CN108842797B - Device for reinforcing open caisson bottom sealing and monitoring open caisson bottom sealing cracks and detection method - Google Patents

Device for reinforcing open caisson bottom sealing and monitoring open caisson bottom sealing cracks and detection method Download PDF

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CN108842797B
CN108842797B CN201810728541.4A CN201810728541A CN108842797B CN 108842797 B CN108842797 B CN 108842797B CN 201810728541 A CN201810728541 A CN 201810728541A CN 108842797 B CN108842797 B CN 108842797B
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rod
finite element
bottom sealing
elastic wave
open caisson
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CN108842797A (en
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金炜枫
王鑫
邓陈艳
其他发明人请求不公开姓名
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Zhejiang Lover Health Science and Technology Development Co Ltd
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    • E—FIXED CONSTRUCTIONS
    • E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
    • E02D—FOUNDATIONS; EXCAVATIONS; EMBANKMENTS; UNDERGROUND OR UNDERWATER STRUCTURES
    • E02D23/00—Caissons; Construction or placing of caissons
    • E—FIXED CONSTRUCTIONS
    • E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
    • E02D—FOUNDATIONS; EXCAVATIONS; EMBANKMENTS; UNDERGROUND OR UNDERWATER STRUCTURES
    • E02D33/00—Testing foundations or foundation structures
    • E—FIXED CONSTRUCTIONS
    • E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
    • E02D—FOUNDATIONS; EXCAVATIONS; EMBANKMENTS; UNDERGROUND OR UNDERWATER STRUCTURES
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    • E02D2600/10—Miscellaneous comprising sensor means

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Abstract

The invention discloses a device and a method for reinforcing a bottom sealing of an open caisson and monitoring cracks of the bottom sealing of the open caisson, wherein the device comprises a plurality of reinforcing frames and bottom sealing reinforcing layers; the reinforcing frame comprises a first rod and a second rod, the first rod is horizontally arranged, the second rod is vertically arranged, and one end of the first rod is fixedly connected with the middle part of the second rod; arranging a strain-measuring distributed optical fiber along the rod length direction of the first rod, thereby providing early warning when the underground water pressure causes the first rod material in the back cover reinforcing layer to be damaged; the crack monitoring device comprises a plurality of elastic wave receiving sheets and a data acquisition and analysis system, wherein the elastic wave receiving sheets are positioned on the side wall of the reinforcing frame. The invention has the advantages of overcoming the problem of difficult bottom sealing of the open caisson caused by overlarge pressure of the pressure-bearing water, preventing the relative displacement between the bottom sealing and the side wall of the open caisson, and overcoming the problem of difficult monitoring of crack and cracking of the bottom sealing after the bottom sealing.

Description

Device for reinforcing open caisson bottom sealing and monitoring open caisson bottom sealing cracks and detection method
Technical Field
The invention belongs to the field of geotechnical engineering research, and particularly relates to a device for reinforcing an open caisson bottom sealing and monitoring open caisson bottom sealing cracks.
Background
The open caisson foundation is a form of underground structure, and is characterized by that firstly, a well-cylindrical open caisson is made on the ground surface, then the soil is continuously dug in the open caisson to make the open caisson gradually sink to a specific elevation under the action of self-weight, then the bottom is sealed. The bottom sealing can prevent groundwater from flowing into the open caisson. When an open caisson foundation is adopted in an area with abundant underground water, in order to balance the influence of underground confined water, the concrete is generally poured by a guide pipe method for bottom sealing, but if the pressure of the confined water is too high, the bottom sealing is difficult, and meanwhile, the crack of the bottom sealing is difficult to monitor.
Disclosure of Invention
The invention provides a device for reinforcing bottom sealing of an open caisson and monitoring cracks of the bottom sealing of the open caisson, aiming at solving the problems that the bottom sealing of the open caisson is difficult due to overlarge pressure of pressure-bearing water, preventing the relative displacement between the bottom sealing and the side wall of the open caisson and solving the problems that cracks of the bottom sealing are difficult to monitor after the bottom sealing.
