A mass concrete temperature monitoring method based on DTS temperature measurement technology

Abstract

A mass concrete temperature monitoring method based on DTS temperature measurement technology, comprising: a) uniformly arranging horizontal optical fibers in a radial manner in the horizontal direction with the foundation pit center as the center, and arranging vertical optical fibers in an S shape along the raft thickness direction; b) coupling the horizontal optical fibers and the vertical optical fibers with the steel bar mesh; c) connecting the horizontal optical fibers and the vertical optical fibers with an optical fiber demodulator to form a distributed optical fiber temperature measurement system; d) after the pouring of the raft foundation is completed, analyzing the temperature change measured by the optical fiber demodulator, and stopping the monitoring when the temperature change tends to be stable. By arranging horizontal and vertical optical fibers in the raft foundation, the temperature change of the mass concrete is collected by the distributed optical fiber demodulator, and the data is analyzed to obtain the concrete temperature field, so that the temperature change of the concrete during the pouring process can be monitored in real time and accurately, the temperature control of the concrete can be accurately and effectively guided, the need for large-scale temperature monitoring can be met, the measurement accuracy is improved, the monitoring cost is low, the anti-interference ability is strong, and the stability is better.

Description

TECHNICAL FIELD

[0001] The present application relates to a mass concrete temperature monitoring method based on DTS temperature measurement technology. The monitoring method can meet the requirements of DTS temperature measurement technology for monitoring the temperature change of mass concrete, and can form a concrete temperature field to accurately guide the concrete temperature control. The monitoring accuracy of the monitoring method is significantly improved compared with the traditional monitoring method, and the monitoring cost is reduced. BACKGROUND

[0002] With the large-scale construction of high-rise buildings, mass concrete is widely used as the foundation part of the building. During the pouring and curing of mass concrete, due to the poor thermal conductivity of concrete and the hydration reaction of cement releasing a large amount of heat, it is easy to cause a large temperature difference inside the concrete structure, forming a large temperature stress. The early concrete has low tensile strength, and the temperature stress forces the material to produce temperature cracks, thereby affecting the strength of the material and the durability of the structure. Necessary temperature monitoring of mass concrete and mastering the change of temperature gradient are the premise of effectively implementing cooling measures and the guarantee of controlling the construction quality of mass concrete.

[0003] Traditional concrete temperature field monitoring mostly uses point thermometers. However, the use of traditional point thermometers for concrete temperature field monitoring has the following disadvantages: 1) only a single point temperature can be measured, installation is complex, and anti-interference ability is poor; 2) monitoring information is managed by manual, dispersed storage, and information analysis needs to go through a complex process of data collection, upward reporting, expert discussion, and downward transmission, the analysis cycle is long, and it is difficult to play the role of the monitoring system; 3) the temperature meter has limited point distribution, and the information amount is too small, it is difficult to master the temperature field change and distribution rule of the entire concrete structure, and thus it is not suitable for mass concrete temperature measurement.

[0004] In recent years, a distributed optical fiber temperature measurement technology has appeared in this technical field, which has obvious advantages compared with the traditional thermocouple temperature measurement technology: high temperature measurement accuracy, wide monitoring range, real-time online monitoring, automatic data collection, and convenient and fast mastering of the temperature field change of the entire concrete structure. With the rapid development of distributed optical fiber temperature measurement technology, it has become a very effective means for monitoring the internal temperature of mass concrete. However, this temperature measurement technology not only has high cost of optical fiber monitoring, but also has great construction difficulty. Therefore, a very effective technology and method are needed to make up for the shortcomings of the existing technology. SUMMARY

[0005] In order to overcome the above-mentioned deficiencies of the prior art, the application provides a mass concrete temperature monitoring method based on DTS temperature measurement technology, which utilizes a distributed optical fiber temperature measurement system to monitor the mass concrete temperature field in real time, and has high monitoring precision and low monitoring cost.

[0006] The mass concrete temperature monitoring method based on DTS temperature measurement technology of the application, on one hand, determines the optical fiber type by comparison test, and adopts temperature compensation optical fiber, which has the highest temperature measurement precision and the highest optical fiber survival rate; on the other hand, adopts a transverse radiation type and vertical S-shaped optical fiber arrangement mode (i.e. a distributed optical fiber arrangement mode) to monitor temperature change.

