A method for monitoring riverbed settlement during tunnel construction under a river

Abstract

The present invention discloses a method for monitoring riverbed settlement during tunnel underpass river construction, comprising the following steps: burying a water level detection device on the riverbed directly above the tunnel as a monitoring point, burying a water level detection device on the riverbed outside the construction influence range of the upstream and / or downstream of the monitoring point as a reference point; the water level detection device comprises a water level gauge and a communication module, the water level gauge monitors the water level depth of the water level detection device in real time, and the communication module reads and transmits water level data to the outside at a fixed time; calculating the water level height difference between the monitoring point and the reference point at the same detection time, comparing the later water level height difference with the initial water level height difference to obtain the deformation of the monitoring point, and judging whether the monitoring point has settled or bulged. The monitoring method of the present invention has the advantages of high precision, high stability and high reliability, can effectively reduce the monitoring cost and can provide a scientific and positive reference basis for construction.

Description

[Technical field]

[0001] The invention relates to engineering monitoring, and in particular to a method for monitoring riverbed settlement during construction of a tunnel under a river. [Background Technology]

[0002] The tunneling process of urban rail transit shield tunnels often causes disturbances to the surrounding soil. In order to timely obtain the deformation of the ground and soil during the shield tunneling process, the actual construction process generally adopts the method of ground manual observation, that is, the use of total stations and levels to monitor deformation. However, when the shield tunnel passes under the river, traditional monitoring methods cannot be directly implemented. The general practice is to use underwater scanning of the terrain, and then superimpose and analyze the terrain data obtained by multiple scans to achieve part of the purpose of monitoring the settlement.

[0003] Currently, due to technical and cost reasons, there is no effective monitoring method for engineering tunnels passing under rivers, lakes and reservoirs. The industry mainly conducts water surface inspections (observing whether bubbles are generated, etc.). The inspection method is relatively primitive and cannot quantitatively analyze the amount of riverbed subsidence caused by engineering tunnels.

[0004] Some high-risk projects where tunnels pass under rivers, lakes or other places use unmanned boats to conduct underwater topographic mapping and compare the topographic data obtained multiple times. However, this is expensive, and its accuracy and frequency are far from meeting the requirements of high-frequency real-time settlement monitoring. [Summary of the invention]

[0005] The technical problem to be solved by the present invention is to provide a method for monitoring riverbed settlement during construction of a tunnel under a river with high accuracy and low cost.

[0006] In order to solve the above technical problems, the technical solution adopted by the present invention is a method for monitoring riverbed settlement during underwater tunnel construction, comprising the following steps:

[0007] 101) A water level detection device is buried on the riverbed directly above the tunnel as a monitoring point, and at least one water level detection device is buried on the riverbed outside the construction influence range upstream and / or downstream of the monitoring point as a reference point;

[0008] 102) The water level detection device includes a water level meter and a communication module. The water level meter monitors the water level depth of the water level detection device in real time, and the communication module reads and transmits water level data to the outside at regular intervals;

[0009] 103) Calculate the water level difference between the monitoring point and the reference point at the same detection time, compare the later water level difference with the initial water level difference to obtain the deformation of the monitoring point, and determine whether the monitoring point has settled or bulged.

[0010] In the monitoring method described above, the water level detection device includes a prefabricated concrete part serving as a counterweight block, the bottom of the prefabricated concrete part includes a plurality of steel bars extending downwardly serving as a metal bracket inserted into the riverbed to fix the water level detection device; the top of the prefabricated concrete part includes a metal bracket for binding and fixing the water level gauge, and the metal bracket is connected to a steel cable for point deployment and recovery of the water level detection device.

[0011] In the monitoring method described above, the communication module of the water level detection device is connected to the corresponding data acquisition terminal on the shore through a communication cable, and the data acquisition terminal is wirelessly connected to the control center to send data to the control center; the communication cable is tied together with the steel cable, tied with a cable tie at set intervals, and tied with heavy blocks, and sunk to the bottom of the water.

[0012] In the monitoring method described above, a water level detection device is buried on the riverbed upstream and downstream of the monitoring point as a reference point; the deformation h of the monitoring point is: h=((△h1-△h01)+(△h2-△h02)) / 2; wherein △h1 is the later water level difference between the monitoring point and the first reference point, △h01 is the initial water level difference between the monitoring point and the first reference point; △h2 is the later water level difference between the monitoring point and the second reference point, and △h02 is the initial water level difference between the monitoring point and the second reference point.