The technical scheme of the invention is as follows: a device for reinforcing an open caisson bottom sealing and monitoring open caisson bottom sealing cracks comprises a plurality of reinforcing frames and bottom sealing reinforcing layers; the reinforcing frame comprises a first rod and a second rod, the first rod is horizontally arranged, the second rod is vertically arranged, and one end of the first rod is fixedly connected with the middle part of the second rod; the bottom sealing reinforcing layer is positioned at the bottom of the open caisson; the second rod is positioned in the bottom sealing and reinforcing layer, the first rod is positioned below the side wall of the open caisson, one part of the first rod is positioned in the bottom sealing and reinforcing layer, the other part of the first rod is positioned in the soil layer, and the first rod can prevent the bottom sealing and reinforcing layer and the side wall of the open caisson from relative displacement.
Preferably, the bottom sealing and reinforcing layer is a concrete layer or a cement mixing layer.
Preferably, the distributed optical fiber for measuring the strain is arranged along the rod length direction of the first rod, the distributed optical fiber can monitor the strain of the first rod, and then the stress of the first rod is calculated through the strain, so that whether the stress of the first rod exceeds the strength allowable value of the first rod material or not is judged, and early warning is provided when the underground water pressure causes the first rod material in the back cover reinforcing layer to be damaged. Preferably, the distributed optical fiber is arranged on the lower surface of the first rod, and the distributed optical fiber is connected with the data acquisition and analysis system.
Preferably, the crack monitoring device comprises a plurality of elastic wave receiving sheets and a data acquisition and analysis system, wherein the elastic wave receiving sheets are positioned on the side wall of the reinforcing frame, and the data acquisition and analysis system is connected with the elastic wave receiving sheets.
Preferably, the reinforcing frame is provided with a first elastic wave receiving piece, a second elastic wave receiving piece and a third elastic wave receiving piece, the first elastic wave receiving piece and the third elastic wave receiving piece are arranged on the side wall of the second rod, and the second elastic wave receiving piece is arranged on the upper surface of the first rod.
Preferably, the elastic wave receiving sheet is made of a piezoelectric material, and the elastic wave receiving sheet made of the piezoelectric material can convert elastic waves into voltage signals, so that cracks can be monitored by receiving elastic waves generated after cracks crack.
A reinforcing and monitoring method of a device for reinforcing an open caisson bottom sealing and monitoring open caisson bottom sealing cracks comprises the following steps:
step 1: when the open caisson is sunk to a preset position, a bottom sealing reinforcing layer is manufactured at the bottom of the open caisson, and the bottom sealing reinforcing layer can be formed by pouring concrete or mixing cement and soil;
step 2: before the bottom sealing and reinforcing layer is solidified and hardened and has fluidity, the second rod in the reinforcing frame stands on the top surface of the bottom sealing and reinforcing layer, and the position of the first rod is described as follows: setting the fixed connection point of the first rod and the second rod as point A, setting the free end of the first rod as point B, and setting the vector connecting point A and point B
Figure GDA0002428210960000031
Pointing to the center of the open caisson; the second rod is then inserted into the bottom-sealing consolidated layer and then rotated 180 deg. so that the first rod is below the side wall of the open caisson and one part is in the bottom-sealing consolidated layer and the other part is in the soil layer, i.e. the vectors of points a and B
Figure GDA0002428210960000032
Pointing to the outer side of the open caisson;
step 3, after the bottom sealing reinforcing layer is coagulated and hardened, monitoring the strain (x) of the lower surface of the first rod in real time by distributed optical fibers arranged along the rod length direction of the first rod, adhering the distributed optical fibers to the lower surface of the first rod, connecting the distributed optical fibers with a data acquisition and analysis system, wherein x represents a coordinate along the rod length direction, x is more than or equal to 0 and less than or equal to L, L represents the length of the first rod, and the tensile stress sigma (x) of the first rod can be calculated as (x) × E by the strain (x) and the Young modulus E of the rod, when the first rod in the bottom sealing reinforcing layer is stressed due to the underground water pressure, the tensile strain of the lower surface of the first rod is maximum, so that the damage of the underground water pressure to the bottom sealing reinforcing layer can be warned based on whether the tensile stress sigma (x) exceeds a first rod material strength allowable value;