[0007] The technical scheme of the mass concrete temperature monitoring method based on DTS temperature measurement technology of the application is specifically introduced as follows.

[0008] Firstly, the scientific principle on which the technical scheme of the application is based, i.e. DTS temperature measurement technology, is introduced.

[0009] The distributed optical fiber temperature measurement system (also referred to as DTS system) is usually composed of a laser light source, a sensing optical fiber (cable) and a detection unit, and is an automatic monitoring system. The measurement is realized by utilizing the principle that light transmission in the optical fiber can produce backscattering, i.e. a laser pulse with certain energy and width is injected into the optical fiber, and backscattering light waves are constantly generated during the transmission of the laser pulse in the optical fiber, the state of the light waves is changed by the temperature of the scattering point in the optical fiber, the backscattered light waves are sent into a signal processing system after wavelength division multiplexing, detection and demodulation, and the temperature signal can be displayed in real time, and the information can be located according to the transmission speed of the light waves in the optical fiber and the time of the back light echo.

[0010] The main feature of the distributed sensing type optical fiber temperature measurement system is that the optical fiber itself is used as a sensitive element by utilizing the characteristics of the optical fiber, and the temperature measurement optical fiber not only plays a light transmission role, but also plays a sensing role. Therefore, the distributed sensing type optical fiber temperature measurement system is also referred to as an intrinsic distributed optical fiber monitoring system or a full-distributed optical fiber monitoring system, and is simply referred to as a distributed optical fiber temperature measurement system.

[0011] The reflected light reflected back to the incident end mainly includes Rayleigh scattering light and Raman scattering light. Since the Rayleigh scattering is less affected by temperature change, it can be ignored. The Raman scattering includes Stokes scattering and Anti-Stokes scattering, in the Stokes scattering, the Stokes light is irrelevant to temperature change, but in the Anti-Stokes scattering, the Anti-Stokes light changes with temperature change.

[0012] DTS is based on Raman Optical Time-Domain Reflectometer (ROTDR), when the pulse light emitted by laser light source (laser) has non-elastic collision in the transmission of optical fiber, Raman scattering occurs, generating two different frequency shift components, one component is Anti-Stokes light with frequency greater than the incident light, which is sensitive to temperature, and the other component is Stokes light with frequency less than the incident light, which is not sensitive to temperature, the light intensity, frequency shift and temperature of the two components satisfy the following relationship:

[0013]

[0014] In the formula, R(T) is a temperature function; I f , v f are Anti-Stokes light intensity and frequency respectively; I s , v s are Stokes light intensity and frequency respectively; c is the propagation speed in vacuum; v is the Raman frequency shift; h is the Planck constant; K is the Boltzmann constant; T is the absolute temperature.

[0015] The distance between the incident end of pulse light and the temperature abnormal point satisfies the following relationship:

[0016]

[0017] In the formula, L is the distance from the incident end of pulse light to the temperature abnormal point; t is the interval time from emitting pulse light to receiving scattered light; n is the refractive index of optical fiber.

[0018] Based on the relationship (1), the temperature demodulator obtains the temperature information R(T) of the abnormal point according to the light intensity ratio I f / I s of the two frequency shift components, and then based on the relationship (2), obtains the position information L of the abnormal point according to the interval time t of optical signal.

[0019] Then, the specific steps of the monitoring method involved in the technical scheme of the application are introduced.

[0020] A mass concrete temperature monitoring method based on DTS temperature measurement technology, sequentially comprising the following steps:

[0021] a. uniformly arranging 8 horizontal optical fibers in a radial manner along the horizontal direction outward from the center of the foundation pit, and thus arranging multiple layers at such intervals; meanwhile, arranging vertical optical fibers in an S shape along the thickness direction of the raft on 4 horizontal optical fibers;

[0022] b. The horizontal optical fiber and the vertical optical fiber (collectively referred to as "temperature measuring optical fiber" or "temperature monitoring optical fiber") are respectively bound with the PVC pipe by nylon straps, the PVC pipe is connected by pipe clamp, and is sent into the bound steel mesh in sections; the PVC pipe is connected and coupled with the steel mesh by nylon straps;

[0023] c. The horizontal optical fiber and the vertical optical fiber are connected with the peripheral optical fiber demodulator by the transmission optical cable, and thus a distributed optical fiber temperature measuring system is formed;

[0024] d. After the raft foundation is poured, the temperature change of the concrete measured by the optical fiber is analyzed by the optical fiber demodulator, and the monitoring is stopped when the temperature change tends to be stable, and finally the concrete temperature field of the raft foundation is formed.