[0013] In the monitoring method described above, in step 101, a plurality of monitoring points are arranged along the tunnel direction at set intervals, a water level detection device is buried on the riverbed outside the construction influence range upstream and / or downstream of the monitoring point as a reference point, and a hydrological flowmeter is arranged between the reference point and the monitoring point.

[0014] According to the monitoring method described above, the cumulative settlement of a monitoring point a is obtained by the following formula:

[0015] ΔH a =(H a -H 基 )-H a0

[0016] Where ΔH a : water level change at monitoring point a, i.e., the settlement at monitoring point a; H a0 : initial water level difference at monitoring point a; H 基 : The water level value of the reference point after synchronizing the reference point time with the monitoring point time by considering the flow velocity; H a : Water level value at monitoring point a.

[0017] In the monitoring method described above, the water level value H of the reference point after the reference point time is synchronized with the monitoring point time 基 Obtained by the following formula:

[0018] H 基 =H 基1+(H 基2 -H 基1 )*(t 基 -t 基1 ) / (t 基2 -t 基1 )

[0019] Among them, H 基1 : The instantaneous water level value of the benchmark point when the same measuring section starts collecting data; H 基2 : The instantaneous water level value of the reference point when data collection ends in the same measuring section; t 基 : Time base of the reference point; t 基1 : The time when the data collection starts at the benchmark point of the same measuring section; t 基2 : The time when data collection for the benchmark point in the same measuring section ends.

[0020] The monitoring method described above, the water level value H at monitoring point a a Obtained by the following formula:

[0021] H a =H a1 +(H a2 -H a1 )*(tt a1 ) / (t a2 -t a1 )

[0022] Among them, H a1 : The instantaneous water level value at monitoring point a when data collection starts in the same measuring section; H a2 : The instantaneous water level value of monitoring point a at the end of data collection in the same measuring section; t a1 : the starting time of data collection in the same measuring section of monitoring point a; t a2 : The time when data collection of the same measuring section of monitoring point a ends.

[0023] The monitoring method described above, the time reference t of the reference point 基 Obtained by the following formula:

[0024] t 基 =t-Δt

[0025] In the above formula, the time base of the monitoring point is t = t1 max +(t2 min -t1 max ) / 2

[0026] Among them, t1 max The latest time when the monitoring points in the same measurement section start collecting data; t2 min The earliest time when the monitoring points in the same measurement section finish collecting data;

[0027] Time Difference

[0028] In the above formula, s is the distance between the reference point and the monitoring point, in meters; v is the water flow velocity measured by the hydrological flow meter, in meters per second.

[0029] The monitoring method of the present invention has the advantages of high precision, high stability and high reliability, can effectively reduce the monitoring cost and can provide a scientific and positive reference basis for construction. [Drawings]

[0030] The present invention will be further described in detail below in conjunction with the accompanying drawings and specific embodiments.

[0031] Figure 1 Schematic diagram of a monitoring system according to an embodiment of the present invention.

[0032] Figure 2 It is a schematic diagram of a counterweight block of a water level detection device according to an embodiment of the present invention.

[0033] Figure 3 It is a schematic diagram of the plan layout of monitoring points according to an embodiment of the present invention.

[0034] Figure 4 It is a schematic diagram of settlement calculation according to an embodiment of the present invention. [Specific implementation method]

[0035] The method for monitoring riverbed settlement during underwater tunnel construction of the present invention is as follows: Figures 1 to 4 As shown, a water level detection device is buried on the riverbed directly above the tunnel as a monitoring point, and a water level detection device is buried on the riverbed outside the construction influence range upstream and / or downstream of the monitoring point as a reference point; the water level detection device includes a water level meter, a hydrological flow meter and a communication module, the water level meter monitors the water level depth of the water level detection device in real time, the hydrological flow meter monitors the water flow velocity in real time, and the communication module reads and transmits water level and hydrological data to the outside at regular intervals; the water level height difference between the monitoring point and the reference point at the same detection time is calculated, and the later water level height difference is compared with the initial water level height difference to obtain the deformation of the monitoring point, and determine whether the monitoring point has subsided or bulged. The specific implementation method is as follows:

[0036] 1. Measurement point arrangement

[0037] Since the pressure-type water level gauge has a small mass, it will be affected by the water flow and cause spatial displacement when it sinks into the water, thus causing distortion of the monitoring data. Therefore, a counterweight device is required to ensure its stable position. The counterweight block is a 20Kg trapezoidal concrete prefabricated part. A 20cm steel bar bracket is reserved at the bottom to be inserted into the mud for fixing. A metal bracket is reserved at the top for tying and fixing the water level gauge. A steel cable is connected at the top for easy point layout and recovery. The structure of the concrete component is as follows: Figure 2 shown.