preferably, the method for monitoring the crack occurrence area in the back cover reinforcing layer by the crack monitoring device in the step 3 comprises the following 4 processes:
(1) the elastic wave receiving sheet receives elastic waves generated by crack cracking and transmits data to the data acquisition and analysis system;
(2) then the data acquisition and analysis system establishes a three-dimensional finite element model of the open caisson, the bottom sealing reinforcing layer and the reinforcing frame in the foundation, the established finite element grid has n nodes, a finite element overall mass matrix is set as [ M ], a finite element overall rigidity matrix is set as [ K ], an acceleration column vector on the finite element node is set as { a }, a displacement column vector on the finite element node is set as { u }, a load column vector on the finite element node is set as { f }, and a dynamic finite element equation is established as follows:
[M]{a}+[K]{u}＝{f}
each elastic wave receiving sheet is superposed with one finite element grid node, so that the actually measured time difference of the finite element nodes positioned on the elastic wave receiving sheet for receiving the elastic waves can be obtained from the actually measured data, m finite element nodes are set for receiving elastic wave signals, the moment of transmitting the elastic wave signals to the m finite element nodes can be obtained, and the actually measured time difference sequence { △ t) of the vibration signals received between every two nodes in the m finite element nodes can be obtained1,△t2,△t3,…,△tlTherein is here
Figure GDA0002428210960000041
(3) Then obtaining the time difference of the finite element nodes positioned on the elastic wave receiving sheet for receiving the simulated vibration signals: applying impact load to the ith finite element node, and simulating to obtain a time difference sequence of every two nodes of the m finite element nodes positioned on the elastic wave receiving sheet for receiving vibration signals
Figure GDA0002428210960000042
Here, the
Figure GDA0002428210960000043
The superscript i represents that the impact load is applied to the ith finite element node; i, taking the time from 1 to the total node number n to obtain n simulated time difference sequences:
Figure GDA0002428210960000044
Figure GDA0002428210960000051
(4) and finally obtaining a finite element node closest to the crack: recording an error function of
Figure GDA0002428210960000052
Here, the
Figure GDA0002428210960000053
The superscript i represents that the impact load is applied to the ith finite element node; i takes the sum of the numbers of the nodes from 1 to n to obtain a sequence { F) containing n error function values1,F2,…,FnSelecting { F }1,F2,…,FnAnd determining the position of the crack, and grouting at the crack position to block leakage caused by the crack.
The symbolic description in the above method is summarized as follows:
n: the total node number of the finite element grid;
[ M ]: a finite element overall mass matrix;
[K] the method comprises the following steps A finite element overall stiffness matrix;
{ a }: acceleration column vectors on finite element nodes;
{ u }: displacement column vectors on finite element nodes;
{ f }: load column vectors on finite element nodes.
m: the total node number of the finite elements contacted with the distributed optical fiber vibration sensor;
{△t1,△t2,△t3,…,△tl}: receiving an actually measured time difference sequence of vibration signals between every two nodes in the m finite element nodes;
l: the total combination number of any two node combinations in the m finite element nodes is
Figure GDA0002428210960000054
Figure GDA0002428210960000055
When the ith node is applied with a simulated impact load, simulating to obtain a time difference sequence of receiving vibration signals by every two nodes in m finite element nodes on the vibration sensor;
Fi: the superscript i indicates that an error function is obtained when the impact load is applied to the ith finite element node, having
Figure GDA0002428210960000061
Here, the
Figure GDA0002428210960000062
The invention has the advantages of overcoming the problem of difficult bottom sealing of the open caisson caused by overlarge pressure of the pressure-bearing water, preventing the relative displacement between the bottom sealing and the side wall of the open caisson, and overcoming the problem of difficult monitoring of crack and cracking of the bottom sealing after the bottom sealing.
Drawings
FIG. 1 is a schematic view of a reinforcement frame and a back cover reinforcement layer of the present invention;
FIG. 2 is a schematic view of the placement of the stiffener in the bottom sealing stiffener layer according to the present invention;
FIG. 3 is a top view of the open caisson of the present invention;
FIG. 4 is a schematic structural view of a reinforcing frame of the present invention;
in the figure, 1, a soil layer, 2, an open caisson, 3, a reinforcing frame, 4, a bottom sealing reinforcing layer, 5, a first elastic wave receiving sheet, 6, a distributed optical fiber, 7, a second elastic wave receiving sheet, 8, a third elastic wave receiving sheet, 9, a first rod, 10, a data acquisition and analysis system, 11, a second rod and 12 are slurry for balancing underground water pressure.