[0025] Further, the horizontal optical fiber and the vertical optical fiber both adopt temperature compensation optical fiber.

[0026] Further, the temperature compensation optical fiber comprises, from inside to outside, a fiber core, an optical fiber cladding layer, an optical fiber coating layer and an optical fiber sheath layer.

[0027] Further, the optical fiber demodulator is a cabinet type distributed optical fiber temperature demodulator.

[0028] The mass concrete temperature monitoring method based on the DTS temperature measuring technology can monitor the temperature change of the mass concrete structure in the whole process from pouring to solidification of the raft foundation by the distributed optical fiber in real time and accurately, can meet the requirement of large-scale monitoring, can greatly improve the measurement precision, can save the cost to the maximum, and has strong anti-interference ability and better stability. BRIEF DESCRIPTION OF DRAWINGS

[0029] Figure 1 It is a schematic view of the temperature measuring optical fiber arranged along the horizontal direction in the mass concrete temperature monitoring method based on the DTS temperature measuring technology.

[0030] Figure 2 It is a schematic view of the temperature measuring optical fiber arranged along the thickness direction of the raft in the mass concrete temperature monitoring method based on the DTS temperature measuring technology.

[0031] Figure 3 It is a schematic view of the distributed optical fiber temperature measuring system.

[0032] Figure 4 It is a structural schematic view of the temperature compensation optical fiber.

[0033] Figure 5 It is a sectional view of the temperature compensation optical fiber.

[0034] In the figure: 1-temperature compensation optical fiber; 2-optical fiber sheath layer; 3-optical fiber coating layer; 4-optical fiber cladding layer; 5-fiber core. DETAILED DESCRIPTION

[0035] The specific embodiments of the present application will be further described and explained in detail in conjunction with the accompanying drawings.

[0036] The mass concrete temperature monitoring method based on the DTS temperature measurement technology of the present application comprises the following steps in sequence:

[0037] a. Eight horizontal optical fibers are uniformly arranged in a radial manner outward along the horizontal direction with the center of the foundation pit as the center, as shown in FIG. 1, and multiple layers are arranged at such intervals, as shown in FIG. 2, for example, three layers, as shown in FIG. 3, to monitor the temperature change of the concrete along the horizontal direction. At the same time, vertical optical fibers are arranged in an S-shaped manner along the thickness direction of the raft, as shown in FIG. 4, on the arranged horizontal optical fibers to monitor the temperature change of the concrete along the thickness direction of the raft. Figure 1 Figure 3 Figures 2-3

[0038] b. The horizontal optical fibers and the vertical optical fibers (collectively referred to as "temperature measurement optical fibers" or "temperature monitoring optical fibers") are respectively bound with PVC pipes by nylon straps, the PVC pipes are connected by pipe clamps, and are sent into the steel mesh in sections after being bound. Then, the PVC pipes are connected and coupled together with the steel mesh by nylon straps, and the tightness is determined by the distance between the two fixed points, so that the tightness of all optical fibers is consistent, and the monitoring error is reduced.

[0039] c. The horizontal optical fibers and the vertical optical fibers are connected with the peripheral optical fiber demodulator by a transmission optical cable, as shown in FIG. 5, thus forming the distributed optical fiber temperature measurement system of the present application. Figure 3

[0040] d. The strain image monitored by the temperature measurement optical fibers is obtained by the optical fiber demodulator. After the pouring of the raft foundation is completed (i.e., after the pouring of the mass concrete), the above-mentioned monitored temperature change of the concrete is analyzed by the optical fiber demodulator, and the monitoring is stopped when the temperature change tends to be stable, and finally an accurate and efficient temperature field of the raft foundation (i.e., a concrete temperature monitoring field) is formed.

[0041] The above steps a-c can be collectively referred to as the "optical fiber arrangement" step.