[0038] The concrete components with water level gauges installed are buried in the riverbed through settlement. Steel bar pull rings are embedded on the concrete components. A total station is set up on the shore. After the position of each measuring point is laid out, it is lowered to the designated position every 30 meters along the tunnel direction by controlling the direction through steel cables. A water level gauge is buried as a reference point outside the influence range of upstream and downstream construction. The plane layout of the monitoring points is as follows: Figure 3 The monitoring point facade layout is as shown in Figure 4 shown.

[0039] 2. Monitoring module integration

[0040] Due to the shielding effect of the river water on the signal, the water level meter cannot transmit the signal from the bottom of the water, and can only be connected to the digital acquisition terminal through the line. It is planned to tie the line and the steel cable together, tie it with a cable tie every 1 meter, and tie a hanging block of about 1kg every 1 meter of the steel cable, sink it to the bottom of the river, and lay it along the riverbed above the tunnel, and finally fix it on the fixed device on the river bank. Each water level meter is equipped with a monitoring all-in-one machine (power supply, data reading, data transmission), which monitors the water level depth of the river bottom water level meter in real time, and calculates the actual elevation of the water level meter by regularly measuring the water level elevation of the river surface, and reflects the sedimentation changes of the river bottom through its elevation changes.

[0041] 3. Data Collection and Results Processing

[0042] After the monitoring points are set up, wait for the natural settlement of the counterweight concrete components to stabilize for 24 hours, all monitoring components are debugged and kept powered on for normal communication, read the water level data every 15 minutes for 48 hours, and remove unreasonable data such as the imbalance of the navigation water level for ships, and take the average water level difference between the monitoring point and the benchmark point as the initial value △h0. The initial values ​​of the water level difference between the monitoring point and the two benchmark points are △h01 and △h02 respectively.

[0043] The digital acquisition terminal reads the water level depth of the water level gauge in real time. The depth is the elevation difference between the water level gauge and the river surface at that time. Assuming that the initial heights of the reference point and the monitoring point and the river surface in the initial state are Hbase0 and h0 respectively, under normal circumstances, the difference between Hbase0 and h0, that is, △h0, should be a constant, and this constant is not affected by the rise and fall of the river surface water level. When a certain monitoring point sinks or rises, this value should change. Assuming that the initial heights of the reference point and the monitoring point and the river surface measured at a certain moment are Hbase1 and h1 respectively, at this time, the height difference △h1 between the two changes. Assuming △h1>△h0, it means that the height difference between the reference point and the monitoring point becomes larger, that is, the monitoring point has sunk, otherwise the monitoring point has risen. At the same time, the deformation h of the monitoring point can be calculated as: h=((△h1-△h01)+(△h2-△h02)) / 2.

[0044] Among them, △h1 is the difference between the later water level height of the monitoring point and the first benchmark point, △h01 is the difference between the initial water level height of the monitoring point and the first benchmark point; △h2 is the difference between the later water level height of the monitoring point and the second benchmark point, △h02 is the difference between the initial water level height of the monitoring point and the second benchmark point.

[0045] The time base between the monitoring point and the reference point is t = (t1 max -t2 min ) / 2 ①

[0046] (In formula 1, t1 max The latest time when the monitoring points in the same measurement section start collecting data; t2 min The earliest time when the monitoring point in the same measurement section ends the collection. The above two values ​​are obtained from the deformation curve diagram with the monitoring time as the horizontal axis X and the water level as the vertical axis Y, which is drawn after internal sorting.

[0047] Time Difference

[0048] (In Formula 2, s is the distance between the reference point and the monitoring point, in meters; v is the water flow velocity measured by the hydrological flow meter, in meters per second)

[0049] 4.1 Solve the time base synchronization problem between monitoring reference points and monitoring points by the following formula:

[0050] Reference point time t 基 =t-Δt ③

[0051] The water level at the reference point after synchronizing the reference point time with the monitoring point time by taking the flow velocity into consideration:

[0052] H 基 =H 基1 +(H 基2 -H 基1 )*(t 基 -t 基1 ) / (t 基2 -t 基1 ) ④

[0053] (In Formula 4, H 基1 : The instantaneous water level value of the benchmark point when the same measuring section starts collecting data; H 基2 : The instantaneous water level value of the reference point when data collection ends in the same measuring section; t 基 : Time base of the reference point; t 基1 : The time when the data collection starts at the benchmark point of the same measuring section; t 基2 : The time when data collection of the benchmark point of the same measuring section ends; the above four values ​​are obtained from the deformation curve diagram with monitoring time as the horizontal axis X and water level as the vertical axis Y drawn after internal sorting).

