provide an early warning for the excessive pressure of the confined water on the bottom seal of the caisson;

Step 4: Check whether there is leakage on the bottom cover of the caisson: set the positive and negative access points for resistance measurement on the edge of the water barrier sheet, connect the positive access point to the positive pole of the DC power supply, connect the negative pole of the DC power supply, the ammeter and The negative access points are connected in sequence, and the resistance R is calculated by the voltage U of the DC power supply and the current I measured by the ammeter, and there is By monitoring the change of resistance R, it is judged whether there is leakage in the caisson bottom cover, for example, a sudden decrease in resistance R indicates that there is leakage.

Preferably, the method of measuring the relative vertical displacement w1 in the step ₂ is: firstly divide the midpoint of the distributed optical fiber to the end point of the optical fiber where the first pressure sensor is located on average into n segments, and each segment in the distributed optical fiber The length is Δl, when the radius of the circular waterproof thin plate is R, there is Δl=R/n, the end point of the optical fiber at which the first pressure sensor is located is node 1, and the node corresponding to the middle point of the distributed optical fiber is n+1, The nodes in the direction from node 1 to node n+1 are sequentially recorded as 1, 2, 3, Λ, n, n+1, and the strain measured at the i-th node of the distributed optical fiber is assumed to be ε _i , then the midpoint of the distributed optical fiber _The formula for calculating the relative vertical displacement w1 relative to the end point of the optical fiber where the first pressure sensor is located is The calculation process of the relative vertical displacement w ₂ of the middle point of the distributed optical fiber relative to the end point of the optical fiber where the second pressure sensor is located is the same as the calculation process of w ₁ .

The invention has the beneficial effects of alleviating the leakage of the bottom seal of the caisson caused by pressurized water, in addition, it can monitor whether there is leakage in the bottom seal of the caisson, and at the same time monitor the displacement and stress of the water-blocking thin plate in the bottom seal of the caisson, so as to give an early warning of the leakage under the bottom seal of the caisson Confined water pressure is too high.

Description of drawings

Fig. 1 is the schematic diagram of water-repelling thin plate, bottom sealing reinforcement layer and caisson of the present invention;

Fig. 2 is a schematic diagram of a longitudinal section of a water-proof thin plate of the present invention;

Fig. 3 is a top view of the waterproof sheet of the present invention.

Fig. 4 is a schematic diagram of the connection between the data acquisition and analysis system of the present invention, the distributed optical fiber and the pressure sensor.

In the figure 1. foundation soil layer, 2. caisson, 3. water-proof thin plate, 4. back cover reinforcement layer, 5. distributed optical fiber, 6. first rod, 7. second rod, 8. first pressure sensor, 9. Second pressure sensor, 10. DC power supply, 11. Ammeter, 12. Positive access point, 13. Negative access point, 14. Optical fiber demodulator, 15. Data acquisition and analysis system.

Detailed ways

In order to make the technical means, innovative features, goals and effects achieved by the present invention easy to understand, the present invention will be further described below in conjunction with specific illustrations.

As shown in Fig. 1-Fig. 3, a kind of caisson bottom seal anti-seepage and displacement monitoring device comprises water-proof thin plate 3 and displacement monitoring device; The first rod 6, the first pressure sensor 8, the distributed optical fiber 5, the second pressure sensor 9 and the second rod 7, the data acquisition and analysis system 15, the optical fiber demodulator 14 and the distributed optical fiber 5 are connected in sequence, and the The data acquisition and analysis system 15 is respectively connected with the first pressure sensor 8 and the second pressure sensor 9, the water-proof thin plate 3 is placed horizontally, the distributed optical fiber 5 is horizontally placed on the upper surface of the water-proof thin plate 3, and the first rod 6 and the second rod 7 are placed vertically; the distributed optical fiber 5 can monitor the strain on the upper surface of the water-proof sheet 3;