[0042] Selection of optical fibers: Preferably, the horizontal optical fibers and the vertical optical fibers (which can be collectively referred to as temperature measurement optical fibers or temperature monitoring optical fibers) of the present application all adopt temperature compensation optical fibers.

[0043] Figure 4 The structure of the temperature compensation optical fiber in the present application is shown in FIG. 6, Figure 5 ​​​​It is a sectional view of the temperature-compensated optical fiber in the present application. Figures 4-5 The temperature-compensated optical fiber in the present application comprises, from inside to outside, a fiber core 5, an optical fiber cladding 4, an optical fiber coating layer 3 and an optical fiber sheath layer 2.

[0044] Selection of the optical fiber demodulator: the optical fiber demodulator in the present application is a distributed optical fiber demodulator, preferably a cabinet-type distributed optical fiber temperature demodulator.

[0045] In the present application, a plurality of optical fiber measuring points are arranged at intervals in each temperature-compensated optical fiber, and the interval between adjacent optical fiber measuring points is preferably 15 m.

[0046] In the present application, the monitored optical fiber temperature change is analyzed by the optical fiber demodulator, so that the temperature curve of each channel at each moment and the temperature curve of any point on the optical fiber changing with time can be seen on the DTS demodulator.

[0047] In summary, the mass concrete temperature monitoring method based on the DTS temperature measurement technology in the present application adopts a horizontal radiation and vertical S-shaped arrangement mode to arrange the temperature measuring optical fiber, and the temperature measuring optical fiber is selected from temperature-compensated optical fiber, and the optical fiber demodulator is selected from a cabinet-type distributed optical fiber temperature demodulator. Therefore, according to the present application, the distributed optical fiber can monitor the temperature change in the mass concrete structure in the whole process from pouring concrete to solidification of the raft foundation in real time and accurately, which can meet the requirement of large-scale monitoring, greatly improve the monitoring precision, save the cost to the maximum, reduce the cost to the minimum, and has strong anti-interference ability and better stability. It can be seen that the present application can meet the requirement of the ability of the distributed optical fiber sensing technology to accurately monitor the temperature change and the ability to form a temperature field.

Claims

1. A method for monitoring the temperature of large-volume concrete based on DTS temperature measurement technology, comprising the following steps: a. Eight horizontal optical fibers are evenly arranged radially outward from the centroid of the foundation pit, and multiple layers are arranged at intervals in this manner to monitor the temperature change of the concrete along the horizontal direction; at the same time, vertical optical fibers are arranged in an S-shape along the thickness direction of the raft slab on the horizontal optical fibers to monitor the temperature change of the concrete along the thickness direction of the raft slab; the horizontal and vertical optical fibers are collectively referred to as temperature measuring optical fibers. b. Tie the horizontal and vertical optical fibers to the PVC pipes with nylon cable ties, connect the PVC pipes with pipe clamps, and feed them into the tied steel mesh section by section. Then, use nylon strips to connect and couple the PVC pipe to the steel mesh. c. Connect the horizontal and vertical optical fibers to the external optical fiber demodulator using transmission optical cables, thus forming a distributed optical fiber temperature measurement system; d. The strain image monitored by the temperature-measuring optical fiber is obtained by the optical fiber demodulator. After the raft foundation is poured, the concrete temperature change measured by the optical fiber is analyzed by the optical fiber demodulator. When the temperature change tends to stabilize, the monitoring is stopped, and finally the concrete temperature field of the raft foundation is formed. Moreover, numerous fiber optic measuring points are spaced apart in each temperature measuring fiber, with a spacing of 15m between adjacent fiber optic measuring points.

2. The method for monitoring the temperature of large-volume concrete based on DTS temperature measurement technology according to claim 1, characterized in that: Both the horizontal and vertical optical fibers are temperature-compensated fibers.

3. The method for monitoring the temperature of large-volume concrete based on DTS temperature measurement technology according to claim 2, characterized in that: The temperature-compensated optical fiber (1) includes, from the inside out, a fiber core (5), an optical fiber cladding (4), an optical fiber coating layer (3), and an optical fiber sheath layer (2).

4. The method for monitoring the temperature of large-volume concrete based on DTS temperature measurement technology according to any one of claims 1-3, characterized in that: The fiber optic demodulator is a cabinet-type distributed fiber optic temperature demodulator.

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