[0054] 4.2 Solve the time base synchronization problem between monitoring points by the following formula:

[0055] Water level value at monitoring point

[0056] H a =H a1 +(H a2 -H a1 )*(tt a1 ) / (t a2 -t a1 ) ⑤

[0057] (Where H a1 : The instantaneous water level value at monitoring point a when data collection starts in the same measuring section; H a2 : The instantaneous water level value of monitoring point a at the end of data collection in the same measuring section; t a1 : the starting time of data collection in the same measuring section of monitoring point a; t a2 : The end time of data collection in the same measuring section of monitoring point a; the above four values ​​are obtained from the deformation curve diagram drawn after internal collation with monitoring time as the horizontal axis X and water level as the vertical axis Y. )

[0058] 4.3 Solving the problem of refining settlement data under the same time base

[0059] ΔH α =(H α -H 基 )-H a0 ⑥

[0060] (In Formula 6, ΔH a : water level change at monitoring point a, i.e., the settlement at monitoring point a; H a0 : initial water level difference at monitoring point a; H 基 : The water level value of the reference point after synchronizing the reference point time with the monitoring point time by considering the flow velocity; H a : Water level value at monitoring point a)

[0061] 5. Measurement point recovery

[0062] After the monitoring work is completed, the measuring points are manually recovered using small boats and can be reused after simple cleaning and maintenance.

[0063] Example:

[0064] 1. Selection of components: pressure-type water level gauge with temperature compensation function, range: 0~100m, accuracy level: 0.25%, long-term stability: ≤±0.1%FS / year; data acquisition terminal: built-in lithium battery, using IoT card single-point communication transmission, can collect multiple communication modes such as timed communication mode, transparent transmission mode, real-time online collection mode, etc.; hydrological flow meter: range: 0.06~15.00m / s, measurement error ≤1.5%.

[0065] 2. Layout of measuring points: Along the tunnel direction, weighted pressure-type water level gauges are arranged at intervals of 30 meters as monitoring points; weighted pressure-type water level gauges are arranged as reference points at a depth greater than 3 times the tunnel depth upstream of the monitoring points; hydrological flowmeters are arranged between the reference points and the monitoring points.

[0066] 3. Power supply and data transmission: 12V single crystal solar panels are used to power each monitoring component; mobile Internet of Things is used for data transmission, and the minimum sampling transmission interval is 15 minutes.

[0067] Taking a tunnel in Guangzhou that passes under the Pearl River as an example, the detection method of the present invention is described:

[0068] According to the survey results, the water depth of the Pearl River secondary channel in a certain section is about 8 to 12 meters. Taking into account the influence of the channel and the river water, this project only conducts experiments in the shallow water areas near the shore on both sides. A pressure-type water level gauge is buried by settlement at 30m, 60m and 90m above the left-line tunnel on the north and south banks respectively. At the same time, a water level gauge is buried about 30m away from the shore upstream and downstream as a reference point. Each water level gauge is equipped with an all-in-one monitoring machine (power supply, data reading, data transmission). The water level depth of the river bottom water level gauge is monitored in real time, and the actual elevation of the water level gauge is calculated by regularly measuring the river surface water level elevation. The settlement changes of the river bottom are reflected by its elevation changes.

[0069] The frequency of monitoring the water level of the Pearl River is once every 15 minutes. After data synchronization, the settlement values ​​are calculated four times within 1 hour. Finally, the average value is taken after eliminating unreasonable factors such as irregular data when ships pass by according to the four settlement values. Finally, after one month of continuous observation, this method can obtain riverbed settlement data with an accuracy better than 5mm.

[0070] Table 1: Subsidence monitoring of a certain section of the subway under the Pearl River (unit: cm)

[0071]

[0072]

[0073]

[0074]

[0075] Table 2: Examples of monitoring data refinement after time base normalization

[0076] The monitoring method of the method of the above embodiment of the present invention realizes real-time measurement of riverbed settlement, and the highest frequency can reach 1 minute / time. After actual application, the tidal synchronization algorithm can achieve a measurement accuracy better than 5mm, which can meet the riverbed settlement of the engineering tunnel under the water body and can effectively guide the underwater engineering excavation construction.