The water-proof thin plate 3 is circular, the distributed optical fiber 5 passes through the center of the water-proof thin plate 3, and the midpoint of the distributed optical fiber 5 coincides with the center of the water-proof thin plate 3;

The caisson back cover anti-seepage and displacement monitoring device is equipped with a DC power supply 10 and an ammeter 11, and the positive pole access point 12 and the negative pole access point 13 for measuring resistance are set on the edge of the water-proof sheet 3, and the positive pole access point 12 and the DC The positive pole of the power supply 10 is connected, the negative pole of the DC power supply 10, the ammeter 11 and the negative pole access point 13 are connected in sequence, and the resistance R is calculated by the voltage U of the DC power supply 10 and the current I measured by the ammeter, and there is By monitoring the change of resistance R, it is judged whether there is leakage in the caisson bottom cover, for example, a sudden decrease in resistance R indicates that there is leakage.

An anti-seepage and displacement monitoring method of a caisson bottom sealing anti-seepage and displacement monitoring device, comprising the following steps:

Step 1: There is a caisson 2 in the foundation soil layer 1, the cross section of the caisson 2 is circular, and the water-proof sheet 3 is circular; the lower end of the caisson 2 has a bottom reinforcement layer 4, and the bottom reinforcement layer 4 can be used for concrete pouring. It is formed or mixed with cement and soil. The bottom reinforcement layer 4 has the function of resisting the water pressure at the bottom of the caisson 2 and preventing seepage. In the bottom reinforcement layer 4, a water-proof sheet 3 is placed horizontally, and the water-proof sheet 3 strengthens the caisson 2. The anti-seepage ability of the back cover, the first pressure sensor 8 and the second pressure sensor 9 are respectively located on the upper part of the two ends of the distributed optical fiber 5, one end of the first rod 6 is connected with the first pressure sensor 8 and the other end is connected with the bottom of the caisson 2, One end of the second rod 6 is connected to the second pressure sensor 9 and the other end is connected to the bottom of the caisson 2, and the water-proof thin plate 3 can prevent underground pressurized water from infiltrating along the cracks of the bottom-sealing reinforcement layer 4;

Step 2: Displacement monitoring: first measure the compression of the first rod 6 and the second rod 7, set the length of the first rod 6 as L ₁ , set the length of the second rod 7 as L ₂ , and set the Young’s modulus of the first rod 6 is E ₁ , let the Young's modulus of the second rod 7 be E ₂ , let the stress measured by the first pressure sensor 8 be σ ₁ , let the stress measured by the second pressure sensor 9 be σ ₂ , let the first rod 6 The compression amount of the rod 7 is Δs ₁ , and the compression amount of the second rod 7 is Δs ₂ , then the compression amount of the first rod 6 is The compression amount of the second rod 7 is Then measure the relative vertical displacement w ₁ of the midpoint of the distributed optical fiber 5 relative to the first pressure sensor 8, measure the relative vertical displacement w ₂ of the midpoint of the distributed optical fiber 5 relative to the second pressure sensor 9, then the midpoint of the distributed optical fiber 5 The average relative vertical displacement relative to its two ends is w _o =(w ₁ +w ₂ )/2, and finally the absolute vertical displacement of the center of the waterproof sheet 3 is calculated as w=w _o +(Δs ₁ +Δs ₂ )/2 ;

Step 3: Check whether the stress of the waterproof sheet 3 exceeds the strength of the waterproof sheet 3: set the radius of the circular waterproof sheet 3 as R, let the thickness of the circular waterproof sheet 3 be h, and set the circular waterproof sheet 3 The Young's modulus is E, and the Poisson's ratio of the circular water-proof thin plate 3 is set to be v, and the displacement at the center of the circle water-proof thin plate 3 is taken as the distance between the measured distributed optical fiber 5 midpoint relative to the distributed optical fiber 5 two ends The average relative vertical displacement w _o , then set the maximum stress in the waterproof sheet 3 as σ _max and the calculation formula is Assume that the strength of the waterproof sheet 3 is [σ]. When σ _max ≥ [σ], it indicates that the stress in the waterproof sheet 3 exceeds its own strength, that is, the underground confined water causes the bottom reinforcement layer 4 and the waterproof sheet 3 to deform too much. Large and the water-repellent sheet 3 has been damaged, which can provide an early warning for the pressure of the confined water on the bottom seal of the caisson 2;