Detailed Description
In order to make the technical means, innovative features, objectives and effects of the present invention apparent, the present invention will be further described with reference to the following detailed drawings.
The device for reinforcing the bottom sealing of the open caisson and monitoring the cracks of the bottom sealing of the open caisson as shown in fig. 1-4 comprises a plurality of reinforcing frames 3 and bottom sealing reinforcing layers; the reinforcing frame 3 comprises a first rod 9 and a second rod 11, the first rod 9 is horizontally arranged, the second rod 11 is vertically arranged, and one end of the first rod 9 is fixedly connected with the middle part of the second rod 11; the bottom sealing reinforcing layer 4 is positioned at the bottom of the open caisson 2; the second rods 11 are positioned in the bottom sealing and strengthening layer 4, the first rods 9 are positioned below the side wall of the open caisson 2, one part of the first rods is positioned in the bottom sealing and strengthening layer 4, the other part of the first rods is positioned in the soil layer 1, and the first rods 9 can prevent the relative displacement of the bottom sealing and strengthening layer 4 and the side wall of the open caisson 2;
the bottom sealing and reinforcing layer 4 is a concrete layer or a cement mixing layer;
as shown in fig. 4, the distributed optical fiber 6 for measuring strain is arranged along the rod length direction of the first rod 9, and the distributed optical fiber 6 can monitor the strain of the first rod 9, and then calculate the stress of the first rod 9 according to the strain, so as to judge whether the stress of the first rod 9 exceeds the material strength allowable value of the first rod 9, and provide an early warning when the underground water pressure causes the material of the first rod 9 in the back cover reinforcing layer 4 to be damaged; the distributed optical fiber 6 is arranged on the lower surface of the first rod 9; the distributed optical fiber 6 is connected with a data acquisition and analysis system 10.
The crack monitoring device comprises a plurality of elastic wave receiving sheets and a data acquisition and analysis system 10, wherein the elastic wave receiving sheets are positioned on the side wall of a reinforcing frame 3, and the data acquisition and analysis system 10 is connected with the elastic wave receiving sheets; for example, as shown in fig. 4, the reinforcing frame is provided with a first elastic wave receiving sheet 5, a second elastic wave receiving sheet 7, and a third elastic wave receiving sheet 8, the first elastic wave receiving sheet 5 and the third elastic wave receiving sheet 8 being placed on the side wall of the second rod 11, and the second elastic wave receiving sheet 7 being placed on the upper surface of the first rod;
a reinforcing and monitoring method of a device for reinforcing an open caisson bottom sealing and monitoring open caisson bottom sealing cracks comprises the following steps:
step 1: when the open caisson 2 sinks to a preset position in the soil layer 1, a bottom sealing reinforcing layer 4 is manufactured at the bottom of the open caisson 2, and the bottom sealing reinforcing layer 4 can be formed by pouring concrete or mixing cement and soil; at this time, slurry 12 for balancing the pressure of the underground water exists in the open caisson 2 and above the bottom sealing reinforcing layer 4, and the slurry 12 for balancing the pressure of the underground water is used for balancing the pressure-bearing water below the bottom sealing reinforcing layer 4, so that the pressure-bearing water is prevented from cracking the bottom sealing reinforcing layer 4 upwards;
step 2: before the bottom sealing reinforcing layer 4 is set and hardened and has fluidity, the second rod 11 in the reinforcing frame 3 stands on the top surface of the bottom sealing reinforcing layer 4, and the position of the first rod 9 is described as follows: let the fixed connection point of the first rod 9 and the second rod 11 be point A, let the free end of the first rod 9 be point B, and let the vector connecting point A and point B
Figure GDA0002428210960000083
Pointing to the center of the open caisson 2; the second rod 11 is then inserted into the back reinforcement layer, this time as shown in fig. 2 a; the second rods 11 are then rotated 180 deg. so that the first rods 9 are located below the side walls of the open caisson 2 and one part is located in the bottom-sealing and reinforcing layer 4 and the other part is located in the soil layer 1, i.e. the vectors of points a and B
Figure GDA0002428210960000084