[0077] The monitoring method for riverbed settlement during underwater tunnel construction of the above embodiment of the present invention has the advantages of high precision, high stability, high reliability, etc. The water level difference between the reference point and the monitoring point is measured by the tidal synchronization algorithm, which effectively controls the variable. It can realize all-weather real-time large-scale automated underwater settlement monitoring, and the measuring points can be recycled and reused, which can effectively reduce the monitoring cost and provide a scientific and positive reference basis for construction.

Claims

1. A method for monitoring riverbed settlement during construction of a tunnel under a river, characterized in that: The following steps are involved: 101) A water level detection device is buried on the riverbed directly above the tunnel as a monitoring point, and at least one water level detection device is buried on the riverbed outside the construction influence range upstream and / or downstream of the monitoring point as a reference point; a plurality of the above-mentioned monitoring points are arranged at set intervals along the tunnel direction, and a water level detection device is buried on the riverbed outside the construction influence range upstream and / or downstream of the monitoring point as a reference point, and a hydrological flow meter is arranged between the reference point and the monitoring point; 102) The water level detection device includes a water level meter and a communication module. The water level meter monitors the water level depth of the water level detection device in real time, and the communication module reads and transmits the water level data to the outside at regular intervals; 103) Calculate the water level difference between the monitoring point and the reference point at the same detection time, compare the later water level difference with the initial water level difference to obtain the deformation of the monitoring point, and judge whether the monitoring point has settled or uplifted; The cumulative settlement of a monitoring point a is obtained by the following formula: in, : The water level change at monitoring point a, i.e., the settlement at monitoring point a; : Initial water level difference at monitoring point a; : The water level value of the reference point after synchronizing the reference point time with the monitoring point time by considering the flow velocity; : Water level value at monitoring point a.

2. The monitoring method according to claim 1, characterized in that: The water level detection device includes a prefabricated concrete part as a counterweight block. The bottom of the prefabricated concrete part includes a plurality of steel bars extending downward, which serve as a metal bracket inserted into the riverbed to fix the water level detection device. The top of the prefabricated concrete part includes a metal bracket for binding and fixing a water level gauge. The metal bracket is connected to a steel cable for point-to-point deployment and recovery of the water level detection device.

3. The monitoring method according to claim 1, characterized in that: The communication module of the water level detection device is connected to the corresponding data acquisition terminal on the shore through a communication cable. The data acquisition terminal is wirelessly connected to the control center to send data to the control center. The communication cable is tied together with the steel cable, tied with a cable tie at set intervals, and tied with heavy blocks and sunk to the bottom of the water.

4. The monitoring method according to claim 1, characterized in that: A water level detection device is buried on the riverbed upstream and downstream of the monitoring point as a reference point; the deformation h of the monitoring point is: h=((△h1-△h01)+(△h2-△h02)) / 2; among them, △h1 is the later water level difference between the monitoring point and the first reference point, △h01 is the initial water level difference between the monitoring point and the first reference point; △h2 is the later water level difference between the monitoring point and the second reference point, △h02 is the initial water level difference between the monitoring point and the second reference point.

5. The monitoring method according to claim 1, characterized in that: The water level value of the benchmark point after the benchmark point time is synchronized with the monitoring point time Obtained by the following formula: in, : The instantaneous water level value of the benchmark point when the same measuring section starts collecting data; : The instantaneous water level value of the benchmark point when data collection ends in the same measuring section; : The time base of the benchmark point; : The time when data collection starts at the benchmark point of the same measuring section; : The time when data collection for the benchmark point in the same measuring section ends.

6. The monitoring method according to claim 1, characterized in that: Water level value at monitoring point a It is obtained by the following formula: in : The instantaneous water level value of monitoring point a at the beginning of data collection in the same measuring section; : The instantaneous water level value of monitoring point a at the end of data collection in the same measuring section; : The starting time of data collection in the same measuring section of monitoring point a; : The end time of data collection in the same measurement section of monitoring point a; In the above formula, the time reference of the monitoring point :in, is the latest time when the monitoring points in the same measurement section start collecting data. It is the earliest time when the monitoring points in the same measurement section finish collecting data.

7. The monitoring method according to claim 1, characterized in that: Time base of the benchmark It is obtained by the following formula: In the above formula, the time base of the monitoring point is in, The latest time when data collection starts at the monitoring points in the same measurement section; The earliest time when the monitoring points in the same measurement section finish collecting data; In the above formula, s is the distance between the reference point and the monitoring point, in meters; v is the water flow velocity measured by the hydrological flow meter, in meters per second.

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