Step 4: check whether there is leakage on the back cover of the caisson 2: set the positive pole access point 12 and the negative pole access point 13 for resistance measurement on the edge of the water-proof sheet 3, and connect the positive pole access point 12 to the positive pole of the DC power supply 10, and the DC power supply The negative pole of 10, the ammeter 11 and the negative pole access point 13 are connected in sequence, and the resistance R is calculated by the voltage U of the DC power supply 10 and the current I measured by the ammeter 11, and there is Whether there is leakage from the bottom cover of the caisson 2 is judged by monitoring the change of the resistance R, for example, a sudden decrease in the resistance R indicates that there is leakage.

The method of measuring the relative vertical displacement w1 in the step ₂ is as follows: firstly divide the midpoint of the distributed optical fiber 5 to the end point of the optical fiber 5 where the first pressure sensor 8 is located, and divide it into n segments on average, and each segment in the distributed optical fiber 5 The length is Δl, when the radius of the circular water-proof thin plate 3 is R, there is Δl=R/n, note the end point of the optical fiber 5 where the first pressure sensor 8 is located as node 1, and record the node corresponding to the middle point of the distributed optical fiber 5 is n+1, the nodes in the direction from node 1 to node n+1 are sequentially recorded as 1, 2, 3, Λ, n, n+1, and the strain measured at the i-th node of the distributed optical fiber 5 is ε _i , Then the formula for calculating the relative vertical displacement w1 _of the midpoint of the distributed optical fiber 5 relative to the end point of the optical fiber 5 where the first pressure sensor 8 is located is The calculation process of the relative vertical displacement w ₂ of the middle point of the distributed optical fiber 5 relative to the end point of the optical fiber 5 where the second pressure sensor 9 is located is the same as the calculation process of w ₁ .

Claims (6)

1. a kind of bottom sealing antiseepage and displacement monitor, it is characterised in that: it includes water proof thin plate, displacement monitor； The displacement monitor includes data acquisition and analysis system, optical fibre interrogation instrument and sequentially connected first bar, first pressure Sensor, distribution type fiber-optic, second pressure sensor and the second bar, the data acquisition and analysis system, optical fibre interrogation instrument and point Cloth optical fiber is sequentially connected, and the data acquisition and analysis system connects with first pressure sensor and second pressure sensor respectively It connects, the water proof thin plate is horizontal positioned, and the distribution type fiber-optic is placed horizontally in water proof thin plate upper surface, first bar and second Bar is placed vertically.

2. a kind of bottom sealing antiseepage according to claim 1 and displacement monitor, it is characterised in that: the water proof is thin Plate is circle, and the optical fiber passes through the center of circle of water proof thin plate, and optical fiber midpoint and the water proof thin plate center of circle are overlapped.

3. a kind of bottom sealing antiseepage according to claim 1 and displacement monitor, it is characterised in that: first pressure Force snesor and first pressure sensor are made of piezoelectric ceramics.

4. a kind of bottom sealing antiseepage according to claim 1 and displacement monitor, it is characterised in that: the open caisson envelope Bottom antiseepage and displacement monitor are furnished with DC power supply and galvanometer, and the anode access of measurement resistance is arranged in water proof sheet edges The anode connection of point and cathode access point, positive access point and DC power supply, cathode, galvanometer and the cathode access of DC power supply Point is sequentially connected.