Pointing outside the open caisson 2, this time as shown in fig. 2 b;
step 3, after the bottom sealing reinforcing layer 4 is coagulated and hardened, monitoring the strain (x) of the lower surface of the first rod 9 in real time by the distributed optical fiber 6 arranged along the rod length direction of the first rod 9, wherein the distributed optical fiber 6 is adhered to the lower surface of the first rod 9, the distributed optical fiber 6 is connected with the data acquisition and analysis system 10, x represents a coordinate along the rod length direction of the first rod 9 and is more than or equal to 0 and less than or equal to L, L represents the length of the first rod 9, therefore, the strain (x) and the Young modulus E of the first rod 9 can calculate the tensile stress sigma (x) of the first rod 9 to be (x) × E, the strain of the distributed optical fiber 6 is measured in a mode that the fiber Brillouin frequency shift quantity is measured, the strain is calculated by the Brillouin frequency shift quantity, and the calculation formula
Figure GDA0002428210960000081
Where v isBRepresenting the Brillouin center frequency, vB(0) Indicating the brillouin center frequency to which the initial strain corresponds,
Figure GDA0002428210960000082
expressing the strain proportionality coefficient, (x) expressing the strain; when the underground water pressure causes the first rod 9 in the back cover strengthening layer 4 to be stressed, the tensile strain of the lower surface of the first rod 9 is the largest, so that the damage of the underground water pressure to the back cover strengthening layer 4 can be warned based on whether the tensile stress sigma (x) exceeds the material strength allowable value of the first rod 9; monitoring a crack generation area in the back cover reinforcing layer by using a crack monitoring device;
the method for monitoring the crack generation area in the back cover reinforcing layer by the crack monitoring device in the step 3 comprises the following 4 processes:
(1) the elastic wave receiving sheet receives elastic waves generated by crack cracking and transmits data to the data acquisition and analysis system 10;
(2) then, the data acquisition and analysis system 10 establishes a three-dimensional finite element model of the open caisson 2, the bottom sealing reinforcing layer 4 and the reinforcing frame 3 in the foundation, the established finite element grid has n nodes, a finite element overall quality matrix is set as [ M ], a finite element overall rigidity matrix is set as [ K ], an acceleration column vector on the finite element node is { a }, a displacement column vector on the finite element node is { u }, a load column vector on the finite element node is { f }, and a dynamic finite element equation is established as follows:
[M]{a}+[K]{u}＝{f}
each elastic wave receiving sheet is superposed with one finite element grid node, so that the actually measured time difference of the finite element nodes positioned on the elastic wave receiving sheet for receiving the elastic waves can be obtained from the actually measured data, m finite element nodes are set for receiving elastic wave signals, the moment of transmitting the elastic wave signals to the m finite element nodes can be obtained, and the actually measured time difference sequence { △ t) of the vibration signals received between every two nodes in the m finite element nodes can be obtained1,△t2,△t3,…,△tlTherein is here
Figure GDA0002428210960000091
(3) Then obtaining the time difference of the finite element nodes positioned on the elastic wave receiving sheet for receiving the simulated vibration signals: applying impact load to the ith finite element node, and simulating to obtain a time difference sequence of every two nodes of the m finite element nodes positioned on the elastic wave receiving sheet for receiving vibration signals
Figure GDA0002428210960000101
Here, the
Figure GDA0002428210960000102
The superscript i represents that the impact load is applied to the ith finite element node; i, taking the time from 1 to the total node number n to obtain n simulated time difference sequences:
Figure GDA0002428210960000103
(4) and finally obtaining a finite element node closest to the crack: recording an error function of
Figure GDA0002428210960000104
Here, the
Figure GDA0002428210960000105
The superscript i represents that the impact load is applied to the ith finite element node; i takes the sum of the numbers of the nodes from 1 to n to obtain a sequence { F) containing n error function values1,F2,…,FnSelecting { F }1,F2,…,FnAnd determining the position of the crack, and grouting at the crack position to block leakage caused by the crack.
The symbolic description in the above method is summarized as follows:
n: the total node number of the finite element grid;
[ M ]: a finite element overall mass matrix;
[K] the method comprises the following steps A finite element overall stiffness matrix;
{ a }: acceleration column vectors on finite element nodes;
{ u }: displacement column vectors on finite element nodes;
{ f }: load column vectors on finite element nodes.
m: the total node number of the finite elements contacted with the distributed optical fiber vibration sensor;
{△t1,△t2,△t3,…,△tl}: receiving an actually measured time difference sequence of vibration signals between every two nodes in the m finite element nodes;
l: the total combination number of any two node combinations in the m finite element nodes is
Figure GDA0002428210960000111
Figure GDA0002428210960000112
When the ith node is applied with a simulated impact load, simulating to obtain a time difference sequence of receiving vibration signals by every two nodes in m finite element nodes on the vibration sensor;
Fi: the superscript i indicates that an error function is obtained when the impact load is applied to the ith finite element node, having
Figure GDA0002428210960000113
Here, the
Figure GDA0002428210960000114

Claims (5)

1. The utility model provides a consolidate open caisson back cover and monitor open caisson back cover crackle's device which characterized in that: the reinforcing frame comprises a plurality of reinforcing frames and a bottom sealing reinforcing layer; the reinforcing frame comprises a first rod and a second rod, the first rod is horizontally arranged, the second rod is vertically arranged, and one end of the first rod is fixedly connected with the middle part of the second rod; the bottom sealing reinforcing layer is positioned at the bottom of the open caisson; the second rods are positioned in the bottom sealing and reinforcing layer, the first rods are positioned below the side wall of the open caisson, one part of the first rods are positioned in the bottom sealing and reinforcing layer, the other part of the first rods are positioned in the soil layer, and the first rods can prevent the bottom sealing and reinforcing layer and the side wall of the open caisson from relative displacement;
distributed optical fibers for measuring strain are arranged along the rod length direction of the first rod, the distributed optical fibers are arranged on the lower surface of the first rod, and the distributed optical fibers are connected with a data acquisition and analysis system;
the device also comprises a crack monitoring device, wherein the crack monitoring device comprises a plurality of elastic wave receiving sheets, and the elastic wave receiving sheets are positioned on the side wall of the reinforcing frame; the data acquisition and analysis system is connected with the elastic wave receiving sheet;
the reinforcing frame is provided with a first elastic wave receiving sheet, a second elastic wave receiving sheet and a third elastic wave receiving sheet, the first elastic wave receiving sheet and the third elastic wave receiving sheet are arranged on the side wall of the second rod, and the second elastic wave receiving sheet is arranged on the upper surface of the first rod.
2. The device for reinforcing the caisson bottoming and monitoring the caisson bottoming crack according to claim 1, wherein the device comprises: the bottom sealing reinforcing layer is a concrete layer or a cement soil stirring layer.
3. The device for reinforcing the open caisson bottom sealing and monitoring the open caisson bottom sealing cracks according to claim 1 is characterized in that: the elastic wave receiving sheet is made of piezoelectric materials.
4. A method for monitoring an apparatus for reinforcing a caisson sealing bottom and monitoring a caisson sealing bottom crack according to any one of claims 1 to 3, wherein the method comprises the following steps: which comprises the following steps:
step 1: when the open caisson is sunk to a preset position, a bottom sealing reinforcing layer is manufactured at the bottom of the open caisson, and the bottom sealing reinforcing layer is formed by pouring concrete or mixing cement and soil;
step 2: before the bottom sealing and reinforcing layer is solidified and hardened and has fluidity, the second rod in the reinforcing frame stands on the top surface of the bottom sealing and reinforcing layer, and the position of the first rod is described as follows: fixed connection of the first rod and the second rodPoint A, point B and the vector connecting the points A and B
Figure FDA0002519841280000021
Pointing to the center of the open caisson; the second rod is then inserted into the bottom-sealing consolidated layer and then rotated 180 deg. so that the first rod is below the side wall of the open caisson and one part is in the bottom-sealing consolidated layer and the other part is in the soil layer, i.e. the vectors of points a and B
Figure FDA0002519841280000022
Pointing to the outer side of the open caisson;
and 3, after the sealing bottom reinforcing layer is solidified and hardened, monitoring the strain (x) of the lower surface of the first rod in real time by using a distributed optical fiber arranged along the rod length direction of the first rod, wherein the x represents a coordinate along the rod length direction, is not less than 0 and not more than L, and is not more than L, wherein the length of the first rod is represented by L, the tensile stress sigma (x) of the first rod is calculated to be (x) × E according to the strain (x) and the Young modulus E of the rod, and when the first rod in the sealing bottom reinforcing layer is stressed due to the underground water pressure, the tensile strain of the lower surface of the first rod is the maximum, so that whether the underground water pressure damages the sealing bottom reinforcing layer or not is warned based on whether the tensile stress sigma (x) exceeds the allowable value of the material strength of the first rod, and a crack monitoring device monitors the crack generation area in.