5. a kind of bottom sealing antiseepage and the antiseepage of displacement monitor described in -4 and displacement monitoring side according to claim 1 Method, it is characterised in that: it includes the following steps:

Step 1: the cross section of open caisson is circle, and water proof thin plate is circle；There is back cover reinforcing layer in open caisson lower end, and back cover reinforcing layer can Think that concreting is formed or stirred for cement and soil, level lays water proof thin plate in back cover reinforcing layer, the One pressure sensor and second pressure sensor are located at the top at distribution type fiber-optic both ends, one end of the first bar and the first pressure Force snesor connection and the other end is connect with open caisson bottom, one end of the second bar connect with second pressure sensor and the other end and The connection of open caisson bottom；

Step 2: displacement monitoring: measuring the decrement of the first bar and the second bar first, if the first pole length is L₁If the second bar is long Degree is L₂If the first bar Young's modulus is E₁If the second bar Young's modulus is E₂If the stress that first pressure sensor measures is σ₁If the stress that second pressure sensor measures is σ₂If the decrement of the first bar is Δ s₁If the decrement of the second bar is Δ s₂, then the decrement of the first bar isThe decrement of second bar isThen distribution type fiber-optic is measured Relative vertical displacement w of the midpoint with respect to first pressure sensor₁, distribution type fiber-optic midpoint is measured with respect to second pressure sensor Relative vertical displacement w₂, then distribution type fiber-optic midpoint is w with respect to the average relative vertical displacement at itself both ends_o=(w₁+w₂)/2, The absolute vertical displacement for finally calculating water proof thin plate center is w=w_o+(Δs₁+Δs₂)/2；

Step 3: whether the stress for examining water proof thin plate is more than water proof thin plate intensity: the radius of round water proof thin plate is set as R, if circle The plate thickness of shape water proof thin plate is h, if the Young's modulus of round water proof thin plate is E, if the Poisson's ratio of round water proof thin plate is v, is taken The displacement of round water proof thin plate the center point is the average phase at the distribution type fiber-optic midpoint Relative distribution formula optical fiber both ends that measurement obtains To displacement w_o, set the maximum stress in water proof thin plate then as σ_maxAnd calculation formula isIf water proof is thin The intensity of plate is [σ], works as σ_maxShow that the stress in water proof thin plate has been more than self-strength when >=[σ], i.e. underground bearing water causes Back cover reinforcing layer and water proof thin plate deform excessive and water proof thin plate destroyed, can be in this way artesian water to bottom sealing pressure mistake It is big that early warning is provided；

Step 4: examining whether bottom sealing has leakage: in the positive access point and cathode of the setting resistance measurement of water proof sheet edges The anode connection of access point, positive access point and DC power supply, cathode, galvanometer and the cathode access point of DC power supply successively connect It connects, resistance R is calculated by the electric current I that the voltage U and galvanometer of DC power supply are measured, is hadPass through the change of monitoring resistor R Change to judge whether bottom sealing has a leakage, such as resistance R reduces show to have leakage suddenly.

6. a kind of bottom sealing antiseepage according to claim 5 and the antiseepage of displacement monitor and displacement monitoring method, It is characterized by: measuring relative vertical displacement w in the step 2₁Mode are as follows: first by distribution type fiber-optic midpoint to first pressure Optical fiber endpoint where force snesor is equally divided into n sections, and the length of each segmentation is Δ l in distribution type fiber-optic, when round water proof When the radius of thin plate is R, there is Δ l=R/n, the optical fiber endpoint where remembering first pressure sensor is node 1, remembers distribution type fiber-optic The corresponding node in midpoint is n+1,1,2,3, Λ, n, n+1 is successively denoted as from node 1 toward the node that node is the direction n+1, if distribution The strain that the i-th node measurement of formula optical fiber obtains is ε_i, then distribution type fiber-optic midpoint is with respect to the optical fiber where first pressure sensor The relative vertical displacement w of endpoint₁Calculation formula beDistribution type fiber-optic midpoint is with respect to second pressure sensor The relative vertical displacement w of place optical fiber endpoint₂Calculating process and w₁Calculating process it is identical.