5. The monitoring method of the device for reinforcing the caisson bottoming and monitoring the caisson bottoming crack according to claim 4, wherein the device comprises: the method for monitoring the crack generation area in the back cover reinforcing layer by the crack monitoring device in the step 3 comprises the following 4 processes:
(1) the elastic wave receiving sheet receives elastic waves generated by crack cracking and transmits data to the data acquisition and analysis system;
(2) then the data acquisition and analysis system establishes a three-dimensional finite element model of the open caisson, the bottom sealing reinforcing layer and the reinforcing frame in the foundation, the established finite element grid has n nodes, a finite element overall mass matrix is set as [ M ], a finite element overall rigidity matrix is set as [ K ], an acceleration column vector on the finite element node is set as { a }, a displacement column vector on the finite element node is set as { u }, a load column vector on the finite element node is set as { f }, and a dynamic finite element equation is established as follows:
[M]{a}+[K]{u}＝{f}
each elastic wave receiving sheet is superposed with one finite element grid node, thus the actually measured time difference of the finite element nodes positioned on the elastic wave receiving sheet for receiving the elastic wave is obtained from the actually measured data, a total of m finite element nodes are set for receiving elastic wave signals, the moment of transmitting the elastic wave signals to the m finite element nodes is obtained at the moment, and thus the actually measured time difference sequence { delta t) of receiving vibration signals between every two nodes in the m finite element nodes can be obtained1,Δt2,Δt3,…,ΔtlTherein is here
Figure FDA0002519841280000031
(3) Then obtaining the time difference of the finite element nodes positioned on the elastic wave receiving sheet for receiving the simulated vibration signals: applying impact load to the ith finite element node, and simulating to obtain a time difference sequence of every two nodes of the m finite element nodes positioned on the elastic wave receiving sheet for receiving vibration signals
Figure FDA0002519841280000032
Here, the
Figure FDA0002519841280000033
The superscript i represents that the impact load is applied to the ith finite element node; i, taking the time from 1 to the total node number n to obtain n simulated time difference sequences:
Figure FDA0002519841280000034
Figure FDA0002519841280000035
…
Figure FDA0002519841280000041
…
Figure FDA0002519841280000042
(4) and finally obtaining a finite element node closest to the crack: recording an error function of
Figure FDA0002519841280000043
Here, the
Figure FDA0002519841280000044
The superscript i represents that the impact load is applied to the ith finite element node; i takes the sum of the numbers of the nodes from 1 to n to obtain a sequence { F) containing n error function values1,F2,…,FnSelecting { F }1,F2,…,FnDetermining a cracking position, and then plugging leakage caused by the crack by grouting at the cracking position;
the symbolic description in the above method is summarized as follows:
n: the total node number of the finite element grid;
[ M ]: a finite element overall mass matrix;
[K] the method comprises the following steps A finite element overall stiffness matrix;
{ a }: acceleration column vectors on finite element nodes;
{ u }: displacement column vectors on finite element nodes;
{ f }: load column vectors on finite element nodes;
m: the total node number of the finite elements contacted with the distributed optical fiber vibration sensor;
{Δt1,Δt2,Δt3,…,Δtl}: receiving an actually measured time difference sequence of vibration signals between every two nodes in the m finite element nodes;
l: the total combination number of any two node combinations in the m finite element nodes is
Figure FDA0002519841280000045
Figure FDA0002519841280000051
When the ith node is applied with a simulated impact load, simulating to obtain a time difference sequence of receiving vibration signals by every two nodes in m finite element nodes on the vibration sensor;
Fi: the superscript i indicates that an error function is obtained when the impact load is applied to the ith finite element node, having
Figure FDA0002519841280000052
Here, the
Figure FDA0002519841280000053
CN201810728541.4A 2018-07-05 2018-07-05 Device for reinforcing open caisson bottom sealing and monitoring open caisson bottom sealing cracks and detection method Active CN108842797B (en)

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